This routine implements the 8th-order filter, 9 coefficients, because of the symmetry of the coefficient, h (0) = h (8), H1 (1) = h (7), h (2) = h (6), h (3) = h (5), H (4) is a single coefficient in the middle. According to the formula:
Realization diagram:
Derived when the coefficient N is an even number, e.g. N = 4: y (n) = h (0) * {x (0) + x (n-3)} + h (1) * {x (n-1) + x (n-2)}
When the coefficient N is odd, for example, N = 5:
y (n) = h (0) * {x (0) + x (n-1)} + h (1) * {x (n-1) + x (n-3)} + h (2) * x (n-2)
1, with the quantized filter coefficients and generating matlab
After setting the parameters, click "Design Filter" button, "file" - "export", the filter coefficient deriving the Workspace, as shown below:
Run: Num = Num ', the filter coefficients are copied to the file COFFICIENT.dat.
Quantized coefficients: run in matlab quantization.m
2. Description
Generating a sine wave with a matlab program table sin_1MHz_gen.m, change the variable f0 = 1.5e6 may generate waveforms at different frequencies. The number of data of the waveform data stored in the first cycle signal_1m.dat file is stored Fs / Fo molecular ratio of the smallest positive integer, such as Fs = 25MHz, Fo = 0.3MHz, Fs / Fo = 250 / 3 (Fs = 25 / 24MHz), the number of data stored in the waveform for the beginning of the file signal_1m.dat 250 data. Signal_gen0.v respective statements if (i0<50) corresponding to if (i0<250). signal_1m.dat placed under simulation simulation directory
3, the filter multisim simulation
Run matlab, produced by sin_1MHz_gen.m 5MHz (f0 = 5e6) sinusoidal signal, Fs / Fo = 5, the first five data hex_sin_data signal_1m.dat data file stored, if the statement of the respective signal_gen0.v (i0 <50) corresponding to if (i0<5).
FIG following simulation waveform (input and output signals of fir filter):
Run matlab, produced by sin_1MHz_gen.m 1MHz (f0 = 1e6) sinusoidal signal, Fs / Fo = 25, the data hex_sin_data first five data files stored signal_1m.dat, if the statement of the respective signal_gen0.v (i0 <5) corresponding to if (i0<25).
FIG following simulation waveform (input and output signals of fir filter):
This shows that the attenuation functions of FIR band signals.
Part of the code:
// Date: 2012-5-27
// Description: 8-order FIR filter, 2MH passband, stopband 8MHz, band attenuation 80dB, 1dB passband
// Uesedfor
// Taobao:
// E-mail:
[email protected]
// ================================================ ==========================
timescale 1 ns / 1 ns
module fir_filter
(
i_fpga_clk,
i_rst_n,
i_filter_in,
o_filter_out
);
input i_fpga_clk; // 25MHz
input i_rst_n
input signed [7: 0] i_filter_in; // data rate 25Mh
output reg signed [7: 0] o_filter_out; // filtered output
// ================================================ ==============
Order filter coefficients // 8 of 9 coefficients, coefficient symmetry
// ================================================ ==============
wire signed [15: 0] coeff1 = 16'd239;
wire signed [15: 0] coeff2 = 16'd1507;
wire signed [15: 0] coeff3 = 16'd4397;
wire signed [15: 0] coeff4 = 16'd7880;
wire signed [15: 0] coeff5 = 16'd9493;
// ================================================ ===============
// delay chains
// ================================================ ===============
reg signed [7: 0] delay_pipeline1;
reg signed [7: 0] delay_pipeline2;
reg signed [7: 0] delay_pipeline3;
reg signed [7: 0] delay_pipeline4;
reg signed [7: 0] delay_pipeline5;
reg signed [7: 0] delay_pipeline6;
reg signed [7: 0] delay_pipeline7;
reg signed [7: 0] delay_pipeline8;
always @ (posedge i_fpga_clk or negedge i_rst_n)
if (! i_rst_n)
begin
. Delay_pipeline1 .1881 = 8'b0;
. Delay_pipeline2 .1881 = 8'b0;
. Delay_pipeline3 .1881 = 8'b0;
. Delay_pipeline4 .1881 = 8'b0;
. Delay_pipeline5 .1881 = 8'b0;
. Delay_pipeline6 .1881 = 8'b0;
. Delay_pipeline7 .1881 = 8'b0;
. Delay_pipeline8 .1881 = 8'b0;
end
Else
begin
delay_pipeline1 < = i_filter_in, Read more
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