Performance in the Primary and Secondary Processing of Pulsed Radio Signals in Passive Radar Systems

Simulation has been applied to observing, radio parameter estimating, and identifying electronic devices to estimate the performance in primary and secondary signal processing in passive radar systems for various forms of receiving and analyzing equipment.     

A Novel Method of Distance Measurement Based on Pulse Position Modulation and Synchronization of Chaotic Signals Using Ultrasonic Radar Systems

This paper deals with a novel method of transmission and receipt of a signal based on both the property of two chaotic systems generating the same chaotic signal when they are synchronized and the property of pulse position modulation (PPM) to be insensitive to the distortions of the transmission channel. The method is discussed in the context of ultrasonic radar systems, in which the transmitter and receiver, which consist of ultrasonic sensors, are near each other, and the received signal consists of the transmitted signal reflected by an obstacle. A reference sinusoidal signal is superimposed to a chaotic signal generated by a master chaotic system, and the whole signal is modulated according to the PPM method and transmitted by the sensor. The received signal is demodulated, and the demodulated signal forces a slave chaotic system to generate the chaotic signal embedded in it, which allows recovery of the sinusoidal signal by subtracting this chaotic signal from the demodulated echo. The difference of the phases of the reference sinusoidal signal and the recovered sinusoidal signal allows computation of the time of flight of the signal and, consequently, the distance of the radar system from the obstacle. The novel method is illustrated and tested by both simulation and experiments. The interference problem between the considered radar system and other radar systems ( crosstalk) is also addressed, and a solution is proposed to avoid it.     

Time-frequency-based non-stationary interference suppression for noise radar systems

The problem addressed here is non-stationary interference suppression in noise radar systems. Towards this aim, two linear time ?frequency (TF) transforms, short-time Fourier transform and local polynomial Fourier transform are used as a means of signal representation and filtering. The noise radar return signal is a wideband random signal occupying the whole TF plane, whereas the interference signal is well concentrated in the TF plane. This implies that the filtering of the received signal can be performed by using a binary mask to excise only a portion of the TF plane corrupted by the interference. Simulations carried out on the radar return signal corrupted by extremely strong non-stationary interferences confirm the effectiveness of the proposed method.     

一种超宽带零中频的微波光子信道化接收机

信道化接收技术是现代电子战和雷达系统的重要组成部分,是满足其高频段、大带宽、多通道同时接收等需求的核心使能技术。本文提出了一种基于微波光子的零中频接收机,可通过调整光频梳中心频率的方法使之与宽带RF信号组的中心频率相对应,从而实现3GHz的宽带射频信号的信道化接收,每个子信道带宽为600MHz且直接解调为I/Q基带信号。     

Suppression of smeared spectrum ECM signal

Abstract

Three electronic counter‐countermeasures (ECCM) techniques for suppressing smeared spectrum (SMSP) jamming, a new electronic counter measures (ECM) technique, are presented. The analytical representations of the SMSP ECM signal in the time domain and the frequency domain are first derived, and then the differences between the SMSP jamming signal and the radar linear frequency modulation (LFM) signal are analyzed. Based on the differences, a jamming suppression system specifically for SMSP jamming interference excision is designed, which applies three different signal processing tools, i.e. fractional Fourier transform (FRFT), Fourier transform (FT) and atomic decomposition (AD). The jamming suppression performance of the presented methods is evaluated through simulations. The simulation results show that the presented methods can successfully suppress SMSP jamming.     

Signal Processing in Noise Radar Technology [Editorial]

Noise Radar Technology (NRT) addresses the increasing performance demands placed on both military and civilian radar systems by enhancing their reliable operation in congested, unfriendly or hostile environments. For instance, many surface and maritime radar systems used for national border surveillance, traffic control, indoor surveillance, etc. must be able to operate in a congested electromagnetic environment without performance degradations caused by intentional external electromagnetic interference (EMI). Even greater demands are placed on military air, space, maritime and battlefield radar systems that must reliably operate in congested and hostile environments characterized by deliberate and adaptive jamming. In addition, many military missions require covert radar operation, which increases the complexity of radar signal processing.     

Transient and overvoltage recovery testing of analog-to-digitalconverters

The dynamic performance (the noise effective number of bits, the spurious-free dynamic range, and the signal-to-noise ratio) of the high-speed analog-to-digital (A/D) converters used in radar systems can be characterized by a spectral analysis test consisting of a series of sinusoidal signals of different frequencies and amplitudes. Some radar systems are exposed to large noise impulses either from an environment or hostile electronic countermeasures (ECM). For these systems, in order to minimize system impact, the radar specification requires that the converters meet transient and overvoltage recovery specifications. In order to verify these requirements, we developed a test method which is a variant of the standard sine-wave test. The transient and overvoltage recovery performance of the converters is determined by applying a poised waveform and determining the time required to recover from the pulse. We designed and built a special test fixture that produces a pulse that is clean to 12-bits accuracy with a 400-ohm load. This paper describes the characteristics of two different 12-bit, 4-MHz converters that were tested, the test equipment, the data analysis, and the transient and overvoltage recovery test results     

