In this thesis, we consider the joint design of transceivers for a multiple access Multiple Input and Multiple Output (MIMO) system having Inter-Symbol Interference (ISI) channels. The system we consider is equipped with the Minimum Mean Square Error (MMSE) Decision-Feedback (DF) detector. Traditionally, transmitter designs for this system have been based on constraints of either the transmission power or the signal-to-interference-and-noise ratio (SINR) for each user. Here, we explore a novel perspective and examine a transceiver design which is under a fixed sum Gaussian mutual information constraint and minimizes the arithmetic mean square error of the MMSE-decision feedback detection. For this optimization problem, a closed-form solution is obtained. We prove that the optimal solution is achieved if and only if the sum mutual information is uniformly distributed over each individual user per the number of its active subchannels; i.e., user mutual information uniform distribution. Meanwhile, the Gaussian mutual information of the current user under perfect feedback for all the previous users is uniformly distributed over each individual symbol within the block signal of the user; i.e., symbol mutual information uniform distribution. The user mutual information uniform distribution is attained by successively solving a series of inverse (dual) problems of maximizing single user throughput, while the symbol mutual information uniform distribution is maintained by using the equal diagonal QRS decomposition. We also show that such uniform decomposition, in addition to minimizing the arithmetic MSE of MMSE-decision feedback detection, also has another two optimality properties: (a) Both the optimal user-detection order and symbol-detection order are natural orders in terms of signal to interference and noise ratios. (b) The free-distance for the Maximum Likelihood (ML) detector has an asymptotic behavior when the sum Gaussian mutual information tends to large. / Thesis / Master of Applied Science (MASc)

Over the past decade, infrared has attracted a considerable amount of interest as an alternative medium to radio for short-range indoor wireless local area networks. Infrared offers a number of significant advantages over its radio frequency counterpart, such as the abundance of bandwidth that is currently unregulated worldwide, the availability of low cost emitters and detectors, inherent security and resistance to multi path fading. The work presented in this thesis focuses on modulation techniques, the fundamental aim being to assess the suitability of digital pulse interval modulation (DPIM) for use in indoor optical wireless communication systems. Infrared transceivers are subject to eye safety regulations, and consequently power efficiency is an important criterion when evaluating modulation techniques. From the error probability analysis carried out on the non-distorting additive white Gaussian noise channel, it is shown that DPIM is able to trade off power efficiency against bandwidth efficiency by increasing the number of bits per symbol. Furthermore, by encoding an additional bit per symbol, DPIM can outperform pulse position modulation (PPM) both in terms of power efficiency and bandwidth efficiency when simple threshold detection is employed. Indoor optical wireless systems generally operate in the presence of intense ambient light, emanating from both natural and artificial sources. Along with contributing to the generation of shot noise, artificial ambient light sources also introduce a periodic interference signal which can have a detrimental effect on link performance. Original analysis is presented which examines the error performance of DPIM in the presence of interference from a fluorescent lamp driven by a high-frequency electronic ballast, which is potentially the most degrading source of ambient light. It is found that such interference results in an average optical power requirement that is almost independent of the bit rate. The analysis then goes on to consider the effectiveness of electrical high-pass filtering as a simple means of mitigating the effect of the interference, taking into account the baseline wander introduced by the high-pass filter. DPIM was found to be more susceptible to the effects of baseline wander compared with PPM, a finding which is supported by the original analysis carried out on the power spectral density of the scheme. Consequently, whilst electrical high-pass filtering was found to be very effective at high bit rates, significant power penalties are still incurred at low to medium bit rates. In non-directed line of sight and diffuse link configurations, multipath propagation gives rise to intersymbol interference (ISI), which must be taken into account for data rates above 10 Mbit/s. Original analysis is presented which examines the unequalized performance of DPIM in the presence of ISI. From this analysis, it is found that on any given channel, the improved bandwidth efficiency of DPIM results in lower average optical power penalties, compared with PPM. One novel technique which can be used to make DPIM more resistant to the effects of ISI is to add a guard band to each symbol, immediately following the pulse. Original contributions are presented which evaluate the effectiveness of this technique. To quantify the results obtained, analysis is also carried out on DPIM using a zero-forcing decision feedback equalizer (ZF-DFE), which represents a more traditional approach to mitigating the effects of ISI. It is shown that the guard band technique offers a similar level of performance to the ZF-DFE on all but the most severe channels, and has the advantage of reduced cost and complexity compared with implementing a ZF-DFE. To support the theoretical and simulated performance of DPIM carried out in this thesis, details are given of a prototype 2.5 Mbit/s diffuse infrared link employing 16-DPIM which has been designed and constructed. The error performance of the link is measured under a variety of ambient light conditions, and the effectiveness of electrical high-pass filtering in mitigating the resulting interference is assessed. It is shown that whilst a fluorescent lamp driven by a high frequency electronic ballast has the potential to significantly degrade link performance, the power penalty introduced by this source can be made manageable by careful selection of the high-pass filter cut-on frequency.

