Analysis and optimized designs are presented of three types of single feed circularly polarized microstrip antennas, namely, a diagonal fed nearly square, a truncated-corners square and a square with a diagonal slot. The Green's function approach and the desegmentation methods are used. The resonant frequencies are calculated for two orthogonal modes which together yield circular polarization. Optimum feed locations are determined for the best impedance match to a 50 \Omega coaxial feed line. Axial-ratio bandwidths, voltage standing-wave ratio (VSWR) bandwidths and radiation patterns are evaluated and verified experimentally.

Analysis and optimized design of single feed circularly polarized microstrip antennas

A method for increasing the bandwidth of microstrip patch antennas by incorporating two additional resonators which are gap-coupled to the radiating edges of a rectangular patch is described. A two-dimensional analysis using Green's function and segmentation method is used for analyzing the proposed antenna configurations. A bandwidth as large as five times a single rectangular patch is obtained in S -band. Changes in the radiation pattern over this wide bandwidth are discussed. Experimental results are in reasonable agreement with the analysis.

Broad-band microstrip antennas using additional resonators gap-coupled to the radiating edges

Publisher Summary This chapter deals with the models currently used to improve the quasistatic approximation of microstrip structures. The chapter presents a brief review of the microstrip fundamentals; a comprehensive account of these dynamical models. A particular model based on the calculation of the electric surface currents in the structure is introduced in the chapter. The Green's functions involved are constructed and numerically evaluated using the exact formulation for dipole potentials in a stratified medium. New evaluation techniques developed for Sommerfeld integrals permit a very accurate computation of Green's functions. Their properties are then extensively discussed; the validity of the quasistatic approximations is checked and the importance of the surface wave is pointed out in detail. Finally, the integral equations for the currents are set up and solved by numerical methods in that also give several practical applications. The chapter concludes the model is that the surface currents on the antenna are directly determined and the near field can then be determined easily, that becomes most important when microstrip structures are utilized as radiators or biological applicators.

A Dynamical Radiation Model for Microstrip Structures

Segmentation method for the analysis of two-dimensional microwave planar circuits is modified by using Z-matrices for the individual planar segments. The proposed method is compared with the previously reported method using S-matrices and is shown to be computationally more efficient.

Segmentation Method Using Impedance Matrices For Analysis Of Planar Microwave Circuits

A study of an arbitrarily-shaped planar circuit is reported. The theoretical background is presented and then a numerical method of analysis is introduced. Experiments show good agreement between the theoretical calculations and the measurements. The examples of applications concern stripline circuits but the method may be also applied to waveguides.

Analysis of an Arbitrarily-Shaped Planar Circuit a Time-Domain Approach

Three principal categories have been known in electrical circuitry so far. They are the lumped-constant (0-dimensional) circuit, distributed-constant (1-dimensional) circuit, and waveguide (3-dimensional) circuit. The planar circuit to be discussed in general in this paper is a circuit category that should be positioned as a 2-dimensional circuit. It is defined as an "electrical circuit having dimensions comparable to the wavelength in two directions, but much less thickness in one direction." The main subject of this paper is the computer analysis of an arbitrarily shaped, triplate planar circuit. It is shown that a computer analysis based upon a contour-integral solution of the wave equation offers an accurate and efficient tool in the design of the planar circuit. Results of some computer calculations are described. It is also shown that the circuit parameters can be derived directly from Green's function of the wave equation when the shape of the circuit is relatively simple. Examples of this sort of analysis are also shown for comparison with the computer analysis.

T. Okoshi

Papers

The Planar Circuit - An Approach to Microwave Integrated Circuitry