Radar Antenna System Research Articles

Design and Simulation Analysis of Antenna Structure for Active Phased Array Radar

Abstract This article adopts a modular design concept to design an active phased array radar antenna system structure and elaborates on its structural layout design and thermal design content. A finite element model of the antenna structure framework was established, and the rationality of its structural and thermal design was verified through static and thermal simulation analysis.

An Improved OMP Algorithm for Enhancing the Anti-Interference Performance of Array Antennas.

The demand for precise positioning in noisy environments has propelled the development of research on array antenna radar systems. Although the orthogonal matching pursuit (OMP) algorithm demonstrates superior performance in signal reconstruction, its application efficacy in noisy settings faces challenges. Consequently, this paper introduces an innovative OMP algorithm, DTM_OMP_ICA (a dual-threshold mask OMP algorithm based on independent component analysis), which optimizes the OMP signal reconstruction framework by utilizing two different observation bases in conjunction with independent component analysis (ICA). By implementing a mean mask strategy, it effectively denoises signals received by array antennas in noisy environments. Simulation results reveal that compared to traditional OMP algorithms, the DTM_OMP_ICA algorithm shows significant advantages in noise suppression capability and algorithm stability. Under optimal conditions, this algorithm achieves a noise suppression rate of up to 96.8%, with its stability also reaching as high as 99%. Furthermore, DTM_OMP_ICA surpasses traditional denoising algorithms in practical denoising applications, proving its effectiveness in reconstructing array antenna signals in noisy settings. This presents an efficient method for accurately reconstructing array antenna signals against a noisy backdrop.

Design of multiple‐input multiple‐output radar amplitude‐bounded waveforms with desired ambiguity function based on sequential quadratic programming

AbstractThe transmit waveform with ambiguity function specifications in the range‐Doppler plane has been of great interest in traditional single antenna radar systems in recent years. This paper considers the design of waveform sets with a desired slow‐time ambiguity function for multiple‐input multiple‐output radar. Specifically, it is desirable that the ambiguity function has low sidelobes where clutter occurs, as this reduces the impact of the clutter on target detection. Instead of unimodular waveforms, the authors consider amplitude modulation signals and introduce the bound constraint on signal amplitudes into the optimisation for the consideration of transmitter efficiency. The design problem is formulated as minimising the weighted integrated sidelobes level of the ambiguity function over the range‐Doppler plane under bound constraints. The resulting problem has a highly non‐linear objective function and is constrained by bound constraints and quadratic equality (constant energy) constraints, making it difficult to solve. The authors develop an efficient algorithm based on the sequential quadratic programming technique and non‐linear conjugate gradient method to solve it. Simulation results show that the proposed algorithm is superior to the existing methods.

Metasurfaces and Blinking Jamming: Convergent Study, Comparative Analysis, and Challenges.

Blinking jamming is an active self-screening technique performed by at least two aircraft to tackle monopulse radars and all complexity related thereto. Nowadays, the technique can be performed with digital radiofrequency memories (DRFMs), which are cumbersome, complex, expensive, need a dedicated compartment and antenna, and introduce spurs in the signals. In this paper, we propose an alternative to the implementation of blinking jamming with DRFMs, namely with reconfigurable metasurfaces. By covering the aircraft parts that most contribute to the radar cross-section (RCS), reconfigurable metasurfaces can interchangeably absorb or amplify impinging waves, making the aircraft 'blink' from the radar perspective. To validate the feasibility, simulations accounting for realistic phenomena are conducted. It is seen that, if the aircraft RCS can be varied in a ratio of 10:1, either with absorptive or power-amplifying metasurfaces, a performance similar to that of the DRFM is achieved. Furthermore, a ratio of 2:1 is sufficient to make the radar antenna system movements exceed the angular range of the formation. We also anticipate our work to be a starting point for completely new ways of countering radars, e.g., with countless small drones performing passive or active stand-off blinking jamming.

Leaky-Vivaldi antenna covered with metasurface with leaky wave radiation and aperture radiation.

