Guest editorial for the special issue on software-defined radio transceivers and circuits for 5G wireless communications

Yichuang Sun, Baoyong Chi, and Heng Zhang, Guest Editorial for the Special Issue on Software-Defined Radio Transceivers and Circuits for 5G Wireless Communications, published in IEEEE Transactions on Circuits and Systems II: Express Briefs, Vol. 63 (1): 1-3, January 2016, doi: https://doi.org/10.1109/TCSII.2015.2506979.Peer reviewedFinal Accepted Versio

Optimal beam forming for laser beam propagation through random media

Focusing optical beams on a target through random propagation media is very important in many applications such as free space optical communica- tions and laser weapons. Random media effects such as beam spread and scintillation can degrade the optical system\u27s performance severely. Compensation schemes are needed in these applications to overcome these random media effcts. In this research, we investigated the optimal beams for two different optimization criteria: one is to maximize the concentrated received intensity and the other is to minimize the scintillation index at the target plane. In the study of the optimal beam to maximize the weighted integrated intensity, we derive a similarity relationship between pupil-plane phase screen and extended Huygens-Fresnel model, and demonstrate the limited utility of maximizing the average integrated intensity. In the study ofthe optimal beam to minimize the scintillation index, we derive the first- and second-order moments for the integrated intensity of multiple coherent modes. Hermite-Gaussian and Laguerre-Gaussian modes are used as the coherent modes to synthesize an optimal partially coherent beam. The optimal beams demonstrate evident reduction of scintillation index, and prove to be insensitive to the aperture averaging effect

Fractionation statistics

<p>Abstract</p> <p>Background</p> <p>Paralog reduction, the loss of duplicate genes after whole genome duplication (WGD) is a pervasive process. Whether this loss proceeds gene by gene or through deletion of multi-gene DNA segments is controversial, as is the question of fractionation bias, namely whether one homeologous chromosome is more vulnerable to gene deletion than the other.</p> <p>Results</p> <p>As a null hypothesis, we first assume deletion events, on one homeolog only, excise a geometrically distributed number of genes with unknown mean <it>µ</it>, and these events combine to produce deleted runs of length l, distributed approximately as a negative binomial with unknown parameter <it>r</it>, itself a random variable with distribution <it>π</it>(·). A more realistic model requires deletion events on both homeologs distributed as a truncated geometric. We simulate the distribution of run lengths <it>l</it> in both models, as well as the underlying <it>π</it>(<it>r</it>), as a function of <it>µ</it>, and show how sampling <it>l</it> allows us to estimate <it>µ</it>. We apply this to data on a total of 15 genomes descended from 6 distinct WGD events and show how to correct the bias towards shorter runs caused by genome rearrangements. Because of the difficulty in deriving <it>π</it>(·) analytically, we develop a deterministic recurrence to calculate each <it>π</it>(<it>r</it>) as a function of <it>µ</it> and the proportion of unreduced paralog pairs.</p> <p>Conclusions</p> <p>The parameter <it>µ</it> can be estimated based on run lengths of single-copy regions. Estimates of <it>µ</it> in real data do not exclude the possibility that duplicate gene deletion is largely gene by gene, although it may sometimes involve longer segments.</p

A 0.1–5.0 GHz flexible SDR receiver with digitally assisted calibration in 65 nm CMOS

