射頻期中整理.pptx

AM = Amplitude modulation 調幅,資料載在振幅上
FM = Frequency modulation 調頻,資料載在頻率上
ASK = amplitude shift keying 振福位移鍵送,電磁波振幅小代表0，振幅大代表1
PSK = phase shift keying 相位位移鍵送,電磁波相位0°（先上後下振動）代表0，相位180°（先下後上振動）代表1
FSK = frequency shift keying 頻率位移鍵送,電磁波頻率低代表0，頻率高代表1
ISI problem = Intersymbol interference problem 符號間干擾問題
RRC filter = root raised cosine filter 根餘弦濾波器
CPFSK = Continuous Phase Frequency Shift Keying 連續相位頻移鍵控
DPSK = Differential PSK 差分相位調變-移相180o
QPSK = Quadrature Phase Shift Keying 4階相位偏移調變-移相90o
OQPSK = offset QPSK 偏移QPSK-移相90o
p/4 QPSK =移相135o
MSK = Minimum Shift Keying最小頻移鍵控
PDF = Probability Density Function 概率密度函数
PSD = Power Spectral Density 功率譜密度
FIR = finite impulse response有限脈衝響應濾波器
ARQ = Automatic repeat request systems自動重複請求系統
TDD = Time division duplex 時分雙工
FDD = Frequency division duplex 頻分雙工
TDM = Time division multiplexing 分時多工
FDM = Frequency division multiplexing 正交頻分多工
WDM = Wavelength division multiplexing 波長分波多工

TDMA = Time Division multiple Access 分時多工
FDMA = Frequency Division Multiple Access 分頻多重進接
CDMA = Code Division Multiple Access 分碼多重進接
ODMA = Orthogonal frequency-division multiplexing 正交分頻多工
AMPS = Advanced Mobile Phone System 類比式行動電話系統
NADC = North American Digital System
GSM = Global System for Mobile Communication 全球行動通訊系統
DECT = Digital European Cordless Telephone 數位增強無線通訊

2: Modulation and demodulation Slide 3
Amplitude Modulation
• Amplitude modulation

Amplitude Modulation
• AM
• Sensitive to additive noise.
• Requires linear PA
( ) [1 ( )]cos
AM BB c
x t Ac mx t t

 
缺點
對雜訊敏感
需要線性PA

AM Detector
• Coherent demodulation or Envelop detector
• The envelop of the modulated waveform does not cross zero
( ) 1 ( )
AM BB
x t mx t
 
AM 接收機
Coherent 同調

FM Modulator
• VCO can be a FM modulator
• phase is an integral form of frequency
• VCO frequency is determined by value of the Inductor, which is
modulated by XBB(t).
( ) cos ( )
FM c c BB
x t A t m x t dt

 
 
 

FM 發射機
二極體就是一個可變
電容(在逆向導通區)

Simple FM Demodulator
• Simple FM Demodulator :
• Differentiator
• High pass filter
 
   
1 1
( ) [ ( )]sin[ ( ) ]
out c c BB c BB
v t A R C mx t t m x t dt
FM 解調
微分器
高通濾波器

Narrow Bandwidth FM (1)
• If << 1 rad
( ) cos ( )
FM c c BB
x t A t m x t dt

 
 
 

, ( ) cos (sin ) ( )
FM NB c c c c BB
x t A t A m t x t dt
 
  
 ( )
BB
m x t dt
微分-高通
積分-低通

Narrow Bandwidth FM (2)
• Single tone test , if 

( ) cos
BB m m
x t A t
( ) cos ( )
FM c c BB
x t A t m x t dt

 
 
 


Narrow Bandwidth FM
• NBFM Spectrum

FM spectrum
• Bessel Function
( ) cos
BB m m
x t A t


( ) cos[ ( / )sin ]
FM C C m m m
x t A t mA t
  
 
( ) ( )cos( )
FM C n C m
n
x t A J n t
  


 

m
m
mA



0 1
If << 1 rad
( ) 1
, ( ) Narrow Band FM
2
( ) 0 for 1
n
J J
J n


 





   



  

Carson’s rule
• Carson’s rule : If the bandwidth of FM ( ) is defined as containing
98% signal power, the following formula is derived
2( 1)
FM BB
BW BW

 
FM
BW

Digital Modulations
• ASK, PSK, FSK
PSK---技術最複雜，抗雜訊能力最好，因此較常用在無線通訊
ASK---技術最簡單，抗雜訊能力最差，較少使用在無線通訊，而是使用在光纖通訊
FSK---技術複雜，但抗雜訊能力比ASK 好，錯誤率低，可使用在無線通訊

Digital Modulations
n
n
cos , if b 1
( )
0 ,if b 0
c
ASK
A t
x t
 

 


1 n
n
cos , if b 1
( )
cos 2 ,if b 0
FSK
A t
x t
A t




 


1 n
1 n
cos , if b 1
( )
cos ,if b 0
PSK
A t
x t
A t




 
 


ASK
• The simplest form of bandpass data modulation is Amplitude Shift Keying (ASK).
• In binary ASK, where only two symbol states are needed, the carrier is simply turned on or off.
• ASK is sometimes referred to as ON-OFF Keying (OOK).

ASK data spectrum
• This ASK spectrum is a double sideband spectrum
• It has an upper and lower sideband with respect to the carrier.
• If we now include all the components in the baseband stream which will mix with the carrier to generate a frequency
sum(+) and difference(-) component,
then 1. resulting spectrum is symmetrical about the carrier frequency
then 2. spectrum is with a positive and reversed image of the baseband 'sinc' spectrum for an unfiltered binary data
stream.
Data stream in

Factors affecting signal bandwidth
• Reducing the width of the pulse but keeping the period of the
waveform constant results in
• the lower harmonic levels
• an increase in the level of the higher harmonics

Smooth transition
• Because the sharp changes in waveform
can only be constructed from a large
number of low-level high frequency
sinusoids in a Fourier series expansion.
• So a waveform which has sharp
transitions in the time domain will have a
higher harmonic content than smooth
transitions.
• Hence, modulation that possess smooth
pulse shapes between symbol states are
to be favored when bandwidth is limited.
Nyquist filter

Nyquist filters
• A commonly used pulse-shaping method is to pass the data stream
through a low pass filter having a raised cosine response.
• The raised cosine filter belongs to a family of filters called Nyquist
filters .
• It also reduces ISI problem.

Bandpass filtering method
• In order to minimize the occupied bandwidth of the transmitted ASK signal, filtering or pulse
shaping is required either prior to or after modulation onto a carrier.
• The switching method of ASK generation does not allow any pre-filtering of the modulating
baseband symbol stream, as the switch is a non-linear process
Switch沒有辦法濾波

Non-coherent detection
• ∵With ASK, the information is conveyed in the amplitude or
envelope of the modulated carrier signal.
∴ the data can thus be recovered using an envelope detector.
• An simplest envelope detector comprises a diode rectifier and smoothing filter
• non-coherent detector.
ASK解調
RFID會用到ASK
整流+濾波+比較器

Non-coherent detection
• If quadrature versions of the modulated carrier signal are available in the receiver, that is,a(t) cos wct and
a(t) sin wct (where a(t) represents the data imposed amplitude modulation).
• Mathematically we get:
a(t)2 cos2wct + a(t)2 sin2wct
= a(t)2 (cos2wct + sin2wct) = a(t)2
沒有乘法器
抗雜訊較差一點

ASK Coherent detection
• Representing the modulated data signal as a(t) cos wct and the reference carrier as cos(wct + q) ,
the mixer output becomes:
a(t) cos wct cos(wct + q)
= 0.5 a(t)cos(q) + 0.5 a(t)cos(2wct + q)
• If the carrier is phase coherent with the incoming modulated carrier signal (that is, there is no
frequency or phase difference between them, q = 0o), then
the output is proportional to a(t) and perfect detection is achieved.
Coherent
載波是什麼就成一
個一樣的訊號(SNR
較好)
缺點
會有一個相位差!

Coherent Matched filter
• Matched filtering of baseband data signals is for
optimizing the signal to noise ratio at the output of
a data receiver.
• Matched filtering is applicable to bandpass
modulation detection.
• A matched filter pair such as the root raised
cosine(RRC filter) filters can thus be used to
• shape the source and
• received baseband data
symbols in ASK,
有最佳的SNR
可限制BW 可積分

Carrier recovery for ASK
• It is beneficial to use coherent detection of ASK
• means of recovering the carrier frequency and phase from the
incoming data signal is needed.
• A technique that is well suited to this task is the phase-locked loop
(PLL)
• Issues:
• input referred noise
• Off state

Coherent detection vs
non-coherent detection
• Let us now consider the case of detecting the ASK signal in the presence of noise. For simplicity
we will assume that the carrier is in the 'off' state and that we have a specific noise component of
length N and phase 60 degree
• The non-coherent detector,
• which is performing amplitude detection, is simply measuring the length of the composite
(ASK + Noise) vector regardless of the vector phase. It would thus produce an output voltage
proportional to N, the noise vector length.
• The coherent detector,
• acts by mixing the incoming signal with the reference carrier cos wt. The result is that the
voltage at the detector output due to the noise is reduced by a factor cos(60o) = 0.5 and is
thus proportional to N/2.

Coherent detection vs
non-coherent detection
• On average, the coherent detection method reduces the noise voltage
out of the detector by a factor of root 2 and the noise power by 2.
• In other words, coherent detection of ASK can tolerate 3 dB more
noise than non-coherent ASK for the same likelihood of detection
error.

BER performance of ASK
• The Eb/N0 value is for the average symbol power which is 3 dB less than the peak symbol power for ASK (the
carrier is off for approximately half of the transmitted symbols).
SNR的倍率
(類比)
錯
誤
率
(
數
位
)
類比數位溝通
的圖示

FSK generation
• FSK can be generated by switching between distinct frequency
sources.
• Any phase discontinuity at the symbol boundary will result in a much
greater prominence of high frequency terms in the spectrum
2個不同頻率的訊
號做切換開關
不連續的地方有高
頻協波項

FSK generation
• FSK can be realized by applying the data signal to a voltage controlled
oscillator (VCO) .
• The phase transition between consecutive symbol states is
guaranteed to be smooth (continuous).
• FSK with no phase discontinuity between symbols is known as a
Continuous Phase Frequency Shift Keying (CPFSK) format.

