660 research outputs found

    A Fully-Integrated Reconfigurable Dual-Band Transceiver for Short Range Wireless Communications in 180 nm CMOS

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    © 2015 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.A fully-integrated reconfigurable dual-band (760-960 MHz and 2.4-2.5 GHz) transceiver (TRX) for short range wireless communications is presented. The TRX consists of two individually-optimized RF front-ends for each band and one shared power-scalable analog baseband. The sub-GHz receiver has achieved the maximum 75 dBc 3rd-order harmonic rejection ratio (HRR3) by inserting a Q-enhanced notch filtering RF amplifier (RFA). In 2.4 GHz band, a single-ended-to-differential RFA with gain/phase imbalance compensation is proposed in the receiver. A ΣΔ fractional-N PLL frequency synthesizer with two switchable Class-C VCOs is employed to provide the LOs. Moreover, the integrated multi-mode PAs achieve the output P1dB (OP1dB) of 16.3 dBm and 14.1 dBm with both 25% PAE for sub-GHz and 2.4 GHz bands, respectively. A power-control loop is proposed to detect the input signal PAPR in real-time and flexibly reconfigure the PA's operation modes to enhance the back-off efficiency. With this proposed technique, the PAE of the sub-GHz PA is improved by x3.24 and x1.41 at 9 dB and 3 dB back-off powers, respectively, and the PAE of the 2.4 GHz PA is improved by x2.17 at 6 dB back-off power. The presented transceiver has achieved comparable or even better performance in terms of noise figure, HRR, OP1dB and power efficiency compared with the state-of-the-art.Peer reviewe

    Low-Power Energy Efficient Circuit Techniques for Small IoT Systems

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    Although the improvement in circuit speed has been limited in recent years, there has been increased focus on the internet of things (IoT) as technology scaling has decreased circuit size, power usage and cost. This trend has led to the development of many small sensor systems with affordable costs and diverse functions, offering people convenient connection with and control over their surroundings. This dissertation discusses the major challenges and their solutions in realizing small IoT systems, focusing on non-digital blocks, such as power converters and analog sensing blocks, which have difficulty in following the traditional scaling trends of digital circuits. To accommodate the limited energy storage and harvesting capacity of small IoT systems, this dissertation presents an energy harvester and voltage regulators with low quiescent power and good efficiency in ultra-low power ranges. Switched-capacitor-based converters with wide-range energy-efficient voltage-controlled oscillators assisted by power-efficient self-oscillating voltage doublers and new cascaded converter topologies for more conversion ratio configurability achieve efficient power conversion down to several nanowatts. To further improve the power efficiency of these systems, analog circuits essential to most wireless IoT systems are also discussed and improved. A capacitance-to-digital sensor interface and a clocked comparator design are improved by their digital-like implementation and operation in phase and frequency domain. Thanks to the removal of large passive elements and complex analog blocks, both designs achieve excellent area reduction while maintaining state-of-art energy efficiencies. Finally, a technique for removing dynamic voltage and temperature variations is presented as smaller circuits in advanced technologies are more vulnerable to these variations. A 2-D simultaneous feedback control using an on-chip oven control locks the supply voltage and temperature of a small on-chip domain and protects circuits in this locked domain from external voltage and temperature changes, demonstrating 0.0066 V/V and 0.013 °C/°C sensitivities to external changes. Simple digital implementation of the sensors and most parts of the control loops allows robust operation within wide voltage and temperature ranges.PHDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/138743/1/wanyeong_1.pd

