Array Radar Antenna Research Articles

Miniaturized Hybrid Rat-Race Coupler of a 2.5 GHz Loaded by Resistors

A rat-race coupler is one of the essential components used in microwave circuits. Rat-race coupler has numerous applications in satellite communication, phased array radar antenna systems and radar. Recently, wireless communication systems usually require smaller device size, in order to meet circuit miniaturization. Thus, size reduction becoming major design considerations for practical applications. This paper includes design the proposed microstrip rat-race coupler for frequency 2.5 GHz. The area of the proposed rat-race coupler compared with the conventional structure, the proposed rat-race coupler in this paper has smaller size than the conventional structure. The main outcome of this work is reducing the area of the proposed coupler by 10%. Microwave Office (MWO-225-SUF) tool is used to execute the design of the coupler in this work.

Study on UWB Through-wall Radar Antenna Array Configuration and Moving Person Tracking and Imaging Algorithm

Study on UWB Through-wall Radar Antenna Array Configuration and Moving Person Tracking and Imaging Algorithm

Secondary Surveillance Radar Antenna [Antenna Designer's Notebook

This paper deals with a secondary surveillance radar (SSR) array antenna, which is intended for a system combining the secondary surveillance radar antenna and the primary surveillance radar antenna. It describes the patch array elements and the synthesis for the secondary surveillance radar array, considering both elevation and azimuth patterns for sum, difference, and sidelobe-suppression beams, and suspended stripline couplers. The utilization of multilayer techniques allows the connection of layers with patch radiating elements and layers with beamforming networks.

Impact of Low-Frequency Radar Interference on Digital Terrestrial Television

This paper considers low-frequency radar cohabitation with digital video broadcasting terrestrial (DVB-T). The spatial and temporal radio frequency propagation characteristics of the terrestrial and air-to-ground channels are modeled using state-of-the-art 3-D ray tracing for real-world broadcast television scenarios. Rooftop DVB-T receivers are assumed at user locations in two different urban environments, namely, the cities of London and Bristol, U.K.. The propagation characteristics are combined with appropriately orientated 3-D antenna radiation patterns, which include full polarization information for the DVB-T rooftop antennas, the base-station antennas, and the airborne radar antennas. A radar waveform generator is used to synthesize a representative range of radar signals. A DVB-T physical layer simulator has been developed to predict the performance of the received broadcast stream at each rooftop location. Factors, such as additive noise, the power and structure of the wanted DVB-T and the interfering radar signals, and the nature of the radio channels, are shown to influence the DVB-T bit error rate results. Statistics for the probability of high-quality DVB-T reception are reported as a function of the modulation scheme, propagation environment, aircraft orientation, radar antenna array configuration, and radar waveform type.

ZACUBE‐1 Space Weather Mission: Characterize the SuperDARN HF Radar Antenna Array at SANAE‐IV

Key Points SuperDarn characterization CubeSat mission

Antenna Array for Passive Radar: Configuration Design and Adaptive Approaches to Disturbance Cancellation

We consider the selection of an antenna array configuration, composed of a small number of omnidirectional elements, to be exploited for passive radar sensors. Based on properly identified pattern characteristics and design criteria for practical applications, a suitable planar configuration is selected that allows both angular selectivity and direct signal attenuation. The selected configuration is further optimized in terms of sidelobe level by resorting to appropriate amplitude tapering. Moreover, three different approaches are investigated for antenna-based adaptive disturbance cancellation, and a comparative performance analysis is carried out. Simulation results show that an effective clutter suppression is obtained if the direct signal from the transmitter is attenuated by means of spatial adaptive cancellation, and the multipath echoes from stationary obstacles are removed by means of temporal adaptive cancellation. In particular, the approach based on the Sidelobe Canceller is shown to yield good performance while requiring a limited system complexity.

