Harmonic Signals Retrieval Approach Based on Blind Source Separation

A frequently encountered problem in signal processing is harmonic retrieval in additive colored Gaussian or non-Gaussian noise, especially when the frequencies of the harmonic signals are very close in space. The purpose of this paper is to develop an efficient Blind Source Separation (BSS) algorithm from linear mixtures of source signals, which enables to separate harmonic source signals using only one observed channel signal even if the frequencies of the harmonic signals are closely spaced. First, we establish the BSS based harmonic retrieval model in additive noise by using the only one observed channel, and analyze the fundamental principle by utilizing BSS method to retrieve harmonics. Then, we propose a BSS-based approach to the harmonic retrieval by resorting the concept of W-disjoint orthogonality in the over-complete BSS situation, and as a result, we get the separation algorithm using only one channel mixed signals. Simulation results show that the proposed separation algorithm-BSS-HR is able to separate the harmonic source signals.     

Accurate RF large-signal model of LDMOSFETs including self-heatingeffect

In this paper, we present a new silicon RF LDMOSFET large-signal model including a self-heating effect. A new empirical channel current model suited for accurately predicting intermodulation distortion is employed. The proposed channel current model can represent transconductance (gm) saturation and rolloff in the continuous manner. It has continuous higher order derivatives for accurate prediction of nonlinear microwave circuit behavior, such as power amplifiers, microwave mixers, oscillators, etc. Using the complete large-signal model, we have designed and implemented a 1.2 GHz power amplifier. The measured and simulated amplifier characteristics, especially the intermodulation and harmonic behaviors, are in good agreement     

Tunable wideband SAW-less receiver front-end in 65 nm CMOS

A surface acoustic wave-less receiver front-end for GSM, TD-LTE and TD-SCDMA standards featuring a novel low noise amplifier (LNA) architecture and harmonic rejection technique is presented. The two-stage LNA uses capacitive feedback in the first stage for wideband input matching. It can operate from 500 MHz up to 2.5 GHz with an S₁₁ below ?15 dB. The harmonic rejection mixer structure operates using two- and four-phase local oscillator signals and is capable of achieving a high harmonic rejection over a wide channel bandwidth. The average harmonic rejection is above 60 dB measured over a 20 MHz LTE channel and above 70 dB over a GSM channel. The mixer structure contains digitally tunable resistor and capacitor banks for precise tuning, causing the peak harmonic rejection in the channel to exceed 80 dB. The precise tuning capability ensures good harmonic rejection in the presence of process mismatch and duty cycle mismatch. The 1-dB received signal compression point with a blocker present at 20/80 MHz offset for low-/high-band is 0 and +2 dBm, respectively. In-band IIP3, and IIP2 are ?14.8 and >49 dBm, respectively, for low-band. For high-band they are ?18.2 and >44 dBm. Implemented in 65 nm CMOS, the complete front-end consumes 80 mW of power.     

基于向量序列谐波恢复的缓时变频率选择性MIMO无线信道的估计方法

该文研究缓时变频率选择性MIMO无线信道谐波拟合模型参数的估计问题,提出基于向量序列谐波恢复及非线性约束最小二乘法的非盲信道估计方法。与以往采用chirp序列作为训练信号的方法不同,该文采用全序列作为训练信号。仿真结果表明,与采用chirp序列作为训练信号的方法相比,此方法的训练信号容易获得,并且在相同信噪比条件下具有更好的估计精度。     

A Carrier-Transit-Delay-Based Nonquasi-Static MOSFET Model for Circuit Simulation and Its Application to Harmonic Distortion Analysis

In this paper, a compact model of nonquasi-static (NQS) carrier-transport effects in MOSFETs is reported, which takes into account the carrier-response delay to form the channel. The NQS model, as implemented in the surface-potential-based MOSFET Hiroshima University STARC IGFET model, is verified to predict the correct transient terminal currents and to achieve a stable circuit simulation. Simulation results show that the NQS model can even reduce the circuit simulation time in some cases due to the elimination of unphysical overshoot peaks normally calculated by a QS-model. An average additional computational cost of only 3% is demonstrated for common test circuits. Furthermore, harmonic distortion characteristics are investigated using the developed NQS model. While the distortion characteristics at low drain bias and low switching frequency are determined mainly by carrier mobility, distortion characteristics at high frequency are found to be strongly influenced by channel charging/discharging.     

