Fourier transformation using an electroabsorptive CCD spatial light modulator

The use of a GaAs CCD as a spatial light modulator is described and its application to coherent optical Fourier transformation is analyzed. In this device, the transmission through the two-dimensional buried-channel CCD may be electroabsorption modulated near the GaAs cutoff wavelength since the electric field in each storage well is controlled by the transferred charge. One of the primary advantages of this modulator is the ability to electrically address the device at high speed. Analysis of the two-dimensional modulator with a silicon CCD detector array yields a projected dynamic range approximately equal to the number of modulator array elements. For arrays containing greater than 1000 elements, detector performance and nonuniformities can limit the maximum range to 30-40 dB. The device can also be optically addressed, and in this mode of operation it has a comparable dynamic range to the electrically addressed structure with an optical write energy an order of magnitude lower than liquid crystal or photorefractive light valves. An alternative mode of device operation is a waveguide mode in which the light propagates along an epitaxial layer and is modulated as it passes under a one-dimensional CCD. The detection is done by a second linear CCD. The higher modulation efficiency results in a dynamic range approximately one hundred times the number of elements but is again limited to 30-40 dB because of detector response and nonuniformities.     

An Integrated IF Amplifier and Detector for an A.M. Upconversion Radio

This paper presents a monolithically integrated IF amplifier and envelope detector for an AM upconversion car-radio receiver. This receiver is intended for the reception of the long-wave and medium-wave frequency bands and uses an intermediate frequency of 10.7 MHz. Specific requirements resulting from the upconversion concept will be illustrated and the basic considerations for maximization of the signal-to-noise ratio as a function of the input signal level will be given. Furthermore, a new method will be presented for fixing the signal levels and the AGC speed in the amplifier. The amplifier uses two emitter-driven variable-gain pairs alternated by negative-feedback current amplifiers. It has an AGC range of 90 dB and a gain of 66 dB. The audio output level is constant within 0.2 dB over the full controll range. A cross-quad compensated envelope detector is driven at a level as low as 30 mV and shows less than 3-percent distortion at a modulation depth of 80 percent.     

Improvement of responsivity of high-speed infrared detector using hot carriers in semiconductors

A room temperature, high-speed and high-sensitive infrared hot carrier detector using p-type Ge has been investigated at 10.6 μm. The detector is composed of a whisker antenna and a diode contact forming an ohmic contact on p-type Ge. This detector has the merit that one can easily have impedance matching between the antenna and the diode contact without any matching section, so that high sensitivity can be obtained. A voltage sensitivity 16 dB higher than that of metal-insulator-metal (MIM) point contact diode has been observed from this detector.     

基于相干激光雷达的激光微多普勒探测

利用相干激光雷达探测目标微动特性技术是一种以单频激光为光源,用外差探测的方式实现对低速、低频多个运动物体进行微多普勒信息提取和识别的技术.以波长为1.064 μm的窄线宽单块激光器为光源,发射激光经过模拟长距离传输的4 km的光纤延迟,照射到以扬声器的发声单元和电动平移台为目标的微动物体上,目标反射的激光会聚进入单模光纤,参考光与信号光通过3 dB光纤合束器线性耦合进入同一根光纤,并在探测器表面进行相干.用于接收相干信号的探测器的接入方式为光纤输入,带宽为3.5 GHz.利用时间-频率域联合描述的方法对数/模(A/D)采样后的数据进行分析.在4 km光纤延迟时,本系统最低探测速度为0.5 mm/s,速度分辨率达到毫米每秒量级,频率分辨率达到千赫兹量级.利用微多普勒信息探测技术,实现了探测物体表面的微动状态信息和识别运动状态的目的.     

基于FPGA的相控阵探测器高速信号处理电路

为了降低相控阵探测器结构的复杂度,基于现场可编程门阵列FPGA设计了五通道高速信号处理电路。采用坐标旋转数字计算机CORDIC和多相分解滤波器设计了数字下变频器,降低每个数据流的处理负担。在波达方向DOA模块中,引入改良的收缩阵列方法,实现了对数据的并行处理,缩短了空间谱的搜索时间。利用嵌入式乘法器和加法器实现了波束形成网络BFN的可编程设计,使响应速度达到了毫秒级。实验结果表明:设计的电路总延迟仅为1.242 ms,能将原始信号放大到近13 dB,方向角测量误差小于1°,实现了对无线电基带信号的高速处理。     

Technique for minimising effect of detector inhomogeneity on fibre attenuation measurements

In fibre attenuation measurements by the `cut-back? method, the necessity for a homogeneous detector is implicit. We have found a commonly used germanium detector to be significantly inhomogeneous, leading to an estimated attenuation discrepancy of 0.02 dB at best and 0.4 dB at worst. In the letter, we outline a method for reducing this discrepancy to levels of less than 0.004 dB.     

