Radar receiver optimization for a continuously scanning antenna

The optimum coherent radar receiver configuration is derived for a continuously scanning antenna on the basis of maximizing the available energy for a given processor complexity. Included in the analysis are the length of the coherent dwell, the size of the discrete Fourier transform and the degree of weighting used for Doppler filtering, and the use of overlapped processing windows. Gaussian shapes for the processing window and antenna mainbeam are assumed in order to make the analysis tractable     

MMW system trade-offs

A brief review is given of the current state of knowledge of millimeter-wave atmospheric propagation and clutter characteristics and the detection performance of two air-to-ground fire-control systems evaluated in terms of their ability to detect a 40-m² target in the presence of atmospheric attenuation and three types of clutter. Generally, the 35-GHz system considered performed better in terms of signal-to-noise ratio performance and in signal-to-clutter ratio performance for light clutter. In heavy clutter, the 95-GHz system performed significantly better than the 35-GHz system. For 300-m altitude with refrozen snow clutter background, neither system developed a large enough signal-to-clutter radio to detect the target reliably     

DOA estimation by exploiting the amplitude modulation induced by antenna scanning

We propose a beamsplitting-like approach to estimate the directions of arrival (DOA) of multiple radar targets present in the mainlobe of a rotating antenna. The proposed method is based on the maximum likelihood (ML) technique and it avoids the need for a difference channel by exploiting knowledge of the antenna main beam pattern. Two scenarios are considered: multiple targets with unknown deterministic complex amplitudes and multiple targets with Gaussian distributed random complex amplitudes. The performance of the proposed estimator is investigated through Monte Carlo simulation and it is compared with the Cramer-Rao lower bound (CRLB).     

毫米波多普勒近程探测系统仿真

介绍了基于旋转弹丸的ADS毫米波多普勒近程探测系统的组成,建立了某武襄直升机的近程探测系统数学模型,并且对探测系统目标回波的时域、频域和STFT时频域进行了LabVIEW的仿真分析。结果表明,该多普勒近程探测系统仿真具有较好的测试性和工程实用性,在理论和工程上都具有广阔的应用前景。     

MMW radar scattering statistics of terrain at near grazingincidence

The statistical behavior of clutter observed near grazing incidence and at 95 GHz is investigated for the specific cases of bare ground, snow cover, and for a heterogeneous scene. The bare ground constitutes a homogeneous target under homogeneous conditions and the magnitude of the amplitude is Rayleigh distributed. While the snow cover is a homogeneous target, the conditions under which it was observed are heterogeneous, and the Bayes rule is employed to describe its clutter distribution. The Bayes rule integrates variations due to signal fading with the underlying variations in the backscattering coefficient associated with the heterogeneity. The heterogeneous scene is also successfully described with the Bayes rule     

Visual analysis in a deployable antenna experiment [satellite antenna]

To establish a large deployable antenna, monitoring and collimation are essential for reliable and precise deployment. We have developed an analysis method to detect shifts in several images, in which the combination of cross-correlations between images and approximations at subpixel precision enables us to detect shifts in images with a precision of up to 0.01 pixels. The LDREX mission; which was a preliminary experiment for a large deployable antenna, ETS-VIII, was performed in December 2000. During this experiment, anomalies occurred in the antenna, and deployment was aborted. To understand the cause of the anomalies, we used our visual analysis method. Using this analysis, we detected vibrating features in the antenna, which were useful for explaining the anomalies. We outline our visual analysis method and discuss its application in monitoring the deployable antenna.     

