Technique for spatial interference reduction and its application in monopulse radar with active phased array antenna

During the service process of active phased array antenna (APAA), factors such as array heating and wind loading cause significant deformation, which will seriously affect the electromagnetic (EM) performance. Obtaining the geometric parameters of the array through sensors and predicting the real-time EM performance based on the digital twin (DT) technique are crucial to guarantee the service quality of the array antenna (e.g., the detection accuracy of a target). Traditional offline simulation methods can calculate the real EM performance of APAA with geometric errors. However, it requires a large number of computational resources and computation time, which is difficult to meet the demand for real-time prediction in DT. In this article, a generalized DT framework based on the reduced-order model for APAA is proposed. First, we introduce a dynamic-static attention-enhanced convolutional network for real-time computation of key EM indicators. Then, a super-resolution generating network is proposed, which realizes the mapping of array geometrical errors to the 3-D far-field pattern, and provides support for comprehensive performance evaluation. The framework proposed in this article constructs a twin model of APAA, realizes the virtual-reality mirroring of the EM performance, and is deployed and applied in an APAA DT platform.

The basic principles of building a promising domestic regional satellite communication system "Express-RV", based on the highly elliptical orbit "Molniya" and intended for broadband access of civil sector subscribers to various public communication networks, in particular to the Internet, are considered. The main technical requirements for the antenna systems of mobile satellite communication terminals of the Express-RV system are formulated. The necessity of using active phased array antennas for a number of types of such terminals is justified. A brief overview of the principles of implementation and examples of the design of microstrip active phased array antennas, including their elementary emitters and individual modules, are given. The problem of the occurrence of the blinding effect inherent in flat microstrip gratings made on dielectric substrates is noted; measures to compensate for this effect are considered. The possibility of expanding the maximum scanning angle of a narrowly directed beam of an active phased array antenna by using a magnetically controlled scattering dielectric lens, as well as creating segment-dome structures of antenna systems in relation to mobile terminals of mobile satellite communications of the "Express-RV" system, is shown. Simple analytical relations are derived that allow us to estimate the number of elementary emitters required for the implementation of a receiving-transmitting active phased array antenna with specified technical characteristics: gain and maximum scanning angle; the corresponding dependencies are given. The cost of creating an antenna system based on an active phased array is estimated.

This paper proposes a 2x4 microstrip antenna array for mono-pulse tracking radar in the S-Band. In the proposed design, a rat-race coupler is paired with a 2x4 patch antenna array at 3GHz. The feed is given to the sum and difference ports of the rat-race coupler to obtain the sum and difference patterns. The design aims to help in tracking. The tracking is done in one-dimensional space, and the design has limited elements with better efficiency. In the proposed design, the simulated and measured results have a return loss of at least - 10 dB at 3 GHz and the sum pattern has a main lobe and side lobe difference of at least 12 dB, while a null depth of at least 20 dB is achieved in the difference pattern. A gain of 17 dB has been noted. The simulation of this design was done on Ansys HFSS and MathWorks Antenna Toolbox softwares with an epsilon value of 2.2 of the Rogers RT 5880 substrate with a thickness of 1.6 mm. The design also contains chamfered elements to decrease the side lobe levels.

Strengthening the role of unmanned aerial vehicles (UAVs) for various purposes due to their group use allows obtaining a number of advantages in solving a wide class of tasks. At the same time, the new advantages of group use of UAVs are due to: the difficulty of separate observation of the group members and, accordingly, the difficulties of tracking and target distribution; the inability to serve the entire large group with the number of participants exceeding the capacity of the information control system of the opposing side; the increase in the behavioral complexity of the UAV in solving various problems through the use of artificial intelligence; random change of the spatial position of individual UAVs within the group, preventing their detection and selection of virtually all types of information systems. The noted advantages of the UAVs groups are especially pronounced in the implementation of such a new task as the formation and use of temporary active phased antenna arrays (APAA) of large sizes based on multicopter for the implementation of long-range radar systems. In this regard, the purpose of the paper is to present a variant of the algorithm for the formation and functioning of such a APAA. On the example of solving the task of maintaining an air object, the features of the operation of a radar with a APAA based on a group of UAVs are illustrated.

A study of the methodology for correcting the distortion of the radiation pattern parameters caused by the mutual influence of emitters is presented on the example of a rectangular active phased array antenna with the number of emitters: 64 in the azimuthal plane, 8 in the angular plane. The dependence of the main characteristics of the radiation pattern on the deflection of the beam during electronic scanning and changes in the intensity of the electromagnetic field during the formation of the cosine-square amplitude distribution on the pedestal is considered. The characters of the dependencies are determined and a technique is proposed for controlling the distortion of the characteristics that occur when the beam is deflected. The implementation of the technique allows to adjust the parameters of the radiation pattern, which has distortions due to changes in the mutual influence of the emitters, to obtain the required characteristics of the active phased array antenna, to use operating modes that require the parameters of the antenna array to remain unchanged.

This paper presents the design and measurement results of a new active phased antenna array using Injection- locking oscillators. The required phase relation for each array element is obtained by electronic tuning through injection-locking technique, and the beam-scanning capability is demonstrated, so a shifterless beam scanning method is proposed, and its feasibility is verified through 1times4 element phase array.

