Antenna arrays

This communication presents a novel technique for the analysis and design of complex antennas, including reflectoarrays and antennas composed by metamaterials and other finite-sized multilayered quasi-periodic structures. This method is based on the Method of Moments, and the combination of the Multilevel Fast Multipole Algorithm (MLFMA) [1] and the Characteristics Basis Function Method (CBFM) [2] has been applied to reduce the computational cost. The method has been tested considering several periodic structures achieving good results.

The aim of this paper is to introduce and use the
spider monkey optimization (SMO) as an optimization technique
for the electromagnetics and antenna community. The SMO is a
new swarm intelligence technique which models the foraging
behavior of spider monkeys. To show the efficiency of the SMO,
different examples are presented and the results are compared
with the results obtained using other popular optimization
techniques. The optimization procedure is used to synthesis the
array factor of a linear antenna array and to optimally design an
E-shaped patch antenna for wireless applications. By comparing
to traditional optimization techniques that reported in the
literature, it is evident that SMO is efficient in reaching the
optimum solutions with less number of experiments.

A miniaturized ultra wideband (UWB) planar array antennas for C-band aircraft weather RADAR applications is presented. Firstly, the effect of the ground plane is studied. Later, the realization and experimental validation of the geometry that has an UWB characteristic are discussed. This array antennas is composed of a twenty-four radiating element that is etched onto FR-4 substrate with an overall size of 162 × 100 × 1 58 mm 3 and a dielectric constant of ε r = 4 4. The results show that this miniaturized array antennas gives us a bandwidth which is about 115% and a gain greater than 13 dB which are required in aircraft weather radar applications.

Теоретически и экспериментально проведено исследование согласования и характеристик излучения сверхширокополосных излучателей на основе ТЕМ рупора, в том числе новых типов, для кольцевых антенных решеток. Теоретические результаты получены путем электродинамического моделирования на основе метода конечных элементов и метода конечных разностей во временной области.

This article covers the basic principles of true-time-delay (TTD)-based space-time array processors and ultra-wideband beamformers. General considerations regarding the need for TTD array processing, optimum array size, antenna spacing, and array patterns are discussed for communication and imaging UWB arrays. Several recent integrated circuit implementations of UWB TTD-based beamformers are presented. A few commercial applications that warrant UWB TTD-based array processing, with emphasis on imaging and sensing, are also described.

The performance of an isolated antenna compared with itself but embedded (in-situ) in an array is not the same mostly due to the influence of mutual coupling and electromagnetic diffraction. Although signal processing techniques have been widely spread in literature for antenna arrays of elements with same physical properties and same performance, there is not enough mention regarding antennas with dissimilar behaviors. The usual way of avoiding this problem is by means of some kind of compensation that can reduce the differences but not always eliminate them, unless the information of the active radiation pattern of the antennas in array and wideband compensation techniques are used. A great advantage of employing adaptive methods for processing with antenna arrays is that it ensures good performance even without requiring this complete information. However, the distortions incorporated to the acquired signals by such processing step added to the improper characterization of the antenna array degrades the precision of the received signal parameters measurements. In this paper we analyze the need of using compensation techniques in GNSS applications when the performance of the array of antennas is properly characterized. The degrading effects of using adaptive antenna arrays on acquired GNSS signals and how to avoid them are also evaluated. Simulated results that involve an array of microstrip antennas for GNSS are presented.

In this paper, a high gain narrow band array of rectangular microstrip patch antennae is proposed. Every array element is rectangular in shape. FR-4 and Rogers-3006 material with dielectric constant 4.4 and 6.51, loss tangent of 0.002 and height 1mm have been used as substrates. Microstrip lines are used as feed lines to substrate. The proposed design of 8x1 patch array antenna using ROGERS-3006, gives better results in comparison with FR-4 in microwave application. The operating frequency is considered as 10 GHz. The patch array has been targeted for the application as sensor, where high gain, narrow bandwidth and higher directivity is needed, which are simulated and compared in the proposed research.

