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

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

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

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

Crack Signal Saturation in High Sensitivity ACFM Technique

Recently, we proposed the high sensitivity ac field measurement (ACFM) technique for detecting and sizing surface cracks in metals [1–2]. This non-destructive evaluation (NDE) technique requires an inducer which possesses a field region with odd symmetry for positioning the probe. When properly orientated in this field region, a single linear probe acts as a differential probe with the added advantage of a phase contribution due to the crack. Both a rectangular coil and a rhombic wire loop can be used as inducers to provide the necessary field. In Fig.1, the positions of the probe with respect to these inducers are shown. As can be inferred from this figure, the probe is coupled to the magnetic field tangent to the metal surface

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

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)

EBG enhanced broadband dual antenna configuration for passive self-interference suppression in full-duplex communications

A full-duplex system is realised using dual EBG isolated rectangular spiral antennas and its performance is compared with the same full-duplex system using a circulator and a single spiral antenna element. The new antenna system consists of two antennas one with RHCP and the another one with LHCP implemented on a single substrate. Two columns of EBG is placed between the two antennas to improve the isolation. At the operating frequency of 3.2 GHz, the antenna configuration has nearly 31 dB isolation. For the identical baseband input power, the full-duplex system utilising dual spiral antenna configuration exhibits 9 dB higher isolation than the circulator based full-duplex system

Slot Resonators for Characterization of Dielectrics at Microwave Frequencies

Open planar resonators like single and stacked microstrip resonators were used in the past for the measurement of dielectric constants and thicknesses of lossy and lossless dielectrics at microwave frequencies [1–3]. With a large width, the microstrip resonator effectively acts as a planar antenna in which case the fringing field is significant for the two slots at the two ends of the resonator and the resonator Q-factor is low. One of the limitations of the microstrip resonator is its spatial resolution which is determined by the size of the resonator. It is envisaged that this problem can be overcome by the use of planar slot resonators, Fig.1. Furthermore, compared to the microstrip-fed microstrip resonator, a microstrip-fed planar slot resonator would provide a better isolation between the feed and the material under test