Input impedance of a circular microstrip disc antenna using mode matching

A model is developed to calculate the input impedance of a coaxially fed circular microstrip disc antenna. A mode-matching approach is used, which makes it possible to include the effects of modes other than the dominant mode. Comparison is made with measured results taken over the frequency range 8 GHz to 11 GHz.     

Analysis of Gunn integrated annular ring microstrip antenna

The analysis conducted on Gunn integrated annular ring microstrip antenna and evaluation of various parameters such as input impedance, voltage standing-wave radio voltage standing wave ratio (VSWR), return loss, bandwidth, radiation pattern, beamwidth, etc., as a function of bias voltage and threshold voltage reveals that the Gunn loaded patch offers wider tunability, better matching, enhanced radiated power as compared to the patch alone. Bandwidth of the Gunn loaded patch improves to 11.07% over the 7.9% bandwidth of the patch whereas the radiated power is enhanced by 3.7 dB as compared to the patch.     

Size reduced meander line annular ring microstrip antenna

A method to reduce the size of the annular ring microstrip antenna is presented. A parametric study shows a very large size reduction can be achieved.     

Input impedance of a probe-fed stacked circular microstrip antenna

The input impedance of a microstrip antenna consisting of two circular microstrip disks in a stacked configuration driven by a coaxial probe is investigated. A rigorous analysis is performed using a dyadic Green's function formulation whereby the mixed boundary value problem is reduced to a set of coupled vector integral equations using the vector Hankel transform. Galerkin's method is used in the spectral domain, using two sets of disk current expansions. One set is based on the complete set of orthogonal modes of the magnetic cavity, and the other uses Chebyshev polynomials with the proper edge condition for the disk currents. An additional term is added to the disk current expansion to model the current properly in the vicinity of the probe/disk junction. The input impedance of the antenna, including the probe self-impedance, is calculated as a function of the layered parameters and the ratio of the two disk radii. Disk current distributions and radiation patterns are presented. The calculated results are shown to be in good agreement with experimental data     

INPUT IMPEDANCE OF MICROSTRIP ANTENNA WITH THICK MULTILAYER SUBSTRATE

A method has been devised to analyze multilayer electrically thick circular mi-crostrip antenna excited by a probe.The current on the probe is taken to be uniform.Thismethod was verified by analysis and experiment of an electrically thick circular microstrip an-tenna with an air gap.Based on the free space electric dyadic Green's function,the field expressionof an horizontal electric dipole(HED),which is located at any point of the multilayer media andpoints in any direction,has been derived.By using this field expression and the Richmond re-action equation,an integral equation in terms of electric current on the patch is formulated.Byproperly choosing current expansion modes,this method can be used for an electrically thick mi-crostrip antenna.The theoretical results agree very well with experimental data for an electricallythick circular microstrip antenna with an air gap.     

Input impedance of rectangular patch antenna fed by microstrip line

A simple full-wave method for analysing rectangular microstrip antennas is presented. The problem of voltage term calculation is elucidated in the case of the microstripline-fed antenna. A new model for calculating the voltage term is proposed and compared to the other two models taken from the literature.<>     

Input impedance of a probe-fed circular microstrip antenna with thick substrate

A method of computing the input impedance for the probe fed circular microstrip antenna with thick dielectric substrate is presented. Utilizing the framework of the cavity model, the fields under the microstrip patch are expanded in a set of modes satisfying the boundary conditions on the eccentrically located probe, as well as on the cavity magnetic wall. A mode-matching technique is used to solve for the electric field at the junction between the cavity and the coaxial feed cable. The reflection coefficient of the transverse electromagnetic (TEM) mode incident in the coaxial cable is determined, from which the input impedance of the antenna is computed. Measured data are presented to verify the theoretical calculations. Results of the computation of various losses for the circular printed antenna as a function of substrate thickness are also included.     

Input impedance of rectangular microstrip patch antenna withiso/anisotropic substrate-superstrate

The modified Wolff model (MWM), which is an improved version of the cavity model, is presented to compute the resonance frequency and input impedance of a rectangular microstrip patch antenna under the isotropic/anisotropic substrate-superstrate configuration. The model has accuracy better than 1.5% for both the resonance frequency and resonant resistance, as compared against the results of the method of moments (MOM) and experimental results     

Polarization-agile microstrip antenna array using a single phase-shift circuit

A novel polarization-agile microstrip antenna array is proposed, in which the polarization agility from linear to circular polarization for the whole array is realized easily by controlling a single phase-shift circuit. Using the corner-fed square patch element, a new 16 element dual-polarized array with high isolation and low cross-polarization is designed and analyzed by the extended multiport network method. A special FET phase shifter circuit is created, where 0/spl deg/ or 90/spl deg/ phase shift between dual ports is electrically switched. Experimental results are presented to verify the theory, and measured circularly-polarized radiation patterns show a boresight axial ratio of 0.5 dB. Another experiment that connects a low noise amplifier together with the phase-shift circuit is also introduced, realizing both polarization agility and power amplification with one active circuit.     

Miniaturised microstrip bandpass filter using stepped impedance ring resonators

A novel microwave bandpass filter using microstrip stepped impedance ring resonators is reported. The new filter has the advantages of compact size together with sharp rejection of outbands. A two-pole microstrip bandpass filter of this type has been implemented and examined, theoretically and experimentally.     

