Huang Shizhen

An MWCNT-doped SNO2 thin film NO2 gas sensor by RF reactive magnetron sputtering

An MWCNT-doped (multi-walled carbon nanotube) SnO2 thin film NO2 gas sensor, prepared by radio frequency reactive magnetron sputtering, showed a high sensitivity to ultra-low concentrations of NO2 in the parts per billion range. X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy (SEM) characterizations indicated that the MWCNTs were affected by the morphology of the SnO2 thin film and the particle size. The properties of the MWCNT-doped SnO2 sensor, such as sensitivity, selectivity, and response-recovery time, were investigated. Experimental results revealed that the MWCNT-doped SnO2 thin film sensor response to NO2 gas depended on the operating temperature, NO2 gas concentration, thermal treatment conditions, film thickness, and so on. The mechanism of the gas-sensing property of the MWCNT-doped Sn22 thin film sensor was investigated and showed that the improved gas-sensing performance should be attributed to the effects between MWCNTs (p-type) and SnO2 (n-type) semiconductors.

A design of high PSRR CMOS voltage reference based on subthreshold MOSFETs

Based on the principle of subthreshold voltage references, a voltage reference circuitry with high PSRR is proposed in this work. In HSPICE the simulation result shows that the PSRR performance of the circuit is very good as they are 53 dB at 100 KHz, 35 dB at 100 MHz and the max is close to 92 dB, the reference voltage is 706.92plusmn1.16 mV and the average temperature coefficient is 12.9 ppm/degC at the 5 V supply voltage as well as the range of -55degC to +125degC. Moreover, the current dissipation is not more than 1.6 muA at 5 V.

A novel VSWR-protected and controllable CMOS class E power amplifier for Bluetooth applications

This paper describes the design of a differential class-E PA for Bluetooth applications in 0.18 µm CMOS technology with load mismatch protection and power control features. The breakdown induced by load mismatch can be avoided by attenuating the RF power to the final stage during over voltage conditions. Power control is realized by means of “open loop” techniques to regulate the power supply voltage, and a novel controllable bias network with temperature compensated is proposed, which allows a moderate power control slope (dB/V) to be achieved. Post-layout Simulation results show that the level of output power can be controlled in 2 dBm steps; especially the output power in every step is quite insensitive to temperature variations.

A wide band and low PN PLL design for digital tuner

In order to realize a wide-band and low phase noise PLL for digital tuner, the desired tuning range of the PLL describes in this paper is divided into 8 sections according to different L/C tank circuits changed by channel selection, then a coarse-tuning loop is designed in the system to automatically select the suitable one of the 8 tuning curves which have overlapped part besides a fine-tuning loop that is the traditional PLL required, yielding design tradeoffs between output amplitude, power, locking time, and other factors.

Design of a broadband LNA for TV tuner

This paper described the design of a broadband LNA for TV tuner. The LNA uses two stage structures to achieve trade off of output impedance match and gain. In order to reduce the NF of the amplifier, noise canceling principle is adopted to cancel the noise. The simulation result shows that, in operation bandwidth 48 MHz~860 MHz, the gain is 24 dB, Noise figure is 3 dB, input impedance and output impedance match are also good.