A leaky-Vivaldi antenna covered with metasurface (LVAM) is proposed in this paper. The traditional Vivaldi antenna covered with metasurface realizes backward frequency beam-scanning from -41∘ to 0∘ in the high-frequency operating band (HFOB) and retains aperture radiation in the low-frequency operating band (LFOB). In the LFOB, the metasurface can be regarded as a transmission line to realize a slow-wave transmission. In the HFOB, the metasurface can be considered a 2D periodic leaky-wave structure to realize a fast-wave transmission. The simulated results show that LVAM has the -10 dB return loss bandwidths of 46.5% and 40.0%, and the realized gain of 8.8-9.6 dBi and 11.8-15.2 dBi cover the 5 G Sub-6 GHz band (3.3-5.3 GHz) and the X band (8.0-12.0 GHz), respectively. The test results are in good agreement with the simulated results. As a dual-band antenna covering the 5 G Sub-6 GHz communication band and military radar band, the proposed antenna can guide the future integrated design of communication and radar antenna systems.

Practical approach of measuring of angular bearing errors for radiotransparent radomes with complex shape in the “antenna – radome” system in the entire possible scanning ar-ea of the airborne radar antenna system

A nose radiotransparent radome (RTR) plays the role of a dielectric lens of a complex shape, which can significantly affect the radiation characteristics of the airborne radar antenna of an aircraft located under it. Modern radars, as a rule, are built on the basis of antenna systems with electronic beam control – phased antenna arrays. The phasing of the array is carried out in the most different (available for a given phased array) spatial directions. One of the parameters that define the operation of the radar under the RTR is the error in determining the angular position of the targets found by the radar. With complex forms (with one plane of symmetry) of the nose RTR, the resulting angular bearing errors (ABE) depend significantly on the spatial position in which the radar antenna is currently phased. In some cases, bearing errors must be taken into account when operating the radar. This becomes especially important in direction finding and tracking of targets remote to the limit for radar aircraft. In this case, the data on the values of the ABE depending on the current coordinates of the array phasing become relevant. The aim of the article is to present a simple technique that makes it possible to practically measure the ABE in the system “antenna – RTR” in a significant area of electronic scanning by the antenna beam. The technique for measuring the ABE has been developed, which was tested on the basis of an antenna-measuring collimator complex (“compact test site”). Mathematical expressions have been given for calculating both components of ABE (in the phased antenna array angular coordinate system) based on the measured data. At the initial stage, the technique has been tested on the basis of a specially made quick-detachable model-simulator of the radome, which has the ability to introduce arbitrary ABE. With the help of this model, a comparison of the results of measurements obtained on the basis of the proposed method and the method associated with the measurement of dynamic spatial radiation patterns (RP) has been performed. A good correlation of data has been noted for different methods, but on one physical model-simulator of the RTR, which allows us to speak about the correctness of the chosen approach. Subsequently, the correctness of the proposed method has been confirmed by the data collected when working with the system “phased antenna array – RTR” (teardrop shape). In this case, the calculated components of the ABE have been compared with the results of direct measurements by the difference method, when each of the orthogonal components is calculated by measuring the angle of displacement of the minimum of the corresponding difference pattern, obtained before and after the installation of the RTR. The developed technique of preliminary measurement of angular bearing errors over a significant part of the surface of a real RTR makes it possible, if necessary, to compensate the measured ABE in aircraft radar computers, thereby increasing the accuracy of determining the spatial coordinates of targets in space.

Practical Noise Model of an Active Electronically Scanning Array

Active electronically scanning arrays are now widely used in radar and communication systems. The noise characteristics are critical to the system signal-to-noise ratio, thus modeling of the antenna array noise is useful. In this paper, a two-port noise model of an active electronically scanning array is presented, which is more practical than the model in previous publications. In this model, an antenna array with a multistage combiner network is equivalent to a one-stage combiner network, thus the calculation of the noise figure is greatly simplified. Since the model is based on measurable parameters, it can be applied directly to the design of electronically scanning arrays. The noise model of a spaceborne synthetic aperture radar antenna system is displayed for example. Some useful conclusions are got about the noise figure for tapered antenna arrays. For a weighted antenna array with taper efficiency εT, if the gain of low noise amplifiers is sufficiently large, the noise figure of the antenna array is increased by 1/εT, compared to a uniformly weighted array. Besides, the deterioration of the signal-to-noise ratio for a tapered antenna array system originates from the increase of antenna noise temperature, rather than the decrease of antenna aperture gain.

