Theory and experiment of the hemispherical cavity-backed slotantenna

The hemispherical cavity-backed slot antenna is studied theoretically and experimentally. The exact magnetic field Green's function of the cavity is derived rigorously and expressed in a form convenient for numerical computation. The moment method is used to find the equivalent magnetic current in the slot and, hence, the input impedance of the antenna configuration. The effects of the cavity size, of the slot length, and of the slot offset on the input impedance are studied and very good agreement between theory and experiment is obtained. The variation of the magnetic current around the slot and cavity resonances are discussed. Comparisons between the rigorous solution and the single-mode theory are given and the limitation of the single-mode theory is discussed     

Characteristics of aperture-coupled rectangular dielectricresonator antenna

Theoretical analysis of an aperture-coupled rectangular dielectric resonator antenna is presented. A model based on the modal expansion method and the spectral domain approach is developed. Numerical results for return losses and radiation patterns of the TE₁₁₁^y mode are compared with experimental data available in the literature and reasonable agreement between theory and experiment is obtained. This model is flexible as it enables studies to be made of the effects of parameters such as slot dimensions, slot displacement and stub length on input impedances     

Diffraction coefficients for a slot-excited conical antenna

First-order diffraction coefficients for a slot-excited conical antenna are calculated, beginning with integral expressions for the radiation field. Simple formulas based on these coefficients are presented for the radiation patterns that correctly reproduce the interference structure as well as predict the magnitude of the field down to quite low frequencies. Plots of the diffraction coefficients are given for both symmetric and asymmetric excitation of a circumferential slot. Radiation fields are compared with those obtained by summing the exact normal mode series.     

Analysis of hemispherical cavity-backed slot antenna

The input impedance of the hemispherical cavity-backed slot antenna is investigated theoretically and experimentally. The mode-matching method and moment method are used to find the Green's function of the cavity and the equivalent magnetic current of the slot, respectively. The effects of slot length and cavity radius on the input impedance are studied     

Investigations into a cavity-backed circular-patch antenna

An empirical formula for resonant frequency of a circular cavity-enclosed circular-patch antenna is tested with measured results. The patch miniaturization in the presence of the cavity is proved. Different design curves in terms of resonant frequencies and bandwidth are derived to facilitate antenna design without a priori knowledge of complex numerical techniques. A simple gain formula for a circular-patch antenna is derived and tested against the measured gain data. The results agree very well. The beamwidth, axial ratio, and mutual coupling in the presence of the cavity are investigated.     

Theory and experiment on the annular-ring microstrip antenna

This paper presents a critical and comprehensive account of the theory of the annular-ring microstrip antenna based on the cavity model and compares the theoretical results with measurements. It is found that in the theory, the physical radii must be modified to account for the fringing fields along the edges of the ring. The modifications are necessary not only for improving accuracy but also for the correct identification of the modes. Detailed theoretical and experimental results are given on resonant frequencies, radiation patterns and input impedances. Our results also confirm the various features of the tm ₁₁ and tm ₁₂ modes predicted previously by the vector Hankel transform analysis.     

The input admittance of the rectangular cavity-backed slot antenna

The input admittance of the rectangular cavity-backed slot antenna is investigated. The slot is assumed narrow so that the voltage distribution in its aperture is sinusoidal. Equations which represent the input admittance of this slot, backed by a rectangular cavity in which a single propagating wave is assumed to exist, are given. Calculations based on these representations are compared to available measured data. As the depth of the cavity increased the resonant frequency decreased and the bandwidth became narrower. Input admittance curves as a function of electrical slot length are also presented for several size cavities.     

A cavity-backed dipole antenna with wide-bandwidth characteristics

This communication describes a cavity-backed dipole antenna that has a broad-band VSWR response, unidirectional radiation patterns, and almost constant gain (10.5 pm 1dB) over an operating bandwidth of 1.8: 1. Measured pertinent electrical characteristics are presented.     

The transition field on the surface of a slot-excited conical antenna

A previous derivation of the transition field on the surface of a slot-excited conical antenna is corrected, and the new result as well as the tip-diffraction coefficient are checked by a calculation involving only the exact normal-mode series.     

Radiation characteristics of a cavity-backed cylindrical gap antenna

The input impedance and the equatorial radiation patterns of a VHF cavity-backed cylindrical gap antenna are derived and compared with experiments. The experiments generally support the computations, provided that the gap dimension is neither larger than about 1/100 of a wavelength, nor so thin that mechanical tolerances in the feed design become important. The results show that the tuning, impedance bandwidth, and the radiation patterns of this antenna can be controlled very accurately by adjusting the internal radius and height of the cavity. Salient points of this antenna are its wide-band characteristics (10-percent bandwidth), its pattern circularity, and particularly the fact that it can be made an integral part of a space vehicle.     

Network model for strip-fed cavity-backed printed slot antenna

An equivalent network for the strip-fed cavity-backed slot antenna is derived. The model is based on some physical insight into the problem. The various parameters of the network are derived from the experimental data on the input reflection parameter of the antenna. This model gives an insight into the strip-slot-cavity coupling and hence the working of the structure. It is also useful for predicting the performance of such practical antennas.     

A mathematical model for the impedance of the cavity-backed slot antenna

A mathematical model is derived that relates the impedance of a cavity-backed slot antenna to that of an identical slot which is free to radiate on both sides of a large ground plane. The model, which utilizes empirical constants from a previous experimental investigation, provides a continuously variable function of frequency and cavity depth for the impedance of a cavity-backed slot of fixed length and cavity cross section. This function is then compared with previously found experimental values and two theoretical solutions, one using a variational method and the other using the complex Poynting theorem.     