ABSTRACT A synthetic overview of the fascinating topic of phased array antennas for satellite communications is presented. A system engineering approach to the design and development of phased arrays is shown to be essential in order to achieve an effective and synergic design and to implement large-scale production techniques. It is the author's firm opinion that a broadband technical background and an open, “lateral thinking” mentality are key factors for the successful design, development and production of active phased arrays

The Indian regional navigational satellite system
(IRNSS) is an autonomous regional satellite navigation system
being developed by the Indian Space Research Organization
(ISRO) which would be under complete control of the Indian
Government. The requirement of such a navigation system is
driven by the fact that access to Global Navigation Satellite
System, GPS is not guaranteed in hostile situations. Design of
IRNSS antenna at user segment is mandatory. The simulated
Microstrip patch antenna operates on the frequency of L5 band
(1176.45 MHz) which is used for positioning services. Its
parameters are enhanced by making 2x8 array with Teflon
substrate, increasing gain, directivity, and efficiency to 17.3dB,
18.1dBi and 95.58% respectively. For fabrication purpose
substrate FR4 substrate can be used for which 10.1dB gain and
15.4dBi directivity is obtained till 2x8 array. Results of
simulation are compared with hardware results using Vector
network analyzer for two models of all array.

The technique of interpolated arrays is applied to ESPRIT-type direction finding methods. The resulting method uses sensor arrays with an arbitrary configuration, thus eliminating the basic restrictive requirement of ESPRIT for two (or more) identical arrays. This approach allows for resolving D+1, while the original ESPRIT method requires at least 2D sensors. Moreover, it is shown that while ESPRIT performs poorly for signals propagating in parallel (or close to parallel) with the array displacement vector, the advocated technique does not exhibit such weakness. Finally, using two subarrays, ESPRIT cannot resolve azimuth and elevation even when the sensors are not collinear. However, the interpolated ESPRIT procedure resolves azimuth and elevation using only a single array. The performance of the original ESPRIT when the sensor locations are perturbed is also discussed and illustrated numerically

International Journal of Antennas is a peer-reviewed, open access journal that publishes original research as well as review articles in the field of antennas and its allied domain. This journal aims to bring together leading academic scientists, researchers, engineers and research scholars to exchange and share their experiences and research results in their specialized arena in antenna engineering. The journal invites good quality research and review papers for publications.

Modern radar systems often have the conflicting requirements of a large phased array antenna for increased power-aperture product and/or angular resolution versus wide instantaneous signal bandwidth for fine range resolution. Pulse-to-pulse diversity may also be desired as a countermeasure against coherent repeater jammers. Using the multicarrier nature of orthogonal frequency-division multiplexing to encode wide instantaneous bandwidth pulses we propose a novel digital phased array architecture which mitigates dispersion effects experienced when the array main beam is electronically steered off broadside. The result is the ability to transmit and receive wideband pseudo-random phase coded pulses with a phased array antenna. Simulation results are used to quantify the benefit of the architecture. An overview of digital orthogonal frequency-division multiplexing waveform generation is also provided.

SIR-C/X-SAR, a three-frequency radar to be flown on the Space Shuttle in September 1993, is described. The SIR-C system is a two-frequency radar operating at 1250 MHz (L-band) and 5300 MHz (C-band), and is designed to get four-polarization radar imagery at multiple surface angles. The X-SAR system is an X-band imaging radar operating at 9600 MHz. The discussion covers the mission concept; system design; hardware; RF electronics; digital electronics; command, timing, and telemetry; and testing.

This paper describes recent work on the topic of multi-dimensional (MD) spatio-temporal noise and distortion shaping for radio-frequency (RF) antenna arrays with applications in wireless communications, phased-array radar sensing, microwave/mm-wave imaging, and radio astronomy instrumentation. The MD spectral properties of propagating plane-waves that arise from electromagnetics are combined with MD circuits and signal processing theory based on passive resistive terminated 2-D filters. The result, for the first time in the literature, is MD multi-port extensions of the analog and digital electronics found within wireless transceivers, including RF amplifiers, mixers, and data converters. In particular, a multi-port extension of conventional analog-to-digital converters (ADCs) is proposed in which the distortion that is generated from non-linear operations (such as quantization) is spectrally shaped in multiple spatio-temporal dimensions such that the region of support (ROS) of the desired RF signals corresponding to desired planar waves is ideally mutually exclusive with that of these undesired components. Because of spectral shaping, both distortion and noise are non-overlapping with the signal of interest and can be filtered out after sampling by using an MD digital filter. This theoretical advance in MD noise and distortion shaping across both space and time domains ensures that both electronic noise and non-linear distortion arising from coarse low-complexity quantization do not appreciably reduce the signal to noise and distortion ratio (SNDR) of antenna array receivers. The proposed method is an extension of ∆ − Σ modulation that is commonly used in conventional single-input single-output ADCs but does not require either temporal or spatial over-sampling. Moreover, to the best of our knowledge this paper is the first to combine 2-D analog filters derived from resistively-terminated classical passive low-pass filter prototypes with active analog feedback control in multiple dimensions (space, time) to realize 2-D analog-digital mixed-signal electronics for RF array processing applications.