A 10GHz–40GHz wideband PHEMT MMIC passive frequency doubler

A wideband GaAs PHEMT monolithic microwave integrated circuit passive frequency doubler is presented. It adopts balanced doubler structure, which consists of four diodes and two baluns of input port and output port. Four balanced diodes are constructed by PHEMT where drain and source have been short-circuited. To attain differential output signal feeding four balanced diodes, the structure of the balun is designed based on a multiple coupled line implementation way of the Marchand balun, which allows tighter coupling and improved performance in a wider bandwidth range. We adjust parameters of the balun to obtain the performance improvement, and after by simulation and optimization, the two-way output signals of the balun attain 180° ± 5° phase difference in a very wide frequency range, and the maximum loss point of whole frequency band is about 1dB. Finally, the whole doubler is simulated by ADS and is fabricated in the WIN PP25 process. We have carried out on-chip tested by use of signal generator, spectrum analyzer at probe platform. The measurement results show that this doubler has relatively wide output frequency range, from 10GHz to 40GHz, the conversion loss is from 10dB to 13dB when input power level is about 15dBm, and the conversion loss could be decreased if the input power level is increased. The fundamental harmonic and third harmonic suppression are better than 30 dB in the entire band, 4th harmonic rejections is also better than 25 dB in most of the output frequencies. The frequency doubler have been adopted widespread in microwave test instruments.