声表面波延迟线

声表面波延迟线是在雷达和通信系统中应用非常广泛的器件.文中结合实用声表面波延迟线器件的设计实例,介绍了折叠式固定延迟线结构原理和设计计算,克服了传统延迟线受基片材料长度和器件尺寸的限制,满足了雷达、通信等电子设备中对电信号的长延迟需求;同时还讨论了为满足超高频的应用需求和增加相对带宽,所采用的谐波和倒相换能器的设计方法.     

A Low-Power High-Sensitivity X-Band Rail SAR Imaging System [Measurement's Corner]

Wideband radar imaging with range gating and high sensitivity can be achieved with the use of low-cost commercially available narrowband IF filters. Such filters reduce the effective receiver noise bandwidth of the radar system. This allows for high sensitivity, comparable to that of single-sideband radio receivers, while at the same time acquiring de-chirped wide-band received waveforms. A carefully developed radar architecture, based on the use of these IF filters, is shown in this paper. This radar architecture is then implemented in an X-band linear rail synthetic-aperture-radar (SAR) imaging system. The X- band rail SAR is a linear FM-chirped radar, which chirps from approximately 7.5 GHz to 12.5 GHz. The radar front end is mounted onto an eight-foot-long linear rail. The transmitted power is adjustable to 10dBm or less. It will be shown that objects as small as groups of pushpins in free space can be imaged using transmitted power as low as 10 nW. These results are compared to previous direct-conversion X-band FMCW rail SAR work. A high-sensitivity X-band rail SAR such as this could be useful for measuring low-radar-cross-section (RCS) targets. This radar could be used in high clutter environments that require a range gate. This low-power X-band rail SAR could be useful for operation in restricted transmission areas, where maximum radiated power is severely limited. Other applications include any that require low transmitter power, such as automotive radar.     

数字调频连续波测距雷达方程

数字调频连续波（DFMCW）测距雷达有多项工程设计参数,包括由于连续波收发隔离度限制发射高功率Ptmax、采用数字方式产生DFMCW信号的扫频带宽B、扫频时宽T（扫频信号重复周期）及DFMCW测距雷达接收机的中频量程带宽Bn、接收机动态压缩特性和采用数字FFT信号处理器的采样频率fs等。将对这些设计参数的定义进行说明,并与一般脉冲雷达或线性调频（LFM）脉冲压缩雷达的设计参数进行比较和等效估算,最后推导出DFMCW测距雷达工程使用的方程式。     

一种数字式微波延迟线设计

通过混频将微波信号下变频到中频,在中频进行数字化,并采用循环存取法完成数字信号延迟处理,最后再将数字信号还原成模拟信号并上变频回与输入信号频率相同的微波频段,最终设计出频率4 300MHz、带宽70MHz、最大延迟时间50μs、延迟步进5ns的微波频段延迟线,该产品有很好的直通及三次信号抑制性能。     

Waveguide-to-microstrip transition with integrated bias-T

A novel device, a waveguide-to-microstrip transition with an integrated bias-T, is presented. The substrate-based planar structure comprises a waveguide E-probe, shaped as a radial line. The probe couples the RF field of a full-height waveguide to a microstrip line or directly to an active component, e.g., a transistor or diode in a mixer or direct detector. The radial probe is connected on its wide side to another port via a specially shaped high impedance line that provides RF/DC isolation. This port can then be used to inject DC and/or extract IF signals. The design of the presented structure was done using CAD (3-D EM simulation) and an X-band device was produced and fully characterized. The measured performance is in excellent agreement with the simulations; the device has return loss better than -20 dB, insertion loss less or equal to -0.15 dB and isolation for the bias-T line better than -20 dB. RF bandwidth for the transition is 30% of the central frequency.     

