Cavity-backed Microstrip Patch Research Articles

Feasibility Investigation of SIW Cavity-Backed Patch Antenna Array for Ku Band Applications

A cavity-backed microstrip patch antenna array was optimized in the Ku band. The backing cavity was designed under each patch antenna of the array in order to increase the bandwidth and minimize the intercoupling among the radiating elements. Substrate integrated waveguide (SIW) technology was employed to fabricate the above-mentioned cavity below the radiating patch. More precisely, four microstrip array antennas, made by 2 × 2, 4 × 4, 8 × 8, and 16 × 16 elements were designed, fabricated, and characterized. The measured maximum gain was G = 13 dBi, G = 18.7 dBi, G = 23.8 dBi, and G = 29.2 dBi, respectively. The performance of the proposed antenna arrays was evaluated in terms of radiation pattern and bandwidth. An extensive feasibility investigation was performed even from the point of different materials/costs in order to state the potential of the engineered antennas in actual applications. The obtained results indicate that a cavity-backed microstrip patch antenna is a feasible solution for broadband digital radio and other satellite communication overall for niche applications.

Wideband Dual-Polarization Microstrip Patch Antenna Array for Airborne Ice Sounder

We present the design and realization of an antenna array based on cavity-backed microstrip patch antenna elements, with a relative operating bandwidth exceeding 20% at a return-loss level better than 15 dB. The antenna array of four elements did not show any compromise in bandwidth. It exhibited sidelobe levels better than 15 dB, with a gain of around 12 dBi. Excellent agreement was achieved between measurements and predictions for the designs of both the single element and the array. This antenna is part of the European Space Agency's airborne polarimetric P-band terrestrial ice sounder.

A Cavity-Backed Aperture-Coupled Microstrip Patch Antenna Array with Sum/Difference Beams

This paper presents a new cavity-backed aperture-coupled microstrip patch antenna (ACMPA) array with sum/difference beams. It is composed of a feed network and two aperture-coupled elliptical patch antennas. A metallic cavity is used at the back of the antenna array to minimize the back radiation. The feed network is realized by a planar magic-T, which consists of microstrip and slotline T-junctions coupled by microstrip-slotline transitions. The antenna is designed, manufactured and tested at 35 GHz. Measurements show clean and symmetrical patterns are realized for both the sum and difference beams. The measured −3-dB E- and H-plane beamwidths of the sum pattern are 55.8◦ and 77.6◦, respectively. A deep null of −32.4 dB is achieved for the difference pattern. Meanwhile, the measured return losses for both the sum and difference ports are less than 10 dB from 34.2–36.6 GHz corresponding to a bandwidth of 6.8%. Within this bandwidth, the isolation between the sum and the difference ports is better than 38 dB.

Substrate-Integrated Cavity-Backed Patch Arrays: A Low-Cost Approach for Bandwidth Enhancement

The substrate-integrated waveguide (SIW) technology is utilized as an alternative low-cost approach in fabricating cavity-backed patch antennas. The proposed antenna arrays combine the attractive features of the conventional metalized cavity-backed patch arrays like surface wave suppression, high radiation efficiency, and enhanced bandwidth, yet provide a low manufacturing cost. A previously developed design of a 2×2 SIW cavity-backed microstrip patch sub-array is extended here and used as a basic building block to attain larger arrays of 2 × 4, 4 × 4, and 8 × 8 elements. The fabricated arrays have been measured and demonstrate good agreement with their simulated performance. The design and performance of these arrays are compared to other conventional bandwidth enhancement techniques, which prove SIW as a viable alternative.

A Differential Dual-Polarized Cavity-Backed Microstrip Patch Antenna With Independent Frequency Tuning

A dual-polarized cavity-backed microstrip patch antenna has been demonstrated with independent tuning of both polarizations from 0.6 GHz to ~1.0 GHz using varactor diodes (1.2-5.4 pF). The 10-dB impedance bandwidth varies from 0.9% to 1.8% over that range. Differential coaxial feeds and the placement of the tuning varactors in the appropriate symmetry planes are employed to achieve a differential-mode port-to-port isolation of >28 dB over the tuning range. Accordingly, the cross-polarization level is <; -20 dB at broadside. The antenna is 100 × 100 × 6.4 mm3 and is fabricated on a dielectric substrate (er = 2.2). The feed point and matching circuit for an impedance match to 50 Ω are determined using the transmission line model. This model underestimates the sensitivity of the resonance frequency to the loading capacitance, but leads to a good initial design. To the authors' knowledge, this is the first dual-polarized antenna with independent tuning over a 1.7:1 bandwidth and single-sided radiation.

