Misalignment of delay-locked loop DLL output edges creates an undesired periodicity, resulting in reference harmonic tones at the output spectrum of edge-combining DLL ECDLL -based frequency synthesizers. These spurious tones corrupt the spectral purity to an unacceptable level for wireless applications. Hence, to estimate the spurious performance of such synthesizers, exhaustive Monte Carlo MC simulations are inevitable. Based on closed-form expressions, this paper proposes a generic predictive model for harmonic spur characterization of ECDLL-based frequency synthesizers, whose prediction accuracy is independent of synthesizer design parameters and system non-idealities.
Therefore, it can replace MC method to significantly accelerate the iterative design procedure of the synthesizer, while providing comparable predictions in terms of robustness and accuracy to that of MC. Validity, accuracy, and robustness of the proposed prediction method against wide-range values of non-idealities are verified through MC simulations of both the behavioral model and transistor-level model of the synthesizer in a standard nm CMOS technology. We present the design of an integrated multiplexer and a dc clamp for the input analog interface of a high-speed video digitizer in the 1.
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The ac-coupled video signal is dc restored using a novel all-digital current-mode charge pump. An eight-input multiplexer is realized with T-switches, each containing two series-connected bootstrapped switches. A T-switchs grounding branch is merged with the pull-down end of the clamping charge pump.follow link
Time-domain analog signal processing techniques
An adaptive digital feedback loop encompassing a video analog-to-digital converter ADC controls the clamp charge pump. The bootstrapped switches have been adapted to suit the video environment, allowing on-the-fly recharging. The varying ON-resistance of the conventional bootstrapped switch is utilized to linearize the multiplexer response by canceling the effect of the nonlinear load capacitance contributed by the clamp transistors.
Under worst case conditions, the multiplexer maintains a dB spurious-free dynamic range over a range of known input video frequencies, and it reduces the second-order harmonic component upon optimization. The dc clamp provides bit precision over the full range of the video ADC and can set the dc at the target level for at most video lines.
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Synthesizable all-digital ADCs that can be designed, verified and taped out using a digital design flow are of interest due to a consequent reduction in design cost and an improved technology portability. As a step towards high performance synthesizable ADCs built using generic and low accuracy components, an ADC designed exclusively with standard digital cell library components is presented.
The proposed design is a time-mode circuit employing a VCO based multi-bit quantizer.
The ADC has first order noise-shaping due to inherent error feedback of the oscillator and sinc anti-aliasing filtering due to continuous-time sampling. The proposed architecture employs a Gray-counter based quantizer design, which mitigates the problem of partial sampling of digital data in multi-bit VCO-based quantizers. Furthermore, digital correction employing polynomial-fit estimation is proposed to correct for VCO non-linearity. The design occupies 0. The performance is comparable to that of recently reported custom designed single-ended open-loop VCO-based ADCs, while being designed exclusively with standard cells, and consuming relatively low average power of 3.
A new Vernier time-to-digital converter TDC architecture using a delay line and a chain of delay latches is proposed. The delay latches replace the functionality of one delay chain and the sample register commonly found in Vernier converters, hereby enabling power and hardware efficiency improvements.
The delay latches can be implemented using either standard or full custom cells, allowing the architecture to be implemented in field-programmable gate arrays, digital synthesized application-specific integrated circuits, or in full custom design flows.
To demonstrate the proposed concept, a 7-bit Vernier TDC has been implemented in a standard nm CMOS process with an active core size of 33 mu m x mu m. The time resolution is 5. With the advent of Internet of Things IoT it has become clear that radio-frequency RF designers have to be aware of power constraints, e. The objective of this work, one of the first systematic studies of power bounds for RF-systems, is to provide an overview and intuitive feel for how power consumption and sensitivity relates for low-power receivers.
This was done by setting up basic circuit schematics for different radio receiver architectures to find analytical expressions for their output signal-to-noise ratio including power consumption, bandwidth, sensitivity, and carrier frequency. The analytical expressions and optimizations of the circuits give us relations between dc-energy-per-bit and receiver sensitivity, which can be compared to recent published low-power receivers. The parameter set used in the analysis is meant to reflect typical values for an integrated 90 nm complementary metal-oxide-semiconductor fabrication processes, and typical small sized RF lumped components.
