707 research outputs found
Free Level Threshold Zone (FLTZ) Logic For Mixed Analog-Digital Closed Loop Circuitry [TK7887.6. N335 2008 f rb].
Para penyelidik sentiasa mencari cara-cara penambahbaikan kaedah antara muka antara domain Analog dan Digital.
Researchers have always look for ways to improve the interfacing method between the Analog and Digital domain
Contribution to the design of continuous -time Sigma - Delta Modulators based on time delay elements
The research carried out in this thesis is focused in the development of a new class of data converters for digital radio. There are two main architectures for communication receivers which perform a digital demodulation. One of them is based on analog demodulation to the base band and digitization of the I/Q components. Another option is to digitize the band pass signal at the output of the IF stage using a bandpass Sigma-Delta modulator. Bandpass Sigma- Delta modulators can be implemented with discrete-time circuits, using switched capacitors or continuous-time circuits. The main innovation introduced in this work is the use of passive transmission lines in the loop filter of a bandpass continuous-time Sigma-Delta modulator instead of the conventional solution with gm-C or LC resonators. As long as transmission lines are used as replacement of a LC resonator in RF technology, it seems compelling that transmission lines could improve bandpass continuous-time Sigma-Delta modulators. The analysis of a Sigma- Delta modulator using distributed resonators has led to a completely new family of Sigma- Delta modulators which possess properties inherited both from continuous-time and discretetime Sigma-Delta modulators. In this thesis we present the basic theory and the practical design trade-offs of this new family of Sigma-Delta modulators. Three demonstration chips have been implemented to validate the theoretical developments. The first two are a proof of concept of the application of transmission lines to build lowpass and bandpass modulators. The third chip summarizes all the contributions of the thesis. It consists of a transmission line Sigma-Delta modulator which combines subsampling techniques, a mismatch insensitive circuitry and a quadrature architecture to implement the IF to digital stage of a receiver
Design of sigma-delta modulators for analog-to-digital conversion intensively using passive circuits
This thesis presents the analysis, design implementation and experimental evaluation of passiveactive discrete-time and continuous-time Sigma-Delta (ÎŁÎ) modulators (ÎŁÎMs) analog-todigital converters (ADCs).
Two prototype circuits were manufactured. The first one, a discrete-time 2nd-order ÎŁÎM, was designed in a 130 nm CMOS technology. This prototype confirmed the validity of the ultra incomplete settling (UIS) concept used for implementing the passive integrators. This circuit, clocked at 100 MHz and consuming 298 ÎŒW, achieves DR/SNR/SNDR of 78.2/73.9/72.8 dB, respectively, for a signal bandwidth of 300 kHz. This results in a Walden FoMW of 139.3 fJ/conv.-step and Schreier FoMS of 168 dB.
The final prototype circuit is a highly area and power efficient ÎŁÎM using a combination of a cascaded topology, a continuous-time RC loop filter and switched-capacitor feedback paths. The modulator requires only two low gain stages that are based on differential pairs. A systematic design methodology based on genetic algorithm, was used, which allowed decreasing the circuitâs sensitivity to the circuit componentsâ variations. This continuous-time, 2-1 MASH ÎŁÎM has been designed in a 65 nm CMOS technology and it occupies an area of just 0.027 mm2. Measurement results show that this modulator achieves a peak SNR/SNDR of 76/72.2 dB and DR of 77dB for an input signal bandwidth of 10 MHz, while dissipating 1.57 mW from a 1 V power supply voltage. The ÎŁÎM achieves a Walden FoMW of 23.6 fJ/level and a Schreier FoMS of 175 dB. The innovations proposed in this circuit result, both, in the reduction of the power consumption and of the chip size. To the best of the authorâs knowledge the circuit achieves the lowest Walden FOMW for ÎŁÎMs operating at signal bandwidth from 5 MHz to 50 MHz reported to date
High Performance Integrated Circuit Blocks for High-IF Wideband Receivers
Due to the demand for highâperformance radio frequency (RF) integrated circuit
design in the past years, a systemâonâchip (SoC) that enables integration of analog and
digital parts on the same die has become the trend of the microelectronics industry. As
a result, a major requirement of the next generation of wireless devices is to support
multiple standards in the same chipâset. This would enable a single device to support
multiple peripheral applications and services.
