Cognitive radio (CR) is a multi-disciplinary field that makes use of knowledge from a multitude of specialties such as antenna design, circuits, systems and digital signal processing among many others. CR has emerged as an area of interest over 20 years ago and in the years since has evolved to encompass both realizable theory and physical hardware. Key among the latter are reconfigurable, software defined radios and embedded sensors that incorporate flexible parameters, allowing a CR to operate in a wide variety of electromagnetic (EM) environments. The ideal cognitive radio would be capable of adapting to a changing EM environment without any specific knowledge or direction from the operator. This would require the radio itself to be aware of the EM environment and ideally, to sense the EM environment and act upon it in a semi-autonomous or autonomous way. While most research in this field has focused on the spectrum sensing aspects of the domain, development of the above-described "ideal CR" would require that the EM environment be characterized in domains such as angular, time and polarization among others. Signal dependent parameters can also be characterized such as bandwidth and modulation. The multi-dimensionality of the environment and the signals present within entail challenges with scalability and efficiency. This work focuses on the efficient sensing of signals in the angular domain also known as direction-of-arrival (DOA). There are a multitude of ways to find a signal's DOA. All require multiple antennas connected to a single or multiple radio nodes, antennas with patterns that gather energy in a particular direction, or multiple single antenna radios. The methods that utilize multiple antennas exploit the phase and/or amplitude relationships between the antennas themselves for a signal's DOA. The principal tradeoff between DOA methods typically converges to scan time vs. number of antenna elements. For many DOA architectures, this also means a scan time tradeoff with angular resolution as well. Since fast and accurate measurements are important for characterizing a quickly changing EM environment, sensing speed becomes a key requirement in designing a CR and associated sensing architecture. In this work, we present a DOA sensing architecture suitable for use in CR systems called the Direct Space to Information Converter (DSIC). Unlike current state-of-the art DOA methods, the DSIC breaks the tradeoff between scan time and the number of antenna elements needed for a given angular resolution when compared to other DOA and beamforming architectures. By randomly modulating the received signals in space, across multiple antenna elements and taking a few, compressed sensing (CS) measurements, the DSIC is able to angularly scan a wide field of view in an order of magnitude less time than other DOA methods. These CS measurements correspond to different random perturbations of the DSIC's antenna factor and can be quantized in as little as a single bit of resolution in the DSIC's phaseshifters/vector modulators. The DSIC is able to create multiple user-specified nulls in the antenna pattern to reduce the impact of strong known interferers while also simultaneously scanning the full field of view. Additionally, the designer has the option of performing simultaneous reception or nulling while sensing. If nulling, a few different methods are available each suitable for varying EM environments and potential use cases. We show in detail the multi-disciplinary process in designing a complete end-to-end hardware solution, selecting the parameters necessary to design the DSIC as well as test and characterize it. The benefits of the DSIC are discussed and compared to the current state-of the art with an emphasis on architectures suitable for use in interferer rich environments. We demonstrate that the energy usage of the DSIC is lower than comparable CR architectures by a large factor and scales much more favorably in terms of energy and physical complexity as the number of antenna elements increase. At the conclusion of this work we also discuss future areas of exploration in extending the DSIC's capability by incorporating an ability to sense the spectrum as well as the DOA of a signal.

M.S.

Portable communication systems require, in part, high-efficiency radio frequency power amplifiers (RF PA) if battery lifetime is to be conserved. Conventional amplifier classifications and definitions are presented in a unified and concise format. The Bipolar Junction Transistor (BJT) and Metal-Semiconductor Field Effect Transistor (MESFET) are evaluated as active devices in high-efficiency RF PA designs. Two amplifier classes (class CE and class F) meet the system requirements of an 850 MHz operating frequency, a power output of 3 W, a battery supply voltage of 9 Vdc, and a sinusoidal-type signal to be amplified. Both classes are evaluated through recent research literature and simulated using the PSpice® computer simulation program. Class CE and class F are found to provide efficiencies exceeding 80 percent under the given system constraints.</p. / Master of Science

