Energy-efficient, short-range ultra-wideband radio transceivers

Short-range wireless communications continually attract interest from both industry and academia, and it is changing our life in every aspect in the last decade. The design of wireless transceivers is the bottleneck for variety applications, due to RF modeling inaccuracy, stringent FCC regulations over the transmitted power spectrum, interference, multi-path reflections, modulation scheme, receiver sensitivity, and synchronization. In addition, energy efficiency is always one of the most important design goals. Ultra-Wideband(UWB) is found to be very energy-efficient due to its low duty cycle and potentially high data rate due to its wide bandwidth. However, there still remain unsolved issues with UWB transceivers, such as pulse shaping, multi-path reflections, and receiver clock synchronization. To address these, novel techniques such as wireless multi-path equalization, pulse injection-locking for receiver clock synchronization, reconfigurable pulse shaping, low power wireless clock distribution, and an ultra-low-power super-regenerative receiver are implemented and verified on silicon. Three chips are designed and verified: a 3-5GHz Impulse-Radio(IR) UWB transceiver, a 3-60GHz all digital reconfigurable transmitter, and a 402-405MHz MICS/UWB(Sub-GHz) super-regenerative receiver incorporating wireless clock synchronization. A detailed design methodology, measurement results, and discussions are presented

A 3.1-4.8GHz IR-UWB All-Digital Pulse Generator in 0.13-um CMOS Technology for WBAN Systems

Analog, Digital & RF Circuit DesignImpulse Radio Ultra-WideBand (IR-UWB) systems have drawn growing attention for wireless sensor networks such as Wireless Personal Area Network (WPAN) and Wireless Body Area Network (WBAN) systems ever since the Federal Communications Commission (FCC) released the spectrum between 3.1 and 10.6GHz for unlicensed use in 2002. The restriction on transmitted power spectral density in this band is equal to the noise emission limit of household digital electronics. This band is also shared with several existing service, therefore in-band interference is expected and presents a challenge to UWB system design. UWB devices as secondary spectrum users must also detect and avoid (DAA) other licensed users from the cognitive radio???s point of view. For the DAA requirement, it is more effective to deploy signal with variable center frequency and a minimum 10dB bandwidth of 500MHz than a signal covering the entire UWB spectrum range with fixed center frequency. A key requirement of the applications using IR-UWB signal is ultra-low power consumption for longer battery life. Also, cost reduction is highly desirable. Recently, digital IR-UWB pulse generation is studied more than analog approach due to its lower power consumption. An all-digital pulse generator in a standard 0.13-um CMOS technology for communication systems using Impulse Radio Ultra-WideBand (IR-UWB) signal is presented. A delay line-based architecture utilizing only static logic gates and leading lower power consumption for pulse generation is proposed in this thesis. By using of all-digital architecture, energy is consumed by CV2 switching losses and sub-threshold leakage currents, without RF oscillator or analog bias currents. The center frequency and the fixed bandwidth of 500MHz of the output signal can be digitally controlled to cover three channels in low band of UWB spectrum. Delay based Binary Shift Keying (DB-BPSK) and Pulse Position Modulation (PPM) schemes are exploited at the same time to modulate the transmitted signals with further improvement in spectrum characteristics. The total energy consumption is 48pJ/pulse at 1.2V supply voltage, which is well suitable for WBAN systems.ope

380 MHz Low-Power Sharp-Rejection Active-RC LPF for IEEE 802.15.4a UWB WPAN

This paper describes a wide-band sharp-rejection active-RC low pass filter (LPF) for pulse-based UWB IEEE 802.15.4a WPA, applications. Sharp rejection is attributed to the combination of different AC characteristic of three biquads in series. A simple operational amplifier (Op-amp) is adopted to ensure high frequency performance for the designed filter. The LPF is designed in 0.13μm TSMC CMOS process. The cutoff frequency is 380MHz with about 50% of the tuning range from 300-500MHz. The rejection is 40 dB at 600 MHz. The passband ripple is less than 1.5dB and the filter consumes 4.6mA from 1.2V supply. Core chip size is 580 x 700μm2

380 MHz Low-Power Sharp-Rejection Active-RC LPF for IEEE 802.15.4a UWB WPAN

This paper describes a wide-band sharp-rejection active-RC low pass filter (LPF) for pulse-based UWB IEEE 802.15.4a WPA, applications. Sharp rejection is attributed to the combination of different AC characteristic of three biquads in series. A simple operational amplifier (Op-amp) is adopted to ensure high frequency performance for the designed filter. The LPF is designed in 0.13μm TSMC CMOS process. The cutoff frequency is 380MHz with about 50% of the tuning range from 300-500MHz. The rejection is 40 dB at 600 MHz. The passband ripple is less than 1.5dB and the filter consumes 4.6mA from 1.2V supply. Core chip size is 580 x 700μm2

