Design of 12 W X-band high power cascade amplifier

To achieve optimum electrical performance of a high power amplifier (HPA), there are many considerations that need to be taken care of, such as impedance matching, bias network design, grounding and heat sinking of the HPA device. Nowadays, most semiconductor manufacturers produce internally matched HPA devices to shorten the user's development time. Even though the device used is internally matched, ignorance of the above considerations may lead to device breakdown or oscillation. We present the design of a bias network and a simple microwave coupler with the primary consideration of low insertion loss at 8.3 GHz. Taking account of the practical considerations, we design and evaluate 2 W and 12 W HPA separately prior to integrating them with a coupler. In all cases, excellent measurement results are obtained.