Limitations in the Transmission Line and High Power Rate Race Combiners Used in SSPA 450W CW Amplifiers in the C Band

The article presents power summing on the example of a microwave amplifier operating in the 4.4÷5 GHz band, implemented on GAN HEMT transistors. The output power of 400 W CW was obtained by summing four modules of a multi-stage 125 W amplifier using Rate-Race combiners implemented in coaxial line technology as well as a Magic-T waveguide combiner. The temperature phenomena that appeared when summing the output power for a continuous wave (CW) signal were described. The amplifier is designed in class A to obtain low values of EVM parameters while maintaining output power and efficiency.