A verv small, ultra-wideband MMIC balanced frequency doubler, which employs line-unified HEMT configurations, is proposed. A chip size of 1.0 mm x 0.9 mm is achieved with a conversion loss of 8-10 dB in the 4-40 (GHz output harmonics frequency range and fundamental frequency signal isolation of better than 21 dB above the input fundamental frequency of 7 GHz. Circuit parameters are optimized in a novel and simple prediction using an equation derived from HEMT's dc characteristic and a linear-state CAD software package. The doubler promises to realize miniaturized, wideband MMIC transmitters/receivers.
