Compact Circularly Polarized Patch Antenna Using a Composite Right/Left-Handed Transmission Line Unit-Cell

A compact circularly polarized (CP) patch antenna using a composite right/left-handed (CRLH) transmission line (TL) unit-cell is proposed. The CRLH TL unit-cell includes a complementary split ring resonator (CSRR) for shunt inductance and a gap loaded with a circular-shaped slot for series capacitance. The CSRR can decrease the TM10 mode resonance frequency, thus reducing the electrical size of the proposed antenna. In addition, the asymmetry of the CSRR brings about the TM01 mode, which can be combined with the TM10 mode by changing the slot radius. The combination of these two orthogonal modes with 90° phase shift makes the proposed antenna provide a CP property. The experimental results show that the proposed antenna has a wider axial ratio bandwidth and a smaller electrical size than the reported CP antennas. Moreover, the proposed antenna is designed without impedance transformer, 90° phase shift, dual feed and ground via

Structural behaviour of beam with HDPE plastic balls subjected to flexure load

This paper presents the structural behavior of reinforced concrete beam embedded with high density polyethylene balls (HDPE) subjected to flexural load. The HDPE balls with 180 mm diameter were embedded to create the spherical voids in the beam which lead to reduction in its self-weight. Two beam specimens with HDPE balls (RC-HDPE) and one solid beam (RC-S) with dimension 250 mm x 300 mm x 1100 mm were cast and tested until failure. The results are analysed in the context of its ultimate load, load-deflection profile, and crack pattern and failure mode. It was found that the ultimate load of RC-HDPE was reduced by 32% compared to RC-S beam while the maximum deflection at its mid span was increased by 4%. However, RC-HDPE is noticed to be more ductile compared to RC-S beam. Both types of beams experienced flexure cracks and diagonal tension cracks before failur

An improved 2×2 array antenna using both-sided microwave integrated circuit technology for circular polarization

A circularly polarized microstrip patch array antenna using both-sided microwave integrated circuit (MIC) technology with a triple feed network has been proposed in this article. The antenna elements, feed structure and both-sided MIC technology are used and arranged in such a way to obtain circular polarization alongside high gain without using an external matching circuit. The 50 Ω microstrip line is used to energize the antenna where the antenna’s total feed network is made up of both series and parallel combinations of microstrip and slot line. The antenna was realized using Teflon glass fiber substrate (εr)=2.15 with a thickness of 0.8 mm. The antenna has some splendid parameters including S11 of less than -35 dB, a gain of 12 dBi with an omnidirectional pattern and an axial ratio of 0.7 dB at the operating frequency. The antenna possesses a bandwidth of 430 MHz (4.22%) after operating at X-band in the frequency spectrum. The antenna’s simulated parameters were investigated with the help of advanced design system (ADS) simulation software in microwave momentum mode

Antenna Array Designs For Directional Wireless Communicatoin

Ph.D. Thesis. University of Hawaiʻi at Mānoa 2018

Dual-band Omnidirectional Circularly Polarized Antenna

A dual-band omnidirectional circularly polarized antenna is proposed. The antenna comprises back-to-back microstrip patches fed by a coplanar waveguide. A very low frequency ratio of 1.182 has been achieved, which can be easily tuned by adjusting four lumped capacitors incorporated into the antenna. An analysis of the omnidirectional circular polarization mechanism as well the dual band operation is provided and confirmed by numerical and experimental data. Key parameters to tune the resonant frequencies and the axial ratio have been identified. The prototype antenna provides omnidirectional circular polarization in one plane with cross polar isolation better than 12 dB for both frequency bands

A comprehensive survey on 'circular polarized antennas' for existing and emerging wireless communication technologies

