Spectral domain analysis of aperture-coupled microstrip patch antennas

An aperture-coupled rectangular microstrip patch antenna fed by an orthogonal substrate integrated waveguide (SIW) feed line is of high interest for one-sided imaging systems. This type of feeding technique is beneficial for 2D imaging array configurations in millimeter wave imaging systems due to the limited availability of space for compact array design. In order to reduce the coupling between two adjacent patches (which deteriorates the quality of the imaging results), an artificial impedance metasurface can be used. When properly designed for this purpose, the imaging frequency corresponds to the bandgap frequency of the metasurface. In this paper, a metasurface integrated with this new type of feeding technique is presented. The improved structure shows a 20 dB reduction in coupling (|S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</sub> |) between two adjacent antennas separated by a spacing of one wavelength at an imaging frequency of 30 GHz.

This paper describes a new aperture‐coupled microstrip patch antenna with H‐shaped slots for dual‐band and dual‐polarized operations. Two orthogonal modes are excited in a single long rectangular patch to achieve the two resonant frequencies with a separation of more than 2:1. By using five parasitic conducting strips stacked on the driven patch, the impedance bandwidths can be increased and isolation of more than 34 dB between the two ports is obtained. Moreover, the cross‐polarization levels for the two polarizations are found to be better than 25 dB. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 44–46, 2003

An analysis and equivalent circuit model for an H-shape cross slotted aperture-coupled microstrip patch antenna (ACMPA) are presented. The study in the paper helps us to understand better the antenna property and also provides an easy way to design the antenna. The ACMPA consists of three conductor layers such as patch, ground plane, and feed line. The coupling exists in two places. One between the patch and a slot in the ground and the other between the slot and the feed line are represented by the ideal transformers. To calculate the turn ratio of the ideal transformer effectively the reciprocity theorem and the spectral-domain immittance approach are used. Moreover, vertical slots of `H' slot are considered as the reactive loads. The H-shape cross-slotted ACMPA operating at 3 GHz and 5 GHz simultaneously is fabricated. The good agreement between theoretical and measured results is shown.

This paper describes an efficient design method for an aperture‐coupled microstrip patch antenna, based on an improved transmission line model. The governing equations have been derived and applied to the design of the antenna with a center operating frequency of 11 GHz. The theoretical return loss was compared to the observed results from the fabricated antenna. The error of the proposed design method is less than 1.5%. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 75–78, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11132

Circularly polarized patch antennas are finding increasing use in far-distance communications such as the satellite broadcasting and communication, and in near-distance communications such as the indoor wireless LAN system and the wireless card system, because of their features of lower cost, less weight and lower profile. Practical patch antennas are often covered with a dielectric superstrate for protection against environmental hazards. It is important to predict the effect of this superstrate on the operating characteristics such as the resonant frequency and input impedance. The spectral domain approach using two entire basis functions, respectively corresponding to electric currents flowing on the patch surface of two degenerate modes, is extended to study the resonant frequencies of two degenerate modes, the circular polarization condition and the input impedance of a circularly polarized rectangular patch antenna with a superstrate, excited by a coaxial probe.

Aperture-coupled microstrip patch antennas are very attractive candidates for many polarimetric phased array applications. They offer an excellent electrical performance and are easy to manufacture. Due to their multilayer design an optimum choice can be made for the patch and the feed substrate. Low-permittivity patch substrates yield a high bandwidth as well as high radiation efficiency. Dual linear polarization can be achieved by either crossed slot or offset slot configurations. Depending on the bandwidth the typical polarization isolation of dual polarized aperture-coupled antenna elements on low-permittivity substrates is about -25 dB. However, for several phased array applications a even higher polarization isolation is required. By sequential feeding techniques a significant improvement of the polarization purity at the array level with values of better than -45 dB is achieved. However, microstrip patch arrays with sequentially rotated antenna elements show a different coupling and scan behavior than arrays with unidirectional aligned antenna elements. This paper investigates microstrip patch arrays for phased array applications in the C-band with a sequential feeding technique.

This paper presents a systematic parameter study of aperture-coupled stacked patch antennas fed by coplanar waveguide. These antennas are to be used at millimeter-wave frequencies in the 30-GHz range. The influence of the most important design parameters, such as patch dimensions, aperture dimensions, and substrate thicknesses, was studied extensively. It has been found that these antennas can easily be impedance-matched by tuning the dimensions of the excitation slot and adding a small tuning stub. In this way, an antenna element with a -10 dB impedance bandwidth of 36.8% has been designed. Furthermore, the results of this parameter study have allowed to formulate some general guidelines concerning the design of this type of antenna element.

