David Pozar

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• phd
• Professor Emeritus at University of Massachusetts Amherst

The exact radiation quality factor Q of infinite planar dipole arrays on a grounded magneto-dielectric substrate is presented. The radiated power and stored energies are evaluated in terms of Floquet modes and the spectrum of the arbitrary dipole current. The characteristics of Q with respect to geometrical and material parameters are shown. The Q...

The exact stored energy, radiated power, and radiation quality factor of infinite planar phased arrays of dipole elements are presented for configurations in free space, over a ground plane, and on a grounded dielectric substrate. Radiated power and stored electric and magnetic energies are evaluated in terms of the two-dimensional spectral domain...

The energy storage and radiation quality factor of infinite planar phased arrays are studied for several cases of practical interest, including dipole arrays in free space and over a ground plane, as well as more general infinite phased arrays modeled with planar currents that excite only a small number of Floquet modes. The radiation Q is computed...

While the foundations of microwave engineering remain firmly based on Maxwell's equations, the practice of microwave engineering has changed over the last 60 years in terms of an increasing shift to circuit / transmission line theory for the design and analysis of problems of practical importance. This paper will discuss the changing roles of field...

Several fundamental questions about the operation of receiving antennas are addressed, such as ldquoWhy does a receiving antenna scatter an incident field?rdquo and ldquoUnder what conditions does a receive antenna capture all of the available incident power?rdquo A new method is described by which the received power can be maximized for an arbitra...

"This anthology combines 15 years of microstrip antenna technology research into one significant volume and includes a special introductory tutorial by the co-editors. Covering theory, design and modeling techniques and methods, this source book is an excellent reference tool for engineers who want to become more familiar with microstrip antennas a...

For lossless receive antennas, the power absorbed and delivered to a conjugate matched load can be obtained by computing a net power lost within a volume that includes the antenna. Maximum achievable received powers by different planar array configurations were analyzed. It was found that both a grounded dipole array, and an array of electric/magne...

This paper will review previous and recent work on the maximum gain and minimum Q of arbitrary lossless antennas, with the goal of trying to eliminate some of the confusion, incompleteness, and erroneous statements that sometimes occur in the literature. Our attention will primarily focus on the effects of polarization and the presence of TM, TE, o...

This book gives a very thorough and complete exposition of the history, theory and analysis, and practical design of printed reflectarray antennas. It will be useful to both experienced workers in the field as well as to students or engineers new to the subject.

Solutions are presented for the optimal electric field waveforms radiated by an arbitrary ultrawideband (UWB) antenna. Optimization criteria include maximization of the electric field amplitude at a particular time and location, or maximization of energy density over a specified time interval at a particular location. Assuming bandpass signals, con...

Several aspects of the polarization of maximum gain arbitrary directional antennas are discussed. Starting with a general expansion of the fields radiated by an arbitrary antenna into spherical harmonics, each with two orthogonal electric sources and two orthogonal magnetic sources, it is shown that the maximum gain of a circularly polarized antenn...

A low-cost radiometric temperature sensor system is described, with emphasis on the use of a 12.5 GHz near-field focused microstrip array to provide a low-profile compact product suitable for commercial and industrial applications. An overview of the temperature sensor system is given, followed by design details of the focused microstrip array, inc...

The gain bandwidth of a microstrip reflectarray can be substantially improved by replacing the usual layer of near-resonant patches with a simple artificial impedance surface consisting of closely spaced electrically small patches on a grounded dielectric substrate. It is shown that this approach can lead to reflectarray gain bandwidths (1 dB) in e...

The application of ultra-wideband (UWB) technology to low-cost short-range communications presents unique challenges to the communications engineer. The impact of the US FCC's regulations and the characteristics of the low-power UWB propagation channels are explored, and their effects on UWB hardware design are illustrated. This tutorial introducti...

The design of a lightweight, microstripline-fed, proximity-coupled patch array is described. The design of an 8×8 array of microstrip patch elements on a single dielectric substrate with a coplanar microstrip feed network at 3 GHz was considered. The weight of the described antenna structures could be compared to a standard microstrip patch array a...

For original paper see T.N.Chang and Y.C.Wei, ibid., vol.52, p.631-5 (2004).

Focusing on the design of microwave circuits and components, this valuable reference offers professionals and students an introduction to the fundamental concepts necessary for real world design. The author successfully introduces Maxwell's equations, wave propagation, network analysis, and design principles as applied to modern microwave engineeri...

