Multifunction Radar Research Articles

Design of Real-Time Digital Multi-Beamformer of Digital Array Antenna System for MFR

In this paper, we implement a digital multi-beamformer using FPGA(Field Programmable Gate Array) which has advantages in parallel and real-time data processing. This is accomplished through the use of not only high-speed data communication but also multiple beam forming, which is currently required by MFR(Multi Function Radar). As a result, the beamformer can process 24 Gbps throughput in real-time and form 5 digital beams at the same time. It is also compared to the results of Matlab simulations. We demonstrate how an implemented beamformer can be used in an MFR system by using a digital array antenna.

Multifunction Maritime Radar and RF Systems—Technology Challenges and Areas of Development

Radar systems undertake a number of vital roles in a military environment. They have traditionally been procured and designed to focus on a specific, primary role. Platforms or fighting units often, therefore, have several different radars to cover all the roles required. Multiple radar systems operating on a single maritime platform or in close proximity means some compromises will be made, for example, the siting of the antennas, the management of frequency bands and the type of operation (e.g. from limits of available power, antenna size etc.). It is advantageous to site the radar antenna as high as possible i.e. atop a mast in order to increase the radar horizon and remove any line of site obstruction. As it is desirable to undertake a number of key roles from this prime location this creates the need for a multifunctional radar (MFR).

함정용 레이다 운용을 위한 전광변환장치

Generally, the signal source of active phased array multi-function naval radars is located inside the ship; thus, when an electrical signal source is transmitted to the antenna of the ship, it is difficult to supply a sufficient source to the antenna owing to the distance. In this study, we designed and fabricated an electro-optical conversion device that overcomes this problem by converting electrical signals into optical signals before supplying them. The fabricated device performed electro-optical conversion of the reference signal, local signal, and timing pulses and amplified them using an erbium-doped fiber amplifier module. The sampling and measuring results of 60 output ports showed that the average optical outputs were approximately 2 dB higher than the expected output. Additionally, to protect the operator from high-output optical signals, an interlock function that automatically cuts off the output was applied, and it was confirmed that the interlock function operates normally.

Switchable down-, up- and dual-chirped microwave waveform generation with improved time–bandwidth product based on polarization modulation and phase encoding

A switchable down-, up- and dual-chirped microwave waveform generation technique with improved time–bandwidth product (TBWP) is proposed and demonstrated based on a dual-polarization dual-parallel Mach–Zehnder modulator (DP-DPMZM) cascaded with a polarization modulator (PolM). By properly controlling the phase shifts of the radio frequency signals applied to the DP-DPMZM, switchable down-, up- and dual-chirped waveforms with simultaneous frequency and bandwidth doubling can be generated. To enlarge the TBWP further, splitting parabolic signal and phase-encoding splitting parabolic signal are used to drive the PolM for the enhancement of bandwidth and time duration. Numerical results demonstrate the generation of down-, up- and dual-chirped microwave waveform with TBWP of 8, 160 and 10240. The proposed method may find applications in future multifunction radar systems due to the high performance and flexibility.

A novel segmentation approach for work mode boundary detection in MFR pulse sequence

Understanding and analysis of multi-function radar (MFR) work modes play a key role in radar countermeasures. Many methods have been proposed for recognizing the work modes. However, segmentation of pulse sequence is prior to the mode recognition as the mode transition boundaries are not known in advance for the whole sequence. To solve the boundary detection problem, an unsupervised segmentation method based on recurrence plot (RP) and singular value decomposition (SVD) is proposed in this paper. The method utilizes RP to reveal the characteristic change of the pulse sequence, and makes a quantitative analysis through SVD to extract the main information of work mode. Then, discrepancy measure is employed to detect the boundary, thus determining whether or not the mode transition has occurred. The proposed method can recognize the transition boundaries at different granularity levels. Experimental results show that our method achieves better performance than existing segmentation methods and is robust to non-ideal conditions.

Multifunctional Radar Cognitive Jamming Decision Based on Dueling Double Deep Q-Network

To solve the inefficient and imprecise problem using the Deep Q-network (DQN) algorithm for the radar jamming decision, this paper proposes a multifunctional radar jamming decision optimization method based on the Dueling Double Deep Q-network (D3QN). First, we use a value function reflecting the radar state’s change, and an advantage function related to radar state S and jamming action A to improve the cognitive jamming level for unknown radar modes. Then, using the dueling networks for jamming strategy selection and effectiveness evaluation can further improve decision accuracy. Finally, we propose a prioritized experience replay mechanism during network training to shorten the decision-making time. The experimental results show that our proposed method completes decision tasks 2.1 times more efficiently than the DQN and improves decision accuracy by approximately 10% over DQN.

