Design and Performance Evaluation of a Time Domain Microwave Imaging System

We design a time domain microwave system dedicated to medical imaging. The measurement accuracy of the system, that is, signal-to-noise ratio, due to voltage noise and timing noise, is evaluated. Particularly, the effect of coupling media on the measurement accuracy is investigated both numerically and experimentally. The results suggest that the use of suitable coupling media betters the measurement accuracy in the frequency range of interest. A signal-to-noise ratio higher than 30 dB is achievable in the range of 500 MHz to 3 GHz when the effective sampling rate is 50 Gsa/s. It is also indicated that the effect of the timing jitter on the strongest received signal is comparable to that of the voltage noise

Aika-digitaalimuunnin laajakaistaisiin aikapohjaisiin analogia-digitaalimuuntimiin

Modern deeply scaled semiconductor processes make the design of voltage-domain circuits increasingly challenging. On the contrary, the area and power consumption of digital circuits are improving with every new process node. Consequently, digital solutions are designed in place of their purely analog counterparts in applications such as analog-to-digital (A/D) conversion. Time-based analog-to-digital converters (ADC) employ digital-intensive architectures by processing analog quantities in time-domain. The quantization step of the time-based A/D-conversion is carried out by a time-to-digital converter (TDC). A free-running ring oscillator -based TDC design is presented for use in wideband time-based ADCs. The proposed architecture aims to maximize time resolution and full-scale range, and to achieve error resilient conversion performance with minimized power and area consumptions. The time resolution is maximized by employing a high-frequency multipath ring oscillator, and the full-scale range is extended using a high-speed gray counter. The error resilience is achieved by custom sense-amplifier -based sampling flip-flops, gray coded counter and a digital error correction algorithm for counter sampling error correction. The implemented design achieves up to 9-bit effective resolution at 250 MS/s with 4.3 milliwatt power consumption.Modernien puolijohdeteknologioiden skaalautumisen seurauksena jännitetason piirien suunnittelu tulee entistä haasteellisemmaksi. Toisaalta digitaalisten piirirakenteiden pinta-ala sekä tehonkulutus pienenevät prosessikehityksen myötä. Tästä syystä digitaalisia ratkaisuja suunnitellaan vastaavien puhtaasti analogisien rakenteiden tilalle. Analogia-digitaalimuunnos (A/D-muunnos) voidaan toteuttaa jännitetason sijaan aikatasossa käyttämällä aikapohjaisia A/D-muuntimia, jotka ovat rakenteeltaan pääosin digitaalisia. Kvantisointivaihe aikapohjaisessa A/D-muuntimessa toteutetaan aika-digitaalimuuntimella. Työ esittelee vapaasti oskilloivaan silmukkaoskillaattoriin perustuvan aika-digitaalimuuntimen, joka on suunniteltu käytettäväksi laajakaistaisessa aikapohjaisessa A/D-muuntimessa. Esitelty rakenne pyrkii maksimoimaan muuntimen aikaresoluution sekä muunnosalueen, sekä saavuttamaan virhesietoisen muunnostoiminnan minimoidulla tehon sekä pinta-alan kulutuksella. Aikaresoluutio on maksimoitu hyödyntämällä suuritaajuista monipolkuista silmukkaoskillaattoria, ja muunnosalue on maksimoitu nopealla Gray-koodi -laskuripiirillä. Muunnosprosessin virhesietoisuus on saavutettu toteuttamalla näytteistys herkillä kiikkuelementeillä, hyödyntämällä Gray-koodattua laskuria, sekä jälkiprosessoimalla laskurin näytteistetyt arvot virheenkorjausalgoritmilla. Esitelty muunnintoteutus saavuttaa 9 bitin efektiivisen resoluution 250 MS/s näytetaajuudella ja 4.3 milliwatin tehonkulutuksella

Ultra wideband communication link

Ultra-wideband communication (UWB) has been a topic of extensive research in recent years especially for its short-range communication and indoor applications. The preliminary objective of the project was to develop a description and understanding of the basic components of the communication link at microwave frequencies in order to achieve the primary objective of establishing a communication setup at a bandwidth of 2.5 GHz for testing Ultra Wideband (UWB) antennas. This was achieved with the aid of commercially available optical system which was modified for the purpose. Beginning with the generation of baseband narrow pulses with energy spanning over a broad frequency range, through multiplexing of different parallel channels carrying these pulses into a single stream, to finally capturing the received signal to understand the effect of the communication link formed; all provided basis for identifying the issues and possible solutions to establishing a reliable communication link at UWB frequency

Contribution to the design of continuous -time Sigma - Delta Modulators based on time delay elements