© 2017 Elsevier Ltd. All rights reserved.A 0.1–5.0 GHz flexible software-defined radio (SDR) receiver with digitally assisted calibration is presented, employing a zero-IF/low-IF reconfigurable architecture for both wideband and narrowband applications. The receiver composes of a main-path based on a current-mode mixer for low noise, a high linearity sub-path based on a voltage-mode passive mixer for out-of-band rejection, and a harmonic rejection (HR) path with vector gain calibration. A dual feedback LNA with “8” shape nested inductor structure, a cascode inverter-based TCA with miller feedback compensation, and a class-AB full differential Op-Amp with Miller feed-forward compensation and QFG technique are proposed. Digitally assisted calibration methods for HR, IIP2 and image rejection (IR) are presented to maintain high performance over PVT variations. The presented receiver is implemented in 65 nm CMOS with 5.4 mm2 core area, consuming 9.6–47.4 mA current under 1.2 V supply. The receiver main path is measured with +5 dB m/+5dBm IB-IIP3/OB-IIP3 and +61dBm IIP2. The sub-path achieves +10 dB m/+18dBm IB-IIP3/OB-IIP3 and +62dBm IIP2, as well as 10 dB RF filtering rejection at 10 MHz offset. The HR-path reaches +13 dB m/+14dBm IB-IIP3/OB-IIP3 and 62/66 dB 3rd/5th-order harmonic rejection with 30–40 dB improvement by the calibration. The measured sensitivity satisfies the requirements of DVB-H, LTE, 802.11 g, and ZigBee.Peer reviewedFinal Accepted Versio

Improved Dynamic Regret of Distributed Online Multiple Frank-Wolfe Convex Optimization

In this paper, we consider a distributed online convex optimization problem over a time-varying multi-agent network. The goal of this network is to minimize a global loss function through local computation and communication with neighbors. To effectively handle the optimization problem with a high-dimensional and structural constraint set, we develop a distributed online multiple Frank-Wolfe algorithm to avoid the expensive computational cost of projection operation. The dynamic regret bounds are established as $\mathcal{O}(T^{1-\gamma}+H_T)$ with the linear oracle number $\mathcal{O} (T^{1+\gamma})$, which depends on the horizon (total iteration number) $T$, the function variation $H_T$, and the tuning parameter $0<\gamma<1$. In particular, when the prior knowledge of $H_T$ and $T$ is available, the bound can be enhanced to $\mathcal{O} (1+H_T)$. Moreover, we illustrate the significant advantages of the multiple iteration technique and reveal a trade-off between dynamic regret bound, computational cost, and communication cost. Finally, the performance of our algorithm is verified and compared through the distributed online ridge regression problems with two constraint sets

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

© 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

A 10-b Fourth-Order Quadrature Bandpass Continuous-Time ΣΔ Modulator With 33-MHz Bandwidth for a Dual-Channel GNSS Receiver

This document is the Accepted Manuscript version of the following article: Junfeng Zhang, Yang Xu, Zehong Zhang, Yichuang Sun, Zhihua Wang, and Baoyong Chi, ‘A 10-b Fourth-Order Quadrature Bandpass Continuous-Time ΣΔ Modulator With 33-MHz Bandwidth for a Dual-Channel GNSS Receiver’, IEEE Transactions on Microwave Theory and Practice, Vol. 65 (4): 1303-1314, first published online 16 February 2017. The version of record is available online at DOI: 10.1109/TMTT.2017.266237, Published by IEEE. © 2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, 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 component of this work in other works.A fourth-order quadrature bandpass continuous-time sigma-delta modulator for a dual-channel global navigation satellite system (GNSS) receiver is presented. With a bandwidth (BW) of 33 MHz, the modulator is able to digitalize the downconverted GNSS signals in two adjacent signal bands simultaneously, realizing dual-channel GNSS reception with one receiver channel instead of two independent receiver channels. To maintain the loop-stability of the high-order architecture, any extra loop phase shifting should be minimized. In the system architecture, a feedback and feedforward hybrid architecture is used to implement the fourth-order loop-filter, and a return-to-zero (RZ) feedback after the discrete-time differential operation is introduced into the input of the final integrator to realize the excess loop delay compensation, saving a spare summing amplifier. In the circuit implementation, power-efficient amplifiers with high-frequency active feedforward and antipole-splitting techniques are employed in the active RC integrators, and self-calibrated comparators are used to implement the low-power 3-b quantizers. These power saving techniques help achieve superior figure of merit for the presented modulator. With a sampling rate of 460 MHz, current-steering digital-analog converters are chosen to guarantee high conversion speed. Implemented in only 180-nm CMOS, the modulator achieves 62.1-dB peak signal to noise and distortion ratio, 64-dB dynamic range, and 59.3-dB image rejection ratio, with a BW of 33 MHz, and consumes 54.4 mW from a 1.8 V power supply.Peer reviewe

