Conformal array controlled by photonics

A 96-element conformal array controlled by photonics was built and tested for airborne radars. The L-band array consists of 1 km fibre-optic links and a photonic time shift network. There was no beam squint (shift in angle) as the frequency sweeps over the entire band (850-1400 MHz). A nanosecond impulse response was measured to demonstrate a 50% instantaneous bandwidth (550 MHz), corresponding to a 30 cm range resolution     

一种宽带光控相控阵天线实验系统

本文介绍了一种宽带光控相控阵天线实验系统,阐述了采用光学技术控制的S波段96单元阵列的系统设计与性能,重点说明该系统的宽带特性.该系统采用了一种基于RF开关的五位光延迟网络实现宽的瞬时带宽.实验结果表明,在2.5GHz~3.5GHz频带内,波束指向未出现偏移.     

频率步进相控阵雷达原理与实现方案的研究

宽带相控阵雷达是当前雷达技术的发展方向之一;瞬时宽带相控阵雷达的带宽受孔径渡越时间的限制,会造成雷达波束指向的变化。由于频率步进信号是一种瞬时窄带、合成宽带的雷达信号,可以通过脉间配相的改变解决孔径渡越时间、波束指向变化等问题。文中提出了频率步进宽带相控阵雷达的基本原理,并给出了几种频率步进相控阵雷达的实现方案。     

Analysis of a true time delay photonic beamformer for transmission of a linear frequency-modulated waveform

A generalized conversion matrix (GCM) and numerical analysis are used to study the distortions suffered by a linear frequency-modulated radio frequency (RF) pulse while propagating through photonic links to be used in wideband phased arrays. The analysis shows the effects of dispersion of all orders, coherent crosstalk and nonlinearity of the optical components on the RF pulse, and the high performance needed to achieve acceptable RF performance of the temporal (impulse) response. The effects of the electrical-to-optical (E/O) and optical-to-electrical (O/E) conversions are also considered. Using the GCM, the optical amplitude and phase fluctuations are converted into their RF counterparts, thereby reducing the optical problem into the well-understood RF domain. A photonic wavelength-controlled true delay device is experimentally shown to achieve good RF performance over a 4-GHz bandwidth, with predicted sidelobe levels below 30 dB.     

基于宽带阵列的数字信道化接收机设计与实现

数字化宽带接收机提高了接收信号的频域覆盖带宽,但往往灵敏度降低而难以检测弱小信号。既追求足够宽的频谱带宽,又提高强杂波背景中弱小目标检测能力,是本文研究的出发点。本文基于宽带相控阵接收机的工程实践,讨论了基于频域抽取的信道化接收机设计原理,设计了一个400M瞬时带宽阵列接收机的工程样机,并成功应用于某多波束阵列接收系统。实验结果表明,该信道化宽带接收机实现了超远程对雷达脉冲信号的检测,具有一定的工程借鉴价值和理论指导意义。     

基于FPGA的超宽带数字波束形成技术

随着高速ADC和高性能FPGA芯片工艺技术的飞速发展,芯片的小型化和集成化促进了电子战系统瞬时覆盖带宽由几十兆赫兹上升到几百兆赫兹甚至到吉赫兹量级,属于超宽带范畴.为了获得更远的探测距离性能,具备同时对多个辐射源侦测的能力,需要瞬时形成多个数字波束对目标区域密集覆盖.针对宽带时域校准与合成处理资源占用多、形成波束少的缺...     

Dual polarization stacked microstrip patch antenna array with verylow cross-polarization

This paper describes the development and performance of a wideband dual linear polarization microstrip antenna array used in the Danish high-resolution airborne multifrequency polarimetric synthetic aperture radar, EMISAR. The antenna was designed for an operating frequency of 1.25 GHz±50 MHz and was built as an array of 8×2 probe-fed stacked microstrip patches. The feeding network is constructed in microstrip and is capable of handling 6 kW of peak input-power at an altitude of 45000 ft (unpressurized). The impedance bandwidth (return loss better than -14 dB) of the antenna is 10%, the isolation between the horizontal and the vertical ports of the array is 50 dB and the cross-polarization suppression is 40 dB. A new design principle for simultaneously achieving very low cross-polarization and low side lobes in dual linear polarization antenna arrays has been applied     

基于OpenVPX平台的宽带数字阵列雷达接收系统设计

本文介绍了一套宽带全数字阵列实验系统。接收天线采用8单元线阵,工作频率为1~3GHz,瞬时带宽为500MHz。系统包含2个4通道高速ADC,每通道采样率为1.2GSPS,可实现对模拟信号的射频直接采样。信号处理机基于模块化思想设计,采用OpenVPX总线。通过多级子阵进行分级处理,具备高度的可拓展性,能够很方便的拓展成更大规模数字信号处理系统。本文结合系统架构提出了一种灵活的信号处理流程并利用该系统进行了探测实验。实测数据处理结果验证了实验系统的有效性和灵活性。      

