Low-noise Ku-band MMIC balanced P-HEMT upconverter

An enhanced design methodology for a low-noise Ku-band monolithic balanced high electron mobility transistor (HEMT) upconverter and its performance are presented in this paper. The mixer topology consists of a common source/common gate HEMT pair that performs the mixing and balun functions. A detailed study has been done to establish the role of the transistor model elements in the performance of the mixer. Based on this study, a new analysis is proposed to optimize the operating point of the mixer in order to get a tradeoff between conversion gain and port isolations. To combine the LO and intermediate-frequency (IF) signals, active circuits were used, as well as a high-pass filter in order to improve the isolations. The circuit size, including the filter and the combiners, is 3 mm/sup 2/. On-wafer measurements show a conversion gain over 2.5 dB, with only 3 dBm of LO power. A LO/RF isolation over 27 dB was measured in the whole LO band. The LO/IF isolation is over 27 dB thanks to the low reverse gain of the combiner HEMT's. A single sideband noise figure of 7.3 dB has been obtained.