The document provides an overview of digital passband modulation techniques. It discusses binary modulation schemes including amplitude-shift keying (ASK), frequency-shift keying (FSK), and phase-shift keying (BPSK). It also covers differential phase-shift keying (DPSK), which removes phase ambiguity in BPSK using differential encoding and decoding. Key aspects like signal representation, spectrum, and detection methods are described for each technique.
Frequency-Shift Keying, also known as FSK is a type of digital frequency modulation. It is also often called as binary frequency shift keying or BFSK
Similar to analog FM, it is a constant-amplitude angle modulation.
This presentation will discuss the concepts behind FSK
Base band transmission
*Wave form representation of binary digits
*PCM, DPCM, DM, ADM systems
*Detection of signals in Gaussian noise
*Matched filter - Application of matched filter
*Error probability performance of binary signaling
*Multilevel base band transmission
*Inter symbol interference
*Eye pattern
*Companding
*A law and μ law
*Correlation receiver
Frequency-Shift Keying, also known as FSK is a type of digital frequency modulation. It is also often called as binary frequency shift keying or BFSK
Similar to analog FM, it is a constant-amplitude angle modulation.
This presentation will discuss the concepts behind FSK
Base band transmission
*Wave form representation of binary digits
*PCM, DPCM, DM, ADM systems
*Detection of signals in Gaussian noise
*Matched filter - Application of matched filter
*Error probability performance of binary signaling
*Multilevel base band transmission
*Inter symbol interference
*Eye pattern
*Companding
*A law and μ law
*Correlation receiver
Salient Features:
The magnitude response is nearly constant(equal to 1) at lower frequencies
There are no ripples in passband and stop band
The maximum gain occurs at Ω=0 and it is H(Ω)=1
The magnitude response is monotonically decreasing
As the order of the filter ‘N’ increases, the response of the filter is more close to the ideal response
This presentation covers:
Some basic definitions & concepts of digital communication
What is Phase Shift Keying(PSK) ?
Binary Phase Shift Keying – BPSK
BPSK transmitter & receiver
Advantages & Disadvantages of BPSK
Pi/4 – QPSK
Pi/4 – QPSK transmitter & receiver
Advantages of Pi/4- QPSK
In communication system, intersymbol interference (ISI) is a form of distortion of a signal in which one symbol interferes with subsequent symbols. This is an unwanted phenomenon as the previous symbols have similar effect as noise, thus making the communication less reliable.
In communication system, the Nyquist ISI criterion describes the conditions which when satisfied by a communication channel (including responses of transmit and receive filters), result in no intersymbol interference(ISI). It provides a method for constructing band-limited functions to overcome the effects of intersymbol interference.
The Quadrature Phase Shift Keying QPSK is a variation of BPSK, and it is also a Double Side Band Suppressed Carrier DSBSC modulation scheme, which sends two bits of digital information at a time, called as bigits.
Instead of the conversion of digital bits into a series of digital stream, it converts them into bit pairs. This decreases the data bit rate to half, which allows space for the other users.
QPSK (Quadrature Phase Shift Keying) is type of phase shift keying. Unlike BPSK which is a DSBCS modulation scheme with digital information for the message, QPSK is also a DSBCS modulation scheme but it sends two bits of digital information a time (without the use of another carrier frequency).
The amount of radio frequency spectrum required to transmit QPSK reliably is half that required for BPSK signals, which in turn makes room for more users on the channel.
Phase-shift keying (PSK) is a digital modulation scheme that conveys data by changing (modulating) the phase of a reference signal (the carrier wave). The modulation is impressed by varying the sine and cosine inputs at a precise time. It is widely used for wireless LANs, RFID and Bluetooth communication
Frequency-shift keying (FSK) is a frequency modulation scheme in which digital information is transmitted through discrete frequency changes of a carrier signal.[1] The technology is used for communication systems such as amateur radio, caller ID and emergency broadcasts
The Presentation includes Basics of Non - Uniform Quantization, Companding and different Pulse Code Modulation Techniques. Comparison of Various PCM techniques is done considering various Parameters in Communication Systems.
