In this study, a novel dual-band multiple-feed microstrip antenna is introduced for GNSS applications. The proposed antenna has a compact size of 1548 and counts as a low-cost, low-profile antenna. The mathematical equations of multiple-feed configuration are driven to analyze Circular polarization ( ) generation and find the effective parameters on value. It is shown that for an n-feed symmetric antenna, the phase shift of between ports leads to pure , regardless of the electrical field pattern. However, if the first feed electric field has equal value in the x and y direction and also 90 phase shift, the value is increased. A symmetric four-feed configuration is employed on the antenna to generate . Also, fractal Circular rings and perturbing sectors are applied to miniaturize the antenna and improve the value. Numerical simulation shows that all feeding network requirements are met and the phase shift is satisfied at both frequencies by using the coupler technique. Furthermore, results show desirable band width of 48 and 60 and high front to back ratio of 16.1 and 14 at =1.227 and =1.575 , respectively. The axial ratio ( ) beam-width at both frequencies is more than 66 .

In this paper, a new X band Metamaterial (MTM) based ferrite phase shifter is presented. The phase shifter is excited by Circular polarized wave base on combination of TE10 and TE01 modes in a square waveguide. In order to synthesize negative index material (NIM), negative permeability of ferrite slabs in extraordinary mode is mixed with the negative permitivity of printed periodic metallic wires on substrate, in the same frequency band. By using the introduced new Circular polarized MTM based layout, the proposed phase shifter loss is less than 3 dB, while the loss of MTM waveguide phase shifters is about 10 dB. Also, the proposed phase shifter profits the miniaturization property of MTM design usage. The total length of the phase shifter is 2 cm with 360° differential phase shift, compared to common dual mode phase shifter with 6 cm length in X band.

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.

Circular polarization is one of the most popular polarization approaches used in different communication systems such as radar, satellite, GPS and WiMAX systems. In this article, we want to design a wideband cylindrical antenna with Circular polarization and maximum frequency coverage from 1. 7 to 2. 7 GHZ. If the optimum load impedance of the amplifier at different frequencies are close, the antenna can be used as an optimal load for the amplifier. In this paper the output of the antenna after application of signals in the S band is also investigated and the effects of the antenna radiation on the amplifier circuits have been considered to some extent.

In this article, a conformal leaky wave antenna with a substrate-integrated waveguide (SIW) structure on a new unit cell substrate is presented. The use of this new method eliminates the main problem of this type of antenna, which is the existence of a stop band (OSB), and enables the antenna to radiate in Broadside as well. In this article, after introducing the new unit cell, a flat leaky wave antenna with an integrated waveguide structure under the layer, which is able to continuously scan from -76.6 to +27 degrees by changing the feeding frequency, was designed and investigated. At the end, the proposed flat antenna is adapted on the surface of a cylinder with a radius of 425 mm. A conformal leaky wave antenna is able to continuously scan from -43 to +37 degrees by changing the feeding frequency. As a result, a scan with Circular polarization from negative to positive angles, which also includes broadside radiation, has been obtained.

One of the methods for optimizing the radiation characteristics of microstrip antennas is using metamaterial as substrate and superstrate. In this research, a rectangular microstrip antenna with Circular polarization and conical pattern is designed at 2.2 GHz frequency. For creating Circular polarization cutting corner method is used and to create conical pattern, 4 array rectangular microstrip patch antennas are used and each antenna is feeded by microstrip line and whole of structure is feeded by a 50 Ω SMA connector. To improve the radiation characteristics and optimize the dimensions of antenna, a 10×10 aray layer of metamaterial is used as substrate and Then the antenna has been made. The metamaterial parameters such as Permeability (µ) and Permittivity (ε) is extracted by Nicolson-Rose method. The simulation results show that the antenna dimensions is decreased 30% and bandwidth and gain of the antenna are increased 17% and 45% respectively. All the simulation process for antenna designation is implemented in HFSS 18.2 software.

In this paper, a new compact quadruple slot antenna is proposed for GPS applications. This antenna has a right hand Circular polarization which is suitable for GPS satellite signal reception. The antenna is formed by four similar slot antenna excited with 90 degree phase difference. The antenna dimension is 12Î24Î24mm3 which is very compact compared with the references.Moreover, the antenna has a very good right hand polarization in the horizon which increases the GPS accuracy. Also, the antenna gain is 2.44 dB at the GPS frequency which is good enough for signal acquisition. These specifications introduce this antenna as a good candidate for GPS applications.

The demand for mobile communication systems with high data rate has drawn attention to the millimeter-wave frequencies to increases the channel capacity compared to current 4G cellular networks. So, the fifth generation (5G) mobile communications is presented which is to work in mm-wave frequency band to improve data rate, capacity and latency. One of the challenges of 5G application is the base station and mobile antennas which should be robust against fading. Therefore, in this paper, a two port substrate integrated waveguide (SIW) slot base station antenna for 5G application at 28 GHz is presented. The realized gain of the two-port antenna with a high isolation (20 dB) and Circular polarization is 6. 35 dBi. The 5-element array of the two-port antenna with the same excitation can increase the gain 8 dB, but it has some nulls. With phase shift for excitation ports, the nulls are cancelled.

In this paper, a waveguide polarizer switch is designed, fabricated and tested with linear and Circular polarization ability. Input and output of this structure are WR112 and square waveguide, respectively. This switch is high power and the operating frequency is X band. This structure is composed of several waveguide pieces that they rotate rather than together by an electrical motor. A septum polarizer is designed and fabricated for operation accuracy of the switch. In this work, relations of the switch are extracted. The structure is simulated by CST software and the simulation results are compared with measured results. There is good agreement between the simulation and measurement results. Also, the switch has small size.