Vector modulator
• Vector modulator or quadrature (正交)
modulator
• To generate FSK requires the
generation of two symbols, one at a
frequency (c + 1) and one at a
frequency (c – 1).
• In order to generate a frequency shift
of + 1 at the output of the vector
modulator, the I and Q inputs need to
be fed with
+/-cos 1 and sin 1, respectively.
sin（α＋β）＝sinαcosβ＋cosαsinβ
sin（α－β）＝sinαcosβ－cosαsinβ

Spectrum of FSK
• The spectrum of the FSK signal is not as easy to derive as that for ASK
because the FSK generation process is non-linear.
• An approximation can be obtained by plotting the spectra for two ASK
streams centered on the respective carrier frequencies

PLL-based FSK detection
• VCO control voltage must change in order for the PLL to track and lock
onto a new input frequency.
• It provides a direct measure of the input signal frequency for each
symbol in the FSK stream.
應用在低速
的應用

BER

Comparison
• Advantages of FSK
• FSK is a constant envelope modulation, and hence insensitive to amplitude (gain) variations
in the channel
• Compatible with non-linear transmitter and receiver systems.
• The detection of FSK can be based on relative frequency changes between symbol states and
thus does not require absolute frequency accuracy in the channel.
• (FSK is thus relatively tolerant to local oscillator drift and Doppler shift.)
• Disadvantages of FSK
• FSK is slightly less bandwidth efficient than ASK or PSK (excluding MSK implementation).
• The bit/symbol error rate performance of FSK is worse than for PSK under the same SNR.

PSK generation
• The simplest means of realizing unfiltered binary PSK is to switch the
sign of the carrier using the data signal, causing a 0 or 180 degree
phase shift.
• Just as for ASK, this method of generation is not well suited to
obtaining a Nyquist filtered waveform.
• Owing to the difficulty in implementing bandpass high frequency, high Q
filters.

PSK generation
• If filtering is required, then linear multiplication must be employed.
• The data stream to be pre-shaped at baseband prior to the
modulation process.

PSK Detection
• There is no non-coherent equivalent detection process for PSK,
• We need zero phase error for optimum detection and must re-visit the whole area of carrier
recovery.
• Note that if the phase error reaches 90 the output falls to zero!

The Costas loop
   
1
sin cos sin sin
2
     
 
   
 
   
1
cos sin sin sin
2
     
 
   
 
   
1
cos cos cos cos
2
     
 
   
 
   
1
sin sin cos cos
2
     
 
    
 
9

The Costas loop
• If qi-qo > 0 , then input of VCO will increase to trace qi.
• Otherwise, it will operate inversely.
• Behave like a phase lock loop.
• LPF is used to enhance the stability of close loop.
Sin(qi-qo)
Vcoin
Enhance close loop
stability
9

Differential data coding
• FSK is possible to determine the frequency corresponding to each bit.
• However, the phase of PSK relates to the time origin and has no
“absolute” meaning.
• Both Costas loop and squaring circuit suffer from phase ambiguity.
• Training sequence in the head of packet is a possible solution.
• Differential data coding : If the information lies in the phase change
from one bit to the next , then a time origin is not required.
改善PSK資料任取一段看不出相位的問題

Differential data encoding
• Differentially Encoded.
• If the present input bit is a ONE, then the output state of encoder
does not change

Differential data decoding
• If the now state is the same as the previous stat of input, then
decoder outputs ONE.
• What if the encoded Data are inverted?
• Or the first bit is ambiguous?
數位的作法

Differential PSK (DPSK)
• Differential PSK (DPSK) is based on the same differential encoding technique as used in DEPSK.
• Mixer or Multiplier behaves like a XNOR
 
 

 
1 1
1 1
if cos( ) cos( ),after filtering it output 1
if cos( ) cos( ),after filtering it output -1
t t
t t
類比的做法
是一種非同調的相位調變系統 (noncoherent PSK)。對於同調解調相位調變系統，資料位元{ bk }會直接接影響傳送載波的相位進行調變。
DPSK則是以目前位元dk的載波相位與前一位元dk-1的載波相位差(0或π)作為傳送的資訊的調變，DPSK的編碼方式為:
=1
0
k k
k k
b d change
if
b d unchange
if 
也就是dk=bk⊕dk-1。傳送端只要偵測相臨兩位元(dk、dk-1)的載波相位差即可以還原出資料位元bk。

Differential PSK (DPSK)
• It improves upon it by incorporating the differential decoding task as part of the data
demodulation task.
• It does away with the need for a 'carrier recovery' mechanism .它消除了“載波恢復”機制的需
要。
• It rolls ‘coherent detection’ and ‘differential decoding’ into one operation.它將“一致性檢測”
和“差分解碼”合併為一個操作
• Clearly, this detection process is much simpler than that required for true coherent PSK.
• DPSK is widely used in wired and radio modems for medium-rate signalling (up to 4800 bps).
• DPSK, however, has a slightly poorer noise immunity than PSK since the phase reference for DPSK
is now a noisy delayed version of the input signal rather than potentially a well-filtered, virtually
noiseless reference from a carrier recovery process.

Probability Density Function
• The PDF is defined as : Px(x)dx=probability that the amplitude is
between x and x+dx.
• Note that PDF does not tell us how fast the waveform varies, that
means no frequency relativity.

Gaussian distribution
• Central Limit Theorem : If many independent random process with
arbitrary PDFs are added, the PDF of the sum approaches a Gaussian
distribution
• Gaussian PDF:
where and m are the standard deviation and the
mean,respectively.
• Remember that 68% for the sampled values fall between m- and
m+ and 99% between m-3 and m+3
2
2
1 ( )
( ) exp
2
2
x
x m
p x

 p
 



  
m平均值
變異量


Power Spectral Density
• The PSD, Sn(f), of a random signal x(t) indicates how much power the
signal carries in a small bandwidth around frequency f.

PDF and PSD
• PDF is statistical indication of how often the amplitude of a random
process falls in a given range of values.
• PSD shows how much power the signal is expected to contain in a
small frequency interval.
• In general, the PDF and PSD bear no relationship.
• Thermal noise has a Gaussian PDF and white PSD.
• Flicker noise the same type of PDF but a PSD proportional to 1/f.
越低頻雜訊越高

PDF of Binary Modulation

BER calculation
• It demonstrates that BER is only concerned with
SNR
• To gain a max SNR , E must be maximized too.
 
 
2
2 1
2 1
2
0
( ) ( )
2 2
2
e
n n
A A
A A E
p Q Q Q
N
 
 

  
  
 
 
2
2 1
2
0
( )
where,
/ 2
n
A A E
SNR
N


 

Coherent BPSK


 

2
1 2
according to [ ( ) ( )]
Ed p t p t dt




2
0
2
(2 cos )
2
b
T
C c
c b
A t dt
A T
 
 

 
 
2
0
Hence c b
e
A T
P Q
N

 

2
2
b 0
E ( cos )
2
b
T
c b
C
A T
A t dt
 
  
 
 
0
2
Hence b
e
E
P Q
N
Large Ac&Tb cause low Pe

Coherent FSK
• For a given probability of error and noise density, the bit energy in
BFSK must be twice that in BPSK.
• The minimum distance between the points in the constellation is
greater in BPSK.
• Recall that SNRmax=2Ed/N0, the value of Ed reach its maximum if
p1(t)=-p2(t), which is the case for BPSK.
• BPSK has a 3-dB advantage over BFSK
• However, BFSK is widely used in low data rate application where Eb
can be maximized by allowing a long Tb.
週期長一點,SNR變好,速度變慢

Quadrature Modulation
• It is often beneficial to subdivide a binary data stream into pairs of
two bits and perform the Quadrature modulation:
PSK同時使用cos和sin的訊號

Quadrature Modulation
• Quadrature modulation encompasses two broad categories:
• Quadrature Phase Shift Keying (QPSK),
• Minimum Shift Keying (MSK)
QPSK

QPSK 解調

Phase transition
• Large phase (maximum 180 degrees) changes occurs at the end of
each symbol.
• Large phase transition causes large envelope variation.(180 degree
cross zero is worst).
• Such transition needs a linear power amplifier
相位角會差180
產生劇烈波型變化
造成頻域上突然變寬一下

OQPSK
• Offset QPSK remedies the drawback of QPSK
• The bit error rate and spectrum of OQPSK are identical to those of
QPSK
• Offset QPSK (OQPSK) delays one of the bit streams after serial parallel
conversion:
解決弦波不要變化太劇烈

OQPSK
• Thus, A and B cannot simultaneously change state.
• a smoother transition here relaxes the linearity requirement of the
power amp.
• Maximum phase change is 90 degrees. 相位小頻寬就
較不佔空間
雖然速度和PSK差不多但
是相位差差了90度(PSK
180)

p/4 QPSK
• The signal set consists of two QPSK schemes, one shifted by π/4 with
respect to the other:
• The spectrum and BER of it are identical to those of QPSK

p/4 QPSK 可以讓I,Q同時傳
速度變快

p/4 QPSK
• Maximum phase change is 135 degree

Envelop variation of QPSK
• Quadrature Phase Shift Keying can be filtered using raised cosine
filters to achieve excellent out of band suppression.
• Large envelope variations occur during phase transitions, thus
requiring linear amplification.
180的位置濾
波會影響後面
的波

Spectrum regrowth
Non-linear
Amplifier
不線性放大

Spectrum Comparison
• MSK (or GMSK) has wider but sharper baseband spectrum

MSK Generation
• From the view of frequency. MSK is a subset of FSK, which satisfies
the following condition:
 
Hence, phase change is within one b
f T T
   0.5
b
f T

MSK
• MSK exhibiting the same error rate as QPSK with sharper decay in its
spectrum than the retangular-pulse QPSK family.
• The smooth phase transitions in MSK lower the signal power in the
sidelobes of the spectrum
• But widens the main lobe.
• MSK spectrum has a decay proportional to 4
f

Phase change
• Phase change of MSK and GMSK
• All continuous in phase domain
• MSK is discontinuous in frequency domain
紅色:QPSK的相位變
化(瞬間)
MSK在一個週期內
完成相位變化

GMSK
• Generation of GMSK signal

Gaussian filter
• In MSK , the BT is infinity and this allows the square bit transients to
directly modulate the VCO.
• BT is 3dB bandwidth symbol time product
• If BT is less than 0.3, some form of combating the ISI is required.

