Series/Parallel Time-Multiplexed Switched-Capacitor Filters with Programmability Based on Non-Uniform Sampling

This paper presents an improved scheme for programmable time-multiplexed (TM) switched-capacitor (SC) filters. The proposed approach uses a novel sampling technique, which eliminates the need for resolution/area tradeoffs. The programmability of each processing channel is based on the use of non-uniform clock signals with noise-shaped sampling energy. No capacitor values are modified for programming frequency response parameters and, hence, the performance of the TM SC filter is not sacrificed for programmability. Such a sampling technique not only leads to an accurate frequency response control, but also allows the design procedures and the resulting SC circuit implementation to be simplified. A test-chip including a programmable second-order TM SC filter with a multiplexing order of four, which operates in series or in parallel mode, was fabricated in conventional CMOS technology. Measurement results demonstrate the effectiveness and versatility of the proposed technique.     

基于信号流图的开关电流滤波器设计

开关电流（SI）是有望取代开关电容（SC）的一种新型的取样数据技术，鉴于SC技术发展的成熟性及其与SI技术的紧密联系，即SC和SI滤波电路具有互易性，可采用信号流图转置的方法，将SC综合法直接用于SI滤波器设计，而无须提出新的设计方法。本文以二阶巴特沃思开关电容带通滤皮器为例给出了该方法的具体应用。     

Classification of DoS Attacks in Smart Underwater Wireless Sensor Network

As per the most recent literature, Orthogonal Frequency Division Multiplexing (OFDM), a multi access technique, is considered most suitable for the 3G, 4G and 5G techniques in high speed wireless communication. What made OFDM most popular is its ability to deliver high bandwidth efficiency and superior data rate. Besides it, high value of peak to average power ratio (PAPR) and Inter Carrier Interference (ICI) are the challenges to tackle down via appropriate mitigation scheme. As a research contribution in the present work, an improved self-cancellation (SC) technique is designed and simulated through Simulink to mitigate the effect of ICI. This novel proposed technique (Improved SC) is designed over discrete wavelet transform (DWT) based OFDM and compared with conventional SC scheme over different channel conditions i.e. AWGN and Rayleigh fading environments. It is found that proposed DWT-OFDM with Improved SC scheme outperforms conventional SC technique significantly, under both AWGN and Rayleigh channel conditions. Further, in order to justify the novelty in the research contribution, a Split-DWT based Simulink model for Improved SC scheme is investigated to analyse the BER performance. This Split-DWT based Simulink model presented here foretells the future research potential in wavelet hybridization of OFDM to side-line ICI effects more efficiently.

     

Nonlinear Shaping SC Oscillator With Enhanced Linearity

A nonlinear shaping technique for a switched-capacitor (SC) bandpass filter (BPF) based oscillator yielding enhanced linearity is presented. Usually, for an SC oscillator consisting of a BPF and a two-level comparator, the linearity can only be improved by increasing the quality factor (-factor) of the BPF. This paper proposes an efficient way to improve the linearity of SC BPF-based oscillators. In particular, by replacing the conventional two-level comparator by a sound multilevel comparator, a nonlinear shaping of the signal at the output of the comparator causes a significant improvement in linearity. To illustrate the effectiveness of the proposed technique, one conventional SC BPF-based oscillator and the proposed oscillator have been designed and fabricated in a standard 0.35- CMOS technology. Each oscillator was designed to operate from a 1.65 V supply voltage and a master clock frequency of 80 MHz. The oscillation frequency is 10 MHz and the -factor of the BPF is 10. Experimental results demonstrate that the proposed scheme improves the third-order harmonic distortion by 20 dB with respect to the conventional SC BPF-based oscillator.     

单一单位增益放大器的Q增强SC滤波器

本文阐述了采用单位增益放大器的SC滤波器的设计方法。基于无源Q增强技术,由Sallew Key有源RC电路导出了一系列Q增强的二阶SC低通、高通和带通滤波器。设计表明,本文提出的Q增强SC电路比文献给出的电路需要小得多的电容分散度。本文考察了这些电路灵敏度和有限GB对SC电路的影响。用分立元件做了实验,实验结果与理论计算相吻合。     

Switched-capacitor bandpass filter with quasi-continuous digitalQ-factor tunability

A second-order switched-capacitor (SC) bandpass filter with very wide Q-factor programmability range, is presented. Although the Q-factor is controlled by digitally varying the effective sampling frequency of an SC branch, quasi-continuous programmability is provided. Experimental results from a 0.8 μm CMOS integrated prototype demonstrate the versatility of the proposed technique     

Clock feedthrough compensation with phase slope control in SCcircuits

A clock feedthrough compensation technique for SC circuits is presented. The principle is based on the control of the switch turn-off slope. A single control block can drive a large number of identical SC structures, thus minimising area overhead. Experimental results from an integrated prototype show that the injected charge is reduced by a factor as high as 13     

Iterative frequency domain channel estimation for dft-precoded ofdm systems using in-band pilots