An all-digital transmitter for pulsed ultra-wideband communication

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2008.Includes bibliographical references (p. 91-96).Applications like sensor networks, medical monitoring, and asset tracking have led to a demand for energy-efficient and low-cost wireless transceivers. These types of applications typically require low effective data rates, thus providing an opportunity to employ simple modulation schemes and aggressive duty-cycling. Due to their inherently duty-cycled nature, pulse-based Ultra-Wideband (UWB) systems are amenable to low-power operation by shutting off circuitry during idle mode between pulses. Furthermore, the use of non-coherent UWB signaling greatly simplifies both transmitter and receiver implementations, offering additional energy savings. This thesis presents an all-digital transmitter designed for a non-coherent pulsed UWB system. By exploiting relaxed center frequency tolerances in non-coherent wideband communication, the transmitter synthesizes UWB pulses from an energy efficient, single-ended digital ring oscillator. Dual capacitively-coupled digital power amplifiers (PAs) are used in tandem to generate bipolar phase modulated pulses for spectral scrambling purposes. By maintaining opposite common modes at the output of these PAs during idle mode (i.e. when no pulses are being transmitted), low frequency turn-on and turn-off transients typically associated with single-ended digital circuits driving single-ended antennas are attenuated by up to 12dB. Furthermore, four level digital pulse shaping is employed to attenuate RF side lobes by up to 20dB. The resulting dual power amplifiers achieve FCC compliant operation in the 3.5, 4.0, and 4.5GHz IEEE 802.15.4a bands without the use of any off-chip filters or large passive components. The transmitter is fabricated in a 90nm CMOS process and requires a core area of 0.07mm2. The entirely digital architecture consumes zero static bias current, resulting in an energy efficiency of 17.5pJ/pulse at data rates up to 15.6Mbps.by Patrick Philip Mercier.S.M

Ultra-Wideband Transceiver Design And Optimization

University of Minnesota Ph.D. dissertation. July 2015. Major: Electrical Engineering. Advisor: Ramesh Harjani. 1 computer file (PDF); xiii, 128 pages.The technology landscape has quickly changed over the last few years. Developments in personal area networks, IC technology, DSP processing and bio-medical devices have enabled the integration of short range communication into low cost personal health care solutions. Newer technologies and solutions are being developed to cater to the personal operating space(POS) and body area networks(BAN). Health care is driving towards using multiple sensor and therapeutic nodes inside the POS. Technology has enabled remote patient care where the patient has low cost on-body wearables that allow the patient/physician to access vital signs without the patient physically visiting the clinic. Big semiconductor giants want to move into the wearable health monitor space. Along with the developments in fitness based health wearables, there has been a lot of interest towards developing BAN devices catering to the 'mission-critical' wearables and implants. Hearing aids, EKG monitors, neurostimulators are some examples. This work explores the use of the 802.15 ulta wideband (UWB) standard for designing a radio to operate in the a wireless sensor network in the BAN. The specific application targeted is a hearing aid. However, the design in this work is capable of working in a low power low range application with the ability to have multiple data rates ranging from a few kHz to 10's of MHz. The first radio designed by Marconi using spark-gap transmitters was an impulse radio (IR). The IR UWB technology boasts of low power, low cost, high data rates, multiple channels, simultaneous networking, the ability to carry information through obstacles that more limited bandwidths cannot, and also potentially lower complexity hardware design. The inherent timing accuracy associated with the technology gives UWB transmissions immunity to multipath fading and are hence make them more suitable for a cluttered indoor environment. The key difference with the traditional narrowband transceiver is that instead of using continuous wave (CW) transmission, impulses in time are used. The timing accuracy associated with these impulses require synchronization in time, rather than synchronization in frequency for carrier-based CW systems. A complete fully integrated system is presented in thesis. This work presents a low-power noncoherent IR UWB transceiver operating at 5GHz in 0.13um CMOS. A fully-digital transmitter generates a shaped output pulse of 1GHz 3-dB bandwidth. DLLs provide a PVT-tolerant time-step resolution of 1ns over the entire symbol period and regulate the pulse generator center frequency. The transmitter outputs -31dBm (0.88pJ/pulse at 1Mpulse/s) with a dynamic (energy) efficiency of 16pJ/pulse. The transmit out pulse is FCC part 15 compliant over process voltage and temperature (PVT) variations. The transmitter is semi-compliant with IEEE 802.15.6 and IEEE 802.15.4 standards and will become completely compliant with minor modifications. The receiver presented in this work is a non-coherent energy detect IR UWB receiver. The receiver has an on-chip transformer preceding the LNA, which is followed by a super-regenerative amplifier (SRA), envelope detector, sample-and-holds, and a bank of comparators. The design is SRA based energy-detection receiver. Measured results show a receiver efficiency of 0.32nJ/bit at 20.8Mb/s and operation with inputs as low as -70dBm. The SRA based energy-detection receiver utilizes early/late detection for a two-step baseband synchronization algorithm. An integrated solution to the issue of synchronization is also proposed. The system proposed is capable of synchronization and tracking control. The system in this work utilizes early/late detection for a two-step baseband synchronization algorithm. The algorithm is implemented in Matlab and the time to synchronization is observed to be between 250us to a few couple of ms. Measurements have also been made using the receiver and manually implementing the algorithm. This work addresses all aspects time synchronization in an IR transceiver. The initial mismatch is addressed by two methods. Beyond the initial synchronization, the system presented in this system is also capable of tracking. This would mean that once the transceiver has been synchronized, the timing generation would continue to track the phase and the frequency changes depending upon crystal drift over time or movement between the receiver and the transmitter. A test was also performed on the complete transceiver system with two radios talking to each other over a highly attenuated wired channel

Measurement and characterization of ultra-wideband wireless interconnects within active computing systems

Ultra-wideband (UWB) radio has become an attractive alternative for wireless communications due to the robustness to multipath fading, low power transmission, mostly-digital implementation, and low cost. Furthermore, short-range, high data-rates applications are possible with UWB radios due to the wide spectral allocations at 3.1 - 10.6 GHz. This thesis presents experimental measurements of UWB wireless interconnects within an operational computer system chassis. The purpose of the thesis is to analyze and verify the implementation of high-bandwidth wireless communications using an impulse-radio ultra-wideband (IR-UWB) 3.1 - 5 GHz transceiver within an enclosed, heavy multipath, metallic environment such as a computer server chassis. Bit-error-rate (BER) and recovered clock jitter were measured at various positions within the computer chassis. The results show a 6X improvement in BER after applying the equalizer to the noisy channel while the motherboard is fully operating