GMSK
• Lowe BT
• Narrow BW
• Sever ISI Problem

3:Data Transmission Slide 72
Intersymbol interference
• Filter can be used to shape the pulse and limit the bandwidth.
• Filtering effect will cause a spreading of individual data symbols.
• For consecutive symbols, this spreading causes part of the symbol energy to overlap with
neighboring symbols, causing intersymbol interference (ISI).
symbol一個周期的資料
Data一個瞬間抓取的資料

Zero ISI
• Pulse shaping for zero ISI: Nyquist channel filtering.
• It is also evident that the sample timing must be very accurate to
minimize the ISI problem.

Raised cosine filtering
• A commonly used realization of the Nyquist filter is a raised cosine
filter.
• So called because the transition band (the zone between passband
and stopband) is shaped like part of a cosine waveform.
• The sharpness of the filter is controlled by the parameter , the filter
roll-off factor.
• When  = 0 this conforms to an ideal brick-wall filter.

Raised cosine filtering
• Actual modulation bandwidth, B = 0.5 X 1/Ts (1 + )

FIR
• Traditionally it has been difficult to construct a filter having a Nyquist
response using analogue components.
• and it has taken the development of the digital signal processor (DSP)
to bring Nyquist and raised cosine filters into everyday use.
• finite impulse response (FIR)

Choice of 
• Benefits of small 
– Maximum bandwidth efficiency achieved.實現最大的帶寬效率。
• Benefits of large 
– Simpler filter – fewer stages (taps) hence easier to implement
with less processing delay.更簡單的過濾器 - 更少的階段（水龍頭），因此更容
易實現與更少的處理延遲。
– Less signal overshoot, resulting in lower peak to mean excursions of
the transmitted signal.
較少的信號過衝，導致較低的峰值意味著發送信號的偏移。
– Less sensitivity to symbol timing accuracy – wider eye opening.對符號計
時精度的敏感度較低 - 較大的眼圖張開。

Gain distortion – filters
• Filters are never perfectly 'flat' in the passband .
• Elliptic or Chebychev filters have very high passband ripple, but also achieve very fast roll-off.
• Butterworth or Bessel filters have much less ripple but also much slower roll-off.
• The raised cosine filter also
exhibits passband ripple,
• It depends on the length (number
of taps) used in the filter.
• The degree of ripple can be
small with very long filter
length, but complex.

Phase distortion
• Many filters have phase variations across the passband and in the
transition band.
• Bessel filter having a very good near linear phase response with
frequency, and
• But Elliptic filter having a very poor response.

Group delay
• Group delay is defined as the rate of change of phase shift with
frequency.
• For a non-linear phase response, the group delay will vary with
frequency as shown here,

Phase distortion
• High power amplifiers
• have non-linear amplitude response with input power.
• they also usually have a non-linear phase response with input power
• Caused by non-linear devices
• Such as varactors.
• Cause AM-PM distortion.
• Has a detrimental effect on
phase based modulation
formats such as M-ary PSK.

Multipath distortion
• More than one propagation path exist
• It causes significant distortion of the received data symbols.
• The same source signal,
arriving by a different route,
will experience a different
path length and hence a
different propagation delay
同向變強
反向變弱

Multipath fading
• If the phase difference approaches 180° ,then the signals will in fact
partially cancel each other.
• If the phase difference approaches 0 ° they will reinforce.

frequency selective fading
• The effect is known as frequency selective fading and gives rise to
notches in the frequency response of the channel.
收訊好
傳輸速度越快

Multipath fading
• Time domain problem : intersymbol interference will occur.
• Channel equalizers are often employed. 通道均衡器經常被使用

Coping with multipath fading
• Spectral spreading
• Direct sequence spread spectrum uses a wideband data sequence to mix with a narrowband data
signal and thence spread the energy .
• A small proportion of the spread signal energy will be lost in the frequency selective fades and
the majority will pass.
• By de-spreading the signal in the receiver, a reasonable copy of the original transmitted signal can
be obtained.
• Data coding and channel equalization are often employed in addition to the spreading to improve
the integrity of the channel.
展頻
應用:wifi
Multipath很嚴重
因為訊號會一直在室內反彈

Coping with multipath fading
• Frequency hopping
• It approach means that for some of the time the signal will fall within
a selective fade, but for most of the time, it will be passed within a
non-fading portion of the channel.
• With extra coding a high integrity communications link can be
established
跳頻
應用:藍芽

Diversity
Space Diversity
Time Diversity
Frequency Diversity

Channel coding
• Error detection schemes – ARQ (Automatic Repeat Request Systems).
• Stop and Wait ARQ,Go Back N ARQ ,Selective ARQ
• Error detection and correction –This process is known as FEC
(Forward Error Correction).

Parity Check
• Parity Check
UART在使用的

Parity Check Circuit
• Parity Check Circuit

Block coding
• Hamming codes
• Interleaving
• BCH (Bose-Chaudhuri-Hocquenghem)
• Reed–Solomon (RS) codes

Convolutional coding
• Viterbi convolutional code
• Trellis Diagrams
• Turbo Code

Viterbi algorithm
• The Viterbi algorithm was conceived by Andrew Viterbi.
• It is an error-correction scheme for noisy digital communication links.
• It’s finding universal application in decoding the convolutional codes
used in both CDMA and GSM digital cellular, dial-up modems, satellite,
deep-space communications, and 802.11 wireless LANs.
• It is now also commonly used in speech recognition, keyword spotting,
computational linguistics, and bioinformatics.

雙工，復用和多路訪問

Duplex
• Half-duplex
• Full-duplex
• Time division duplex (TDD)
• Time division duplex has a strong advantage in the case where the asymmetry
of the uplink and downlink data speed is variable
• Frequency division duplex (FDD)
• Frequency division duplex is much more efficient in the case of symmetric
traffic. In this case TDD tends to waste bandwidth during switchover from
transmit to receive.

• 時分雙工（英文縮寫為TDD，Time-Division Duplexing），是利用時間分隔多工技術來分隔傳送及接收的信號。它利
用一個半雙工的傳輸來模擬全雙工的傳輸過程。時分雙工在非對稱網路（上傳及下載頻寬不平衡的網路）有明顯
的優點，它可以根據上傳及下載的資料量，動態的調整對應的頻寬，如果上傳資料量大時，就會提高上傳的頻寬，
若資料量減少時再將頻寬降低。時分雙工的另一個好處是在緩慢移動的系統中，上傳及下載的無線電路徑大致相
同，因此類似波束成形的技術可以運用在時分雙工的系統中
• 頻分雙工（英文縮寫為FDD，Frequency-Division Duplexing），是利用頻率分隔多工技術來分隔傳送及接收的信號。
上傳及下載的區段之間用「頻率偏移」（frequency offset）的方式分隔。若上傳及下載的資料量相近時，頻分雙工
比時分雙工更有效率。在這個情形下，時分雙工會在切換傳送接收時，浪費一些頻寬，因此延遲時間較長，而且
其線路較複雜且耗電。頻分雙工的另一個好處是在無線電收發規劃上較簡單且較有效率，因為一個裝置傳送及接
收使用不同的頻帶，因此裝置不會接收到自己傳出的資料，傳送及接收的資料也不會互相影響。在時分雙工系統
中，需在鄰近的區段中增加保護區段（guard band），但這會使頻譜效率下降。否則就要有同步機制，使一裝置的
傳送和另一裝置的接收同步。同步機制會增加系統的複雜度及成本，而且因為所有的裝置及時間區塊都要同步，
也降低了頻寬使用的靈活性。

Multiplexing 多工
• Multiplexer :Multiplexing is the combining of two or more
information channels onto a common transmission medium.
• Generally, it is always used in telecommunication.
• In electrical communications, the two basic forms of multiplexing are :
• time-division multiplexing (TDM) and
• frequency-division multiplexing (FDM).
• In optical communications:
• FDM is referred to as wavelength-division multiplexing (WDM).

分時多工（Time-Division Multiplexing，TDM）是一種數位或者模擬（較罕見）的多工技術。使用這種技術，兩個
以上的訊號或資料流可以同時在一條通訊線路上傳輸，其表現為同一通訊頻道的子頻道。但在物理上來看，訊號
還是輪流占用物理通道的。時間域被分成周期迴圈的一些小段，每段時間長度是固定的，每個時段用來傳輸一個
子頻道。例如子頻道1的採樣，可能是位元組或者是資料塊，使用時間段1，子頻道2使用時間段2，等等。一個
TDM的影格包含了一個子頻道的一個時間段，當最後一個子頻道傳輸完畢，這樣的過程將會再重複來傳輸新的影
格，也就是下個訊號片段。
波長分波多工（Wavelength Division Multiplexing，WDM）是利用多個雷射器在單條光纖上同時發送多束不同波長
雷射的技術。每個訊號經過數據（文本、語音、視訊等）調變後都在它獨有的色帶內傳輸。WDM能使電話公司和
其他運營商的現有光纖基礎設施容量大增。
正交分頻多工（英語：Orthogonal frequency-division multiplexing, OFDM）有時又稱為分離複頻調變技術（英語：
discrete multitone modulation, DMT），可以視為多載波傳輸的一個特例，具備高速率資料傳輸的能力，加上能有效
對抗頻率選擇性衰減，而逐漸獲得重視與採用。
OFDM使用大量緊鄰的正交子載波（Orthogonal sub-carrier），每個子載波採用傳統的調變方案，進行低符號率調製。
可以視為一調變技術與多工技術的結合。

Difference
• - Time Division Multiplexing (TDM) imply partitioning the bandwidth
of the channel connecting two nodes into finite set of time slots.
• - Time Division multiple Access (TDMA) imply partitioning the
bandwidth of a channel shared by many nodes, typically an
infrastructure node and several mobile nodes, where each node gets
to access its dedicated time slot.