Radio frequency (RF) filters are one of the key building blocks in modern microelectronic digital communication systems that use a narrow frequency band with strong interferers nearby. The objective of this thesis is to explore the better DR performance of RF filters using the Q-enhanced LC filter. It takes a divide-and-conquer method by designing 1. A new simple pseudo-differential pair (PDP) for input gm stage. It is the fastest, high-linearity, low-distortion, and wide-range constant-gm design reported to date. This has been applied in the final filter tape-out and has proven to be effective experimentally. 2. A new tunable discrete inductor (TDL) to achieve two-level inductance with the same real estate that can be used to expand the filtering frequency range. This has been verified experimentally. 3. A new tunable discrete capacitor (TDC) to achieve high linearity over wide terminal voltage swing range. This has been verified through simulation. 4. A new systematic way to achieve synchronized gain, center frequency, and filtering Q tuning capability for Q-enhanced LC filters. It has been verified through simulation. In order to verify the concept, a 900 MHz filter is designed and fabricated with National Semiconductor Company (NSC)'s standard 0.18 um digital epi-substrate CMOS technology, and packaged with NSC's LLP-28. The measurement results show that with filter Q of 17 at 845 MHz, the 1 dB compression point is measured to be +4 dBm, IIP3 to be +16 dBm with a peak noise floor of -154 dB/Hz, spurious free dynamic range (SFDR) to be 71 dB. With filter Q of 70 over a 20 MHz BW, the 1 dB compression point is measured to be -9.5 dBm, IIP3 to be +7 dBm with a peak noise floor of -141 dB/Hz, SFDR to be 57 over 20 MHz BW. This filter uses between 56 and 60 mA with a power supply of 1.8 V due to the low-Q (Q~1) of inductor. It is the RF filter with the highest DR in the published literature. The DR can be even higher if inductor Q can be improved as DR is proportional to Q^2.

No description available.

<p> Recently, there has been a strong trend in medicine to use implanted electronic devices for diagnostic and/or therapeutic purposes. These devices usually involve a one- or twoway communication link, allowing communication with the implant. One revolutionary implanted system that was recently launched into the healthcare market is the wireless imaging capsule for monitoring the gastrointestinal tract. Among the application-specific design challenges of such a wireless system are the severe constraints on low power and on small physical size. Besides, the allowed power levels of signals due to in-body radiating devices are restricted to very low values due to human safety concerns. To meet the requirements of such a wireless system, highly efficient, small-size, low-power transmitting radio frequency (RF) blocks are needed. </p> <p> This thesis focuses on the design, implementation and measurements of the last two blocks in the transmitter, namely the antenna and the power amplifier (PA). Three PA circuits have been designed and measured, all of class AB topology. The first two PAs operate at 2.4 GHz, while the third is designed for 405-MHz operation. All designs are fully integrated and realized in a standard mixed-signal 0.18 ~m complementary metaloxide- semiconductor (CMOS) process. Measurement results show that at a supply voltage of 1.4 V, the circuits have a maximum drain efficiency of 32% and 40.7% for the 2.4-GHz and the 405-MHz designs, respectively, while providing an output power of 7.2 and 8 dBm to the load. These results greatly outperform similar designs in the literature, proving that class AB PAs, if properly designed, are well-suited for low-power biotelemetry application. </p> <p> A simple layout design approach was developed to minimize the parasitic effects of on-silicon interconnections that cause significant degradation in the performance of RF integrated circuits (RF ICs ). This approach was used to design the layouts of the three PA circuits presented in this work, and the approach was tested on a low-noise amplifier (LNA) operating at 5 GHz, since at such a high frequency the parasitics become more pronounced. Measurements on the LNA circuit show good agreement with simulations. </p> <p> Thus, next to allowing for optimized circuit performance, this approach can shorten the design time of RF ICs by providing very good predictions of performance characteristics. </p> <p> The last part of this thesis deals with the analysis and design of efficient in-body antennas. A study of the use of loop antennas in medical implants was conducted. Simulations and measurements have been used to characterize the radiation performance of loop antennas in terms of their radiation resistance, transmitting bandwidth and biocompatibility. At 405 MHz, the antenna has proven to be efficient in the dissipative biological tissues, to have a wide transmitting bandwidth, and a specific absorption rate (SAR) distribution that is well below the safety limits. To further verify its suitability for in-body operation, a miniature loop antenna was fabricated and measured at 405 MHz and 2.4 GHz. For measurement purposes, two body simulating chemical solutions were prepared in-house to provide the necessary radiation environment. Measurements show that small loop antennas are well matched in the medium and are thus good in-body radiators. </p> / Thesis / Master of Applied Science (MASc)