Substrate-Integrated Waveguide Ku-Band Cavity-Backed 2 $\,\times\,$2 Microstrip Patch Array Antenna

A Ku-band cavity-backed microstrip patch 2 x 2 antenna array has been implemented using the substrate-integrated waveguide (SIW) technology-a low-cost multilayer printed circuit board (PCB) process. Cavities are emulated using vias, and the patches are fed using microstrip lines that are centrally fed by a shielded coaxial probe feed line. Simple design guidelines for the cavity, patch, and substrate selection are presented. The array was fabricated, and its measured results agreed very well with theoretical predictions and indicated a relatively high efficiency and wide bandwidth of greater than 70% and 9%, respectively.

Broadband high‐efficiency microstrip antenna array with corporate‐series‐feed

AbstractA linearly polarized microstrip antenna array in the Ku‐band achieves high efficiency by having the proper impedance matching throughout the array and by properly using the corporate and series feeds with microstrip transmission lines. The efficiency of the antenna array is 83.3%. The cavity‐backed microstrip patch is used as the element of the antenna array to obtain relatively wide bandwidth. The auto‐tracking antenna in the azimuth direction is developed with a very low profile as well as a low manufacturing cost for the vehicle's rooftop mounting. The main beam of array is tilted 15° away from the broadside direction to provide optimum coverage for Korea satellite III. The measured gain of an antenna array is 23.8 dBi at the center frequency of 12.5 GHz. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 181–183, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20413

Chiral cover effects on microstrip antennas

By exploiting a rigorous variational formulation, we point out the main effects of a chiral cover on a cavity backed microstrip patch antenna. A hybrid finite element-boundary integral method is employed to solve numerically the electromagnetic problem modeled by a variational functional. The dependence of the resonance frequency on the cover thickness and on the chirality admittance of the material is first investigated. In more detail, it is demonstrated that a chiral cover permits reducing the antenna dimensions, compared to an isotropic one, for a fixed working frequency. Then, through several numerical examples, we also investigate the variation of gain properties, cross-polarization levels, radiation resistance, radiation efficiency, and radar cross-section.

Mutual coupling between patch antennas recessed in an elliptic cylinder

Cavity-backed microstrip patch antennas are often used in aircraft applications because of their ability to conform to the vehicle surface. For arrays of patches, it is important to be able to predict the dependence on surface curvature of the coupling between patches. The mutual impedance between two rectangular patch antennas recessed in an elliptic cylinder is computed using a finite element-boundary integral method. Results show that the coupling between the antennas is dependent on the curvature of the cylinder surface. For H-plane coupling, the coupling decreases as the radius of curvature increases. For E-plane coupling, the strongest coupling occurs for a specific curvature.

FEM-BEM formulation for the analysis of cavity-backed patch antennas on chiral substrates

An extended variational formulation to study cavity-backed microstrip patch antennas with chiral materials is presented. A finite-element boundary integral numerical approach is applied to satisfy the stationary condition associated with the variational formulation and some features of chiral media for patch antenna applications are investigated. Specifically, an appreciable reduction of the antenna dimensions with respect to the isotropic case and an undesirable increase in the cross-polarization levels are observed.

Efficient full-wave analysis of mutual coupling between cavity-backed microstrip patch antennas

A full-wave methodology for a broadband analysis of isolated cavity-backed and probe-fed arbitrarily shaped microstrip patch antennas is combined with an analytical method based on the properties of rotation and translation of spherical modes for obtaining an efficient scattering matrix description of the mutual coupling in a two-element array. The proposed procedure is validated and results are given for identical circular cavity-backed patch antennas.

Scattering properties of antennas residing in cavities filled by inhomogeneous materials via a variational formulation

Inhomogeneous media exhibit many properties that are very useful either in microwave circuits or in radiation components. In this paper a scattering analysis of cavity-backed microstrip patch antennas with inhomogeneous slabs is proposed. An equivalent variational formulation of the electromagnetic problem for this kind of antenna is derived, such that a very efficient Finite Element Method-Boundary Integral code can be straightforwardly applied. Numerical results are compared with those known in the literature showing an excellent agreement with them. The main scattering properties of the inhomogeneous substrates are also pointed out and compared with those of homogeneous substrates.