X波段可编程光钎传输微波延迟系统

介绍了X波段可编程光纤传输微波延迟系统的基本工作原理及系统组成。叙述了该系统的研制过程,包括:光发射模块、光接收模块和光纤延迟链路的设计。微波延迟系统具有低插入损耗、低延迟相关损耗,输出幅度稳定,快速延迟切换速度(<0.5 ms)等优点以及单板机编程和计算机控制界面。该延迟系统传输微波频率范围:9~11 GHz,延迟时间范围为1.013 3~1.646 7μs,延迟精度为0.5 ns,延迟时间可以在1.013 3~1.646 7μs范围内步进调节,延迟时间控制实现了计算机控制。     

机场天气雷达双通道数字中频处理系统的实现

机场天气雷达要求能够从复杂的天气环境中识别不同的天气状况以保障航空飞行安全,其接收机大动态以及抗噪性能设计对雷达至关重要。在分析模数转换器（ADC）对雷达中频接收机动态范围制约的基础上,根据中频带通采样和数字下变频的原理,实现了基于现场可编程门阵列的双通道ADC采样数字中频处理系统,并给出了系统的设计原理、方法以及测试结果。通过对双通道ADC采样的数字中频处理系统的实现,能够很好地提高天气雷达接收机的动态范围,并应用于机场多普勒天气雷达数字中频接收机。     

Doppler estimation using a coherent ultrawide-band random noiseradar

The University of Nebraska has developed an ultrawide-band (UWB) coherent random noise radar operating over the 1-2 GHz frequency range. The system achieves phase coherence by using heterodyne correlation of the received signal with a time-delayed frequency-shifted replica of the transmit waveform. Knowledge of the phase of the received signal and its time dependence due to target motion permits the extraction of the mean Doppler frequency from which the target speed can be inferred. Theoretical analysis, simulation studies, and laboratory measurements using a microwave delay line showed that it was possible to estimate the Doppler frequency from targets with linear as well as rotational motion. Field measurements using a photonic delay line demonstrated the success of this technique at a range of about 200 m at target speeds of up to 9 m/s. Analysis shows that the accuracy with which the Doppler frequency can be estimated depends not only on the phase performance of various components within the system, but also upon the random nature and bandwidth (BW) of the transmit waveform, and the characteristics of unsteady target motion     

有源相控阵天线瞬时宽带性能改善研究

采用无色散特性的模拟或数字移相器会导致天线波束指向随频率发生变化,即相控阵天线的孔径效应。工程上一般在子阵级别上采用色散特性的实时延迟线拓展相控阵天线瞬时带宽,但是子阵级延时量化误差会产生周期性栅瓣,导致天线副瓣性能恶化。文中提出在通道(或多通道收发组件)上设置小位延迟线、与子阵级大位延时线叠加使用,消除或改善子阵级延时误差造成的性能恶化。结合X波段有源二维阵列天线,对单元级、子阵级、子阵+单元两级三种情况进行了仿真。仿真结果表明,子阵+单元两级延时方法在扩展相控阵天线瞬时带宽的同时,能明显改善相控阵天线的副瓣特性,且具有较强的工程可实现性。     

大动态数字接收机的设计与实现

介绍了 X 波段相控阵雷达大动态数字接收机的设计和实现方法,对接收机的灵敏度、 噪声系数及动态范围等主要技术指标进行了分析和计算,并给出了各主要模块的实现方法。     

X波段多功能频率合成器设计

文章介绍了一种X波段多功能频率合成器的设计方法,该方法以直接数字频率合成(DDFS)和直接式模拟合成技术为基础,通过优化频率规划和引入相位噪声清除技术,改善了频率合成器杂散和相位噪声性能。雷达激励器采用了"任意波形产生(AWG)+IQ调制"结构,除产生雷达激励波形外,兼具回波模拟器功能,实现了一个硬件平台,两种功能的一体化设计,具有良好的工程应用价值。文章给出了原理框图,并对相位噪声、杂散等方面做重点的介绍和分析,文末给出了测试结果。     

雷达HRRP目标识别系统参数分析

雷达高分辨距离像在实现自动目标识别方面具有较大潜力,其识别性能与雷达系统参数,如雷达工作频率、信号带宽等有关。此外,用于采集识别器训练数据的雷达接收机的特性与实际工作的雷达接收机的特性会有所不同,也会影响到识别性能。文中对上述参数对识别性能的影响进行了分析和评估,所得到的结果对目标识别雷达的系统设计具有参考价值。     

A 100-MHz bandpass sigma-delta modulator with a 75-dB dynamic range for IF receivers

A fourth-order switched-capacitor bandpassΣ△modulator is presented for digital intermediatefrequency (IF) receivers.The circuit operates at a sampling frequency of 100 MHz.The transfer function of the resonator considering nonidealities of the operational amplifier is proposed so as to optimize the performance of resonators.The modulator is implemented in a 0.13-μm standard CMOS process.The measurement shows that the signal-to-noise-and-distortion ratio and dynamic range achieve 68 dB and 75 dB,respectively,over a bandwidth of 200 kHz centered at 25 MHz,and the power dissipation is 8.2 mW at a 1.2 V supply.     