毫米波制导导弹系统误差及捕获概率研究

分析了毫米波制导导弹系统误差源及其分布特性,该误差直接决定所需导引头动态视场的大小;对导引头动态视场的影响因素进行了分析,并计算了导引头在不同条件下的动态视场,基于此计算了导引头捕获概率。研究结果可以直接应用于毫米波制导导弹的工程研制,并且可以对同类的自寻的导弹工程研制起借鉴作用。     

WiMAX dynamnic beamforming antenna

This presents our design and development of an 8-channel adaptive beaniforming antenna for new developments in radio technology: the emergence of chip-based components implementing the recently completed IEEE 802.16d-2004 (WiMAX) radio standard [1-4]. WiMAX offers the potential of long-range (up to 50 miles) and high bandwidth (up to 50 Mb~s) radio links. Although the new WiMAX standard offers the potential for using smart, adaptive antennas, this functionality has not been implemented. Our design will serve as a common platform for testing adaptive array algorithms including direction of arrival (DOA) estimation, beamforming, and adaptive tracking, as well as complete wireless communication with a WiMAX Radio. Heavy emphasis will be placed on ease of implementation in a multi-channel / multi-user environment. In the future, we hope to expand this interface to support dynamic radio channel selection via direct interaction with radio hardware or implementation of a cognitive radio system.     

Wideband array antenna concept

This presents a unique wideband array concept that includes a wideband array aperture incorporating radiating elements of different sizes and inter-element spacings. The array is a fully-filled aperture consisting of a core region surrounded by several layers of radiating elements which increase in size. By proper selection of the core region and the number of layers, one can form a beam with specified beamwidth over a five to one frequency range. The proposed concept considerably reduces the cost and complexity by decreasing the effective number of radiating elements and the corresponding receive or transmit modules. Numerical simulation results, ignoring the mutual coupling effects, are presented for array patterns at several frequencies to prove the concept. A possible beamforming concept is also included. Additional work is planned to prove the viability of the concept by taking the mutual coupling into account.     

Effectiveness of MMW aerosols in defeating a battlefieldsurveillance radar: field demonstration preliminary results

The US Army ERDEC is developing advanced aerosol systems to combat threat surveillance, fire control, and seeker systems operating in the visible, infrared, and millimeter wave portions of the electromagnetic spectrum. One such system is the M56 multispectral smoke generator, which presently operates in the visible and infrared portions of the spectrum; a millimeter wave (MMW) Module is in development to extend the M56 spectral range. This paper documents preliminary results of a field demonstration test of the M56 MMW Module. An MMW instrumentation radar was modified to simulate the scan pattern and radar parameters of a tactical battlefield surveillance radar system. A test grid was populated with both stationary and moving tactical targets, and the radar scanned the grid to simulate a surveillance radar in operation. Once a realistic tactical engagement scenario was developed, MMW aerosols were deployed to demonstrate the impact such aerosols could have on radar detection and classification performance     

Active transmitting phased antenna arrays

The benefits of using transmitting phased array antennas for radar systems are examined. Accurate performance prediction for the transmitting phased array antennas requires theories describing both the antenna system and the power generation devices. These theories were created and applied to the design and performance evaluation of the Russian 3-D mobile solid-state surveillance radar 67N6E (GAMMA-DE), a PAA designed for long-range air defense.     

Short antenna spaceborne SAR concepts

This analysis concludes that, for a “swath/azimuth resolution” (SAR) ratio not exceeding 10⁴ (as is the case for the missions designed and imagined up until now), it is possible, thanks to new imaging modes based on timing diagram saturation, to reduce the length of the antenna by two (defined along the speed vector) under equivalent performance, antenna area, onboard energy and spectral occupancy conditions. One of the advantages is that the Spotlight mode is not needed except if one wishes to exceed the ratio of 10⁴, which gives, in addition to the elimination of the operational limitations of this mode, high cost reduction possibilities with very simplified antenna architectures. These principles are applicable to all types of satellite architectures provided that the rejection of the nadir echo is done other than in the temporal domain, here too saturated. They are especially interesting for the RADAR SAIL case, lowering the costs of the RADAR satellite concept invented by CNES, based on the use of a vertical antenna placed in the orbit plane. On the one hand, they get round the length limitation related to this concept and generalise its utilisation range. On the other hand, the absence of the nadir echo (physically rejected on account of the SAIL concept geometry) enables antenna simplification to be pushed as far as possible without having to preserve a minimum number of control points required for beam nulling toward nadir and, in addition, a single diagram, that of the pencil beam, enables all incidences and modes to be covered, which simplifies the characterisation, calibration and operation of the Radar.     