Integrated Design of a Compact and Lightweight S-Band Traveling-Wave Tube Amplifier for a New Class of Microwave Power Module

A new class of compact and lightweight S-band 1 kW traveling-wave tube (TWT) is being developed for a microwave power module (MPM) that will be used for phased antenna array radar applications. The proposed S-band MPM provides a tenfold peak power increase compared to state-of-the-art S-band MPMs. In this paper, the design of the vacuum power booster TWT part of the MPM is presented. The compact and lightweight S-band TWT is driven by a 6 kV, 0.9 A electron beam. The amplifier is predicted by large-signal simulations to generate over 1 kW at S-band with 25 dB saturated gain and over 40% efficiency. The stability from unwanted oscillations has been investigated. To suppress the oscillations, the helix circuit has been coated with carbon composite material. The coaxial input and output antennas have been fabricated. For efficiency enhancement, a multi-stage depressed collector (MDC) has been designed using a 3D particle-in-cell (PIC) simulator, VORPAL. The collector design makes use of a current loop based on a feedback mechanism for effective design process. The integrated designs of a helix circuit, an electron gun, a periodic permanent magnet (PPM), antennas, and a collector are presented.

Signal-to-Noise Ratio Equalization for TOPSAR Mode Using a Nonuniform Steering Rate

In this letter, an optimized scanning in terrain observation by progressive scan synthetic aperture radar (TOPSAR) mode is studied. A nonuniform steering rate of the radar array antenna in the along-track direction is proposed in order to obtain constant radiometric sensitivity and signal-to-noise ratio. This is achieved owing to the longer integration time of the echoes received at both ends of the antenna azimuth sweep. By optimizing iteratively the array discrete steering rate law, the radiometric impact of the array basic element pattern (subarray pattern) can be accurately compensated. First, simulation results are presented to validate the nonuniform steering TOPSAR.

Dual-Polarized Printed S-Band Radar Array Antenna for Spacecraft Applications

A novel dual-polarized broadband antenna array for S-band is presented. This antenna is composed of 6 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\,\times\,$</tex> </formula> 2 microstrip antenna elements with a hybrid feed-line network providing an isolation <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\geq$</tex> </formula> 18.6 dB between the H- and V-ports. The operative bandwidth is from 3.15 to 3.25 GHz, and the peak measured gain is approximately 19 dBi. The array is suitable for spacecraft operation because of the selected materials, its low profile ( <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\sim$</tex> </formula> 8 mm thickness), and light weight. It has potential applications in synthetic aperture radar (SAR), remote sensing, and wireless communications.

The Radiation Properties of a Novel Wire Antenna for the Security Fence Radar

The radiation properties of a novel wire antenna are investigated. The main part of this antenna is a sinusoidal wire undulator, which radiates by coupling electromagnetic energy from a Goubau line located near the antenna. Far-field patterns and S-parameters composed of three sets of antenna are measured. The measured patterns are compared with the calculated ones and the phase and attenuation constants of all the antennas are calculated. Frequency behavior and the dependency on the antenna dimensions of those wave parameters are investigated. Measured and calculated field patterns are also compared with the MoM patterns and some properties of the wave propagating along structure are explained by using MoM current distributions. It is shown that a broadside transversal radiation occurs in a narrow frequency band. The radiation intensity strongly depends on the coupling distance between the Goubau line and the sinusoidal undulator. This antenna is used as the basic element of the security fence radar antenna array working at 1.25 GHz in the L-band, which detects intruders approaching the fence. The performance of the antenna in the array is investigated and the near field distribution of the array is measured. The received signals caused by an intruder are given. The effects of rain and wind are also considered. The results suggests that the security fence radar introduced in this study can be used for the perimeter control of closed areas such as airports, malls, etc.

Ant colony optimisation for tree-searching-based synthesis of monopulse array antenna

The design of simple feed networks is of great interest in synthesising monopulse radar array antennas in order to reduce the complexity of the antenna architecture, the costs as well as the occupied physical space (e.g. on aircraft). Sub-arraying techniques have been proposed to properly address such a task. Starting from the formulation of the sub-arraying problem in terms of a combinatorial one, the final compromise solution is obtained by looking for the minimum cost path inside a binary tree graph through an ant colony optimiser.

Testing of Inflatable-Structure Shape Control Using Genetic Algorithms and Neural Networks

I NFLATABLE structures have attractedmuch interest in the space community due to their unique advantages in achieving lowmass and high packaging efficiency [1,2]. We are currently working on an in-house research and development project of a membrane synthetic aperture radar antenna and solar array (see Fig. 1). It is expected that the membrane will be subjected to flatness problems during its lifetime in orbit, due to the thermal variation in space. A purely passive control method may not be sufficient to keep the membrane flat. Hence, an active control system is proposed to adjust the tensions according to the thermal variation. Actuators are installed in series with the links, such that the tensions stretching the membrane can be adjusted. A genetic algorithm and neural network (GA–NN) scheme is proposed for modeling and tension optimization. The neural network model of the membrane is established as a mapping from the boundary stretching tensions and space environment to membrane flatness. After the neural network training is completed, the membrane flatness can be estimated by inputting the measured stretching tensions and space environment data to the neural network model. Based on the neural network model, the genetic algorithm is applied to search for the optimal tensions that minimize the membrane wrinkles [3]. Experimental results demonstrate the effectiveness of the proposed scheme.