Harmonic vibration suppression of maglev rotor system under variable rotational speed without speed measurement

The high-speed rotating machinery equipped with active magnetic bearings (AMBs) always suffers from rotor unbalance and displacement sensor runout, which produce periodic fluctuations in current and cause power amplifier saturation and severe harmonic vibration. The harmonic vibration suppression, especially under variable rotational speed, requires the speed information, but the problem of no installation conditions for speed measurement sensors in some applications may rise with conventional suppression approaches. This paper presents a novel multi-notch filters (MNFs) method with frequency estimator to suppress the harmonic vibration. Firstly, the harmonic vibration dynamic modeling is described and the expressions of current and vibration force affected by harmonic displacement disturbance are obtained. The structure and notch characteristic of the MNFs are then presented, the frequency estimator based on one single channel displacement signal is developed and its convergence is analyzed. Moreover, the stability of the whole system with MNFs is investigated and the compensation phases are implemented according to system identification to maintain the closed-loop stability. Simulation and experiments are conducted on an AMB-rotor setup and validate the effectiveness of the proposed method on eliminating the harmonic current and suppressing the harmonic vibration under the variable rotational speed.     

Characterization of annealed proton exchanged LiNbO3waveguides for nonlinear frequency conversion

A thorough and detailed characterization of annealed proton-exchanged (APE) waveguides in Z-cut LiNbO₃ is described. The mode index measurements in planar waveguides as a function of wavelength and annealing time are reported, including useful analytical relations for the refractive index change, its dispersion, and the depth profile as a function of annealing parameters. Analytical expressions for the mode propagation characteristics are presented and experimentally verified with reasonable accuracy. It is shown that the planar waveguide characterization results can be used to model the channel waveguide characteristics accurately. The model provides closed-form expressions for the mode index and the mode field profile, and the theoretical results are in excellent agreement with the measured data. The technique is used to accurately predict the phase mismatch between the fundamental and second harmonic modes in frequency-doubling experiments using APE channel waveguides. An optimum waveguide geometry for which the phase mismatch is relatively insensitive to the waveguide nonuniformity was predicted and verified experimentally     

Analysis and modeling of nonlinearities in VLSI MOSFETs includingsubstrate effects

Presents a detailed analysis of the distortion components of the drain current of integrated MOS transistors operated in nonsaturation, in which signals are simultaneously applied to the drain, gate, and substrate terminals. In contrast with previous analyses which have accounted for the modulation of the inversion layer channel mobility by both transverse and longitudinal fields (short channel devices), the model yields highly accurate analytical expressions in closed form (down to at least 80 dB below fundamental), and hence easily lends itself to 'hand' analysis. Moreover, the model predicts that individual odd or even distortion components can be suppressed (nulled) by a range of combinations of substrate bias and signal amplitudes. Alternatively, odd distortion components can be nulled by suitable substrate drive while even distortion components can be nulled by properly driving the gate terminals of the MOSFETs. Experimental data which validate the model are presented, and the effectiveness of harmonic suppression in a standard, tunable, MOSFET-C integrator is demonstrated     

Effects of threshold based relay selection algorithms on the performance of an IEEE 802.16j mobile multi-hop relay (MMR) WiMAX network

IEEE 802.16j MMR WiMAX network introduces multi-hop relay architecture, which involves cooperative relay stations focusing on increasing the network throughput and coverage. Relay selection algorithms can be used to choose the optimal relay, which help in reducing the computational complexity during the signal processing operation of the wireless network. In this research work, a conventional Amplify-Forward (AF)/Decode-Forward (DF) assisted multi-relay IEEE 802.16j WiMAX network is considered. The effects of relay selection algorithms on the performance metrics such as Symbol Error Rate (SER) and channel capacity are investigated in detail through simulation-based study. Further, the performance of this network utilizing the proposed relay selection algorithms, namely threshold based max_min and threshold based harmonic mean of SNR, are compared with the existing max_min and harmonic mean of SNR based algorithms. Standard diversity combining techniques such as Maximal Ratio Combining (MRC) and Selection Combining (SC) are used for combining the transmitted signal at the receiver. In addition, the impact of relay locations on the performance metrics are explored. It is observed that both the proposed threshold based max_min and threshold based harmonic mean of SNR based relay selection algorithms outperform the max_min and harmonic mean of SNR based algorithms, as both the SER and channel capacity for the considered multi-relay WiMAX network is improved significantly. Further, this extensive study and analysis will be beneficial for the design of MMR WiMAX networks.     

