Hybrid-coupled shorted rectangular microstrip antennas

Hybrid-coupled (both gap and direct) shorted rectangular microstrip antennas have been investigated. Only one patch is fed and the other patch is parasitically coupled along the radiating and the non-radiating edges, respectively. Dual frequency and broadband operation has been obtained by optimising the coupling between the two patches through a copper strip     

H-plane coupling between rectangular microstrip antennas

A new model that theoretically characterises mutual coupling effects between two rectangular microstrip antennas is presented. Numerical S-parameter results exhibiting mutual coupling effects are reported.     

A transmission line model for arrays of rectangular microstrip antennas

A very efficient transmission line model for the analysis of arrays of rectangular microstrip antennas is presented. The structure of the model is discussed, and its validity is proved. This is done for the isolated microstrip antenna as well as for the coupling between antennas. Then follows a discussion of the numerical efficiency. And finally a numerical example shows the effect of mutual coupling on the impedance and radiation pattern of a 21 element Chebyshev array at different scanangles.     

Surface wave losses of rectangular microstrip antennas

A closed-form expression is presented for the space wave efficiency of rectangular microstrip antennas. This expression is derived from and compared to numerical results available in the literature. The expression is useful for substrates with relative permittivities between 1 and 12.8 and for the complete range of thicknesses normally used.<>     

E-plane coupling between two rectangular microstrip antennas

A model which theoretically characterises end coupling (E-plane coupling) between two rectangular microstrip antennas is discussed. Computer generated S-parameter results for this particular type of mutual coupling are presented.     

Mutual coupling between cylindrical rectangular microstrip antennas

The effect of curvature and separation on the mutual coupling between probe feed rectangular microstrip antennas printed on a cylindrical surface is studied theoretically and experimentally. To incorporate the interactions between patches through the space wave as well as the surface wave, the rigorous spectral domain approach is adopted. The experiment is performed for the purpose of validation of the theoretical results     

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.     

A new edge extension expression for the resonant frequency of electrically thick rectangular microstrip antennas

A new fringing field extension expression is presented for the resonant frequency of electrically thick rectangular microstrip antennas. The theoretical resonant frequency results obtained by using this new fringing field extension expression are in very good agreement with the experimental results available in the literature.     

An experimental investigation of electrically thick rectangular microstrip antennas

The electromagnetic properties of electrically thick rectangular microstrip antennas were investigated experimentally. Antennas were fabricated with different patch sizes and with electrical thicknesses ranging from 0.03 to 0.23 wavelengths in the dielectric substrate. The resonant frequencies were measured and compared to existing formulas. The bandwidth was calculated as a function of electrical thickness and the antenna radiation patterns were measured.     

Improved cavity model parameters for calculation of resonantfrequency of rectangular microstrip antennas

Models for the resonant frequency proposed by other authors are shown to produce misleading results for frequencies greater than about 3 GHz. However, a cavity model with a novel empirically determined edge extension parameter provides calculated frequencies within 2% of measurements for antennas operating between 600 MHz and 5 GHz     

The radiation from rectangular microstrip antennas mounted on two-dimensional objects

The radiation patterns for a quadratic microstrip antenna mounted on two-dimensional objects, the circular cylinder and the strip, have been calculated using both the transmission-line model and the resonator model. Analytical expressions for the far field are presented, and calculations are compared with measurements. All measurements clearly indicate that the resonator model is better than the transmission-line model in radiation pattern calculations outside the principal planes of the antenna.     

Analysis of dielectric covered infinite array of rectangular microstrip antennas

A method is presented to determine the active input impedance of an infinite array of rectangular patches embedded in a dielectric layer. The reaction integral equation is used to include details of feed structure into the formulation. The matching performance over wide scan angles of the printed antenna with a dielectric cover is studied. The results obtained by the present method are compared with the theoretical and experimental results reported earlier, for an array without a cover layer.     

A study of the effect of the top patch in rectangular dual patch microstrip antennas

A moment method procedure is used to solve the integral equations describing rectangular dual patch microstrip antennas. After checking the accuracy of the procedure by comparing calculated with measured results, it is used to analyse theoretically the effect of the top patch, especially the variation of the impedance curve and the gain of the configuration with two parameters, the distance between the two patches and the size of the top patch. Finally, a first attempt is made to outline a technique for the determination of these two parameters in order to obtain a maximum bandwidth.     

