Digital Antenna Research Articles

Вероятностная оценка обнаружения радиолокационного сигнала цифровой антенной решеткой с пространственно-корреляционным методом обработки сигналов.

Вероятностная оценка обнаружения радиолокационного сигнала цифровой антенной решеткой с пространственно-корреляционным методом обработки сигналов.

Design and analysis of the digital phased antennas characteristics using modern systems of the atomized design (CAD)

There are discussed methods of the digital phased antennas design using the modern (computer aided design) CAD. There are given examples of digital antenna blocks and elements design using different CADs.

First analysis of inclined air showers detected by Tunka-Rex

The Tunka Radio Extension (Tunka-Rex) is a digital antenna array for the detection of radio emission from cosmic-ray air showers in the frequency band of 30 to 80 MHz and for primary energies above 100 PeV. The standard analysis of Tunka-Rex includes events with zenith angle of up to 50?. This cut is determined by the efficiency of the external trigger. However, due to the air-shower footprint increasing with zenith angle and due to the more efficient generation of radio emission (the magnetic field in the Tunka valley is almost vertical), there are a number of ultra-high-energy inclined events detected by Tunka-Rex. In this work we present a first analysis of a subset of inclined events detected by Tunka-Rex. We estimate the energies of the selected events and test the efficiency of Tunka-Rex antennas for detection of inclined air showers.

Digital beamform simulation in anechoic chamber

The results of digital beamform simulation, principles of processing and use of the obtained experimental data are presented. Methods were developed and an experimental setup was created for full- scale modeling and measurement of the characteristics of digital antenna systems with spatio-temporal signal processing at the Scientific and Production Center for Radio Information Metrology of the Moscow Aviation Institute (SPC RIM MAI).

Signal recognition and background suppression by matched filters and neural networks for Tunka-Rex

The Tunka Radio Extension (Tunka-Rex) is a digital antenna array, which measures radio emission of the cosmic-ray air-showers in the frequency band of 30-80 MHz. Tunka-Rex is co-located with the TAIGA experiment in Siberia and consists of 63 antennas, 57 of them are in a densely instrumented area of about 1 km2. In the present workwe discuss the improvements of the signal reconstruction applied for Tunka-Rex. At the first stage we implemented matched filtering using averaged signals as template. The simulation study has shown that matched filtering allows one to decrease the threshold of signal detection and increase its purity. However, the maximum performanceof matched filtering is achievable only in case of white noise, while in reality the noise is not fully random due to different reasons. To recognize hidden features of the noise and treat them, we decided to use convolutional neural network with autoencoder architecture. Taking the recorded trace as an input, the autoencoder returns denoised traces, i.e. removes all signal-unrelated amplitudes. We present the comparison between the standard method of signal reconstruction, matched filtering and the autoencoder, and discuss the prospects of application of neural networks for lowering the threshold of digital antenna arrays for cosmic-ray detection.

Methods beamforming adaptive digital array and their study using a computer model

The article describes the computer model of an adaptive digital antenna array. We considered in detail its features and specifications. The results of experimental research methods beamforming digital adaptive antenna array using a computer model. We studied four methods of providing independent beams forming the directivity pattern, calibration of the receiving channels, interference suppression and measurement navigation parameters.

Theoretical Analysis and Experimental Measurement of Digital Multi-Beam Phased Antenna Array in the C-Range

The choice of element for constructing a phased antenna array (PAA) providing a relative frequency bandwidth up to 9% for the transmission or reception of wireless communication system information was carried out. There are three methods to suppress of side lobes and diffraction of PAA in the radiation far field. Superposition of excitation signals of a flat PAA for simultaneous emission of several independent beams in a radiation far field was used. Сalculation and optimization of progressive distribution of phase shifts in the excitation signal group in the horizontal and vertical directions in the plane of PAA for radiation (reception) of independent beams in spherical coordinates (azimuth and elevation) in space was performed. An experimental sample of a phased antenna array was developed using microstrip technology, which forms several beams in a radiation far field. An experimental measurement of the voltage standing wave ratio and relative frequency bandwidth of the sample developed by phased array microstrip and printing technology was carried out.

