Analysis and development of a signal injection technique usingtransmission lines embedded at phased array aperture

In a performance monitoring/fault isolation and correction (PM/FIC) system of a phased array antenna, a built-in transmission line embedded in the array aperture is used for signal injection to check the signal flow. The authors present an analysis of electromagnetic coupling between a twin-lead transmission line and a dipole element. An analysis of the coupling between a transmission line and a linear array of dipole elements over a ground plane has also been developed. The calculated data compared with the measured data favorably. A development of microstrip-line signal injectors embedded in an aperture of a 2D array of monopole excited parallel-plate waveguides has also been made. Measurements of the feed and aperture distributions have been made and the measured distributions follow the designed feed distribution closely     

Digital wireless sensor server using an adaptive smart-antenna/retrodirective array

A wireless sensor server is developed based on a reconfigurable active smart-antenna/retrodirective array. The system can serve as both a retrodirective array transponder and a smart-antenna receiver simply by changing the frequency of the local oscillator applied to the mixers, enabling it to utilize its hardware best to suit its communication environment. When operating as a direct-conversion receiver, the receiver array successfully demodulates a quaternary phase-shift keying (QPSK) modulated signal with circuit gain of 7 dB, and E/sub b//N/sub 0/ for BER=10/sup -4/ is approximately 12 dB without any error correction. In the retrodirective array mode, the system provides 20 dB circuit gain and 20 dB radio-frequency/intermediate-frequency isolation at the center frequency as well as phase conjugation, exhibiting excellent retrodirectivity. The mixers perform phase conjugation and modulation simultaneously, enabling the transmission of locally stored data. The local data is successfully extracted by an interrogator.     

有源相控阵雷达T/ R 组件幅相外场检测系统

针对外场环境下对有源相控阵雷达T/ R 组件幅相性能的检测要求,在充分利用雷达自身资源的基础上,设计了一种基于中场测量技术的T/ R 组件测试方案,并构建了相应的测试系统。运用归一化和阵面单元加权的相对幅相测量法对采集数据进行分析,解决了缺少标准数据的难题,提高了外场测试的灵活性和适应性。理论分析和实际测试结果表明:该系统具有操作简便、定位故障组件快速、对场地要求不高等特点,实现了一种低成本的伴随式测试保障手段。     

FPGA-based test bed for measurement of AM/AM and AM/PM distortion and modeling memory effects in RF PAs

Using a field-programmable gate array (FPGA) development board, a digital signal processor (DSP) builder, and the phase-to-amplitude conversion principle, a low-cost system for measuring the amplitude-to-amplitude (AM/AM) and amplitude-to-phase (AM/PM) distortion curves of radio frequency (RF) power amplifiers (PAs) is presented. The state of the art based on the measurements and preliminary studies of AM/AM and AM/PM distortion curves is discussed. A full digital control of the test bed simulated/emulated in Matlab/Simulink is introduced to recalculate the known AM/AM and AM/PM measurements stored as look-up table (LUT). Finally, the low-cost system comprises the memory polynomial model (MPM) that involves the nonlinearity order and memory effects of real PAs.     

阵列式无线压力传感器系统设计与迟滞补偿研究

为提高传统硅压阻式压力传感器的测量精度,针对性地设计与实现了一种带有迟滞误差校正功能的阵列式无线压力传感器系统。该系统采用了硅压阻式传感器阵列和高精度模数转换器AD7794,以STM32微处理器作为数据采集和信号处理的核心部件,并通过无线蓝牙传输模块将测量数据发送至手机接收端,以手机APP显示测量结果有利于用户对压力实现无线监测。针对硅压阻压力传感器的迟滞非线性,基于最小二乘法与函数校正法对压力传感器阵列的输出信号进行了非线性和迟滞误差补偿,结果表明：迟滞误差从原来的±0.152%降为±0.077%,,有效地提高了系统的测量精度。     