一种长波红外光导探测器CMOS电路设计

CMOS 电路是高输入阻抗,而长波红外光导探测器是低阻抗,实现低阻抗红外光导探测器与CMOS 电路的良好匹配,是目前长波红外探测器高性能成像的关键技术。文中设计了一种能在低温下工作的低阻抗红外光导探测器CMOS 电路,差分放大器采用正负电源供电,在输入级采用桥式输入方式,该电路第一级采用1M的负反馈电阻实现信号放大,第二级放大采用正端放大方式,输入级、第一级放大、第二级放大均采用直接耦合方式。测试结果表明,该放大器与长波红外低输入阻抗光导探测器连接后能正常工作,总放大倍数大于1 万倍,3 dB 带宽大于4 kHz,等效输入电压噪声小于1.5 V,有效地解决了低阻抗光导探测器与高阻CMOS 电路的匹配问题。     

非致冷InAsSb中长波红外探测器研究评述

作为一种新兴的红外光电材料,InAsSb由于其禁带宽度窄、电子迁移率极高等优良特性受到了世界各国的广泛关注。InAsSb探测器的优势在于：对中长波红外波段的探测而言,其在室温下也具有很高的探测率,同时InAsSb探测器具有比HgCdTe探测器更高的响应速度。这些优势使得InAsSb探测器可制成非致冷型红外探测器,容易实现仪器的小型化,大大降低成本,在某些场合成为能够取代HgCdTe的理想材料。文章分别对InAsSb探测器国内和国外的研究近况作一简要评述,从而显示出在中长波红外波段InAsSb材料广阔的应用前景。     

Bipolar Microwave RMS Power Detectors

A peak/RMS power detector with$geq hbox 40~dB$dynamic range is presented. The simulated frequency response is flat to 60GHz and the measured response is flat to 20 GHz. Analysis shows that the Meyer detector, originally developed as a peak detector, can be used for RMS detection with an error less than 0.5dB over an approximately 20 dB range, comparable to the popular RF/microwave diode detector. The range for RMS detection is extended by cascading several stages of attenuators and detectors, leading to a circuit suitable for applications such as embedded RFIC test. The power detector is only 700$,times,$550$muhbox m ^2$including all AC and DC bond pads.     

碲镉汞高温红外探测器组件进展

高工作温度红外探测器组件是第三代红外探测器技术的重要发展方向,可用于高工作温度红外探测器的基础材料主要有锑基和碲镉汞两大类。介绍了昆明物理研究所在高工作温度红外焦平面探测器组件方面的最新研究进展,其中基于碲镉汞材料p-on-n技术研制的高工作温度中波640×512探测器组件在150 K温区性能优异,探测器的噪声等效温差(NETD)小于20 mK,配置了高效动磁式线性制冷机的高温探测器组件(IDDCA结构),质量小于270 g,探测器组件光轴方向长度小于70 mm(F4),室温环境下组件稳态功耗小于2.5 Wdc,降温时间小于80 s,声学噪声小于27 dB,探测器光轴方向自身振动力最大约1.1 N。目前正在进行环境适应性和可靠性验证,完成后就可实现商用量产。     

High performance single mode OTDR using coherent detection and fibre amplifiers

A high performance single mode OTDR has been constructed at 1.55 mu m using a DFB laser diode, laser diode pumped fibre amplifiers and a coherent detector, all suited to integration into a robust and portable instrument. A dynamic range of 33 dB has been attained with 1 mu s launch pulses, 1 MHz receiver bandwidth and 10/sup 4/ integrations. This result represents an increase of about 13 dB in performance over the standard version of the OTDR using a laser diode as a light source. It is comparable to the best previously reported value attained using a high power glass laser and a cooled detector.<>     

A 7.5-GHz super regenerative detector

In this paper, simulated and measured results are presented for a microwave-integrated-circuit super regenerative detector operating at 7.5 GHz and brief comparisons made to a monolithic-microwave integrated-circuit super regenerative detector operating at 34 GHz. The sensitivity of the 7.5-GHz detector was measured at -83-dBm (AM, 1 kHz, 100 % mod) RF signal for 12 dB (signal + noise + distortion)/(noise + distortion). Simulation results show that, to produce a sensitive super regenerative detector, a high rate of change in loop gain of the oscillator circuit with respect to the gate bias (quenching) voltage and a high maximum loop gain at the point of detection is required. It has also been shown, by simulation and measurement, that the detection frequency of the super regenerative detector is lower than the normal free-running oscillation frequency     

Accurate determination of waveguide-fed p-i-n photodiode absorption

Experimental and theoretical determinations of the absorption of a waveguide fed GaInAs photodiode are presented. The absorption is determined as a function of the propagation length using μ-p-i-n diodes regularly spaced along the GaInAs absorbing layer. The detector absorption is as high as 2060 dB/cm. However, for propagation lengths longer than ~200 μm it falls to about 120 dB/cm. The results are analyzed using two different approaches. The first consists in determining the eigenmodes of both the passive waveguide and the detector/waveguide structure. The second is the beam propagation method (BPM). Both methods demonstrate that the absorption curve can be fully explained by the existence of two modes, of which the one with the lowest absorption is induced by the presence of an undoped InP buffer layer. Both eigenmode decomposition and BPM are in quantitative agreement with the experimental data     

