Root Raised Cosine Filter (Digital Demod)
Many communication systems use distributed filtering, that is, filtering is performed partially in the transmitter, to limit bandwidth, and partially in the receiver, to limit interference. To achieve the overall desired frequency response each filter's transfer function is based on the square root of the desired response. For these systems matched square-root raised cosine filters are used in the transmitter and the receiver sections of the system to achieve optimum signal to noise ratio. This implies that filter characteristics in the VSA (which simulates the receiver) must be selected to be similar to the filter characteristics of the transmitter. The standard NADC North American Digital Cellular demodulation type offered in this VSA provides this type of filter.
The equation for the square-root raised cosine (root Nyquist) filter follows (where T is the symbol interval):
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