Passive bistatic radar based on target illuminations by digital audio broadcasting

A practical passive bistatic radar that is based on target illuminations by digital audio broadcasts is described. As with all such radars, direct signal interference (DSI) is identified as a major limitation, the effect being exacerbated by the multiplicity of illuminators. In addition, such multiplicity can also make the extraction of the original transmitted signal difficult. DSI is reduced by a combination of analogue and digital null formation and isolation by use of cross polarisation. Fast techniques are developed for signal extraction and digital null formation, allowing these operations to be achieved in real time. Both the hardware and algorithms of the system are described and representative radar observations are included to show the systems effectiveness.     

Target localisation techniques and tools for multiple-input multiple-output radar

This study presents a comparative study of coherent and non-coherent target localisation techniques for multiple-input multiple-output (MIMO) radar systems with widely distributed elements. Performance is evaluated based on closed-form solutions developed for the best linear unbiased estimator (BLUE) for each of the localisation methods. These estimators afford insights into the relation between radar locations, target location and localisation accuracy. In particular, the means squared error of the BLUE is factored into a term dependent on signal and processing characteristics and a term dependent on sensor locations. The latter is referred to as geometric dilution of precision (GDOP). The best achievable accuracy for the coherent case is obtained, and a comparative study with the non-coherent case is presented. MIMO radar systems with coherent processing are shown to benefit from a gain because of coherent processing among sensors. This gain is referred to as coherent localisation gain, and it is proportional to the ratio of the signal carrier frequency to the effective bandwidth (a large ratio for typical signals). The footprint of multiple transmit/ receive sensors results in a gain, referred to as MIMO gain, for both processing techniques. The MIMO gain is proportional to the product of the number of transmitting and receiving sensors. Analysis of the MIMO gain through the use of GDOP contour maps demonstrate the achievable accuracy at various target locations for a given layout of sensors.     

Ultra-wideband radar noise reduction for target classification

The authors describe a calibration procedure for ultra-wideband (UWB) radar systems in order to measure the frequency-dependent transfer function or radar cross-section, respectively, of objects with a high computational efficiency. The benefit of using UWB pulses is that only one measurement is required for covering several GHz. However, the signal processing steps contain a deconvolution operation producing spike artefacts. They were successfully removed by the calculation of frequency-dependent signal-to-noise ratio and a following Wiener filtering. The proposed method was verified by some elementary targets of which the size of the objects were determined.     

Adaptive beamforming for high-frequency over-the-horizon passive radar

Target detection and tracking systems using emitters of opportunity have received significant interest recently, especially those which exploit VHF and UHF broadcasts as signal sources in so-called passive radar systems. Here, the authors discuss an experimental system in the high-frequency (HF) band, where due to long-distance ionospheric propagation of radio waves in the 3?30 MHz spectrum, the illuminator may be located well beyond the line-of-sight. In this study, live data was recorded by a high dynamic range multichannel digital receiver connected to a two-dimensional (L-shaped) antenna array, and signals from an uncooperative HF over-the-horizon (OTH) radar transmitter have been captured and analysed. As a preliminary step towards the development of a general HF-OTH passive radar system, the scope of this work is to compare the performance of conventional and adaptive spatial processing techniques in terms of their ability to cancel direct-wave interference and protect useful signal echoes to detect a small cooperative aircraft target. In particular, an alternative adaptive beamforming method specifically tailored to this application is proposed, and its practical performance is compared with classical and standard adaptive beamforming approaches. GPS data measured on-board the cooperative aircraft provided accurate ground truth of the flight path, enabling target profiles in bi-static range, Doppler frequency and direction-of-arrival (azimuth/elevation) to be calculated as a function of time. This information permitted the different processing schemes to be evaluated with a high degree of confidence. The experimental system and live data analysed are exclusively from the HF Radar program of the Defence Science and Technology Organisation (DSTO), Australia.     

Navy Programs in Superconducting Technology

A review of U.S. Navy efforts in superconducting technology is given. Programs include development of superconducting magnets for motors in ship propulsion systems and to generate magnetic moments in mine sweeping systems. A program to develop superconducting quantum interference devices (SQUIDs) for detection of mines and buried ordnance has successfully been demonstrated. In electronic applications, superconducting filters, resonators, and antennae are being developed for radar, communication, and space systems. Concurrent with these superconductivity programs are efforts to improve the efficiency, reliability, and affordability of refrigeration systems.     

