The Design Of High Performance Wideband Voltage-Controlled Oscillator In DRM/DAB Receiver

Analog broadcasting digitization is the trend of technological development, Didital Radio Mondiale (DRM) and Digital Audio Broadcasting (DAB) are two emerging common digital broadcasting. In DRM/ DAB system design, the VCO (Voltage Controlled Oscillator) needs to meet a wide tuning range, while the tuning gain difference needs to be controlled within a certain range, so that the stability of the phase locked loop can be increased. In order to reduce the influence of noise, we need a low tuning gain. Since the VCO is a large-signal circuit, wideband VCO output oscillation amplitude variation in the entire tuning range needs to be kept within a low range. To meet these requirements, this paper studied this wideband VCO design.Based on SMIC 0.18-μm Mixed Signal CMOS process, an LC-tuned VCO with a wide tuning range, a low tuning gain variation and a stable output oscillation amplitude is designed. Firstly, the mathematical model and simulation methods of the VCO is introduced, the advantages and disadvantages of common variable capacitance is analyzed. The phase noise model and wideband VCO output oscillation amplitude problems is also discussed. In order to get a wide tuning range, this paper analyzes and compares the advantages and disadvantages of different wideband VCO structures. A variable capacitance is choosed as a way to adjust the oscillation frequency of VCO. For variable capacitance specific implementation, this paper analyzed and simulated the common fixed capacitor array VCO, and the shortcomings is pointed out, eventually a combination of the variable capacitor array and fixed capacitor array VCO is implemented, enabling low tuning gain variation to be realized. Finally, the analog feedback loop control structure is selected, in order to obtain a stable output amplitude.The pre-simulation, layout and post-simulation of the wideband VCO design are achieved by means of Cadence Spectre simulation tools. The simulation results show that the wideband VCO meets the project requirements and can be integrated to the DRM/DAB receiver system.