Reflective array antenna

About: Reflective array antenna is a research topic. Over the lifetime, 4366 publications have been published within this topic receiving 57884 citations.

Compact antenna array receiver for robust satellite navigation systems

Abstract: A compact navigation receiver comprising a decoupled and matched four-element L1-band antenna array with an inter-element separation of a quarter of the free-space wavelength is presented in this paper. We investigate the impact of the decoupling and matching network on the robustness of the navigation receiver. It is observed that in order to achieve high robustness with a compact antenna array, it is necessary to employ a decoupling and matching network, particularly in case of three spatially separated interferers. Furthermore, we study the influence of the polarization impurity of the compact planar antenna array on the equivalent carrier-to-interference-plus-noise ratio (CINR) of the receiver when impinged with different numbers of diametrically polarized interference signals. It is shown that the higher-order modes possess strong polarization impurity, which may halve the available degrees-of-freedom for nulling in the presence of linear-polarized interferers, using a conventional null-steering algorithm. We verify the robustness of the designed compact receiver by means of a complete global-navigation-satellite-system demonstrator. It is shown that the maximum jammer power that is allowed us to maintain the CINR above 38 dBHz with three interferers can be improved by more than 10 dB if a decoupling and matching network is employed.

Signal correlations in coupled cell and MIMO antennas

Abstract: Introduction Keeping signal correlation low across antennas is critical for good receive diversity in cell communications, and for creating independent transmission channels in high data rate MIMO (multiple-input multiple-output) techniques. Tools to achieve this are particularly important when trying to pack multiple antennas into small mobile terminals. Analyses of signal correlations for these applications usually neglect mutual antenna coupling. This paper presents precise formulas for the correlation between signals in mutually coupled antennas, for both 2D and 3D diffusive propagation environments. New values of optimal antenna spacing are given, and closely spaced antennas are predicted to work much better than previously expected.

Step-scanned circular-array antenna

Abstract: A circular-array radar antenna designed for operation over a 20-percent bandwidth has demonstrated improved performance over that of linear arrays. A major advantage is that the beam pointing angle is independent of frequency. The array developed and tested provides 128 beam positions with a beam crossover of about -2 dB, a half-power beamwidth on the order of 4 or 5 degrees, and a sidelobe level of -25 dB. Step increments of one element per beam position allow practical implementation of step scanning, i.e., simple commutation of the current distribution. Two approaches are possible for feeding and scanning the ring array: 1) a vector-transfer system involving 3-bit phase and amplitude boards which are capable of amplitude attenuation (VT scan) and 2) a lens feed system employing an R-2R parallel-plate region, with the spacing between the plates less than 1/2 a free-space wavelength, so that only the electric-field component perpendicular to the plates is propagated. Energy is launched and extracted from the lens by means of monopoles mounted 1/4 wavelength in front of the circumferential ground plane enclosing the lens. Computations involved in determining current distribution are based on [1] and [2].

Spatio-temporal coding for radar array processing

Abstract: The aim of this paper is to present a new method allowing radar digital beamforming (DBF) with only one receiver channel. The key point is the use of a particular spatio-temporal waveform transmitted by an active phased array antenna. By properly choosing the temporal modulation applied on each of the transmission elements, one can transmit different signals in different directions, allowing (under certain hypotheses) angular localisation with only one receiver channel. The major advantage is the design of a low cost system providing DBF capabilities.

Integrated Broadband Bowtie Antenna on Transparent Silica Substrate

Abstract: The bowtie antenna is a topic of growing interest in recent years. In this letter, we design, fabricate, and characterize a modified gold bowtie antenna integrated on a transparent silica substrate. The bowtie antenna is designed with broad RF bandwidth to cover the X-band in the electromagnetic spectrum. We numerically investigate the antenna characteristics, specifically its resonant frequency and enhancement factor. Our designed bowtie antenna provides a strong broadband electric field enhancement in its feed gap. Taking advantage of the low-k silica substrate, high enhancement factor can be achieved without the unwanted reflection and scattering from the backside silicon handle, which is the issue of using a silicon-on-insulator (SOI) substrate. We simulate the dependence of resonance frequency on bowtie geometry, and verify the simulation results through experimental investigation, by fabricating different sets of bowtie antennas on silica substrates and then measuring their resonance frequencies. In addition, the far-field radiation pattern of the bowtie antenna is measured, and it shows dipole-like characteristics with large beamwidth. Such a broadband antenna will be useful for a myriad of applications, ranging from photonic electromagnetic wave sensing to wireless communications.