A Broadband Slotted Ridge Waveguide Antenna Array

A longitudinally-slotted ridge waveguide antenna array with a compact transverse dimension is presented. To broaden the bandwidth of the array, it is separated into two subarrays fed by a novel compact convex waveguide divider. A 16-element uniform linear array at X-band was fabricated and measured to verify the validity of the design. The measured bandwidth of S11les-15 dB is 14.9% and the measured cross- polarization level is less than -36 dB over the entire bandwidth. This array can be combined with the edge-slotted waveguide array to build a two-dimensional dual-polarization antenna array for the synthetic aperture radar (SAR) application

PARAMETRIC STUDY OF FLAT SANDWICH MULTILAYER RADOME

This paper presents parametric analysis of Flat Sandwich Multilayer Radome using Boundary Value Solution technique. The effect of variations in the characteristics of constituent layers of Radome on its microwave transmission properties has been studied. This work has relevance in development of Planar Array Radar Antennas especially for airborne platforms.

Direct infrared measurements of phased array aperture excitations

A thermographic imaging technique has been developed to measure electromagnetic (EM) fields. This technique is applied in this paper to measure the aperture plane fields of large phased array radar antennas and to determine the aperture (source) excitations of the array, i.e., the distribution of the radiated energy over the elements in the aperture plane of the array. These IR measurements, therefore, can be performed on-site at the remote location of the antenna in-the-field to produce a non-distorted image of the field excitations in the aperture plane of the array, which control the overall radiation characteristics of the array. In general, these images can be used for field diagnostics to evaluate the electrical characteristics of the elements of the array, i.e., the state (strength) of the aperture excitations and the condition of the switching circuits (phase shifters and attenuators), which control the radiation pattern of the antenna. The aperture field distribution can be compared to a standard “test pattern” to quickly determine the operational state of each individual element of the array. Individual attenuators and/or phase shifters that produce incorrect element intensities can be easily and quickly identified with this technique. Short-circuited elements at various positions in the array are used to simulate faults in the elements and to test the feasibility of the thermal technique to determine the operational state of the array. Therefore, the overall “state of health” of the array and the need for repair can be determined in-the-field using the IR measurement technique to avoid the expensive and time consuming alternative of dismantling the array and shipping it to a maintenance depot for testing, calibration, and repair on a standard, planar, near-field antenna test range. In this paper, the IR technique is tested in a controlled environment to determine the feasibility of using the IR images as an array diagnostic tool to measure the aperture excitations of large phased array radar antennas.

Direct infrared measurements of phased array near-field and far-field antenna patterns

A thermal imaging technique has been developed to measure electromagnetic (EM) fields. This technique is applied in this paper to measure the EM fields radiated by large phased array radar antennas and to determine the near-field distributions and the far-field antenna pattern. This thermal technique is based on infrared (IR) measurements of the heating patterns produced in a thin, lossy detector screen made from a carbon loaded polyimide film placed in the plane over which the field is to be measured. The temperature rise in the screen material is related to the intensity of the field incident on the screen. An experimental calibration table was developed at NIST/Boulder to convert the temperature rise at any point on the screen into an equivalent incident radiated field strength. This thermal imaging technique has the advantages of accuracy, simplicity, speed, and portability over existing hard-wired probe methods and produces a 2D picture of the near field or the far field. These IR measurements, therefore, can be performed on-site at the remote location of the antenna in-the-field to produce an image of the radiating field of the array, which can be used to determine the overall radiation characteristics of the array, i.e., the radiation pattern of the combined array elements (gain and beam-width) and the condition of the electronic switching circuits (phase shifters and attenuators). Therefore, the overall “state of health” of the array and the need for repair can be determined in-the-field using the IR technique to avoid the expensive and time consuming alternative of dismantling the array and shipping it to a maintenance depot for testing, calibration, and repair on a standard, planar, near-field antenna test range. In this paper, the IR technique is tested in a controlled environment to determine the feasibility of using the IR images as an array diagnostic tool i) to measure the radiated field of large phased array radar antennas (near-field or far-field patterns in a transverse plane parallel to the plane of the array), ii) to measure the transition of the field from the near field to the far field (in an axial plane perpendicular to the plane of the array), and iii) to test the switching of the array from a scan mode to a target tracking mode.