This communication presents a high-low-epsilon (HLE) biaxial anisotropic lens for enhancing the gain of a linearly polarized antenna at 28 GHz. The theory and mechanism of gain enhancement using the biaxial anisotropic HLE lens is presented along with the realization of the HLE media using metamaterials (MTMs). First, the gain enhancement is studied using a microstrip patch antenna loaded with the HLE slab, and a peak gain of 13.9 dBi achieved with HLE slab in simulations. This gain enhancement is attributed to the special propagation properties of the waves in biaxial anisotropic media. The HLE media is practically realized using seven MTM layers stacked over each other and then loaded to the patch antenna and the substrate integrated waveguide (SIW) fed aperture coupled patch antenna (ACPA) to verify the gain enhancement. The measurement results confirm realized peak gain of 13.71 and 13.67 dBi for patch and ACPAs, respectively. Both the antennas have an overall height of 0.65λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> , and the proposed technique results in aperture efficiencies greater than 97% and 94% for the two antennas, respectively, at 28 GHz.

This paper presents the development, fabrication, and measurement of a novel beam-forming system consisting of 16 subarray antennas, each containing four aperture-coupled patch antennas, and the application of this system in smart wireless communication systems. The beam patterns of each of the subarray antennas can be switched toward one of nine zones over a half space by adjusting the specific phase delay angles among the four antenna elements. Furthermore, when all subarrays are pointed at the same zone, slightly continuous beam steering in around 1° increments can be achieved by dynamically altering the progressive phase delay angle among the subarrays. Phase angle calibration was implemented by coupling each transmitter output and down converter into the in-phase/quadrature baseband to calculate the correction factor to the weight. In addition, to validate the proposed concepts and the fabricated 2-D phased array antenna system, this study measured the far-field radiation patterns of the aperture-coupled patch array integrated with feeding networks and a phase-calibration system to carefully verify its spatially switched-beam and beam-steering characteristics at a center frequency of 2.4 GHz which can cover the industrial, scientific, and medical band and some long-term evolution applications. In addition, measured results were compared with calculated results, and agreement between them was observed.

This paper had been comparing the performance of the normal patch antenna with single complimentary SRR patch antenna. Four different shapes of single complimentary split ring resonator structure had been incorporated into the microstrip patch antenna - square, circular, triangular, and rhombic. This simulation works had been done in CST Microwave Studio simulation software. The operating frequency of this antenna is 2.40 GHz for Wireless Local Area Network (WLAN) application. The parameters that considered in these works are return loss, resonant frequency, input impedance, gain, radiation pattern and bandwidth. The focusing parameter is to achieve the best gain performance that obtained from the single complimentary split ring resonator patch antenna. The addition of square SRR onto patch antenna will improve the gain from 6.334 dB to 6.508 dB.

A novel design of an active antenna with a dielectric resonator stabilized HEMT (high electron mobility transistor) oscillator (DRO) and an aperture-coupled patch antenna is reported. The circuit is fabricated using a coplanar waveguide (CPW) with the oscillator and the antenna on opposite sides of the substrate. The active antenna was demonstrated at 7.6 GHz; however, the design can be scaled to higher frequencies. Excellent oscillator characteristics and radiation patterns have been obtained.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The spectral domain technique (SDT) is extended to take into account both finite thickness and conductivity of strips in planar monolithic integrated transmission lines. The proposed extension subdivides a strip into elementary thin strips, and preserves the efficiency and versatility of the classical SDT.

The general problem of a cavity-backed aperture radiator is formulated for the tangential electric field in the aperture. The result is used to obtain an integro-differential equation for the special case of a narrow slot backed by a rectangular cavity resonator. This equation is then solved numerically by the method of moments with the proper choice of piecewise sinusoidal basis and testing functions to remove the differential operator in the integrand. Typical numerical results are presented to show the effect of various cavity and slot dimensions on quantities such as voltage distribution along the slot, input impedance, resonance frequency and bandwidth of the antenna.

The input and mutual impedances of rectangular microstrip patches mounted on a spherical structure are studied in the paper. The analysis approach is based on the moment method where the elements of the moment method matrix are calculated in the spectral domain. In order to avoid numerical problems a modified vector-Legendre transformation and normalized Legendre polynomials are defined and applied to the solution procedure. An approximate method is developed to calculate coupling between basis and test functions located on different patches. A laboratory model is built to test different configurations of patches and to validate the calculated results.

In this contribution the generalized exponential matrix technique in spectral domain is adopted for investigating the combined effects of chiral operation in some multilayered bianisotropic substrates, and the mathematical treatment accounts for the most generalized bianisotropic linear media characterized by four 3 x 3 constitutive tensors. Such chiral operation can be realized artificially using a certain number of bianisotropic biaxial or Faraday chiral plates in order that double or three chiralities are formed. Numerical results are presented to demonstrate the influences of changing different variables associated with the reversing of the sign of chirality parameter : the right-and left-handed spiral orientations of the axes of four constitutive tensors as well as the biasing magnetic fields in chiroferrite and chiroplasma substrates on the co- and cross-polarized far-field distribution of a dipole antenna. Some unique relations concerning the main beam direction and the co- and cross-polarized components of the far-field are found and discussed.