Numerical modeling of second harmonic generation in opticalwaveguides using the finite element method

A numerical study of second harmonic generation (SHG) in optical waveguides is presented using the finite element method (FEM) and the Crank-Nicholson split-step procedure. Results are given for a Cherenkov radiation scheme in both planar and channel waveguides. Also presented are results obtained on frequency doubling for guided modes in both planar and channel waveguides, using the quasi-phase-matching scheme     

Optimization of MOS amplifier performance through channel length and inversion level selection

The dependence of MOS amplifier performance on channel length and channel inversion is simulated and discussed. Suggestions are made regarding the optimization of voltage gain, nonlinear distortion and the gain-bandwidth product (GBW) through careful device length and inversion level selection. The midband voltage gain of the common-source amplifier is shown to remain relatively constant when biased for weak inversion operation, with short-channel devices continuing to amplify effectively at very low levels of inversion, allowing for extremely low power circuits. Total harmonic distortion is reduced through decreasing channel length and/or the level of channel inversion. The GBW is optimized through the use of minimum sized transistors biased to operate in the strong inversion region.     

An improved deep submicrometer MOSFET RF nonlinear model with newbreakdown current model and drain-to-substrate nonlinear coupling

An improved deep submicrometer (0.25 μm) MOSFET radio-frequency (RF) large signal model that incorporates a new breakdown current model and drain-to-substrate nonlinear coupling was developed and investigated using various experiments. An accurate breakdown model is required for deep submicrometer MOSFETs due to their relatively low breakdown voltage. For the first time, this RF nonlinear model incorporates the breakdown voltage turnover trend into a continuously differentiable channel current model and a new nonlinear coupling circuit between the drain and the lossy substrate. The robustness of the model is verified with measured pulsed I-V, S-parameters, power characteristics, harmonic distortion, and intermodulation distortion levels at different input and output termination conditions, operating biases, and frequencies     

Multi-order predistortion of power amplifiers using a second harmonic based technique

A novel multi-order predistortion linearizer is proposed to achieve independent control of the third- and fifth-order intermodulation products in high power amplifier. The approach is based on a combination of the second harmonic technique and the difference frequency technique. The second harmonic and difference frequency terms are generated using an envelope detector and two frequency multipliers. The RF predistorter has the advantage of low insertion loss and the requirement of a short delay line. Experimental results demonstrate an adjacent channel power ratio (ACPR) reduction of 11 dB for W-CDMA, at 2140 MHz.     

TACAN机载接收机谐波抑制对测距精度的影响研究

TACAN机载设备通过无线信道与地面台通信,机载设备信号的接收是通过超外差射频通道进行的,通道性能的好坏直接影响TACAN测距精度,所以射频通道的设计至关重要。本文正是基于这一点,通过理论分析的方法研究了TACAN机载设备射频通道指标中谐波干扰信号的特性对TACAN测距精度的影响,为TACAN射频通道的设计做出参考。     

Jointing Adaptive Modulation Relay Selection Protocols for Two-Way Opportunistic Relaying Systems with Amplify-and-Forward Policy

Two novel best-relay selection protocols, the jointing adaptive modulation max–min (AM-MM) protocol and the jointing adaptive modulation maximum harmonic mean (AM-MHM) protocol, are proposed for two-way opportunistic relaying systems with amplify-and-forward policy (TWOR-AF). By integrating the adaptive modulation with the conventional max–min (NonAM-MM) and maximum harmonic mean protocols, the effect of the modulation schemes used at both sources is exploited perfectly in the proposed AM-MM and AM-MHM protocols. The analytical expressions to the approximate upper bounds of overall average symbol error probability (SEP) for TWOR-AF systems with these different relay selection protocols are obtained through theoretic analysis. The numerical results demonstrate that the average SEP of TWOR-AF systems can be improved greatly when the proposed jointing adaptive modulation relay selection protocols are performed. Furthermore, in certain channel realizations, the adaptive modulation non-selection protocol outperforms the conventional NonAM-MM protocol in which the adaptive modulation is not integrated.     

