Showing papers on "Metamaterial antenna published in 1997"

Off-axis properties of silicon and quartz dielectric lens antennas

Abstract: The theoretical far-field patterns and Gaussian-beam coupling efficiencies are investigated for a double-slot antenna placed off aids on extended hemispherical silicon and quartz lenses. Measured off-axis radiation patterns at 250 GHz agree well with the theory. Results are presented that show important parameters versus off-axis displacement: scan angle, directivity, Gaussicity, and reflection loss. Directivity contour plots are also presented and show that near-diffraction limited performance can be achieved at off-axis positions at nonelliptical extension lengths. Some design rules are discussed for imaging arrays on dielectric lens antennas.

Dual-frequency triangular microstrip antenna with a shorting pin

Abstract: This paper presents a novel design of triangular microstrip antenna with dual-frequency operation. In this design the microstrip patch is short-circuited using a shorting pin and fed by a single probe feed. By varying the shorting pin position in the microstrip patch, such a design can provide a large tunable frequency ratio of about 2.5-4.9 for the two operating frequencies. Experimental results for operating at frequencies of 464 and 2276 MHz are presented and discussed.

Compact triangular microstrip antenna

Abstract: Loading a triangular microstrip antenna with a shorting pin can significantly reduce the antenna size at a given operating frequency. Experimental results of such a triangular microstrip antenna are presented. Variations of the resonant frequency of the triangular microstrip patch with different shorting-pin positions are given, and comparisons of the compact and conventional triangular microstrip antennas are also presented and discussed.

Calculation of radiation patterns of microstrip antennas on cylindrical bodies of arbitrary cross section

Abstract: A simplified approach based on reciprocity is presented to calculate the radiation patterns of microstrip patch antennas or arrays on a cylindrical body having an arbitrary cross section. In this approach, the microstrip patch antennas are characterized using the finite-element method, and their radiation patterns are then calculated using a two-dimensional method of moments in conjunction with the reciprocity theorem. The validity of the calculation is demonstrated by comparison with measured data for a microstrip patch antenna on a circular cylinder attached to a plate. Other numerical examples are also presented to show the capability of the method as well as various effects of the host cylinder on radiation patterns.

A micro-machined microwave antenna integrated with its electrostatic spatial scanning

Abstract: This paper proposes an original actuator designed for microwave applications. A microstrip antenna is patterned on a micromachined fused quartz structure that can rotate to perform the spatial scanning of the emitted microwave beam. Both measured mechanical and microwave characteristics provide this device with the ability to open new application field of MEMS in detection and wireless communication.

Green's function analysis of single and stacked rectangular microstrip patch antennas enclosed in a cavity

Abstract: A rigorous Green's function analysis of rectangular microstrip patch antennas enclosed in a rectangular cavity is described. The formulation makes use of a frequency-independent preprocessing (image extraction) on the spectral domain representation of the Green's function. Measured and simulated results are shown for both single and stacked-patch antennas enclosed in a cavity.

Dual-band dual-polarized microstrip antennas for SAR applications

Abstract: In SAR applications two important frequency bands are the L-band, around 1.275 GHz, and the C-band at 5.3 GHz. The nominal bandwidth at both bands is desirable to be about 100 MHz. The authors report the design and construction of a dual band antenna for SAR in which the L band elements are perforated. The configuration is discussed and measurements of impedance and radiation patterns are given.

An X-band active microstrip reflectarray

Abstract: The design of an amplifier element and an active array are presented for use in an X-Band active microstrip reflectarray antenna. To separate incident and reflected waves, as well as minimise the separation between amplifier elements in the array, a dual feed aperture coupled microstrip patch antenna is used as the radiating element.

Miniaturization on planar antennas with very high permittivity materials

Abstract: Miniaturization on planar printed-circuit antennas by loading the substrate with very high permittivity materials (/spl epsiv//sub r/=38) has been experimentally demonstrated on the planar inverted-F, microstrip, and dielectric resonator antennas. The results show that the size reduction is achieved with the gain comparable with that of the same type of antenna with a low dielectric constant. It is achieved by adding a superstrate of higher permittivity materials (/spl epsiv//sub r/=80).

