Digital Zero Research Articles

A high‐efficiency power management unit with wide dynamic range for RF energy harvesting system

AbstractA high‐efficiency power management unit (PMU) with wide dynamic range for radio frequency (RF) energy harvesting system is proposed in this paper. A digital zero current switching (ZCS) and a digital maximum power point tracking (MPPT) circuits are adopted. A sub‐threshold current reference circuit and a subthreshold voltage detection circuit are proposed to reduce the power consumption of always‐on control circuits and improve the conversion efficiency at low input power. A dual‐oscillator is designed to extend the frequency range and widen the input power range with optimized power consumption under low‐end band and high‐end band, respectively. Switch size and on‐time are adjusted according to the input power, which optimizes the conversion efficiency in a wide power range. Proposed PMU is implemented in a standard 180 nm CMOS process. The post‐layout simulation results show that proposed PMU can achieve cold‐start at the input voltage of 280 mV, the power consumption to maintain the PMU is only 9.6 nW. The input power range of the PMU is 11 nW–677 μW. When the input power is 50 nW, a power conversion efficiency (PCE) of 65% is achieved, and the peak PCE can reach 93% at 23.5 μW.

Hybrid Distributed MRC With Imperfect CSI for MU-MIMO Systems

We present new results for uplink distributed MIMO with two-stage beamforming (BF). Two- and four-cluster base station layouts are considered with four BF strategies. Stage one considers analog (A) or digital (D) maximal ratio combining (MRC), with digital MRC or digital zero forcing (ZF) in stage two. We denote the resulting BF schemes as A-D, D-D, A-ZF and D-ZF. Using new analytical results for the expected signal-to-interference-plus-noise-ratio (SINR) of A-D and D-D, we show that the performance gap between these schemes increases with the number of clusters. Using novel simplifications for the A-ZF and D-ZF SINR, we show that the interference reduction of the first stage processing causes a delay of the MRC/ZF performance cross-over relative to a single-stage system. We analyze the asymptotics of A-D and D-D strategies, extending existing results for single-stage co-located processing to a distributed two-stage system. We show how the relative performance of A-D and D-D varies significantly depending on the distribution of interference among the base stations and that A-D can outperform D-D.

Thermoelectric Energy Harvesting Interface Circuit With Capacitive Bootstrapping Technique for Energy-Efficient IoT Devices

This paper presents a low-input-voltage (100 mV), low-output-voltage (500–600 mV) thermoelectric energy harvesting interface circuit for near-threshold energy-efficient Internet-of-Things (IoT) devices. The capacitive bootstrapping technique is used to generate a positive and negative bias pair for alleviating the significant conduction losses of power MOSFETs in a near-threshold operation. Internal bias voltages are automatically boosted to different levels as per the loading conditions to extend the output power range. The deployment of constant on-time digital pulse skip modulation with digital zero current detection (ZCD) achieves an ultralight load operation, and precluding a reverse current. The digital ZCD is capable of dynamically adjusting the off-time ( ${T}_{\mathrm {OFF}}$ ) of the power transistors, which vary according to the input and output voltage levels. The proposed step-up dc-dc power converter implemented using a 180 nm CMOS technology demonstrates a maximum conversion efficiency of 76.4% over a $1~{\mu }\text{W}$ – $500~{\mu }\text{W}$ load range, significantly evaluating the feasibility of the near-threshold interface circuit architecture for energy-efficient IoT devices.

Study of the padding effects in numerical reconstruction of digitally recorded holograms

The reconstruction stage in the numerical reconstruction of digitally recorded holograms, imaging process named digital holography (DH), is carried out by means of computational tools. These tools are meant to reproduce the diffraction process that a known wave undergoes as it illuminates the digitally recorded hologram by using different models of light propagation. Due to the numerical nature of these methodologies some problems in their calculation, like approximations and data cuts, prevent users from obtaining more accurate results. This work shows how enlarging the size or domain of the digitally recorded hologram with digital zeros or replicas of the digital hologram, i.e. implementing padding, the visual quality of the reconstruction is improved. On using computer generated holograms of standard test images like Lena’s picture and a USAF1951 resolution test target and the real hologram of a die, the effect of padding in the quality of the reconstructed holograms is quantified. The optimal values for the hologram enlargement are determined by measuring the differences between the reconstructed and the original images and by evaluating the processing time”.