Analysis of a cavity-backed annular slot antenna with one pointshorted

Analysis of a cavity-backed annular slot antenna with one point shorted is performed experimentally and theoretically. Resonance frequencies, bandwidths, and radiation patterns are studied with respect to slot width, cavity depth, and slot shorting position. In the theoretical analysis, the method of moments is applied to find the magnet current on the slot, and the Green's function for the field inside the cavity has been newly derived. By selecting a slot shorting position, circular polarization, and a bandwidth of more than 10%, the voltage standing-wave ratio (VSWR) ⩽2 for the input impedance is obtained     

加载多层介质谐振器的宽带背腔缝隙天线设计

提出并设计了一种工作于X波段的新型宽带背腔缝隙天线,通过在缝隙外侧加载多层介质谐振器,有效扩展了天线带宽并显著提高了天线增益.设计的天线中心频率为10 GHz,-10 dB回波损耗带宽约为40％;带内增益5～9.5 dBi,比未加载多层介质谐振器的背腔缝隙天线提高2～3 dB.实测结果同设计结果基本吻合,有效验证了该设计的正确性.     

A cavity-backed rectangular aperture antenna with application to a tilted fan beam array antenna

A rectangular aperture of A/sub x//spl times/A/sub y/, cut in the top conducting plate of a triplate transmission line and backed by a cavity, radiates a tilted beam off the direction normal to the aperture. The mechanism of the radiation is explained using the Poynting vector distribution above the aperture and the phase distribution of the electric field over the aperture. The tilt angle is calculated as a function of side length A/sub x/ for a representative value of A/sub y/=18 mm=0.747/spl lambda//sub 12.45/, where /spl lambda//sub 12.45/ is the wavelength at a test frequency of 12.45 GHz. A tilted beam of approximately 27/spl deg/ is realized at A/sub x//A/sub y/=8/9 with a gain of approximately 8 dB. Using this value of A/sub x//A/sub y/, an array antenna composed of rectangular cavity-backed aperture elements is investigated. The array forms a tilted fan beam without phase shifters. The frequency responses of the gain and input impedance are discussed.     

Theory and experiment of a coaxial probe fed hemisphericaldielectric resonator antenna

A hemispherical dielectric resonator antenna fed by a coaxial probe is studied both theoretically and experimentally. The Green's function for the evaluation of the input impedance is derived rigorously and expressed in a form convenient for numerical computations. The method of moments is used to obtain the probe current from which the input impedance of the DR antenna is calculated. Both delta gap and magnetic frill source models are considered. Moreover, the results using a reduced kernel as well as the exact kernel are presented. Both entire basis (EB) and piecewise sinusoidal (PWS) expansion modes are used and the results are compared. The effects of the probe length, feed position, and dielectric constant on the input impedance are discussed. Finally, the theoretical radiation patterns for the first three resonant modes (TE₁₁₁, TM₁₀₁, and TE₂₂₁) of the DR antenna are presented     

Radiation and scattering from ferrite-tuned cavity-backed slotantennas: theory and experiment

A three-dimensional finite-element method hybridized with the spectral/spatial domain method of moments is presented for the analysis of ferrite-tuned cavity-backed slot antennas. The cavity, which is partially filled with magnetized ferrite layers, is flush mounted on an infinite ground plane with possible dielectric or magnetic overlay. The antenna operates primarily in the ultrahigh-frequency band. The finite-element method is used to solve for the electric-field distribution inside the cavity, whereas the spectral-domain approach is used to solve for the exterior region. An asymptotic extraction of the exponential behavior of the Green's function followed by a spatial evaluation of the resulting integral is used to improve computational speed. Radar cross section, input impedance, return loss, gain, and efficiency of ferrite-tuned cavity-backed slots (CBS) are calculated for various biasing conditions. Numerical results are compared with experimental data     

Theory and experiment of circularly polarized dielectric resonator antenna with a parasitic patch

The use of a single parasitic patch for circular polarization (CP) excitation of the dielectric resonator antenna (DRA) is investigated. For demonstration, the technique is applied to the conformal-strip fed hemispherical DRA, excited at the fundamental TE/sub 111/ mode. Using the Green's function approach, the integral equations for the conformal-strip and parasitic-patch currents are formulated by matching the appropriate boundary conditions. The equations are then solved using the method of moments (MoM). In using the MoM, both the rigorous and simplified current expansions are used for the parasitic patch, and their results are compared with each other. In each case, the impedance integrals are evaluated by virtue of newly obtained recurrence formulas and direct analytical integration. Hence, the results can be calculated very efficiently without the need for any numerical integration, which greatly facilitates the numerical implementation. The input impedance, axial ratio, and radiation patterns of the CP DRA are calculated, and the results are in good agreement with measurements.     

Wideband dielectric resonator antenna excited by cavity-backed circular aperture with microstrip tuning fork

A wideband dielectric resonator antenna excited by a circular aperture is investigated experimentally. The aperture is coupled by a microstrip feedline with a microstrip fork-like tuning stub. A backing cavity is placed beneath the stub to block undesirable backside radiation. The return loss, field pattern, and antenna gain of the proposed configuration were measured, and the results are compared with those without the backing cavity.