SSB_PPT.pptx

©M. S. Ramaiah University of Applied Sciences
1
Mini Project Work
B-TECH ECE

2
Name :- Samanwaya Das
Registration Number:- 17ETEC004097

3
Title of the Project
VHDL Implementation Of Efficient SSB Modulator Using
Differential Phase Shifter
• Supervisor
Supervisor : Dr. D. Punithavathi
• Place of Work : M S Ramaiah University of Applied Sciences

4
Outline
• Introduction
• Title and Aim
• Block Diagram or Concept
• Objectives
• Methodology
• Filter Coefficients
• Filter Characteristics
• MATLAB implementation
• VHDL implementation
• Single side spectrum of conventional method
• Single side spectrum of dual filter method
• Observation and results
• References

5
Introduction
• Many DSP applications require conversion of real valued signal into an
analytical signal. This requires SSB modulation schemes to generate
modulated signal (audio processing applications).
• SSB modulation is a type of AM modulation, wherein only one of the side
bands either USB or LSB is transmitted.
• SSB eliminates one of the sideband saving bandwidth and power, thus
making it one of the most efficient modes of signal transmission. This
features necessitates a requirement of SSB modulation scheme.
• Existing SSB modulation schemes are i)Frequency discrimination method
ii) Phase discrimination method (Hartley Modulator) iii) Weavers method

6
Introduction to Phase Discrimination Method
• Project based on “Phase discrimination” uses filtering method,
which gives 90 degree phase shift for various frequency ranges.
• Hilbert transformer is widely used 90 degree phase shifter.
Practically it cannot be designed to give exactly unity gain, over its
ranges of pass band. This can cause, phase and amplitude
mismatches while generating analytical signal. “Fig 1” shows the
frequency response of Hilbert filter used in Ref[3].

7
Hilbert Transform using FIR filter
Fig. 1 Frequency response of Hilbert filter
used in Ref[3]. Inset shows the ripples in
the passband.

8
Introduction to VHDL
• Use of Very high-speed integrated circuit Hardware Description
Language (VHDL) code allows for several different points of
customization to this application based on needs and desired
accuracy. VHDL also allows for quick re-design based on changing
requirements.
• VHDL ensures the use of this code for many years. Because of this,
many years from now this code will be able to be used and
modified to fit current application needs.
• FPGA, implementation possible which allows the physical
realization of the architecture. Further FPGA allows for architecture
prototyping, which can be developed into ASIC chip. ASIC chip, can
be mass produced to cater the needs of the market.

9
Title
VHDL Implementation of efficient SSB Modulator using
Differential Phase Shifter
Aim
To design a differential phase shifter for the efficient SSB
Modulator and to implement it using VHDL

10
General SSB Block Diagram
Fig.2:Block diagram of conventional
method of generating SSB

11
Proposed SSB Block diagram
Fig 3: block diagram of proposed SSB
modulation

12
Objectives
• To study SSB modulation and the phasing method used in the generation
of SSB modulated wave with its spectrum.
• To design the FIR filter for the proposed SSB method.
• To implement the conventional methodology and proposed
methodology of SSB in MATLAB.
• To implement the conventional methodology and proposed
methodology using VHDL.
• To analyze and compare the performance of proposed method with the
conventional by applying a message signal

13
The implementation of conventional and proposed architecture is
done using MATLAB and Xilinx’s Vivado(VHDL).
MATLAB IMPLEMENTATION:
• We have 2 types of filters used in this project, Hilbert filter and +45
and -45 degree low pass FIR filters. Filter coefficients of Hilbert filter
(Ref[2]) and low pass FIR filter(Ref[1]) are obtained using MATLAB.
• Using these coefficients the architectures are simulated in MATLAB
and corresponding waveforms and phase lag is obtained.
• The resultant frequency spectrums are obtained using MATLAB and
the corresponding suppressions are calculated.
Methodology

14
Methodology
VHDL implementation(using Xilinx’s Vivado):
• IP cores and the clocks required for the designing of conventional
and proposed architecture are generated using Xilinx’s Vivado. Port
mapping is done to map the ports with the corresponding inputs.
• Required input signals are provided to the generated IP’s with the
help of counters, the resultant RTL schematic is obtained and the
wave forms are generated.
• The output text of Xilinx’s Vivado is imported to MATLAB and then
simulated in MATLAB to obtain corresponding frequency
spectrums.
• The resultant suppressions are calculated.