Determination of radiation pattern for linear antenna array with multistage adaptive compensator of interferences

Introduction. Adaptive compensation algorithms of interference in digital antenna array (DAA) are characterized by high computational complexity. As result, it makes it difficult to implement them in real time. A parallelization of computational processes and simultaneous processing in all parallel channels is one of the main directions of increasing the speed of processing. The approach based on block Gram-Schmidt orthogonalization makes it possible to synthesize multistage adaptive compensators of interference with parallel-sequential signal processing that similar to the architecture of multiprocessor computer systems. The signal processing in DAA based on multistage adaptive compensator of interference is more complex than in single-stage ones. Each stage has own set of weight coefficients. As result, a technique for calculating radiation pattern (RP) of a linear DAA with a multistage adaptive compensator of interference and certain architecture and parameters is required. Theoretical results. The block diagram of the adaptive compensator of interference by using block signal orthogonalization of compensation channels and consistent determination of the compensation error has a ladder form and includes some stages. Each stage consists groups of modules. Each module in the group is a multi-input weight adder. The complex signal envelope from the DAA output applies to the main channel of an adaptive compensator of interference. The technique for calculating RP of DAA with a multistage adaptive compensator of interference by using block orthogonalization of compensation channels signals includes the following steps: 1. Forming of the matrix impulse characteristics for the adaptive compensator of interference stages. 2. Calculation of the matrix impulse response for a multistage filter realizing an interference compensation procedure based on its factorized representation. 3. Determination of the weight coefficients of an equivalent single-stage adaptive compensator of interference in the form of multi-input weighted adder. 4. Calculation of the RP of DAA with an equivalent single-stage adaptive compensator of interference. Experimental results. RP analysis based on the proposed technique is carried out for six-element linear DAA with one-, two-, three- and six-stage adaptive compensators of interference and three jammers. The analysis confirms that considered adaptive compensators of interference have the same effectiveness of interference elimination. In the same time, they are characterized by the same accuracy of "zeros" formation on interference sources and the width of rejection zone for different values of correlation matrix conditioning of the interference. Conclusions. We propose the technique for calculating the RP of DAA with multi-stage adaptive compensator of interference by using the factorized representation of the matrix impulse response of a multistage filter. This compensator is based on block signals orthogonalization of compensating channels and provides parallel-sequence signal processing.

Controlling Radiation Beams by Low-Profile Planar Antenna Arrays with Coding Elements.

Beam diversity enables antenna arrays to play important roles in radar, communications, imaging, and next-generation wireless systems. However, achieving flexible control of beams in a low-cost way is still very challenging. Here, we propose low-profile planar antenna arrays with coding elements to control and engineer radiation patterns more freely and flexibly. The proposed planar antenna array consists of binary radiating elements which are characterized by digital codes “0” and “1”. By designing spatial coding patterns of the radiating elements, multifarious functionalities can be well realized, such as beam splitting, beam scanning, and beam deflection. More importantly, coding metasurfaces can be properly arranged around the digital radiating elements to reduce the radar cross section of the antenna, while the radiation performance is well preserved. The low-profile, high-gain, lightweight digital antenna arrays are verified numerically and experimentally in the microwave band. The proposed digital coding planar antenna arrays derive a new paradigm to control the radiation patterns in low-overhead and advanced digital design fashions and offer promising applications in multitasked and intelligent antenna devices and new information systems.

Theoretical Complexity of Grid Cover Problems Used in Radar Applications

Modern radars are highly flexible systems, relying on digital antennas to dynamically control the radar beam shape and position through electronic circuits. Radar surveillance is performed by sequential emission of different radar beams. Optimization of radar surveillance requires finding a minimal subset of radar beams, which covers and ensures detection over the surveillance space, among a collection of available radar beams with different shapes and positions, thus minimizing the required scanning time. Optimal radar surveillance can be modelled by grid covering, a specific geometric case of set covering where the universe set is laid out on a grid, representing the radar surveillance space, which must be covered using available subsets, representing the radar beams detection areas. While the set cover problem is generally difficult to solve optimally, certain geometric cases can be optimized in polynomial time. This paper studies the theoretical complexity of grid cover problems used for modelling radar surveillance, proving that unidimensional grids can be covered by strongly polynomial algorithms based on dynamic programming, whereas optimal covering of bidimensional grids is generally non-deterministic polynomially hard.

Метод моделирования скалярного поля радиопомех декаметрового диапазона, рандомизированного цифровой антенной решеткой.

Метод моделирования скалярного поля радиопомех декаметрового диапазона, рандомизированного цифровой антенной решеткой.

Развитие схемотехники ЦАР: некоторые итоги. Часть 2

Развитие схемотехники ЦАР: некоторые итоги. Часть 2

Оценка допустимого интервала времени обновления задержек распространения сигнала между антеннами цифровых антенных полей

Оценка допустимого интервала времени обновления задержек распространения сигнала между антеннами цифровых антенных полей

Integrated Positioning System With Restricted Access to Navigation Satellite Signals

Abstract Global satellite navigation system (GNSS) is by far the most cost-effective outdoor positioning technology currently available and used for many types of applications. In some cases a user may face difficult conditions, like restricted access to the navigation satellites due to natural or man-made phenomena. This paper presents an idea of an integrated positioning system capable of functioning under limited visibility conditions of navigation satellites. The system includes a digital antenna array, channels for converting radio navigation signals, a phase difference meter, a gyro platform with 3 gyros, an altimeter and a special calculator. With the help of mathematical modeling, the accuracy characteristics of the system are investigated by determining the coordinates of the carrier under conditions of a small number of available satellite signals.

