RF Oscillator Based on a Passive RC Bandpass Filter

A passive RC bandpass filter (BPF) based voltage-controlled-oscillator (VCO) operating at 2.5 GHz is presented. In GHz frequency range, a preferred type of an oscillator is either an LC oscillator or a ring oscillator. An LC oscillator exhibits an excellent phase noise performance while its fabrication cost is expensive due to the inductors. On the other hand, a ring oscillator can be built with standard CMOS devices resulting in a cheap fabrication cost. However, it has a poor phase noise and jitter performance and is sensitive to power supply noise. This paper proposes a RC BPF-based oscillator. Its property is closer to a LC oscillator rather than a ring oscillator and, as a result, improves the jitter performance due to power supply noise. Also, it can be fabricated in a standard CMOS process since there is no inductor. To prove the proposed concept, a RC BPF-based oscillator was designed and fabricated in a standard 0.13-mum CMOS technology. An operating frequency of 2.5 GHz and phase noise of - 95.4 dBc/Hz at 1 MHz offset was measured. Power consumption was 2.86 mW from a 1.3 V supply voltage.