Gapwaveguide Automotive Imaging Radar Antenna With Launcher in Package Technology

A 77 GHz gapwaveguide radar antenna system with launcher-in-package (LiP) technology is presented in this paper for automotive imaging applications. Firstly, state-of-the-art LiP technology integrated with radar transceivers is proposed. The transceivers are equipped with waveguide interfaces for RF connection, enabling direct integration with waveguide antennas. Robust interconnects for coupling transceivers to waveguide antennas with non-galvanic contacts are proposed using gapwaveguide packaging technology. A simultaneous multi-mode imaging radar system using 4 cascaded aforementioned transceivers is introduced. Designated antenna elements of the system are realized by slot arrays with center-fed ridge gapwaveguides. Ultimately, the imaging radar antenna has a top radiating slot layer, a middle distribution layer and a bottom interconnect layer capable of accommodating 4 LiP radar transceivers with considerable assembly tolerance which is really one of the key aspects for commercial automotive radar applications. Input matching and radiation patterns of the antenna are verified by measurement. The results indicate that the proposed gapwaveguide imaging radar antenna in conjunction with the novel LiP packaging is able to serve the radar system properly. To the best of the authors’ knowledge, the proposed gapwaveguide antenna system is the first imaging radar antenna system ever developed for LiP components. This work provides a compact, high-efficiency and cost-effective solution for the integration of complex radar systems with waveguide antennas.

An Improved 3D Ultra-Wideband High-Efficiency Substrate Integrated Coaxial Meander Delay Line

This paper proposes an improved substrate integrated coaxial meander delay line to overcome the beam dispersion problem in a spaceborne synthetic aperture radar phased array antenna system with large bandwidth. The delay line operates in the range of 4 GHz–10 GHz with a relative bandwidth of 85.7%. In the proposed structure, the delay effect is generated by the combination of a meander delay line and a substrate integrated coaxial line, which results in a significant improvement in the delay efficiency. Furthermore, a planar turn structure, a vertical transition structure, and a microstrip transition structure are designed to realize three-dimensional tight wiring. The proposed delay lines are fabricated on three and five layered Rogers RO3006 PCB substrate. The experimental tests are conducted on the 3.1 ns and 6.4 ns delay lines with the dimensions of 38 mm × 7 mm × 0.5 mm and 37 mm × 9.2 mm × 1 mm, respectively. The experimental results indicate that the insertion and return losses of the two lines are within the reasonable range. Compared with the related research, the proposed delay lines’ delay time, delay multiplier, and relative bandwidth are improved by 2.13–160 times, 1.025–6.8 times, and 2.14–3.86 times, respectively, which shows their good practical value and application prospect.

Methodology for the Development of Radar Control Systems for Flying Targets with an Artificially Reduced RCS

The article explores methods for detecting and tracking air targets in radar with an artificially reduced radar cross-section (RCS). A technique for control the radar antenna system using an adaptive method is presented, which is based on adapting the system to the conditions of information uncertainty due to fluctuations in the excitation signal of the radar target's radar-absorbing coating. Known methods of radar aircraft (active and passive, which do not take into account the structure of the coating of the aircraft) do not allow obtaining information about an air target with an artificially reduced RCS. The main contribution of this article is the development of radar and control methods based on the resonant frequency-phase interaction of the microwave electromagnetic field with the crystal structure of the radar absorbing coating of the aircraft. The stages of antenna system control based on the "frequency-phase detection method", "passive-active" tracking method, and "adaptive method" of antenna control have been studied. To test the proposed methods, an experiment was conducted to determine the transient process in the control system under conditions of information uncertainty. As a result of the experiment, the probability of tracking the target is increased by 14-19%. The findings will be useful for developers of radar and control systems for modern air facilities with an artificially reduced RCS.

Spatial resolution enhancement of rotational-radar subsurface datasets using combined processing method

Effective visualisation of railway tunnel subsurface features (e.g. voids, utilities) provides critical insight into structural health and underpins planning of essential targeted predictive maintenance. Subsurface visualisation here utilises a rotating ground penetrating radar antenna system for 360° point cloud data capture. This technology has been constructed by our industry partner Railview Ltd, and requires the development of complimentary signal processing algorithms to improve feature localisation. The main novelty of this work is extension of Shrestha and Arai’s Combined Processing Method (CPM) to 360° Ground Penetrating Radar (360GPR) datasets, for first-time application in the context of railway tunnel structural health inspection. Initial experimental acquisition of a sample rotational transect for CPM enhancement is achieved by scanning a test section of tunnel sidewall - featuring predefined target geometry - with the rotating antenna. Next, frequency data separately undergo Inverse Fast Fourier Transform (IFFT) and Multiple Signal Classification (MUSIC) processing to recover temporal responses. Numerical implementation steps are explicitly provided for both MUSIC and two associated spatial smoothing algorithms, addressing an identified information deficit in the field. Described IFFT amplitude is combined with high spatial resolution of MUSIC via the CPM relation. Finally, temporal responses are compared qualitatively and quantitatively, evidencing the significant enhancement capabilities of CPM.

