An IC based self-oscillating mixer for telecommunications

This work presents the measurement results of a 2.5 GHz push-pull self-oscillating mixer (SOM) circuit with internal and external LC resonators. This SOM is used for injection locked phase locked loop (ILPLL) applications, where a separate phase detector (PD) circuit is not required. This SOM design was fabricated using an InGaP/GaAs HBT foundry process. Output power of about 0 dBm is attained over a large frequency tuning range. The power consumption of the SOM is typically about 60 mW using a 5 V supply. The voltage down-conversion gain and power up-conversion gain of up to 15 and 11.5 dB are measured for the circuit. It is also observed that there is a compromise between obtaining a high conversion gain and low close-in to carrier phase noise. It is demonstrated that a phase noise improvement of up to 6 dB can be achieved by implementing an external LC resonator.