Kin Keung Lee

A Sub-

A new current-mode bandgap reference circuit (BGR) which is capable of generating sub-1-V output voltage is presented. It has not only the lowest theoretical minimum current consumption among published current-mode BGRs, but also additional advantages of an inherent curvature-compensation function and not requiring NPN BJTs. The curvature-compensation is achieved by utilizing the exponential behavior of sub-threshold CMOS transistors to compensate the BJT base-emitter voltage high-order temperature dependence. By taking advantages of the continuing development of CMOS technology, sub- μW power consumption is achieved with a reasonable core area. Related design considerations and challenges are discussed and analyzed. The proposed BGR is realized in a TSMC 90 nm process. Measurement results shows a temperature coefficient without trimming as low as 10.1 ppm/°C over a temperature range of 70 °C because of the proposed curvature-compensation technique. The average value is 32.6 ppm/°C which could be improved by trimming resistor ratios. The average power consumption at room temperature is 576 nW, with a core area of only 0.028 mm2.

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A low-power impulse radio (IR) ultra wideband (UWB) pulse generator (PG) is presented. It uses digital gate-delay for timing achieving good power efficiency and acceptable spectral filling. The circuit is scalable in both bandwidth and center frequency. Both energy consumption and chip area are reduced compared to most conventional higher order Gaussian PGs. The PG is realized in a TSMC 90 nm CMOS process. Measurements show the energy consumption from a 1.2 V to be 5.2 pJ/pulse for a 200 MHz pulse repetition frequency (PRF). The core area is 0.0015 mm2 (38 µm×40 µm). Lastly, a dynamic pre-charge (DPC) scheme is proposed to eliminate the standby current and make the PG favourable for low-data-rate applications.

Bandgap Reference Circuit With an Inherent Curvature-Compensation Property

An impulse radio ultrawideband (IR-UWB) transmitter (TX) intended for long-range passive radio-frequency (RF) identification tags is presented. It is wirelessly powered by an ultrahigh-frequency (UHF) signal. A 128-bit pseudonoise code is transmitted when enough energy is harvested. A new on-off-keying multicycle energy-efficient IR-UWB pulse generator (PG) is proposed, and a co-design with power management circuits is introduced to improve the system supply noise performance. A novel injection-locking divider co-designed with an RF voltage rectifier is proposed to eliminate the injection input resistive load that exists in some designs; otherwise, the input sensitivity would be degraded. A proof-of-concept prototype is fabricated in a TSMC 90-nm CMOS process. Measurements show the TX input sensitivity to be approximately -17.5 dBm with a 900-MHz UHF input. The measured PG output swing is 195 mVp-p with a -10 dB bandwidth of approximately 3.4 GHz.

A 5.2 pJ/pulse impulse radio pulse generator in 90 nm CMOS

Radio-frequency identification (RFID) systems are widely used in our daily life. Although several proposed solutions are in production, limitations are still significant. In this paper, the current RFID technology is reviewed and major shortcomings are discussed. Our expected features on next generation RFID systems are described. Finally, we propose an impulse-radio (IR) ultra-wideband (UWB) RFID system and present how to improve the performance by using IR-UWB technology.

A Wireless-Powered IR-UWB Transmitter for Long-Range Passive RFID Tags in 90-nm CMOS

UWB backscatter RFID systems require high quality clock signals and crystal oscillator is one of the few candidates. A study of a low-power parallel-mode crystal oscillator for such applications is presented. A 7.8125 MHz Pierce crystal oscillator is realized in a TSMC 90 nm CMOS process. It has a frequency stability of ±7 ppm from 0 to 70°C and draws 36 μW from a 1.2 V supply. The core area excluding pads is 0.021 mm2.

IR-UWB technology on next generation RFID systems

The demand for wireless-powered circuits are increasing rapidly, RFID and WSN are good examples. One of the most important components is the on-chip voltage rectifier. Research has been conducted intensively on the rectifier design, however not many of them considered the co-design with antennas and matching networks. This paper intends to fill this gap. An analysis on the co-design is presented. A new look-up table design methodology is proposed and simulations are done using Cadence to prove the methodology.

A study of low-power crystal oscillator design

A novel impulse radio (IR) ultra wideband (UWB) pulse generator (PG) intended for RFID tags is presented. A new pulse-shaping approach suited for CMOS implementation is proposed. The power consumption and chip area are reduced compared to the conventional higher order Gaussian PGs. The proposed PG uses digital gates for timing achieving good power efficiency and, meanwhile, acceptable spectral filling. The circuit is scalable both in bandwidth and center frequency. The PG is designed in a TSMC 90 nm CMOS technology. Post-layout simulations show a worst-case power consumption from a 1.2 V supply to be 6.5 pJ/pulse for a 100 MHz pulse repetition frequency (PRF). The chip area is 0.00079 mm2 (38.2 µm×20.8 µm) for the PG core.

Co-design of antenna, matching network and voltage rectifier in state-of-the-art CMOS

This brief presents a continuous-time impulse radio ultrawideband transmitter. The transmitter is a part of a high-precision ranging single-chip transceiver that measures the time-of-flight symbol propagation. The clock burst generator in the transmitter will initiate symbol transmission in continuous time unbounded by any clock signal while maintaining an accurate chip rate during symbol transmission. Using a calibration circuit, the clock period can be programmed precisely to compensate for device mismatch. The transmitter is fabricated in Taiwan Semiconductor Manufacturing Company 90-nm CMOS technology and occupies an area of 0.123 mm2. The programmable clock range is from 12.65 to 111 MHz, and the measured rms jitter is 3.26 ps at 50 MHz. The entire transmitter has a power consumption of 1.41 mW at the data rate of 2 Mbit/s.

A novel 6.5 pJ/pulse impulse radio pulse generator for RFID tags

A low-power on-off-keying impulse-radio (IR) ultra-wideband (UWB) pulse generator (PG) operating at band group # 6 is presented. It is intended for IR-UWB radio applications. The IR signal is generated by utilizing the propagation delay of a delay-line and shaping its output. An on-chip inductor is used to tune out the output parasitic capacitance, hence the power consumption is reduced. Successfully implemented in a TSMC 90 nm CMOS process, measurements results show an energy consumption of 5.3 pJ/pulse with a 1.2 V supply. The pulse width and -10-dB bandwidth are 890 ps and 1.8 GHz respectively. The core area is 0.082 mm2.

An IR-UWB Transmitter for Ranging Systems

A low-power on-off-keying impulse-radio (IR) ultra-wideband (UWB) pulse generator (PG) intended for wireless-powered IR-UWB radio applications is presented. The proposed PG has high flexibility, the center frequency, output power and pulse-width (PW) are controllable depending on channel conditions and data rates. Qualitative frequency-domain and transient analyses are presented. A new figure-of-merit (FoM) is proposed such that a more precise comparison between different PGs can be made. The PG is successfully implemented in a TSMC 90 nm CMOS process, measurements show the energy consumption and FoM to be 2.8-7.5 pJ/pulse and 1.6-2.6% respectively. The output swing and PW are 277-329 mVp-p and 509-1088 ps respectively. The core area is 0.092 mm 2 .