High Speed, Low Power FIR Digital Filter Implementation
Presented by,
Praveen Dongara and Rahul Bhasin
Flow Chart
• Motivation
• Brief Discussion on FIR
• Full Adder Design
• Pipelined Multiplier (8 X 8)
• Pipelined adder (16 X 16)
• Results
• Trouble shooting
Motivation
• FIR - Finite Impulse Response Filter– Fundamental processing unit in DSP systems
• High frequency applications– Video imaging
• Low power applications– Wireless communications
Brief Discussion on FIR Filters
1-N
0i
)( y(n) inxhi
• An N-tap FIR filter can be described by:
Direct Implementation
Tsample TM +
TA
FIR Discussion contd.
• 2-parallel FIR Filter• Parallel Processing• Advantage
– Reduced power consumption
– Or high speed
• Disadvantage– Overhead of area
2-parallel design
Why Pipelined/Parallel ?
• Pipelined to enable higher sampling rates
– Sampling frequency can be increased n-fold if we have n pipeline stages.
• Parallel for low power
Why Pipelined/Parallel? Contd.
f V C L) / (f V )C (L P 2222
- V can be decreased by
- C increases by L (L=2)
- f can be decreased by L
Optimizations at various levels
Improvement Achieved
Levels of design hierarchy
Full Adder
• Dynamic Logic
• True Single Phase Clocking (TSPC)
xorcilxorbiajcy
rxobiajxorbiajSum
...
....
).(. cisicisixor
Full Adder contd.
Pipelined Multiplier
• Baugh-Wooley Algorithm for 8 X 8 multiplication
• 2’s complement numbers
Pipelined Multiplier Floor Plan
• Latency of 12 cycles
• Partial product summing full adder array
• Vector merge adder
• Latch stages to skew the multiplier bits b0-b7
• Deskewing latches for the product bits
Pipelined Multiplier Layout
Pipelined Multiplier contd.
• Example – Input vectors 111111a1 X 0101010b
• If a=1 and b=1 we have the following output sequence.
– 1111111110101011
Pipelined Multiplier contd.
16 X 16 Pipelined Adder
• Latency of 8 cycles
• Triangular array of half adders
• Merging of two half adder rows – Leads to decrease in latency
• Advantage – Regularity of design– Fewer deskewing latches
16 X 16 Pipelined Adder Layout
FIR Filter Layout
Results
Trouble Shooting
• Convergence problems
• Elmore/Penfield analysis requires lot of disk space and time