Combined Antenna Array Research Articles

OAM mode purity improvement based on antenna array

Orbital Angular Momentum (OAM) waves are characterized by helical wave fronts and orthogonality between different modes. Therefore, OAM waves have huge potential in improving wireless communications' channel capacity and radar imaging's resolution. Consequently, the generation and application of OAM waves have attracted a lot of attention. And many methods are proposed to generate OAM waves. Although antenna array is the most popular method of generating OAM waves, OAM waves generated by antenna array have redundant modes. However, all advantages of OAM waves are closely related to infinite OAM modes. Thus, to better apply OAM waves to wireless communications and radar, it is very important to reduce unnecessary OAM modes and improve the OAM mode purity. In order to improve the OAM mode purity, two combined antenna arrays composed of X direction antenna and Y direction antenna array are proposed in this paper. The X direction antenna array and the Y direction antenna array are supplied by the excitations with the same amplitude and fixed phase shift. The overall phase shift of the X direction antenna array is π/2 more or less than that of the Y direction antenna array. The results of formulas and antenna models in CST show that the combined antenna arrays can generate OAM waves with less redundant modes in x component, y component and z component. Besides, the z component carries pure OAM modes.

Arrays of combined antennas with equal-amplitude distribution of bipolar voltage pulses

The paper presents the comparative characteristics of the radiation pattern of the combined antenna arrays excited by a bipolar pulse and harmonic oscillations near the central frequency of the spectrum of ultrawideband radiation. Particular attention is paid to the 3x3 array radiation source with maximum efficiency.

A modularized high-power ultra-wideband radiation system based on the space-synthesis method.

In this paper, a high-power ultra-wideband radiation system, composed of multiply radiation modules, is developed based on the space-synthesis method. The radiation module mainly consists of a transistorized pulser, a 2 × 2 combined antenna array, and a power divider. To improve the out parameters [the amplitude, the pulse repetition frequency (PRF), and the rise time] of the transistorized pulser based on the Marx circuit, the influence of the traveling wave process on the output pulse must be concerned. Based on the theoretical analysis, the printed circuit board circuit parameters and the circuit structure of the pulser are optimized. To improve the power synthesis efficiency, the pulse jitter characteristic of the pulser is improved by replacing the conventional base triggering mode with the collector voltage ramp triggering mode for the first-stage avalanche transistor in the pulser. The previous optimized antenna array is utilized in this radiation system, which has a better radiation performance in the prescribed aperture area. In addition, based on the gradient microstrip structure, the power divider integrated with the pulser is designed, which has the advantages of wide bandwidth, low loss, and light weight. Experimental results show that the peak effective potential rEp of the radiation system of 20 radiation modules is 221.8 kV, the maximum PRF could reach 10 kHz, and the half-power radiation angles of its radiation field are about 5° in both the E plane and the H plane. More radiation modules could be integrated into the system to achieve a higher electric field in the future.

Radiation Characteristics of an Offset Reflector Antenna Excited by a Combined Antenna Array

The results of a numerical simulation of an ultrawideband hybrid antenna are presented. The antenna consists of an offset reflector and a 2×2 array of orthogonally arranged combined antennas optimized for excitation by bipolar voltage pulses of duration 0.5 ns at a center frequency of 2 GHz. The antenna is designed for use as a component of a high-power ultrawideband radiation source. The polarization characteristics of the radiation have been studied numerically for two 2-GHz modes. In the first mode, wave beams with linear orthogonal polarizations are sequentially formed. In the second mode, a wave beam with an elliptically polarized field is formed. It has been demonstrated that the radiation peak can be controlled in two mutually perpendicular directions within the width of the pattern.

A portable ultrawideband electromagnetic radiator with a 1.4 MW/50 kHz solid-state subnanosecond pulser.