A Comprehensive Study of Losses in mm-Wave Microstrip Antenna Arrays

Abstract: This paper presents a study of losses in mm-wave microstrip antenna arrays Methods to reduce losses in mm-wave microstrip antenna arrays are described in this paper, Microstrip antennas posses attractive features such as low profile, light weight, small volume and low production cost. In addition,the benefit of a compact low cost feed network is attained by integrating the microstrip feed structure with the radiating elements on the same substrate. However, losses in the microstrip feed network forms a significant limit to the achievable gain in microstrip antenna arrays, Conductor, dielectric and radiation losses are the major components of loss in mm-wave microstrip antenna arrays. Surface wave losses in thin microstrip substrates (compare to wavelength) are usually negligible. At frequencies ranging from 30 to 40 GHz conductor losses are around 0. 15 to 0.2 dB per wavelength, dielectric losses are around 0.04 to 0.05 dB per wavelength for a 50 ohm line on a 10 mil duroid substrate with ?r=2.2. The open nature of the microstrip configuration suffer from radiation originating at various geometrical discontinuities This radiation phenomenon causes additional signal loss in the microstrip antenna feed network. These phenomena become significant in mm-wave microstrip antenna arrays, more bends, T-junctions and other discontinuities are introduced in the feed network and radiation loss increases considerably. As an example radiation loss of a right angle bend in a 50 ohm line on a 10 mil duroid substrate with ?r= 2.2, is 0.1dB at 30GHz and 0.17 dB at 40GHz.

Effects of curvature on the fabrication of wraparound antennas

Abstract: The extension of the microstrip antenna design from planar to cylindrical structures introduces a variety of complications, both in the modeling and fabrication of the structures. Parametric variations due to curvature can be determined theoretically, but it has been found that the process of shaping planar microwave materials into cylinders can cause significant changes to their electrical and physical properties which must be taken into account when designing antenna elements and feed circuitry. The material issues that arise during fabrication of conformal microstrip antennas are discussed in this paper. Several cylindrical microstrip patch antennas were designed using Boulder Microwave Technologies Clementine (R) software. Allowances for the changes that occur in the material as a result of formation were included both as adjustments to the material parameters input into the program, and to the dimensions of the resulting designs. These designs were then fabricated and measured for comparison with simulated results.

A monopole-probe-based quasi-optical amplifier array

Abstract: A quasi-optical amplifier array designed for Ku-band operation is presented. Orthogonal monopole-probe antennas are used to couple the power into, and out from, an array of microstrip-based amplifiers. The array has a gain of 5.4 dB at 16.4 GHz using packaged high electron mobility transistors (HEMT's). This gain is 3.5 dB below the maximum stable gain for this device at this frequency.

A modified transmission line model for cavity backed microstrip antennas

Abstract: Spatial power combining of many MMIC amplifiers at millimeter wave frequencies using a fixed array of microstrip antenna elements places unique demands on the dielectric media. The substrate must be relatively thick to allow space for MMIC placement, must provide rather high thermal conductivity to dissipate MMIC heat, and be of high dielectric constant to shrink the circuit element dimensions. Presently, microstrip antenna models require a low dielectric constant substrate to be valid. This paper presents a modified transmission line model based on the model of Pues and Van de Capelle (1984) which addresses the problems of thick, high dielectric constant substrates as applied to proximity coupled, cavity backed microstrip antenna elements. The goal of the model was to guide the design of a microstrip array antenna suitable for a spatial power combined module.

Improved linear transmission line model for rectangular, circular and triangular microstrip antennas

Abstract: The linear transmission line (LTL) model had been reported for calculating the admittance of a linearly polarized arbitrary shaped patch antenna with symmetrical geometry and constant thickness. In this method, the patch is divided into very small sections along the feed axis length and the width for each section is calculated. However, when this model was simulated and compared for various reported results on rectangular microstrip antennas (RMSA) and circular microstrip antennas (CMSA), an error of around 10% was observed. We propose the following modifications for the reported LTL model. (1) The effective dimensions of the antennas are used instead of physical dimensions to account for the fringing fields. (2) The effective permittivity expression is used to account for the dispersion effect. (3) The characteristic impedance equation was modified to account for the dispersion effect. (4) The effect of probe inductance is taken into account. After incorporating these modifications, the analysis was carried out for the RMSA, CMSA and the equilateral triangular microstrip antenna.