Compact laser radar and three-dimensional camera

A novel three-dimensional (3D) camera is capable of providing high-precision 3D images in real time. The camera uses a diode laser to illuminate the scene, a shuttered solid-state charge-coupled device (CCD) sensor, and a simple phase detection technique based on the sensor shutter. The amplitude of the reflected signal carries the luminance information, while the phase of the signal carries range information. The system output is coded as a video signal. This camera offers significant advantages over existing technology. The precision in range is dependent only on phase shift and laser power and theoretically is far superior to existing time-of-flight laser radar systems. Other advantages are reduced size and simplicity and compact and inexpensive construction. We built a prototype that produced high-resolution images in range the (z) and x-y.     

线性调频信号检测的快速调频变换算法

线性调频（LFM）信号是雷达和声呐系统中常用的宽带信号。介绍了一种快速调频变换算法,用于线性调频信号的检测。首先对该方法进行了详细的推导和讨论,讨论了该快速算法中使用到的部分傅立叶变换快速算法,并研究了快速调频变换算法的计算量。最后,实验表明了快速调频变换算法有良好的信号检测性能。     

某新型战场侦察雷达信号处理系统研究

为有效、经济地提高部队及院校对某新型战场侦察雷达的训练,在LabVIEW软件平台上设计某新型战场侦察雷达的信号处理系统。采用模块化编程方法,建立伪码调相准连续波雷达的数字下变频、脉冲压缩、动目标显示、动目标检测、恒虚警检测和PPI显示模块,设计系统的人机交互界面。结果表明:设计的某新型战场侦察雷达的信号处理系统可以有效地模拟该雷达的信号处理过程及PPI显示,操作方便,易于扩展和部队使用。     

Using a van-mounted FM-CW radar to detect corner-reflectorroad-boundary markers

The motivation for this experimental work is to explore a car-borne radar to assist the river of a vehicle in determining where the vehicle is located within the road during adverse (blizzard and/or foggy) weather conditions. This paper discusses the advantage of frequency-modulated continuous wave (FM-CW) radar to achieve such a system. Results are reported of detecting corner reflectors placed on the shoulders of the road with a van-mounted FM-CW radar. The corner reflectors were used as markers of road boundaries. These reflectors were ranged with two radar channels operating simultaneously in real time. The radar signals were processed using a digital signal processing (DSP) circuit board. It is shown that the radar could map the corner reflectors on single and/or two road shoulders in real-time operation at a speed up to 50 km/h. This kind of car-borne radar aids snow-plowing work in a heavy snow regions     

一种新的相位编码信号多普勒补偿算法研究

相位编码信号是一种多普勒频率敏感信号,而且码长越大,对多普勒频率越敏感,严重影响了雷达对高径向速度目标和远距离目标探测的能力。该文在分析伪码序列与多普勒容限关系的基础上,提出一种新的伪码调相准连续波雷达的多普勒补偿算法。该算法将回波信号取平方后送到动目标检测(MTD)滤波器中,通过提取回波信号中的多普勒频率信息,进行多普勒补偿。从仿真结果可以看出,该算法能够有效地降低多普勒频率对脉冲压缩结果的影响,验证了方法的可行性。     

Signal-to-noise ratio analysis to estimate ocean wave heights from X-band marine radar image time series

This work analyses the structure of the different contributions to the image spectrum derived by the three-dimensional Fourier decomposition of sea clutter time series measured by ordinary X-band marine radars. The goal of this investigation is to derive a method to estimate the significant wave height of the ocean wave fields imaged by the radar. The proposed method is an extension of a technique developed for the analysis of ocean wave fields by using synthetic aperture radar systems. The basic idea behind this method is that the significant wave height is linearly dependent on the square root of the signal-to-noise ratio, where the signal is assumed as the radar analysis estimation of the wave spectral energy and the noise is computed as the energy due to the sea surface roughness, which is closely related to the speckle of the radar image. The proposed method to estimate wave heights is validated using data sets of sea clutter images measured by a marine radar and significant wave heights derived from measurements taken by a buoy used as reference sensor.     

Mutual interference and low probability of interception capabilities of noise radar

Recently, there has been considerable interest in noise radar over a wide spectrum of applications, such as through-wall surveillance, tracking, Doppler estimation, polarimetry, interferometry, ground penetrating or subsurface profiling, detection, synthetic aperture radar (SAR) imaging, inverse SAR imaging, foliage penetration imaging etc. Major advantages of using noise in the transmit signal are its inherent immunity from radio frequency and electromagnetic interference, improved spectrum efficiency, and hostile jamming as well as being very difficult to detect. The basic theory of digital signal processing in noise radar design is treated. The theory supports the use of noise waveforms for radar detection and imaging in such applications as covert military surveillance and reconnaissance. It is shown that by using wideband noise waveforms, one can achieve high resolution and reduced range estimation ambiguity. Mutual interference and low probability of interception capabilities of noise radar are also evaluated. The simulation results show the usefulness of the noise radar technology to improve on conventional radars.