This paper discusses the amount of power, which is scattered and absorbed by a receiving antenna and in particular, whether an antenna can absorb the entire power incident upon it. The absorbed and scattered power from dipole arrays in either free space, or over ground plane is considered. By defining a suitable "aperture efficiency" for the receiv...

It is shown that the dominant factor controlling reflectarray bandwidth is the bandwidth of the radiating element, and that the effect of non-constant path delays over the surface of the flat reflector has little significance unless the aperture is electrically very large and the f/D ratio is small. An example of a polarisation-twist reflectarray u...

It is well known that the active element pattern of a phased array, obtained by driving a single radiating element of the array while all other elements are match terminated, can be expressed in terms of the scattering matrix parameters of the array. It is shown how this relationship can be inverted so that the scattering parameters for all element...

A critical need in the evaluation of an ultrawideband (UWB) radio system is the calculation of the energy link loss between the source at the transmit antenna and the receiver load. While the rigorous calculation of link loss in a wideband pulsed system requires a full transient electromagnetic solution for the transmit and receive antennas, we sho...

Solutions are presented for various optimizations of transient waveforms and signals used in ultrawideband radio systems. These include the transmit antenna generator waveform required to maximize receive antenna voltage amplitude (with bounded input energy), the transmit antenna generator waveform that provides the "sharpest" received antenna volt...

This paper describes a full-wave moment-method analysis of an aperture-coupled microstrip coupler using a resonant cavity (rectangular or circular) between the substrate ground planes. Structures of this type are useful for millimeter-wave integrated circuits and phased arrays, as they allow the use of a relatively thick central ground plane to pro...

This paper describes the design and testing of a prototype dual-band dual-polarized planar array operating at L- and X-bands. The primary objectives were to develop new antenna technology with dual-band and dual-polarization capability in a shared aperture, featuring low mass, high efficiency, and limited beam scanning. The design of a prototype pl...

Microstrip antennas aperture coupled to a grounded coplanar waveguide (GCPW) have been fabricated on a single layer substrate and studied experimentally and theoretically. Through-plated via holes are used to suppress spurious parallel plate modes. Measurements demonstrate that this antenna element has good performance for both bandwidth and radiat...

Both computer power and software capabilities have increased substantially, and there are now a variety of general purpose software packages commercially available for the analysis and design of antennas and microwave components. Before the advent of such software, a common practice in industry and universities was to write custom computer codes fo...

Wireless communication is one of the most exciting areas of electrical engineering today, and antennas and RF devices are often the key components that control overall performance. applications such as cellular and PCS telephony, DBS, GPS, LMDS, WLBNs, VSATs, and LEO satellite systems comprise a US market that is currently in excess of $100B. World...

Spaceborne synthetic aperture radar antennas have many special electrical requirements, such as operation at multiple frequencies with multiple polarization ability, with fairly wideband operation being required at these frequencies. They are also required to be electrically large, giving rise to issues such as low mass, easy and reliable deployabi...

This paper describes a microstrip reflectarray antenna designed to produce a shaped-beam coverage pattern using phase synthesis. The concept is demonstrated with a Ku-band linearly polarized reflectarray designed to provide coverage of the European continent and measured results are compared to those obtained for a previously designed shaped-reflec...

A novel printed antenna element capable of providing dual polarised operation over two widely separated frequency bands is described. The element consists of a perforated proximity-fed microstrip patch antenna operating at the lower frequency, layered over a subarray of aperture coupled microstrip elements operating at the upper frequency. Results...

The hybrid method of moments (MoM)/Green's function method technique is applied to infinite periodic printed antenna arrays containing dielectric inhomogeneities. The solution uses an integral equation for an infinite periodic printed array on or over a homogeneous dielectric substrate, coupled with equivalent volume polarization currents for diele...

The design advantages provided by aperture-coupled microstrip patches can be very useful in wireless communications applications. A way to improve the front-to-back ratio is to place a microstrip antenna element behind the aperture as a reflector. Proximity coupling between the feed line and the reflecting element is negligible due to the thick foa...

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...

This paper discusses various methods of implementing a shared-aperture dual-frequency dual-polarized array antenna for spaced-based synthetic aperture radar (SAR) applications. After evaluating the use of several potential array architecture concepts and radiating elements, a design using interlaced C-band microstrip patches and X-band printed slot...