Experimental results of compact microstrip antennas

Abstract: Due to its low profile, the microstrip antenna has found many applications in personal communication systems. And, owing to the miniaturization of communication equipment, designs for reducing the size of the microstrip antenna have received much attention. One of the effective ways to reduce the patch size of the microstrip antenna is to introduce a shorting pin at the edge of the patch. Based on this technique, several novel designs of the compact microstrip antennas are described. The antenna size can be reduced to less than 50% of the size of a conventional microstrip antenna. By incorporating the meandering of the patch, the electrical length of the patch can be further increased. The characteristics of such compact microstrip antennas are experimentally studied. Comparisons between the compact and conventional microstrip patch antennas are also given.

A 20 GHz active integrated multilayer microstrip patch array for portable communication terminals

Abstract: This paper presents a multilayer microstrip array architecture utilizing electromagnetic coupling to reduce feed network complexity, device integration to improve noise performance, and bias integration for simplicity.

Frequency Doubling Integrated Push-Push Active Microstrip Transponder

Abstract: A novel frequency doubling active microstrip antenna transponder circuit incorporating two in-house designed monolithic microwave integrated circuit (MMIC) amplifiers is presented. As well as receiving the input signal, the receiving microstrip antenna also divides the input power into two equal parts and produces phase shift of 180° between two outputs. The outputs are fed to two non-linearly biased MMIC amplifiers which are connected so that the first harmonic power adds while the fundamental is suppressed. The transponder circuit responds to an input signal at 10 GHz. The experimental results achieved from the transponder circuit are presented in the paper.

Resonance and radiation of cylindrical triangular microstrip antennas

Abstract: The characteristics of cylindrical microstrip antennas with triangular patches are studied theoretically and experimentally. The fundamental mode (TM/sub 10/ mode), having a broadside radiation pattern, is studied. A full-wave approach for the analysis of the cylindrical triangular microstrip antenna is applied, and the resonance frequency, input impedance, and far-zone radiated fields are formulated. Numerical results are calculated and an experiment is also conducted to verify the theory. A comparison of the antenna characteristics with those of the rectangular and circular patches is also given.

An enhanced microstrip patch radiating element

Abstract: A compound radiating element consisting of a rectangular microstrip patch plus two parasitically-excited wire monopoles is examined both theoretically and experimentally. The wires are located adjacent to the patch along its centerline in the E-plane. The overall radiation pattern of the element is calculated and found to exhibit beam narrowing and enhanced directivity for proper choice of the monopole height and spacing. Experimental pattern measurements were made and are in essential agreement with the predictions of the theory.

A leaky transmission line method for the analysis of the microstrip line traveling wave antennas

Abstract: We present a numerically efficient and fast technique which can be used for design and optimization of traveling wave radiating structures. This technique is similar to the leaky cavity method which has successfully been applied to the analysis of the microstrip patch antennas (Lo et al. 1979). It is based on the fact that the traveling wave antennas are essentially leaky wave radiators. The traveling wave RF current over the body of these antennas, which are usually in the form of long transmission lines, radiates electromagnetic power continuously and therefore decreases, in amplitude, exponentially (Nakano and Hirose 1994). In the proposed "leaky transmission line model" for this antenna, the per unit length resistance of the line is modified to include the power lost to the radiation in addition to the other losses.

FDTD analysis of a shorted and truncated microstrip antenna for mobile communications systems

Abstract: In this paper, a shorted and truncated microstrip antenna suitable for mobile communications systems is presented. Full-wave analysis is performed using the finite-difference time-domain method. It has been found that the shorted and truncated microstrip antennas exhibit a very narrow band resonance around 850 MHz when the dimensions of the antenna are chosen properly.

Design of a two-element dual-frequency microstrip array

Abstract: The design of a single-layer dual-frequency rectangular microstrip antenna using a single probe feed has been demonstrated by Chen and Wong (see Microwave Opt. Technol. Lett., vol.11, p.83-4, 1996). In this dual-frequency design, the two operating frequencies are mainly determined from the patch dimensions and the substrate parameters, and the feed position is selected such that the TM/sub 01/ and TM/sub 10/ modes are excited at the first two resonant frequencies. We report the design of a two-element dual-frequency array (for 1.9 and 2.45 GHz) using the single-feed dual-frequency rectangular microstrip patches. Experimental results for the characteristics of such a dual-frequency antenna array are presented and discussed.

A method of implementing a probe for microstrip antennas with subcell spatial adjustment in FDTD

Abstract: A method of implementing a wire with a subcell spatial displacement from the edge of a cell has been described. It is demonstrated successfully by adjusting the matching point of a feeding probe modeled by this method on a microstrip patch antenna designed for the 9 GHz band.