Based on the aforementioned, the traditional superheterodyne frontâend
architecture is not suitable for such applications as it would require a complete receiver
for each standard to be supported. A more attractive alternative is the highintermediate
frequency (IF) radio architecture. In this case the signal is digitalized at an
intermediate frequency such as 200MHz. As a consequence, the baseband operations,
such as downâconversion and channel filtering, become more power and area efficient
in the digital domain. Such architecture releases the specifications for most of the frontâend building blocks, but the linearity and dynamic range of the ADC become the
bottlenecks in this system. The requirements of large bandwidth, high frequency and
enough resolution make such ADC very difficult to realize. Many ADC architectures
were analyzed and ContinuousâTime Bandpass SigmaâDelta (CTâBPâÎŁÎ) architecture was
found to be the most suitable solution in the highâIF receiver architecture since they
combine oversampling and noise shaping to get fairly high resolution in a limited
bandwidth.
A major issue in continuousâtime networks is the lack of accuracy due to powervoltageâ
temperature (PVT) tolerances that lead to over 20% pole variations compared
to their discreteâtime counterparts. An optimally tuned BP ÎŁÎ ADC requires correcting
for center frequency deviations, excess loop delay, and DAC coefficients. Due to these
undesirable effects, a calibration algorithm is necessary to compensate for these
variations in order to achieve high SNR requirements as technology shrinks.
In this work, a novel linearization technique for a Wideband LowâNoise
Amplifier (LNA) targeted for a frequency range of 3â7GHz is presented. Postâlayout
simulations show NF of 6.3dB, peak S21 of 6.1dB, and peak IIP3 of 21.3dBm,
respectively. The power consumption of the LNA is 5.8mA from 2V.
Secondly, the design of a CMOS 6th order CT BPâÎŁÎ modulator running at 800
MHz for HighâIF conversion of 10MHz bandwidth signals at 200 MHz is presented. A
novel transconductance amplifier has been developed to achieve high linearity and high
dynamic range at high frequencies. A 2âbit quantizer with offset cancellation is alsopresented. The sixthâorder modulator is implemented using 0.18 um TSMC standard
analog CMOS technology. Postâlayout simulations in cadence demonstrate that the
modulator achieves a SNDR of 78 dB (~13 bit) performance over a 14MHz bandwidth.
The modulatorâs static power consumption is 107mW from a supply power of ± 0.9V.
Finally, a calibration technique for the optimization of the Noise Transfer
Function CT BP ÎŁÎ modulators is presented. The proposed technique employs two test
tones applied at the input of the quantizer to evaluate the noise transfer function of
the ADC, using the capabilities of the Digital Signal Processing (DSP) platform usually
available in mixedâmode systems. Once the ADC output bit stream is captured,
necessary information to generate the control signals to tune the ADC parameters for
best SignalâtoâQuantization Noise Ratio (SQNR) performance is extracted via Leastâ
Mean Squared (LMS) softwareâbased algorithm. Since the two tones are located
outside the band of interest, the proposed global calibration approach can be used
online with no significant effect on the inâband content
Error Correction For Automotive Telematics Systems
One benefit of data communication over the voice channel of the cellular network is to reliably transmit real-time high priority data in case of life critical situations. An important implementation of this use-case is the pan-European eCall automotive standard, which has already been deployed since 2018. This is the first international standard for mobile emergency call that was adopted by multiple regions in Europe and the world. Other countries in the world are currently working on deploying a similar emergency communication system, such as in Russia and China. Moreover, many experiments and road tests are conducted yearly to validate and improve the requirements of the system. The results have proven that the requirements are unachievable thus far, with a success rate of emergency data delivery of only 70%.
The eCall in-band modem transmits emergency information from the in-vehicle system (IVS) over the voice channel of the circuit switch real time communication system to the public safety answering point (PSAP) in case of a collision. The voice channel is characterized by the non-linear vocoder which is designed to compress speech waveforms. In addition, multipath fading, caused by the surrounding buildings and hills, results in severe signal distortion and causes delays in the transmission of the emergency information. Therefore, to reliably transmit data over the voice channels, the in-band modem modulates the data into speech-like (SL) waveforms, and employs a powerful forward error correcting (FEC) code to secure the real-time transmission.