Salient Features:
The magnitude response is nearly constant(equal to 1) at lower frequencies
There are no ripples in passband and stop band
The maximum gain occurs at Ω=0 and it is H(Ω)=1
The magnitude response is monotonically decreasing
As the order of the filter ‘N’ increases, the response of the filter is more close to the ideal response
This presentation covers:
Some basic definitions & concepts of digital communication
What is Phase Shift Keying(PSK) ?
Binary Phase Shift Keying – BPSK
BPSK transmitter & receiver
Advantages & Disadvantages of BPSK
Pi/4 – QPSK
Pi/4 – QPSK transmitter & receiver
Advantages of Pi/4- QPSK
In communication system, intersymbol interference (ISI) is a form of distortion of a signal in which one symbol interferes with subsequent symbols. This is an unwanted phenomenon as the previous symbols have similar effect as noise, thus making the communication less reliable.
In communication system, the Nyquist ISI criterion describes the conditions which when satisfied by a communication channel (including responses of transmit and receive filters), result in no intersymbol interference(ISI). It provides a method for constructing band-limited functions to overcome the effects of intersymbol interference.
The Quadrature Phase Shift Keying QPSK is a variation of BPSK, and it is also a Double Side Band Suppressed Carrier DSBSC modulation scheme, which sends two bits of digital information at a time, called as bigits.
Instead of the conversion of digital bits into a series of digital stream, it converts them into bit pairs. This decreases the data bit rate to half, which allows space for the other users.
QPSK (Quadrature Phase Shift Keying) is type of phase shift keying. Unlike BPSK which is a DSBCS modulation scheme with digital information for the message, QPSK is also a DSBCS modulation scheme but it sends two bits of digital information a time (without the use of another carrier frequency).
The amount of radio frequency spectrum required to transmit QPSK reliably is half that required for BPSK signals, which in turn makes room for more users on the channel.
Phase-shift keying (PSK) is a digital modulation scheme that conveys data by changing (modulating) the phase of a reference signal (the carrier wave). The modulation is impressed by varying the sine and cosine inputs at a precise time. It is widely used for wireless LANs, RFID and Bluetooth communication
Frequency-shift keying (FSK) is a frequency modulation scheme in which digital information is transmitted through discrete frequency changes of a carrier signal.[1] The technology is used for communication systems such as amateur radio, caller ID and emergency broadcasts
The Presentation includes Basics of Non - Uniform Quantization, Companding and different Pulse Code Modulation Techniques. Comparison of Various PCM techniques is done considering various Parameters in Communication Systems.
Solution includes design of systems architectures and mechanical and electrical installations, instrumentation of the integrated systems, and certification for ground and flight tests. visit for more info @ http://www.qinetiq.com/services-products/air/Pages/aircraft-system-integration-and-upgrades.aspx
QinetiQ solution includes design of systems architectures and mechanical and electrical installations, instrumentation of the integrated systems, and certification for ground and flight tests.
The following documents defines the different encoding schemes/Techniques.
These encoding schemes have different way to solve a problem.
The techniques are used in network and wireless devices only. Although there are many different techniques that used in other devices and network as well but i used/ mention these techniques for only network and wireless devices. These techniques are also used in mobile network. There are also many lectures for this but i uploaded only lecture 5 because i found it important to everyone.
This includes Digital signal data transmission, Base band and band pass transmission. Also detailed with PAM, PPM, PWM, PCM, DPCM, DM, ADM, ASK, PSK, FSK.
This slide describe the techniques of digital modulation and Bandwidth Efficiency:
The first null bandwidth of M-ary PSK signals decrease as M increases while Rb is held constant.
Therefore, as the value of M increases, the bandwidth efficiency also increases.
The following resources come from the 2009/10 BEng (Hons) in Digital Communications & Electronics (course number 2ELE0064) from the University of Hertfordshire. All the mini projects are designed as level two modules of the undergraduate programmes.
The objective of this module is to have built communication links using existing AM modulation, PSK modulation and demodulation blocks, constructed AM modulators and constructed PSK modulators using operational function blocks based on their mathematical expressions, and conducted simulations of the links and modulators, all in Simulink®.
This is the presentation on the basic concepts of electronics and communication. In this we can get the knowledge of the basic things used in the airport in CNS department.