The instantaneous performance of a site diversity system is analyzed. This analysis is performed using instantaneous diversity gain (a new parameter for describing diversity performance) and the correlation coefficient. Also, a relationship between the correlation coefficient and instantaneous diversity gain was established. In addition, a review of statistical diversity gain and existing models of statistical diversity gain were also presented. Measured statistical diversity gain data from the VPI&SU site diversity experiment were also presented and compared with instantaneous diversity gain. The relationship between the correlation coefficient and instantaneous diversity gain was used to present a crude model of diversity gain. This model was compared with the model of Hodge. Margin calculations were performed to display the usefulness of instantaneous diversity gain. These were performed using the VPI&SU site diversity experiment data. / Master of Science

Wireless systems, ranging from radio to optical frequencies, typically comprise two domains: the signal path and the local oscillator (LO) path. While signal processing is conventionally performed in the signal path, more recently, techniques that exploit LO-based signal processing are becoming increasingly popular. LO-based analog signal processing can be utilized for solving fundamental problems and for improving the performance of systems in a wide variety of applications that span radio to optical frequencies. In this dissertation, I explore LO-based signal processing to enable new functionalities and enhance performance in electrical, optical, and electro-optical circuits and systems. In the electro-optical domain, I use LO-based signal processing to improve the performance of a long-range Frequency-Modulated Continuous-Wave (FMCW) Light Detection and Ranging (LiDAR) system. As laser nonlinearity degrades the performance of ranging and imaging systems, it is essential to address this problem. In this dissertation, to linearize a laser, an integrated continuous-time Electro-Optical Phase-Locked Loop (EOPLL) is presented with a loop bandwidth equal to its reference frequency. Despite the high bandwidth, the proposed system is spurless, which is enabled by using Single-Sideband (SSB) and Harmonic-Reject mixing (HRM) techniques. These techniques are explored in Phase-Locked Loop (PLL) design for the first time. These features result in less area consumption and loss associated with the optical part of the system and increase the precision and accuracy of our long-range FMCW LIDAR significantly. In the electrical domain, I use LO engineering to address some of the challenges that exist in three different electrical systems including mm-wave Multi-Input Multi-Output (MIMO) systems, ultra-low power RF systems, and wideband mm-wave systems. In the first project, to alleviate the challenge of supporting a high data rate Input/Output (I/O) interface in a large-scale tiled mm-wave MIMO array, a single-wire interface (SWI) is used in this dissertation, and a 60GHz 4-element scalable MIMO transmitter (TX) prototype is designed. In our work, we use frequency-domain multiplexing (FDM) to simultaneously support the signals of four MIMO channels. Then, in our proposed FDM, HRM is utilized to generate the different frequencies at which the various IF signals are multiplexed. This enables us to multiplex and de-multiplex the four modulated signals simultaneously to/from the single-wire using multiple phases of only one LO. The technique proposed in this research significantly reduces the number of lines needed for LO and signal routing in a massive MIMO system. The second electrical project in this dissertation targets ultra-low power receivers at RF frequency. Wake-up receivers (WURX) are integral to reducing the power consumed by the main or primary RX in ultra-low power systems. Thus, the ability to share one antenna for both RXs is essential and results in a compact hybrid system. Furthermore, linearity and sensitivity are two fundamental criteria in these RXs. In order to improve the linearity of these systems, mixer-first RX architecture can be used for both RXs. However, mixer-first architecture has some drawbacks, like low gain and high noise figure (NF), which degrade the sensitivity of the system. Here, in our research, we implement a hybrid primary RX and WURX in which, first, a Quadrature Hybrid Coupler (QHC) is used to share one antenna between the two RXs and to achieve wideband input matching. Secondly, to address the problem of sensitivity in the mixer-first structure, we exploit a LO-assisted noise-canceling technique combined with a bottom-plate capacitor mixer-first receiver. This structure exploits implicit capacitive stacking which enables us to achieve passive LO-defined voltage gain, high linearity, and a low NF. In the last electrical project in this dissertation, I present a novel frequency-interleaved (FI) channel aggregation architecture for wideband mm-wave systems that relaxes the requirements of their Analog-to-Digital/Digital-to-Analog Converters (ADC/DAC) and consequently reduces the total cost and power consumption. In our proposed architecture, the input bandwidth is channelized into four sub-channels, which are individually up/downconverted from/to baseband, where they can be digitized with multiple lower rate subconverters. We use the idea of HRM in the channelizer to simultaneously down(up)convert four sub-channels with only one LO. Four chips, including two mm-wave RX and TX chips and two baseband RX and TX chips, are designed and tested to show the functionality of the entire system as a transceiver. Finally, I conclude this dissertation with an optical project which is a Silicon Photonic (SiP) simultaneous Mode and Wavelength Division (De)Multiplexer (MWD(De)MUX) for optical frequencies at C-band. I use an advanced 3D simulation tool, RSOFT software, to design and test this novel compact SiP structure. Our circuit uses a cascade of Mode Division Multiplexer (MDM) and Wavelength Division Multiplexer (WDM) stages for (de)multiplexing. A novel phase shifter introduced and used in this work is designed using two close waveguides on a CMOS compatible SiP platform, which results in reduced loss and size compared to conventional techniques.