In this dissertation, the Turbo coded performance of the eCall in-band modem is first evaluated through the adaptive white Gaussian noise (AWGN) channel and the adaptive multi-rate (AMR) voice channel. The modulation used is biorthogonal pulse position modulation (BPPM). Simulations are conducted for both the fast and robust eCall modem. The results show that the distortion added by the vocoder is significantly large and degrades the system performance. In addition, the robust modem performs better than the fast modem. For instance, to achieve a bit error rate (BER) of 10^{-6} using the AMR compression rate of 7.4 kbps, the signal-to-noise ratio (SNR) required is 5.5 dB for the robust modem while a SNR of 7.5 dB is required for the fast modem.
On the other hand, the fading effect is studied in the eCall channel. It was shown that the fading distribution does not follow a Rayleigh distribution. The performance of the in-band modem is evaluated through the AWGN, AMR and fading channel. The results are compared with a Rayleigh fading channel. The analysis shows that strong fading still exists in the voice channel after power control. The results explain the large delays and failure of the emergency data transmission to the PSAP. Thus, the eCall standard needs to re-evaluate their requirements in order to consider the impact of fading on the transmission of the modulated signals. The results can be directly applied to design real-time emergency communication systems, including modulation and coding
RF MEMS reference oscillators platform for wireless communications
A complete platform for RF MEMS reference oscillator is built to replace bulky quartz from mobile devices, thus reducing size and cost. The design targets LTE transceivers. A low phase noise 76.8 MHz reference oscillator is designed using material temperature compensated AlN-on-silicon resonator. The thesis proposes a system combining piezoelectric resonator with low loading CMOS cross coupled series resonance oscillator to reach state-of-the-art LTE phase noise specifications. The designed resonator is a two port fundamental width extensional mode resonator. The resonator characterized by high unloaded quality factor in vacuum is designed with low temperature coefficient of frequency (TCF) using as compensation material which enhances the TCF from - 3000 ppm to 105 ppm across temperature ranges of -40ËC to 85ËC. By using a series resonant CMOS oscillator, phase noise of -123 dBc/Hz at 1 kHz, and -162 dBc/Hz at 1MHz offset is achieved. The oscillatorâs integrated RMS jitter is 106 fs (10 kHzâ20 MHz), consuming 850 ÎŒA, with startup time is 250ÎŒs, achieving a Figure-of-merit (FOM) of 216 dB. Electronic frequency compensation is presented to further enhance the frequency stability of the oscillator. Initial frequency offset of 8000 ppm and temperature drift errors are combined and further addressed electronically. A simple digital compensation circuitry generates a compensation word as an input to 21 bit MASH 1 -1-1 sigma delta modulator incorporated in RF LTE fractional N-PLL for frequency compensation. Temperature is sensed using low power BJT band-gap front end circuitry with 12 bit temperature to digital converter characterized by a resolution of 0.075ËC. The smart temperature sensor consumes only 4.6 ÎŒA. 700 MHz band LTE signal proved to have the stringent phase noise and frequency resolution specifications among all LTE bands. For this band, the achieved jitter value is 1.29 ps and the output frequency stability is 0.5 ppm over temperature ranges from -40ËC to 85ËC. The system is built on 32nm CMOS technology using 1.8V IO device
Fiber Optics
Optical fibers in metrology, telecommunications, sensors, manufacturing, and health science have gained massive research interest. The number of applications is increasing at a fast pace. This book aims to present a collection of recent advances in fiber optics, addressing both fundamental and industrial applications. It covers the current progress and latest breakthroughs in emergent applications of fiber optics. The book includes five chapters on recent developments in optical fiber communications and fiber sensors, as well as the design, simulation, and fabrication of novel fiber concepts
Error Correction For Automotive Telematics Systems
One benefit of data communication over the voice channel of the cellular network is to reliably transmit real-time high priority data in case of life critical situations. An important implementation of this use-case is the pan-European eCall automotive standard, which has already been deployed since 2018. This is the first international standard for mobile emergency call that was adopted by multiple regions in Europe and the world. Other countries in the world are currently working on deploying a similar emergency communication system, such as in Russia and China. Moreover, many experiments and road tests are conducted yearly to validate and improve the requirements of the system. The results have proven that the requirements are unachievable thus far, with a success rate of emergency data delivery of only 70%.