1. TELE3113 Analogue and Digital
Communications –
Digital Band-pass Modulation
Wei Zhang
w.zhang@unsw.edu.au
School of Electrical Engineering and Telecommunications
The University of New South Wales
29 Sept 2009
2. Passband Communication
• In baseband date transmission, a sequence of bits is represented in
the form of discrete pulse modulated wave (PAM, PPM, PWM) or
digital baseband modulated wave (PCM, DM, DPCM) that are
transmitted over a low-pass channel (e.g., a coaxial cable).
• For a bandpass channel, e.g., wireless radio, microwave, satellite,
optical fibre, we have to resort to the use of a modulation strategy
configured around a carrier signal.
• Passband signals are generated by modulating a baseband signal
onto a carrier.
• The frequency band of the transmitted signals over the channel is
centred at the carrier frequency.
3. Passband Communication
• Passband Analog communication
– A baseband analog signal is modulated onto a carrier using AM,
FM, PM techniques.
• Passband Digital communication
– A baseband digital signal is modulated onto a carrier using
digital signalling techniques such as
• ASK (Amplitude shift keying),
• PSK (Phase shift keying),
• FSK. (frequency shift keying),
4. Passband Digital Signalling
• In digital signalling, the binary digital information is first encoded
using a particular coding scheme, e.g. Polar NRZ, Unipolar RZ,
Manchester, etc.
• The code is then impressed on a carrier by using a conventional
modulation technique.
• For digital signalling, modulation is the switching (keying) of a
carrier waveform parameter (amplitude, phase or frequency)
between preset levels, whose values are discrete.
• This impresses the code, and therefore the information, on the
carrier.
5. Two types of digital signalling
Digital signalling can be
1. Binary (ASK, BPSK, FSK)
The digital information is transmitted a bit at a time
2. Multilevel (QAM, Quardrature PSK, M-ary PSK)
Several bits are grouped together too form symbols, and then symbols are
modulated and then transmitted as one unit.
The primary performance issues in digital transmission:
• Optimal transmitter and receiver design,
• Minimising average probability of symbol error,
• spectral properties, bandwidth occupied by a modulation scheme
• An important property of any modulation scheme is its spectral
characteristic. This determines the bandwidth required for
transmission.
6. Binary Digital Signalling
Amplitude-Shift Keying (On-Off Keying)
• Switching the amplitude of the carrier signal
between two discrete levels.
• e.g. switching (keying) a carrier sinusoid "on" and
"off" with a unipolar binary signal
• The ASK signal is represented by
s ( t ) = Ac m( t ) cos( ω c t )
• m(t) is the unipolar baseband data signal.
• Ac is the amplitude of carrier.
• ωc is the angular frequency of the carrier.
7. • The spectrum of ASK signal, S(f), can be
found from the Fourier transform
∞
• S ( f ) = ∫ A m( t ) cos( ω t )e − j 2πft dt
c c
−∞
∞ A
= ∫ c
m( t ) e − j 2π ( f − f c )t + e − j 2π ( f + f c )t dt
−∞ 2
Ac
= (M ( f − f c ) + M ( f + f c ))
2
• Note: the bandwidth required to transmit
the ASK s(t) is twice the bandwidth of the
modulating signal m(t).
i.e. BT=2B
9. Detection of ASK
• ASK can be generated and detected in the same fashion as AM.
• ASK may be detected by coherent or noncoherent approaches.
10. Frequency-Shift Keying (FSK)
• Switching the frequency of the carrier
signal between discrete levels.
• In FSK, each discrete level of a code is
represented by a specific frequency.
• e.g. A binary code with two levels is
represented by two discrete frequencies.
11. Frequency-Shift Keying (FSK)
• In the time domain, the FSK signal is
represented by
⎡ t
⎤
s (t ) = Ac cos ⎢ωc t + D f ∫ m(t )dt ⎥
⎣ −∞ ⎦
m(t) is the baseband data signal.
Ac is the amplitude of the carrier.
Df is the frequency deviation [rad./volt/sec].
13. Detection of FSK
• FSK can be detected by either coherent or
incoherent detection
14. Binary Phase-Shift Keying (BPSK)
• Switching the phase of the carrier signal
between two discrete levels. Usually the two
levels differ by 180º.