This paper will describe the development of a dual-frequency SAR array operating in the L and C bands, with dual linear polarization capability in both bands. This array shares the same radiating aperture for both bands and both polarizations, resulting in the smallest possible aperture area for a given gain specification. A critical constraint in...

Microstrip reflectarrays offer a flat profile and light weight, combined with many of the electrical characteristics of reflector antennas. We describe the use of crossed dipoles as reflecting elements in a microstrip reflectarray. The theory of the solution is described, with experimental results for a 6" square reflectarray operating at 28 GHz. T...

Microstrip reflect arrays offer a flat profile and light weight, combined with many of the electrical characteristics of reflector antennas. Previous work [1]-[7] has demonstrated a variety of microstrip reflect arrays, using different elements at a range of frequencies. In this paper we describe the use of crossed dipoles as reflecting elements in...

The feasibility and performance of an aperture-coupled cavity-fed microstrip patch antenna and an aperture-coupled cavity antenna are demonstrated using reciprocity and moment method analyses, followed by practical design guidelines and equivalent circuit models. Each antenna incorporates a thick ground plane that can be useful as a heat sink for a...

An E-plane aperture coupled microstrip patch array antenna is presented which incorporates novel microstrip reflector elements in its design. These elements provide a significant reduction in back radiation levels over a bandwidth in excess of 20%. Design considerations for the array elements are given and radiation patterns for the microstrip elem...

First Page of the Article

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-pr...

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 patte...

The analysis presented is capable of treating perturbations to either the excitation or the geometry of an infinite periodic array. It is based upon the solution to the perfectly periodic array, and therefore is best suited to problems having relatively localized perturbations to perfect periodicity. It is numerically efficient, becoming more compu...

A planar lens antenna based on aperture coupled microstrip patch elements with stripline delay lines is described. Features of this design are discussed, and results for transmission coefficient magnitude against frequency are presented. The background for the development of this lens configuration is discussed in terms of a natural progression fro...

An aperture coupled stacked patch microstrip antenna is presented which is capable of operating over a bandwidth in excess of 50%. Measured and predicted impedance behaviour and gain over the band are given. Other important factors such as surface wave efficiency and back radiation levels are presented

While it is often desirable to select planar antennas and circuitry for their advantages in terms of cost, low-profile, and compatibility with microwave integrated circuits, there are still many applications where it is necessary to combine such components with rectangular waveguides. This is especially true at millimeter wave frequencies, where wa...

Microstrip reflectarrays utilize the advantages of planar antenna technology in providing an alternative to parabolic reflectors. The main barrier to implementing a microstrip reflectarray in many applications where reflectors have traditionally been used is that the gain bandwidth is typically only 5 percent (defined for a 1 dB drop from peak gain...

The orthogonal mode of an aperture coupled rectangular microstrip antenna can be coupled to the aperture-excited mode with coplanar microstrip lines to provide a compact circularly polarised element with a single aperture feed. An equivalent circuit model was developed for the analysis and design of this element, and a working version was used to d...

The reflectarray combines features of reflector and array antennas. Reflectarrays are illuminated by a feed antenna which excites an array of radiating elements comprising a reflecting surface, and these elements produce a radiated field. Some types of reflectarrays, including the microstrip reflectarray, also produce a specularly reflected field c...

The aperture coupled cavity fed patch and the aperture coupled cavity antenna are analyzed. Each geometry incorporates a thick ground plane which may serve as a heat sink for active MMIC circuitry, and as structural support for thin substrates. The presence of the thick ground plane, as well as the aperture coupled feeding scheme, make these antenn...

Electrical Engineering/Antennas and Propagation Microstrip Antennas The Analysis and Design of Microstrip Antennas and Arrays Microstrip Antennas contains valuable new information on antenna design and an excellent introduction to the work done in the microstrip antenna area over the past 20 years. The articles are well-chosen and (are) complete wi...

The excitation of the parallel plate mode in stripline configurations is a serious concern in the design of multilayer feeding networks. Using either probes or slots as means of power transfer between adjacent layers, the parallel-plate is always excited, and to insure its suppression a considerable effort has to be made. This letter presents a new...

Microstrip antenna subarrays, consisting of a central aperture coupled microstrip antenna element feeding additional elements via coplanar microstrip lines, are described along with their relative advantages and a basic design procedure. A five-element microstrip subarray is used to demonstrate the concept, and measured data are compared with desig...