Multiple Access
• FDMA : Speak with different pitches
• TDMA : Speak alternately
• CDMA : Speak with different language

TDMA : 是一種為實現共享傳輸介質（一般是無線電領域）或者網路的通
訊技術。它允許多個用戶在不同的時間片（時槽）來使用相同的頻率。
用戶迅速的傳輸，一個接一個，每個用戶使用他們自己的時間片。這允
許多用戶共享同樣的傳輸媒體（例如：無線電頻率）。
TDMA在美國通常也指第二代（2G）行動電話標準，具體說是指IS-136或
者D-AMPS這些標準使用TDMA技術分時共享載波的帶寬。
FDMA :是利用不同的頻率分割成不同頻道的多址技術。FDMA技術為用
戶單獨分配了一或多個頻段，或通道，用於類比傳輸過程，如固網電
信、無線電、衛星通訊等。FDMA的替代品包括TDMA，CDMA和SDMA。
缺點：串擾可能造成頻率間的干擾並破壞傳輸。
CDMA : 是一種多址接入的無線通訊技術。CDMA最早用於軍用通訊，但時
至今日，已廣泛應用到全球不同的民用通訊中。在CDMA行動通訊中，將
話音訊號轉換為數位訊號，給每組數據話音封包增加一個地址，進行擾碼
處理，然後將它發射到空中。CDMA最大的優點就是相同的帶寬下可以容
納更多的呼叫，而且它還可以隨話音傳送數據資訊。

FDMA
• Frequency Division Multiple Access
• If a channel has a bandwidth W Hz, and individual users require B Hz,
then the channel in theory should be able to support W/B users

FDMA
• Efficiency of frequency multiplexing
• It is governed by how effectively the transmission bandwidth is constrained
by each user, such as  of RRC.
• It is also dependent on how good (selective) the 'de-multiplexing' system is at
filtering out the modulation corresponding to each user.
優點
頻率復用的效率
它受到每個用戶（如RRC）傳輸帶寬的有效限制。
這也取決於“多路分解”系統在篩選出對應於每個用
戶的調製時有多好（選擇性）。

Challenges of FDMA
• Near-far effect
• very large variations in received signal power that arise from users in
different frequency is one of the biggest challenges.
• If the strong signal is producing any out-of-band radiation in the slot
occupied by the weak signal, this can easily swamp the weak signal corrupting
the communications
• Typical up to 100 dB
缺點
不同頻率的用戶產生的接收信號功率的巨大變化是最大的挑戰之一。
如果強信號在弱信號佔用的時隙中產生任何帶外輻射，則這可以容易地淹沒破壞通信的弱信號
典型值高達100 dB

Challenges of FDMA
• Solution :
• Side-lobe energy of digital modulation formats, such as and on designing modulation formats
that are not overly sensitive to amplifier distortion.
• CPFSK , GMSK: are all driven by this near-far problem in the wireless application
• Other challenges
• Doppler shift and local oscillator error : in the radio environment include dealing with the
frequency cause uncertainty for any individual user .
• This inevitable error requires guard-bands to be allocated between frequency slots, thus
sacrificing some of the efficiency of the FDMA scheme.
解答：
數字調製格式的旁瓣能量，例如設計對調製器失真不太敏感的調製格式。
CPFSK，GMSK：在無線應用中都受到這個近遠程問題的驅動
其他挑戰
多普勒頻移和本地振盪器誤差：在無線電環境中包括處理任何個人用戶的頻率不確定性。
這個不可避免的錯誤需要在頻隙之間分配保護頻帶，從而犧牲了FDMA方案的一些效率。

Advantages of FDMA
• Better ISI performance arising from path delay
• Longer symbol time
• Another advantage of FDMA is that the bandwidth of the TX and RX
circuitry is kept to a minimum or narrow, (particularly the bandwidth
over which power amplifiers are to be made linear),
重要優點
路徑延遲引起的ISI性能更好
更長的符號時間
FDMA的另一個優點是TX和RX電路的帶寬保
持在最小或者窄（特別是功率放大器線性
化的帶寬），

Disadvantage of FDMA
• Frequency stability : if the guard-bands are to be kept to a minimum,
the need for guard-bands has traditionally been a bigger problem for
FDMA use.
• Solution : Requiring very costly and high stability oscillators in the modems.
• Frequency selective fading :
• FDMA has the susceptibility of any individual narrow frequency slot to
frequency selective fading which can cause loss of signal.
頻率穩定度：如果要將保護頻帶保持在最低限度，保護頻帶的需求傳統上是FDMA使用中的一個更大的問題。
解決方案：在調製解調器中需要非常昂貴和高穩定性的振盪器。
頻率選擇性衰落：
FDMA具有任何單個窄頻隙對頻率選擇性衰落的敏感性，這會導致信號丟失。

TDMA
• Operation : The user has access to a modem operating at a rate
several times.
• Channel Capacity : if the data rate on the channel is w bits/second,
and each individual user requires only b bits/second, then the system
can support w/b simultaneous users.

Capacity of TDMA TDMA的容量
• Issue : TDMA is very likely that the channel capacity is being
'wasted‘ because time slots are regularly assigned.
• Solution :To maximize the use of a channel resource under these
circumstances.
• packet based transmission is now common on wired links. (e.g. Ethernet)
• user is not given a fixed repeated time slot, but rather allocated a time slot
'on demand'
問題：由於時隙是定期分配的，TDMA很可能是“浪費”了信道
容量。
解決方案：在這種情況下最大限度地使用渠道資源。
基於分組的傳輸現在在有線鏈路上很常見。（例如以太網）
用戶沒有被賦予固定的重複時隙，而是分配了“按需”的時隙

Challenges of TDMA
• Challenge : Again, the 'near-far' effect comes into play, with signals
from a distant user taking longer to arrive at the base-station than
those from a near user.
• Solution : Guard-times are required between time slots
• Challenge : The near-far problem also gives rise to the same signal
strength fluctuations in the base-station.
• Result : No problem with adjacent channel interference as no user is
operating concurrently with another.
挑戰：再次，“近遠”效應發揮作用，遠方用戶的信號比來自近用戶的信號需要更長的時間才能到達基站。
解決方案：時隙之間需要保護時間
挑戰：近遠端問題也會在基站中產生相同的信號強度波動。
結果：由於沒有用戶與另一個用戶同時操作，所以鄰頻干擾沒有問題。

Challenges of TDMA
• Challenges : Round-trip delay
• If the distance between MS&BS is 30Km, the delay is about 0.2ms.
• Solutions : Time Advance
• The timing advance(TA) is calculated by the BSS, based on the bursts received
from the MS.
• automatically advances the start time of its own uplink transmission in order
to compensate for the up-link time delay.
挑戰：往返延遲
如果MS和BS之間的距離是30Km，則延遲約為0.2ms。
解決方案：時間提前
時間提前量（TA）由BSS根據從MS接收到的突發來計算。
自動提前其自己的上行鏈路傳輸的開始時間以便補償上行鏈路時間延遲。

Advantages of TDMA
• Slighter Frequency selective fading:
• Variable user data rate : the ease with which users can be given variable
data rate services by simply assigning them multiple time slots.
可變的用戶數據速率：通過簡單地為用戶分配多個時隙，用
戶可以輕鬆獲得可變數據速率業務。

Advantages of TDMA
• Only one PA : There is only one power amplifier required to support
multiple users for all time slot users.
• Traditionally with FDMA, each user channel at the base-station has
required an individual power amplifier, the output of which is
combined at high power to feed a single common antenna.
• Because the frequency is different.
• Saves Power : Each units is only on for part of time for receiver.
只有一個PA：只有一個功率放大器需要支持所有時隙用戶的多個用戶。
傳統上使用FDMA，基站的每個用戶信道都需要一個單獨的功率放大器，其輸出以高功率組合以饋送一個公共天
線。
因為頻率不同。
節省電力：每個單位只有部分時間接收。

Disadvantages of TDMA
• System Timing Issue : For the same data rate, TDMA is with shorter
symbol data period than FDMA.
• higher peak power rating for the power amplifier :
• Because TDMA use also requires each user terminal to support a much higher
data rate than the user information rate
系統時序問題：對於相同的數據速率，TDMA比FDMA具有更短的符號數據周期。
功率放大器的峰值功率額定值更高：
由於TDMA使用也要求每個用戶終端支持比用戶信息速率高得多的數據速率

CDMA
• Code Division Multiple Access (CDMA)
• Advantages :
• The interference immunity of CDMA for multi-user communications
• It has very good spectral efficiency characteristics.
• There are two very distinct types of CDMA system classified as :
• direct sequence CDMA
• frequency hopping CDMA
碼分多址（CDMA）
優點：
CDMA對多用戶通信的抗干擾性
它具有非常好的頻譜效率特性。
有兩種非常不同的CDMA系統分類為：
直接序列CDMA
跳頻CDMA

Frequency hopped CDMA
• Frequency Hopping : it involves taking the narrow bandpass signals
for individual users and constantly changing their positions in
frequency with time.
• Benefit : changing frequency is to ensure that any one user's signal
will not remain within a fade for any prolonged period of time.
• Operation : the carrier
frequencies are assigned
according to a predetermined
sequence or code.
跳頻：它涉及到為個人用戶提供窄帶通信號，並隨著時間不斷地改
變他們的位置。
好處：改變頻率是為了確保任何一個用戶的信號都不會長時間處於
衰落狀態。
運營：運營商
頻率被分配
根據預定
序列或代碼。