    Techniques for Wideband All Digital Polar Transmission

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    abstract: Modern Communication systems are progressively moving towards all-digital transmitters (ADTs) due to their high efficiency and potentially large frequency range. While significant work has been done on individual blocks within the ADT, there are few to no full systems designs at this point in time. The goal of this work is to provide a set of multiple novel block architectures which will allow for greater cohesion between the various ADT blocks. Furthermore, the design of these architectures are expected to focus on the practicalities of system design, such as regulatory compliance, which here to date has largely been neglected by the academic community. Amongst these techniques are a novel upconverted phase modulation, polyphase harmonic cancellation, and process voltage and temperature (PVT) invariant Delta Sigma phase interpolation. It will be shown in this work that the implementation of the aforementioned architectures allows ADTs to be designed with state of the art size, power, and accuracy levels, all while maintaining PVT insensitivity. Due to the significant performance enhancement over previously published works, this work presents the first feasible ADT architecture suitable for widespread commercial deployment.Dissertation/ThesisDoctoral Dissertation Electrical Engineering 201

    A low-power reconfigurable analog-to-digital converter

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    Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2001.Includes bibliographical references (p. 197-200).This thesis presents the concept, theory and design of a low power CMOS analog-to-digital converter that can digitize signals over a wide range of bandwidth and resolution with adaptive power consumption. The converter achieves the wide operating range by reconfiguring (1) its architecture between pipeline and delta-sigma modes (2) by varying its circuit parameters such as size of capacitors, length of pipeline, oversampling ratio, among others and (3) by varying the bias currents of the opamps in proportion with converter sampling frequency, accomplished through the use of a phase-locked loop. Target input signals for this ADC include high frequency and moderate resolution signals such as video and low I.F. in radio Receivers, low frequency and high resolution signals from seismic sensors and MEMs devices, and others that fall in between these extremes such as audio, voice and general purpose data-acquisition. This converter also incorporates several power reducing features such as thermal noise limited design, global converter chopping in the pipeline mode, opamp scaling, opamp sharing between consecutive stages in the pipeline mode, an opamp chopping technique in the delta-sigma mode, and other design techniques. The opamp chopping technique achieves faster closed-loop settling time and lower thermal noise than conventional design.(cont.) At a converter power supply at 3.3V, the converter achieves a bandwidth range of 0-10MHz over a resolution range of 6 -16 bits, and parameter reconfiguration time of 12 clock cycles. Its PLL lock range is measured at 20KHz to 40MHz. In the delta-sigma mode, it achieves a maximum SNR of 94dB and second and third harmonic distortions of 102dB and 95dB, respectively at 10MHz clock frequency, 9.4KHz bandwidth, and 17.6mW power. In the pipeline mode, it achieves a maximum DNL and INL of +/-0.55LSBs and +/-0.82LSBs, respectively, at 11-bits of resolution, at a clock frequency of 2.6MHz and 1MHz tone with 24.6mW of power.by Kush Gulati.Ph.D

    A Bang-Bang All-Digital PLL for Frequency Synthesis

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    abstract: Phase locked loops are an integral part of any electronic system that requires a clock signal and find use in a broad range of applications such as clock and data recovery circuits for high speed serial I/O and frequency synthesizers for RF transceivers and ADCs. Traditionally, PLLs have been primarily analog in nature and since the development of the charge pump PLL, they have almost exclusively been analog. Recently, however, much research has been focused on ADPLLs because of their scalability, flexibility and higher noise immunity. This research investigates some of the latest all-digital PLL architectures and discusses the qualities and tradeoffs of each. A highly flexible and scalable all-digital PLL based frequency synthesizer is implemented in 180 nm CMOS process. This implementation makes use of a binary phase detector, also commonly called a bang-bang phase detector, which has potential of use in high-speed, sub-micron processes due to the simplicity of the phase detector which can be implemented with a simple D flip flop. Due to the nonlinearity introduced by the phase detector, there are certain performance limitations. This architecture incorporates a separate frequency control loop which can alleviate some of these limitations, such as lock range and acquisition time.Dissertation/ThesisM.S. Electrical Engineering 201

