93 research outputs found

    A wide dynamic range high-q high-frequency bandpass filter with an automatic quality factor tuning scheme

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    An 80 MHz bandpass filter with a tunable quality factor of 16∼44 using an improved transconductor circuit is presented. A noise optimized biquad structure for high-Q, high- frequency bandpass filter is proposed. The quality factor of the filter is tuned using a new quality factor locked loop algorithm. It was shown that a second-order quality factor locked loop is necessary and sufficient to tune the quality factor of a bandpass filter with zero steady state error. The accuracy, mismatch, and sensitivty analysis of the new tuning scheme was performed and analyzed. Based on the proposed noise optimized filter structure and new quality factor tuning scheme, a biquad filter was designed and fabricated in 0.25 μm BiCMOS process. The measured results show that the biquad filter achieves a SNR of 45 dB at IMD of 40 dB. The P-1dB compression point and IIP3 of the filter are -10 dBm and -2.68 dBm, respectively. The proposed biquad filter and quality factor tuning scheme consumes 58mW and 13 mW of power at 3.3 V supply.Ph.D.Committee Chair: Allen Phillip; Committee Member: Hasler Paul; Committee Member: Keezer David; Committee Member: Kenny James; Committee Member: Pan Ronghu

    Design for testability of high-order OTA-C filters

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    Copyright © 2016 John Wiley & Sons, Ltd.A study of oscillation-based test for high-order Operational Transconductance Amplifier-C (OTA-C) filters is presented. The method is based on partition of a high-order filter into second-order filter functions. The opening Q-loop and adding positive feedback techniques are developed to convert the second-order filter section into a quadrature oscillator. These techniques are based on an open-loop configuration and an additional positive feedback configuration. Implementation of the two testability design methods for nth-order cascade, IFLF and leapfrog (LF) filters is presented, and the area overhead of the modified circuits is also discussed. The performances of the presented techniques are investigated. Fourth-order cascade, inverse follow-the-leader feedback (IFLF) and LF OTA-C filters were designed and simulated for analysis of fault coverage using the adding positive feedback method based on an analogue multiplexer. Simulation results show that the oscillation-based test method using positive feedback provides high fault coverage of around 97%, 96% and 95% for the cascade, IFLF and LF OTA-C filters, respectively. Copyright ÂPeer reviewe

    Communication Subsystems for Emerging Wireless Technologies

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    The paper describes a multi-disciplinary design of modern communication systems. The design starts with the analysis of a system in order to define requirements on its individual components. The design exploits proper models of communication channels to adapt the systems to expected transmission conditions. Input filtering of signals both in the frequency domain and in the spatial domain is ensured by a properly designed antenna. Further signal processing (amplification and further filtering) is done by electronics circuits. Finally, signal processing techniques are applied to yield information about current properties of frequency spectrum and to distribute the transmission over free subcarrier channels

    Design of high frequency transconductor ladder filters

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    Practical realization of electronically adjustable universal filter using commercially available IC-based VBDA

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    This paper describes the practical realization of electronically adjustable voltage-mode universal filter with three inputs and single output (TISO) using the commercially available integrated circuit (IC)-based voltage differencing buffered amplifiers (VDBAs). The realization is resistor-less and contains only two VDBAs and two capacitors. The described filter structure can realize all the five standard biquadratic filter functions from the same configuration without needing any component matching criterions. It also exhibits low-output impedance, which enables for easy cascading in voltage-mode operation. Owing to practical VDBA realization, the filter circuit can be easily made electronically tunable with orthogonal o-Q tuning. The effects of the VDBA non-idealities on the filter performance have been analyzed in detail. To prove the theoretical finding, the performance of the studied circuit was also experimentally measured using the operational transconductance amplifie

    Integrated realizations of reconfigurable low pass and band pass filters for wide band multi-mode receivers

