A 400 MHz reconfigurable injection-locking based RC oscillator for ASK/FSK modulation

In this work an RC oscillator, operating at 404.5MHz, MICS (Medical Implant Communication Service) band, is evaluated for both ASK/FSK modulation and injection locking based FSK (Frequency Shift Keying) demodulation. The oscillator, which consists of a cross-coupled relaxation topology, is analyzed and evaluated in 130 nm IBM CMOS technology. Injection locking is driven by a differential current signal. ASK (Amplitude Shift Keying) and FSK modulation are performed by controlling the cross-coupled bias current and the MOS varactor capacitance respectively. Simulation results show that, at the free-running frequency of 404.5 MHz, the oscillator presents a phase noise of -126.36 and -133 dBc/Hz at 1MHz and 10 MHz offset frequency respectively, while consuming 50 micro Watts of power from a 1V supply voltage. The oscillator frequency locking range, for a 1 micro Ampère injected current, is 398 MHz to 410 MHz which covers the whole MICS band.