The eCall in-band modem transmits emergency information from the in-vehicle system (IVS) over the voice channel of the circuit switch real time communication system to the public safety answering point (PSAP) in case of a collision. The voice channel is characterized by the non-linear vocoder which is designed to compress speech waveforms. In addition, multipath fading, caused by the surrounding buildings and hills, results in severe signal distortion and causes delays in the transmission of the emergency information. Therefore, to reliably transmit data over the voice channels, the in-band modem modulates the data into speech-like (SL) waveforms, and employs a powerful forward error correcting (FEC) code to secure the real-time transmission.
In this dissertation, the Turbo coded performance of the eCall in-band modem is first evaluated through the adaptive white Gaussian noise (AWGN) channel and the adaptive multi-rate (AMR) voice channel. The modulation used is biorthogonal pulse position modulation (BPPM). Simulations are conducted for both the fast and robust eCall modem. The results show that the distortion added by the vocoder is significantly large and degrades the system performance. In addition, the robust modem performs better than the fast modem. For instance, to achieve a bit error rate (BER) of 10^{-6} using the AMR compression rate of 7.4 kbps, the signal-to-noise ratio (SNR) required is 5.5 dB for the robust modem while a SNR of 7.5 dB is required for the fast modem.
On the other hand, the fading effect is studied in the eCall channel. It was shown that the fading distribution does not follow a Rayleigh distribution. The performance of the in-band modem is evaluated through the AWGN, AMR and fading channel. The results are compared with a Rayleigh fading channel. The analysis shows that strong fading still exists in the voice channel after power control. The results explain the large delays and failure of the emergency data transmission to the PSAP. Thus, the eCall standard needs to re-evaluate their requirements in order to consider the impact of fading on the transmission of the modulated signals. The results can be directly applied to design real-time emergency communication systems, including modulation and coding
Frequency-modulation control of a DC/DC current-source parallel-resonant converter
This paper proposes a frequency-modulation control scheme for a dc/dc current-source parallel-resonant converter with two possible configurations. The basic configuration comprises an external voltage loop, an internal current loop, and a frequency modulator: the voltage loop is responsible for regulating the output voltage, the current loop makes the system controllable and limits the input current, and the modulator provides robustness against variations in resonant component values. The enhanced configuration introduces the output inductor current as a feed-forward term and clearly improves the transient response to fast load changes. The theoretical design of these control schemes is performed systematically by first deriving their small-signal models and second using Bode diagram analysis. The actual performance of the proposed control schemes is experimentally validated by testing on a laboratory prototype.Peer ReviewedPostprint (author's final draft
Baseband analog front-end and digital back-end for reconfigurable multi-standard terminals
Multimedia applications are driving wireless network operators to add high-speed data services such as Edge (E-GPRS), WCDMA (UMTS) and WLAN (IEEE 802.11a,b,g) to the existing GSM network. This creates the need for multi-mode cellular handsets that support a wide range of communication standards, each with a different RF frequency, signal bandwidth, modulation scheme etc. This in turn generates several design challenges for the analog and digital building blocks of the physical layer. In addition to the above-mentioned protocols, mobile devices often include Bluetooth, GPS, FM-radio and TV services that can work concurrently with data and voice communication. Multi-mode, multi-band, and multi-standard mobile terminals must satisfy all these different requirements. Sharing and/or switching transceiver building blocks in these handsets is mandatory in order to extend battery life and/or reduce cost. Only adaptive circuits that are able to reconfigure themselves within the handover time can meet the design requirements of a single receiver or transmitter covering all the different standards while ensuring seamless inter-interoperability. This paper presents analog and digital base-band circuits that are able to support GSM (with Edge), WCDMA (UMTS), WLAN and Bluetooth using reconfigurable building blocks. The blocks can trade off power consumption for performance on the fly, depending on the standard to be supported and the required QoS (Quality of Service) leve
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