Microwave amplifier

A microwave amplifier for amplifying electromagnetic (EM) signals at a fundamental frequency, the amplifier comprising:

• a transistor configured to provide an amplified microwave signal at an output thereof;
• and
• a load network coupled to the output for shaping a waveform of the amplified microwave signal,
• wherein the load network comprises:
• a fundamental matching network that is tunable to provide impedance matching at the fundamental frequency;
• a half-wave transmission line for a second harmonic frequency of the amplified microwave signal, the half-wave transmission line being disposed between the output and the fundamental matching network;
• a quarter-wave stub and a five-quarter-wave stub for a third harmonic frequency of the amplified microwave signal arranged on the half-wave transmission line to provide an open circuit condition at the third harmonic frequency;
• and
• a quarter-wave stub for the second harmonic frequency and a quarter-wave stub for the fundamental frequency, arranged on the half-wave transmission line to provide a short circuit condition at the second harmonic frequency.