Same-band combiner for co-sited base stations

A signal combiner comprising:

• a first port configured to receive a first input signal comprising first and second receive bands and to transmit a first output signal comprising a transmit band;
• a second port configured to output a second output signal comprising the first receive band;
• a third port configured to output a third output signal comprising the second receive band and to receive a second input signal that is to be transmitted from the first port as the first output signal;
• a load forming a fourth port in a four-port network comprising the first, second, and third ports;
• a plurality of resonators within a plurality of chambers arranged in a constant-impedance-bandwidth configuration;
• a first transmission line coupling the first and third ports to each other and to a first resonator of the plurality of resonators;
• and
• a second transmission line coupling the second port and the load to each other and to at least a second resonator of the plurality of resonators different from the first resonator.