A polyphase RC filter implemented in ring configuration for a SiGe millimetre-wave receiver

A broadband polyphase RC Filter is presented suitable for millimetre-wave image reject receivers. A ring layout is chosen in preference to the traditional grid layout to improve symmetry. Crossover paths are implemented in microstrip and inverted microstrip with high isolation. Electromagnetic simulation shows a gain imbalance less than 1.0 dB and phase imbalance less than 1.4° from 20 to 50 GHz.