MMIC Power Amplifier Output Combiner Network Considerations for S-Band Applications

The output combiner network for any power amplifier application that utilizes 2 or more parallel combined active devices is well known to be a critical component for a successful design. At higher microwave and millimeter frequencies, distributed corporate combiners are generally employed for a low loss, integrated combiner solution. This combiner technique can also be employed for lower microwave frequency applications, for example, for S-Band MMIC power amplifiers. Though relatively easy to model and design, these lower frequency applications present unique challenges of their own. This paper compares several possible solutions to the combiner network problem for the S-Band MMIC applications. A comparative study of the various solutions is presented. This study was used as a selection process for the design of a S-Band power amplifier MMIC that was subsequently fabricated, packaged and tested. Modeled versus measured performance, with respect to the output combiner network, shows very good agreement.