A high-efficiency and high output power K-Band frequency doubler using InGaAs PHEMT power device is developed, which features high fundamental frequency rejection, high efficiency, good conversion gain over wide bandwidth, and high output power. A compact lumped rat-race hybrid and an output buffer amplifier are implemented on chip for a balanced design and high output power. The circuit exhibits measured conversions gain about 8 dB over the output frequencies from 12 to 22 GHz. The fundamental frequency suppression is better than 20 dB and the second harmonic saturation output power is higher than 12 dBm with a miniature chip size of 2 mm × 1 mm.
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