Development and optimization of microwave guide polarizers using equivalent network method

In this article, we have developed a new mathematical model of a microwave square guide polarization converter with diaphragms. The applied model was created using the microwave theory of equivalent networks. The novelty of the developed theoretical model consists in its possibility to take into account the thickness of the diaphragms. This feature is achieved by using more accurate but complicated T- and Π-shaped equivalent networks. Theoretical analysis and optimization of a guide polarizer were performed using the scattering and transmission matrices of the diaphragms in a square guide. The parametric optimization of a guide polarizer was performed by means of the developed equivalent networks and using finite elements method in the frequency domain. The optimal sizes and electromagnetic characteristics of the polarizer, which were obtained by both methods, are in good agreement. The main advantage of the suggested mathematical model consists in the calculation time reduction. Developed compact waveguide polarizer can be used in modern satellite and radar antenna systems with circular polarization of applied electromagnetic waves.

Sub-Millimeter-Wave Polarization-Independent Spatial Power Divider for a Two-Port Dual-Polarized Antenna

An antenna system is proposed that uses a novel polarization-independent spatial power divider to align the beams from two orthogonally oriented dual-polarized feeds. This antenna system uses a common aperture for transmitting and receiving and provides high port isolation while maintaining compatibility with fully polarimetric radar. Unlike conventional two antenna radar systems, a radar using this antenna does not suffer from the parallax problem. The spatial power divider is designed using an all-dielectric metasurface approach and is fabricated on a silicon wafer using standard micromachining technology. The measured device exhibits at most 0.9 dB of difference between the reflection and transmission for both transverse electric and transverse magnetic incident waves at 45° incidence, over a band from 221 to 250 GHz. Conical horns are fabricated as feeds and together with the spatial power divider, a focusing lens, and microwave absorbers, are assembled in a three-dimensional-printed housing to complete the antenna system. Its measured gain is approximately 39 dB for each port and polarization, and isolation between ports is at least 40 dB for all polarization combinations over the band of interest.

A DESIGN SOLUTION FOR COMPACT SLOTTED WAVEGUIDE ARRAY ANTENNAS BASED ON SIW TECHNOLOGY

Slotted waveguide array antenna is a crucial structure in microwave frequency antennas with many applications in radar and communications systems. Previously, slotted waveguide array antenna systems mainly used metal materials. The study of slotted array antenna based on the waveguided with SIW (Substrate Integrated Waveguide) technology is a novel approach. The paper presents the results of researching, designing, and manufacturing waveguide slot array antenna with low SLL using SIW technology in X-band. The results will be an essential basis for selecting a design solution for slotted waveguide array antenna by SIW technology to replace traditional metal slot array antennas in practical applications in X band radar antenna systems.

Hybrid Metamaterial for the Secondary Radar Antenna System

This paper proposes the gain enhancement of dual-band and dual-polarized asymmetric horn antenna for the secondary radar system using hybrid metamaterial techniques. The hybrid metamaterial is comprised of the structures of woodpile electromagnetic bandgap (EBG) for gain enhancement of the primary main beam of the radar system at the operating frequency of 1,300 MHz with horizontal polarization; and the wire medium structure that is placed beside the EBG structure for gain improvement of the identification friend or foe (IFF) main beam, which is operated at the center frequency of 1,060 MHz with vertical polarization. Meanwhile, the cooperated structures have to function to control the directions of the primary and IFF main beams retaining at 0° and 6°, respectively, too. When the hybrid metamaterial structure is placed at the front of an asymmetric horn’s aperture, with suitable parameters and optimized spacing, it is found to increase the gains of the two beams compared to the single asymmetric horn around 3 dB and retain the directions of original main beams. The comparison of the results between simulation and measurement, such as the reflected power (S<sub>11</sub>), gain, and radiation patterns, are in good agreement.

Radar Wave Based Positioning of Spatially Distributed MIMO Radar Antenna Systems for Near-Field Nondestructive Testing

Spatially distributed multiple-input multiple-output (MIMO) radar systems offer an advantage in locating and characterizing targets compared to individual MIMO radar. In such systems, precise antenna positioning is crucial for their imaging performance. This letter presents a method for antenna position estimation based on radar wave propagation between the antennas. The antenna positions are calculated based on a multilateration algorithm and further optimized by using Levenberg–Marquardt method and singular value decomposition. Ranging and positioning performances obtained with a 15-GHz stepped frequency MIMO radar are described and evaluated. Finally, measurement results from a test object illustrate the performance of the proposed method for near-field nondestructive targets testing.