15
15
Hilbert Filter Coefficients
Coefficients H
-0.003098750403898756 A(0)
-0.020135571740449009 A(1)
-0.020939191991494636 A(2)
-0.000202907720244840 A(3)
0.026952793338152693 A(4)
0.034346295140573725 A(5)
0.007402212025804578 A(6)
-0.038808195575967708 A(7)
-0.063568924468410643 A(8)
-0.027845568148826612 A(9)
0.073581669737100258 A(10)
0.200516197928349321 A(11)
0.288205417056360269 A(12)
0.288205417056360269 A(13)
0.200516197928349321 A(14)
0.073581669737100258 A(15)
-0.027845568148826612 A(16)
-0.063568924468410643 A(17)
-0.038808195575967708 A(18)
0.007402212025804578 A(19)
0.034346295140573725 A(20)
0.026952793338152693 A(21)
-0.000202907720244840 A(22)
-0.020939191991494636 A(23)
-0.020135571740449009 A(24)
-0.003098750403898756 A(25)
-0.003098750403898756 A(26)
generated by using a raised cosine window.
Filter order:27. To generate the coefficients of the Hilbert transform filter a program is
used is Iowa Hills Hilbert Filter Designer). The filter coefficients have been generated by
using a raised cosine window. passband range 0.00 to 0.35rad/sec, fs = 49Khz.

16
16
Dual Filter Coefficients
Filter coefficients A
0.0000 A(0)
-0.0000 A(1)
-0.0000 A(2)
-0.0103 A(3)
-0.0000 A(4)
-0.0336 A(5)
0 A(6)
-0.0613 A(7)
0.0000 A(8)
-0.0685 A(9)
-0.0000 A(10)
-0.0000 A(11)
0.0000 A(12)
0.7466 A(13)
0 A(14)
-0.3952 A(15)
0 A(16)
-0.1540 A(17)
0.0000 A(18)
-0.0507 A(19)
0.0000 A(20)
0.0000 A(21)
0.0000 A(22)
0.0149 A(23)
0.0000 A(24)
0.0109 A(25)
0 A(26)
0.0032 A(27)
Filter A coefficients:
Filter order :26.The coefficients are generated by MATLAB code written by C. S. Tuner
Ref[1].the specification used in the MATLAB code are 𝜔1 = 0.05𝑟𝑎𝑑/𝑠𝑒𝑐 𝜔2 =
0.45𝑟𝑎𝑑/𝑠𝑒𝑐 𝑎𝑛𝑑 𝑎 = 0.05rad/sec , passband range 0.1 to 0.4rad/sec. fs = 49Khz.

17
17
Filter Coefficients
Filter coefficients B
0.0000 B(27)
-0.0000 B(26)
-0.0000 B(25)
-0.0103 B(24)
-0.0000 B(23)
-0.0336 B(22)
0 B(21)
-0.0613 B(20)
0.0000 B(19)
-0.0685 B(18)
-0.0000 B(17)
-0.0000 B(16)
0.0000 B(15)
0.7466 B(14)
0 B(13)
-0.3952 B(12)
0 B(11)
-0.1540 B(10)
0.0000 B(9)
-0.0507 B(8)
0.0000 B(7)
0.0000 B(6)
0.0000 B(5)
0.0149 B(4)
0.0000 B(3)
0.0109 B(2)
0 B(1)
0.0032 B(0)
Filter B coefficients:

18
18
Hilbert Filter Characteristics
• The magnitude and phase response of the conventional Hilbert-FIR
filter, using MATLAB.
Fig 4: filter characteristics of Hilbert FIR filter

19
Hilbert Filter Characteristics
• The passband of Hilbert FIR has, passband ripples as shown in the figure.
Fig 5: ripples in passband of Hilbert filter

20
20
Dual Shifter FIR Filter Characteristics
• The magnitude and phase response of +45 degree filter, using
MATLAB
Fig 6: filter characteristics of +45 degree filter

21
21
Dual Shifter FIR Filter Characteristics
• The magnitude and phase response of -45 degree filter, using
MATLAB
Fig 7: filter characteristics of -45 degree filter

22
22
Dual shifter FIR Filter Characteristics conclusions
• The figures in slide 20 and 21 signifies, the characteristics of +45/-
45-degree dual filter. Upon, close observation and superimposing
the phase response we would observe a net phase difference of 90
degree throughout the band.
• These filters, have identical magnitude spectrum which essentially
gives identical magnitude at the end of the 2 filter stages.

