Cavity-backed Microstrip Antenna Research Articles

Designing a Cavity Backed Microstrip Antenna with Enhanced Isolation for the Development of a Continuous Wave Ground Penetrating Radar

This paper presents an improved design of a rectangular microstrip antenna at 920 MHz by backing it with an appropriate cavity wall to enhance the isolation between the transmitter and receiver antenna for use in applications, where the weak received power gets masked by the direct coupled power between two antennas. Antennas having 0.12 λ cavity wall with separation gap of 0.36 λ resulted in an isolation of 52.6 dB at a resonance frequency of 920 MHz with maximum and minimum isolation of 71.4 dB and 49.1 dB, respectively for 5% BW of the antenna designed. These antennas were fabricated and tested, which are used in the development of Continuous Wave Ground Penetrating Radar with an online graphical user interface; leading to the validation of the usefulness of proposed antennas. The isolation achieved at an optimised separation of the antennas enabled detection of metal targets as small as a bunch of wire buried 20 cm in the soil and non-metal, like wood and plastic buried in soil. It enabled the detection of a circular steel target of radius 12.5 cm buried at a depth of 65 cm in loose semi-dry pebbled soil.

A Broadband Proximity-Coupled Stacked Microstrip Antenna With Cavity-Backed Configuration

A broadband cavity-backed proximity-coupled stacked microstrip antenna is presented. Due to the interaction of the two stacked patches, two associated resonances are produced. Unlike conventional proximity-coupled or cavity-backed microstrip antennas, the lower patch and the cavity of this antenna produce the coupled resonances. These devised methods make the antenna act as multiple resonances, conducing to a broadband impedance matching. The simulated and the measured results demonstrate a bandwidth over one octave (VSWR <; 2). In the meantime, stable radiation patterns are obtained across the entire impedance band. The key parameters of the antenna are studied, and a prototype antenna that has a three-dimensional interconnection structure is provided.

Embedded air cavity backed microstrip antenna on an LTCC substrate

One of the major challenges for next-generation, highly integrated, wireless system-on-packages (SOPs) is to integrate the antenna into the package. Due to the inherent narrow bandwidth of planar antennas on LTCC substrates that have moderate relative permittivities in the range 5–20, techniques for improving the bandwidth have to be considered in order to meet the requirements of wideband telecommunication standards. This paper presents a study of laser-micromachined air cavities embedded into an LTCC substrate, and their application in improving the bandwidth of an aperture coupled microstrip patch antenna operating at around 10 GHz. Furthermore, the effects of the air cavity on the size, gain, and radiation efficiency of the antenna are presented and discussed.

Analysis of cavity-backed microstrip antennas by a 3-D finite element/segmentation method and a matrix Lanczos-Pade algorithm (SFELP)

A methodology that combines the domain segmentation technique, the three-dimensional finite-element method (3-D FEM), and a symmetric matrix Lanczos-Pade algorithm, is used for the fast frequency-sweep analysis of cavity-backed microstrip antennas by using a spherical mode expansion on the radiation boundary. Results for a circular patch antenna validate the proposed method.

Broad-Band U-Slot Patch Antennas Loaded By Chiral Material

The analysis of wide band microstrip/slot antennas residing in cavities with arbitrary patch shapes and in presence of both isotropic and chiral materials is proposed in this paper. The theoretical approach is based on the variational formulation and the numerical solution is carried out by applying a combined Finite Element-Boundary Integral (FE-BI) Method. Such an approach already known in the literature only for isotropic and anisotropic media is extended also to the case of biisotropic dielectrics, including chiral materials. A numerical code based on the new theory here presented has been developed and it is employed in order to investigate the main features of chiral materials as substrates for cavity backed microstrip antennas. This numerical code allows to study also antennas loaded by isotropic substrates as particular cases when imposing the chiral admittance to vanish. To test this capability the design of an U-slot microstrip antenna printed on a conventional isotropic dielectric for wide band applications is proposed. Finally, it is shown how the employment of chiral substrates instead of isotropic ones reduces the antenna size for a fixed working frequency and improves the impedance bandwidth, without decreasing too much the other radiating properties.

Grounded coplanar waveguide-fed aperture-coupled cavity-backed microstrip antenna

Microstrip antennas aperture coupled to a grounded coplanar waveguide (GCPW) have been fabricated on a single layer substrate and studied experimentally and theoretically. Through-plated via holes are used to suppress spurious parallel plate modes. Measurements demonstrate that this antenna element has good performance for both bandwidth and radiation patterns. Calculations using a commercial CAD package are in reasonable agreement with measured data.

Scattering from a cavity backed microstrip antenna on a bi-anisotropic substrate with a finite ground plane by a hybrid finite element method

A new extended finite element formulation for finding radiation patterns, radar cross section (RCS) and input impedance of planar integrated circuits on a very general bi-anisotropic grounded slab with finite size is presented. The approach is based on a hybrid finite element method (FEM) wherein the electromagnetic fields in the FEM region are coupled to the fields outside by a surface integral equation. Because of the local nature of the FEM, this formalism allows inclusion of the inhomogeneities in the problem domain. Numerical results are compared and agree well with existing published data for various conventional configurations.

45-GHz MMIC power combining using a circuit-fed, spatially combined array

We describe the design and measurement of a hybrid-circuit, tile-approach subarray for use in spatial power-combined transmitters. The subarray consists of 16 monolithic millimeter-wave integrated circuit (MMIC) amplifiers, each feeding a circularly polarized cavity-backed microstrip antenna. The average performance across the 43.5-45.5 GHz band is as follows: EIRP 18.3 dBW, DC-RF efficiency 10.3%, effective transmitter power 530 mW, system gain 13.2 dB, and combining efficiency of 46.2%. The minimum axial ratio is 1.2 dB at 43.9 GHz, and the array has a 3% 3-dB axial ratio bandwidth.