Novel Adaptive Dwell Scheduling Algorithm for Digital Array Radar based on Pulse Interleaving

The digital array radar (DAR) is a fully digitized phased array radar in which digital beam forming technique is used both in receive and transmit. A lot of simulations are made about the influence of amplitude-phase error on the antenna pattern, since amplitude-phase error of the antenna will severely affect the performances of the digital array radar. Based on the far-field external monitoring principle, the amplitude-phase error calibration method of the digital processing is studied, and the “in-the-field calibration” method, combining the reference data and the mid-field monitoring, is finally presented. Besides, the key techniques of the real-time DBF based on the FPGA processing platform are analyzed. The test results show that by using the method proposed, the high-precise calibration data can be obtained and the antenna beam after calibration can meet the digital array radar's requirements, and moreover the FPGA processing platform can realize the real-time multi-beam processing. It is a probe that the method combines the reference data and the mid-field monitoring, which is a simple, feasible and effective method for the digital array radar in the field calibration.

An Entropy-based PSO for DAR task scheduling problem

Digital Array Module (DAM) is one of the key components of digital array radar (DAR). Usually, a DAR contains tens to hundreds of DAMs, which is making it increasingly difficult for human operators to test them in limited time. Therefore, the technique for automatic test of DAMs is in urgent demand. This paper presents a DAM automatic test system (ATS) that has proved successful in several radar test projects. We first analyze the requirement of automatic test according to characters of DAM. After that we propose a brief of comprehensive framework as well as the design scheme of hardware and software. We finally discuss the method of testing data acquisition and algorithm for calculating performance indexes. Application examples have shown that the system can meet the great demand of testing tasks with high automation, efficiency, and accuracy.

In this paper, frequency broadband signal beamforming methods of digital array radar (DAR) are researched and broadband signal adaptive beamforming is realized through MVDR rule. Simulation and comparison show that blocked DFT beamforming method has advantage of little calculating quantity. For non-superposition of each block destroy the relativity of signal, blocked DFT make aberrance to pulse compression and take bad influence in succedent processing. Sliding-window DFT beamforming can achieve good performance of pulse compression, but it has large calculating quantity. Improved DFT beamforming method has the same calculating quantity with blocked DFT method, and it doesn't destroy the relativity of signal so that it can achieve good performance of pulse compression and in succedent processing. Improved DFT beamforming method is fit for used in engineering. The result of its application in DAR has been given.

In this paper some potential system and processing advantages of conformal cone shaped digital array radar have been investigated, in particular in relation to potential alternative approaches for angle estimation with respect to the traditional monopulse. First of all potential benefit in terms of reduction of the number of radiating elements is shown when a conical array is considered with respect to a traditional system formed by four planar arrays, if a coverage of 360° must be assured. Secondly, having in mind an innovative digital array system where the received signals are analog to digital converted at element level and the corresponding data are possibly transferred to a central elaboration unit, an alternative approach is investigated for angular estimation. In this paper we derive the theoretical expression of the Cramer Rao Lower Bound for elevation angle estimation using a cluster of beams; we compare the limit performance of the traditional approach for angle estimation based on Sum and Difference beams with the approach based on a crowded cluster of RX beams properly spaced. The approaches show approximately equivalent performance, making the second particularly interesting for those situations where monopulse is known to experience performance degradation, as low elevation angle estimation; in this particular case an example of cluster design is shown, where the direct signal from a low altitude target must compete with a specular multipath.

In this paper, a 10-channel digital array module(DAM) based on software radio theory model is designed for VHF-wave digital array radar. Up to now, DAM has fulfilled all project design requirements.

The traditional power allocation method for multi-target localization adopts the Robust Chance Constrained Power Allocation Scheme (RCC-PA), which does not consider the strong clutter characteristics in the current radar detection environment. However, how to reasonably allocate the power required for the radar to locate the target in the strong clutter is a fundamental challenge for improving the combat capability of the radar. Since Simultaneous Multi-beam Digital Array Radar (SM-DAR) can provide high-resolution information on targets in strong clutter, this paper extends the RCC-PA scheme to strong clutter and introduce an extended target model suitable for high-resolution SM-DAR. At the same time, the Gamma distribution is used to reflect the statistical characteristics of the Radar Cross Section (RCS) so that the extended RCC-PA scheme (ERCC-PA) can be suitable for all the scatterers whose RCS belong to Gamma distribution families. In the ERCC-PA scheme, the Strong Clutter Information Reduction Factor (SCIRF) of the extended target is first derived. Then, a Gamma Chance-constraint Programming Model (Γ-CCP model) is constructed to optimize the power allocation for locating multiple extended targets in strong clutter. The extended dichotomy method for power allocation is also given. Theoretical analysis shows that the power of multi-target localization in strong clutter can still be reasonably allocated under the target with multi-measurement characteristics. In addition, the power distribution of multi-target localization in the strong clutter is negatively correlated with the shape parameter of the Gamma distribution. Specifically, the larger the shape parameter characterizes the larger individual strong scatterer, resulting in the SM-DAR requiring less positioning power. The experimental results verify the theoretical analysis and show that the ERCC-PA scheme can improve the utilization of power compared with the benchmark and has the advantage of robustness to the fluctuation of the target RCS.

