Monopulse Radar System Research Articles

A Wideband 1-bit Reconfigurable Electromagnetic Surface for Monopulse Radar Applications

We present a wideband 1-bit reconfigurable electromagnetic surface (REMS) for monopulse radar applications at X-band. The proposed REMS element integrates a 1-bit reflection-type phase shifter controlled by a PIN diode. By altering the working states of the PIN diode, well-defined beam scanning is obtained. Furthermore, selecting different feeding states can realize the sum (Σ) and difference (Δ) patterns. The key design issues, including element modeling, coding design, and feed optimization, are studied to obtain good Σ and Δ beam performance. Experimental results show that REMS achieves a high gain of 23.3 dBi, a low sidelobe level of -15 dB, and a low null depth of -30 dB. The wide-angle monopulse beam-scanning up to ±60° is obtained. The gain bandwidth of -3 dB ranges from 9.35 to 11.75 GHz, with a relative bandwidth of 22.75%. Thus, the proposed multi-feed REMS brings new freedom for the Σ and Δ beam scanning, which provides wide application prospects for the monopulse radar system.

Closed‐form angle estimation of unresolved targets in monopulse radar to counter the angular electronic attack

AbstractTypical monopulse radar cannot detect the angle of two closely‐spaced targets in one resolution cell. The authors propose a closed‐form technique to estimate the angle of two unresolved targets by using a single snapshot of four radar receiver channels. In this work, phase comparison and amplitude comparison problems for monopulse radar are resolved. The monopulse radar angle estimation system has been enhanced using the diagonal difference channel. Using a single pulse, this technique can accurately determine the angle and amplitude of the deceptive decoy and the real target. If both targets have the same direction, the proposed scheme cannot detect them; therefore, to estimate the angle of such targets, we used an additional antenna. The effectiveness of the proposed method is validated by comparing the exact solutions and simulations.

Time modulation based unconventional phased antenna arrays for monopulse and multifunction radar systems

AbstractThe development of novel and innovative phased array designs toward affordable and performance‐oriented solutions has become the dire need of modern‐age wireless communication technologies. This paper proposed an unconventional method to design phased array antennas by eliminating the need of phase shifters. A cost‐effective alternative is presented by using “time‐modulation” based arrays capable of beam steering and electronic scanning. Controlling the high‐speed absorptive switches connected with each radiating elements in a periodic manner to generate the desired amplitude and phase tapering is the main purpose of these time‐domain arrays. So, the need for expensive phase shifters and erroneous attenuators can be avoided. This article explored the idea of “time‐modulation” to design innovative and efficient phased arrays for monopulse and multifunction radar systems. Suitable switching sequences are designed to produce simultaneous sum‐difference radiation patterns for monopulse tracking radars, and simultaneous scanned beam patterns for multifunction radars. To achieve the desired objectives, time‐modulated linear arrays of 10, 20, and 30 elements are proposed with appropriate switching sequences. The parameters of the arrays such as switch‐ON instants, switch‐ON periods, and switch‐OFF instants are controlled by employing the crow search optimization (CSO) algorithm. Representative results for both the applications are elaborated and compared with recently published counterpart designs to present the potentialities of the proposed concept for electronic steering and beam scanning applications.

MIMO Monopulse Radar for Detecting Human Targets With I/Q Curve-Length Estimations

This letter proposes a method to detect the angular locations of human targets using a multiple-input–multiple-output (MIMO) monopulse radar system. Sum and difference beams used for monopulse processing are simply implemented by digital beamforming of a virtual array generated by collocated MIMO radar. Human targets are readily distinguished from stationary clutter based on the phase variations in their signals, which are detected by estimating the curve lengths (CLs) of the I/Q trajectories. A monopulse processing technique integrated with the CL method is thus proposed. This system resolves two human targets, of which the angular separation is less than the angular resolution of the conventional radar. The system is verified through both simulations and experiments in an indoor environment.

