D.W. Griffin

Electromagnetic design aspects of packages for monolithic microwave integrated circuit-based arrays with integrated antenna elements

Reliable and cost-effective packaging of monolithic microwave integrated circuits (MMICs) is an important aspect of the design of phased array systems. At millimeter wavelengths, where small dimensions make machining and assembly a complex matter, the interconnections between the modules housing the MMIC components and the antenna elements are a source of unreliability as well as a potential problem in terms of electromagnetic losses. One solution involves the integration of antenna elements onto the MMIC chips. The paper addresses the issues involved in packaging and housing MMIC chips with integrated antenna elements and presents some insights into the electromagnetic design of such packages. >

Analysis of infinite arrays of substrate-supported metal strip antennas

An electric field integral equation method is applied to a metal strip antenna on an electrically thick dielectric substrate of finite size in a uniform infinite array environment. An efficient solution is found using the method of moments. Metal strip folded dipole antennas are analyzed both with and without a coplanar strip feed line, and the effects of the substrate and feed line are investigated. A technique for minimizing the effect of feed line scattering is presented, and arrays of these elements are shown to be capable of good scanning performance over a wide range of beam-steer angles. A phased array simulator experiment is described and the measured results show good agreement with those obtained by analysis. The class of antenna elements studied may be fabricated using monolithic microwave integrated circuit (MMIC) technology, and the analysis described illustrates the expected characteristics for millimeter-wavelength phased arrays of this type. >

On the modeling of metal strip antennas contiguous with the edge of electrically thick finite size dielectric substrates

A solution to the problem of radiation by a narrow metal strip antenna contiguous with the edge of a dielectric substrate is presented where the substrate has parameters such that its electrical thickness is appreciable. Such an antenna may be useful at millimeter wavelengths as an integrated phased array element forming a part of a monolithic microwave integrated circuit (MMIC). A suitable geometry for this application is illustrated and an efficient computational procedure developed. Comparisons with experimental results for the input impedance and far-field radiation patterns show excellent agreement. The influence of the dielectric substrate on the performance of an antenna designed to operate at approximately 60 GHz is discussed. Two examples, the first involving the analysis of a coplanar strip transmission line fed antenna and the second involving impedance matching and control of cross-polarized radiation using a folded strip dipole, are given to illustrate practical applications of the analytical method to design problems. >

Mutual coupling between metal strip antennas on finite size, electrically thick dielectric substrates

An analysis of the mutual coupling between metal strip antennas which are contiguous with the ends of finite-size, electrically thick dielectric substrates is outlined. Such antennas have been proposed as useful monolithic microwave integrated circuit antennas for millimeter-wavelength applications. The analysis presented was verified experimentally, and the results are applied to three-element arrays of metal strip folded dipoles with coplanar strip feed lines. The effect of the electrically thick, finite-size dielectric substrates on the mutual coupling between elements of the arrays is described. >

Monolithic active array limitations due to substrate modes

Monolithic integration of antenna elements, with other passive and active components on a gallium arsenide wafer, to form a phased array antenna assembly has been visualised, in terms of cost-effective performance, as an ideal product for exploiting the millimetre-wave spectrum. In its simplest form it is assumed that the planar array is on one face of the wafer and that the reverse side is a metallised ground plane and heat sink. The design challenge is to accommodate all of the functions to be performed by the array of elements within an area of wafer necessary for the required, antenna directivity. This simple structure appears to be compatible with monolithic technology and with antenna operation that involves electric current type radiating elements in front of a highly conducting reflecting surface. A wafer thickness of about one quarter of the wavelength in the dielectric is indicated and, to avoid grating lobes with a uniform array, an element-to-element spacing of one-half of a free space wavelength is indicated. The required directivity determines the number of elements, the antenna array aperture and the area of wafer needed.

Electromagnetic design aspects of packages for phased array modules that may incorporate monolithic antenna elements

It is pointed out that, where large floor area packages must be used and damping with lossy material is not acceptable, the electromagnetic design of MMIC (monolithic microwave integrated circuit) packages requires careful analysis for the minimization of cavity resonance effects. If monolithic antenna elements are to be used, then aspects of the antenna array design are directly relevant to package design and the suppression of resonances. The following issues are examined: basic package functions and features; MMIC module layout, package shape, and connections; electromagnetic design problems within packages; and the effect of antenna radiation on package design.<<ETX>>

A chip scale approach to monolithic microwave integrated circuit antenna design for millimeter wavelength arrays

A study of a chip-scale approach to MMIC (monolithic microwave integrated circuit) antenna design for millimeter-wave phased arrays has shown that good performance can be obtained from a simple, low-cost antenna element. It has also been shown that the type of arrays under consideration is technologically feasible and offers potential for cost-effective millimeter-wave systems. This chip-scale approach is seen to have several advantages over a wafer-scale approach for directly integrating the antenna element on a MMIC. It is also shown that the substrate extension will have a significant effect on the performance of the metal strip dipole antenna.<<ETX>>

Analysis of the single wire fed dipole antenna

An antenna consisting of a single wire connection from a source to a half-wavelength dipole above a ground plane is studied. With the inherent simplicity of the structure in mind, and the frequent need to connect a dipole antenna to an unbalanced output port (e.g., coaxial or microstrip line), the authors examine the performance of one such antenna and discuss the implications for similar geometry feeds with microstrip patch antennas. Current distribution and radiation patterns are presented. A number of observations on the operation of antennas fed by single wires or probes oriented perpendicular to ground are presented. Although the current distribution on the feed wire appears to be uniform, the description of this wire as a transmission line or nonradiating feed is not correct The mechanism for the radiation from the feed wire is a traveling wave from the feedpoint to the junction with the dipole. Since the resulting radiating structure is asymmetrical, the radiation pattern is also asymmetrical.<<ETX>>

The dielectric resonator power combiner oscillator: a new design for micro- or millimeter-wave development

Field effect type transistor oscillators are formed on the surface of a shielded rectangular dielectric resonator and synchronised via the dielectric LSM-mode resonance. Their combined outputs are coupled via a monolithic-compatible structure into a standard output line or guide. Measured DC-to-RF conversion efficiencies up to 35% validate the new concepts and design method.

A new instrument and technique for diagnosing electromagnetic design problems in microwave module housings and component packages

With the aim of diagnosing electromagnetic (EM) design problems in microwave module housings and component packages, a method of measuring the frequencies at which resonances occur and the distribution of the associated electric field intensity at the inside face of the housing or package lid has been developed and tested. The method does not require modification of the connections to the microwave assembly within the housing. The housing or package only need have a flat lid and that it be left off so that the item under test can be mounted on an equivalent flat plate on the test instrument. The microwave assembly in the housing or package may be operated normally while resonant field distributions are being measured. The prototype instrument yields results that demonstrate the practical application of this measurement assembly as a diagnostic and design development tool for microwave housings and packages of rectangular metal box shape. Resonances in the 8-12-GHz range have been accurately measured and indicate that by scaling dimensions an assembly for use at millimeter wavelengths is feasible.<<ETX>>