The results of the analysis of the energy consumption of the transmitting active phased antenna array (APAA) of a spacecraft of the low-orbit communication system (with broadband access or with direct access to cellular subscribers) have been presented. It has been shown that in order to reduce energy consumption by switching on (off) the emitters, depending on the beam deflection angle from the nadir, it is possible to achieve a significant reduction in the heat release of the spacecraft’s APAA. But this solution is feasible only if the APAA forms one “jumping” beam.

This paper proposes an analytical formulation of the instrumental errors in multilevel hierarchic SAR architecture equipped with active phased array antennas. The basis of the study is the derivation of the so called post-calibration errors, which remain as residual error contributions after the application of a dedicated internal calibration procedure. The limitations of the current internal calibration approaches for the-state-of-the-art space-borne SAR missions are analyzed and alternative internal global calibration strategies are proposed to reduce the impact of the post-calibration error. Numerical simulations of instrumental errors are presented to evaluate the different proposed calibration procedures.

We propose an S-band active phased array antenna (APAA) with analog phase shifters (PSs) that use double-balanced mixers (DBMs). The quadrature phase shift keying modulator integrated circuits (ICs) used as the phase shifters can control both the amplitude and phase of the input signal continuously and independently by using the control voltages. The phase and amplitude errors during phase rotation were 0.5/spl deg/ rms (max=1.7/spl deg/) and 0.3 dB rms (max=0.7 dB), respectively. The range in which the amplitude could be linearly changed was 7 dB. The proposed antenna exhibited sufficient performance for mobile vehicles to handle satellite communications: beam-pointing resolution of 0.04/spl deg/, beam-pointing accuracy in the null pointing of 0.4/spl deg/ rms, and sidelobe suppression with an amplitude taper achieved by setting the amplitude of the PS using two DBMs. Comparison between the analog PS and a reflection-type four-bit digital PS showed that although the analog one is unsuitable for use in a passive PAA, it is suitable for use in an APAA.

Radar detection equipment with active phased array antennas (APAA) as signal transceiver is an important part of modern communication and military warfare, while the various uncertainties arising from the manufacturing assembly and operating environment of the antenna have a substantial impact on the detection performance of active phased array radar. Consequently, it is essential to examine the influence of these uncertainties on radar detection capability and explore robust strategies for performance regulation. This paper takes the APAA with antenna detection as a function as an object, the deviation analysis of antenna gain, sidelobe level and half-power beamwidth on the maximum detection range is realized, the interval amount calculation formula of ranging and angular detection accuracy is derived, and the influence of half-power beamwidth on target resolution is analyzed. Then an APAA performance guarantee method based on interval refinement is proposed. The proposed method is validated by comparing its compensation results with those of conventional optimization algorithms, revealing clear advantages in both computational efficiency and compensation accuracy. A case study is conducted to evaluate the performance of the proposed method, and the results show that the proposed method can effectively reduce the interval size of the amplitude and phase compensation of the excitation current and significantly improve the antenna detection performance.

In this paper a low cost/complexity modular architecture for electronically scanned active phased array antenna (A-PAA) for high throughput K/Ka-band mobile satellite communication (SATCOM) is presented. With this approach, A-PAAs of any size, shape, and configuration can be built of intelligent building blocks (active sub-array modules) to minimize the design complexity and fabrication cost. The design and fabrication aspects of K/Ka A-PAA with wide scanning angle range is presented. The measured results of the modular array show that the antenna main beam can be steered to ± 70o off the boresight at 20/30 GHz. Furthermore, the antenna is able to achieve EVM ~ 7.60 % during the constellation test for 16 QAM and 1.2 Gb/s.

Advanced method for calibrating individual modules of active phased antenna arrays (APAA) has been introduced earlier [1-4]. This method allows fast and accurate characterization of every modules. As calibrating sequences set pseudo-noise sequences (PN-sequences, Kasami codes, Gold sequences etc.) can be used, but introduced additional measurement error due to mutual interference between sequences in one set. Decorrelation algorithm of reducing this error has been introduced earlier [5]. But it requires sequences set size as large as number of APAA-channels so it can be costly to implement it for large-size APAA. In this paper authors discuss variant of decorrelation algorithms with repeated use of sequences which allow of using small set of pseudo-noise sequences in calibrating systems.

A transmission double-line, with low attenuation and low voltage standing wave ratio (VSWR) for the calibration of X-band active phased-array antennas, was designed and manufactured. The transfer function from a fed element of active phased-array antennas to the double-line was measured. The transmission double-line is used to monitor and correct the element phase error of an active phased-array antenna. Radiation patterns before compared to after calibration show that the approach is useful.

Array antennas are popular in radar and communication applications. It is possible to control the pattern characteristics from array antennas very effectively and easily. Array designers used different techniques to produce narrow beams. But it is essential to produce not only narrow beams but also other beam shapes like Square and Cosecant beams. These shaped beams are extremely useful in search, track radars and also for ground mapping. The difference patterns are often produced from sum patterns with additional phase, but in the case of marine radars either sum or difference patterns are asymmetrical in their sidelobe structure. In view of the above facts intensive investigations are carried out in the present work to generate asymmetrical difference patterns form Cosecant patterns with Fourier series, Fourier Transform and Woodward-Lawson methodologies.

The results of the research of the developed fiber-optic transmission systems for analog high frequency signal are represented. On its basis, a new method to identify various structural defects in the active phased antenna arrays is elaborated.