Ku- 및 Ka-Band 기반의 대공 탐색 레이다 효과도 분석

To develop missiles to intercept short and medium-range rockets, the effectiveness of the air-to-air radar detector should be analyzed. In this study, to analyze the performance of a Ku- and Ka-band-based detector, we model the monopulse radar system, radar echo, and trajectories of the missile and rocket and perform numerical analysis for the radar cross section (RCS) of a computer aided design (CAD) model that is constructed based on an actual rocket. In addition, both the Swerling model and the analyzed RCS are considered in simulation to analyze the effect of the beam width of the monopulse radar and the power of received signals. As a result of the simulation, the Ka-band radar tracked the target relatively accurately in the presence of multiple targets, whereas the Ku-band radar had a higher probability of detection for low-RCS targets.

A Dual-Mode SIW Compact Monopulse Comparator for Sum and Difference Multibeam Radar Applications

In this letter, a compact wideband substrate integrated waveguide (SIW) monopulse comparator is proposed. The TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> and TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sub> modes of an SIW transmission line are used to generate in-phase and out-of-phase excitation fields for the sum and difference beams without complex phase shift network. The monopulse comparator can realize maximum 0.4-dB amplitude balance, 3.6° phase balance for both sum and difference ports, and −37.0-dB isolation coefficient within the operating bandwidth of 9.43–10.65 GHz. In addition, to integrate the monopulse comparator with a low-cost beam scanning capability, six monopulse comparators are used as the sources to excite a flat Luneburg lens. The experimental result demonstrates that ±58° beam coverage range with around −20.0-dB null depth and 15.0-dBi gain can be realized. The advantages of the proposed monopulse multibeam antenna, including low profile, low cost, wide beam scanning range, and wide operating bandwidth, make it a very promising solution for low-cost monopulse radar systems.

Novel 8-Port Network

The proposed 8-port network which consists of 4-coupler combined in unique way to produce 8-port network. This network with the proper terminations will find many applications in microwave and millimeter wave networks. This proposed 8-port network (with the proper termination) can be used as power combiner divider, six-port reflect meter in order to measure both the amplitude and the phase of the network under test. The proposed 8-port also can be used as phase comparator in a monopulse radar system for determining both the azimuth and the elevation of the target (K. Chang, et al, 1987). In addition, the circuit can be utilized as a 4-way power combiner/divider with the sub-arms isolated from one another. Generally, this 8-port network enjoys a compact structure which contains slots in sections the ground plane and between the coupled lines in order to improve the performance of this networks. Also this circuit can be utilized with proper termination as a network synthesize (G. Matthaei, et al, 1980). In the theoretical analysis of the proposed 8-port network, unique signal flow has been developed for this proposed. The purpose of the 8-port has been fabricated on Roger substrate of dielectric constant (ɛṛ = 3.38) and (thickness of the substrate is =0.2).

Sorotan Perkembangan Rekabentuk Antena Jalur Mikro Ekadenyut

A monopulse radar system functions to detect targeted objects by using Sum and Difference signals from the reflected signals. The use of parabolic type antennas in conventional radar systems has disadvantages in terms of space, mass, and manufacturing costs. Therefore, microstrip antennas have been proposed because they are flat, lightweight, and cheaper to fabricate. Multiple devices used to produce the important sum and difference signals i.e., hybrid junctions, directional coupler, comparator, and other related methods are studied in this paper. This is due to each of them has their own advantages and limitations. Monopulse microstrip antenna also can be designed in single and multiple layers. Single layer antenna structure is smaller in size and low cost. However, the downside of this structure is having low bandwidth. On the other hand, the multi-layer structure has a higher bandwidth compared to single layer. Nevertheless, at the same time it is thicker in size, difficult to integrate as well as requires more expensive manufacturing costs. It is found that the combination of a single layered antenna structure design and hybrid coupler has the potential to provide better advantages in terms of simplicity, space and cost.