A novel transit time based analytical broadband noise model is developed and implemented for high frequency bipolar transistors. This model is applied to a complementary (npn + pnp) silicon germanium (SiGe) heterojunction bipolar transistors (HBT). A complete set of analytical equations are derived using this transit time noise model, to express the four fundamental noise parameters in terms of device parameters. A comprehensive analysis on the ac, dc and broadband noise performance of a 200 GHz SiGe HBT technology, under cryogenic temperatures, is presented. The transit time based noise model is used to analyze the RF noise behavior of the SiGe HBT down to 85 K. Significant performance gain is demonstrated in cryogenic temperatures indicating the suitability of SiGe HBT for extreme environment electronics. A sub-circuit based substrate parasitic modeling methodology, in silicon based processes, is presented. A test case low noise amplifier, operating in the 5 GHz band, is designed in a SiGe HBT process and is used to demonstrate the validity of the design methodology. A dual-band, dual-mode transceiver front end for IEEE802.11a/b/g WLAN applications, is designed in a 0.8 and #956;m SiGe HBT process. The transceiver uses a new architecture which uses an on-chip frequency doubler and a single off-chip frequency synthesizer for both the 2.4 and 5 GHz bands. The performance of the transceiver meets the specification of the IEEE802.11a/b/g standards. The work described in the dissertation significantly advances the state-of-the-art in bipolar broadband noise modeling and RF, microwave circuit design using silicon based processes. The contributions and implications of this work for future research are discussed.

In recent years, oscillators are considered as inevitable blocks in many electronic systems. They are commonly used in digital circuits to provide clocking and in analog/RF circuits of communication transceivers to support frequency conversion. Nowadays, CMOS technology is the most applicable solution for VLSI and especially for modern integrated circuits used in wireless communications. The main purpose of this project is to design a high performance voltage-controlled oscillator (LC VCO) using 65nm CMOS technology. To meet the state-of-the-art requirements, several circuit solutions have been explored and the design work ended-up with a Quadrature VCO. The circuit operates at center frequency of 2.4 GHz. The phase noise of QVCO obtained by simulation is -140 dBc/Hz at 1MHz offset frequency which is 6 dB less compared to conventional LC VCOs. The power consumption is 3.6mW and the tuning voltage can be swept from 0.2 V to 1.2 V resulting in 2.25 GHz - 2.55 GHz frequency range.

To address the various emerging standards like BluetoothTM, Home RF, Wi-fiTM (IEEE 802.11), ZigBeeTM etc., in the field of wireless communications, different transceivers have been designed to operate at various frequencies such as 450 MHz, 902-920 MHz, 2.4 GHz, all part of designated ISM band. Though, the wireless systems have become more reliable, compact and easy to develop than before, a detailed performance analysis and characterization of the devices should be done. This report details the performance analysis and characterization of a popular binary FSK transceiver TRF6901 from Texas Instruments. The performance analysis of the device is done with respect to the TRF/MSP430 demonstration and development kit.