Resonant frequencies of rectangular microstrip antennas with flushand spaced dielectric superstrates

This paper presents a predictive model for the resonant frequencies of rectangular microstrip antennas with flush and spaced superstrates. This closed-form model is suitable for CAD and is directly applicable for the integration of microstrip antennas beneath plastic covers or protective dielectric superstrates in portable wireless equipment. The model utilizes conformal mapping and the concept of equivalent capacitance to determine the effective permittivity of a covered microstrip structure. A comparison between calculated and measured resonant frequencies demonstrates that the model provides less than 1% errors for structures with low relative permittivities (ε _r<3) and slightly higher errors for structures that contain higher permittivity materials. Generally, the model predicts the resonant frequency of a spaced superstrate structure as accurately as possible within the tolerance range of the structure's electrical and physical parameters     

Analysis and design of broad-band single-layer rectangular U-slot microstrip patch antennas

A wide operating bandwidth for a single-layer coaxially fed rectangular microstrip patch antenna can be obtained by cutting a U-shaped slot on the patch. This antenna structure has recently been found experimentally to provide impedance bandwidths of 10%-40%, even with nonair substrates. However, design rules for this antenna have not yet been presented. This paper develops principle design procedures through examination of the structure's multiple resonant frequencies as well as the radiation and impedance properties of different antenna geometries. The approximate design rules are derived by analysis of former experiments, method of moments (MoM) simulations, and measurement results. Simulations and measurements of several antennas designed using these new rules are presented and directions for further study are discussed.     

Multiport network model and transmission characteristics oftwo-port rectangular microstrip patch antennas

A multiport network model for two-port rectangular microstrip patch antennas is introduced. This model is capable of accounting for the feedline-patch junction reactances as well as for the mutual coupling among the edges of the patch, and is used to evaluate two-port transmission characteristics of rectangular patches. The proposed model has been applied to the analysis of rectangular patches used as elements of series-fed microstrip arrays. Results presented show that it is possible to match a two-port patch at the input port and, at the same time, to achieve a specified transmission coefficient to the other port to taper the amplitude distribution of the array appropriately. These experimental results verify the validity of the proposed model and the method of analysis used     

A bandwidth enhancement method for microstrip antennas

Bandwidth enhancement methods for electromagnetically coupled microstrip dipoles are discussed. It is demonstrated that if parasitic metallic strips are incorporated in the structure either co-planar and parallel to the embedded microstrip transmission line open end, or between the transmission line and the microstrip dipole, then substantial bandwidth enhancement results. Experimental verification of this model is introduced for a bandwidth definition based on the frequency range which satisfies a voltage standing-wave ratio (VSWR) < 2 criterion. Also, experimentalbar{E}- andbar{H}-plane patterns verify the theoretical model which accounts for radiation from the microstrip dipole, the parasitics, and the transmission line.     

Electric surface current model for the analysis of microstrip antennas with application to rectangular elements

An approach to the analysis of microstrip antennas which is applicable also to relatively thick substrates using the relevant Green's function is presented. The Green's function is derived and closed form expressions for various antenna characteristics which explicitly take into account the presence of the dielectric material are obtained in terms of the electric surface current density. For rectangular microstrip elements near resonance the current distribution is approximated using lossless transmission line analysis, thus enabling the complete evaluation of the characteristics of the element near resonance. The results obtained in this approach for the radiation resistance, surface wave resistance, radiation pattern, directivity, and bandwidth are presented in a detailed set of graphs for a representative set of parameters.     

腔基微带天线的矢量有限元--边界积分方法分析

该文将矢量有限元——边界积分(Edge-Based FE-BI)混合方法用于腔基微带贴片线的辐射特性分析。分别计算了在无阻抗负载和加有阻抗负载两种情况下的输入阻抗，以此验证了该混合方法的正确性；然后计算了贴片天线表面缝隙部分的场分布，验证微带天线分析模型——传输线模型的合理性；最后计算了E面、H面方向图以及相应的交叉极化方向图。