An asymptotic expansion of the microstrip Green's function is used to facilitate a study of mutual coupling between two printed antennas, and coupling versus element separation is presented for substrate parameters of practical interest. For certain substrate parameters, it is found that the magnitude of mutual coupling does not decay monotonically...

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 c...

The feasibility of using a thick ground plane with an aperture coupled microstrip patch antenna while maintaining reasonable antenna performance is demonstrated using moment method and reciprocity analyses in the spectral domain. The thick ground plane, which may serve as a heatsink for active MMIC circuitry, or as a mechanical support for thin sub...

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...

In a great number of microwave applications a highly directive antenna with a main beam scanned to a certain angle is required. To achieve this a certain aperture illumination with progressive phasing is used. The two primary ways to do this are reflectors and arrays. The reflector antenna uses its geometry to create the desired phase across the ap...

The aperture coupled microstrip patch antenna was proposed in Pozar (1985) to alleviate the difficulties of feeding printed antennas operating at millimeter wave frequencies. This geometry has subsequently been analyzed by a number of researchers using various techniques and models. The addition of a thick ground plane to the aperture coupled patch...

In recent years, the rectangular slot has been proposed as a means of power transfer between layers in multilayer printed antennas. Compared to probes, slots reduce fabrication complexity considerably, and allow more flexibility in the design of multilayer configurations. In the past, the aperture-coupled microstrip patch has been analyzed using th...

The authors correct several errors appearing in their paper (see Pozar, IEEE Trans. Antennas. Propagat., vol. 40, p. 1084, 1992). First, the sign assumption for κ in the Green's function is opposite that given in equation (1) for the permeability tensor. The sign of κ is directly related to the polarity of the bias field, and is sometimes defined d...

Printed antennas have become popular as cheap, light-weight and conformal antennas in modern radar, satellite, mobile and personal communication systems. However, the conventional geometries of microstrip patches printed on a single-layered substrate, and fed by a coaxial probe or a microstrip line, do not meet the diverse requirements in advanced...

Aperture coupled microstrip patches have the advantages of more available substrate area for active devices, isolation of the feed structure from the radiating elements, and the elimination of connections through the substrate layers using vias. The authors presented a variation to the single patch design, where four additional patches are added to...

The problem of modular design of multilayer printed arrays is addressed. The use of slot as a means of power transfer between layers makes the use of multilayer feeding networks attractive. Four different transitions are analyzed using the moment method in the spectral domain. A typical equivalent circuit valid for all these transitions is used, an...

A graph describing the directivity of an omnidirectional antenna versus the half-power elevation-plane beamwidth is presented. This data has been calculated assuming a sin/sup n/ theta elevation-plane pattern. A closed-form curve-fitted approximation for this relationship is also presented.< >

The finite-difference-time-domain (FDTD) technique is applied to two-dimensional periodic problems in scattering and radiation. This method allows the direct and complete treatment of periodic scatterers and arrays having transverse or longitudinal inhomogeneities, and several examples are presented to illustrate the versatility of the technique. T...

Microstrip reflectarrays typically use tuning stubs on each element to adjust the phase of the reflected field. The authors describe a new approach in which the need for tuning stubs is eliminated and phase control is achieved simply by adjusting the resonant length of the patch elements. The advantages of this approach are described, as are a full...

A ferrite superstrate or radom layer can be used to control the radiation, reception, and scattering from a printed antenna or array by applying a DC magnetic bias field in the plane of the ferrite, orthogonal to the RF magnetic field. By properly choosing the bias field, the effective permeability of an extraordinary plane wave propagation in the...

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 paral...

In order to to study the effect of random positioning errors in an infinite array an impedance analysis must be done. The authors present the first solution and data for the expected value of the input impedance of an infinite array of printed dipoles on a dielectric substrate. Theory is introduced, and results for several cases are presented and d...

The authors describe three different design approaches for series-fed broadside microstrip arrays having a center feed point. The first array uses a standard standing-wave feed design, but with the novel feature that the patch width is varied in order to obtain the desired amplitude taper. The second design also uses patches of varying widths, but...

A microstrip antenna composed of parallel dipole resonators of different lengths fed by a rectangular slot cut in the ground plane of a microstrip line is analyzed using an integral equation technique solved in the spectral domain using the Galerkin method of moments. Multifrequency operation of this antenna is demonstrated using two different conf...