• The BPSK signal is represented by
[
s ( t ) = Ac cos ω c t + D p m( t ) ]
m(t) is the baseband data signal.
Ac is the amplitude of the carrier.
Dp = is the peak phase deviation [rad./volt].
15. Binary Phase-Shift Keying (BPSK)
ref Couch pg 343
• let m(t) a polar signal with peak values of ± 1 and rectangular pulse
shape. Then
( ) ( )
s ( t ) = Ac cos D p m( t ) cos( ω c t ) − Ac sin D p m( t ) sin( ω c t )
= Ac cos( D ) cos( ω t ) − A
p c c ( )
sin D p m( t ) sin( ω c t )
Since cosine is an even function.
– The first term is called the pilot carrier term which does not
carry any useful information --- power wasted!
– The second term is the data term carrying the coded message.
– The peak phase deviation Dp determines the ratio of the data to
the pilot term.
16. Optimal BPSK
• To maximise the signalling power efficiency
(large proportion of power is to be carried by the
data term), the pilot term must be minimised, i.e.
Dp = ∆θ = 90º = π/2
• Hence for the optimal BPSK, the signal becomes
s ( t ) = − Ac m( t ) sin( ω c t )
• The transmitted signal phase is switched
between two values, 0, 1800
18. Detection of BPSK
• Coherent (Synchronous) detection must
be used
multiplier
BPSK signal baseband digital signal
LPF
cos ( ω c t)
19. Detection of BPSK
• If a low-level pilot carrier component is
transmitted a PLL can be used to recover
carrier
• Otherwise a Costas loop may be used to
synthesise the carrier reference from this
BPSK-SC signal
– 180º phase ambiguity must be resolved
• Can be accomplished by sending a known test
signal
• or using differential coding
21. Costas phase-locked loop
• Note: m2(t) thus ambiguity for ±1
• Hence loop is just as likely to phase lock
such that the demodulated output is
proportional to – m(t) as it is to m(t)
• Thus we cannot be sure of the polarity of
the output and binary 1’s could be read as
binary 0’s
22. Differential Phase-Shift Keying
(DPSK)
• Motivation of DPSK:
– Remove the 180º phase ambiguity in
BPSK by using differential coding at the
Tx and differential decoding at the Rx.
– When serial data is passed through
many circuits along a communications
channel the waveform is often
unintentionally inverted
• Often occurs during switching between
several data paths
23. Differential Phase-Shift Keying
(DPSK)
• Differential Coding
– In differential coding, an input binary data
sequence {dn} is encoded into differential data
{en} determined by
en = d n ⊕ en −1
where ⊕ is a modulo 2 adder or exclusive OR
gate (XOR) operation
24. Differential Phase-Shift Keying
(DPSK)
• Each digit in the encoded sequence is
obtained by comparing the present input
bit with the past encoded bit
• A binary 1 is encoded if the present input
bit and the past encoded bit are of
opposite state
• A binary 0 is encoded if the states are the
same
25. Differential Phase-Shift Keying
(DPSK)
• At the receiver side, the encoded data {en} is
~
decoded to produce the data {d n } by
~ ~ ~
d n = en ⊕ en −1
The tilde denotes data at the receiver.
• Hence the encoded signal is decoded by
comparing the state of adjacent bits
– If the present received encoded bit has the same
state as the past encoded bit a binary 0 is decoded
– A binary 1 is decoded for opposite states
28. Generation of DPSK
logic network phase-shift keying
DPSK signal
baseband binary data
carrier
one bit delay
29. Detection of DPSK
multiplier
DPSK signal baseband data
LPF
one bit delay
When the baseband data is represented in polar code:
e.g. 1 --- -1v and 0 --- +1v,
the modulo 2 adder logic at the receiver side can be easily
realised using a one-bit delay and a multiplier.
0 = 1 ⊕ 1 +1 = -1 × -1
1 = 1 ⊕ 0 -1 = -1 × +1
1 = 0 ⊕ 1 -1 = +1 × -1
0 = 0 ⊕ 0 +1 = +1 × +1