Fast frequency-sweep analysis of cavity-backed microstrip patch antennas

A fast frequency-sweep technique is presented for the analysis of cavity-backed microstrip patch antennas. This technique applies the method of asymptotic waveform evaluation (AWE) to the hybrid finite-element boundary-integral (FE–BI) solution of the original boundary-value problem. Numerical examples show that the proposed technique can speed up the analysis by more than an order of magnitude. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 22: 389–393, 1999

Fast frequency-sweep analysis of microstrip antennas on dispersive substrate

A fast technique that combines the method of asymptotic waveform evaluation (AWE) and the hybrid finite-element boundary-integral (FE-BI) method is introduced for the analysis of cavity-backed microstrip patch antennas residing on a dispersive substrate. Numerical examples are given to demonstrate the accuracy and efficiency of the technique.

Fast RCS Computation Over a Frequency Band Using Combined FEM/MoM Technique in Conjunction with Asymptotic Waveform Evaluation (AWE)

ABSTRACT A novel and fast hybrid Finite Element Method/Method of Moments (FEM/MoM) technique in conjunction with Asymptotic Waveform Evaluation (AWE) is presented to calculate radar cross section (RCS) over a wide frequency range of a cavity-backed aperture in an infinite ground plane. The hybrid FEM/ MoM technique when applied to the cavity-backed aperture results in an integro-differential equation with electric field as the unknown variable. The electric field obtained from the solution of the integro-differential equation is expanded as a function of frequency in Taylor series. The coefficients of the Taylor series are determined using the frequency derivatives of this equation. The Taylor series is then matched via the Pad'e approximation to obtain a rational polynomial representation for the electric field, which can be used to extrapolate the electric field over a frequency range. The RCS of the cavity-backed aperture is calculated using the electric field at different frequencies. Numerical results for a square cavity, a circular cavity, and a cavity-backed microstrip patch are presented over a frequency range. Good agreement between AWE and the exact solution over the frequency range is obtained and the present method proved to be cost effective in terms of CPU time compared to calculating RCS at each frequency.

Cavity backed microstrip patch array feed for multiple beam applications

Multiple beam antennas use reflectors with several feeds at offset locations in the focal plane. The complete feed array tends to be bulky and heavy, hence, to alleviate this, microstrip patch arrays have been used as feed elements. However, a power division circuit becomes necessary for the patches which increases losses. A patch array backed by a cylindrical cavity is proposed which eliminates this lossy circuit. An additional feature is that the beamwidths in various planes may be controlled to a certain extent by varying the interelement spacing. The test results of the proposed feed are presented and discussed; the feed seems suitable for use in multiple-beam applications.

Broadband microstrip patch antenna on micromachined silicon substrates

A micromachined rectangular cavity-backed microstrip patch antenna has been developed on high resistivity silicon wafers. This novel patch antenna has a much reduced effective dielectric constant and wide bandwidth.

Analysis of microstrip antennas with complex and anisotropic substrate by a hybrid FEM/BEM approach

In this paper, a hybrid formulation based on the finite element method (FEM) and boundary element method (BEM) is presented for numerical analysis of the electromagnetic (EM) radiation and scattering from cavity-backed microstrip patch antennas. The cavity is recessed in a ground plane and may have arbitrary shape and contain inhomogeneous, anisotropic, and lossy dielectric materials. The formulation has been implemented using edge elements and the computer program has been tested by a number of numerical examples, proven to be valid and robust.

Scattering and radiation analysis of cavity-backed microstrip patch antennae with anisotropic slabs via a variational formulation

Abstract In this paper we examine an arbitrarily shaped cavity-backed microstrip patch antenna with a very general anisotropic grounded slab. We apply a hybrid finite-element-boundary-integral method. We use the finite-element method to solve the Helmholtz equation in the interior of the micro-strip antenna and use the boundary-integral method, together with the dyadic Green function approach, to determine the fields exterior to the microstrip patch antenna. We couple the two methods at the interface plane by enforcing the field continuity conditions. Several numerical results are presented demonstrating the validity, efficiency and capability of this technique.

Scattering and radiation analysis of cavity-backed microstrip patch antennae with anisotropic slabs via a variational formulation

In this paper we examine an arbitrarily shaped cavity-backed microstrip patch antenna with a very general anisotropic grounded slab. We apply a hybrid finite-element-boundary-integral method. We use the finite-element method to solve the Helmholtz equation in the interior of the micro-strip antenna and use the boundary-integral method, together with the dyadic Green function approach, to determine the fields exterior to the microstrip patch antenna. We couple the two methods at the interface plane by enforcing the field continuity conditions. Several numerical results are presented demonstrating the validity, efficiency and capability of this technique.