Design a Low Noise 5GHz Differential Cross-Coupled VCO and Colpitts VCO Using BiCMOS Technology

Abstract

This paper describes the 0.35 um SiGe BiCMOS Voltage Controlled Oscillators (VCOs). One is Cross-coupled VCO, and the other one is Colpitts VCO. Both of them are designed with the same method. For achieving lower noise, the differential structure was used at this design. The center frequency for Cross-coupled VCO and Colpitts VCO is 5GHz. The tuning range of Cross-coupled VCO and Colpitts VCO is 1750 MHz and 230 MHz, respectively. The phase noise and the figure of merit (the FOM) for Cross-coupled VCO, are -155.5 dBc/Hz and -224.7dBc/Hz @1MHz offset frequency at an oscillation frequency of 5GHz, respectively. The phase noise and the figure of merit value of Colpitts VCO is -134.1 dBc/Hz and -200.3 dBc/Hz at the 1MHz offset from the center frequency of 5GHz. For The DC current of Cross-coupled and Colpitts VCO is 2 mA and 4 mA , respectively. Considering a 3.0 V supply Cross-coupled voltage (VCC) for both VCOs. The output power of Cross-coupled VCO is -3.94 dBm and the Colpitts VCO achieves an output power of 5.428 dBm. Agilent ADS software is used throughout this work