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Signal Processing Using Digital Technology
Jeremy BarstenJeremy Stockwell
December 10, 2002
Advisors:Dr. Thomas Stewart
Dr. Vinod Prasad
Digital Signal Processor Project Description Preliminary Work
Research Design
Standards and Patents Goals Schedule
Project Description All purpose digital signal processor
using FPGA/VHDL and ASIC/VLSI technology.
Useable for a variety of applications: Audio and Video Cellular Technology
Adapted depending on the application.
Project Description High-level Block Diagram:
Input ProcessedSignal Signal
DIGITALSIGNAL
PROCESSOR
Filter Design Manipulating a digital input
utilizing multipliers and adders. Direct Form II realization of an IIR
Filter: X(n) w(n) b0 y(n)
-a1 b1
-a2 b2 w(n-1)
w(n-2)
Z-1
Z-1
Signal Converters Each signal will be analog in
nature. Requires an analog-to-digital
converter at the input stage and a digital-to-analog converter at the output stage.
Type of converter will be determined later.
Adder and Multiplier Any basic signal processor consists
of different stages of addition and multiplication.
A n-bit by n-bit multiplication will take place and result in a 2*n-bit value.
This answer will be added to previous values stored in a data register (discussed later).
Adder and Multiplier Cellular Multiplication:
a3 a2 a1 a0
b0
b1
b2
b3
p7 p6 p5 p4 p3 p2 p1 p0
Adder and Multiplier For 2’s compliment addition and
multiplication:
Cellular Array
2’s Complement Block
2’s
B
L
O
C
K
Adder and Multiplier
x(n)-a1*w(n-1)
-a1 -a2
w(n-1) w(n-2)
x(n)
x(n)-a1*w(n-1)
Shows the consecutive steps in the addition, multiplication, and data management.
16-Bit Multiplier
32-bit Adder/Subtractor
Memory Management
16-Bit Multiplier
Memory Management
32-bit Adder/Subtractor
Data Management Need to store old calculated values
for later use. Need a “shift-and-store” type of
data management. Will deliver the correct data at the
appropriate time.
Data Management The possibility of overflow exists in
the addition and multiplication stage. For this reason, a truncation circuit is
needed to control and adjust the value of the adder/multiplier circuit.
Will also use truncation before sending out the final signal.
Preliminary Work Investigation of Xilinx compiler. Ripple carry adder v. Carry
look ahead adder. Parallel multiplier v. Serial
multiplier.
* 16-bit ripple carry adder will have 34 gate delays
Ripple Carry AdderRipple Carry Adder
CLA Adder
* 16-bit CLA adder will have 10 gate delays
Xilinx Implementation Implemented both adders using VHDL. Created simple adder in VHDL (a+b=c). Compared results to see what type of adder
was created by the compiler. Results:
CLA AdderRipple Adder
Simple Adder
Delay 11.05 ns 22.43 ns 11.05ns
Checked results using FPGA board.
Multiplier Advantages and disadvantages
of using a parallel multiplier v. a serial multiplier.
Investigate the feasibility of using a Parallel Multiplier.
Speed v. Area
Signed Serial Multiplier For a signed serial multiplier, it is
necessary to sign extend. For Example (-3 x 5):
1101(-3) x 0101(+5)
11111101 0000000 111101
+ 00000 11110001(-15)
Signed Serial Multiplier
Sign ExtensionSign Extension
Shift RegisterShift RegisterShift RegisterShift Register
Adder/SubtractorAdder/Subtractor
RegisterRegister
A B
Product
Area v. Speed Implemented Serial adder and
simple AxB adder in VHDL.
Area Delay Area Delay Area Delay
Serial Multiplier 7.14% 96.88ns 13.52% 210.8ns 24.49% 503.68ns
Parallel Multiplier 10.71% 27.41ns 28% 38.76ns 107.40% 51.06ns
Area v. Delay (serial)Area v. Delay
7.00%
9.00%
11.00%
13.00%
15.00%
17.00%
19.00%
21.00%
23.00%
25.00%
27.00%
96 146 196 246 296 346 396 446 496 546
Delay(ns)
Are
a
Area v. Delay (parallel)Area v. Delay
10.00%
30.00%
50.00%
70.00%
90.00%
110.00%
130.00%
27 32 37 42 47 52 57
Delay(ns)
Are
a
Other Multiplier Options It is possible to use a combination
of parallel and serial multipliers. For example it is possible to use
two 8-bit parallel multipliers in series which will double the delay but will save space.
Standards and Patents Searched the Internet for
standards and patents on digital signal processors.
Many of the standards were application specific.
Could not really find specific standards on digital signal processors.
Hardware and Software Programs
Xilinx Foundation Software Leonardo Spectrum L-Edit Pro v8.2 PSpice Circuit Simulation Xilinx XC4005ePC84 FPGA Board A/D and D/A converters
Project Goals Determine best trade-off between size
and speed for the adder/multiplier circuit.
VLSI implementation of a 4-bit adder and multiplier.
Determine the number of bits used in our processor to ensure stability.
Complete data management and truncation block of the processor.
Decide on specific application.
Project Schedule January/February:
Complete adder/multiplier in VHDL and implement on the FPGA board.
Complete VLSI design of adder/multiplier circuit. March:
Determine specific application and design the appropriate filter. April:
Complete data management and truncation block. Implement entire design on FPGA board and troubleshoot any
errors that arise. May:
Prepare final presentation and possibly present at Student Expo.
Signal Processing Using Digital Technology
Jeremy BarstenJeremy Stockwell
December 10, 2002
Advisors:Dr. Thomas Stewart
Dr. Vinod Prasad