Jeong-Woo Lee

A 600-dpi capacitive fingerprint sensor chip and image-synthesis technique

This paper examines the possibility of a low-cost, high-resolution fingerprint sensor chip. The test chip is composed of 64/spl times/256 sensing cells (chip size: 2.7/spl times/10.8 mm/sup 2/). A new detection circuit of charge sharing is proposed, which eliminates the influences of internal parasitic capacitances. Thus, the reduced sensing-capacitor size enables a high resolution of 600 dpi, even using a conventional 0.6 /spl mu/m CMOS process. The partial fingerprint images captured are synthesized into a full fingerprint image with an image-synthesis algorithm. The problems and possibilities of this image-synthesis technique are also analyzed and discussed.

A fully integrated CMOS frequency synthesizer with charge-averaging charge pump and dual-path loop filter for PCS- and cellular-CDMA wireless systems

This paper presents the design of a fully-integrated CMOS frequency synthesizer for PCS- and cellular-CDMA wireless systems. The proposed charge-averaging charge pump scheme suppresses fractional spurs and the VCO combined with coarse tuning improves phase noise characteristics. The improved architecture of the dual-path loop filter makes it possible to implement a large time constant on a chip. Fabricated in 0.35-/spl mu/m CMOS technology, this circuit provides 10 kHz channel spacing with phase noise of -106 dBc/Hz at 100 kHz offset. Power dissipation is 60 mW with 3.0 V supply.

Full-CMOS 2-GHz WCDMA direct conversion transmitter and receiver

This paper presents a full-CMOS transmitter and receiver for 2.0-GHz wide-band code division multiple access with direct conversion mixers and a DC-offset cancellation scheme. The direct conversion scheme combined with a multiphase sampling fractional-N prescaler alleviates the problems of the direct conversion transmitter and receiver. Digital gain control is merged into the baseband filters and variable-gain amplifiers to optimize the linearity of the system, reduce the noise, and improve the sensitivity. Variable-gain amplifiers with DC-offset cancellation loop eliminate the DC-offset in each stage. The chip implemented in 0.35-/spl mu/m CMOS technology shows the experimental results of 6 dBm maximum output power with 38-dB adjacent channel power rejection ratio at 1.92 MHz, 50-dB dynamic range, and 363-mW power consumption in the transmitter. The receiver shows -115.4 dBm sensitivity, a 4.0-dB noise figure, and a dynamic range of 80-dB with 396-mW power consumption.

A single-chip 2.4-GHz direct-conversion CMOS receiver for wireless local loop using multiphase reduced frequency conversion technique

A single-chip direct-conversion CMOS receiver for 2.4-GHz wide-band code-division multiple-access wireless local loop (WLL) is described. The chip includes a low noise amplifier, a 12-phase downconverter, a variable gain amplifier, a g/sub m/-C channel selection filter, a programmable phase-locked loop for seven channel frequencies, and a 4-bit flash analog-to-digital converter. The proposed multiphase reduced frequency conversion scheme combined with a multiphase sampling fractional-N prescaler, a cascaded dc-offset canceler and distributed automatic gain control loops offers solutions to problems of a direct-conversion receiver. Experimental results show -115-dBm sensitivity, 4.4-dB noise figure, and 95-dB dynamic range, which sufficiently meet commercial WLL specification.

A CMOS dual-band fractional-n synthesizer with reference doubler and compensated charge pump

A fully integrated dual-band frequency synthesizer in 0.35 /spl mu/m CMOS technology achieves a phase noise of -141 dBc/Hz at 1.25 MHz offset in the PCS band with a reference frequency doubler. Fractional spurs are reduced by 8.6 dB at 50 kHz offset with a replica compensated charge pump.

Comparison frequency doubling and charge pump matching techniques for dual-band /spl Delta//spl Sigma/ fractional-N frequency synthesizer

The frequency synthesizer with two LC-VCOs is fully integrated in a 0.35-/spl mu/m CMOS technology. In supporting dual bands, all building blocks except VCOs are shared. A current compensation scheme using a replica charge pump improves the linearity of the frequency synthesizer and, thus, suppresses spurious tones. To reduce the quantization noise from a /spl Delta//spl Sigma/ modulator and the noise from the building blocks except the VCO, the proposed architecture uses a frequency doubler with a noise-insensitive duty-cycle correction circuit (DCC) in the reference clock path. Power consumption is 37.8 mW with a 2.7-V supply. The proposed frequency synthesizer supports 10-kHz channel spacing with the measured phase noise of -114 dBc/Hz and -141 dBc/Hz at 100-kHz and 1.25-MHz offsets, respectively, in the PCS band. The fractional spurious tone at 10-kHz offset is under -54 dBc.

A reset-free anti-harmonic delay-locked loop using a cycle period detector

This paper describes a new delay-locked loop (DLL) circuit that uses a replica delay line and a cycle period detector to solve the false lock problem in the conventional DLLs. The auxiliary loop in the proposed DLL monitors the lock state of the main loop by estimating the cycle period of the input clock and decides whether the main loop is in the coarse lock state or not. The auxiliary loop does not require an external reset or a start-up signal for the coarse lock operation, which is performed in the background without affecting the fine lock operation of the main loop. The proposed DLL is useful in the applications such as wide range DLLs and multiphase clock generators. The proposed DLL was implemented in 0.25-/spl mu/m mixed-mode CMOS technology and its operating frequency ranges from 30 to 200 MHz. Its cycle-to-cycle rms jitter is 12.8 ps at 133 MHz, and it dissipates 30 mW at 2.5 V.

A single-chip 2.4 GHz direct-conversion CMOS transceiver with GFSK modem for Bluetooth application

This paper describes the radio transceiver for Bluetooth application operating at 2.4 GHz ISM band. The transceiver uses low cost CMOS technology and integrates all components including PLL. Only RF matching elements and bypassing capacitors for power supply stability are required for a complete transceiver. The proposed transceiver is implemented with 0.25 μm CMOS process and draws 60 mA from 2.7 V supply in receiver active mode.

A fully-integrated CMOS frequency synthesizer with charge-averaging charge pump and dual-path loop filter for PCS- and cellular-CDMA wireless systems

This paper presents the design of a fully-integrated CMOS frequency synthesizer for PCS- and cellular-CDMA wireless systems. The proposed charge-averaging charge pump scheme suppresses fractional spurs and the VCO combined with coarse tuning improves phase noise characteristics. The improved architecture of the dual-path loop filter makes it possible to implement a large time constant on a chip. Fabricated in 0.35-/spl mu/m CMOS technology, this circuit provides 10 kHz channel spacing with phase noise of -106 dBc/Hz at 100 kHz offset. Power dissipation is 60 mW with 3.0 V supply.

A single-chip 2.4 GHz direct-conversion CMOS receiver for wireless local loop using one-third frequency local oscillator

A single-chip direct-conversion CMOS receiver for 2.4 GHz wide-band CDMA for wireless local loop (WLL) is described. The chip includes an LNA, a 12-phase down converter, a variable gain amplifier, a gm-C channel selection filter, a programmable PLL for 7 channel frequencies, and a 4-bit flash ADC. The proposed 12-phase down conversion scheme combined with a multi-phase sampling fractional-N prescaler, a cascaded DC-offset canceler and distributed AGC loops offers solutions to the problems of a direct conversion receiver. Experimental results show -115 dBm, sensitivity, 4.4 dB noise figure, and 95 dB dynamic range.