808 research outputs found
Wireless interrogation of an optically modulated resonant tunnelling diode oscillator
n this work, a resonant tunnelling diode-photo-detector based microwave oscillator is amplitude modulated using an optical signal. The modulated free running oscillator is coupled to an antenna and phase locked by a wireless carrier that allows remote extraction of the information contained in the modulation. An off-the-shelf demodulator has been used to recover the envelope of the baseband data originally contained in the optical signal. Data were successfully transmitted at a rate of 1 MSym/s with a bit error rate below 10â6
A Fully Integrated 24-GHz Eight-Element Phased-Array Receiver in Silicon
This paper reports the first fully integrated 24-GHz eight-element phased-array receiver in a SiGe BiCMOS technology. The receiver utilizes a heterodyne topology and the signal combining is performed at an IF of 4.8 GHz. The phase-shifting with 4 bits of resolution is realized at the LO port of the first down-conversion mixer. A ring LC voltage-controlled oscillator (VCO) generates 16 different phases of the LO. An integrated 19.2-GHz frequency synthesizer locks the VCO frequency to a 75-MHz external reference. Each signal path achieves a gain of 43 dB, a noise figure of 7.4 dB, and an IIP3 of -11 dBm. The eight-path array achieves an array gain of 61 dB and a peak-to-null ratio of 20 dB and improves the signal-to-noise ratio at the output by 9 dB
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 jÀnnitetason piirien suunnittelu tulee entistÀ haasteellisemmaksi. Toisaalta digitaalisten piirirakenteiden pinta-ala sekÀ tehonkulutus pienenevÀt prosessikehityksen myötÀ. TÀstÀ syystÀ digitaalisia ratkaisuja suunnitellaan vastaavien puhtaasti analogisien rakenteiden tilalle. Analogia-digitaalimuunnos (A/D-muunnos) voidaan toteuttaa jÀnnitetason sijaan aikatasossa kÀyttÀmÀllÀ aikapohjaisia A/D-muuntimia, jotka ovat rakenteeltaan pÀÀosin digitaalisia. Kvantisointivaihe aikapohjaisessa A/D-muuntimessa toteutetaan aika-digitaalimuuntimella.
Työ esittelee vapaasti oskilloivaan silmukkaoskillaattoriin perustuvan aika-digitaalimuuntimen, joka on suunniteltu kÀytettÀvÀksi laajakaistaisessa aikapohjaisessa A/D-muuntimessa. Esitelty rakenne pyrkii maksimoimaan muuntimen aikaresoluution sekÀ muunnosalueen, sekÀ saavuttamaan virhesietoisen muunnostoiminnan minimoidulla tehon sekÀ pinta-alan kulutuksella. Aikaresoluutio on maksimoitu hyödyntÀmÀllÀ suuritaajuista monipolkuista silmukkaoskillaattoria, ja muunnosalue on maksimoitu nopealla Gray-koodi -laskuripiirillÀ. Muunnosprosessin virhesietoisuus on saavutettu toteuttamalla nÀytteistys herkillÀ kiikkuelementeillÀ, hyödyntÀmÀllÀ Gray-koodattua laskuria, sekÀ jÀlkiprosessoimalla laskurin nÀytteistetyt arvot virheenkorjausalgoritmilla. Esitelty muunnintoteutus saavuttaa 9 bitin efektiivisen resoluution 250 MS/s nÀytetaajuudella ja 4.3 milliwatin tehonkulutuksella
Experimental analysis of multidimensional radio channels
In this thesis new systems for radio channel measurements including space and polarization dimensions are developed for studying the radio propagation in wideband mobile communication systems. Multidimensional channel characterization is required for building channel models for new systems capable of exploiting the spatial nature of the channel. It also gives insight into the dominant propagation mechanisms in complex radio environments, where their prediction is difficult, such as urban and indoor environments.
The measurement systems are based on the HUT/IDC wideband radio channel sounder, which was extended to enable real-time multiple output channel measurements at practical mobile speeds at frequencies up to 18Â GHz. Two dual-polarized antenna arrays were constructed for 2Â GHz, having suitable properties for characterizing the 3-D spatial radio channel at both ends of a mobile communication link. These implementations and their performance analysis are presented.