Radar station with digital axisymmetric active phased antenna array as a promising direction for the development of surveillance radars

The purpose of the study was to build a surveillance radar station (radar) with an axisymmetric (i.e. cylindrical, conical, etc.), multibeam receiving-transmitting active phased array (APAR) and investigate its characteristics. The radar station makes it possible to shorten the surveillance time, increase the rate of updating information, provide flexibility in changing operating modes, increase the reliability and service life of a radar station as compared to a radar station with mechanical rotation of antenna systems. The radar station is compared with electronic circular scanning based on cylindrical, three- and tetrahedral APAR

Синтез устойчивого разностно-равносигнального метода автосопровождения космического аппарата цифровой антенной решеткой

Синтез устойчивого разностно-равносигнального метода автосопровождения космического аппарата цифровой антенной решеткой

High-accuracy direction finding of arbitrarily correlated multipath signals with the use of digital antenna arrays

An algorithm of direction finding of a set of arbitrarily correlated multipath harmonic and quasiharmonic signals in the presence of a normal white noise is substantiated. Results of numerical simulation for different variants of correlation between signals arriving at the input of a circular antenna array are presented. It is shown that, in order to increase the accuracy of determination of directions of arrival, number, and amplitudes of the arriving signals with the use of the proposed algorithm, it is expedient to perform preliminary fast Fourier transform procedure with subsequent direction finding at each frequency component.

Improved absolute calibration of LOPES measurements and its impact on the comparison with REAS 3.11 and CoREAS simulations

LOPES was a digital antenna array detecting the radio emission of cosmic-ray air showers. The calibration of the absolute amplitude scale of the measurements was done using an external, commercial reference source, which emits a frequency comb with defined amplitudes. Recently, we obtained improved reference values by the manufacturer of the reference source, which significantly changed the absolute calibration of LOPES. We reanalyzed previously published LOPES measurements, studying the impact of the changed calibration. The main effect is an overall decrease of the LOPES amplitude scale by a factor of 2.6 ± 0.2, affecting all previously published values for measurements of the electric-field strength. This results in a major change in the conclusion of the paper ‘Comparing LOPES measurements of air-shower radio emission with REAS 3.11 and CoREAS simulations’ published by Apel et al. (2013) : With the revised calibration, LOPES measurements now are compatible with CoREAS simulations, but in tension with REAS 3.11 simulations. Since CoREAS is the latest version of the simulation code incorporating the current state of knowledge on the radio emission of air showers, this new result indicates that the absolute amplitude prediction of current simulations now is in agreement with experimental data.

LOPES — Recent Results and Open Questions on the Radio Detection of Air Showers

LOPES was a digital antenna array operating for approximately 10 years until spring 2013 at the Karlsruhe Institute of Technology (KIT). Triggered by the co-located KASCADE-Grande air-shower experiment, it measured the radio signal of around 1000 cosmic-ray air showers with energies E ≳ 1017 eV in an effective band of 43 – 74 MHz. Using the interferometric technique of cross-correlation beamforming, LOPES could reconstruct the shower direction with an accuracy < 0.7°, the shower energy with a precision < 20%, and the atmospheric depth of the shower maximum, Xmax, with a precision < 95g/cm2. In particular the reconstruction of the shower maximum suffers from significant measurement uncertainties due to the radio-loud environment of the site. This article summarizes our latest results on the reconstruction of the shower maximum, using two independent methods: the steepness of the hyperbolic radio wavefront and the slope of the lateral distribution of the radio amplitude. Moreover, we show vectorial measurements of the electric field with the tripole antennas of the latest LOPES setup. Finally, we discuss open questions as well as the potential impact of the lessons learned at LOPES for future antenna arrays.

Hybrid Analog–Digital Antenna Array With Built-in Image Injection Calibration

This study presents a hybrid receiving array architecture that combines analog and digital beamforming to offer a solution for the phased-array feed and other multifunction receive-only applications. This architecture is capable of handling multiple beams forming simultaneous and precision beam steering. To further reduce the hardware counts of the online performance monitoring, a calibration method is proposed in which none of the transmitters or the dedicated distribution network are used. The hybrid architecture concept and built-in calibration are validated experimentally via a prototype. The system performance, including the statistical results of the baseband measurement, phase error, and radiation patterns under various array configurations, are illustrated. An effective phase tuning step of 0.1 ° , as well as a steering resolution at the subdegree level, is achieved, and the measured aperture distribution is in good agreement with that derived from the proposed online calibration.