23
MATLAB IMPLEMENTATION
• For implementation consider the message signal of 1kHz and carrier
signal of 5kHz for ease of plotting and representation
1.Conventional method:
Fig 8: output of the Hilbert transform and message signal
To find the phase difference between the two-signal, fast Fourier transform
(fft) . It can be observed that the magnitude of the two filters are different
and with a phase shift obtained to be of 91.0486 degrees(MATLAB).

24
• The above graph shows the separation between two side band in
dB scale. The suppression is around 19 dB between lower and
upper side band.
Fig 9: single side spectrum of conventional
method MATLAB implementation

25
• 2. Dual filter method:
Fig 10: dual filter output
• The above graph shows output of the two filters , we can observe
that the amplitude for the two filters are same and with a phase
shift obtained to be of 90.8679 degrees(MATLAB).

26
26
Fig 11: single side spectrum of dual filter
• The above graph shows the separation between two side band is
27dB.

27
VHDL IMPLEMENTATION
• The implementation of the hardware-based simulation is done using
VHDL. For the simulation Xilinx’s Vivado design suite is chosen.
• IP cores have to be used to implement the architecture in Vivado,
• Before, describing the IP cores, the clocking scheme provided to the
architecture should be provide .
• The clocking scheme provided is LVDS(low voltage differential)
• The LVDS operates at low power and can run at high speeds
• we use 2 voltage levels this can be specified as 200 Mhz_p and 200
Mhz_n. This, essentially signifies the default clock of 200 Mhz can be
scaled down for our requirement

28
1.MMCM (Mixed mode Clock manager)
• The system clock default is 200 Mhz, from 200
Mhz it is required to downconvert to 49 Khz
• The first step converting the 200 Mhz to
intermediate frequency greater than
5Mhz.Using use the clocking wizard ip, in which
MMCM mode is used. 9.8 Mhz is chosen as the
frequency to down convert as it satisfies, the
condition of being greater than 5Mhz
• Next stage using a counter to convert 9.8 Mhz
to 49 Khz. The counter is set for 200 rounds,
after every 200 rounds it toggles. (9.8 Mhz /
200) = 49Khz, this is used to create the clock
frequency of 49 Khz. 49Khz is clocking
frequency, thus matching it with the sampling
frequency.
Fig 12: ip symbol of MMCM

29
2.DDS COMPILER: to generate message signal
• The generation of message signal is
done by the DDS compiler ip of Xilinx’s
repository.
• Message signal is that signal, which
essentially is from end users. These are
the signals, which are given as input
from the user and received by another
user
• The message signal is a small 1Khz signal.
• provision is given to use both cosine and
sine as a message signal. However, the
one chosen is sine. The output is sliced
into 16 bits, for each sine and cosine.
Fig 13: ip symbol of DDS complier
to generate message signal

30
3.DDS COMPILER: to generate carrier signal
• For generating carrier signal we use DDS
complier to generate a carrier frequency
of 5Khz
• Both sine and cosine are required for
carrier signal
• The output is given 16 bits for sine and
cosine each
• The same architecture of DDS complier for
generating message and carrier signal is
used both in Hartley architecture and the
proposed methodology
Fig 14: ip symbol of DDS complier to
generate carrier signal

31
4.MULTIPLIER
• The signals out of Hilbert and dual filter
have to be multiplied with the carrier signal
,here the multiplier is used.
• The total number of multiplier used is 4. 2
for conventional and 2 for the proposed
methodology. One of the ports of multiplier
is carrier frequency of 5Khz is given(port A)
and though one of the other ports message
of 1 Khz (port B )passing through the Hilbert
or only message or dual filter is given. Both
the ports multiply 16 bits of data, to give 32
bits of output(port P).
Fig 15: ip symbol of multiplier

32
5.FIR COMPILER : HILBERT TRANSFORM FILTER
• The Hilbert transform is a filter gives
a phase shift 90 degree. This forms
the essential part of Hartley
architecture to generate the SSB.
• The input given is the message
signal of 16 bits, and an output of 16
bit is provided for further stages.
• 1 ip have been used to implement .
Fig 16: ip symbol of Hilbert filter

33
6.FIR COMPILER : DUAL FILTER
• The 45-degree dual filters takes the
message signal, and shifting the signals
by a phase of - 45 and +45 which is
provided at the output.
• The input is 16 bit message data and
provides 16 bit output data for further
process.
• 2 separate Ip’s have been used to
implement the 2 dual filters
Fig 17: ip symbol of dual filter