다기능레이다의 다중 탐색영역 탐색운용기법

In this study, separate search areas are set in the threat area to maximize the operational efficiency of the multi-function radar, and a search operation method for multi-search areas according to their importance, is proposed. In particular, to satisfy the frame time required to fulfill the maximum detection range for each search area, a search ratio calculation method using the search times of each area is proposed. In addition, to satisfy the search ratio, a search operation method is proposed that can meet the requirements for multi-search areas by switching the search area based on the threshold for the search time, for each area. In this study, two search areas with different search waveforms were set, and the achievement of the requirement was mathematically verified. In addition, the suitability of the proposed method was confirmed through performance analysis under various simulation conditions.

Cognitive Electronic Jamming Decision-Making Method Based on Improved Q -Learning Algorithm

In this paper, a cognitive electronic jamming decision-making method based on improved Q -learning is proposed to improve the efficiency of radar jamming decision-making. First, the method adopts the simulated annealing (SA) algorithm’s Metropolis criterion to enhance the exploration strategy, balancing the contradictory relationship between exploration and utilization in the algorithm to avoid falling into local optima. At the same time, the idea of stochastic gradient descent with warm restarts (SGDR) is introduced to improve the learning rate of the algorithm, which reduces the oscillation and improves convergence speed at the later stage of the algorithm iteration. Then, a cognitive electronic jamming decision-making model is constructed, and the improved Q -learning algorithm’s specific steps are given. The simulation experiment takes a multifunctional radar as an example to analyze the influence of exploration strategy and learning rate on decision-making performance. The results reveal that compared with the traditional Q -learning algorithm, the improved Q -learning algorithm proposed in this paper can fully explore and efficiently utilize and converge the results to a better solution at a faster speed. The number of iterations can be reduced to more than 50%, which proves the feasibility and effectiveness of the method applied to cognitive electronic jamming decision-making.

Sequential extraction and recognition of pulse group structure for multi‐function radar

The structure design and switching regulation of pulse groups in multi-function radars (MFRs) are closely related to the work mode. The sequential extraction and recognition of MFR pulse group structure is a fundamental task to analysing and interpreting the work modes and behaviour intentions of an MFR. In this study, the temporal structure of MFR pulse group is expressed hierarchically, which is intensively modelled based on regular grammar. Besides, a corresponding hierarchical automaton is established to sequentially extract and recognise the MFR pulse group structure in pulse train. The hierarchical automaton used for pulse group recognition has a two-layer structure. The bottom layer of the hierarchical automaton realises the sequential input of pulses and recognition of pulse subgroups, and the sequential input of pulse subgroups and recognition of pulse groups are realised at the top layer. The simulation results demonstrate that the proposed method performs satisfyingly in recognising the pulse group structure and is robust to not only pulse noises but also to the emitter number and pulse group scale.

Pulse Deinterleaving for Multifunction Radars With Hierarchical Deep Neural Networks

Multi-function radars (MFRs) work with pulse groups, and pulses in different groups are weakly correlated, which greatly increases the difficulty for MFR pulse deinterleaving, especially in cases of significant data noises. At present, no relevant research results have been reported to address this problem. In this article, a hierarchical deep learning model will be established to describe the sequential patterns of pulse trains from MFRs. The bottom layer of the model represents discrete pulse groups with continuous vectors, which describes the temporal pattern of pulse groups and makes them machine readable. The top layer uses a recursive neural network to mine the sequential pattern between consecutive pulse groups. The two layers are then synthesized to form a hierarchical model, which is able to describe the semantic correlations between different pulses within MFR pulse trains, and the parameters of subsequent pulse groups and their inner pulses can be predicted based on preceding pulses. Based on the hierarchical model, this article proposes an iterative pulse deinterleaving method and a parallel one for MFRs. Simulation results demonstrate that, the proposed methods perform satisfyingly in separating interleaved pulses from radars of the same or different types, and they are robust to significant pulse noises.

Model-Based Time Series Clustering and Interpulse Modulation Parameter Estimation of Multifunction Radar Pulse Sequences

Multifunction radars (MFRs) are sophisticated sensors with significant intelligence, flexibility, and agility. It is important to analyze the system behavior and interpret the intentions of an MFR through the recognition of consecutive work modes in a pulse sequence. With the rapid development of MFRs, the agility capabilities in work mode modulations and the modulation parameters have increased, making the recognition task more challenging. Therefore, it is essential to develop new methods that are more adaptive and less depended on prior information. This article proposes a new method for the time series clustering of MFR work modes named as model-based radar time series clustering. The proposed method considers the variable modulation parameters of submode and employs three algorithms for different assumptions of progressive availability of the priors of a noncooperative MFR. The experiments with four typical pulse repetition interval modulations simulation samples validate the feasibility and the superior performance of the proposed method over the state-of-the-art pulse sequence clustering methods for recognition of MFR work modes.

