Design of miniature, wideband MMIC doubler

A wideband passive MMIC frequency doubler is designed. It only consists of input match circuit, two balanced diodes and a passive balun, and also DC bias. The input match circuit is mainly consisted of parallel capacitor to ground, which improves input return loss. Two balanced diodes are constructed by HEMT where drain and source have been short-circuited. The passive balun adopts a novel, but very simple structure, which makes two-way signals attain 180° phase difference in a very wide frequency range. DC bias is an extra circuit to optimize performance at low input power levels. It can be applied through either the “+” or “-” bias or both, with the other one either grounded or open. The whole doubler is simulated by ADS and is fabricated in the OMMIC process. We have carried out measurements by signal generator, spectrum analyzer and probe platform. The measurement results show that this doubler has relatively low conversion loss, about from 10dB to 14dB when input power level is bigger than 10dBm, and if DC bias is added the circuit, the conversion loss has a 1dB promotion approximately. The doubler also has favorable suppression over 1/2 and 3/2 spurs, which are better than 20dB, from 20GHz to 60GHz output frequencies. At the same time, the simulated results and measured results get good consistency from compared data. In addition, the doubler occupies little area, only 0.6mm², and so saves much cost.