Design of Conical Transmission Line Power Combiners Using Tapered Line Matching Sections

An axially symmetric power combiner, which utilizes a tapered conical impedance matching network to transform ten 50-Omega inputs to a central coaxial line over the X-band, is presented. The use of a conical line allows standard transverse electromagnetic design theory to be used, including tapered impedance matching networks. This, in turn, alleviates the problem of very low impedance levels at the common port of conical line combiners, which normally requires very high-precision manufacturing and assembly. The tapered conical line is joined to a tapered coaxial line for a completely smooth transmission line structure. Very few full-wave analyses are needed in the design process since circuit models are optimized to achieve a wide operating bandwidth. A ten-way prototype was developed at X-band with a 47% bandwidth, very low losses, and excellent agreement between simulated and measured results.     

P 波段超宽带雷达接收机的设计与实现

P 波段合成孔径雷达因其穿透性强而受到广泛关注,但是因其频段低而带宽宽,使得接收机的设计面临诸多挑战。文中介绍了一种工作中心频率为330 MHz 、相对带宽达60￡￥ 、动态范围达80 dB 的合成孔径雷达接收机的设计过程。提出了P 波段超宽带雷达接收机的设计方案;同时,对噪声系数、增益、动态范围等关键指标进行了详细的分析和计算。解决了大动态范围增益控制、宽带幅频平坦特性、带外抑制度等技术难题。设计完成的接收机各项指标均达到或优于系统要求,并成功应用于雷达系统中。     

Ku波段高性能声体波微波延迟线的设计与优化

通过优化换能器拓扑结构、腔体结构和可调的微带匹配网络设计,研制出中心频率14 000 MHz、带宽1 500 MHz及延迟时间0.5 μs的Ku波段声体微波延迟线.该产品的插入损耗为-56 dB,直通抑制大于45 dB,三次渡越抑制大于55 dB,产品综合性能指标优异.     

雷达信号模拟器的中频信号产生器设计

针对侦察系统性能指标的检测,雷达信号模拟器是常用工具,而其以中频信号产生模块为主。采用ADSPBF533与高性能FPGA硬件平台,利用直接数字频率合成技术产生各种雷达中频信号波形数据,生成雷达中频信号,再经过对该中频信号进行变频、放大、滤波,即可形成模拟雷达信号,一个中频信号产生模块包括1块通信控制板和3块中频信号产生模块,并可同时模拟出12部雷达中频信号。     

94-GHz TWT for military radar applications

For future military radar applications, high frequency, light-weight TWTs become more and more important. To cover this market, Thomson Tubes Electroniques GmbH several years ago started the development of a 94-GHz TWT. The goal of this program was a TWT (double comb delay line structure) in the 94-GHz frequency range with an instantaneous bandwidth greater than 500 MHz (tunable within 1 GHz) and an output peak power greater than 200 W in the center of the band (150 W over the band) for a duty cycle of max. 10%. The basic design and main test results of the 94-GHz TWT are the content of this paper     

A Single-Ended Resistive $X$-Band AlGaN/GaN HEMT MMIC Mixer

A broadband highly linear X-band mixer in AlGaN/GaN monolithic microwave integrated circuit technology has been designed, processed, and characterized. The design is based on a 4 times 100 mum AlGaN/GaN HEMT in a single-ended circuit topology. The mixer has an IF bandwidth of 2 GHz with a conversion loss (CL) of < 8 dB across the X-band with a minimum CL of 6.9 dB at 11 GHz. The large-signal performance is exemplified by IIP 3 levels of 22 and 30 dBm at local oscillator drive levels of 15 and 23 dBm, respectively. A minimum noise figure of 9 dB is achieved at 11.6 GHz.     

An IF Cross-Pol Canceller for Microwave Radio Systems

This paper discusses cross-pol cancellation for microwave radio system applications. A model for cross-pol interference coupling during multipath fades is postulated and some preliminary performance goals are presented. A design for an IF canceller consisting of cross-coupled adaptive tapped delay lines and a digital controller is presented and discussed. Predicted canceller performance as a function of tap spacing and number is discussed and compared to measured data. The design of a two-channel, dual-polarized lab fade simulator is presented, and methods to characterize canceller performance and fade parameters are also briefly discussed.