A high performance 1 GHz voltage controlled oscillator using neural system architecture

In this paper, an improved voltage controlled oscillator scheme with temperature compensated frequency, a wide linear range, low phase noise and low power dissipation is presented for application in transmitting signals of gas sensors from mines using RF communication. The basic unit of the oscillator is a ring based differential amplifier incorporating temperature compensated voltage dependent PMOS capacitors and standard PMOS triode connected load with temperature compensated biasing scheme. The increased nonlinearity in the presence of PMOS capaciors is reduced to 0.001% using a digitally programmable neural architecture which is simulated in the mixed signal domain of SYNOPSYS. Additionally, the temperature compensated PMOS capacitor improves the sensitivity of the VCO and the standard temperature compensated biasing scheme of the PMOS triode connected load reduces the drift in amplitude with temperature variation. The PMOS varactor lowers the phase noise of the VCO compared to parasitic capacitors without increasing the power dissipation. The entire VCO is designed using 0.18 mu m typical technology of TSMC with 1.8 V power supply. The tuning range of the VCO is 0.3-1.7 V, maximum frequency is 1 GHz with a linear change of around 750 MHz, temperature sensitivity and power consumption are around 50 ppm/degrees C and 2 mW respectively. The phase noise is obtained to be around - 123dBc/Hz at 1 MHz offset frequency.