基于数字零中频纳米位移遥测技术研究

基于数字零中频纳米位移遥测技术研究

Note: On-line weak signal detection via adaptive stochastic resonance.

We design an instrument with a novel embedded adaptive stochastic resonance (SR) algorithm that consists of a SR module and a digital zero crossing detection module for on-line weak signal detection in digital signal processing applications. The two modules are responsible for noise filtering and adaptive parameter configuration, respectively. The on-line weak signal detection can be stably achieved in seconds. The prototype instrument exhibits an advance of 20 dB averaged signal-to-noise ratio and 5 times averaged adjust R-square as compared to the input noisy signal, in considering different driving frequencies and noise levels.

Performance of a Zero Average Dynamics‐controlled buck converter using different pulse‐width modulation schemes

SummaryThe response of a digital Zero Average Dynamics (ZAD)‐controlled buck converter under the variation of its intrinsic parameters as well as the pulse‐width modulation signal is studied in detail. The multiparameter analysis presented here leads to a complete knowledge of the different dynamical scenarios exhibited by the system. Numerical results indicate that the success of the ZAD‐strategy is highly dependent on the parameter and pulse‐width modulation (PWM) combinations. Experiments are included to validate the performance inside the so‐called optimum region. Copyright © 2013 John Wiley & Sons, Ltd.

Feedforward signal prediction for accurate motion systems using digital filters

A positioning system that needs to accurately track a reference can benefit greatly from using feedforward. When using a force actuator, the feedforward needs to generate a force proportional to the reference acceleration, which can be measured by means of an accelerometer or can be created by double differentiation of the reference position.The positioning system’s response to the feedforward usually shows some delay, caused by calculation time of the digital control computer, the digital-to-analog converter that drives the actuator’s amplifier, and digital differentiation of the reference position. At higher frequencies, even a small delay causes a large tracking error. Prediction of the feedforward signal by one or two samples can reduce this error.This paper describes three methods to predict a feedforward signal over a time span of a few samples. Polynomial extrapolation of past data does not require knowledge of the signal’s properties. Sinusoidal extrapolation produces an exact prediction at a set of chosen design frequencies. Both filter types can be implemented as FIR filters. A particular form of frequency sampling filters, having digital zeros which are not each other’s conjugates, can also be used for prediction purposes. The complex filter output allows reconstruction of input signal properties and its prediction. The filters are compared with regard to their suitability for predicting feedforward signals.

A Passive All-Optical Device for 2R Regeneration Based on the Cascade of Two High-Speed Saturable Absorbers

We discuss the design and realization of a passive all-optical device for 2R regeneration based on a dual-stage of high-speed microcavity saturable absorbers, one for noise reduction of digital zeros (SA-0), and the other for noise reduction of digital ones (SA-1). The numerical and experimental results showed that by using a simple combination of SA-0 and SA-1 devices, one can obtain an intensity transfer function with a large extinction ratio improvement of low power levels and a strongly nonlinear response reducing the noise of high power levels. The amplitude and phase characterization of a 40-GHz signal transmitted by this device, obtained by frequency-resolved optical gating measurements, reveals the intensity-dependant pulse-compression effect and the low chirp introduced by this device.

Timing acquisition for low-SNR data storage channels

As magnetic data storage densities are pushed toward Tb/in/sup 2/ and beyond, advanced signal-detection algorithms are being suggested to cope with the expected lower signal-to-noise ratios (SNRs). However, at low SNR, loss of lock will frequently occur in the current timing-recovery system. This paper illustrates that inadequate timing acquisition is the major cause for loss of lock in hard disk drives. Motivated by the digital zero phase start (DZPS) technique, a digital zero frequency/phase start (DZF/PS) technique is proposed to quickly reduce the initial frequency and phase errors. Kalman filter-based acquisition can be used subsequently to fine-tune acquisition based on the buffered symbol-rate samples of a preamble readout signal. Numerical simulations show that DZF/PS can reduce preamble length significantly (when used in acquisition) compared with DZPS.

