Using Altera's Cyclone series of EP1C6Q240C8 chip, designed a 32-order FIR filter system of variable parameters, compiled on-chip logic cells occupy 75% of occupied RAM 71%. Using the signal generator produces a variety of input signals, the computer according to the given filter indicators derive the first-order factor, and then FPGA configuration; FPGA and then filtered the data uploaded to the computer display.
Specific experiments and analyzed as follows:
(1) filter indicators: Window function for Kaiser window, β = 3.4, sampling frequency of 187.5kHz, cut-off frequency of 35kHz, filter amplitude-frequency characteristic and phase-frequency characteristic as shown in Figure 13; input signal is 1.5kHz, and 10kHz sine wave mixed-signal, oscilloscope signal in Figure 14 a) shows, the filtered signal in Figure 14 b) below. From Figure 14 b) can be seen, since the low-pass filter cutoff frequency of 35kHz, the input of the mixed-signal frequency are lower than 35kHz, so the filtered signal waveform has not changed.
(2) filter indicators and (1) the same input signal is 1.5kHz and 50kHz sine wave mixed-signal, oscilloscope signal in Figure 15 a) shows, the filtered signal in Figure 15b) as shown. The results can be seen that the low-pass filter cutoff frequency of 50kHz would be greater than the sine wave signal filtered out, the basic retained 1.5kHz sine wave signal.(3) filter indicators: window function is Hamming window, the sampling frequency of 187.5kHz, cut-off frequency of 5kHz, filter characteristics as shown in Figure 16; input signal is 1kHz sine wave and white noise mixed-signal, oscilloscope signal shown in Figure 17 a) shows, the filtered signal in Figure 17 b) below. After the results can be seen from the filter, filter to filter out a lot of white noise, basically resumed 1kHz sine wave signal.
(4) filter indicators: Window function for Kaiser window, β = 3.4, sampling frequency of 187.5kHz, pass-band frequency 10kHz ~ 15kHz, filter characteristics as shown in Figure 18; input signal is 27kHz, and 10kHz sine wave mixed-signal , oscilloscope signal in Figure 19 a) shows, the filtered data shown in Figure 19 b) below. Through the filtered image can be seen that the band-pass filter will be outside the pass-band frequency 27kHz sine wave signal filtered out, and basically restored 10kHz sine wave signal.
(5) filter indicators: Filter indicator and (4) the same; input signal is 1kHz and 10kHz sine wave mixed-signal, oscilloscope signal in Figure 20 a) below. After filtering the data shown in Figure 20 b) below. Through Figure 20 b) can be seen that the band-pass filter will be lower than outside the pass-band frequency of 1kHz sine wave signal filtered out, and basically retained the 10kHz sine wave signal.
The above filter performance testing experiments. Through experiments (1) and (2) to validate the performance of the filter low-pass filtering. Through experiments (3) to validate the filter to filter out