A Novel Automatic Algorithm for Estimating the Jet Engine Blade Number of Insufficient JEM Signals

One of the major issues in multifunction radars is time resource allocation to maximize the radar’s ability. If jet engine modulation (JEM) is more efficiently performed in an insufficient dwell-time environment, the remaining time can be allocated for other tasks. This study presents a novel automatic algorithm for estimating the jet engine blade number of insufficient JEM signals. We employed a harmonic selection rule and a modified empirical mode decomposition (EMD) with an adaptive low-pass filtering. For a refined autocorrelation waveform, the analysis focuses on a desirable combination of intrinsic mode functions derived from the modified EMD. The approach is significant because it enables reliable estimation despite the insufficient JEM signal. Also, the proposed algorithm is innovative because it uses only the time-domain method, not the frequency-domain method. The application is expected to enhance the efficiency of radar resource management.

Generation of Switchable Chirp Waveforms in the Photonic Domain with Immunity to Dispersion-Induced Power Fading

A novel photonic approach to generating switchable multi-format chirp waveforms using a dual-drive dual-parallel Mach–Zehnder modulator (DD-DPMZM) is proposed and experimentally demonstrated. By properly controlling the bias voltage on the DD-DPMZM, different chirp RF waveforms, including the dual-, down-, and up-chirp waveforms, can be obtained when an RF signal and a chirp RF signal are injected into the modulator. A main feature of this approach is that it can eliminate chromatic dispersion-induced RF power fading, which is highly desired in distributed multi-functional radars based on radio over fiber. There is no polarization control and optical filtering in the given scheme, which also improves the stability and feasibility of the approach. An experiment successfully demonstrated the generation and switching of the multi-format chirp waveforms and the capability of immunity to dispersion-induced power fading.

Multi-Functional Microwave Photonic Radar System for Simultaneous Distance and Velocity Measurement and High-Resolution Microwave Imaging

A photonic-assisted multi-functional radar system for simultaneous distance and velocity measurement and high-resolution microwave imaging is proposed and experimentally demonstrated by using a composite transmitted microwave signal of a single-chirped linearly frequency-modulated (LFM) signal and a single-tone microwave signal. In the system, the transmitted signal is generated via photonic frequency up-conversion based on a single integrated dual-polarization dual-parallel Mach-Zehnder modulator (DPol-DPMZM), while the echo signals scattered from the target are de-chirped to two low-frequency signals using a microwave photonic frequency mixer. By using the two low-frequency de-chirped signals, the real-time distance and radial velocity of the moving target can be measured accurately according to the round-trip time of the echo signal and its Doppler frequency shift. Compared with the previously reported distance and velocity measurement methods, where two LFM signals with opposite chirps are used, these parameters can be obtained using only a single-chirped LFM signal and a single-tone microwave signal. Meanwhile, high-resolution inverse synthetic aperture radar (ISAR) imaging can also be realized using ISAR imaging algorithm. An experiment is performed to verify the proposed multi-functional microwave photonic radar system. An up-chirped LFM signal from 8.5 to 12.5 GHz and an 8.0 GHz single-tone microwave signal are used as the transmitted signal. The results show that the absolute measurement errors of distance and radial velocity are less than 5.9 cm and 2.8 cm/s, respectively. ISAR imaging results are also demonstrated, which proves the high-resolution and real-time ISAR imaging ability of the proposed system.

OO 다기능 레이더 고출력 송신시스템 냉각유(PAO) 누유에 따른 시스템 영향성 연구

다기능 레이더(MFR: Multi Functional Radar)의 고출력 송신시스템(HPTS: High Power Transmission System)에는 하위 시스템과 슬립링로터리조인트(SRJA: Slipring Rotary Joint Ass’y)를 보호하기 위한 냉각 메커니즘이 있다. 다기능 레이더가 고출력 송신 시 일부 구성품들은 약 100℃ 이상의 고온 상태를 유지한다. 시스템의 온도를 안정적으로 유지시키기 위하여 고출력 송신장치(HPTU: High Power Transmission Unit)의 액체냉각장치(LCU: Liquid Cooling Unit)는 냉각유(PAO: Poly Alpha Olefin)를 순환시켜 시스템을 냉각시킨다.<BR>다기능 레이더의 야전 배치 수량이 증가하고 사용연한이 증가함에 따라 PAO 미세누유 식별이 증가하고 있다. PAO 누유로 인한 문제를 해결하려면 고출력 송신시스템의 하위 시스템을 해외에 있는 제조업체에 보내야 하는데 그로 인해 오랜 수리기간동안 공군 방공시스템의 공백이 발생하게 된다.<BR>이 문제를 해결하기 위해 PAO 누유에 따른 영향성을 전기적 영향성, 냉각능력 영향성, 시스템 영향성에 따라 분석하였다. 또한, 현장에서는 신속하고 정확한 누유량 측정 및 누유수준을 판단하는데 어려움이 있으므로 영향성 분석결과를 고려하여 냉각유 누유 문제를 다루는 합리적인 조치 방안을 제시하였다.