Frequency hopped CDMA
• Speed : Frequency hopping is most effective if a fast hopping rate is
used (several thousand times per second)
• Problem 1:
• Need the design of fast switching synthesizers
• Broadband power amplifiers which in practice put an upper limit on the
hopping rate
• Problem 2: the narrowband channels are susceptible to Doppler shift,
local oscillator error.
• Advantages : less vulnerable to
• discrete narrowband interference
• near-far effect problems.
速度：如果使用快速跳躍速率（每秒數千次），跳頻是最有效的
問題1：
需要快速切換合成器的設計
寬帶功率放大器實際上對跳頻速率提出了一個上限
問題2：窄帶信道容易受到多普勒頻移，本地振盪器誤差的影響。
優點：不容易受到
離散的窄帶乾擾
近遠期效應問題。

Direct sequence CDMA
• The wideband spreading signal is generated using a pseudo-random
sequence generator clocked at a very high rate (termed the chipping
rate).
• De-spreading :
• the correct sequence is used at both ends of links.
• the two sequences are time aligned
展頻的CDMA
寬帶擴展信號是使用以非常高的速率
（稱為碼片速率）定時的偽隨機序列發
生器產生的。
去擴散：
鏈接兩端都使用正確的順序。
這兩個序列是時間對齊的

Direct sequence CDMA
• Capacity Limits : If there is some correlation between spreading codes,
as is almost always the case, then there will be a small contribution to
any individual de-spread user signal from all the other spread users
on the channel.
共享經濟
容量限制：如果擴頻碼之間存在某種相
關性，幾乎總是如此，那麼對於來自信
道上的所有其他擴頻用戶的任何單個解
擴用戶信號將有一個小貢獻。

Advantages of CDMA
• Spread spectrum CDMA overcomes frequency selective fading by
ensuring that most of the spread signal energy falls outside the fading
'notches‘.
• Flexible user data rate: flexibility to accommodate variable user data
capacity
• Each user in a spread spectrum CDMA system can increase their modulation
rate and local narrowband modulation bandwidth.
• Flexible user numbers :
• By slightly over-subscribing the number of users and their 'spread energy
quota' on a spread spectrum CDMA system
優點
擴頻CDMA通過確保大多數擴頻信號能量落在衰落“陷波”之外來克服頻率選
靈活的用戶數據速率：靈活地適應可變的用戶數據容量
擴頻CDMA系統中的每個用戶可以增加其調製速率和本地窄帶調製帶寬。
靈活的用戶號碼：
通過在擴頻CDMA系統上略微超額訂購用戶數量及其“擴頻能量配額”

Disadvantages of CDMA
• Penalty : the signal processing overhead involved with such high rate
and bandwidth transmission.
• Power control : it has also been identified as a critical issue in
maximizing the number of users that can be supported on a given
common frequency channel.
• Contiguous block :CDMA also requires a large amount of bandwidth
to be available in a contiguous block
• Typically bandwidths of 5 MHz upwards are desirable for best
communications performance.
• 1.25 MHz for IS-95
訊號處理要
很強
缺點
懲罰：涉及如此高速率和帶寬傳輸的信號處理開銷。
功率控制：在給定的公共頻道上可以支持的用戶數量最大化的過程中，
它也被認為是一個關鍵問題。
連續的塊：CDMA也需要大量的帶寬在連續的塊中可用
為了獲得最佳的通信性能，通常需要5 MHz以上的帶寬。

Combination
• TDMA / FDMA combination
• We have already seen some examples of digital communication
systems exploiting combinations of multi-user access techniques.
• GSM, although primarily a TDMA system, requires several 200 kHz
frequency channels (each carrying eight time slots) in order to
provide a practical high capacity cellular system and can thus be
viewed as an FDMA system also.
TDMA / FDMA組合
我們已經看到一些利用多用戶訪問技術組合的數字通信系
統的例子。
GSM雖然主要是TDMA系統，但為了提供實用的高容量蜂
窩系統，需要幾個200kHz頻率信道（每個信道攜帶8個時
隙），因此也可以被看作FDMA系統。

AMPS
• Channel Number : 833

NADC
• North American Digital System
• IS-54 when it includes AMPS

GSM
• Global System for Mobile Communication
• TDMA/FDM

IS95
• Qualcomm CDMA

DECT
• Digital European Cordless Telephone

Analog Cellular Telephone
n/a
n/a
n/a
Channel Bit Rate
FM
FM
FM
Modulation
NMT-450: 25 kHz
NMT-900: 12.5 kHz
ETACS: 25 kHz
NTACS: 12.5 kHz
AMPS: 30 kHz
NAMPS: 10 kHz
Channel Spacing
1
Users Per Channel
NMT-450: 200
NMT-900: 1999
ETACS: 1240
NTACS: 400
AMPS: 832
NAMPS: 2496
Number of Channels
FDD
FDD
FDD
Duplex Method
FDMA
FDMA
FDMA
Multiple Access
Method
NMT-450:
Rx: 463-468
Tx: 453-458
NMT-900:
Rx: 935-960
Tx: 890-915
ETACS:
Rx: 916-949
Tx: 871-904
NTACS:
Rx: 860-870
Tx: 915-925
Rx: 869-894
Tx: 824-849
Mobile Frequency
Range (MHz)
NMT
Nordic Mobile
Telephone
TACS
Total Access
Communication System
AMPS/NAMPS
Narrow Band Advanced
Mobile Phone System
Standard
Analog Cellular Telephones
n/a
n/a
n/a
Channel Bit Rate
FM
FM
FM
Modulation
NMT-450: 25 kHz
NMT-900: 12.5 kHz
ETACS: 25 kHz
NTACS: 12.5 kHz
AMPS: 30 kHz
NAMPS: 10 kHz
Channel Spacing
1
Users Per Channel
NMT-450: 200
NMT-900: 1999
ETACS: 1240
NTACS: 400
AMPS: 832
NAMPS: 2496
Number of Channels
FDD
FDD
FDD
Duplex Method
FDMA
FDMA
FDMA
Multiple Access
Method
NMT-450:
Rx: 463-468
Tx: 453-458
NMT-900:
Rx: 935-960
Tx: 890-915
ETACS:
Rx: 916-949
Tx: 871-904
NTACS:
Rx: 860-870
Tx: 915-925
Rx: 869-894
Tx: 824-849
Mobile Frequency
Range (MHz)
NMT
Nordic Mobile
Telephone
TACS
Total Access
Communication System
AMPS/NAMPS
Narrow Band Advanced
Mobile Phone System
Standard
Analog Cellular Telephones

Digital Cellular Telephone
270.833 kb/s
1.2288 Mb/s
48.6 kb/s
Channel Bit Rate
GMSK
(0.3 Gaussian Filter)
GMSK
8-PSK (EDGE only)
QPSK/OQPSK
p/4 DQPSK
Modulation
200 kHz
200 kHz
1250 kHz
30 kHz
Channel Spacing
8
15-50
3
Users Per Channels
374
124
20
832
Number of Channels
FDD
FDD
FDD
FDD
Duplex Method
TDMA/FDM
TDMA/FDM
CDMA/FDM
TDMA/FDM
Multiple Access
Method
Rx: 1805-1880
Tx: 1710-1785
Rx: 869-894
Tx: 824-849
Rx: 925-960
Tx: 880-915
Rx: 1805-1880
Tx: 1710-1785
Rx: 1930-1990
Tx: 1850-1910
Rx: 869-894
Tx: 824-849
Rx: 1930-1990
Tx: 1850-1910
Rx: 2110-2170
Tx: 1920-1980
(CDMA2000 Asia)
Rx: 869-894
Tx: 824-849
Rx: 1930-1990
Tx: 1850-1910
Mobile Frequency
Range (MHz)
DCS 1800/DCS 1900
Digital Communication System
GSM
Global System for Mobile Communication
CDMA
IS-95
Code Division Multiple Access
TDMA
IS-54/IS-136
Time Division Multiple Access
Standard
Digital Cellular Telephones
270.833 kb/s
1.2288 Mb/s
48.6 kb/s
Channel Bit Rate
GMSK
GMSK
8-PSK (EDGE only)
QPSK/OQPSK
p/4 DQPSK
Modulation
200 kHz
200 kHz
1250 kHz
30 kHz
Channel Spacing
8
15-50
3
Users Per Channels
374
124
20
832
Number of Channels
FDD
FDD
FDD
FDD
Duplex Method
TDMA/FDM
TDMA/FDM
CDMA/FDM
TDMA/FDM
Multiple Access
Method
Rx: 1805-1880
Tx: 1710-1785
Rx: 869-894
Tx: 824-849
Rx: 925-960
Tx: 880-915
Rx: 1805-1880
Tx: 1710-1785
Rx: 1930-1990
Tx: 1850-1910
Rx: 869-894
Tx: 824-849
Rx: 1930-1990
Tx: 1850-1910
Rx: 2110-2170
Tx: 1920-1980
(CDMA2000 Asia)
Rx: 869-894
Tx: 824-849
Rx: 1930-1990
Tx: 1850-1910
Mobile Frequency
Range (MHz)
DCS 1800/DCS 1900
GSM
CDMA
IS-95
TDMA
IS-54/IS-136
Standard