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    With the explosive development of wireless communication systems the specifications of the supporting hardware platforms have become more and more demanding. According to the long term goals of the industry, future communications systems should integrate a wide variety of standards. This leads to the idea of software defined radio, implemented on fully reconfigurable hardware.Among other reconfigurable hardware blocks, suitable for the software radio concept, an outstanding importance belongs to the reconfigurable filters that are responsible for the selectivity of the system. The problematic of filtering is strictly connected to the architecture chosen for a multi-mode receiver realization. According to the chosen architecture, the filters can exhibit low pass or band pass frequency responses.The idea of reconfigurable frequency parameters has been introduced since the beginning of modern filtering applications due to the required precision of the frequency response. However, the reconfiguration of the parameters was usually done in a limited range around ideal values. The purpose of the presented research is to transform the classical filter structures with simple self-correction into fully reconfigurable filters over a wide range of frequencies. The ideal variation of the frequency parameters is continuous and consequently difficult to implement in real circuits. Therefore, it is usually sufficient to use a discrete programming template with reasonably small steps.There are several methods to implement variable frequency parameters. The most often used programming templates employ resistor and capacitor arrays, switched according to a given code. The low pass filter implementation proposed in this work uses a special switching template, optimized for a quasi-linear frequency variation over logarithmic axes. The template also includes the possibility to compensate errors caused by component tolerances and temperature. Another important topic concerns the implementation of programmable band pass filters, suitable for IF sampling receivers. The discussion is centered on the feasibility and the flexibility of different band pass filter architectures. Due to the high frequency requirements, the emphasis lays on filters that employ transconductance amplifiers and capacitors.Die rasch fortschreitende Entwicklung drahtloser Kommunikationssysteme führt zu immer anspruchsvolleren Spezifikationen der diese Systeme unterstützenden Hardwareplattformen. Zukünftige Kommunikationssysteme sollen übereinstimmend mit den längerfristigen Zielen der Industrie verschiedene Standards integrieren. Dies führt zu der Idee von vollständig rekonfigurierbarer Hardware, welche mittels Software gesteuert wird.Inmitten anderer rekonfigurierbarer Hardwareblöcke, die für das Software Radio Konzept geeignet sind, besitzen die steuerbaren Filter, welche wesentlichen Einfluss auf die Selektivität des Systems haben, eine enorme Bedeutung. Die Filterproblematik ist eng mit der gewählten Architektur der standardübergreifenden Empfängerrealisierung verknüpft. Die Filter können entsprechend der ausgesuchten Architektur Tiefpass- oder Bandpasscharakter annehmen.Die Idee rekonfigurierbarer Frequenzparameter wurde bereits mit Beginn moderner Filteranwendungen auf Grund geforderter Frequenzganggenauigkeit umgesetzt. Jedoch wurde die Parameterrekonfiguration üblicherweise nur in einem begrenzten Bereich um die Idealwerte herum vorgenommen. Das Ziel der vorgestellten Forschungsarbeit ist es, diese klassischen Filterstrukturen mit einfacher Selbstkorrektur in über große Frequenzbereiche voll rekonfigurierbare Filter zu transformieren. Idealerweise werden die Frequenzparameter kontinuierlich variiert weswegen sich die Implementierung in reellen Schaltkreisen als schwierig erweist. Deshalb ist es üblicherweise ausreichend, ein diskretes Steuerschema mit kleinen Schrittweiten zu verwenden.Es gibt verschiedene Methoden, variable Frequenzparameter zu implementieren. Die meisten Schemata verwenden Widerstands- und Kondensatorfelder, die entsprechend eines Kodes geschaltet werden. Die in dieser Arbeit vorgestellte Implementierung eines Tiefpassfilters nutzt ein spezielles Umschaltschema, welches für die quasi-lineare Frequenzvariation bei Darstellung über logarithmischen Axen optimiert wurde. Es beinhaltet weiterhin die Möglichkeit, Fehler zu kompensieren, die durch Bauelementtoleranzen und Temperaturschwankungen hervorgerufen werden.Ein weiteres interessantes Thema betrifft die Implementierung steuerbarer Bandpassfilter, die für Empfänger mit Zwischenfrequenzabtastung geeignet sind. Die Betrachtung beschränkt sich hierbei auf die Durchführbarkeit und Flexibilität verschiedener Bandpassfilterarchitekturen. Auf Grund hoher Frequenzanforderungen liegt der Schwerpunkt auf Filtern, die auf Transkonduktanzverstärkern und Kondensatoren basieren

    Speech Processing Front-end in Low-power Hardware

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    The objective of this work is to develop analog integrated circuits to serve as low-power auditory front-ends in signal processing systems. An analog front-end can be used for feature-extraction to reduce the requirements of the digital back-end, or to detect and call attention to compelling characteristics of a signal while the back-end is in sleep mode. Such a front-end should be advantageous for speech recognition, noise suppression, auditory scene analysis, hearing prostheses, biological modeling, or hardware-based event detection.;This work presents a spectral decomposition system, which consists of a bandpass filter bank with sub-band magnitude detection. The bandpass filter is low-power and each channel can be individually programmed for different quality factors and passband gains. The novel magnitude detector has a 68 decibel dynamic range, excellent tracking capability, and consumes less than a microwatt of power. The system, which was fabricated in a 0.18 micron process, consists of a 16-channel filter bank and a variety of sub-band computational elements

    System-level design and RF front-end implementation for a 3-10ghz multiband-ofdm ultrawideband receiver and built-in testing techniques for analog and rf integrated circuits