We consider two techniques of in-band frequency domain multiplexed (FDM) pilots using interleaved frequency domain multiple access (IFDMA) signal with a Chu sequence for DFT-precoded OFDM (or single-carrier (SC)) systems. One, called frequency domain superimposed pilot technique (FDSPT), superimposes pilot tones onto scaled or deleted data tones, which preserves spectral efficiency at the expense of a slight performance loss. The other, called frequency expanding technique (FET), multiplexes pilot tones by displacing data tones, which slightly reduces spectral efficiency. Using FDM pilots in SC systems facilitates flexible and efficient assignment of signals to available spectrum. We propose an iterative frequency domain decision-directed interference cancellation technique to reduce the intersymbol interference level of SC signals with FDSPT pilots (resulting from the suppression of data tones). Moreover, we propose a low complexity frequency domain iterative decision-directed channel estimation (IDDCE) technique for SC systems using FDM pilots. Using IDDCE, the frame error rate (FER) performance for coded SC systems using FET and FDSPT pilots with interference cancellation is found to be about 0.2 dB and about 0.5 dB, respectively, away from the FER performance with known channel frequency response at FER=10^-2. FDSPT pilots can also be used for OFDM systems with channel coding. It is found that an extra 1 dB of SNR is required at FER=10^-2,compared with that using the conventional FET pilots for OFDM systems.     

By-inspection analysis of switched-capacitor networks †

The recent advances in implementation of analogue MOS switched-capacitor (SC) networks have established a need for new methods of analysis of these circuits. In this paper an analysis method of SC networks operating with an n-phase clock is presented. The method is based on a building block approach which facilitates the derivation of a z-domain equivalent circuit. The equivalent circuit is then analysed using the flow-graph technique.     

Spinal Cord Injury Detection and Monitoring Using Spectral Coherence

In this paper, spectral coherence (SC) is used to study the somatosensory evoked potential (SEP) signals in rodent model before and after spinal cord injury (SCI). The SC technique is complemented with the Basso, Beattie, and Bresnahan (BBB) behavior analysis method to help us assess the status of the motor recovery. SC can be used to follow the effects of SCI without any preinjury baseline information. In this study, adult female Fischer rats received contusion injury at T8 level with varying impact heights using the standard New York University impactor. The results show that the average SC between forelimb and hindlimb SEP signals before injury was relatively high ( ges0.7). Following injury, the SC between the forelimb and hindlimb SEP signals dropped to various levels (les0.7) corresponding to the severity of SCI. The SC analysis gave normalized quantifiable results for the evaluation of SCI and recovery thereafter using the forelimb signals as an effective control, without the need of any baseline data. This technique solves the problems associated with the commonly used time-domain analysis like the need of a trained neurophysiologist to interpret the data and the need for baseline data. We believe that both SC and BBB may provide a comprehensive and complementary picture of the health status of the spinal cord after injury. The presented method is applicable to SCIs not affecting the forelimb SEP signals.     

High-Selectivity Switched-Capacitor Bandpass Filter with Quasi-Continuous Quality Factor Tunability

This paper describes the design and implementation of a second-order switched-capacitor (SC) bandpass (BP) filter with very wide quality factor (Q) programmability range. The filter selectivity is digitally programmed by varying the effective sampling frequency of an SC branch, without modifying any capacitor value. The proposed approach allows a quasi-continuous Q-factor tunability avoiding, in principle, the inherent quantization error associated to any traditional programming technique. Automatic Q-factor tuning is performed by using a scheme based on an amplitude-locking loop approach. Experimental results obtained from a 0.8-m CMOS integrated prototype demonstrate the versatility of the proposed technique for high-Q SC BP filters.     

Selected mapping technique for reducing PAPR of single‐carrier signals

Single‐carrier transmission with frequency‐domain equalization (SC‐FDE) is widely known as a promising transmission technique providing low error probability with low peak‐to‐average power ratio (PAPR) of transmit signal. However, the low‐PAPR property of SC‐FDE cannot be maintained if multi‐level data modulation is introduced. The low‐PAPR property of SC‐FDE can be maintained by applying transmit filtering with roll‐off factor at the expense of spectrum efficiency. In this paper, we propose two types of selected mapping (SLM) to reduce the PAPR of SC‐FDE transmit signal. The first SLM technique is conducted in the frequency domain, where the phase rotation is applied to subcarriers similar to the SLM technique for orthogonal frequency division multiplexing transmission. The second SLM technique is conducted in the time domain, where the phase rotation is applied directly to data‐modulated symbol sequence. Computer simulation confirms that both SLM techniques are able to reduce the PAPR of SC‐FDE signal without significant degradation of bit‐error rate performance and spectrum efficiency. Copyright © 2016 John Wiley & Sons, Ltd.     