The usefulness of the developed measurement systems is demonstrated by performing channel measurements at 2Â GHz and analyzing the experimental data. Spatial channels of both the mobile and base stations are analyzed, as well as the double-directional channel that fully characterizes the propagation between two antennas. It is shown through sample results that spatial domain channel measurements can be used to gain knowledge on the dominant propagation mechanisms or verify the current assumptions. Also new statistical information about scatterer distribution at the mobile station in urban environment is presented based on extensive real-time measurements. The developed techniques and collected experimental data form a good basis for further comparison with existing deterministic propagation models and development of new spatial channel models.reviewe
Living IoT: A Flying Wireless Platform on Live Insects
Sensor networks with devices capable of moving could enable applications
ranging from precision irrigation to environmental sensing. Using mechanical
drones to move sensors, however, severely limits operation time since flight
time is limited by the energy density of current battery technology. We explore
an alternative, biology-based solution: integrate sensing, computing and
communication functionalities onto live flying insects to create a mobile IoT
platform.
Such an approach takes advantage of these tiny, highly efficient biological
insects which are ubiquitous in many outdoor ecosystems, to essentially provide
mobility for free. Doing so however requires addressing key technical
challenges of power, size, weight and self-localization in order for the
insects to perform location-dependent sensing operations as they carry our IoT
payload through the environment. We develop and deploy our platform on
bumblebees which includes backscatter communication, low-power
self-localization hardware, sensors, and a power source. We show that our
platform is capable of sensing, backscattering data at 1 kbps when the insects
are back at the hive, and localizing itself up to distances of 80 m from the
access points, all within a total weight budget of 102 mg.Comment: Co-primary authors: Vikram Iyer, Rajalakshmi Nandakumar, Anran Wang,
In Proceedings of Mobicom. ACM, New York, NY, USA, 15 pages, 201
Optimized Stage Ratio of Tapered CMOS Inverters for Minimum Power and Mismatch Jitter Product
In this paper, an optimum stage ratio (tapering factor) for a tapered CMOS inverter chain is derived to minimize the product of power dissipation and jitter variance due to device mismatch. Analysis shows that this optimum stage ratio (2.4) is lower than that of minimum delay (3.6) and minimum power-delay (6.35) product. This analysis is verified by simulation results using standard 180 nm as well as 90 nm CMOS technology. Knowledge of the optimum stage ratio helps to design low power low mismatch jitter buffers for multi phase clock generation circuits that can drive large load capacitances.\ud
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RECEIVER DESIGN AND PERFORMANCE ANALYSIS FOR COMMUNICATION CHANNELS WITH CARRIER PHASE NOISE AND FADING
Ph.DDOCTOR OF PHILOSOPH
Massive MIMO Systems with Non-Ideal Hardware: Energy Efficiency, Estimation, and Capacity Limits
The use of large-scale antenna arrays can bring substantial improvements in
energy and/or spectral efficiency to wireless systems due to the greatly
improved spatial resolution and array gain. Recent works in the field of
massive multiple-input multiple-output (MIMO) show that the user channels
decorrelate when the number of antennas at the base stations (BSs) increases,
thus strong signal gains are achievable with little inter-user interference.
Since these results rely on asymptotics, it is important to investigate whether
the conventional system models are reasonable in this asymptotic regime. This
paper considers a new system model that incorporates general transceiver
hardware impairments at both the BSs (equipped with large antenna arrays) and
the single-antenna user equipments (UEs). As opposed to the conventional case
of ideal hardware, we show that hardware impairments create finite ceilings on
the channel estimation accuracy and on the downlink/uplink capacity of each UE.