Yes / IET Editorial: In the future communications will be pervasive in nature, allowing users access at the “touch of button” to attain any service, at any time, on any device. The future device design process requires both a reconfigurable RF front end and back end with high tuning speed, energy efficiency, excellent linearity and intelligence to maximise the “greenness” of the network. But energy efficiency and excellent linearity are the main topics that are driving the designs of future transceivers, including their efforts to minimise network contributions to climate changes such as the effect of CO2 emissions: the minimisation of these is a requirement for information and communication technology (ICT) as much as for other technologies. Recently, information and communication technologies were shown to account for 3% of global power consumption and 2% of global CO2 emissions, and hence far from insignificant. The approach towards energy conservation and CO2 reduction in future communications will require a gret deal of effort which should be targeted both at the design of energy efficient, low-complexity physical, MAC and network layers, while maintaining the required Quality of Service (QoS). There is also a need, in infrastructures, networks and user terminals, to take a more holistic approach to improving or achieving green communications, from radio operation, through functionality, up to implementation. The increasing demand for data and voice services is not the only cause for concern since energy management and conservation are now at the forefront of the political agenda. The vision of Europe 2020 is to become a smart, sustainable and inclusive economy, and as part of these priorities the EU have set forth the 20:20:20 targets, whereby greenhouse gas emissions and energy consumption should be reduced by 20% while energy from renewables should be increased by 20%.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-04-20T15:37:28Z No. of bitstreams: 1 guilhermeribeirocolen.pdf: 1980646 bytes, checksum: 55067533570f6bd2d5a1ab3288db464d (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-04-24T16:49:37Z (GMT) No. of bitstreams: 1 guilhermeribeirocolen.pdf: 1980646 bytes, checksum: 55067533570f6bd2d5a1ab3288db464d (MD5) / Made available in DSpace on 2017-04-24T16:49:37Z (GMT). No. of bitstreams: 1 guilhermeribeirocolen.pdf: 1980646 bytes, checksum: 55067533570f6bd2d5a1ab3288db464d (MD5) Previous issue date: 2012-09-06 / CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico / Esta dissertação tem como objetivo investigar, propor e analisar esquemas para reduzir a complexidade computacional de algoritmos implementados na camada física de transceptores para comunicação de dados via rede elétrica - power line communication (PLC) que são baseados em multiplexação por divisão de frequência ortogonal - orthogonal frequency division multiplexing (OFDM). Inicialmente, o Clustered-OFDM é investigado e analisado com o intuito de reduzir a complexidade computacional dos transceptores PLC. Além disto, uma relação entre complexidade computacional e desempenho é demonstrada para Clustered-OFDM e múltiplo acesso por divisão de frequência ortogonal - orthogonal frequency division multiple access (OFDMA). Os resultados computacionais quantificam a relação entre complexidade computacional e redução da capacidade do canal para o Clustered-OFDM em comparação com o OFDMA. Em seguida, é proposto e analisado um esquema Clustered-OFDM para comunicação com múltiplas entradas e múltiplas saídas - multiple-input and multiple-output (MIMO) 2×2, denominado MIMO-Clustered-OFDM, que tem como base um código de bloco espacial e temporal. Os resultados de comparações revelam que a proposta MIMO-Clustered-OFDM pode reduzir a capacidade do canal para atingir uma menor complexidade computacional, comparado ao MIMO-OFDMA. Por último, é introduzido um processo para analisar estatisticamente a degradação gerada pelo agrupamento de subportadoras contíguas para o uso de algoritmos de alocação de bits. Um estudo de caso com canais PLC revela que o critério aplicado para agrupar subportadoras contíguas pode proporcionar diferentes níveis de reduções de rendimento, bem como de outras perdas de desempenho se o tamanho do grupo é variável. / This thesis aims at investigating, proposing, and analyzing techniques to reduce the computational complexity of algorithms implemented in the physical layer of power line communication (PLC) transceivers which are based on orthogonal frequency division multiplexing (OFDM). First, the clustered-OFDM is investigated and analyzed to reduce computational complexity. Also, a trade between computational complexity and performance is demonstrated for clustered-OFDM and orthogonal frequency division multiple access (OFDMA). Performance results quantify what kind of tradeoff between computational complexity and capacity reduction can be achieved in comparison with OFDMA. Second, a clustered-OFDM scheme for 2×2 multiple input multiple output (MIMO) communication based on space time block code, named MIMO-clustered-OFDM, is proposed and analyzed. Comparison results reveal that the proposed MIMO-clustered-OFDM can trade capacity with computational complexity and can achieve lower computational complexity than MIMO-OFDMA. Third, a procedure to statistically analyze the degradation yielded by the use of granularity for grouping a set of contiguous subcarriers to be used by bitloading algorithm is introduced. A case study with PLC channels reveals that the criterion applied to group of contiguous subcarriers can offer different levels of throughput reductions and other performance losses if the size of the group is varied.