Semantic Coding and Model Reconstruction of Multifunction Radar Pulse Train

Retrieving the working modes of multifunction radar from electronic reconnaissance data is a difficult problem, and it has attracted widespread attention in the field of electronic reconnaissance. It is also an important task when extracting benefits from big electromagnetic data and provides straightforward support to applications, such as radar type recognition, working state recognition, radar intention inferring, and precise electronic jamming. Based on the assumption of model simplicity, this study defines a complexity measurement rule for multifunction radar pulse trains and introduces the semantic coding theory to analyze the temporal structure of multifunction radar pulse trains. The model complexity minimization criterion guides the semantic coding procedure to extract radar pulse groups corresponding to different radar functions from pulse trains. Furthermore, based on the coded sequence of the pulse train, the switching matrix between different pulse groups is estimated, and the hierarchical working model of multifunction radars is ultimately reconstructed. Simulations are conducted to verify the feasibility and performance of the new method. Simulation results indicate that the coding theory is successfully used in the proposed method to automatically extract pulse groups and rebuild operating models based on multifunction radar pulse trains. Moreover, the method is robust to data noises, such as missing pulses.

Method for functional state recognition of multifunction radars based on recurrent neural networks

Method for functional state recognition of multifunction radars based on recurrent neural networks

탄도탄 동시 추적을 위한 복합전술에서의 다기능레이다 자원관리 방법에 관한 연구

With the advancements in the field of military technology, recently, the development of weapons systems has diversified and accelerated. Consequently, surveillance systems have become more important. Therefore, a high-performance radar that serves a variety of purposes is required. To meet these requirements, multifunction radar (MFR) that can serve a variety of performance aspects and purposes with single radar is the main part of the surveillance system. Through resource management of MFR, not only common targets, but also hazardous weapon systems, such as ballistic missiles or anti-ship guided missiles, can be detected efficiently. In addition, with the technological developments in the ballistic missile system of North Korea, the ability to respond to ballistic missiles is a challenge. In this study, resource management methods for simultaneous ballistic missile detection and tracking under the condition of detecting normal targets were analyzed using a modeling and simulation (M&amp;S) tool. As a result, the outcomes of resource management changes to simultaneously detect and track 1,000 normal targets and two ballistic missiles were deduced.

해상 상태에 따른 함정 요동에 의한 레이다 성능 변화에 관한 연구

Ship can be placed in various sea condition during missions and is fluctuated by wave according to sea condition and the fluctuation get bigger as the sea condition gets worse. This not only reduces the radar performance but also limits the required operational capability. Therefore, unlike in the case of ground-based radar, the beam of radar operated in the naval vessel must be compensated according to ship motion. For a multi-function radar, the beam is compensated according to the attitude of the ship by electronic beam steering. Electronic beam steering would result in losses; however, if it is not employed, the target may be missed. The radar should be designed considering the margins by analyzing these phenomena in advance. Therefore, in this study, the modeling and simulation (M&amp;S) tool was used to simulate ship motions according to various sea states and to analyze the variation in radar performance. Consequently, it was verified that the variation in radar performance increased as the sea state intensified.

Photonic approach for generating bandwidth-doubled and switchable multi-format chirp waveforms.

A novel photonic approach for generating switchable multi-format chirp RF waveforms is proposed and experimentally demonstrated. The key component in the scheme is a dual-parallel Mach-Zehnder modulator (DPMZM). By properly setting the bias voltage on the DPMZM, different chirp RF waveforms with a doubled bandwidth, including the dual-, up-, and down-chirp waveforms, can be generated, when an unmodulated RF signal and a chirp RF signal are injected. The experiments are implemented to demonstrate the generation of switchable chirp waveforms with bandwidths of 2 and 0.8 GHz. The proposed scheme features its compact structure, easiness in switching control, as well as bandwidth doubling, which has potential applications in multifunctional radars.