Wireless sensor networks are becoming important in several monitoring and sensing applications. Ultra low power consumption in the sensor nodes is important for extending the battery life of the nodes. In this dissertation, two low power BFSK receiver architectures are proposed and verified with prototype implementations in silicion. A 2.4 GHz 1 Mb/s polyphase filter (PPF) BFSK receiver demonstrates ±180 ppm frequency offset tolerance (FOT) and 40 dB adjacent channel rejection (ACR) at a modulation index (MI) of 2, with a power consumption of 1.9 mW. High FOT at low MI is achieved by a frequency-to-energy conversion architecture using PPFs without any frequency correction. The proposed hybrid topology of the PPF provides an improved ACR at reduced power. To further improve the energy efficiency, a low energy 900 MHz mixer-less BFSK receiver is designed. High gain frequency-to-amplitude conversion and better sensitivity is achieved by a linear amplifier with Q-enhanced LC tank, eliminating the need for local oscillators and mixers. With a power consumption of 500 μW, the receiver achieves sensitivities of -90 dBm and -76 dBm for data rates of 0.5 Mb/s and 6 Mb/s, respectively. The energy efficiency is 80 pJ/b when operating at 6 Mb/s. / Graduation date: 2013 / Access restricted to the OSU Community at author's request from March 25, 2013 - March 25, 2014

Cognitive radios have been proposed as a new technology to counteract the spectrum scarcity issue and increase the spectral efficiency. In cognitive radios, the sparse assigned frequency bands are opened to secondary users, provided that interference induced on the primary licensees is negligible. Cognitive radios are established in two steps: the radios firstly sense the available frequency bands by detecting the presence of primary users and secondly communicate using the bands that have been identified as not in use by the primary users.<p><p>In this thesis we investigate how to improve the efficiency of cognitive radio networks when multiple cognitive radios cooperate to sense the spectrum or control their interferences. A major challenge in the design of cooperating devices lays in the need for exchange of information between these devices. Therefore, in this thesis we identify three specific types of control information exchange whose efficiency can be improved. Specifically, we first study how cognitive radios can efficiently exchange sensing information with a coordinator node when the reporting channels are noisy. Then, we propose distributed learning algorithms allowing to allocate the primary network sensing times and the secondary transmission powers within the secondary network. Both distributed allocation algorithms minimize the need for information exchange compared to centralized allocation algorithms. / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished

