If I am doing a IQ FIR filter, do I only need one FIR for the I and one FIR for the Q, or more?

Answer 1

You need 2 filters.

If the I and Q channels are simply in quadrature with each other, then you should get by with identical filters, and you might be able to share one filter between the channels if your processor is fast enough.

If the I and Q channels are of different bandwidths (e.g. color encoded channels in a color NTSC TV broadcast), then the 2 filters will have to be different.

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