How Radar Technology Changed the Course of the World after World War II - Science and Technology

After the independent invention of radar in the early 1930s, the development of radar went rapidly during World War II (1939-1945) when both Axis and Allied forces relied on the system to get an edge over the other. Ever since the war, radar technology has substantially increased in its innovation and capability throughout the years. This paper examines the progress of radar technology following World War II (1939-1945) with an aim to provide a landscape of the prevalent radar system during the war which was mono-pulse tracking radar systems and moving-target indication (MTI) system. After a thorough background study of the past radar system, the paper highlights application of the newer developed Phased Array Radar System which was formulated out through the implementation of the improved capabilities of both prevalent systems. Moreover, the paper provides a brief overview of the modular system and formulates a time frame relating to the development of radar research. Thus, the paper, later on, foresees the prominent future where phased array systems could be expanded to civilian and non-civilian technological research by providing thorough research and comparative analysis. Phased array systems are found to a prominent possible cheaper alternative for the civilian and non-civilian system. It shows prominence to be an effective useful tool for radar systems.

저고도 해상표적 추적에서 다중경로 영향 억제를 위한 다중 주파수 모노펄스 방향 탐지 방법

This paper proposed a monopulse method using multiple frequencies to overcome multipath interference in the tracking of low-altitude sea targets. The method determines target elevation candidates by comparing the difference between the measured complex monopulse ratios and those calculated considering multipath interference at three adjacent frequencies. The final target elevation is determined among the candidates by using a cost function set based on the characteristics of the results considering multipath interference. Because the proposed method requires solely the measured target distance and monopulse ratios, it can be applied to the existing monopulse radar system without additional configuration. The suppression effect of multipath interference was verified by a simulation conducted for tracking low-altitude targets in a multipath environment.

Reconfigurable Sum and Difference Beams Based on a Binary Programmable Metasurface

Sum and difference beams are two kinds of field patterns, which have been commonly used in monopulse radar systems for detecting and tracking targets. This letter proposes to synthesize sum and difference beams based on a binary programmable metasurface (BPM). Moreover, the sum and difference beams can be steered by reprogramming digital coding schemes of the BPM. A prototype of the BPM is designed and tested at the Ka-band. Both simulations and experiments validate the presented functions of beam shaping and beam steering.

Simulation of air‐to‐ground ranging mode of airborne monopulse radar over complex terrain

Air-to-ground ranging (AGR) is one of the important operation modes of an airborne monopulse radar system. Here, an approach for the detailed modelling and simulation of the AGR performance of such a radar system over complex terrain is proposed. Time-domain monopulse signals reflected by the terrain's surface were modelled using the dynamics of the airborne platform, clutter properties, and RF specifications of the radar, which included the operating frequency, antenna beam patterns, and pulse repetition time. The AGR performance was then numerically analysed by employing the modelled monopulse return signals and a digital elevation model of the terrain's surface. Several crucial factors affecting the accuracy of line-of-sight estimation, including shadowing effects and roll stabilisation, were addressed using numerical simulations of various scenarios.

Modeling of Monopulse Radar Signals Reflected from Ground Clutter in a Time Domain Considering Doppler Effects

To evaluate the performance of a monopulse radar system, it is necessary to accurately model radar return signals from the ground surface in a time domain. In this paper, we propose a numerical method to model these return signals including radar radio frequency specifications, such as the pulse repetition interval, frequency, and polarization, as well as the antenna geometry, the ground clutter backscattering characteristics, and so on. The Doppler effect is also incorporated into the signal generation scheme because of the dynamics of the platform/clutter and the antenna orientation. The Doppler frequency shift caused by the ground clutter is modeled by employing the time correlation of the received signals. In some scenarios, the monopulse signals are generated and numerically examined. For real radar application, the effect of the platform’s roll stabilization on the monopulse signals is investigated based on the proposed signal generation scheme.

