 Open Access
 Total Downloads : 16
 Authors : Srinath R, Ms. Kousalya R
 Paper ID : IJERTCONV4IS14035
 Volume & Issue : NCSPC – 2016 (Volume 4 – Issue 14)
 Published (First Online): 30072018
 ISSN (Online) : 22780181
 Publisher Name : IJERT
 License: This work is licensed under a Creative Commons Attribution 4.0 International License
An Efficient Constant Multiplier Architecture for Reconfigurable Fir Filter Synthesis
Srinath R Ms. Kousalya R
Master of Engineering in Applied Electronics Assistant Professor, Department of ECE,
Sri Venkateswara College of Engineering, Sri Venkateswara College of Engineering, Sriperumbudur602117 Sriperumbudur602117
Abstract: This paper proposes a reconfigurable finite impulse response (FIR) filter using constant multiplier algorithm with applying pipeline technique. To design a high performance Reconfigurable fir filter, according to the proposed constant multiplier algorithm with Retiming pipelining method has been applied in coefficient generator block. This method capable of reducing the switching activity of constant multiplier process by 28% as compared to that of existing method. In this technique area and delay can be reduced approximately 24% and 62% respectively compare to previous method. This reconfigurable fir filter can be designed using Verilog hardware Description Language (HDL) and its behaviour can be tested using Modelsim 6.3c software and synthesized in Xilinx10.1.
Keyword: Reconfigurable finite impulse response (FIR),Verilog, pipelining, Xilinx.

INTRODUCTION
Fir Filter is important component in any video processing, audio processing, Digital signal processing (DSP) and any bio medical application. Mostly these systems need some process from reconfigurable Fir Filter. This reconfigurable Fir filter commonly work with dynamically configurable filter coefficient and length and factor of interpolation which can change according to the given specification of different input standards in a computing platform.
In any Fir filter, the multiplier architecture is very important because to analysis of performance of any fir filter is mostly depends on that multiplier. In general direct form fir filter, the multiplication function between one input variable (Xin), and more constant variable like h0, p, p coefficients. It is called Multiple Constant Method (MCM). In this paper we have to apply Retiming pipelining cell concept in multiplier block in reconfigurable fir filter.

RECONFIGURABLE FIR FILTER USING CONSTANT MULTIPLIER
Reconfigurable fir filter is evaluated from direct form fir filter. In this paper to design the reconfigurable fir filter using constant multiplier algorithm with retiming pipelining cell. Retiming pipelining cell is used to reduce usage of clock period. There are two ways to apply retiming concept in fir filter. First one is retiming pipeline cell placed in after the multiplier block in fir filter. The multiplier block performs multiplication operation between input X and H. Another one is cut set retiming cell placed
in between each and every two tap block in fir filter. Here I am using retiming pipeline cell in reconfigurable fir filter. Here the fir filter contains sample data generator, co efficient data generator, common branch filter, and accumulator [1][2].

SAMPLE DATA GENERATOR
The Sample Data generator block contains some parameter like main clock source, reset signal, RRCin signal, interpolation selector (Intp_sel).this data generator block used to generate sample data based on value of interpolation factor, master clock and reset signal. Output of the data generator block is passed to next block.

COEFFICIENT DATA GENERATOR
The two phase optimization technique is used to reduce the hardware usage of implementing reconfigurable fir filter with minimum time computation and design complexity also will be low. The coded coefficient generator block is performing the multiplication operation between x and h. The h values are directly applied in look up tables. To find the size of input data is 16 bit and the coefficient data is 17 bit and provide output data is 16 bit long[1]. The co efficient data generator block consists of important modules such as sign conversion block, partial product generator, and eight multiplexer units , control logic generator, controlled addition layer two and three and final addition layer. The data flow diagram of coefficient data generator block is shown in Fig.1.
Fig.1. data flow diagram of coefficient generator block

FIRST CODING PASS BLOCK
The First Coding Pass unit is providing initial process of coefficient generator. The coefficient value is passed to the first coding pass and its performing in parallel for three different interpolation factors. The first coding pass block is designed by using 2:1 multiplexer circuit. Here vertically to matching operation between two different coded values in same size. Block diagram of Fir Coding Pass is shown in Fig.3.
Fig.2. block diagram reconfigurable fir filter
Fig.3. Block diagram of First Coding Pass

SECOND CODING PASS BLOCK
The second coding pass unit is get the input data from 3 set of coded value in first coding pass block. The block diagram of second coding pass is shown in Fig.4. In this block perform vertically in between these three set of coded coefficient value.
Fig.4. Block diagram of Second Coding Pass

SIGN CONVERSION BLOCK
The sign conversion block is used to analysis sign magnitude condition in given coefficient value. The sign conversion block diagram is shown in Fig.5. The sign conversion block gets 17 bit coded coefficient value from second coding passing block.
The most significant bit of coded coefficient value is equal to 0 means 16 bit coded coefficient values are passed to the output port else 16 bit inverted coded coefficient values are passed to the output port.
Fig.5.Architecture of the Sign Conversion Block

