A Quadrature Signals Tutorial: Complex, But Not Complicated

Understanding the 'Phasing Method' of Single Sideband Demodulation

Complex Digital Signal Processing in Telecommunications

Christopher Felton's current favorite projects are implementing DSP digital circuits with MyHDL for FPGAs. More information @ LinkedIn. Follow @FeltonChris !func...show full bio

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In the previous post the Python scipy.signal *iirdesign* function was disected. We reviewed the basics of filter specification and reviewed how to use the *iirdesign* function to design IIR filters. The previous post I only demonstrated low pass filter designs. The following are examples how to use the *iirdesign* function for highpass, bandpass, and stopband filters designs.

The following is a highpass filter design for the different filter types. Refer to the previous post for information on the i*irdesign* function arguements and usage.

Again, similiar to the approach in the previous post tighter specifications can be given for the ellip and cheyb2 filter design.

As mentioned, a bandpass filter coefficients can be created with the *iirdesign* function as well. Since the *iirdesign *function is similiar for the different filter types we will only use the ellip and cheby2 for the rest of the examples.

And lastely here is an example to create a stopband filter.

The scipy.signal *iirdesign* function, similiar to other signal processing packages, is a flexible tool to design and generate filter coefficients for an IIR filter.

Christopher Felton's current favorite projects are implementing DSP digital circuits with MyHDL for FPGAs. More information @ LinkedIn.

Follow @FeltonChris

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Comments / Replies

fwkz

Said:

How exactly do you compute phase response?

1 year ago

+1

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cfelton

Said:

In this case I am using the signal.freqz to generate the *complex* response. The phase is the angle of the complex values. I can say w,H = signal.freqz(b,a) and plot(w, angle(H))

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cfelton

Replied:

This code snippet includes and example using the signal.freqz and plotting the response, http://www.dsprelated.com/showcode/270.php

fwkz

Replied:

What about phase response in previous post? Phase characteristic is completely different, much more smooth. I execute code from previous example and I get completely different shape.

w,H = signal.freqz(b,a) and plot(w, angle(H)) doesn't make sense there. How do you compute it?

w,H = signal.freqz(b,a) and plot(w, angle(H)) doesn't make sense there. How do you compute it?

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