Mismatched filters for Frank polyphase codes via sidelobe inversion

A computationally efficient mismatched filter for Frank polyphase codes is proposed. It is based on an efficiently constructed matched filter followed by one or more stages of a sidelobe inversion (SLI) filter. This sidelobe inversion filter inherits the computationally efficient structure used for the matched filter. With the addition of few extra multipliers, a significant increase in the main lobe to peak sidelobe ratio is achieved. The proposed filter is area and power efficient, as well. The total delay is more than that of the length-optimal mismatched filter, but is of no significant consequence in most applications.