空间光耦合平衡探测器设计与测试

星地空间相干光通信中,受大气湍流及空间光耦合效率因素的影响,要实现高速率、高探测灵敏度的通信变得异常困难。针对星地空间相干光通信链路中空间光耦合较难的问题,提出了采用大面积平衡探测器来提高探测灵敏度的方法。通过分析平衡探测技术的原理及平衡探测器结构,设计了一种探测面直径为100 m、工作速率为5 Gbps的平衡探测器,搭建了空间相干光通信测试平台。在5 Gbps通信速率下,探测器的直接探测灵敏度达到-18.6 dBm,相干探测灵敏度达到-43.89 dBm,共模抑制比高于38.5 dB。测试结果验证了该空间光耦合平衡探测器用于空间相干光通信的可行性。     

基于FPGA的直接数字波形合成宽带信号源的设计与实现

提出一种改进的波形存储直读法产生宽带雷达线性调频信号的设计方案.以单片高速FPGA取代以往设计中使用的DSP FPGA作为系统的控制核心,简化系统结构.外围接口通用化、模块化,可产生带宽200MHz以内、时宽800μs以内的任意LFM信号.应用预失真技术,产生的宽带信号线性调频相位失真小于±1度,线性调频脉冲顶部不平坦度小于0.5dB,采用Hamming加权后脉冲压缩峰值旁瓣比大于38dB.     

A low noise readout detector circuit for nanoampere sensorapplications

A readout detector IC has been developed which is capable of detecting nanoampere photo-current signals of interest in a high (microampere) background illumination or dc noise level (SNR=80 dB). The readout detector sensor IC processes transient signals of interest from a separate photo-diode pixel array chip. Low noise signal conditioning, filtering, and signal thresholding implement smart sensor detection of only “active pixels.” This detector circuit can also be used to perform signal conditioning for other sensor applications that require detection of very small signals in a high background noise environment     

An eigen-assisted noncoherent receiver for Alamouti-type space-time modulation

We consider noncoherent block detection of Alamouti-type space-time (ST) modulations, employing PSK constellations in quasi-static Rayleigh-fading channels with L receive antennas. The proposed detector, termed an eigen-assisted (EA) receiver, constructs a sample-correlation matrix from the L length-N received signals, determines its two principal eigenvectors, and uses these eigenvectors to reconstruct the two transmitted length-N patterns. Scalar differential encoding is performed at the transmit antennas, and as a result, the transmitted data can be recovered from the reconstructed patterns using scalar multiple-symbol differential detection. In other words, ST-differential encoding is not required at the transmitter and the constellation expansion typically observed with nonbinary signaling is avoided; a highly desirable result under a peak power constraint. Furthermore, the performance of the proposed EA-receiver is only 0.25 dB away from the coherent detection (with differential encoding) lower bound for the modulations considered. For quadrature phase-shift keying at a bit-error rate of 10/sup -4/, our EA-receiver with N=64 outperforms a decision feedback detector by 1 dB (L=1) and conventional ST-differential detection by more than 2.5 dB (L=2). Note that the complexity of our receiver, per symbol decision, is essentially independent of N and is comparable to that of a conventional ST-differential detector. The conclusion is reached that the proposed encoder/receiver pair is a promising alternative to currently known noncoherent techniques employing Alamouti-type ST-modulations.     

多象限光探测器组件研究

介绍了多象限探测器光敏面的设计,讨论了简易制导用多象限光探测器组件的特点.设计了一种新型九象限探测器及其组件,结果表明该器件具有响应速度快、抗冲击能力强等特点.     

Acquisition of Pseudonoise Signals by Recursion-Aided Sequential Estimation

An improved method of acquisition of pseudonoise signals (RARASE) is described and analyzed. This method is an outgrowth of the RASE method, rapid acquisition by sequential estimation. In the new method, the known recursion relation of the PN signal is used to determine if a short estimate of the state of the received PN signal is probably correct and if, consequently, an attempt should be made to track with that estimate. A high proportion of the incorrect initial state estimates can be discarded with relatively simple logic. Analyses are provided for a range of implementations from the simplest, a single 3-input modulo-2 gate, to multiple logic gates and for both a simple in-lock detector and a sequential detector. Significant improvement in acquisition time is shown for long PN signals and for the signal-to-noise range of -13 dB to +3 dB. Acquisition time reduction by a factor of 7.5 is calculated for a PN signal of length2^{15}-1bits compared to the sequential estimation (RASE) method using a simple in-lock detector. Reduction by factors of 1.5 to 3.5 is calculated using the sequential detector.     

一种高速、宽动态范围检波器的研制

微波检波器具有结构简单、使用方便的特点,是射频微波领域的一种常用器件。基于微带混合电路技术,研制了一种高速、宽灵敏度动态范围的脉冲检波器。仿真设计了带宽为5.6~13.8 GHz的宽带带通滤波器和3 GHz的宽阻带低通滤波器作为检波器的输入输出电路。该检波器可以对6~12 GHz频段内、功率为-8~16 dBm的脉冲调制信号进行检波,灵敏度动态范围约25 dB,响应时间小于3~4 ns。