Surprisingly, the capacity is mainly limited by the hardware at the UE, while
the impact of impairments in the large-scale arrays vanishes asymptotically and
inter-user interference (in particular, pilot contamination) becomes
negligible. Furthermore, we prove that the huge degrees of freedom offered by
massive MIMO can be used to reduce the transmit power and/or to tolerate larger
hardware impairments, which allows for the use of inexpensive and
energy-efficient antenna elements.Comment: To appear in IEEE Transactions on Information Theory, 28 pages, 15
figures. The results can be reproduced using the following Matlab code:
https://github.com/emilbjornson/massive-MIMO-hardware-impairment
Sincronização de quadro e frequĂȘncia para OFDM no padrĂŁo IEEE 802.15.4g : algoritmos e implementação em hardware
Orientadores: Renato da Rocha Lopes, Eduardo Rodrigues de LimaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia ElĂ©trica e de ComputaçãoResumo: O objetivo deste trabalho Ă© propor mĂ©todos de sincronização de quadro e de frequĂȘncia de portadora para a camada fĂsica MR-OFDM do padrĂŁo IEEE 802.15.4g, começando pela pesquisa de algoritmos, passando pelas etapas de modelagem e simulação em alto nĂvel, e finalmente implementando e avaliando os mĂ©todos propostos em hardware. A sincronização de quadro Ă© o processo responsĂĄvel por detectar o inĂcio do dado transmitido, ou seja, a primeira amostra vĂĄlida do sinal de interesse. No caso de sistemas OFDM, onde o sinal transmitido Ă© composto por um ou mais sĂmbolos OFDM (cada sĂmbolo sendo composto por uma quantidade fixa de amostras), o objetivo Ă© detectar a borda ou janelamento de tais sĂmbolos OFDM, ou seja, onde começa e termina cada um deles. A sincronização de frequĂȘncia, por sua vez, consiste em estimar e compensar o erro de frequĂȘncia de portadora, causado principalmente pelo descasamento dos osciladores do transmissor e do receptor. Com base em estudos preliminares, selecionamos o algoritmo de Minn para a detecção de quadro. Para a correção de erro de frequĂȘncia, dividimos o processo em duas etapas, como Ă© geralmente proposto na literatura: primeiro, o erro de frequĂȘncia fracionĂĄrio Ă© estimado no domĂnio do tempo durante a detecção de quadro e compensado via rotação de sinal; apĂłs a conversĂŁo do domĂnio do tempo para o domĂnio da frequĂȘncia, o erro de frequĂȘncia inteiro Ă© estimado e compensado utilizando um novo e simples algoritmo que serĂĄ proposto e detalhado neste trabalho. Os algoritmos propostos foram implementados em hardware e uma plataforma de verificação baseada em FPGA foi criada para avaliar o seu desempenho. Os mĂłdulos implementados sĂŁo parte de um projeto que estĂĄ sendo desenvolvido no Instituto de Pesquisa Eldorado (Campinas) que tem como objetivo implementar em ASIC um transceptor compatĂvel com o padrĂŁo IEEE 802.15.4gAbstract: The objective of this work is proposing methods of frame and frequency synchronization for the MR-OFDM PHY of IEEE 802.15.4g standard, starting with the research of state-of-the-art algorithms, passing through modeling, high-level simulations, and finally implementing and evaluating the proposed methods in hardware. Frame synchronization is the process responsible for detecting the beginning of transmitted data and, in the case of OFDM systems, the border of each OFDM symbol, while frequency synchronization consists of estimating and compensating the Carrier Frequency Offset (CFO) caused mainly by a mismatch between the transmitter and receiver oscillators. Based on the initial studies, we selected MinnÂżs algorithm for frame detection. For the CFO correction, we split the process into two steps, as commonly proposed in the literature: first, the Fractional CFO is estimated in the time domain during the frame detection and compensated via signal rotation; after the conversion from time to frequency domain, the Integer CFO is estimated and compensated with a novel and simple algorithm that will be detailed in this work. The proposed algorithms were implemented in hardware and inserted in an FPGA-based verification platform for performance measurement. The implemented modules are part of a project that is under development at Eldorado Research Institute (Campinas) and aims to implement in ASIC a transceiver compliant to the IEEE 802.15.4g standardMestradoTelecomunicaçÔes e TelemĂĄticaMestra em Engenharia ElĂ©tric
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