Anechoic chamber wideband antenna measurements

The method is considered which consists of measurements of output antenna signals on a number of frequencies and Fourier transformation of data into time domain for separation of own antenna field and interference fields. The results of testing at serial facility for antenna measurements in an anechoic chamber are presented as for diagnosis of scattered fields, as for improvement of accuracy of antenna characteristics evaluation.     

一种弹载毫米波全极化单脉冲环焦反射面天线的设计

提出了一种弹载毫米波全极化环焦反射面天线的设计方案,设计了其结构参数,并对其电性能进行了仿真。仿真结果表明,提出的全极化环焦反射面天线的设计方案电性能参数合理,适用于在弹载环境下应用。     

Mechanism for assembling antenna in space

The development of large and precise space antennas is one of the most important topics in constructing space infrastructures. We evaluated an approach to assembling large and accurate space antennas which uses space robots. The assembly mechanism was launched together with the ETS-VII, the first telerobotic satellite from Japan, and its performance, including fully automatic assembling, was verified. The assembling-type antenna and the results of antenna assembly experiments are discussed     

Performance analysis of radar antenna systems

If modern airborne radar systems are to function properly, the radar antenna radiation patterns must meet certain specifications. Until recently, most radar antennas were designed and tested in a clean antenna environment, i.e., there is no near field scattering from host structures or radome effects. However, these higher order effects are the matter of increasing concern with added performance demands in the ever-increasing jammer and clutter interference environments. We investigated the capabilities and limitations of currently available analysis techniques and computer codes for installed performance of airborne radar antenna systems. Then we developed an extended ray-optical technique that could predict total installed performance of airborne radar antenna systems, i.e., the near field scattering from aircraft structures and radome effects. The new analysis technique utilized a ray-tracing method in both airframe and radome simulation. Thus, it can efficiently predict the total installed performance of large radar antenna systems on an aircraft structure     

Reflector antenna analysis by simple photography

The performance of a conventional microwave parabolic dish reflector can be estimated from a 35 mm photo, which is taken when the dish is illuminated by a small light bulb mounted at its feed point. Both random surface errors, structural deformations and feed positioning problems can be analyzed. If only go/no go-information is needed, no optical interferometry is necessary     

Compact wideband FSS-absorber-based low-RCS reflectarray antenna

This paper presents a method to realize compact broadband low-RCS Reflect Array(RA) antenna based on a Frequency Selective Surface(FSS) absorber and a reflective metasurface.Such an FSS absorber consists of a resistance-loaded lossy layer and an FSS layer, which is utilized to reach an absorption-transmission response. The bottom reflective metasurface works as a phase array, reshaping the quasi-sphere wave from the feeding antenna into the quasi-plane wave. As a demonstration, the low-RCS RA an...     

Small Ku-band phased array antenna system

A four-element phased array antenna prototype with varactor tuning has been constructed. The design employs aperture-fed quarter-wave patch elements and loaded-line phase shifters, having a phase adjustment range of about 50/spl deg/, which enables beam steering up to 13/spl deg/ from the array boresight. The system is suitable as a building block for larger arrays and shows as such a maximum gain of 7.7 dBi and an impedance bandwidth of 1 GHz. The sidelobe level is better than -13 dB. Problems encountered include parasitic resonances which disturb matching, and partially deteriorate the radiation pattern. Additionally, mechanical manufacturing tolerances of the microstrip boards were not always adequate, whereby a 6% shift in the center frequency, some impedance errors, and phasing inaccuracies were observed.