A high-isolation Fabry–Perot (FP) antenna array with wide bandwidth and high gain is proposed for Ku -band vehicle satellite communications. Each antenna element consists of a pair of tandem circular parasitic patches (TCPPs), a radial gradient partially reflective surface (PRS), and a reflector, respectively, separated from the ground plane with a double-dumbbell-shaped slot (DDSS) by air layer and foam dielectric. The slot radiator steers the TCPPs to create multiple resonant frequencies and then the impedance bandwidth is widened. The impedance matching could be improved by adjusting four circular slot diameters of the DDSS. The gain is raised by TCPPs and radial gradient PRS, which function to guide the electromagnetic field and uniformize the aperture near-field, successively. The reflector with several resonator elements is used to reduce the backside radiation. As proof of concept, the FP antenna array prototype with a height of $0.613\lambda _{0}$ has been fabricated and measurements confirming simulations are provided. Experimental results show that the impedance bandwidth ranges from 13.48 to 16.95 GHz [22.8% fractional bandwidth (FBW)], and the realized gain is up to 21.59 dBi. A decoupling metallic strip could achieve over 40.8 dB isolation. The proposed antenna element is easily extended for the multiple-input multiple-output (MIMO) and beamforming antennas, further improving the directivity.

Wideband Gain Enhancement of High-Isolation Fabry–Pérot Antenna Array With Tandem Circular Parasitic Patches and Radial Gradient PRS

This letter explores geometrical optics-based raytracing in combination with modal analysis to realize an open cavity structure as an advanced variant of the resonant cavity antenna (RCA). Additional ray confinement has been ensured by determining accurate phase-locking conditions as demonstrated for the first time. Its combination with the analysis of the cavity mode has also been introduced to determine the optimum design parameters, achieving improved radiation properties. With respect to a reference RCA reported earlier, the proposed approach exhibits a remarkable improvement in gain by 4–9 dB, resulting in about 17 dBi peak value consistently over the full 18% matching bandwidth. This is resultant from an increase in aperture efficiency, typically from 27% to 74%. This is achieved without any compromise with the cross-polarization property. The sidelobe level improves over the band except in higher frequency in H-plane. The proposed concept is commercially viable, showing significantly advantageous features.

Geometrical Optics-Based Advanced Design of an Open Cavity Resonant Antenna

Executive

Fabry-Perot Antenna (FPA) is actually a one-dimensional resonant cavity to serve as a high gain radiator. This may consider as a replacement of large antenna array bearing some new features. Higher directivity is obtained through a uniform phase-front developed within the vertical cavity consists of a ground plane and a superstrate layer. The resonance condition of the cavity is maintained by adjusting its dimension as half of the wavelength of the radiating wave. A ‘primary-radiator’ indeed illuminates the Fabry-Perot cavity. Its high-gain characteristics are determined by this primary-radiator along with the superstrate layer. A grounded radiating aperture, a conventional microstrip patch, or a dielectric resonator antenna (DRA) having a broadside radiation pattern commonly serves as the primary-radiator in an FPA design. Traditionally, the superstrates were physically realized as partially reflecting surfaces (PRSs) such as thin dielectric slab, frequency selective surface (FSS), electromagnetic bandgap structure (EBG), artificial magnetic conductor (AMC), metamaterial, metal grid structure, etc. Their gain-enhancement mechanism used to be demonstrated in terms of reflection coefficients [1] or leaky-wave generation. Their basic concept was leakage of electromagnetic energy through the semi-transparent superstrate.

Fabry-Perot Resonant Cavity Antenna: New Theory and Design Opportunity

An advanced design of a Fabry–Perot cavity antenna (FPCA) is proposed to achieve wide common impedance and gain bandwidth along with high gain. A compact and lightweight FPCA is achieved by employing a printed primary radiator and superstrate with superior manufacturing capabilities. A wideband primary radiator is employed for the first time to realize such a wideband FPCA. Superstrate dimensions are estimated by using the aperture field theory and the proposed design is validated through both EM simulation and experiment. The measured broadside gain is shown to be better than 11.5 dBi over an impedance bandwidth of 63% (8.2−15.6 GHz). About 40% common impedance and gain bandwidth is achieved while the broadside gain attains a maximum value of 17.4 dBi. To the best of our knowledge, this has never been achieved before from an FPCA made of a printed superstrate and a primary radiator. The cross-polar (XP) radiation remains under −40 dB whereas the front-to-back ratio remains above 35 dB, over the desired bandwidth.

Advanced Design of High-Gain Fabry–Perot Cavity Antenna Offering Wide Common Impedance and Gain Bandwidth

A new design of Fabry-Perot cavity antenna (FPCA) has been presented with a unique as well as the most desirable feature of very high-gain maintained over its wide matching bandwidth. About 15.5 dBi average broadside-gain has been achieved over the 19% matching bandwidth. A flat-gain characteristic has been attained using a specially designed conical sidewall. In addition to that, the sidewall will play an important role in reducing the mutual coupling arises due to nearby RF elements. About −16 dB and −19 dB side lobe levels have been obtained satisfactorily in two principle-plane patterns (E- and H-plane) respectively. The cross-polarization purity of the antenna is maintained reasonably below −25 dB over the frequency band.

Spandan Manna

Papers

Geometrical Optics-Based Advanced Design of an Open Cavity Resonant Antenna

Wideband Design of a Fabry-Perot Cavity Antenna with Improved Features