Open Loop Filter Duplexer with Internal Stubs for GSM Cellular Base Station

A new filter duplexer with open loop resonators, having inside stubs, for GSM band in the DSC1800 Cellular Radio Base Station (RBS) standard is presented. The filters use resonators of square open loop types. The insertion of the stubs allows the perimeter of the loop to be less than l/2, which is the length used in the well-known canonical loop. The device was fabricated on PTFE (RO3010) board. An eight poles selective filter with a single pair of attenuation poles was used. The full wave EM simulator was used to obtain the desired dimensions of the resonators. Simulated and measured results are presented here.