PARTIAL PRODUCT GENERATOR BLOCK
Constant Shift and addition method is used to get the partial product during the multiplication operation between the input data (Xin) and the filter coefficients. In BCSE technique, realizations of the common sub expression using constant shift and add method remove the common term present in a coefficient[1][3]. The block diagram of partial product generator shown in below Fig.6.
Fig.6. Block diagram of partial product generator


EXISTING BCSE BASED RECONFIGURABLE
FIR FILTER
The multiplexer unit is used to select the appropriate data generated from the parial product generator block based on the coefficient's bit stream. At layer1, eight 4:1 multiplexers are required to produce the partial products according to the two bit BCSE algorithm applied vertically on the MAT. The widths of these 8 multiplexers are 17, 15,
13, 11, 9, 7, 5, and 3bit each instead of 16bit for all, which would reduce the hardware and power consumption. The block diagram of the multiplexers unit is shown in Fig.7.
Fig.7. Block diagram of BCSE based reconfigurable fir filter

PROPOSED BCSE BASED RECONFIGURABLE FIR FILTER WITH RETIMING PIPELINE CELL
The proposed method of binary common subexpression based reconfigurable finite impulse response filter with retiming pipeline cell. The retiming pipeline cell is used reduce critical path delay and also either to increase virtual clock speed, sample time period, or to decrease power consumption at constant speed used on direct form fir filter. Here we have designed 16 bit retiming pipelining cell using data flipflop[5][6].
Generally retiming pipeline cell method applied in between multiplier and adder block in fir filter. This 16 bit retiming pipelining cell applied in reconfigurable constant multiplier architecture. Finally we have to reduce area and also reduce the propagation dlay of reconfigurable fir filter. The block diagram proposed reconfigurable constant multiplier architecture with retiming pipelining cell is shown in Fig.8.
Fig.8. Block diagram of BCSE based reconfigurable fir filter with retiming pipelining cell

CONTROL LOGIC GENERATOR (CL) BLOCK Control logic generator block takes the multiplexed coefficient (H [15:0]) as its input and groups into one of 4
bit each (H [15:12], H [11:8], H [7:4], and H [3:0]) and
another of 8bit each (H [15:8], H [7:0]).
Fig.9. Block diagram of Control Logic (CL) Generator

MULTIPLEXERS UNIT
The Multiplexer unit will be used to select the proper data generated from the partial product generator unit which will depend upon the coefficients of the binary value. At layer1, eight 4:1 multiplexers are needed to produce the partial products according to the 2bit BCSE algorithm. The width of these 8 multiplexers are 17, 15, 13, 11, 9, 7, 5 and 3bit each instead of 16 bit for all partial products, which will reduce the power and hardware consumption[1][2].

CONTROLLED ADDITION AT LAYER 2
The architecture of controlled addition at layer2 is shown in Fig.10. The partial product generator block this generates from eight set of 2bit coded coefficients are added to the final result of multiplication operation in three different addition layers.
Fig.10. Architectural details of the controlled addition at layer2 block.

CONTROLLED ADDITION AT LAYER3
The architecture of controlled addition at layer3 get the input data from output of four sum result in architecture of controlled addition at layer2[1][4]. The block diagram controlled addition at layer3 is shown in Fig.11.
Fig.11. Architecture of the controlled addition at layer3.

CONTROLLED ADDITION AT LAYER4
The controlled addition at layer4 which performs 16 bit addition operation between two 16 bit data from addition at layer3.

RETIMING PIPELINING CELL BLOCK
This is final block of reconfigurable constant multiplier architecture. Here we have to design 16 bit retiming pipeline cell register using data flip flop. In this retiming
pipelining method used reduce critical path delay and also reduce the number of register in this design.

COMMON BRANCH FILTER
The CS block is used to steer proper data to the final accumulation block depending on the corresponding value of interpolation factor parameter. It takes the input from the CG block.
Fig.12. Block diagram of Coefficient Selector

ACCUMULATION UNIT BLOCK (FA)
The final accumulation block has a chain of six adders and six registers as there is seven sub filters.
Fig.13. Block Diagram of Accumulation unit


SIMULATION RESULT
Fig.14. simulation output of BCSE Final Block

TABLE 1 PERFORMANCE COMPARISON BETWEEN TWO DIFFERENT METHOD OF RECONFIGURABLE FIR
FILTER

CONCULSION
Finally we have design reconfigurable fir filter using constant multiplier algorithm with retiming pipelining register through Verilog hardware description language and simulated successfully in Modelsim 6.3c. After that synthesized in Xilinx software, here to analysis usage of hardware computation and propagation delay of fir filter. The proposed method area and delay has been reduced compared to existing method. Both design are synthesized in Xilinx FPGA (field programmable gate array) and verified successfully.
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FPGA Spartan3e Xc3s250 PQ208 
SLICE 
LUT 
DELAY 
BCSE fir Filter 
1367 
2605 
15.346(ns) 
BCSE fir filter using Retiming 
1269 
2029 
2.313(ns) 