In this note, a portable ultrawideband (UWB) electromagnetic radiator is developed based on a transistorized pulser with the peak power of 1.4 MW, the rise time less than 150 ps, and the repetition frequency of 50 kHz. To generate high-amplitude pulses, a 100-stage Marx circuit with parallel connection of multiple transistors is proposed. To improve the pulse repetition rate, the parallel charging Marx circuit is adopted with ferrite beads connected in series between stages for high isolation of pulses. In order to radiate the UWB electromagnetic pulse directionally, a compact combined antenna array is fabricated and connected with the pulser via a coaxial feeding module. The effective potential of the UWB radiator reaches 10.5 kV with the band range (-10 dB) from 173 MHz to 2.32 GHz.

Optimizing High-Power Ultra-Wideband Combined Antennas for Maximum Radiation Within Finite Aperture Area

In this paper, the combined antenna array is developed to maximize the effective potential gain (Gep) within finite aperture area for the high-power ultra-wideband (UWB) radiation. The idea is to make the antenna element as small as possible, so that more elements can be arranged within the prescribed aperture area to maximize Gep of the UWB system. On the other hand, the antenna element should match the pulse excitation. This means that in the frequency domain, the working band of the antenna element should cover the spectrum of the radiated pulse, and in the time domain, critical parameters of the radiated field (e.g., rise time of the monopolar pulse) should not be distorted, and those can be the principles for the UWB antenna to match the pulsed excitation, based on which the minimum size of the antenna element can be determined. With this method, a four-element combined antenna array is designed. Also, an impedance transformer and power divider are designed to feed the antenna array. Also, a big combined antenna is developed with the same aperture dimensions (30 cm × 30 cm) as the antenna array. Then, the performances of the antenna array and the big antenna are measured and compared. Compared with the big antenna, G <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ep</sub> of the antenna array is 21% higher under the applied excitation, which indicates that the proposed method can significantly improve G <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ep</sub> of the UWB system within the prescribed aperture area. Finally, the antenna array is furthermore optimized by adjusting the distances between the elements, and Gep is improved by another 11%, the total improvement is 33%, and the corresponding effective potential gain is 1.49.

Ultra-Practical Guide to Ultrawideband [Book\/Software Review

This book contains nine chapters, progressing from an “Introduction to Ultrawideband, Short- Pulse Radio Systems” to “Transmitting, Receiving, and Arrays Antenna Design and Analysis.” It offers a comprehensive treatment of the methods, analysis, and practice of impulse and ultrawideband (UWB) systems and explores UWB sources, antennas, propagation, electromagnetic theory, and practical systems. It also includes practical guidance on how to build antennas and radio hardware for high-power wideband impulse signals and presents both theoretical and experimental results in the time frequency domain. Further, this book explains and discusses the scattering of UWB electromagnetic pulses by conducting and dielectric objects as well as the impulse response of objects; it also includes coverage of the propagation channel. The reader gains insight into the development of the high-power source of UWB radiation with megavolt effective potential on the base of combined antenna arrays. The book has been translated into English from Russian, with many listed references in Russian. This text covers both theory and practical information on UWB short-pulse radio systems. A UWB radio designer can use many of the examples as a starting point to ensure that he or she is beginning on the right foot. Various examples of test data, parameters, and charts can serve as checkpoint comparisons for an original design. Ultrawideband Short- Pulse Radio Systems is an extremely useful guidebook for any radio designer.

Характеристики излучения офсетной отражательной антенны, возбуждаемой решеткой комбинированных антенн

Характеристики излучения офсетной отражательной антенны, возбуждаемой решеткой комбинированных антенн

Synthesis of ultrawideband radiation of combined antenna arrays excited by nanosecond bipolar voltage pulses

To broaden the spectrum of high-power ultrawideband radiation, it is suggested to synthesize an electromagnetic pulse summing the pulses of different length in free space. On the example of model pulses corresponding to radiation of combined antennas excited by bipolar voltage pulses of the length of 2 and 3 ns, the possibility of twofold broadening of the radiation spectrum was demonstrated. Radiation pulses with the spectrum width exceeding three octaves were obtained. Pattern formation by the arrays of different geometry excited by the pulses having different time shifts was considered. Optimum array structure with the pattern maximum in the main direction was demonstrated on the example of a 2×2 array.

