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1.
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  相似文献   

2.
Esko Alanen 《电信纪事》1991,46(3-4):163-170
The exact image theory is applied to obtain the exact field distribution of an annular microstrip radiator over a two layered biological medium. First, the image functions for the three layer structure (substrate-skin-fat) are derived by expanding the Fourier domain reflection coefficient into a sum of pole terms, known also as the Mittag-Leffler expansion. Secondly, the current distribution on the strip is solved by using the Galerkin’s method with continuous trigonometrical basis functions. In order to reduce the focus of the antenna, the dependence of the focus size on the radius of the antenna is calculated.  相似文献   

3.
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.  相似文献   

4.
A novel approach for impedance matching of probe-fed, stacked microstrip patch antenna elements is demonstrated. The matching structure is compact and enables more than doubling of the operational bandwidth. A circuit model for the feeding probes is developed and its impact on antenna impedance is discussed.  相似文献   

5.
Dubost  G. 《Electronics letters》1983,19(18):737-739
Using electric and polarisation current distributions, known from transmission-line-model analysis, we have determined the far field radiated by a short-circuited rectangular microstrip antenna acting at a quarter-wavelength resonance. An experimental verification for such a radiating strip wrapped around a conducting cylinder is given.  相似文献   

6.
Assuming a quasi-TEM mode of wave propagation and using a conformal transformation technique, accurate and simple analytic expressions for the characteristic wave resistance and the effective dielectric constant of the microstrip dipole antenna in the mixed dielectric medium have been derived. The theoretical values are in close agreement with the experimental results.  相似文献   

7.
The slot microstrip antenna is used as a folded slot dipole symmetrically fed across a gap by means of a strip line. A theoretical model equivalent to several lossy transmission lines had been described previously to explain the bandwidth and the radiation admittance. The theory is improved when coupling between the two equivalent radiating lines of every slot is taken into account, and explains a fourth resonance near the third one, which had been measured on several models. Theoretical results and experiments are in good agreement. They are radiation admittance in a wide frequency band, current distribution along each slot and radiation patterns.  相似文献   

8.
Broadband probe-fed notched plate antenna   总被引:1,自引:0,他引:1  
A probe-fed notched plate antenna for improving the impedance bandwidth is experimentally presented. The notched square plate is suspended above the ground plane. The spacing between the plate and ground plane is ~7% of the operating wavelength. The plate antenna is diagonally fed by a coaxial probe. Measured results show that the notches at the plate function as the reactive loading and, as a result, the enhanced impedance bandwidth reaches the order of 20% without any parasitic elements. The effects of geometric parameters of the plate antenna on the bandwidth are discussed. The radiation patterns and the achieved gains are also examined experimentally  相似文献   

9.
The cross-polarization characteristics of a probe-fed hemispherical dielectric resonator antenna are studied theoretically. The mode-matching method was used to find the exact antenna Green's functions rigorously. The effects of the dielectric constant, probe length, and probe displacement on the cross-polarization level are examined  相似文献   

10.
Phased arrays of probe-fed stacked microstrip patches   总被引:1,自引:0,他引:1  
This paper presents calculated and measured results for infinite phased arrays of probe-fed stacked rectangular and circular microstrip patches. A numerical model is described that is based on a rigorous Green's function/Galerkin solution. In this solution, the connection of one or more vertical probe feeds to each patch is accurately modeled using a special attachment mode basis function, which is derived from the corresponding cavity model solution. Numerical results for both linearly and circularly polarized arrays are obtained. Measured results from a waveguide simulator are also presented and used to validate the numerical model  相似文献   

11.
A new compact microstrip antenna element is analyzed. The analysis can accurately predict the resonant frequency, input impedance, and radiation patterns. The predicted results are compared with experimental results and excellent agreement is observed. These antenna elements are more suitable in applications where limited antenna real estate is available  相似文献   

12.
A method has been previously developed for the computations of mutual coupling between the usual rectangular printed antennas. In the letter the short-circuited antennas with three magnetic walls and an electric wall (Fig. 2) are investigated. Using the cavity model with hybrid boundary conditions (magnetic wall and electric wall) and the equivalence theorem, the problem is reduced to the interactions of two U-shaped magnetic currents. Theory and experiment are in very good agreement.  相似文献   

