Patent ID: 8686808

Claim:
A band combining filter for filtering a microwave signal, the band combining filter having at least one band edge at a band edge transition frequency, the filter comprising: a plurality of filter sections, each filter section comprising; first and second 3 dB hybrid couplers, each 3 dB hybrid coupler comprising first and second input ports and first and second output ports; a first resonator connected between the second input port of the first coupler and the first input port of the second coupler; and, a second resonator connected between the second output port of the first coupler and the first output port of the second coupler; each filter section comprising first and second input ports defined by the first input port of the first coupler and the second input port of the second coupler respectively; each filter section comprising first and second output ports defined by the first output port of the first coupler and second output port of the second coupler respectively; the filter sections being connected in cascade with the first and second outputs of one filter section being connected to the first and second inputs of the next filter section in the cascade; the band combining filter further comprising a coupled phase shifter in the cascade having first and second inputs adapted to receive microwave signals and provide microwave signals at output ports with a phase shift therebetween; wherein a subset of the filter sections are high Q filter sections with the Q values of the resonators of those filter sections having values each of which are at least a factor of three higher than the Q values of the resonators of the remaining filter sections.