Deception Approach to Track-to-Track Radar Fusion Using Noncoherent Dual-Source Jamming

Dual-source jamming is an effective way to prevent monopulse radar systems from performing accurate angle measurements. In this investigation, based on noncoherent dual-source jamming, we propose a cooperative deception approach, which has the benefit of causing persistent and large angular measurement errors to protect a true target and therefore can greatly reduce the discrimination capability of a distributed track-to-track radar fusion system. A scenario involving a single target accompanied by a digital radio frequency memory (DRFM)-based repeater jammer countering two radar systems is illustrated. By controlling the amplitude ratio and time delay in a statistical manner, the active decoy signal and target echo signal can form a noncoherent angular glint effect and result in the deviation of the angle tracking loop of the two radar systems from the true target in opposite directions. The track-to-track association distance related to the retransmission parameters is explicitly derived, and its statistical characteristics are analyzed in detail. Simulations verify the feasibility of the approach. The advantage of the approach lies in its ability to destroy the so-called “common origin” signature of the physical target by injecting false angular information. The direct result is that the true target might not successfully complete the process of track-to-track association, thereby enabling us to realize the desirable effect of “disguise the true target and instead show false decoys”.

Radiation Patterns Analysis of Monopulse Antenna System

Abstract Monopulse antenna can provide multiple beams simultaneously and use single pulse echo signal to form sum and difference signals for ranging and angle measurement. As the front end of the monopulse radar system, the performance of the monopulse antenna is crucial to the range detection and angle measurement accuracy of the radar system. For the monopulse antenna system, the pattern characteristics determine its performance. In this paper, the factors affecting the pattern characteristics of monopulse antenna are studied.

Radial Line Slot Antenna Design With Groove Gap Waveguide Feed for Monopulse Radar Systems

Radial line slot arrays (RLSAs) are well suited to be used in monopulse radar systems. The excitation of the sum and difference patterns can be achieved by the design of simple feeds as shown in this paper. In this work, a feed system based on the use of a cavity made in groove gap waveguide technology (GGW) is presented. The design is made at 24 GHz but can be easily scaled to higher frequencies as the technology is contact-less and fully made in metal. A good isolation between the sum and difference ports together with a good matching of the two of them is obtained. The radiation patterns of the manufactured antenna are also in good agreement with the simulated ones.

Monopulse Beam Synthesis Using a Sparse Single Layer of Weights

A conventional monopulse radar system uses three beams; sum beam, elevation difference beam and azimuth difference beam, which require different layers of weights to synthesize each beam independently. Since the multi-layer structure increases hardware complexity, many simplified structures based on a single layer of weights have been suggested. In this work, we introduce a new technique for finding disjoint and fully covering sets of weight vectors, each of which constitutes a sparse subarray, forming a single beam. Our algorithm decomposes the original non-convex optimization problem for finding disjoint weight vectors into a sequence of convex problems. We demonstrate the convergence of the algorithm and show that the interleaved array structure is able to meet difficult beam constraints.

항공용 안테나 하이브리드 모노펄스 레이다 시스템의 실용적 표적 방위각 추정 방법

항공용 안테나 하이브리드 모노펄스 레이다 시스템의 실용적 표적 방위각 추정 방법

Design and Response Analysis of Wideband Monopulse Radar System Robust to Noise Jamming Signal

Design and Response Analysis of Wideband Monopulse Radar System Robust to Noise Jamming Signal

Optimal Monopulse Beamforming for Side-Looking Airborne Radars

The synthesis of the optimal excitations of the sum and the difference patterns in planar active electronically scanned arrays ( $\text{AESA}$ s) for side-looking airborne monopulse radar systems is addressed. Under the assumption that each array element is equipped with a single transmit receive module ( $\text{TRM}$ ), which is shared among all patterns, the complex (amplitude and phase) $\text{TRM}$ coefficients are optimized with a customized convex programming procedure to yield a sum beam with maximum directivity and difference beams with maximum slope along the boresight direction as well as asymmetric sidelobes envelope for noise suppression from half-space. Representative results from a synthesized $\text{AESA}$ devoted to a real airborne application are illustrated and discussed to give some insights to the interested readers on the features and the potentialities of the proposed synthesis approach.