A Low Phase Noise Crystal Oscillator with a Fast Start-Up Bandgap Reference for WLAN Applications

This article presents the design and implementation of a 40 MHz crystal oscillator (XO) with low phase noise, based on the 55 nm CMOS process, for wireless transceiver systems, particularly those used in Wireless Local Area Network (WLAN). The proposed design employs a bandgap reference circuit that includes a start-up circuit and a low-voltage common-source common-gate current mirror, which ensures that the bandgap reference circuit is powered up effectively across all temperatures and process corners. A low-pass filter is also incorporated at the low dropout regulator (LDO) input to reduce the phase noise of the XO circuit. The experimental results demonstrate that the proposed design achieves a final phase noise of −164.36 dBc/Hz at 100 kHz offset frequency, with a power consumption of 0.444 mW. The test of start-up time is 0.718 ms and the compact chip area is 0.088 mm2. According to the simulation and test results, the final FOM value calculated in this paper is 209.93 dBc/Hz at 100 kHz offset.