Denial of bistatic hosting by spatial–temporal waveform design

A set of theoretical techniques to prevent a radar from being used by a bistatic radar receiver as a non-cooperative illuminator are analysed. This works by radiating in addition to the radar signal waveform, a ‘masking signal’ waveform which is orthogonal to the radar signal waveform, both in the coding domain and the spatial domain. A number of different coding schemes are analysed. Two spatial coding methods are presented and analysed: the first uses a pair of interferometer elements at the extremities of the radar antenna array; the second uses a Butler matrix to generate a set of orthogonal beams. System-level calculations are presented to show the level of masking of the radar signal received by a bistatic radar receiver, and the suppression of the masking signal in the host radar echo. Some ideas for further work are presented.

System Modeling and Signal Processing for a Switch Antenna Array Radar

A system composed of a single transmitter, M receiving antennas, and a single receiving channel is studied. Echo radar signals are acquired in a number of the cycles and used for estimation of the angle, velocity, and range in a multiple moving target scenario. The receiving antennas are switched to the single receiving channel periodically once every cycle. The developed algorithms are based on minimum variance (Capon) beamforming. A new nonstationary version of Capon beamforming is developed for the time-varying steering vector model. It is shown in simulations done for an automotive scenario that the proposed algorithms yield very good performance in terms of both estimation accuracy and multiple-target resolution. The Capon-based estimation gives results close to the corresponding Crame/spl acute/r-Rao lower bounds (CRLBs).

Realization of true-time delay lines based on acoustooptics

A true-time optical delay line for short radiofrequency (RF) pulses using path length dispersion is proposed. It is an optical implementation of the linear phase-shift theorem of the Fourier transformation. Acoustooptic signal processing is used for conversion into the optical frequency domain and for spatial Fourier decomposition of the pulse. The processing of the pulse is obtained by differentially phase shifting the particular frequency components, followed by a heterodyne reconversion into the RF domain. The optical system is intended to be used for delaying, but also for shaping and filtering of RF pulses, mainly in phased array radar antennas. Theoretical analysis of the system principle is given together with experimental results, demonstrating 2-/spl mu/s time delay of 0.5-/spl mu/s-long pulses with maximum optical phase shift of 1.2/spl pi/. A detailed theoretical and experimental bandwidth analysis is carried out, pointing to the main technical problems and their solutions.

Infrared Imaging of Phased Array Radar Antenna Emissions

The subject paper discussed the merits of applying infrared imaging technologies, in association with advanced digital processing techniques, as a system health diagnostic tool to (1) enhance readiness and (2) reduce the cost of ownership associated with phased array radar systems that are used throughout the military services. The planned project shall establish a field-level diagnostic tool that can rapidly assess deployed phased array radar antenna performance, using infrared (IR) imaging techniques and that can isolate deficient radio frequency (RF) solid state emission devices (radiator elements). Infrared imaging of RF emissions from an aircraft-installed phased array radar system (APG-63 used in F-15 aircraft) has been conceptually demonstrated; however, full scale-up was never achieved nor other potential technology applications evaluated because of funding constraints. Today, solid state phased array technology is used pervasively in air and in ground/surface-based radar systems. Table 1 identifies representative ground/surface-based radar systems that incorporate phased array antennas in their system architecture. The ability to conduct operational “end-to-end” testing of phased array antennas will enable deployed verification of detected performance degradations, facilitate field-level replacement of faulty RF emission devices, and help reduce the overall logistics burden associated with dismantling and transporting bulky radar systems for return to depot In addition, the proposed capability could be used as a preliminary diagnostic tool, augmenting existing depot capabilities, to help facilitate the accelerated identification/confirmation of required depot-maintenance actions. IR imaging has the potential to catalyze a fundamental shift, comparable to the introduction of automated testing in support of avionics, in the basic approach to phased array antenna maintenance.