Doppler-shift correction by the DFT,for a QPSK satellite modem

This paper describes a novel technique for the measurement and correction of the Doppler shift (frequency offset) in a received QPSK signal that has been transmitted over a satellite link. The satellite is here assumed to be in a non-geostationary orbit, and correction of the Doppler shift is required to be achieved as soon as the satellite rises above the horizon, when the Doppler shift may be very high and the signal/noise ratio very low. The receiver now has no prior knowledge of the transmitted data, so that a non-data-aided system must be used, capable of operating under seriously adverse conditions. The selected technique measures the DFTs of successive blocks of samples of the received and demodulated signal, and from the DFTs it derives a control signal for the VCO, which generates the in-phase and quadrature reference carriers for the coherent demodulator. The frequency of the latter is adjusted to reduce the residual Doppler shift in the demodulated signal to a sufficiently small value, so that correct phase synchronization of the VCO on to the received signal carrier can then be achieved by means of an appropriate conventional system (not considered here). The paper describes the new technique of Doppler shift correction, and presents the results of computer-simulation tests to measure the time taken to correct an initial Doppler shift of 5 kHz in the received QPSK signal, at very low signal/noise ratios.     

A Smart Sensing Unit for Vibration Measurement and Monitoring

A novel smart sensing unit is developed in this paper for vibration measurement and machinery condition monitoring. The microprocessor-based smart sensor can collect 2-D vibrations and conduct signal analysis. When mounted in proximity of a bearing housing (a general case), it can conduct online fault detection in shafts and bearings. A correlation spectrum method is proposed as a digital encoder to recognize shaft rotation speed. A wavelet energy spectrum technique is adopted for bearing fault detection. A novel strategy is suggested to extract representative features and enhance feature characteristics by integrating the resulting wavelet energy functions over different frequency bands. The effectiveness of the developed smart sensor and the related fault detection techniques is verified by experimental tests corresponding to different bearing conditions. Test results show that the developed smart sensing unit is an effective measurement and condition monitoring tool; the wavelet energy spectrum technique is a robust bearing fault detection method, especially for nonstationary feature extraction and analysis.      

60 GHz Single-Chip Front-End MMICs and Systems for Multi-Gb/s Wireless Communication

Single-chip 60 GHz transmitter (TX) and receiver (RX) MMICs have been designed and characterized in a 0.15mum (f_T~ 120 GHz/f _MAX> 200 GHz) GaAs mHEMT MMIC process. This paper describes the second generation of single-chip TX and RX MMICs together with work on packaging (e.g., flip-chip) and system measurements. Compared to the first generation of the designs in a commercial pHEMT technology, the MMICs presented in this paper show the same high level of integration but occupy smaller chip area and have higher gain and output power at only half the DC power consumption. The system operates with a LO signal in the range of 7-8 GHz. This LO signal is multiplied in an integrated multiply-by-eight (X8) LO multiplier chain, resulting in an IF center frequency of 2.5 GHz. Packaging and interconnects are discussed and as an alternative to wire bonding, flip-chip assembly tests are presented and discussed. System measurements are also described where bit error rate (BER) and eye diagrams are measured when the presented TX and RX MMICs transmits and receives a modulated signal. A data rate of 1.5 Gb/s with simple ASK modulation was achieved, restricted by the measurement setup rather than the TX and RX MMICs. These tests indicate that the presented MMICs are especially well suited for transmission and reception of wireless signals at data rates of several Gb/s     

基于探测器阵列的激光远场光斑测量系统

设计开发了一套基于探测器阵列的激光远场光斑测量系统.在1.5 m×1.5 m的靶面尺寸上间隔10 cm排列了15行×15列激光探测器阵列,探测器响应信号经前置放大后分别进行同步脉冲产生和信号峰值保持、峰值信号A/D采样,最后经计算机通信存储,事后进行光斑图像的形成和分析处理.光斑能量密度测量范围10 μJ/cm~2～10 mJ/cm~2,单元探测器测量精度优于15%,最高测量激光频率可达500 Hz.可满足目前大功率激光干扰武器装备的测量需求.     

