Mohammadmahdi Farahani

Gain Enhancement of Circularly Polarized Dielectric Resonator Antenna Based on FSS Superstrate for MMW Applications

In this communication, a high gain circularly polarized (CP) dielectric resonator antenna (DRA) is proposed. The radiating DR is coupled to a 50 Ω microstrip line through an X-shaped slot etched off the common ground plane. Using a frequency selective surface superstrate layer, a gain enhancement of 8.5 dB is achieved. A detailed theoretical analysis is given and used to optimize the superstrate size and the air gap height between the antenna and superstrate layer. The proposed DRA is designed, simulated, implemented, and tested. The high gain CP DRA has the potential to be used for millimeter wave wireless communication and imaging systems.

Spatially Decoupling of CP Antennas Based on FSS for 30-GHz MIMO Systems

In this paper, an effective approach for mitigating the near-field coupling between four-port circularly polarized (CP) antennas in a 30-GHz multiple-input, multiple-output (MIMO) system is suggested and investigated. This is obtained by incorporating a two-layer transmission-type frequency selective surface (FSS) superstrate based on planar crossed-dipole metal strips. This paper presents a comparison between the mutual coupling when the patches are radiating in free space and in the presence of the FSS layers. The simulated results, when the FSS layers are applied, show an average of 6–12-dB improvement in the isolation between four adjacent CP-MIMO antennas. In addition, an accurate study is carried out on the insignificant reflections produced by the FSS layers to redirect those and also prevent any interference. The proposed

Millimeter-wave couraggated surface for mutual coupling reduction between dipole antennas

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Ka-Band Linear to Circular Polarization Converter Based on Multilayer Slab With Broadband Performance

CP-MIMO antenna along with the superstrate is implemented and tested to validate the simulation results. Experimental results of the coupling and reflection coefficients and axial ratio show an acceptable agreement with the corresponding simulated ones.

Miniaturized microstrip patch antenna using Electromagnetic Band Gap (EBG) structures for multiport passive UHF RFID-tag applications

The mutual coupling reduction between mm-wave dipole antennas using a corrugated surface is presented. The corrugated surface has a bandgap along the propagation direction toward the adjacent antenna. The mutual coupling is reduced between 4 to 20 dB when the corrugated surface is placed between the antennas. Moreover, the proposed corrugated surface does not have significant impact on the antenna radiation pattern.

Mutual coupling reduction in millimeter-wave MIMO dielectric resonator antenna using metamaterial polarization rotator wall

In this paper, a Ka-band polarization converter is presented, which is based on multilayer slab. In order to improve impedance matching, metallic circular traces are printed periodically on each dielectric multilayer slab. Simulated results of the polarizer show that it can transform linearly polarized (LP) to circularly polarized (CP) fields over a frequency band from 23 to 35GHz (42%) with an insertion loss less than 0.5 dB. The transmitted CP wave by the polarizer is approximately robust under oblique illuminations. The polarizer is fabricated and measured by a wideband horn antenna satisfying the simulated results. Next, in order to design a high-gain CP structure around 30 GHz, an 8-element LP array antenna with Chebyshev tapered distribution is designed and integrated with the polarizer. Obviously, the antenna limits the overall bandwidth (nearly 28 to 31.5 GHz) due to the narrowband nature of the LP antenna array. When the polarizer is illuminated by an incident LP wave, the two linear components of the transmitted wave with approximately equal amplitudes and 90° phase difference on the frequency band of interest are produced. Experimental results of the proposed structure show a pure CP with a gain of 13 dBi at 30 GHz, which can be suitable for millimeter wave communication.

A sequential-phase feed antenna subarray based on ridge gap waveguide

This paper presents a miniaturized microstrip patch antenna using an Electromagnetic Band Gap structures (EBG). The microstrip patch antenna is placed on an EBG unit cells layer. Therefore, the proposed antenna is miniaturized and its size is about 75 % compared to conventional antenna. Two chips are matched with the patch antenna at Ultra High Frequency (UHF) 915 MHz, which includes in America band. The proposed antenna is simulated and designed using HFSS software, and the simulation results show good performances in terms of matching, bandwidth, directivity and radiation pattern. The proposed antenna is suitable for passive UHF RFID-tag applications.

A Novel Low-Loss Millimeter-Wave 3-dB 90° Ridge-Gap Coupler Using Large Aperture Progressive Phase Compensation

An effective technique for reducing the mutual coupling between two mm-wave ridge-gap dielectric resonator antennas (DRA) using a novel technique is investigated and presented. This is achieved by embedding a metamaterial polarization rotator (MPR) wall between the two DRAs, which are placed in the H-plane. Using the proposed MPR wall, the TE and TM modes of the antenna become orthogonal which reduces the mutual coupling between the two DRAs. The proposed MPR wall is composed of 7×2 unit cells along the E-plane. The mutual coupling is reduced between 8 to 14 dB when the proposed MPR wall is placed between the antennas. Moreover, the proposed MPR wall does not affect the antenna characteristics.

Miniaturized two dimensional circular polarized magneto-dielectric substrate antenna

A 2×2 circularly polarized (CP) patch subarrays based on ridge gap waveguide (RGW) around 30GHz is designed. To broaden the CP bandwidth, the 2×2 patch subarray elements are fed by sequential feeding technique. The simulated results using CST show that the RGW feeding has a great performance in terms of impedance and radiation characteristics so that impedance and CP bandwidths are 30.5% and 21.5% respectively. In addition, a peak gain 13.5dB at 30GHz is achieved. Numerical results indicate that the proposed structure can cover the 3dB-gain bandwidth of 22.1%.

A CP-GPS antenna using low temperature cofired ceramic technology

A novel millimeter-wave (mm-wave) 90° phase-compensated hybrid coupler using the ridge-gap waveguide (RGW) technology is studied and developed. The coupler is low-loss at mm-wave frequency bands, whereas using conventional transmission lines, such as microstrip or substrate integrated waveguides, yields relatively a high amount of insertion loss. The proposed coupler is designed using large coupling apertures, which with their phase variation over the apertures can compensate for the progressive phase of the coupler and achieve a low output-phase error. The ridge-gap 3-db 90° hybrid coupler is suitable for designing mm-wave beamforming networks, such as the Butler matrix beamformer, where the cross-over transmission lines present a difficulty in designing such networks. In this paper, the dispersion diagram of the RGW is extracted, and a multicoupling aperture technique is formulated for designing the coupler. The coupler is fabricated and measured. The simulated and measured results show a good agreement.