双光频梳辅助的微波频率测量方法北大核心CSCD

为实现大频率范围内多微波频率的高精度即时测量,提出了一种基于双光频梳和法布里-珀罗滤波器(Fabry-Perot filter,FPF)的微波频率测量方案。将待测微波信号通过单边带调制加载在一路光频梳上进行频率复制,再将调制后的光信号通过一个法布里-珀罗滤波器进行信道分割。FPF的输出信号和另一路光频梳耦合后通过光解复用器实现信道化接收。通过设置合适的系统参数,可使得每个信道输出的拍频信号在同一窄带中频频段内。基于频率-光功率映射的原理,通过判断信号的存在性即可确定未知信号所处的频率段,实现信号频率的粗估计。通过对目标信道输出的微波信号进行采样、模数变换和信号处理可实现未知信号频率的高精度测量。通过实验仿真验证了所提方案的有效性,频率测量误差在±2.5 MHz内。     

Controlling resonance frequencies in antennas to achieve wideband operation

A novel antenna design method for controlling resonance frequencies is presented. This method can be realised by simply inserting a spiral inductance and a gap capacitance into a conventional loop-type antenna, and this technique remarkably enhances an impedance bandwidth without increasing the antenna size. The proposed antenna has been designed to have 530 MHz (975?1505 MHz) and 150 MHz (2410?2560 MHz) dual bands (VSWR = 2.5), and can be effectively used as an internal antenna for global system for mobile communications (GSM) and Bluetooth bands. These wideband characteristics provide a critical advantage because the shift of an antenna operation frequency increases when it is near various other components.     

用于电子战系统的微波光链路

微波光链路利用光纤实现信号的分发、传输和处理,它具有带宽大、重量轻、抗干扰等优点,在相控阵、多波束形成等电子战系统中具有很好的应用前景。但是其噪声系数、动态范围等方面的劣势也限制了其实际工程应用。文章主要从理论上分析了微波光链路的噪声系数、动态范围性能的限制因素。并通过试验测试给出了在现有工艺水平条件下微波光链路可以达到的性能指标:在1GHz瞬时带宽下动态范围大于40dB,噪声系数小于5dB。     

宽带相控阵天线波束控制算法分析与优化

宽带相控阵天线在瞬时宽带工作模式下,天线方向图的波束指向将不可避免地出现色散现象,可在天线单元或子阵级采用延时器以改善色散问题。针对延时器、移相器控制码的计算方法,文中在延时剩余法的基础上,提出了中频随动法和自适应最小步长两种新算法。两种算法不仅具有更好的适应性,而且能够改善天线宽带方向图性能。     

Wideband Channel Sounder With Measurements and Model for the 60 GHz Indoor Radio Channel

In this paper, a wideband channel sounder and measurement results for the short range indoor 60 GHz channel are presented. The channel sounder is based on a 1 gigasamples/s dual channel arbitrary waveform generator and A/D converter/software demodulator, which synthesize and detect a baseband PN sequence with 500 MHz bandwidth. A heterodyne transmitter and receiver translate the baseband PN sequence to and from the 60 GHz band. Ten channel measurements taken across the 59 GHz to 64 GHz range are concatenated to provide a continuous channel measurement covering 5 GHz of bandwidth, resulting in 0.2 ns time domain channel impulse response resolution. The dynamic range and maximum sensitivity performance of the channel sounder are discussed in detail. Comparisons of results with a vector network analyzer based system are shown to verify the accuracy of the sounder. In an extensive measurement campaign with vertically polarized omnidirectional antennas, several different rooms (offices, labs, conference rooms and others) in four different buildings have been investigated. Over 700 channel measurements are the basis for a comprehensive characterization of the short range 60 GHz indoor radio channel with omnidirectional antennas. Finally, a simple stochastic static multipath channel model is derived from the measurement results.     

宽带雷达中频直接采样与高速存储系统设计与实现

该文针对大瞬时带宽的宽带雷达回波信号中频直接采样需要解决的采样速率和高速海量数据实时连续存储等问题,首先根据带通信号无混叠采样条件确定了系统的采样速率,并依此提出了数字正交解调、缓存与高速实时无丢失存储等方案并进行了设计与实现。研制的中频信号高速采集实时存储系统基于机架服务器平台,采用QDRII SRAM 作为缓存,以PCIe 接口为数据传输通道。系统在某相控阵雷达实验平台中得到应用,通过外场实测,性能良好,为宽带雷达回波中频直接采集提供一种可行的实现方法。      