An efficient method for nonlinear distortion calculation of the AM and PM noise spectra of FMCW radar transmitters

The demand for autonomous cruise control and collision warning/avoidance systems has increased in recent years. Many systems based on frequency-modulated continuous-wave (FMCW) radar have emerged and are still in development. Due to the high complexity of such systems, the accurate evaluation of the noise spectra in the transmitter chain driven by complex modulated signals is today a severe drawback due to the limitation of simulation tools. In this paper, a method is proposed to compute easily with any commercially available nonlinear simulator, the amplitude and phase modulated signal distortion introduced by the nonlinearities of the transmitter on an FMCW signal. First, the amplitude modulation (AM) and phase modulation (PM) noise spectra of the driving FMCW signal is derived from the knowledge of the continuous wave (CW) AM and PM noise spectra of the voltage-controlled oscillator (VCO), and the modulating saw-tooth signal applied. Using the narrow band envelope concept and a first-order expansion of the nonlinear transfer function of the transmitter, the transfer of the AM and PM noise spectra of the driving FMCW signal through the nonlinear transmitter chain and the resulting output distortion are then computed. This novel approach allows to compute with reduced computation time and very good accuracy the AM/AM, AM/PM, PM/PM, and PM/AM conversion terms in any nonlinear system driven by CW or FMCW signals. This new method has been applied to the characterization of a whole car radar transmitter operating at 77 GHz driven by an FMCW signal issuing from a VCO. A successful comparison between measured and simulated PM-to-AM conversion coefficients of this transmitter is shown, validating the proposed method.     

Seat support surface optimization using force feedback

The development, implementation and evaluation of an algorithm designed to find optimal seat support surfaces are presented. The algorithm has been developed and implemented on an active contour measurement device. The device consists of an array of positioning elements equipped with force sensors for feedback. With a patient seated on the array, the algorithm is designed to find a seat contour that optimally satisfies given performance criteria. The performance criteria are based on measured stiffness of the soft tissues. A theoretical development of the algorithm is presented along with the modifications made to the algorithm during implementation. The results from several tests using man-made test bodies and a prototype contour gauge are presented to verify the algorithm's performance     

4$,times,$25 Gb/s Frequency-Modulated DBR Laser Array for 100-GbE 40-km Reach Application

A monolithically integrated 100-Gb/s throughput (4 $,times,$25 Gb/s) laser array has been developed that employs frequency-modulated distributed Bragg reflector lasers. An optical filter converts a frequency-modulated signal to an amplitude-modulated signal with a high contrast ratio in addition to reducing the lasing spectrum bandwidth. A clear eye opening after 40-km transmission was observed with a 25-Gb/s nonreturn-to-zero signal in the 1550-nm region.      

An active integrated retrodirective transponder for remoteinformation retrieval-on-demand

A retrodirective transponder based on a novel compact phase-conjugating mixer with conversion gain has been developed. The active circuit uses one port for both incoming and outgoing signals, enabling a reduction of circuit size, and the balanced structure provides suppression of undesired signals. By using a modulated local oscillator, the circuit can modulate the received signal in order to retransmit local information to the remote site. A microstrip antenna is integrated with the phase conjugator and the whole system was fabricated on a single substrate, enabling a one-card system. A four-element prototype array with 0.5λ₀ array spacing demonstrated excellent measured retrodirectivity. Additionally, a simplified binary-phase-shift-keying signal transmitted by the array is recovered successfully at the source location, demonstrating great potential for remote tagging and wireless sensor applications     

A novel, robust DSP-based indirect rotor position estimation for permanent magnet AC motors without rotor saliency

This paper proposes and implements a novel rotor position sensorless technique for PM AC motor drives, which allows acceleration from standstill and can operate under various practical operating conditions including transient speed changes. The technique developed here relies on the measurement of the phase voltages and currents of the motor. It uses the incremental values of flux linkage, and the back-EMF functions to estimate incremental rotor position. Using a phase-locked loop (PLL) algorithm, an internal closed-loop correction algorithm can correct rotor position estimation drift, which may be due to the motor parameter variations or measurement inaccuracies. The method is implemented in closed-loop using a digital signal processor (DSP), and details of the implementation are provided in the paper. To demonstrate accuracy, robustness and reliability of the position estimation scheme, the paper presents a number of real-time experimental results, including dynamic operating conditions.     