Fully digital phased array radars (PAR) enable rapid scanning of severe weather phenomena with high temporal and spatial resolution through adaptive beamforming and other advanced methods. An important challenge with such systems is the transferring, processing, and storing of the vast amount of data that can be produced, especially if element-level data are needed. Therefore, reduction of I/Q data size should be investigated when considering fully digital arrays for both scientific and operational needs. In this research, the effects I/Q linear quantization on polarimetric weather radar products has been examined. Among other effects, the results show that pulse compression effectively reduces quantization noise while maintaining the peak storm structure. As expected, negative quantization effects increase with lower signal-to-noise ratio (SNR).

Digital array radar (DAR) can fully realize digitalization at both the transmitting and receiving ends. However, the development of freedom at the transmitting end is far from mature. So, the new concept of multi-dimensional waveform coding array has appeared, which can optimize the transmitting resources in space–time/frequency waveform or another dimension. Space–time coding array (STCA) is a typical kind of multi-dimensional waveform coding array, which can make full use of the high degree of freedom at the transmitting end. It realizes emission diversity by introducing a small time delay between different transmission array elements. In this paper, an optimization method for STCA, which combines the array spatial coding at the transmitting end and mismatched filter design at the receiving end, is proposed. This method aims to solve the sidelobe problems of STCA: the inherent resonance phenomenon and the resolution loss problem. The experimental verification and quantitative comparative analysis prove the effectiveness of the proposed method. The resolution is restored to the ideal level under the premise of maintaining the beam-scanning ability and ultra-low sidelobe, and the resonance phenomenon caused by spectrum discontinuity is eliminated simultaneously.

Modern digital arrays radars (DAR) contain a large number of T/R modules. T/R module system is a critical part of digital array radar. It is necessary to test T/R module strictly before it is set up into the DAR. In practice, manual testing the T/R module with high performance is a complex and hard work, which for the difficulties of heavy test task and complex operations. In order to realize the automatic test of the active T/R modules, the advanced modern automatic test system (ATS) is built based on GPIB bus. The composition and the operation principle of the digital T/R module are introduced and the design of the hardware platform and software system is discussed. The high power measurement in transmitter and broadband data processing in receiver is researched. The timing control design is also introduced. Compared with manual test, the system is applied successfully shortens the test time to 1.5 hour from the manual 48 hours and the consistency of amplitude and phase between receiving channels is calculated automatically. The results showed the ATS can enhance the data processing speed and increase the testing efficiency of T/R module test.

In this paper, an X-band, 8-element wideband digital array radar (DAR) test-bed is presented, which makes use of a novel digital backend coupled with highly-integrated, multi-channel intermediate frequency (IF) digital receiver. Radar returns are received by the broadband antenna and then down-converted to the IF of 0.6GHz-3.0GHz. Four band-pass filters are applied in the front-end to divide the IF returns into four frequency bands with the instantaneous bandwidth of 500MHz. Every four array elements utilize a digital receiver, which is focused in this paper. The digital receivers are designed in a compact and flexible manner to meet the demands of DAR system. Each receiver consists of a fourchannel ADC, a high-performance FPGA, four DDR3 chips and two optical transceivers. With the sampling rate of up to 1.2GHz each channel, the ADC is capable of directly sampling the IF returns of four array elements at 10bits. In addition to serving as FIFO and controller, the onboard FPGA is also utilized for the implementation of various real-time algorithms such as DDC and channel calibration. Data is converted to bit stream and transferred through two low overhead, high data rate and multi-channel optical transceivers. Key technologies such as channel calibration and wideband DOA are studied with the measured data which is obtained in the experiments to illustrate the functionality of the system.

This study proposes the Space–time Radon–Fourier transform (STRFT) for wideband digital array radar (DAR). It is a novel coherent detection technique that jointly realise wideband digital beamforming (DBF), range compression and long-time coherent integration. The likelihood ratio detector (LRT) is first derived based on the three-dimensional (3D) signal model of moving targets, which is the output of the STRFT on the 3D range-compressed echoes. Some transform properties of the proposed STRFT are also discussed. This include the 3D impulse response, 3D translational invariance, multi-target linear additivity, linear SNR gain in additive white Gaussian noise (AWGN), as well as the 3D correlation function of transformed AWGN. Also, the fast implementation of STRFT is proposed in the element-pulse-range frequency domain, which is realised via the two dimensional Chirp-Z transform (CZT) based on fast Fourier transform (FFT) operators. The proposed method may remarkably reduce the computational burden for modern wideband DAR. Finally, some numerical experiments are provided to demonstrate the effectiveness of the proposed methods.

Adaptive dwell scheduling for simultaneous multi-beam radar system based on array element selection with different polarization characteristics

We detail a delta-sigma based system built to produce high-resolution analog waveforms at UHF. With bandwidths as large as 80 MHz and noise floors as low as -140 dBc/Hz, the generated waveforms show potential for use as LO and RF transmission waveforms in a UHF radar system. Finally, the waveform generator system is described as an ideal technology for use in a digital phased array radar.

This paper focuses on the cascaded two-level DBF structures of digital array radar processing system. A real time processing platform is designed and implemented, including hardware system establishing and algorithm mapping, based on general purpose COTS modules. The signal processing system is scalable, restructurable, could satisfy the processing requirement of digital array radar.