Shanthi Sudalaiyandi

UWB Vivaldi antenna for impulse radio beamforming

In this paper, two different types of Vivaldi antenna are designed and tested suitable for electromagnetic beamforming. The first is an antipodal Vivaldi antenna, while the other is a tapered slot Vivaldi antenna. They are both ultra wideband antennas for the 1 GHz to 5 GHz frequency band. They have low impulse distortion and the voltage standing wave ratio (VSWR) less than 2 throughout the entire bandwidth. The antennas are used for impulse radio beamforming.

An inductorless 3–5 GHz band-pass filter with tunable center frequency in 90 nm CMOS

A novel inductorless tunable switched-capacitor band-pass filter based on N-path periodically time-variant networks is presented. The proposed UWB band-pass filter is complete with ring-oscillator used for multi-phase clock generation suitable for power-efficient IR-UWB systems. The filter prototype was fabricated in TSMC 90 nm CMOS, and occupies a chip area of 0.004 mm2. It archives a -3 dB bandwidth of 2 GHz while the center frequency can be tuned from 4 GHz to 4.4 GHz. Power consumption is 1.1 mW from 1.2 V supply voltage, and the performance was verified experimentally.

A variable-gain single-bit ultra-wideband quantizer for baseband receiver front-end

This paper presents a novel variable-gain single-bit ultra-wideband (UWB) quantizer suitable for baseband receiver front-end fabricated in 90 nm CMOS technology. The prototype chip is tested, and measurement results are provided. The proposed quantizer achieves a -3 dB bandwidth covering a spectrum from 10 MHz to 2.7 GHz. The overall gain can be varied from 23 dB to 33 dB while the noise figure (NF) is between 7 dB and 10 dB. The quantizer core occupies a die area of 0.25 × 0.17 mm2 and consumes 4.8 mW from a 1.2 V supply voltage.

Power-efficient CTBV symbol detector for UWB applications

In this paper, we present a novel symbol detector architecture using time-domain running cross-correlation intended for impulse radio UWB communication. A bold new perspective on system design processing (CTBV) completely in continuous time is proposed and an implementation is carried out in 90 nm TSMC low power process technology. By exploring CTBV coding and unique combinational circuits for signal processing operations, a fast and power efficient solution is found to be feasible for clockless CMOS implementation.

Continuous-time symbol detector for IR-UWB rake receiver in 90 nm CMOS

In this paper, a coherent continuous-time symbol detector suitable for a simple RAKE receiver using single-bit correlation is reported. A working chip with fully integrated digital symbol detection without any clocks, ADC and filters for simple and power efficient CMOS implementation has been presented. Cross-correlating RAKE receiver with on-off keying is the most challenging receiver due to its hardware implementation complexity. Also process variations in 90 nm CMOS technology impose significant design challenges to the delayline. Optimal design of the delay elements and the use of pulse width controller blocks (PWC) along the delayline allows narrow pulses through the system significantly reducing the process variation impact. The optimized delayline combined with the high-speed counter and the match thresholder constitute a complete continuous-time IR-UWB RAKE receiver. With a data rate of 1.5 Mbit/s and a power consumption of 2.36 mW, operation of the symbol detector in continuous-time is verified with measured results. The symbol detector along with the ranging system in a master-slave configuration can estimate time-of-flight (ToF) value which aids localization.

Continuous-time single-symbol IR-UWB symbol detection

RAKE based receivers are the most challenging receiver due to its hardware implementation complexity. To build a cross-correlating RAKE receiver with on-off keying pose significant design challenges due to multipath components. Also process variations in 90 nm CMOS technology impose significant challenges in the clockless system. In this paper, a simple coherent RAKE receiver using single-bit correlation in continuous time is reported. A working chip with fully integrated digital symbol detection without any clocks, ADC and filters for simple and power efficient CMOS implementation. Optimal design of the delay elements in the tapped delayline and the use of pulse width controller blocks (PWC) along the delayline allows narrow pulses through the system. The optimized delayline combined with the continuous-time high speed counter and the match thresholder constitute a complete continuous-time RAKE receiver in CMOS. Initial chip measurement shows that a data rate of 1.5 Mbit/s with a power consumption of 0.78 mW was possible.

An inductorless 6-Path band-pass filter with tunable center frequency for UWB applications

This paper presents an inductorless switched-capacitor 6-path band-pass filter suitable for impulse radio ultrawideband (IR-UWB) application designed in nanometer CMOS technology. The proposed wideband band-pass filter is working in discrete-time intended for power-efficient IR-UWB systems. In 90 nm CMOS we were able to design a filter with -3 dB bandwidth of 2.5 GHz and a center frequency tunable from 4.1 GHz to 4.5 GHz. Estimated power consumption is 35 mW from 1.2 V supply voltage according to post-layout simulation. A novel ring oscillator based multiphase clock is proposed, enabling center-frequency tuning at microwave frequencies.

Continuous-time high-precision IR-UWB ranging-system in 90 nm CMOS

Precision ranging is a key factor for localization in wireless sensor networks. Most reported ranging solutions are limited by clock frequency or clock synchronization. With the combination of continuous-time binary value (CTBV) technique and the impulse-radio ultra-wideband (IR-UWB) technology, we have a promising approach towards high precision positioning combined with communication. In this paper, we have presented a UWB communication solution with embedded ranging by measuring the symbol round trip time without a common reference clock. A first working clockless UWB ranging transceiver realized in 90 nm CMOS technology with fully integrated digital symbol detection including a running cross-correlator is implemented. Preliminary measured results shows that two transceivers in a master-slave configuration can estimate distance with centimeter precision (≈ 1.4 cm).

A continuous-time IR-UWB RAKE receiver for coherent symbol detection

Impulse radio ultra-wide band (IR-UWB) technology has been an interesting area of research for low power short-range applications. Due to wide bandwidth, RAKE based receivers are preferred over other type of receivers. However, designing RAKE based correlating receivers remains quite challenging. Correlating receivers in digital domain are very power consuming due to the high-speed DSPs, ADC and matched filter. Synchronization is another issue. Hence we get rid of these power hungry blocks in the presented correlating RAKE receiver which does coherent symbol detection in continuous-time without the need for synchronized clocks. A IR-UWB RAKE receiver in continuous-time binary value (CTBV) overcoming some of the fundamental issues of the conventional correlating receiver is presented along with the measured results. The IR-UWB RAKE receiver along with the sampler, symbol generator and ranging block can be used as a high-precision ranging and communication transceiver for biomedical applications.

A 70-dB, 3.1–10.6-GHz CMOS amplifier in low-power 90 nm CMOS

This paper presents a novel high-gain CMOS amplifier suitable for ultra-wideband (UWB) applications. The proposed amplifier achieves a -3 dB bandwidth covering the entire FCC UWB spectrum from 3.1 GHz to 10.6 GHz with a very high gain of approximately 70 dB. The amplifier is an area-efficient, single-inductor solution designed for TSMC 90 nm CMOS low-power process while consuming 25.1 mW from 1.2 V supply voltage.