Yuan Guo-shun

A dual-mode complex filter for GNSS receivers with frequency tuning

A fifth/seventh order dual-mode OTA-C complex filter for global navigation satellite system receivers is implemented in a 0.18 μm CMOS process. This filter can be configured as the narrow mode of a 4.4 MHz bandwidth center at 4.1 MHz or the wide mode of a 22 MHz bandwidth center at 15.42 MHz. A fully differential OTA with source degeneration is used to provide sufficient linearity. Furthermore, a ring CCO based frequency tuning scheme is proposed to reduce frequency variation. The measured results show that in narrow-band mode the image rejection ratio (IMRR) is 35 dB, the filter dissipates 0.8 mA from the 1.8 V power supply, and the out-of-band rejection is 50 dB at 6 MHz offset. In wide-band mode, IMRR is 28 dB and the filter dissipates 3.2 mA. The frequency tuning error is less than ±2%.

Low voltage bandgap reference with closed loop curvature compensation

A new low-voltage CMOS bandgap reference (BGR) that achieves high temperature stability is proposed. It feeds back the output voltage to the curvature compensation circuit that constitutes a closed loop circuit to cancel the logarithmic term of voltage VBE. Meanwhile a low voltage amplifier with the 0.5 μm low threshold technology is designed for the BGR. A high temperature stability BGR circuit is fabricated in the CSMC 0.5 μm CMOS technology. The measured result shows that the BGR can operate down to 1 V, while the temperature coefficient and line regulation are only 9 ppm/°C and 1.2 mV/V, respectively.

A novel differential VCO circuit design for USB Hub

The paper describes a novel differential voltage controlled oscillator circuit, which is used in the phase locked loop of a USB hub chip. The output clock signals can be altered from 36MHz to 96MHz by changing the value of control signals. The voltage controlled oscillator architecture, module circuits of voltage controlled oscillator design, simulation results, and chip layout are included. Experimental results using CSMC 0.6/spl mu/m process technology show that the anticipatory performance can be obtained and the voltage controlled oscillator circuit consumes only 0.9 mW from a 5V power supply.