Results are presented for isolated microstrip antennas and infinite arrays of microstrip antennas printed on chiral substrates, computed from full-wave spectral domain moment method solutions. Data for resonant length, impedance, directivity, efficiency, cross-polarization level, and scan performance are compared to results obtained for a dielectri...

Radiation and scattering characteristics of microstrip antennas and arrays printed on ferrite substrates with a normal magnetic bias field are described. The extra degree of freedom offered by the biased ferrite can be used to obtain a number of novel characteristics, including switchable and tunable circularly polarized radiation from a microstrip...

Microstrip antenna array design is a rich and fascinating subject that has attracted the interest of antenna practitioners and analysts alike. This is partly due to the fact that microstrip arrays have a number of practical advantages, such as low cost, light weight, and conformability, that make them preferred over other antenna types for a variet...

The analysis and scanning characteristics of several different types of infinite arrays composed of subarrayed printed dipole and microstrip patch elements are presented. The analysis is based on full-wave moment method theory, and includes mutual coupling between elements in the subarray as well as between subarrays. The effect of subarraying on s...

For Part I, see ibid., vol.40, no.5, p.469-481 (1992). The general analysis of part I is applied to several practical geometries of multilayer/multifeed printed antennas. These examples include a dual-feed circularly polarized geometry; a stacked patch geometry; a stripline-aperture coupled geometry with a radome; an open-end proximity-coupled patc...

A general solution is given for a class of printed antenna geometries composed of multiple dielectric layers or ground planes, radiating patches, dipoles, or slots, and an arbitrary configuration of multiple transmission lines proximity-coupled or aperture-coupled to the radiating elements. The solution uses a full-wave spectral-domain moment metho...

It is shown that the radar cross section (RCS) of a microstrip antenna can be significantly reduced over a broad frequency range by using a ferrite substrate biased to a cutoff state. When unbiased, the antenna operates in its usual fashion, with relatively large RCS peaks at frequencies corresponding to the resonances of the patch element. When th...

Several techniques are presented for feeding microstrip antennas with RF-modulated lightwave signals via an optical fiber. Lightwave-to-RF conversion is performed in a module containing a photodiode, RF circuitry, and a microstrip antenna element. Three different transmitting configurations at microwave frequencies were designed and tested: passive...

Microstrip antennas have been one of the most innovative topics in antenna theory and design in recent years, and are increasingly finding application in a wide range of modern microwave systems. This paper begins with a brief overview of the basic characteristics of microstrip antennas, and then concentrates on the most significant developments in...

The problem of multilayered printed antennas is addressed. A conventional corporate feeding network has a crowded layout which can lead to coupling between the network and radiating elements. Furthermore, a conventional feeding network is asymmetric, affecting directly the array performance. It is shown that these problems can be avoided by using a...

The author presents an analysis of infinite arrays composed of arbitrary subarrays of microstrip antenna elements and presents results of the application of this theory to several cases of practical interest. A full-wave moment method solution is used, which includes mutual coupling between elements in the subarray as well as the coupling between s...

The performances of microstrip antennas printed on either normally biased ferrite substrates or chiral substrates are compared. Results for both isolated elements and infinite arrays are presented. For the ferrite substrate case, several new and interesting results are discussed, including the generation of circular polarization using a single feed...

K -band aperture-coupled stacked microstrip antennas are studied and numerical results based on the solution of integral equations solved in the spectral domain are presented. The effects of varying physical parameters of the structure are investigated with the goal of designing millimeter-wave wideband microstrip antennas. Antennas with different...

A frequency-selective surface based on the aperture coupled microstrip is presented. This surface has a narrow bandpass response useful for building radomes with low out-of-band radar cross section (RCS). The analysis employs the spectral domain moment method. The design criteria and a simple lumped element model are derived and presented. Experime...

Input impedance and radar cross section results for probe-fed single rectangular and circular microstrip patch elements obtained using an accurate and efficient numerical model are presented. The model uses a full-wave Green's function/Galerkin solution in which the connection of a vertical probe feed to the patch is rigorously included in the anal...

A general full-wave solution to arbitrary multilayer geometries of printed antennas and arrays coupled to multiple printed feed lines has been developed. It uses spectral-domain Green's functions for multilayer substrates to account for the substrate layering of the printed antenna, and a newly developed generalized multiport reciprocity analysis t...