    Digitally Controlled Oscillator for mm-Wave Frequencies

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    In the fifth generation of mobile communication, 5G, frequencies above 30 GHz, so-called millimeter-wave (mm-wave) frequencies are expected to play a prominent role. For the synthesis of these frequencies, the all-digital phase locked loop (ADPLL) has recently gained much attention. A core component of the ADPLL is the digitally controlled oscillator (DCO), an oscillator that tunes the frequency discretely. For good performance, the frequency steps must be made very small, while the total tuning range must be large. This thesis covers several coarse- and fine-tuning techniques for DCOs operating at mm-wave frequencies. Three previously not published fine-tuning schemes are presented: The first one tunes the second harmonic, which will, due to the Groszkowski effect, tune the fundamental tone. The second one is a current-modulation scheme, which utilizes the weak current-dependence of the capacitance of a transistor to tune the frequency. In the third one, a digital-to-analog converter (DAC) is connected to the bulk of the differential pair and tunes the frequency by setting the bulk voltage. The advantages and disadvantages of the presented tuning schemes are discussed and compared with previously reported fine-tuning schemes. Two oscillators were implemented at 86 GHz. Both oscillator use the same oscillator core and hence have the same power consumption and tuning range, 14.1 mW and 13.9%. A phase noise of -89.7 dBc/Hz and -111.4 dBc/Hz at 1 MHz and 10 MHz offset, respectively, were achieved, corresponding to a Figure-of-Merit of -178.5 dBc/Hz. The first oscillator is fine-tuned using a combination of a transformer-based fine-tuning and the current modulation scheme presented here. The achieved frequency resolution is 55 kHz, but can easily be made finer. The second oscillator utilizes the bulk bias technique to achieve its fine tuning. The fine-tuning resolution is here dependent on the resolution of the DAC; a 100μV resolution corresponds to a resolution of 50 kHz.n 2011, the global monthly mobile data usage was 0.5 exabytes, or 500 million gigabytes. In 2016, this number had increased to 7 exabytes, an increase by a factor 14 in just five years, and there are no signs of this trend slowing down. To meet the demands of the ever increasing data usage, engineers have begun to investigate the possibility to use significantly higher frequencies, 30 GHz or higher, for mobile communication than what is used today, which is 3 GHz or below. To be able to transmit and receive data at these high frequency, an oscillator capable of operating at these frequencies are required. An oscillator is an electrical circuit that generates an alternating current (a current that first goes one way, and then the other) at a specific frequency. Below is an example to illustrate to function and importance of the oscillator: Imagine driving a car and listening to the radio. Suddenly, a horrendous song starts playing from the radio, so you instantly tune to another station and find some great, smooth jazz. Satisfied, you lean back and drive on. But what exactly happened when you "tuned to another station"? What you really did was changing the frequency of the oscillator, which can be found in the radio receiver of the car. The radio receiver filters out all frequencies, except for the frequency of the local oscillator. So by setting the frequency of the local oscillator to the frequency of the desired radio channel, only this radio channel will reach the speakers of the car. Thus, the oscillator must be able to vary its frequency to any frequency that a radio station can transmit on. While an old car radio may seem like a simple example, the very same principle is used in mobile communication, even at frequencies above 30 GHz. The oscillator is also used in the same way when transmitting signals, so that the signals are transmitted on the correct frequency. The design of the local oscillator is a hot topic among radio engineers. A poorly designed oscillator will ruin the performance of the whole receiver or transmitter. This thesis covers the design of a special type of oscillators, called digital controlled oscillators or DCO, operating at 30 GHz or higher. The frequency of these oscillators are determined by a digital word (ones and zeros), instead of using an analog voltage, which is traditionally used. Digital control results in greater flexibility and higher noise-resilience, but it also means that the frequency can’t be changed continuously, but rather in discrete steps. This discrete behavior will cause noise in the receiver. To minimize this noise, the frequency steps should be minimized. In this thesis, we have proposed a DCO design, operating at 85.5 GHz, which can be tuned almost 7 % in either direction. To our knowledge, no other DCO operates at such high frequencies. In the proposed oscillators the frequency steps are only 55 kHz apart, which is so small that its effect on the radio receiver can, with a good conscience, be ignored. This is achieved with a novel technique that makes tiny, tiny changes in the current that passes through the oscillator
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