The research carried out in this thesis is focused in the development of a new class of data converters for digital radio. There are two main architectures for communication receivers which perform a digital demodulation. One of them is based on analog demodulation to the base band and digitization of the I/Q components. Another option is to digitize the band pass signal at the output of the IF stage using a bandpass Sigma-Delta modulator. Bandpass Sigma- Delta modulators can be implemented with discrete-time circuits, using switched capacitors or continuous-time circuits. The main innovation introduced in this work is the use of passive transmission lines in the loop filter of a bandpass continuous-time Sigma-Delta modulator instead of the conventional solution with gm-C or LC resonators. As long as transmission lines are used as replacement of a LC resonator in RF technology, it seems compelling that transmission lines could improve bandpass continuous-time Sigma-Delta modulators. The analysis of a Sigma- Delta modulator using distributed resonators has led to a completely new family of Sigma- Delta modulators which possess properties inherited both from continuous-time and discretetime Sigma-Delta modulators. In this thesis we present the basic theory and the practical design trade-offs of this new family of Sigma-Delta modulators. Three demonstration chips have been implemented to validate the theoretical developments. The first two are a proof of concept of the application of transmission lines to build lowpass and bandpass modulators. The third chip summarizes all the contributions of the thesis. It consists of a transmission line Sigma-Delta modulator which combines subsampling techniques, a mismatch insensitive circuitry and a quadrature architecture to implement the IF to digital stage of a receiver

Components for Wide Bandwidth Signal Processing in Radio Astronomy

In radio astronomy wider observing bandwidths are constantly desired for the reasons of improved sensitivity and velocity coverage. As observing frequencies move steadily higher these needs become even more pressing. In order to process wider bandwidths, components that can perform at higher frequencies are required. The chief limiting component in the area of digital spectrometers and correlators is the digitiser. This is the component that samples and quantises the bandwidth of interest for further digital processing, and must function at a sample rate of at least twice the operating bandwidth. In this work a range of high speed digitiser integrated circuits (IC) are designed using an advanced InP HBT semiconductor process and their performance limits analysed. These digitiser ICs are shown to operate at up to 10 giga-samples/s, significantly faster than existing digitisers, and a complete digitiser system incorporating one of these is designed and tested that operates at up to 4 giga-samples/s, giving 2 GHz bandwidth coverage. The digitisers presented include a novel photonic I/O digitiser which contains an integrated photonic interface and is the first digitiser device reported with integrated photonic connectivity. In the complementary area of analogue correlators the limiting component is the device which performs the multiplication operation inherent in the correlation process. A 15 GHz analogue multiplier suitable for such systems is designed and tested and a full noise analysis of multipliers in analogue correlators presented. A further multiplier design in SiGe HBT technology is also presented which offers benefits in the area of low frequency noise. In the effort to process even wider bandwidths, applications of photonics to digitisers and multipliers are investigated. A new architecture for a wide bandwidth photonic multiplier is presented and its noise properties analysed, and the use of photonics to increase the sample rate of digitisers examined

Research on low power technology by AC power supply circuits

制度:新 ; 報告番号:甲3692号 ; 学位の種類:博士(工学) ; 授与年月日:2012/9/15 ; 早大学位記番号:新6060Waseda Universit

Ultra-Low Phase Noise Microwaves from Optical Signals

Continuous-wave lasers locked to high-finesse optical reference cavities are oscillators that produce ~500 THz optical signals with unprecedented stability. Indeed, sub-femtosecond fractional frequency instability at one second averaging can now be achieved. A self-referenced femtosecond laser frequency comb (FLFC) is used as a frequency divider to provide a phase-coherent link between optical and microwave domains, dividing the frequency down to the gigahertz range while also transferring the stability of the original signal. Photodetectors then convert the optical pulses into electronic signals. The resultant 10 GHz microwave signals have ultra-low phase noise below -100 dBc/Hz at 1 Hz offset, surpassing that of traditional microwave oscillators. This new approach offers significant improvement for many applications that rely on stable microwave signals, and may even create new measurement technologies otherwise unachievable with current signal sources. In reality, fundamental and technical sources of noise in each stage of the optical-to-microwave generation process limit the ultimate achievable stability of the signal. Optical reference cavities are limited by environmental effects and thermal fluctuations, and FLFC dividers suffer from intrinsic timing jitter, amplitude noise, and limited stabilization servo bandwidth. However, it is the seemingly straightforward photodetection of optical pulses that proves to be the limiting factor in the ultimate noise floor of these signals. In this thesis, I describe the noise limitations of each part of the optical-to-microwave scheme, particularly focusing on the noise limitations of photodetection. I will give a basic representation of these photodetection noise phenomena in terms of the physical behavior of optically-generated electrons in semiconductor photodiodes. The two main photodetection noise phenomena--shot noise and amplitude-to-phase conversion--will be thoroughly characterized in the context of generation of 10 GHz low phase noise signals. Finally, I will use this characterization of photodetector noise to choose optimal photodetectors and operating conditions to realize unprecedentedly low phase noise signals with a variety of optical-to-microwave generation schemes