微波光子雷达逆合成孔径成像

微波光子逆合成孔径成像雷达,发挥光子大带宽、低传输损耗、抗电磁干扰等优势,可以提升成像分辨率,并有助于构建分布式阵列雷达,实现精确的三维成像。本文介绍了中国科学院空天信息创新研究院在微波光子雷达逆合成孔径成像方面的成果。首先,搭建了微波光子雷达,基于光子倍频技术产生宽带雷达信号,基于光子去斜处理进行回波信号接收,系统工作在Ku波段,带宽600MHz,实现了对暗室内合作目标和外场非合作目标的二维ISAR成像。在此基础上,结合光射频传输技术和波分复用技术,搭建一发多收的微波光子光纤分布式阵列雷达,在实验室内实现了对3个角反射器的精确三维成像。上述试验结果验证了微波光子技术应用于雷达成像领域的可行性和提升系统关键性能的潜力。     

一种宽带信号数字下变频的实现方法

在宽带、超宽带应用中,单一信号带宽达几百兆赫兹;或者在不同中频同时调制多个信号产生的宽带信号也达数百兆赫兹,用常规的数字下变频方法很难实现。文章提出了一种基于DFT滤波器组的高效数字下变频结构,分析了该解调算法的特点和实现性能。对已知信号带宽和中频的宽带信号,对比了DFT滤波器组和多相分解算法的性能。对信号带宽和中频均在变化的信号,给出了实现思路。最后,给出了该DFT滤波器组的硬件实现方案。     

一种通用宽带FM解调电路的设计

实现了一款可用于卫星接收系统中频段电视信号的解调电路.该芯片的设计基于BiC-MOS工艺.采用5 V电源电压供电,利用单片锁相环(PLL)实现宽带FM解调,外围器件只包括本地振荡维持网络和环路反馈元件,PLL工作频率可达800 MHz.芯片内部还集成了自动增益控制(AGC)、模拟自动频率控制(AFC)模块.该芯片具有较高的信号接收灵敏度.     

宽带Chrip信号激励下功放数字预失真补偿

功率放大器(power amplifiers, PAs)会对输入的宽带线性调频信号(linear frequency modulated, LFM)引入幅度失真和相位失真,这将导致接收机脉冲压缩处理后的输出信号主瓣展宽,旁瓣电平抬高,从而恶化雷达距离分辨率甚至产生虚假目标。文中提出采用有限冲击响应滤波器(finite impulse response, FIR)模型对宽带LFM信号激励下的功放进行行为建模和数字预失真(digital predistortion, DPD)补偿。利用宽带测试平台对500 MHz 瞬时带宽LFM信号激励下峰值功率15 W 的S波段功放进行验证。实验结果表明,浅饱和和深饱和情况下FIR模型都能准确建模功放的失真特性,浅饱和情况下DPD能够补偿幅度失真和相位失真,而深饱和情况下只能补偿相位失真,经过DPD补偿脉冲压缩后的峰值旁瓣电平都明显降低。     

A 20 GHz microwave sampler

A microwave sampler circuit which operates over the frequency band of 1-20 GHz and has a number of novel features is described. These features include a wideband microstrip-to-slot balun and a wideband active isolator the function of which is to reduce the local oscillator to RF leakage from the input port of the sampler. The signal-to-noise ratio over the input bandwidth is greater than 20 dB at an input power level of -32 dBm. This signal-to-noise ratio was measured in an IF bandwidth of 175 MHz and includes the contribution from the IF amplifier. The sampler, which is made on alumina using MIC techniques, has an integrated impulse generator driven with a sinusoidal local oscillator of only 20 dBm over the frequency band of 250-350 MHz. The IF signal is in the 10-175-MHz band. The RF input VSWR is better than 2:1 up to 20 GHz, and the oscillator to RF breakthrough is better than -58 dBm (-78 dBc) when driven with a local oscillator of 20 dBm. This unusually low leakage was achieved by using the active isolator prior to the sampling circuit     

基于双光学频梳的超宽带射频信号信道化合成技术研究（特邀）

随着现代通信系统的发展,宽带和高频微波射频信号在雷达,通信和信号处理等领域的应用越来越广泛。基于微波光子信道化技术,文中通过两个自由频谱范围不同的光学频梳,实现了超宽带射频信号的信道化合成。在信道化合成系统中,多个独立的窄带信号输入各个信道进行上变频,并在多外差探测中被重组成为一个具有连续频谱的宽带射频信号。在多外差探测中,干扰抑制技术的使用提高了合成射频信号可达到的最高频率。在实验中,合成了一个覆盖频率范围8.4~12.4 GHz,瞬时带宽为4 GHz的宽带射频信号。实验结果显示,干扰的抑制率达到了21 dB,表明干扰抑制技术的使用提高了输出信号的最高频率的同时有效地提高了频谱利用率。