Progress in the mechanical effects of gas solidification by hydrate in coal

Aiming at the real problems such as the occurrence of coal and gas outburst and based on the hypothesis of comprehensive action of coal and gas outburst, a method of gas hydration and solidification to prevent coal and gas outburst is proposed. The core of this method is to solidify the gas in coal seam to form gas hydrate, which can not only reduce the gas pressure, but also improve the coal strength, so as to reduce or eliminate the risk of coal and gas outburst. Based on the idea of “coal and gas outburst prevention using hydrate”, the test of gas hydrate formation in coal and the in-situ test of the mechanical property-permeability of gas hydrate bearing coal have been performed, with the numerical modeling technique of the triaxial compression of the gas hydrate bearing coal proposed. The techniques are implemented by comprehensively applying the methods of theoretical analysis, development of testing equipment, indoor test and numerical analysis. In terms of coal and gas outburst prevention, the thermodynamic and kinetic conditions of gas hydrate formation are its theoretical basis, the stable storage of gas hydrate is its technical precondition, and the reduction of gas pressure and the improvement of mechanical properties are its key measures. This paper focuses on the cross mechanics related to the gas hydrate bearing coal. The results show that: ① the theoretical framework of gas solidification technology by the hydrate method for outburst prevention has been initially formed, and the meso-mechanism of improving the mechanical characteristics of coal before and after gas hydration has been preliminarily explored by means of the numerical simulation. ② At present, it has been confirmed that the hydrate formation in coal can not only reduce the gas pressure, but also improve its mechanical properties. High saturation can obviously improve the peak strength of coal. ③ Gas hydrate formation experiences three stages: rapid, slow and stable stage. Additionally, the formation of hydrate will cause the gas seepage channel in the coal to be blocked, resulting in a decrease in its permeability. ④ High gas pressure and high CH4 concentration not only help to increase the saturation but also delay hydrate decomposition, which is conducive to the stable existence of the hydrate. However, a large number of repetitive experiments are still needed to verify the reliability of the method to build up a generalized database. By analyzing current research findings, the limitations and challenges that still exist are discussed, with further research interests pointed out

Influence of micro-particles on gas hydrate formation kinetics: Potential application to methane storage and transportation

Methane hydration is a safe, stable and environmentally friendly technology to bind and utilize excess coalbed methane gas. However, a limiting factor of the commercial application of coalbed methane hydration technology is the sluggish hydration reaction kinetics of methane hydrate formation, which needs to be improved. In this work, different micro-particle suspensions are prepared from an initial solution containing gellan gum and L-tryptophan, along with varying mass fractions of NiMnGa, Cu and carboxylated multi-walled carbon nanotubes, and their influence on the reaction kinetics in methane hydrate formation is examined. The results show that the formation of methane hydrate is enhanced by these micro-particles to varying degrees. Micro-particles show a synergistic solubilization effect with L-tryptophan and gellan gum at 6.2 MPa. The induction times of 1 wt.% NiMnGa system and 1 wt.% Cu system are the shortest. The 2 wt.% NiMnGa system has a pronounced impact on methane gas consumption, and the average gas consumption rates of the 0.1 wt.% Cu system and 1 wt.% NiMnGa system are faster. However, as the concentration of Cu micro-particles increases, both gas consumption and the average generation rate exhibits a linear decrease. This work offers valuable recommendations for choosing the experimental settings, micro-particle types and concentrations. We also lay the groundwork for the practical and sustainable application of coalbed methane storage and transportation technology employing the hydrate approach.Document Type: Original articleCited as: Wu, Q., Tang, T., Zhao, Z., Li, L., Elhefnawey, M., Zhang, B. Influence of micro-particles on gas hydrate formation kinetics: Potential application to methane storage and transportation. Advances in Geo-Energy Research, 2023, 10(3): 189-199. https://doi.org/10.46690/ager.2023.12.0