Based on different sampling theorem, for example classic Shannon’s sampling theorem and Papoulis’ generalized sampling theorem, signals are processed by the sampling devices without loss of information. As an interface between radio receiver front-ends and digital signal processing blocks, sampling devices play a dominant role in digital radio communications. Under the concept of Software Defined Radio (SDR), radio systems are going through the second evolution that mixes analog, digital and software technologies in modern radio designs. One design goal of SDR is to put the A/D converter as close as possible to the antenna. BandPass Sampling (BPS) enables one to have an interface between the RF or the higher IF signal and the A/D converter, and it might be a solution to SDR. However, three sources of performance degradation present in BPS systems, harmful signal spectral overlapping, noise aliasing and sampling timing jitter, hinder the conventional BPS theory from practical circuit implementations. In this thesis work, Generalized Quadrature BandPass Sampling (GQBPS) is first invented and comprehensively studied with focus on the noise aliasing problem. GQBPS consists of both BPS and FIR filtering that can use either real or complex coefficients. By well-designed FIR filtering, GQBPS can also perform frequency down-conversion in addition to noise aliasing reduction. GQBPS is a nonuniform sampling method in most cases. With respect to real circuit implementations, uniform sampling is easier to be realized compared to nonuniform sampling. GQBPS has been also extended to Generalized Uniform BandPass Sampling (GUBPS). GUBPS shares the same property of noise aliasing suppression as GQBPS besides that the samples are uniformly spaced. Due to the moving average operation of FIR filtering, the effect of sampling jitter is also reduced to a certain degree in GQBPS and GUBPS. By choosing a suitable sampling rate, harmful signal spectral overlapping can be avoided. Due to the property of quadrature sampling, the “self image” problem caused by I/Q mismatches is eliminated. Comprehensive theoretical analyses and program simulations on GQBPS and GUBPS have been done based on a general mathematic model. Circuit architecture to implementing GUBPS in Switched-Capacitor circuit technique has been proposed and analyzed. To improve the selectivity at the sampling output, FIR filtering is extended by adding a 1st order complex IIR filter in the implementation. GQBPS and GUBPS operate in voltage-mode. Besides voltage sampling, BPS can also be realized by charge sampling in current-mode. Most other research groups in this area are focusing on bandpass charge sampling. However, the theoretical analysis shows that our GQBPS and GUBPS in voltage mode are more efficient to suppress noise aliasing as compared to bandpass charge sampling with embedded filtering. The aliasing bands of sampled-data spectrum are always weighted by continuous-frequency factors for bandpass charge sampling with embedded filtering while discrete-frequency factors for GQBPS and GUBPS. The transmission zeros of intrinsic filtering will eliminate the corresponding whole aliasing bands of both signal and noise in GQBPS and GUBPS, while it will only cause notches at a limited set of frequencies in bandpass charge sampling. In addition, charge sampling performs an intrinsic continuous-time sinc function that always includes lowpass filtering. This is a drawback for a bandpass input signal. / QC 20100921

Orientador: Carlos Alberto dos Reis Filho / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-12T22:43:50Z (GMT). No. of bitstreams: 1 Thiebaut_MatthieuJacquesAndre_M.pdf: 11116037 bytes, checksum: 353c725fb0cc60a33445209f0ec29a81 (MD5) Previous issue date: 2006 / Resumo: O objetivo deste trabalho é propor uma topologia de receptor adequada para atender as exigências de uma rede de sensores sem fio, onde baixo consumo e baixo custo de fabricação são fundamentais.A topologia escolhida foi a do receptor super-regenerativo realizado em tecnologia CMOS 0,35Km e operando em 900 MHz. O chip foi montado e testado numa placa de alumina junto com alguns componentes passivos externos (circuito tanque e adaptação de impedância) necessários para seu funcionamento. Uma sensibilidade de -82 dBm para uma taxa de erro binário (BER) inferior a 0,1% foi obtida com um sinal modulado tudo-ou-nada (On-Off keying, OOK) de 64 kbits/s. O consumo deste receptor foi de 2,5 mW para uma tensão de alimentação de 2V. / Abstract: The purpose of this work is to develop a radio receiver, which is suitable for application in wireless sensor networks. Among the essential requirements for one such radio are included low power, low cost and high sensitivity. The topology of a super-regenerative receiver to operate in 900MHz was chosen, since it complies with all these requirements in addition to being appropriate for integration. Samples of the developed radio receiver were fabricated in 0,35Km CMOS technology. Prototypes were assembled on alumina plate using a few additional external components as an alternative to evaluate the performance of the radio without being affected by the low quality of the passives L and C used in the tuning block (tank and matching circuit). Test results have shown that the developed receiver features sensitivity of -82 dBm for a bit error rate (BER) lower than 0,1% with an On-Off Keying modulated signal of 64 kbit/s. Measure power consumption has been 2,5 mW for a supply voltage of 2 V. / Mestrado / Eletrônica, Microeletrônica e Optoeletrônica / Mestre em Engenharia Elétrica

Thesis (M.S.)-- Air Force Institute of Technology. / The original document contains color images.