冲击噪声干扰下SC分集接收的系统性能分析

现实的无线通信环境不仅存在着高斯白噪声干扰,而且存在着随机冲击干扰。采用高斯混合噪声的模型,对存在冲击噪声干扰的Rayleigh信道应用选择式合并分集接收,并对MPSK系统的误码率性能做了研究和分析。仿真结果显示了系统性能与随机冲击干扰的关系,同时也证明了SC分集接收是改善无线通信系统的性能的一项有效技术。     

SC filter for RF sampling and downconversion with wideband image rejection

In this paper we present an SC filter for RF downconversion using the direct RF sampling and decimation technique. The circuit architecture is generic and it features high image rejection for wideband signals and good linearity. An SC implementation in 0.13μm CMOS suitable for an RF of 2.4 GHz and 20 MHz signal bandwidth is presented as a demonstrator. Simulation results obtained using Cadence Spectre simulation tools are included.     

Programmable CMOS switched-capacitor biquad using quasi-passivealgorithmic DAC's

This paper describes an electrically programmable switched-capacitor (SC) biquad using quasi-passive algorithmic digital-to-analog converters (DAC's). Since only two equal-valued capacitors are needed for programming each capacitance value, the proposed technique offers compact, cost-effective programmability when compared to traditional programming techniques employing binary-weighted capacitor-arrays (C-arrays). A demonstration prototype chip realized in a 1.2 μm CMOS double-metal double-poly technology, and which implements an 8 b programmable SC biquad giving a wide range of lowpass, bandpass and highpass filtering functions, occupies an active area of only 0.38 mm²     

Switched-capacitor filters

A novel technique for building active filters using switched-capacitor (SC) circuits is proposed. Principles of operation, methods of control, analysis, and design of a typical SC filter are presented. To assess its effectiveness, the technique is used to control input current harmonics in a phase-controlled converter. It is shown that a wide range of harmonics can be controlled using a single filter     

Synthetic aperture radar interferometry using one bit coded raw andreference signals

This paper is concerned about the generation of interferometric phase patterns using synthetic aperture radar (SAR) images obtained by processing the raw data and reference function both quantized at one bit (Signum Coded). Such processing technique involves one-bit coded (i.e., binary) sequences, and can be efficiently implemented in real time using very simple and low cost hardware. It is shown that the proposed SC processing technique preserves, besides the image intensities, also interferometric phase patterns, before and after phase unwrapping. To test the performance of the proposed technique, experiments have been carried out on real data relative to the ERS-1 mission. Quantitative comparison between the results of conventional and SC processing clearly show that the presented method can be used for quick-look DEMs generation. Moreover, in accordance with the SC-SAR theory, an upsampling has also been performed on the signals to be processed to obtain higher quality patterns. This produce a noticeable improvement of the obtained results, so that the SC techniques can be considered a valid alternative to the conventional ones, still preserving the advantages in terms of real time     

基于频谱相关技术的FBG波长偏移检测

针对峰值检测法的不足,提出了频谱相关技术和数字滤波技术,以提高光纤Bragg光栅(FBG)传感系统波长偏移检测精度.分别对峰值检测(CPD)法、数字滤波(CHEBY and IDEAL)法和频谱相关(SC)法检测波长偏移进行了数值模拟,并且搭建了实验系统,对实验数据进行具体分析计算,证实了理论分析的正确性.理论和实验证明, SC法可提高解调检测的精确度,达到理想低通滤波(IDEAL)法的效果.     

Ergodic capacity of switch-and-examine combining under flat Rayleigh fading channels

Switch-and-examine combining (SEC) is an interesting diversity technique that is simpler than selection combining (SC), whereas its performances is similar in terms of bit error rate (BER) and diversity order. As ergodic capacity is also a key performance index in modern wireless systems, this article analyzes the ergodic capacity of the SEC system. The numerical results show that the ergodic capacity of SEC with optimal threshold is similar to that of SC for arbitrary number of diversity branches.     

Order Wire Transmission in Digital Microwave Systems

Control, supervisory, and order wire signal transmission, i.e., service channel (SC) is a requirement for most microwave systems. In digital radio the data spectrum extends to the lowest baseband (BB) frequencies. Frequency translation of the SC above the data spectrum is one possibility. Another method, in frequent use, is the double modulation technique, e.g., the SC amplitude modulates the carrier that is already phase modulated by the data spectrum. A novel approach that results in significant equipment cost savings and good performance is proposed. The low-frequency power density spectrum of the random multilevel channel coded data is removed. The vacated spectrum is available for the SC. For different bit rates, the error probabilityP(e)degradation due to SC is calculated. The analysis is performed for various channel coded messages and SC spectrum utilizations. The high-pass filter that assures low-frequency data spectrum removal is optimized for the SC signal to noise ratio and dataP(e)degradation. The analysis is verified with computer simulations and actual multilevel frequency-shift keying (FSK) 6-GHz microwave hop measurements. The proposed approach is also applicable to analog microwave systems when carrying hybrid information. The hybrid system carries an SC, 6.3-Mb/s data, and 900 frequency division multiplexed voice channels in a shared BB.