34
7.FIR COMPILER : LOW PASS FILTER
• FIR compiler for low pass filter is used
to removing few harmonics at the
output after generating the SSB for dual
filter method.
• The final output produced, has many
harmonics of the resultant signal. A few
of the high frequency harmonics are
attenuated to view SSB spectrum
clearly.
• The IP integration and behavioural
model is written using VHDL.
• After writing the VHDL code, the project
is synthesized and then then elaborated
to generate RTL
Fig 18: ip symbol of low pass
filter

35
8.RTL SCHEMATIC
Fig 19: RTL schematic

36
Single Sided Spectrum of Conventional SSB (VHDL)
Fig 20:single side spectrum of VHDL
implementation of conventional method

37
Single Sided Spectrum of Dual Filter based SSB
(VHDL)
Fig 21:single side spectrum of VHDL
implementation of dual filter method

38
OBSERVATION AND RESULTS
HILBERT ARCHITECTURE DUAL FILTER
MATLAB
Filter coefficients are generated using a
program for designing FIR Hilbert filter
Filter coefficients are generated by writing a
MATLAB code.
The number of coefficients is 27 The number of coefficients is 28
Single filter is used Two filters are used (+45 and -45 degree)
Phase difference between the message
signal when passed to Hilbert filter and
without filter is 91.0486 degree
Phase difference between the message signal
when passed to +45 filter and -45 filter is -
90.8679degree
Obtaining the SSB magnitude spectrum,
magnitude suppression of the side band is
found out around 19dB
Obtaining the SSB magnitude spectrum,
magnitude suppression of the side band is
found out around 27dB (8dB improvement)
VHDL
The suppression between upper and
lower sideband is about 11 dB
The suppression between upper and lower
sideband is about 17 dB (6dB improvement)

39
Conclusions
• The spectrum obtained contains, various harmonics and noise
element. However, we can clearly demarcate the SSB sidebands
obtained.
• For conventional method, we get around 11dB suppression
between the upper and lower side bands.
• For dual shifter method, we get around 17dB suppression between
the upper and lower side bands.
• The difference between the obtained spectrum using VHDL and
MATLAB simulation, can be attributed to the ideal nature of
MATLAB simulation, delays associated with various register
elements, and noise susceptibility in final VHDL architecture.
• We can overall conclude that the upper and lower side band
suppressions is much better in, the proposed dual shifter
methodology. Which is, approximately 17 dB vs 11dB.

40
LINK FOR VIDEO OF VHDL
SIMULATION OF ARCHITECTURES
• Link : -
https://drive.google.com/file/d/1Gx0ELaVcmUHOOkoK0JGxCSjvqZoVrsx_/view?u
sp=sharing

41
References
1. C.S. Turner, ”An efficient analytic signal generator”, Signal Processing Magazine, vol. 23, no. 4,
pp. 91-94, July 2009.
2. IOWA hills Hilbert filter designer
3. A. Reilly, G. Frazer and B. Boashash, ”Analytic signal generation-tips and traps,” in IEEE
Transactions on Signal Processing, vol. 42, no. 11, pp. 3241-3245, Nov 1994.
4. P. Duraiswamy, J. Bauwelinck, J. Vandewege, ”Efficient implementation of 90◦ phase shifter in
FPGA”, EURASIP Journal on Advances in Signal Processing, vol. 2011, pp. 32-32, 2011
5. D. Shi and Y. J. Yu, Design of linear phase FIR filters with high probability of achieving minimum
number of adders, IEEE Trans. Circuits Syst. I, Reg. Papers, vol. 58, no. 1, pp. 126-136, Jan.
2011.
6. Y. J. Yu and Y. C. Lim, optimization of linear phase FIR filters in dynamically expanding sub-
expressions space, Circuits, Syst., Signal Process., vol. 29. no. 1, pp. 65-80, 2010.
6. Douglas Perry, VHDL: Programming by Example Hardcover – Import, 16 Jul 2002
7. Patel / Mitta, Programming in MATLAB ®: A problem-solving approach – 2014
8. B.P. Lathi , Modern Digital and Analog Communication Systems – 2011
.

42
THANK YOU

SSB_PPT.pptx

Recommended

Recommended

More Related Content

Similar to SSB_PPT.pptx

Similar to SSB_PPT.pptx (20)

Recently uploaded

Recently uploaded (20)

SSB_PPT.pptx