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    This work consists of two main parts: a) Design of a 3-10GHz UltraWideBand (UWB) Receiver and b) Built-In Testing Techniques (BIT) for Analog and RF circuits. The MultiBand OFDM (MB-OFDM) proposal for UWB communications has received significant attention for the implementation of very high data rate (up to 480Mb/s) wireless devices. A wideband LNA with a tunable notch filter, a downconversion quadrature mixer, and the overall radio system-level design are proposed for an 11-band 3.4-10.3GHz direct conversion receiver for MB-OFDM UWB implemented in a 0.25mm BiCMOS process. The packaged IC includes an RF front-end with interference rejection at 5.25GHz, a frequency synthesizer generating 11 carrier tones in quadrature with fast hopping, and a linear phase baseband section with 42dB of gain programmability. The receiver IC mounted on a FR-4 substrate provides a maximum gain of 67-78dB and NF of 5-10dB across all bands while consuming 114mA from a 2.5V supply. Two BIT techniques for analog and RF circuits are developed. The goal is to reduce the test cost by reducing the use of analog instrumentation. An integrated frequency response characterization system with a digital interface is proposed to test the magnitude and phase responses at different nodes of an analog circuit. A complete prototype in CMOS 0.35mm technology employs only 0.3mm2 of area. Its operation is demonstrated by performing frequency response measurements in a range of 1 to 130MHz on 2 analog filters integrated on the same chip. A very compact CMOS RF RMS Detector and a methodology for its use in the built-in measurement of the gain and 1dB compression point of RF circuits are proposed to address the problem of on-chip testing at RF frequencies. The proposed device generates a DC voltage proportional to the RMS voltage amplitude of an RF signal. A design in CMOS 0.35mm technology presents and input capacitance <15fF and occupies and area of 0.03mm2. The application of these two techniques in combination with a loop-back test architecture significantly enhances the testability of a wireless transceiver system

    Modern VLSI Analogue Filter Design: Methodology and Software Development

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    This thesis describes various approaches for the design of modern analogue filters and provides a practical filter and equaliser design aids system XFILT. The thesis begins by placing the analogue filter design technique and software into a historical and technology perspective. The evolution of the analogue filter is traced from early work, through the passive-RLC to transconductor-C and switched-current realisations. The software development in VLSI analogue filter automation is reviewed. For SC filter design, a cascade SC design approach which includes a novel pole-zero pairing method and a comprehensive comparison of SC filter realisation using different biquads are presented. Very useful guidelines for the choice of a suitable biquad structure according to the nature of the filter problem are presented. The canonical realisations of SC filter are studied. The multirate SC system design is described. Several strategies and the algorithms for multirate SC system design are proposed. In transconductor-C filter design research, the definition of a canonical ladder based transconductor-C filter is introduced, and two canonical ladder based transconductor-C filter design approaches are proposed. The ladder based transconductor-C equaliser design is also discussed. A practical video frequency transconductor-C filter and equaliser design is given to demonstrate the utility of the matrix design method and the design software. A new approach to realise exact ladder based SI filter with first and second generation memory cell has been proposed. The bilinear transformation is used in the design procedure. Eight different SI ladder based structures can be obtained for one prototype ladder. Therefore it provides SI filter designers with various circuit choices based on different requirement such as area, maximum ratio of transistor aspect ratio limit, sensitivity or noise performance. Techniques to improve dynamic range and reduce circuit parameter spread are also presented. The proposed approach is well suited for a computer compiler implementation. A suitability study of each decomposition method for different filtering applications is also carried out and a general guideline for the choice of different decomposition methods is obtained. A comparison study on SI filter sensitivity performance based on first generation and second generation memory cells is carried out. Using four filter examples, it is demonstrated that SI filters based on a second generation SI memory cell have good sensitivity performance. For SI filters based on first generation memory cells, it is shown that a high ratio of clock frequency to cutoff frequency in the lowpass case, or a high ratio of clock frequency to midband frequency in the bandpass case would introduce high sensitivity. A novel approach for SI ladder filter based on the S2I integrator is also proposed and a canonical realisation for SI filter based on S2I integrator is developed. Examination of SI equaliser design reveals that cascade structure is a better candidate than ladder based structure. Multirate SI filter system design is also studied. Finally, a very brief introduction to the assembly of the design methods in this thesis into a software package XHLT for VLSI analogue filter and equaliser design is given. The user aspects of XFILT have been discussed and various capabilities of XFILT are demonstrated. Several advanced facilities which remove traditional design limitations are illustrated. The philosophy of the system is explained. It is shown that the distinguished features of XFILT are Ease of Use. General Applicability, and Ease of Extension. The system structure is described and the graphics interface which acts both as user friendly interface and a system manager of all the software is outlined. Fabricated SC, transconductor-C, and SI filter and equaliser have been designed by using XFILT. The system is under further enhancement toward a commercial product
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