Radar with increased angular resolution of objects in wide-angle scanning

The parameters of radar antenna systems constructed according to the traditional scheme with phase shifters inserted both in the transmitting and receiving antenna array with the radar in which signal processing is performed only on the receiving side are considered and compared in the paper. In the second case, an additional requirement of orthogonality of the radiated signals is imposed on the radiating system of the transmitter. The characteristics of the radar with three transmitters and four receivers are compared. Two variants of forming a virtual antenna array are considered. In the first case, the radiation of the linear regular antenna array is analyzed, in the second case the thinned one, but with the same number of emitters. We demonstrate that in the second case, it is possible to implement the radar with a better angular resolution. The features of using the radar as a short-range radar for vehicle security systems with a wide-angle view are elaborated. The possibility of false capture of the target is noted. The authors of the research suggest the unambiguous direction finding method.

Antenna system of ultrawideband borehole radar based on loaded electric dipoles

The design of an ultrawideband borehole radar antenna system based on loaded electric dipoles is presented. The antennas are designed to operate in a dielectric medium in the frequency range of 0.25–1 GHz. The results of calculations and measurements of antenna characteristics are presented. The results of sounding the objects when placing antennas in a medium with a relative permittivity of 4 are presented as well.

THE METHOD OF CALCULATION OF COEFFICIENTS OF THE PHASE ABERRATIONS OF AXIALLY ASYMMETRIC DUAL REFLECTOR ANTENNAS

Aerodrome-enroute surveillance radar systems (ARSR) of civil aviation are designed for detection of aerial objects and determination of their range and movement parameters. Meanwhile, the reflector-type antennas are still the main type of_used antenna systems. Radars (ARSR) have, as a rule, antennas with a bidirectional beam, structurally reflector-type antenna is made in the form of a truss welded structure. The use of active phased antenna arrays (APAR) is a promising direction of radars (ARSR) development. Radars (ARSR) based on the phased antenna arrays can significantly improve such critical tactical and technical criteria as: the accuracy of the coordinates determination, the number of simultaneously followed targets. However, the use of APAR does not solve one of the main problems - the presence of a support-rotary device in the radar (ARSR). The principal necessity of a support-rotary device leads to the need of the use of movable joints of feeder lines, which, with a significant number of antenna elements used in the PAR, significantly reduces the potential time before failure. It seems promising to use in the radar antenna systems based on several stationary multi-beam dual-reflector antennas made by axially asymmetric scheme. Methodology of estimation of aberrations of a dual-reflector sensimetrics antenna based on a polynomial expansion of the eikonal function in the plane of the aperture of the main reflector is proposed in the article. Analytical expressions of the functions of display and rotation of the scanning plane of a dual-reflector axially asymmetric antenna with arbitrary parameters, designed based on clippings from centrally symmetric surfaces of rotation of the second order, are obtained. It is shown that the aplanatic antennas lose their scanning features during the transition to the axially asymmetric variant.

First Joint Observations of Radio Aurora by the VHF and HF Radars of the ISTP SB RAS

Two modern radars for diagnosis of the ionosphere by the radio-wave backscattering method, namely, the Irkutsk incoherent scatter radar at VHF (IISR, 154–162 MHz) and the Ekaterinburg coherent radar at HF (EKB, 8–20 MHz) are operated at the Institute of Solar-Terrestrial Physics, Siberian Branch of the Russian Academy of Sciences (ISTP SB RAS). The paper analyzes the results of joint observations of strong scattering (radio aurora) on June 8, 2015. To determine the geographical position of the radio aurora, we developed original methods that take into account both the features of the radio-wave propagation and the features of the radar antenna systems. It is shown that there are areas where the spatial position of the HF and VHF radio aurora can coincide. This permits using the radars as a single complex for diagnosis of the characteristics of small-scale high-latitude irregularities in the ionospheric E and F layers. A comparative analysis of the characteristics and temporal dynamics of the radio-aurora region in the HF and VHF ranges is performed. Using the DMSP satellite data, it has been shown that the radio aurora dynamics during this experiment with the EKB radar can be related with the spatial dynamics of the localized area with high electric field, which moves from high to equatorial latitudes. It is found that due to the broader field of view, radio aurora at the HF radar was stably observed 6–12 min earlier than at the VHF radar. This permits using the EKB radar data for prediction of the radio-aurora detection by the IISR radar.