Class Definition for Class - ELECTRICITY: ELECTRICAL SYSTEMS AND DEVICES
In this brief, we propose how the hardware complexity of arbitrary-order digital multibit error-feedback delta-sigma modulators can be reduced. This is achieved by splitting the combinatorial circuitry of the modulators into two parts, i. The part producing modulator output is removed by utilizing a unit-element-based digital-to-analog converter. To illustrate the reduced complexity and power consumption, we compare the synthesized results with those of conventional structures.
Furthermore, it can operate at a frequency MHz higher than that of the conventional. Periodic jitter raises the harmonic spurs at frequency synthesizer output spectrum, down-converting the out-of-band interferers into the desired band and corrupting the wanted signal. This paper proposes a comprehensive behavioral model for spur characterization of edge-combining delay-locked loop DLL -based synthesizers, which includes the effects of delay mismatch, static phase error SPE , and duty cycle distortion DCD.
Based on the proposed model and utilizing Fourier series representation of DLL output phases, an analytical model which formulates the synthesizer spur-to-carrier ratio SCR is developed. Moreover, from statistical analysis of the analytical derivations, a closed-form expression for SCR is obtained, from which a spur-aware synthesizer design flow is proposed.
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Employing this flow and without Monte Carlo MC method, one can determine the required stage-delay standard deviation SD of a DLL-based synthesizer, at which a certain spurious performance demanded by a target wireless standard is satisfied. This brief analyzes the effect of capacitor variation on the design of high-resolution nonbinary-weighted successive-approximation-register analog-to-digital converters in terms of radix, conversion steps, and accuracy.
Moreover, the limitation caused by the one-side redundancy of the nonbinary-weighted network is addressed and a corresponding solution with a mathematical derivation is provided. In order to relax the mismatch requirement on the capacitor sizing while still ensuring enough linearity, a bottom-up weight calibration technique accounting for noise and offset errors is proposed, and its effectiveness is demonstrated. This calibration approach can be easily incorporated into a charge-redistribution converter without modifying its main architecture and conversion sequence.
This paper presents a new approach to design multiplierless constant rotators.
The approach is based on a combined coefficient selection and shift-and-add implementation CCSSI for the design of the rotators. First, complete freedom is given to the selection of the coefficients, i.
Second, the shift-and-add implementation uses advanced single constant multiplication SCM and multiple constant multiplication MCM techniques that lead to low-complexity multiplierless implementations. Third, the design of the rotators is done by a joint optimization of the coefficient selection and shift-and-add implementation. As a result, the CCSSI provides an extended design space that offers a larger number of alternatives with respect to previous works.
Furthermore, the design space is explored in a simple and efficient way. The proposed approach has wide applications in numerous hardware scenarios. This includes rotations by single or multiple angles, rotators in single or multiple branches, and different scaling of the outputs. Experimental results for various scenarios are provided. In all of them, the proposed approach achieves significant improvements with respect to state of the art. This paper introduces add-equalize structures for the implementation of linear-phase Nyquist th-band finite-length impulse response FIR filter interpolators and decimators.
The paper also introduces a systematic design technique for these structures based on iteratively reweighted -norm minimization. In the proposed structures, the polyphase components share common parts which leads to a considerably lower implementation complexity as compared to conventional single-stage converter structures. The complexity is comparable to that of multi-stage Nyquist structures. A main advantage of the proposed structures is that they work equally well for all integer conversion factors, thus including prime numbers which cannot be handled by the regular multi-stage Nyquist converters.
Moreover, the paper shows how to utilize the frequency-response masking approach to further reduce the complexity for sharp-transition specifications. It also shows how the proposed structures can be used to reduce the complexity for reconfigurable sampling rate converters. Several design examples are included to demonstrate the effectiveness of the proposed structures.
This paper introduces two polynomial finite-length impulse response FIR digital filter structures with simultaneously variable fractional delay VFD and phase shift VPS. The structures are reconfigurable adaptable online without redesign and do not exhibit transients when the VFD and VPS parameters are altered. The overall filters are composed of a number of fixed subfilters and a few variable multipliers whose values are determined by the desired FD and PS values. A systematic design algorithm, based on iteratively reweighted l 1 - norm minimization, is proposed.
It generates fixed subfilters with many zero-valued coefficients, typically located in the impulse response tails. The paper considers two different structures, referred to as the basic structure and common-subfilters structure, and compares these proposals as well as the existing cascaded VFD and VPS structures, in terms of arithmetic complexity, delay, memory cost, and transients.