A Twelve-Beam Steering Low Profile Patch Antenna with Shorting Vias for Vehicular Applications

A low-profile twelve-beam printed patch antenna is presented for pattern reconfigurable applications. The patch is fed at the four sides using coaxial feeds. Diagonal lines of vias are inserted on the patch surface to restrict currents to the edges. Whilst majority of patch antennas have only axial beam pattern, the proposed antenna produces twelve different beams. When one of its four feeds on the sides is excited and the remaining feeds are open circuited, the antenna generates a linearly polarized tilted beam (6.1 dBi, θmax = 30°). This beam is directed away from feeding patch corner. Therefore, the antenna can steer its tilted beam in four different space quadrants in front of the antenna by exciting one feed at a time. The antenna is also capable of generating eight other beams using multiple feed excitations. They are four additional titled beams (6.1 dBi, θmax=30°), two tilted-twin beam (5.8 dBi, θmax=±36°), one semi-doughnut beam (5.8 dBi) and one axial beam (8.2 dBi). The antenna is designed to operate at test frequency of 2.4 GHz and has a height = 1.5 mm (λ0/83). The impedance matching to 50 Ω is achieved using right angle slots etched on the patch antenna

2 x 2 Phased Array Consisting of Square Loop Antennas for High Gain Wide Angle Scanning With Low Grating Lobes

A 2 × 2 array antenna comprised of conventional hybrid high impedance surface-based reconfigurable square loop antennas (SLAs) as elements is presented. The SLA element has four conducting arms and each arm is fed at the middle by vertical probes, which is connected to a 50 Ω port at the bottom of antenna ground plane. Thus, the SLA element has four feeding ports and it is capable of generating five distinct radiation patterns by using a combination of its feeding ports. Depending upon which of its four ports are excited it can provide four high gain off-boresight tilted beams (8.9 dBi at θmax= 36°) in four different quadrants of the space (tilted beam mode). When all the four ports are simultaneously excited with phases of 0°, 0°, 180°, and 180°, it provides an axial beam (6.5 dBi) at boresight (axial beam mode). By combining these two modes the 2 × 2 array of SLAs can provide a scanning range of-60° to +60° in the elevation plane with high-gain beams (14-11.2 dBi)

Conformal Beam-steering Antenna Controlled by a Raspberry Pi for Sustained High Throughput Applications

A complete autonomous system consisting of a beam steerable Hemispherical Square Loop Antenna (HSLA) controlled by a Raspberry Pi is presented for optimizing the throughput in a scattered and a poor Signal to Noise Ratio (SNR) environment. A total of four different indoor communication configurations at various distances were analyzed in presence of interferences. In three configurations HSLA performance was also compared to that of a standard monopole antenna link. It was found HSLA can offer up to 1450 % higher throughput and can withstand much higher interference levels before the system breaks. In terms of quality this means sustaining compressed HD communications. In effect, it improves the system throughput for the test 2.4 GHz (802.11b/g/n) WiFi band. The uniqueness about the system is that it only uses single antenna for both sensing and communication. The algorithm works at application layer that controls the RF switch and antenna patterns at physical layer. Thus, the entire middle protocol layers are untouched. The system can easily be retrofitted to existing non-adaptive communication systems

Effective dielectric constant of top grounded coplanar waveguide on liquid crystal superstrate

AbstractThe effective dielectric constant of the top grounded coplanar waveguide with a liquid crystal (LC) superstrate for phase shifting applications is investigated in the frequency range of 30–60 GHz. Two nematic LC mixtures, namely E7 and MDA‐00‐3506, are used as the superstrate. The measurements show that MDA‐00‐3506 offers higher values of phase shift per millimeter than its E7 counterpart. In particular, the MDA‐00‐3506 provides 3.14°/mm, whereas E7 gives 2.79°/mm at 60 GHz. The results of the dielectric constants from measurement and computer modeling are found to agree to within 5%. For the modeling, a comprehensive finite element package predicting the local alignment of LC molecules and effective dielectric constant at different bias voltages and frequencies are used. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1416–1418, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27564</jats:p

Accurate modelling for the analysis and design of liquid-crystal-based microwave devices

Liquid crystal substrates have been shown to provide the means to develop low-cost, reconfigurable, adaptive and tuneable microwave and MM-wave devices for mobile and wireless communication systems. However, techniques for the characterisation of materials, device fabrication and design are necessary in order to take maximum advantage of the possibilities that these materials offer. This includes appropriate modelling methods to simulate accurately the switching behaviour of the liquid crystal and the characteristics of the wave propagation through the devices, taking full consideration of the point-by-point variation of the material tensor permittivity. We describe these techniques here and show their application in the design of a meander-line phase shifter

Analysis of Microstrip Patch Antennas for Dielectric Measurement

The microstrip patch antenna has been employed by Shimin [1] to measure the dielectric constant of thin slab materials. Although the applicability of the method in [1] is not restricted by the size of the material under test, the etching of the patch and the introduction of the ground plane on the material cannot be practical in many cases. A more practical approach based on the microstrip antenna is reported in [2] for the measurement of the dielectric constant of snow. The technique employs the antenna as an applicator. The antenna is brought to the close proximity or in contact with the surface of the material in order to cause interaction between the antenna’s near field and the object. The result is a change in the input impedance and the resonant frequency of the antenna. Similar to short antenna applicators [3], a patch antenna applicator can take measurements under resonant and off resonant conditions. However, at resonance, achieving accurate measurements are straight-forward. The technique can be applied to solids as well as to liquids with small or large losses. It can also be used in the thickness measurement of layered materials

Microstrip Device for Broadband (15–65 GHz) Measurement of Dielectric Properties of Nematic Liquid Crystals

The essential dielectric properties, the basic alignment techniques, and the common measurement methods of the nematic liquid crystal (LC) at RF are briefly reviewed. A new device for the broadband measurement of the dielectric constants and loss tangents of nematic LCs at microwave and millimeter-wave frequencies is presented. This device whose specification and fabrication are outlined is essentially a two dielectric layer microstrip structure with coplanar-waveguide terminals, which is easy to fabricate. Compared to previous structures, the proposed device is extremely broadband with 15-65-GHz bandwidth, benefits from a solid exposed ground plane for easy temperature test, and operates under bias voltage. The technique for the extraction of the dielectric parameters of the nematic LC analyzed by this device is explained and the sources imposing the frequency limits on the device performance are identified. Two different nematic LCs, MDA-00-3506 and GT3-23001, are characterized and the results are shown to compare well with those available in the literature. In the comparisons, the maximum difference found for the dielectric constants for MDA-00-3506 is 5% and for GT3-23001 is 5.3%

Separated Microstrip Antenna for Satellite Simulators

Microstrip patch antenna have been designed for satellite simulator system for transceiver antenna. The transmitter antenna is designed for the uplink at 14.25 GHz and receiver antenna is designed for the downlink at 11.45 GHz. The transmitter and receiver antennas are designed on a single substrate with microstrip transmission feedline on two sides for each frequency band. Quarter-wavelength structure is used for matching. Simulation results reveal a broadband structure for reflection, with a gain of 7 dB and high efficiency

Mathematical Modeling of the Interaction of Non-Uniform Field ACFM with Finite Size Cracks

The non-destructive evaluation (NDE) of metal surfaces can be accomplished using the alternating current field measurement (ACFM) technique [1]. In this technique a thin-skin eddy current is induced in the metal and the magnetic field above the metal surface is monitored for any perturbation caused by surface defects. In the non-uniform ACFM, the incident field may be produced by a coil or a wire loop carrying a high frequency current [2].</p