David M. Pozar

Design of millimeter wave microstrip reflectarrays

This paper discusses the theoretical modeling and practical design of millimeter wave reflectarrays using microstrip patch elements of variable size. A full-wave treatment of plane wave reflection from a uniform infinite array of microstrip patches is described and used to generate the required patch-design data and to calculate the radiation patterns of the reflectarray. The critical parameters of millimeter wave reflectarray design, such as aperture efficiency, phase errors, losses, and bandwidth are also discussed. Several reflectarray feeding techniques are described, and measurements from four reflectarray design examples at 28 and 77 GHz are presented.

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 Greens 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 reciprocity method of analysis for printed slot and slot-coupled microstrip antennas

A method is presented for the analysis of slot-type discontinuities in microstripline. The approach is based on the reciprocity theorem and uses the exact Greens functions for the grounded dielectric slab in a moment method solution for the unknown antenna currents. The method is applied to two specific geometries: a radiating slot in the ground plane of a microstripline, and an aperture coupled microstrip patch antenna. Results for antenna impedance are compared with measurements, and far-zone patterns are calculated. The method is shown to be quite versatile, and should find application to related problems.

Design of wide-band aperture-stacked patch microstrip antennas

A variation of the aperture-coupled stacked patch microstrip antenna is presented, which greatly enhances its bandwidth. Bandwidths of up to one octave have been achieved. The impedance behavior of this antenna is compared with that of other wide-band microstrip radiators. Matching techniques for the antenna are presented and their relative merits discussed. The effects of varying several key physical parameters of the antenna are investigated, lending some insight into its wide-band operation. Variations on the design such as incorporation of additional patches are also discussed.

Considerations for millimeter wave printed antennas

Calculated data are presented on the performance of printed antenna elements on substrates which may be electrically thick, as would be the case for printed antennas at millimeter wave frequencies. Printed dipoles and microstrip patch antennas on polytetrafluoroethylene (PTFE), quartz, and gallium arsenide substrates are considered. Data are given for resonant length, resonant resistance, bandwidth, loss due to surface waves, loss due to dielectric heating, and mutual coupling. Also presented is an optimization procedure for maximizing or minimizing power launched into surface waves from a multielement printed antenna array. The data are calculated by a moment method solution.

A dual-band circularly polarized aperture-coupled stacked microstrip antenna for global positioning satellite

This paper describes the design and testing of an aperture-coupled circularly polarized antenna for Global Positioning System (GPS) applications. The antenna operates at both the L1 and L2 frequencies of 1575 and 1227 MHz, which is required for differential GPS systems in order to provide maximum positioning accuracy. Electrical performance, low-profile, and cost were equally important requirements for this antenna. The design procedure is discussed, and measured results are presented. Results from a manufacturing sensitivity analysis are also included.

Radiation and scattering from a microstrip patch on a uniaxial substrate

The problem of a rectangular microstrip antenna printed on a uniaxially anisotropic substrate is treated. The effect of anisotropy on the resonant frequency and surface wave excitation of the antenna is considered, and the radar cross section (RCS) of the antenna is calculated. The RCS calculation includes the effect of the load impedance (antenna mode scattering). Results for the resonant frequency of a patch on a uniaxial substrate are compared with measurements, and the RCS of a patch on an isotropic substrate is compared with measurements. The derivation of the uniaxial Greens function in spectral form, the associated moment method analysis for the input impedance and scattering of the microstrip patch, and the expressions for the far-zone fields of a source on a uniaxial substrate are presented.

Scan blindness in infinite phased arrays of printed dipoles

A comprehensive study of infinite phased arrays of printed dipole antennas is presented, with emphasis on the scan blindness phenomenon. A rigorus and efficient moment method procedure is used to calculate the array impedance versus scan angle. Data are presented for the input reflection coefficient for various element spacings and substrate parameters. A simple theory, based on coupling from Floquet modes to surface wave modes on the substrate, is shown to predict the occurrence of scan blindness. Measurements from a waveguide simulator of a blindness condition confirm the theory.

The active element pattern

This review article discusses the use of the active element pattern for prediction of the scan performance of large phased array antennas. The introduction and application of the concept of the active element pattern goes back at least 30 years but the subject is generally not covered in modern antenna engineering textbooks or handbooks, and many contemporary workers are unfamiliar with this simple but powerful idea. In addition, early references on this subject do not provide a rigorous discussion or derivation of the active element pattern, relying instead on a more qualitative interpretation. The purpose of this article is to make the technique of active element patterns more accessible to antenna engineers, and to provide a new derivation of the basic active element pattern relations in terms of scattering parameters. >

Design of wideband circularly polarized aperture-coupled microstrip antennas

Two variations of a novel feeding technique for a wideband circularly polarized aperture-coupled microstrip antenna are described. Prototype designs for wideband linearly polarized elements are first presented, and then used for circularly polarized designs. Techniques used for design of the feed network are detailed, for both series feed and parallel feed versions. Experimental results are shown for each antenna, and results for the two designs are compared. The impedance and axial ratio bandwidths for these antennas are among the best yet achieved for microstrip antenna elements. Several design variations are also discussed. >