Digital modulator employing a polyphase up-converter structure

Abstract

An upconverting circuit is disclosed. The upconverting circuit includes a polyphase component generator that provides Npolyphase components at each input polyphase cycle, wherein N>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.