Digital Cellular Telephone
270.833 kb/s
1.2288 Mb/s
48.6 kb/s
Channel Bit Rate
GMSK
8-PSK (EDGE only)
QPSK/OQPSK
p/4 DQPSK
Modulation
200 kHz
1250 kHz
30 kHz
Channel Spacing
8
15-50
3
Users Per Channels
124
20
832
Number of Channels
FDD
FDD
FDD
Duplex Method
TDMA/FDM
CDMA/FDM
TDMA/FDM
Multiple Access
Method
Rx: 869-894
Tx: 824-849
Rx: 925-960
Tx: 880-915
Rx: 1805-1880
Tx: 1710-1785
Rx: 1930-1990
Tx: 1850-1910
Rx: 869-894
Tx: 824-849
Rx: 1930-1990
Tx: 1850-1910
Rx: 2110-2170
Tx: 1920-1980
(CDMA2000 Asia)
Rx: 869-894
Tx: 824-849
Rx: 1930-1990
Tx: 1850-1910
Mobile Frequency
Range (MHz)
GSM
CDMA
IS-95
TDMA
IS-54/IS-136
Standard
270.833 kb/s
1.2288 Mb/s
48.6 kb/s
Channel Bit Rate
GMSK
8-PSK (EDGE only)
QPSK/OQPSK
p/4 DQPSK
Modulation
200 kHz
1250 kHz
30 kHz
Channel Spacing
8
15-50
3
Users Per Channels
124
20
832
Number of Channels
FDD
FDD
FDD
Duplex Method
TDMA/FDM
CDMA/FDM
TDMA/FDM
Multiple Access
Method
Rx: 869-894
Tx: 824-849
Rx: 925-960
Tx: 880-915
Rx: 1805-1880
Tx: 1710-1785
Rx: 1930-1990
Tx: 1850-1910
Rx: 869-894
Tx: 824-849
Rx: 1930-1990
Tx: 1850-1910
Rx: 2110-2170
Tx: 1920-1980
(CDMA2000 Asia)
Rx: 869-894
Tx: 824-849
Rx: 1930-1990
Tx: 1850-1910
Mobile Frequency
Range (MHz)
GSM
CDMA
IS-95
TDMA
IS-54/IS-136
Standard
42 kb/s
270.833 kb/s
270.833 kb/s
1.2288 Mb/s
p/4 DQPSK
GMSK
GMSK
8-PSK (EDGE only)
QPSK/OQPSK
25 kHz
200 kHz
200 kHz
1250 kHz
3
8
15-50
1600
374
124
20
FDD
FDD
FDD
FDD
TDMA/FDM
TDMA/FDM
TDMA/FDM
CDMA/FDM
Rx: 810-826
Tx: 940-956
Rx: 1429-1453
Tx: 1477-1501
Rx: 1805-1880
Tx: 1710-1785
Rx: 869-894
Tx: 824-849
Rx: 925-960
Tx: 880-915
Rx: 1805-1880
Tx: 1710-1785
Rx: 1930-1990
Tx: 1850-1910
Rx: 869-894
Tx: 824-849
Rx: 1930-1990
Tx: 1850-1910
Rx: 2110-2170
Tx: 1920-1980
(CDMA2000 Asia)
PDC
Personal Digital Cellular
DCS 1800/DCS 1900
GSM
CDMA
IS-95
cess
42 kb/s
270.833 kb/s
270.833 kb/s
1.2288 Mb/s
p/4 DQPSK
GMSK
GMSK
8-PSK (EDGE only)
QPSK/OQPSK
25 kHz
200 kHz
200 kHz
1250 kHz
3
8
15-50
1600
374
124
20
FDD
FDD
FDD
FDD
TDMA/FDM
TDMA/FDM
TDMA/FDM
CDMA/FDM
Rx: 810-826
Tx: 940-956
Rx: 1429-1453
Tx: 1477-1501
Rx: 1805-1880
Tx: 1710-1785
Rx: 869-894
Tx: 824-849
Rx: 925-960
Tx: 880-915
Rx: 1805-1880
Tx: 1710-1785
Rx: 1930-1990
Tx: 1850-1910
Rx: 869-894
Tx: 824-849
Rx: 1930-1990
Tx: 1850-1910
Rx: 2110-2170
Tx: 1920-1980
(CDMA2000 Asia)
PDC
Personal Digital Cellular
DCS 1800/DCS 1900
GSM
CDMA
IS-95
cess

Analog Cordless Telephone
n/a
n/a
Channel Bit Rate
FM
FM
Modulation
25 kHz
1.7, 20, 25 or 40 kHz
Channel Spacing
CT1: 40
CT1+: 80
10, 12, 15, 20 or 25
Number of Channels
FDD
FDD
Duplex Method
FDMA
FDMA
Multiple Access
Method
CT1: 914/960
CT1+: 885/932
2/48 (U.K.)
26/41 (France)
30/39 (Australia)
31/40 (The Netherlands/Spain)
46/49 (China, S. Korea, Taiwan, U.S.A.)
48/74 (China)
Mobile Frequency
Range (MHz)
CT1/CT1+
Cordless Telephone 1
CT0
Standard
Analog Cordless Telephones
n/a
n/a
Channel Bit Rate
FM
FM
Modulation
25 kHz
1.7, 20, 25 or 40 kHz
Channel Spacing
CT1: 40
CT1+: 80
10, 12, 15, 20 or 25
Number of Channels
FDD
FDD
Duplex Method
FDMA
FDMA
Multiple Access
Method
CT1: 914/960
CT1+: 885/932
2/48 (U.K.)
26/41 (France)
30/39 (Australia)
31/40 (The Netherlands/Spain)
46/49 (China, S. Korea, Taiwan, U.S.A.)
48/74 (China)
Mobile Frequency
Range (MHz)
CT1/CT1+
CT0
Standard
Analog Cordless Telephones

Digital Cordless Telephone
384 kb/s
1.152 Mb/s
72 kb/s
Channel Bit Rate
p/4 DQPSK
GFSK
GFSK
Modulation
300 kHz
1.728 MHz
100 kHz
Channel Spacing
4
12
1
Users Per Channel
300
10
40
Number of Channels
TDD
TDD
TDD
Duplex Method
TDMA/FDM
TDMA/FDM
TDMA/FDM
Multiple Access
Method
1895-1918
1880-1900
CT2: 864/868
CT2+: 944/948
Mobile Frequency
Range (MHz)
PHS
Personal Handy Phone System
DECT
Digital Enhanced Cordless Telephone
CT2/CT2+
Standard
Digital Cordless Telephones
384 kb/s
1.152 Mb/s
72 kb/s
Channel Bit Rate
p/4 DQPSK
GFSK
GFSK
Modulation
300 kHz
1.728 MHz
100 kHz
Channel Spacing
4
12
1
Users Per Channel
300
10
40
Number of Channels
TDD
TDD
TDD
Duplex Method
TDMA/FDM
TDMA/FDM
TDMA/FDM
Multiple Access
Method
1895-1918
1880-1900
CT2: 864/868
CT2+: 944/948
Mobile Frequency
Range (MHz)
PHS
Personal Handy Phone System
DECT
Digital Enhanced Cordless Telephone
CT2/CT2+
Standard
Digital Cordless Telephones
歐洲電話

Wireless Data
25
12 Mb/s symbol rate
5.5-54 Mb/s
1, 2 or 11 MB/s
1 Mb/s symbol rate
1.6, 10 Mbps
1 Mb/s symbol rate
721 kb/s raw data
56 kb/s return
19.2 kb/s
Channel Bit Rate
(0.5 G
OFDM: QPSK, QAM
(0.5 Gaussian filter)
OFDM: BPSK (5.5 Mb/s)
OFDM: 16QAM (24, 26 Mb/s)
OFDM: 64QAM (54 Mb/s)
FHSS: GFSK
DSSS: DBPSK (1/MB/s)
DQPSK (2 MB/s)
CCK: QPSK (11 Mb/s)
FHSS
Shaped Binary FM
GMSK
Modulation
OFDM: 20 MHz
FHSS: 1 MHz
DSSS: 25 MHz
1 MHz, 3.5 MHz
1 MHz
30 kHz
Channel Spacing
127
127
8 active
7 active, 200 inactive
1
Users Per Channel
FHSS: 79
DSSS: 11
79
(23 in Japan, Spain, France)
832
Number of Channels
TDD
TDD
TDD
TDD
FDD
Duplex Method
CSMA/CA
CSMA/CA
Frequency hopping
Frequency hopping
FDMA
Multiple Access
Method
24
100
(N.
24
100
(
10
5150-5250
(USA lower band)
5250-5350
(USA middle band)
5725-5825
(USA upper band)
2401-2462
1000 mW/MHz
(North America)
2412-2472
100 mW/MHz
(Europe)
2483
10 mW/MHz
(Japan)
2402-2480
(North America & Europe)
2447-2473 (Spain)
2448-2482 (France)
2473-2495 (Japan)
2402-2480
2447-2473 (Spain)
2448-2482 (France)
2473-2495 (Japan)
Rx: 869-894
Tx: 824-849
Mobile Frequency
Range (MHz)
IEEE
IEEE 802.11a
IEEE 802.11b
HomeRF
Bluetooth
CDPD
Cellular Digital
Packet Data (WAN)
Standard
Wireless Data
(see telephone specs for data over cell phone)
25
12 Mb/s symbol rate
5.5-54 Mb/s
1, 2 or 11 MB/s
1 Mb/s symbol rate
1.6, 10 Mbps
1 Mb/s symbol rate
721 kb/s raw data
56 kb/s return
19.2 kb/s
Channel Bit Rate
(0.5 G
OFDM: QPSK, QAM
FHSS: GFSK
DQPSK (2 MB/s)
CCK: QPSK (11 Mb/s)
FHSS
Shaped Binary FM
GMSK
Modulation
OFDM: 20 MHz
FHSS: 1 MHz
DSSS: 25 MHz
1 MHz, 3.5 MHz
1 MHz
30 kHz
Channel Spacing
127
127
8 active
1
Users Per Channel
FHSS: 79
DSSS: 11
79
832
Number of Channels
TDD
TDD
TDD
TDD
FDD
Duplex Method
CSMA/CA
CSMA/CA
Frequency hopping
Frequency hopping
FDMA
Multiple Access
Method
24
100
(N.
24
100
(
10
5150-5250
(USA lower band)
5250-5350
(USA middle band)
5725-5825
(USA upper band)
2401-2462
1000 mW/MHz
(North America)
2412-2472
100 mW/MHz
(Europe)
2483
10 mW/MHz
(Japan)
2402-2480
2447-2473 (Spain)
2448-2482 (France)
2473-2495 (Japan)
2402-2480
2447-2473 (Spain)
2448-2482 (France)
2473-2495 (Japan)
Rx: 869-894
Tx: 824-849
Mobile Frequency
Range (MHz)
IEEE
IEEE 802.11a
IEEE 802.11b
HomeRF
Bluetooth
CDPD
Cellular Digital
Packet Data (WAN)
Standard
Wireless Data