A new digital zero average current error control algorithm for inverters

Inverter performance is typically measured against its ability to produce a high fidelity output sinusoidal waveform with narrow band switching frequency and good transient response. For this purpose, pulse-width modulation techniques are used to generate the required control signals for the inverter semiconductor switches. Current control voltage-source inverters can be realized using one of the recently proposed zero average current error (ZACE) techniques based on analogue technology. A new and improved algorithm that belongs to the family of ZACE methods suitable for digital technology is proposed in this paper. Advantages include a more robust algorithm with quicker computation allowing fast response and higher switching frequency from a digital signal processor. The effectiveness of the new current control algorithm is demonstrated through simulations first. Experimental results taken from a low power laboratory prototype are also presented to verify the theoretical considerations.

Accuracy of velocity and shear rate measurements using pulsed doppler ultrasound: A comparison of signal analysis techniques

An experimental investigation was instituted to evaluate the performance of Doppler ultrasound signal processing techniques for measuring fluid velocity under well-defined flow conditions using a 10-MHz multigated pulsed ultrasound instrument. Conditions of fully developed flow in a rigid, circular tube were varied over a Reynolds number range between 500 and 8000. The velocity across the tube was determined using analog and digital zero crossing detectors and three digital spectrum estimators. Determination of the Doppler frequency from analog or digital zero crossing detectors gave accurate velocity values for laminar and moderately turbulent flow away from the wall (0.969 less than or equal to r less than or equal to 0.986). Three digital spectrum estimators, Fast Fourier Transform, Burg autoregressive method, and minimum variance method, were slightly more accurate than the zero crossing detector (0.984 less than or equal to r less than or equal to 0.994), especially at points close to the walls and with higher levels of turbulence. Steep velocity gradients and transit-time-effects from high velocities produced significantly larger errors in velocity measurement. Wall shear rate estimates were most precise when calculated using the position of the wall and two velocity points. The calculated wall shears were within 20%-30% of theoretically predicted values.

Bandpass and bandstop recursive filters with low sensitivity

In a sharp cutoff bandpass or bandstop recursive digital filter, the poles and zeros are expected to be clustered around the band edges, and in close proximity of the unit circle in the z-plane. Implementation of such filters with low sensitivity could be achieved by cascading second-order sections, with appropriate low sensitivity structures chosen for individual sections depending on the locations of the poles. An alternative approach for design and implementation of band-pass/bandstop filter with low sensitivity is shown to be based on transformation of sensitivity characteristics of a low sensitivity structure to appropriate angular regions on the unit circle. A fourth-order section of such a filter is realized with a level of sensitivity which is the same as that of the prototype second-order low-pass filter section realized with low sensitivity and with reduced number of multiplications. A few transformations along with their respective structures for transforming a prototype low-pass filter are given.

Statistical design of autoregressive-moving average digital filters

Procedures are presented for the systematic design of digital filters that contain poles and zeros. The procedures are simple, fast, and effective. All of the important algorithms are of the Levinson-type. The first key idea in the paper is that one may begin a design by posing a linear prediction problem for a stochastic sequence. The second is that a high-order "whitening" filter may be constructed for this sequence and "inverted" to yield a high-order all-pole filter whose spectrum approximates the spectrum of the stochastic sequence. The third key idea is that the all-pole filter may be used to generate consistent unit-pulse and covariance sequences for use in the Mullis-Roberts algorithm. This algorithm is then used to obtain a low-order digital filter, with poles and zeros, that approximates the high-order all-pole filter. The results demonstrate that the Mullis-Roberts algorithm, together with the design philosophy of this paper, may be used with profit to reduce filter or stochastic model complexity and to design spectrum-matching digital filters.

A Fast ADC for Pulse Height Analysis

A 256-channel analog-to-digital converter having a 10 nsec per channel digitizing rate utilizing a 100 Mc crystal controlled clock will be described. Pulse analysis is accomplished by a new technique - a sample of the input pulse is analyzed based on "crossover timing" rather than "peak detection." This technique results in better linearity and less spectrum distortion at high counting rates. The "crossover timing" also provides a means of pile-up rejection based on the input pulse shape. A flexible address control provides a means of digital zero suppression which eliminates the spectrum distortion normally present with analog zero suppression and provides an accurate, reproducible means of analyzing portions of a spectrum. In order to minimize the ADC dead time, address information is "transferred" in parallel to the memory. Immediately after transfer the ADC is "free" to accept another input pulse for analysis. The ADC was designed as a plug-in accessory to a versatile, high speed, thin film memory. The complete system provides a means for accurately accumulating data at analyzed counting rates exceeding 100,000 stored counts per second.