A 2.5-GHz InGaP/GaAs differential cross-coupled self-oscillating mixer (SOM) IC

This letter presents a monolithic differential cross-coupled self-oscillating mixer (SOM). The SOM chip is fabricated using an InGaP/GaAs heterojunction bipolar transistor (HBT) foundry process and operates at 2.5 GHz. The chip provides voltage controlled oscillator (VCO) operation, up- and down-conversion mixing, and injection locking functionalities. The voltage down-conversion gain and the power up-conversion gain of up to 15 and 11.5 dB, respectively, are measured for the circuit. There is a compromise between obtaining a high conversion gain, and the oscillator power (-0.3 dBm for a 5-V supply) and phase noise (-84 dBc/Hz at 100 kHz). However, phase noise improvement of 32dB is observed by injection of a -30-dBm stable reference.