Analysis of a Combined Antenna Arrays and Reverse-Link Synchronous DS-CDMA System over Multipath Rician Fading Channels

We present the BER analysis of antenna array (AA) receiver in reverse-link asynchronous multipath Rician channels and analyze the performance of an improved AA system which applies a reverse-link synchronous transmission technique (RLSTT) in order to effectively make a better estimation of covariance matrices at a beamformer-RAKE receiver. In this work, we provide a comprehensive analysis of user capacity which reflects several important factors such as the ratio of the specular component power to the Rayleigh fading power, the shape of multipath intensity profile, and the number of antennas. Theoretical analysis demonstrates that for the case of a strong specular path's power or for a high decay factor, the employment of RLSTT along with AA has the potential of improving the achievable capacity by an order of magnitude.

A Combined Antenna Arrays and Reverse-Link Synchronous DS-CDMA System over Frequency-Selective Fading Channels with Power Control Error

An improved antenna array (AA) has been introduced, in which reverse-link synchronous transmission technique (RLSTT) is incorporated to effectively make better an estimation of covariance matrices at a beamformer-RAKE receiver. While RLSTT is effective in the first finger at the RAKE receiver in order to reject multiple-access interference (MAI), the beamformer estimates the desired user's complex weights, enhancing its signal and reducing cochannel interference (CCI) from the other directions. In this work, it is attempted to provide a comprehensive analysis of user capacity which reflects several important factors such as the shape of multipath intensity profile (MIP), the number of antennas, and power control error (PCE). Theoretical analysis, confirmed by the simulations, demonstrates that the orthogonality provided by employing RLSTT along with AA may make the DS-CDMA system insensitive to the PCE even with fewer numbers of antennas.

A Combined Antenna Array and Multi-User Detection DS-CDMA Receiver inSingle-Path and Multi-Path Fading Channels

An adaptive antenna array is incorporated into a decorrelating multi-user detector to effectively increase the DS-CDMA system capacity. Capacity improvement is due to beamforming gain, spatial diversity gain (assuming large angle spread), and the decorrelating effect. The receiver has been analyzed for the cases of sufficiently and insufficiently spaced receiving antennas. The receiver consists of a front-end beamformer for every user in the cell and has knowledge of all users' signature sequences. The beamformer estimates the desired user channel vector, enhancing its signal and reducing the co-channel interference from other directions. The multi-user detection, exploiting knowledge of other users, rejects those interferers whose arrival angles are close to that of the desired user. The average uncoded Bit Error Rate (BER) as a function of the number of in-beam active users, the average antenna Signal-to-Noise Ratio (SNR), and the number of receiving antennas is examined in both single-path and multi-path Rayleigh fading channels. Analysis shows an increase in system capacity proportional to the number of receiving antennas.

A low-complexity combined antenna array and interference cancellation DS-CDMA receiver in multipath fading channels

A simple direct sequence-code division multiple access receiver that combines adaptive beamforming with parallel interference cancellation in a multipath fading channel is proposed and analyzed. A fast adaptation, conjugate gradient algorithm is used to find the optimum beamformer weights. By beamforming, the desired user's signal is enhanced and the cochannel interference from other directions is reduced. For in-beam multiple access interference reduction, a parallel interference canceller is used in each RAKE finger. In the demodulation process, we propose a new demodulation method in which the incoming signal is correlated with the effecting spreading code rather than the physical spreading code called the effective matched filter. A new combining method called equivalent maximal ratio combining is also proposed and analyzed. The average uncoded bit error rate as a function of the average antenna signal-to-noise ratio and the number of receiving antennas is examined in a frequency selective Rayleigh fading channel for all proposed receiver structures. Both simulation and analysis show an increase in system capacity as a function of the number of antennas and the number of interferers canceled per finger.