Highly Linear Distributed Mixer in 0.25- $\mu \text{m}$ Enhancement-Mode GaAs pHEMT Technology

This letter presents the design and measured results of novel wideband, highly linear gate-pumped distributed downconverter mixers. The circuit is realized in a 0.25-μm, Enhancement-mode GaAs pseudomorphic High Electron-Mobility Transistor process which requires no negative voltage supply. Two cells with different biases in parallel are used to achieve third-order intermodulation product cancelation. Each cell utilizes the distributed topology to absorb the first-order gate-source capacitances C
_gs1
. Two mixers are demonstrated: 1) a single-ended (SE) mixer and 2) a single-balanced (SB) mixer. The SE and SB mixers achieve a measured third-order input intercept point above 30 dBm in the RF frequency ranges from 6-26 GHz and 6-20 GHz, respectively. Both mixers show a conversion loss of less than 10 dB. The balanced mixer exhibits more than 30 dB of LO-RF isolation.