Circular polarized (CP) antennas are well suited for long-distance transmission attainment. In order to be adaptable for beyond 5G communication, a detailed and systematic investigation of their important conventional features is required for expected enhancements. The existing designs employing millimeter wave, microwave, and ultra-wideband (UWB) frequencies form the elementary platform for future studies. The 3.4-3.8 GHz frequency band has been identified as a worthy candidate for 5G communications because of spectrum availability. This band comes under UWB frequencies (3.1-10.6 GHz). In this survey, a review of CP antennas in the selected areas to improve the understanding of early-stage researchers specially experienced antenna designers has presented for the first time as best of our knowledge. Design implementations involving size, axial ratio, efficiency, and gain improvements are covered in detail. Besides that, various design approaches to realize CP antennas including (a) printed CP antennas based on parasitic or slotted elements, (b) dielectric resonator CP antennas, (c) reconfigurable CP antennas, (d) substrate integrated waveguide CP antennas, (e) fractal CP antennas, (f) hybrid techniques CP antennas, and (g) 3D printing CP antennas with single and multiple feeding structures have investigated and analyzed. The aim of this work is to provide necessary guidance for the selection of CP antenna geometries in terms of the required dimensions, available bandwidth, gain, and useful materials for the integration and realization in future communication systems

Reconfigurable microstrip antennas with tunable radiation pattern characteristics

Reconfigurable beam antenna systems are capable of changing their radiation characteristics in real time, such as beam direction, beam shape, beamwidth, etc. Such antenna system is desired for various wireless applications because of many reasons among them; it helps to enhance signal strength received from an intended target, mitigates interference, and accommodates sudden changes in traffic demand of wireless networks. It might also help to reduce the deployment cost of wireless networks infrastructures. In this dissertation, designs for reconfigurable beam microstrip antennas with tunable radiation characteristics have been proposed. The method to achieve these designs is the reconfigurable parasitic element (s) of tunable electrical size, placed in close proximity to the driven patch. A tuning mechanism with the aid of Varactor diodes is introduced for the parasitic patch that effectively allows for controlling its electrical size. This (these) reconfigurable parasitic patch (es) is (are) then applied in different fashions to devise several antenna designs with dynamic electronic control over certain radiation specifications. The accomplished antenna designs in the dissertation are: * Circularly polarized (CP) beam scanning antenna, where two elements microstrip Yagi-Uda antenna is used. The first element is a square patch driven with two probe feeds of quadrature phase for CP excitation. The second element is a parasitic square patch with narrow square-shaped slot carved on its surface. The parasitic patch is adjacent to the driven patch with a small separation distance. Four varactor diodes are placed on the middle of each side of the square slot to facilitate tuning of its electrical size. The parasitic patch electrical size is alloto be effectively tuned by varying the applied reverse biasing DC voltage to the varactors (capacitance value). The CP beam direction is scanned from -36° to 32° with gain variation from 5.7 to 8.2 dBic, and efficiency from 54% to 75.58% along the scanning range. * Two-dimensional beam scanning antenna, where two orthogonal crossed Yagi-Uda antenna configuration is utilized. The driven element is a square patch excited with a probe coaxial feed. The other two parasitic patches are closely placed along the E & H planes of the driven patch. Each parasitic patch has a narrow rectangular slit at its center, where a varactor diode is placed to allow for tuning its electrical size. The beam direction is permitted to be scanned in both the elevation and azimuth planes. The achieved scan range in the elevation plane is from 0° to 32°, whereas in azimuth plan is from 0° to 90°. Along the scanning range, the attained gain changes from 8.1 to 8.9 dBi, and efficiency changes from 86% to 93%. * Tunable beamwidth antenna, with a dynamic control over the radiation beam focusing is proposed. The antenna consists of a square patch excited by a coaxial probe feed, and other two square parasitic patches placed on both sides of the driven along its H-plane. Each parasitic patch has a narrow slit at its center loaded with lumped varactor diode to tune its electrical size. Upon changing the parasitic patches size, the antenna effective aperture is altered, and hence the beamwidth in the H-plane is controlled. The achieved beamwidth tuning range is from 52° to 108°, whereas the gain changes from 6.5 to 8.1 dBi. Throughout the dissertation, 2.45 GHz is chosen, as an example, to be the target frequency. All the designs are validated through experimental measurements for fabricated prototypes, and good agreement is observed between the predicted and measured results