Wireless Data
12 Mb/s symbol rate
5.5-54 Mb/s
1, 2 or 11 MB/s
1 Mb/s symbol rate
1.6, 10 Mbps
1 Mb/s symbol rate
721 kb/s raw data
56 kb/s return
19.2 kb/s
Channel Bit Rate
(0
OFDM: QPSK, QAM
FHSS: GFSK
DQPSK (2 MB/s)
CCK: QPSK (11 Mb/s)
FHSS
Shaped Binary FM
GMSK
Modulation
OFDM: 20 MHz
FHSS: 1 MHz
DSSS: 25 MHz
1 MHz, 3.5 MHz
1 MHz
30 kHz
Channel Spacing
127
127
8 active
1
Users Per Channel
FHSS: 79
DSSS: 11
79
832
Number of Channels
TDD
TDD
TDD
TDD
FDD
Duplex Method
CSMA/CA
CSMA/CA
Frequency hopping
Frequency hopping
FDMA
Multiple Access
Method
5150-5250
(USA lower band)
5250-5350
(USA middle band)
5725-5825
(USA upper band)
2401-2462
1000 mW/MHz
(North America)
2412-2472
100 mW/MHz
(Europe)
2483
10 mW/MHz
(Japan)
2402-2480
2447-2473 (Spain)
2448-2482 (France)
2473-2495 (Japan)
2402-2480
2447-2473 (Spain)
2448-2482 (France)
2473-2495 (Japan)
Rx: 869-894
Tx: 824-849
Mobile Frequency
Range (MHz)
IEEE 802.11a
IEEE 802.11b
HomeRF
Bluetooth
CDPD
Cellular Digital
Packet Data (WAN)
Standard
Wireless Data
12 Mb/s symbol rate
5.5-54 Mb/s
1, 2 or 11 MB/s
1 Mb/s symbol rate
1.6, 10 Mbps
1 Mb/s symbol rate
721 kb/s raw data
56 kb/s return
19.2 kb/s
Channel Bit Rate
(0
OFDM: QPSK, QAM
FHSS: GFSK
DQPSK (2 MB/s)
CCK: QPSK (11 Mb/s)
FHSS
Shaped Binary FM
GMSK
Modulation
OFDM: 20 MHz
FHSS: 1 MHz
DSSS: 25 MHz
1 MHz, 3.5 MHz
1 MHz
30 kHz
Channel Spacing
127
127
8 active
1
Users Per Channel
FHSS: 79
DSSS: 11
79
832
Number of Channels
TDD
TDD
TDD
TDD
FDD
Duplex Method
CSMA/CA
CSMA/CA
Frequency hopping
Frequency hopping
FDMA
Multiple Access
Method
5150-5250
(USA lower band)
5250-5350
(USA middle band)
5725-5825
(USA upper band)
2401-2462
1000 mW/MHz
(North America)
2412-2472
100 mW/MHz
(Europe)
2483
10 mW/MHz
(Japan)
2402-2480
2447-2473 (Spain)
2448-2482 (France)
2473-2495 (Japan)
2402-2480
2447-2473 (Spain)
2448-2482 (France)
2473-2495 (Japan)
Rx: 869-894
Tx: 824-849
Mobile Frequency
Range (MHz)
IEEE 802.11a
IEEE 802.11b
HomeRF
Bluetooth
CDPD
Cellular Digital
Packet Data (WAN)
Standard
Wireless Data
250/28 kb/s
12 Mb/s symbol rate
5.5-54 Mb/s
1, 2 or 11 MB/s
1 Mb/s symbol rate
1.6, 10 Mbps
1 Mb/s symbol rate
721 kb/s raw data
56 kb/s return
19.2 kb/s
Rate
GFSK
OFDM: QPSK, QAM
FHSS: GFSK
DQPSK (2 MB/s)
CCK: QPSK (11 Mb/s)
FHSS
Shaped Binary FM
GMSK
n
4 MHz
OFDM: 20 MHz
FHSS: 1 MHz
DSSS: 25 MHz
1 MHz, 3.5 MHz
1 MHz
30 kHz
cing
255
127
127
8 active
1
annel
FHSS: 79
DSSS: 11
79
832
annels
FDD
TDD
TDD
TDD
TDD
FDD
hod
TDMA
CSMA/CA
CSMA/CA
Frequency hopping
Frequency hopping
FDMA
ess
2402-2480
1000 mW/MHz
(N. America)
2412-2472
100 mW/MHz
(Europe)
2483
10 mW/MHz
(Japan)
5150-5250
(USA lower band)
5250-5350
(USA middle band)
5725-5825
(USA upper band)
2401-2462
1000 mW/MHz
(North America)
2412-2472
100 mW/MHz
(Europe)
2483
10 mW/MHz
(Japan)
2402-2480
2447-2473 (Spain)
2448-2482 (France)
2473-2495 (Japan)
2402-2480
2447-2473 (Spain)
2448-2482 (France)
2473-2495 (Japan)
Rx: 869-894
Tx: 824-849
ency
Hz)
IEEE 802.15.4
ZigBee
IEEE 802.11a
IEEE 802.11b
HomeRF
Bluetooth
CDPD
Cellular Digital
Packet Data (WAN)
d
Wireless Data
250/28 kb/s
12 Mb/s symbol rate
5.5-54 Mb/s
1, 2 or 11 MB/s
1 Mb/s symbol rate
1.6, 10 Mbps
1 Mb/s symbol rate
721 kb/s raw data
56 kb/s return
19.2 kb/s
Rate
GFSK
OFDM: QPSK, QAM
FHSS: GFSK
DQPSK (2 MB/s)
CCK: QPSK (11 Mb/s)
FHSS
Shaped Binary FM
GMSK
n
4 MHz
OFDM: 20 MHz
FHSS: 1 MHz
DSSS: 25 MHz
1 MHz, 3.5 MHz
1 MHz
30 kHz
cing
255
127
127
8 active
1
annel
FHSS: 79
DSSS: 11
79
832
annels
FDD
TDD
TDD
TDD
TDD
FDD
hod
TDMA
CSMA/CA
CSMA/CA
Frequency hopping
Frequency hopping
FDMA
ess
2402-2480
1000 mW/MHz
(N. America)
2412-2472
100 mW/MHz
(Europe)
2483
10 mW/MHz
(Japan)
5150-5250
(USA lower band)
5250-5350
(USA middle band)
5725-5825
(USA upper band)
2401-2462
1000 mW/MHz
(North America)
2412-2472
100 mW/MHz
(Europe)
2483
10 mW/MHz
(Japan)
2402-2480
2447-2473 (Spain)
2448-2482 (France)
2473-2495 (Japan)
2402-2480
2447-2473 (Spain)
2448-2482 (France)
2473-2495 (Japan)
Rx: 869-894
Tx: 824-849
ency
Hz)
IEEE 802.15.4
ZigBee
IEEE 802.11a
IEEE 802.11b
HomeRF
Bluetooth
CDPD
Cellular Digital
Packet Data (WAN)
d
Wireless Data

Personal Communication Systems
•PACS
(based on PHS cordless)
•DCT-U
(based on DECT cordless)
•Composite CDMA/TDMA
•PCS TDMA
(based on IS-136 cellular)
•PCS CDMA
•PCS 1900
(based on GSM cellular)
Wideband CDMA
Multiple Access
Method
Rx: 1930-1990
Tx: 1850-1910
Rx: 1930-1990
Tx: 1850-1910
Mobile Frequency
Range (MHz)
Low Tier Standards
High Tier Standards
Standard
•PACS
(based on PHS cordless)
•DCT-U
(based on DECT cordless)
•Composite CDMA/TDMA
•PCS TDMA
•PCS CDMA
•PCS 1900
(based on GSM cellular)
Wideband CDMA
Multiple Access
Method
Rx: 1930-1990
Tx: 1850-1910
Rx: 1930-1990
Tx: 1850-1910
Mobile Frequency
Range (MHz)
Low Tier Standards
High Tier Standards
Standard

4: Transceiver Architecture Slide 137
Outline
• Receiver :
• Linearity -> IP3, P1dB
• Noise -> SNR
• Sensitivity & Dynamic Range
• Channel filtering
• Transmitter

1-dB compression point
• The input level that causes the small-signal gain to drop by 1dB.
• Because of : Nonlinearity
• Around -25~-20dBm(63.2m ~ 35.6mV in 50Ω system)
非線性系統-
增益會掉

Desensitization and Blocking
• Cause : A small signal is received and accompanied with a strong
interference.
• If 3 is negative, then gain is reduced.
• RF receiver must withstand 60~70dB signal difference.

Intermodulation(I)
• Harmonics distortion is not very useful to characterize nonliearity.
• ∵ For examples, a low pass filter reduce the hamonics.

Intermodulation(II)
• Perform “two-tone” test.
• If
• Then main part
• and harmonics
Third order intermodulation
Second order intermodulation

Intermodulation(III)
• We call the components at and the 21±2 and 22±1 third-order
intermodulation products
• Note the 21- 2 and 22- 1 tone. It comes closest to the main
tone due to nonlinearity effect.
• Ex : A1=A2, if 1A=1V and 3A3/4=10mV
then we say IM componet is -40dBc, where c means with respect to
the carrier.

Intermodulation(IV)
• IM is a troublesome effect in RF system.
• IM causes a weak signal is corrupted by two strong interference.
• While operating by AM, it still degrades the PM. Because zero-
crossing points are still affected.
• The effect can not be observed from Harmonic distortions.