L-probe proximity-fed annular ring microstrip antennas

A broadband single-layer annular ring microstrip antenna fed by an L-shaped probe is studied. It achieves, for the TM₁₁ mode, an impedance bandwidth of about 24% [standing wave ratio (SWR) ⩽2], a 3-dB gain bandwidth of 33%, and a maximum gain of 7.5 dBi. For the TM ₁₂ mode, an impedance bandwidth of about 27% (SWR ⩽2), a 3-dB gain bandwidth of 15.5% and a peak gain of 10.3 dBi are obtained. A foam substrate of thickness around 10% of the operating wavelength in free-space is used as the supporting substrate. The far-field radiation patterns are stable across the passband     

Asymmetrically loaded annular ring antenna

A numerical model for resonant frequency using asymmetric loading is presented using cavity model. In asymmetric loaded antenna, the posts are not equispaced on annular ring antenna and resonant frequency is independent of the angular location of posts. The posts are located away from the centre of patch. The diameter of post is thin as compared to the diameter of annular ring antenna. The first few dominant modes calculated for asymmetric loading are compared to symmetric loading where the posts are to be located at specific angular locations. The theoretical model is compared to the simulated results of IE3D based on Method of Moments. The numerical model developed can also be verified further by the full wave analysis.     

Input impedance of arbitrarily shaped microstrip antennas

Deals with the analysis of arbitrarily shaped microstrip antennas. A powerful and flexible technique is obtained by combining a mixed potential integral equation, successfully used for rectangular patches, with a method of moments, using a division of the patch into triangular cells and overlapping basis functions, defined over cell couples. The resulting computer algorithm is validated by comparing its predictions with the measurements obtained from an equilateral triangular patch     

Input impedance of corner-fed patch antenna for circularpolarisation using desegmentation technique

New analytical expressions have been obtained based on the Green function approach to determine the input impedance of a corner-fed circularly polarised patch antenna using the desegmentation technique. Such an antenna can be used for a LAN or for microwave tags in transport systems     

Broadband proximity fed ring microstrip antenna arrays

Various gap-coupled array configurations of ring microstrip antennas and rectangular slot cut ring microstrip antennas with proximity fed slot cut ring microstrip antenna for larger bandwidth and gain are proposed. The rectangular slot in ring patch reduces its orthogonal TM₀₁ and TM₀₂ mode resonance frequencies and along with TM₁₀ modes of fed and parasitic ring patches, yields broadband response. The gap-coupled configuration with ring patch and slot cut ring patch yields bandwidth of nearly 430 MHz with broadside radiation pattern and peak gain of more than 9 dBi. By gap-coupling ring patches along all the edges of proximity fed pair of slot cut ring patch, a 3 × 3 ring microstrip antenna array is realized. It yields bandwidth of more than 460 MHz with peak gain of more than 10 dBi. To further improve upon the bandwidth, a 3 × 3 array of ring patches in which rectangular slot is first cut on the edges of ring patch which are gap-coupled along x-axis and further cut inside the patches which are gap-coupled along x and diagonal axes, is proposed. Both of these configurations yield bandwidth of more than 500 MHz (>45%) with a peak gain of around 10 dBi.     

The mode features of an annular sector microstrip antenna

A rigorous analysis of the features of the modes of an annular sector printed microstrip antenna is presented. General expressions for its radiation field are derived by using the cavity model. The expressions are used to study the radiation patterns, radiation peak in the broadside direction, and beamwidth of different structures for various sector angles, widths, and modes of excitation. This includes the special cases of quarter-, half-, three-quarters-, and ideal-gap open-ring structures. Compared to a closed ring, the results indicate that the TM₁₂ mode is superior to the TM₁₁ mode with regard to the radiation properties in the annular sector as its angle approaches 2π     

Input impedance and mutual coupling of rectangular microstrip antennas

A moment method solution to the problem of input impedance and mutual coupling of rectangular microstrip antenna elements is presented. The formulation uses the grounded dielectric slab Green's function to account rigorously for the presence of the substrate and surface waves. Both entire basis (EB) and piecewise sinosoidal (PWS) expansion modes are used, and their relative advantages are noted. Calculations of input impedance and mutual coupling are compared with measured data and other calculatious.     

Input impedance of annular-ring microstrip antennas with adielectric cover

A theoretical and numerical analysis of the annular-ring microstrip antenna with a dielectric cover is performed. The problem is formulated in the Hankel transform domain, taking a coaxial feed into consideration. The integral equations for the surface current density on the patch are derived. Galerkin's method is used to solve for the surface current density, and a stationary formula for the input impedance is obtained. Numerical results showing the effects of a dielectric cover on the TM₁₂ mode of the annular ring are given. It is found that the dielectric cover reduces the resonant frequency, decreases the resonant resistance, and increases the impedance bandwidth     

Microstrip disc antenna with short-circuited annular ring

The addition of an annular short-circuited ring to a microstrip disc has resulted in a novel compact antenna suitable for reflector feed applications. Variations of the ring geometry allow bandwidth extensions up to twice that of the disc, but with some gain penalty. The radiation pattern has good circular symmetry and a reduced crosspolarisation of ?21 dB compared to the isolated disc.