Distortion in broad-band gallium arsenide MESFET control and switchcircuits

The author analyzes the nonlinear mechanisms of the MESFET in its passive control mode of operation and equations are developed that allow designers to predict second- and third-order harmonic and intermodulation products in the conducting state MESFET. The analytic expressions are verified by experimental data. The discussion is based on a lumped element equivalent circuit model and is limited to applications where the MESFET is operating in its conducting state. In switch circuits, the analysis indicates that distortion may be reduced by the use of MESFETs with pinchoff voltages in the 2-3-V range and with large open channel current capacities. In attenuators, the analysis shows extreme variations in the level of distortion over a relatively narrow range of attenuation levels. Distortion in the case of the reflective attenuator may be reduced by the use of MESFETs with small open channel current capabilities     

适用于“村村通”的米波段10W8频道电视发射系统的研制

实现“村村通”,其实现方式的经济性与实用性至关重要。设计出米波段谐波相关频道的具体频率参数,用捷变频调制器“调出了”谐波相关频道,在研制工作中发挥了重要作用。     

High-Frequency Si-MOSFET's

Silicon (Si-) MOSFET's with 0.8-mu m channel, made by conventional technology and optimized for microwave applications, have noise figures of 3.7 dB at 4 GHz and maximum frequencies of oscillation of 10 to 12 GHz. The noise and radio-frequency (RF) small signal performance are only slightly affected by double ion implantation of the channel region, used to shift the threshold voltage from - 2 V to +0.2 V. Excess noise is generated in the implanted MOSFET's for lower V/sub DS/ values than in unimplanted ones. The variation of the noise parameters with drain current is lower in implanted devices. The RF equivalent circuit analysis indicates negligible parasitic lead resistances, but high feedback capacitance. A comparison with GaAs MESFET's of the buried channel type showed the Si-MOSFET's to have lower third-order harmonic distortion when driven by a 1-GHz signal source.     

Computer model and charge transport studies in short gate charge-coupled devices

A computer model has been developed that simulates charge transport of carriers in a surface channel charge-coupled device. This model is based on the charge continuity and current transport equations with a time dependent surface field. The device structure of the model includes a source diffusion an input gate and transfer gate. The present model is the first real simulation of the input scheme of the surface-channel CCDs. The scooping and spilling techniques associated with the charge injection process are simulated by the input diffusion which is included in the model.As an application to a CCD practical problem the present model has been used to study the linearity of the electrical charge injection into surface channel charge-coupled devices. The generated harmonic components of a sinusoidal input are calculated using the transfer characteristics of the input stage obtained from the computer simulation.Using this model the spatial variations of the self-induced fringing field and total currents under the storage and transfer gates were computed. The charge transfer mechanisms for short-gate (L ≤ 8 μm) CCDs was investigated. It was found that for short gates the charge transfer efficiency is governed mainly by the fringing field and self-induced current mechanisms. The results of this study help to clarify the mechanism by which the signal-charge level and gate length affect the charge transfer efficiency.     

A modified beam propagation method to model second harmonicgeneration in optical fibers

A finite-difference implementation of the beam propagation method (BPM) is used to solve the paraxial, scalar wave equation with a nonlinear source term. A transparent boundary condition capable of handling asymmetric modes is incorporated in the finite-difference algorithm. This nonlinear BPM is used to model the generation and propagation of second harmonic light in an optical fiber which has been prepared for second harmonic generation (SHG) by the formation of a _χ⁽²⁾ grating. This method can be used to predict the guided mode in which the generated second harmonic light propagates based on the modes of the writing (fundamental and second harmonic) and reading (fundamental only) light. The effects of self-phase modulation (SPM) and cross-phase modulation (XPM) are included in the model