Browsing by Subject "UWB"
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Item Fast hopping frequency synthesis techniques using injection locking.(2010-03) Lanka, NarasimhaThe use of fast-hopping frequency synthesis is a critical component of frequency-hopped spread spectrum (FHSS) systems. FHSS offers many advantages including high resistance to narrow-band interference, low probability of intercept and capability to share spectrum with other narrow-band systems. Such qualities make FHSS a particularly attractive scheme for military applications. In commercial applications, the WiMedia specification for ultra-wideband (UWB)/Wireless-USB presents another standard that uses fast frequency-hopping. The most stringent constraint on the frequency synthesizer in these systems is the band-switching time. This thesis presents novel techniques for fast-hopping frequency synthesis based on injection locking. First, extensive study of the transient behavior of oscillators under injection is presented. Analystical expressions are used as the basis for the study and interesting aspects of the locking process of an injection-locked oscillator (ILO) are identified. Two techniques, lock-range dependent fast-locking and predictive fast-locking, are then presented. In the first technique, fast locking times are achieved by using large lock-ranges for the ILO. Phase dependence of lock-time is exploited in the second technique and extremely fast settling is achieved. These theoretical findings are verified through simulation and measurements from a multiple of oscillator prototypes. Measurements from a low-speed Colpitts oscillator running at 57 MHz are used to verify tracking, out-of-lock behavior and frequency settling of ILOs. Measurements from an LC-oscillator implemented in 0.13-um CMOS technology operating at a free-running frequency of 3.4 GHz are used to verify the dependence of locking time on the lock range and the initial phase of injection. Novel architectures for fast frequency-hopping synthesizers and high frequency direct-digital synthesizer are then presented. Finally, a complete prototype for WiMedia-UWB/Wireless-USB-compliant fast-hopping frequency synthesizer architecture with quadrature outputs, based on sub-harmonic injection-locking, is presented. The synthesizer features a cross-coupled quadrature digitally-controlled oscillator, that is injection-locked to a sub-harmonic frequency. An intuitive closed-form expression for the dynamics of the quadrature injection-locked oscillator is derived. The overall design is a CMOS-only implementation and has been fabricated in 0.13-um SiGe BiCMOS process. Measurement results indicate lock-times of less than 2.5 ns, a locked phase noise of -114 dBc/Hz at 1 MHz offset and a quadrature accuracy of better than 0.5 deg. The frequency synthesizer (excluding output buffers) occupies an area of 0.27 mm2 and consumes 14.5 mW of power. The best and worst-case spur suppression achieved are 47 and 31 dB, respectively. This is the lowest power fast-hopping quadrature frequency synthesizer reported to-date.Item Ultra-Wideband Transceiver Design And Optimization(2015-07) Mehra, AshutoshThe 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.