ON THE DESIGN OF INPHASE AND QUADRATURE FILTERS FOR DELAY COMPENSATION

This correspondence addresses the problem of simultaneous separation a nd delay compensation of the inphase and quadrature components of a si gnal. The proposed approach is based on the notions of combined filter and common filter. The combined filter for a given delay has twice as many coefficients as the inphase filter or the quadrature filter. The coefficients of the combined filter for an arbitrary delay are comput ed as a linear combination of two members of a set of discrete delay f ilters. Finally, to further simplify the design, all the discrete dela y filters in the above mentioned set are polyphase components of a lon g filter called the common filter. The length of the common filter is determined by the requirement that all possible linear combinations of adjacent coefficients result in a filter that meets the desired passb and and stopband ripple specifications. This method, which requires th e design of one single filter, has much less computational complexity than extant approaches which require the design of a filter for every specified delay. The design of a product detector for an agile beamfor mer motivates the proposed method.