13.
In the present paper the analysis of a gap-coupled microstrip antenna (GCMSA) is carried out using the circuit concept and consequently various parameters such as input impedance, VSWR and return-loss are investigated for different air gap lengths. It is observed that the resonant frequency of the antenna with different substrates depends on the gap length. The gap-coupled antenna behaves as an RL network below the resonant frequency for all substrate materials and gap lengths, whereas the antenna behaviour above resonance is like an RC network. It is further observed that the resonant frequency of the GCMSA decreases with increasing gap length.  相似文献   

14.
Guo  Y.X. Luk  K.M. Lee  K.F. 《Electronics letters》2000,36(4):289-291
An experimental demonstration of a compact dual-band patch antenna designed using slot-loaded and short-circuited size-reduction techniques is presented. By controlling the short-plane width, the two resonant frequencies, f10 and f30, can be significantly reduced and the frequency ratio (f30/f30) is tunable in the range ~1.6-2.2  相似文献   

15.
Broadband probe-fed patch antenna with a W-shaped ground plane   总被引:1,自引:0,他引:1  
A new design of a broadband probe-fed patch antenna with a W-shaped ground plane is presented. The W-shaped ground plane is obtained by bending the conventional planar ground plane into an inverted V-shape, seen in the resonant direction of the patch antenna and then adding proper flanges at the two straight edges of the bent ground plane. The proposed design is applicable to the patch antenna with a planar radiating patch with a thin air substrate. With the use of the proposed W-shaped ground plane, the required probe-pin length in the substrate remains small, although the effective substrate thickness is significantly increased, resulting in a much wider operating bandwidth. Also, by choosing proper dimensions of the W-shaped ground plane, the antenna gain for frequencies over the obtained wide bandwidth is enhanced, compared to the conventional patch antenna with a planar ground plane. In addition, the cross polarization is also reduced for the proposed design and the cross-polarization level (XPL) in the H-plane pattern can even be better than that of a conventional probe-fed patch antenna with a thin air substrate  相似文献   

16.
Murakami  Y. Sekine  S. Shoki  H. 《Electronics letters》2002,38(25):1619-1621
The analysis of a cross-slot-coupled circular microstrip antenna is presented. The approach is based on the reciprocity theorem and the exact Green's functions for the antenna structure. The equivalent circuit of the antenna was obtained. The calculated results for antenna input impedance were compared with the measured data.  相似文献   

17.
A wideband probe-fed circularly polarised circular loop antenna is presented. The wideband performance is achieved by introducing a parasitic loop inside the original loop that is driven by a feed probe. It is found that the 2 dB axial ratio bandwidth can be increased from 6% for a single circular loop to 16% by the introduction of a parasitic loop.  相似文献   

18.
The circular microstrip antenna element is formed by a radiating disk closely spaced above a ground plane. It is modeled as a cylindrical cavity with magnetic walls which can be resonant in the transverse magnetic (TM) modes. The far fields and the radiation conductances for different mode structures have been calculated assuming a magnetic line current flowing along the perimeter of the disk. The directivity of a disk antenna excited in the dominant mode is between 4.8 dB and 9.9 dB, depending on the size. Losses, due to imperfect supporting dielectrics and to the finite conductivity of the conductors, have been derived by means of a perturbation technique. Graphs are given for design purposes showing the input impedance, theQfactor, and the radiation efficiency at resonance for different modes and thicknesses. The air-filled microstrip antenna has the highest efficiency and the broadest bandwidth at a given resonant frequency.  相似文献   

19.
A new analytical expression for the input impedance of a patch antenna has been obtained based on the Green function approach which includes the effect of the feed current density vector. The feed reactance is inbuilt and the method is numerically very efficient with a minimal computational requirement  相似文献   

20.
Analysis of an aperture coupled microstrip antenna   总被引:7,自引:0,他引:7  
A microstrip patch antenna that is coupled to a microstripline by an aperture in the intervening ground plane is analyzed. Coupled integral equations are formulated by using the Green's functions for grounded dielectric slabs so that the analysis includes all coupling effects and the radiation and surface wave effects of both substrates. A Galerkin moment method solution of the coupled integral equations agrees quite well with measured data. Design data are contained in parameter studies, many of which are verified by experimental results.  相似文献   

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