circularly-polarized antenna is built based on new SIW(substrate integrated waveguide) structure which contains cavity-backed resonator and a conventional polarized ring with two square slits in inner and outer ring that differ 90° at position and is proposed for right-handed circular polarization (RHCP) and fabricated in two separate layers. A broadband impedance bandwidth of 13.9% and a RHCP axial ratio of 0.5GHz have been obtained under the condition of less than VSWR ≤2 and axial ratio≤ 3 dB, respectively.

In In this paper, two low profile, single fed cavity backed slot antennas providing a circularly polarized (CP) wave are introduced. One of the antennas presents a right-handed CP (RHCP) wave, while the other one offers a left handed CP (LHCP) wave. The proposed antennas consist of a square shaped Substrtae Integrated Waveguide (SIW) cavity incorporatng two couples of radiating slots to radiate two field components with 90 phase difference far from the antennas. A single layer of printed circuit board (PCB) process is employed for both antennas to provide low cost, light weight and also to be compatible with planar circuits. An inset feed line is used to excite two orthogonal modes including TE120 and TE210 with suitable phase difference for generating CP wave. Antenna structures is numerically evaluated using High Frquency Structure Simulator (HFSS) and a prototype of RHCP antenna is fabricated and its radiation charateristics including reflection coefficient, gain, Axial Ratio (AR) and radiation patterns are reported.

Background and Objectives: Microstrip patch antennas are widely used due to their advantages of compact size and easy fabrication compared to other types. However, they have low-performance parameters. As a result, several techniques are used to improve performance parameters in newly designed microstrip antennas. In this study, a novel miniaturized microstrip antenna with circular polarization (CP) is proposed for GNSS applications.Methods: In the design process, the semi-fractal structure is used to reduce the antenna size. Circular polarization is generated using a three-feed configuration with 120◦ phase shift. The CP value is increased by use of perturbing slots and also removing the corners. The novel design of the feeding network and also considering the ground size same as the patch layer, keep the antenna size small. The co-axial probe is used in the feeding network and it is printed on Taconic RF-43 substrate with a low loss tangent of 0.0033. Numerical simulation is applied via CST commercial software to evaluate the antenna performance. The simulations are repeated in two other software, HFSS and FEKO, to validate the study. Results: The proposed antenna has a compact size of 17.56 cm2. The single-layer structure of the designed antenna leads to easy fabrication feature. The proposed antenna has a bandwidth of 55 MHz (1.558-1.614 GHz). It can operate at GPS L1 (1575 MHz), GLONASS G1 (1602 MHz), Galileo E1 (1589 MHz), and E2 (1561 MHz) bands. Results show a high front-to-back ratio (FBR) of 40 dB, RHCP gain of 3.45 dB, and pure CP with axial ratio (AR) beamwidth of 108⸰. Furthermore, the phase center variation (PCV) is less than 0.16 mm.Conclusion: Key features of the proposed antenna are its novel fractal structure that leads to compact size, high front-to-back ratio, wide RHCP beamwidth with desirable bandwidth, and axial ratio beamwidth.

This paper presents an element of a 2×2-element array antenna for Inmarsat BGAN/GPS applications. The element is an axial mode printed quadrifilar helical antenna that has been integrated with a compact feed network to provide sequential phase rotation for circular polarization (CP) radiation. The novel integrated lumped-element feed network is designed to provide a balanced RF power to the four helix arms with a 90° sequential phase difference between them. The design maintains a low cross polarization, and accordingly, a high quality of RHCP up to ± 66° over the transmit frequency band of 1616 MHz to 1626 MHz. The gain in this frequency range is higher than 3. 5 dB with a return loss better than 11 dB and a perfect circular polarization performance (axial ratio ~0 dB). The proposed antenna has small size, light weight, low cost, almost hemispherical radiation pattern and excellent circular polarization that can become a good candidate in satellite L1-band and BGAN satellite communications.

Metasurfaces are two-dimensional artificial structures which have extraordinary electromagnetic properties. They have been used in myriad of devices such as nano-antennas, cloaking coatings, imaging devices, flat lenses, and polarization converters over a wide range of frequency. Due to high dependency of many devices on incident wave polarization, manipulating the polarization of electromagnetic waves would be useful, especially in the THz regime. In this study, we propose a linear to circular polarization converter (LTC-PC) based on a THz reflective metasurface. For a TE linear polarization incident wave, this structure has two distinct bands; the first one lays in a wideband frequency range of 0.5-1.41 THz, in which the reflected wave would be a left-handed circular polarization (LHCP) with minimum efficiency of 89% and maximum efficiency of more than 95% in 80% of the bandwidth. The second band lays in the narrowband frequency range of 1.45-1.55 THz, resulting a right-handed circular polarization (RHCP) wave with a minimum efficiency of 82%. The proposed polarization converter can be used in optical communication and electronic devices.

The mutual coupling issue between two Right Hand Circularly Polarized (RHCP) Magneto-electric (ME) dipole antennas is addressed in this study. To mitigate this issue, a Metasurface Polarization-Rotator (MPR) Wall is employed, resulting in effective minimization of the coupling effects. The innovative antenna design, with high gain, shows promise for 5G applications. It consists of two electric dipole plates with triangular corners positioned at the top, along with two plates acting as magnetic dipoles perpendicular to the ground plane. Additionally, the presence of four plates on the outer periphery of the antenna contributes to the improvement of the circular polarization (CP) performance of the antenna. The feeding structure is configured in a V-shape. Integration of the metasurface polarization-rotator led to a significant reduction in mutual coupling. On average, the mutual coupling is decreased by more than -20.5 dB, reaching impressive values of -45 dB at 2 GHz, -55 dB at 3.1 GHz, and -40 dB at 3.7 GHz when the MPR wall is placed between the ME antennas. The antenna demonstrates promising performance in terms of impedance bandwidth, with a remarkable value of 61.4% for |S11| < [-10dB]. Furthermore, the axial ratio bandwidth for AR < [3 dB] is 63.36%, representing an 11% increase compared to the configuration without the MPR Wall. The maximum right-hand circular polarization gain achieved by the antenna is 9.91 dB at a frequency of 3 GHz. Additionally, the maximum front-to-back ratio (FBR) is 37.6 dB at a frequency of 2.5 GHz. By comparing and analyzing the simulation results for the scenarios with and without the MPR Wall, it becomes evident that the MPR Wall does not significantly affect the parameters of gain, front-to-back ratio, and impedance bandwidth.