An X/K-band Class-E High-Efficiency Frequency Doubler

A class-E frequency doubler is presented at 20.8 GHz, the highest frequency reported to date. The circuit has 42.7% drain efficiency and 31.6% overall efficiency for an output power of 7.1dBm and 0.83 dB conversion gain. A maximum gain of 7.18 dB is achievable with 3.4dBm output power and 13.5% overall efficiency. The trade-off between efficiency and conversion gain is optimized by proper biasing and driving to obtain a 5.23 dB gain with an overall efficiency of 23.5%. The rejection of unwanted harmonics is greater than 26 dBm. The MESFET doubler is designed using a simple switching mode theory based on small signal device parameters.