A wideband two-way UHF stripline combiner

A two-way combiner with a built-in broadside-coupled stripline coupler, for digital video broadcast transmitters at UHF frequencies is presented. The combiner exhibits more than 28dB of return losses at all ports in the entire digital television broadcast frequency band (namely 470MHz-862MHz). The isolation levels between each pair of isolated ports are more than 29dB in the above frequency band. The excellent frequency responses are obtained due to our modifications in the structure of the constituent coupled-line coupler in the form of the utilization of a multi-section broadside-coupled stripline structure and the elimination of the improper stripline bends. While the presented combiner satisfies all standard industrial requirements such as 3U (three Rack Units) distance of input ports, it shows wideband and non-resonant behavior in the frequency responses. In addition, by introducing a novel asymmetry in the structure of the intrinsic coupled-line coupler, significant reductions in the combiner size and cost are achieved.