An upconverting circuit is disclosed. The upconverting circuit includes a
polyphase component generator that provides N.sub.p polyphase components
at each input polyphase cycle, wherein N.sub.p>2 on each input
polyphase cycle defined by a clock. A memory stores the polyphase
components from at least one polyphase cycle prior to the current
polyphase cycle. A plurality of filters process the polyphase components
stored in the memory. Each filter processes a plurality of the polyphase
components to generate a filtered polyphase component corresponding to
that filter. A multiplexer outputs the filtered polyphase components in a
predetermined order to generate a filtered output signal. In one
embodiment, each filter utilizes the same functional relationship to
generate the filtered polyphase components. In another embodiment, the
memory is a shift register. The filters can be of arbitrary complexity.