The receive voltage transmission function of a phased array antenna element

A general method has been developed for determining the voltage response of a phased array element to an incoming electric field. The incident field may arrive from any scan angle, and mutual coupling effects are accounted for in terms of the array element active reflection coefficient. The method defines a receive voltage transmission functionbar{T}(theta, phi, f)as a term whose product with the incident electric fieldE_{i}(theta, phi, f) results in the array element voltage response. The derivation ofbar{T}(theta, phi, f)is obtained by treating each phased array antenna element as a receiving aperture, having an active impedance related to the mutual coupling in the array. The element effective length is formulated using an array element receive equivalent circuit, and the transmission functionbar{T}(theta, phi, f)is obtained using this effective length formulation. The usefulness of the transmission function for studying the response of a phased array element to particular radar signal waveforms is suggested, and an experimental evaluation ofbar{T}(theta phi, f)is described using mutual coupling measurements on a 37-element crossed dipole test array.     

Effects of One Large Signal on Small Signals in a Memoryless Nonlinear Bandpass Amplifier

The theoretical relationships are presented for determining the output amplitude and phase of each small signal when commonly amplified with a large signal by a memoryless nonlinear amplifier. Both the amplitude and phase of each output small signal depend on the input amplitude of the large signal and on the AM/AM and AM/PM characteristics of the nonlinear amplifier. If the nonlinear amplifier is a hard limiter without AM/PM conversion, then the well-known result can also be derived from a general formula developed in this paper. A numerical example is given and confirmed by laboratory measurement.     

A data-gathering antenna array for transhorizon propagation research

A versatile vertical antenna array and receiving system have been developed for measuring relative phase and amplitude along the wavefront of anS-band transhorizon signal. The array, which operates at 3.200 GHz, consists of 12 parabolic antennas 1.22 meters (4 feet) in diameter which are spaced 1.39 meters apart on a tower for a total effective vertical aperture of 15.24 meters (162 lambda). The raw data outputs from the array are amplitude and differential phase successively sampled from the 12 elements. Data can be taken at variable rates of up to 100 passes per second over the 12 elements. The data are processed in a computer to form conventional uniformly illuminated array beams 0.3 degree wide with a grating lobe spacing of 3.9 degrees or to produce many combinations of correlation functions. A reference signal is used to cancel the effects of relative motion of the array support structure from the phase data. The array and receiving system and actual performance characteristics are described.     

Use of direct-modulated/gain-switched optical links inmonopulse-type active phased array systems

With the advance of high speed laser technology, optical interaction with microwave circuits has become highly viable. Such interaction is advantageous as the fiber is low-loss, lightweight, and immune to electromagnetic interference. In this paper, interaction of direct-modulated and gain-switched optical links with active antenna phased array systems is demonstrated. In the direct-modulated optical system, the RF signal directly modulates the DFB laser. In the gain-switched optical system, the laser is gain-switched to function as a RF frequency doubler. The modulated signal is transmitted via an optical fiber and recovered at the receiving end by a high-speed photodetector. The recovered RF is then injected into the active antenna phased array systems as an injection-locking reference signal. Two active antenna systems are used for this demonstration: beam-switching and Doppler transceiver     

Failure Analysis of Memory Organization for Utilization in a Self-Repair Memory System

Traditional approaches to memory reliability have been limited to complete redundancy or coding techniques. Redundancy frequently proves too expensive (introducing additional systems faults) and the traditional memory coding techniques have been limited to those areas of memory where a single fault results in a single failure (e.g., a broken core in a magnetic memory) as distinguished from an address decoder fault. To take an integrated approach to this problem, using a variety of coding and modularization techniques on each of the memory subsystems, it is necessary to determine the types of faults and failures caused by these faults that could occur in the system. This paper presents the results of a failure analysis study of typical 2D, 2?D, and 3D memory organizations. Two-way memories are also considered. This study demonstrates that a 2D memory, utilizing a switching array for memory access, is less susceptible to eatastrophic failures than other organizations considered. A memory organization capable of distributing the failures, in a manner permitting correction by linear codes, was adopted. Other techniques for automatic replacement of fault units are also considered.