Intermodulation(V)
• IP3 : Third intercept point
• It is very useful to characterize the linearity
IM3 component increases with A3.
• IIP3 is the input IP3 and OIP3 is at output.
• Figures (a) in linear scale and (b) in log scale.
RF評估非線性的方法

Intermodulation(VI)
• How to calculate IP3
• Let
• Suppose
• then

Intermodulation(VII)
• How to measure IIP3 with a single measurement
• While
• then
IIP3越大越好(表示越線性)

IIP3 & P1dB
• The theoretically relationship is

Cascade Nonlinear Stages
• If
• then

Cascade Nonlinear Stages
• Practical usage :
• Approximation:
• More cascade stages
第一級的增
益
**後級的線性度會被前一級的增益搞砸
sol:前級增益不能太大,越後級線性度越重要(後級幾乎決定
線性度)

General Considerations
• Receiver :
• Noise -> NF
越前級越重要

Thermal Noise
• In the MOSFET
• Short channel: g > 2 ( process dependent )
• Long channel: g =2/3
電晶體的輸出級用電流來看雜訊

Flicker noise
• Flicker noise
• It arise from random trapping of charge at the
oxide-silicon interface of MOSFETs.
• K is a constant and process dependant.

Shot noise
• If carriers cross a potential barrier, then the overall current actually
consists of a large number of random current pulses.
• Usually exists in the BJT
• The random component of the current is called “shot noise” .
• It is

Input Referred Noise
• The overall noise of a circuit can be represented by only two sources placed at the input:
• Ex.
• Note: The two sources are correlated here because they
represent the same mechanism.

Noise Figure
• NF is a measure of how much the SNR degrades as the signal passes
through system.
• Definition :
• Usually in dB unit ( 10log10)
• NF > 1
• If no input noise, NF -> ∞. (not meaningful)

Noise Figure Calculation
(for measurement)

Noise Figure Calculation
• Ex. : In 50ohm system
What is the NF?

Noise Figure of Cascaded Stages
• NF calculation

Noise Figure of Cascaded Stages
• For a special case :
第一級佔非常多的noise

• Receiver :
• Noise -> NF

Sensitivity
• From NF :
• We get :
• Because the RF is 50ohm system :
• Then :
,where B is bandwidth

Sensitivity Calculation
• Ex.:For GSM,SNRmin ~ 12dB, B = 200kHz
• If NF of the receiver path is 9dB,
Then : Sensitivity is -174+9+53+12 = -100 dBm
• If we have a specification with sensitivity of -105dBm,
Then : NF should be : -105+174-53-12 = 4dB

SFDR
• The upper end of DR (actually “spurious-free” dynamic range,(SFDR)
is defined as the max.
• IM <= the noise floor:
• where Noise floor=-174 dBm+NF+10log B
• Then :

SFDR
• Example: GSM,SNRmin ~ 12dB, B = 200kHz, NF is 9, suppose IIP3 =-15
dBm.
• Then, SFDR=2/3(-15-(-112))-12=52.7 dB
• SFDR indicates how much interference the system can tolerate while
providing an acceptable signal quality.

• Receiver :
• SNR
• Linearity -> IP3
• Channel filtering -> Receiver Architecture

Channel filtering
• Receiver :
• Interference Rejection
• High Q filter
• Ex : 900MHz receiver with 60db ANT of 90kHz => Q:~1E7

Channel filtering
• Receiver :
• Bandpass filter selection
• Tradeoff : In-band Loss & Out-band Rejection
• In-band Loss => High Noise (NF) & Low SNR

Channel filtering
• Receiver :
• Band Selection
• Channel Selection
• Reject image
• Relax linearity requirement

Heterodyne Receiver
• Heterodyne : the signal band is translated to much lower frequencies
(IF) so as to relax the Q required of the channel-select filter.
• IF : intermediate frequency.
• It filters out some strong interference to relax the linearity
requirement for the following stages.
2次降頻完成

Problem of image
• Both desirable and undesirable frequency band are all mixed down to
IF
• Solution : We need proper “image rejection”
雖然訊號從1.8
降到0.1但是如
果1.6有訊也會
被一起降到0.1

4: Transceiver ArchitectureSlide 171
Image rejection
• Trade-off for IF frequency selection
• High IF: good image rejection, poor channel selection
• Low IF : good channel selection, image rejection
較好

Image rejection
• High side injection : if LO > in, then image is higher than LO.
• Low side injection : if LO < in, then image is lower than LO.
• High side injection needs high VCO frequency operation.
• Another consideration depends on the distribution of image band
noise.

Half IF
• If an interference is at , the signal is
down-converted to half IF .
• If the following stage suffers from nonlinearity effect, the second
order distortion of the half IF will fall down the wanted IF band.

Heterodyne Receiver
• To enhance the sensitivity and selectivity, heterodyne receiver
downconverts signal two times.
沒有這段就是
Homedyne
(1次降到0Hz)

Homedyne Receiver
• It converts the RF signal once to the baseband.
• Called Homedyne , direct-conversion, zero-IF architecture.
• In Fig.(a), it operates properly on with double –side band AM signal because it overlaps +
and - input spectrum.
• FM & QPSK has the different spectrum in the upper and lower band. Hence , quadrature
modulation is necessary.
• Fig.(b) operated for the quadrature modulation.

Homedyne Receiver
• Advantages:
• No image
• Need no image rejection filter
• Monolithic integration
• LNA need no 50ohm output matching
• Disadvantage :
• DC offset
• IQ mismatch
• Flicker noise_mos在0HZ時有一個低平的雜訊
• LO leakage
缺點:要把這些全部解決才可以
(皆是低頻的問題)

DC offset
• DC offset is very important issue for zero-IF.
• It corrupts the signal.
• It saturates the following stages.
• It arise from :
• Device mismatch
• Signal reflection
• Tx leaks to RX
self-mixing(源頭)

DC offset
• (a) Self-mixing of LO signal
• (b) Strong interferer from input

DC offset Cancellation
• Solution 1: High pass filter can cancel DC offset
• Issue 1: Around dc signal also loses engery.
• Issue 2: A larger capacitor fail to track fast variation in the offset voltage.
• Solutions 2 : DC free coding
• A modulation or coding method carries little signal around the DC
• Suitable for wideband signal
• Solution 3 : Stores the dc offset
• In the TDMA system, the dc offset value can be stored in the C1 with a switch
S1.

DC offset Cancellation
• Issue 3:
• Mandating large C1 due to thermal noise kT/C.
• Offset due to VCO can be detected and stored.
• However, interferer signal randomly appears.
• Hence, averaged dc offset value is necessary.
stored cancelled
C1先記電壓值,開始工作後再抵銷DC offset

I/Q mismatch
• A homodyne incorporates Quadrate mixing for the frequency and
phase modulation scheme.
• Scheme (b) is preferred due to not interfering the main signal path.
通常使用(b)
(a)RF經過90度可
能會有loss,也就
是雜訊

Even Order Distortion
• IP2 : It is used to characterize even order distortion
• Solutions : Differential circuits
• Issue 1 : The front end antenna and duplexer are usually single ended.
• Hence : Transformer is necessary for single to differential but its loss causes higher NF.
• Issue 2 : Differential circuits consume more power.
降共模雜訊

Flicker Noise
• Flicker noise :
• Its noise power is proportional to 1/f.
• It corrupts input signal significantly around DC frequency.
• In the homedyne receiver the down-converted signal is only amplified LNA &
Mixer (~30dB). Hence signal is still very small and prone to corrupted by the
flicker noise.
• Solution : incorporate large device size to minimize the magnitude of
flicker noise.
閃爍噪音：
其噪聲功率與1 / f成正比。
它顯著地損壞了直流頻率的輸入信號。
在homedyne接收機中，下變頻信號僅被放大LNA和混頻器（〜
30dB）。因此，信號仍然非常小，易受到閃爍噪聲的干擾。
解決方案：採用大尺寸的器件來減小閃爍噪聲的大小。

Channel permutation
• (a) Allowing A for nonlinearity and high gain for ADC
• However, the first filter suffers from noise and linearity issue.
• (b) Relax filter noise requirement
• However, requires linear Amp
• (c) Easy to implement filter in digital circuits
• However, require linear and low thermal and quantization noise ADC
越前面線性度要越高
也表示越前面越難做
a和b比選b會比
較好一點,因為
filter比較不好做

Digital IF architecture
• Digital IF : Second down-conversion is performed in the digital circuits.
• Advantages :
• Alleviate DC offset and flicker noise issue
• No IQ phase and gain mismatch issue
• Difficulty : Need high dynamic and high bandwidth ADC.
主流架構

Sampling IF architecture
• Sample and hold action in the ADC also perform the down-conversion.
• Sampling frequency could be a little lower than IF frequency.
• Still needs high performance ADC with high speed and high linearity.
讓訊號再降頻一次

Subsampling Receiver
• Sampling in the time domain causes periodically repeated spectrum
in the frequency domain.
• Signal then can be down-converted by very low frequency sampling
rate.

Subsampling Receiver
• Drawback : Subsampling by a factor of m multiplies the
downconverted noise power of the sampling circuit by a factor of m.

Direct Conversion Transmitter
• Direct conversion : the transmitted frequency is equal to the LO
frequency.
• Matching network :
• It is to provide a maximum power transferring to the antenna.
• It also filters out the out-of-band component that results from the
nonlinearity of PA.
可以順便濾波

Transmitter Architecture
• Baseband / RF interface
• Quadrature modulation :

Transmitter Architecture
• Baseband pulse shaping

Two-step transmitter
• Advantages:
• Avoid the pulling effect from PA
• Better I/Q matching due to lower frequency operation.
• Difficulty : Second BPF must reject out-of-band signal at (1-2) up
to 50 ~ 60 dB.

Philips Pager Rx
• Philips Pager Rx 可降虛部

Lucent GSM Transceiver
• Lucent GSM Transceiver
降2次就需要
怕和前面的71一樣
被干擾到,所以用
284/4來做71

射頻期中整理.pptx

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