Broad-band gap coupled microstrip antenna

A microstrip antenna with large bandwidth is developed using a parasitic technique. Compared to the available wideband antennas, the proposed antenna structure is very compact and gives a less distorted radiation pattern with frequency. An impedance bandwidth eight times that of a conventional patch antenna of the same size is achieved. The concept of coupled microstrip line model is extended for theoretical interpretation of the impedance loci. The experimental procedure and results are described, and a theoretical analysis is presented     

Circularly polarised aperture coupled microstrip antenna

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 demonstrate the concept. The features of this antenna are compared with several other circularly polarised microstrip antennas     

Aperture coupled microstrip antenna element design

Aperture coupling is investigated as a feed mechanism for microstrip antenna elements. Using modal field expansion, and assuming that coupling is via a magnetic current in the aperture, calculated data on the antenna parameters are obtained. Several samples are manufactured, tested and practical design curves generated at 5.0 and 10 GHz. Good agreement between theory and experiment is obtained. These new results extend the validity of the analysis at high frequencies and will be useful for design and applications involving this type of antenna.<>     

A new aperture coupled microstrip slot antenna

A new aperture coupled design is proposed for microstrip slot antennas to improve their radiation performance. The proposed design is based on a new aperture coupling technique in which the slot is fed by a microstrip line and coupled to several parasitic patch radiators etched on the opposite side from the slot. In contrast to the combination of a slot and a microstrip patch in conventional aperture coupled microstrip antennas, the patches here are employed to reduce the radiation into the half-space that they occupy and increase the radiation in the other half-space. Therefore, the slot antenna can produce radiation patterns with a high front-back ratio. The above objective is achieved by optimizing standing wave distributions of the aperture electric field in the slot through the adjustment of the position of the patches along the axis of the slot. In this paper, design considerations are given, and the results are validated by numerical simulations and experimental measurements.     

Analysis of an aperture coupled microstrip antenna

A microstrip patch antenna that is coupled to a microstripline by an aperture in the intervening ground plane is analyzed. Coupled integral equations are formulated by using the Green's functions for grounded dielectric slabs so that the analysis includes all coupling effects and the radiation and surface wave effects of both substrates. A Galerkin moment method solution of the coupled integral equations agrees quite well with measured data. Design data are contained in parameter studies, many of which are verified by experimental results.     

Analysis of microstripline coupled to microstrip antenna

An analytical method based on the aperture coupling theory and S-parameter matrix has been developed for modelling a microstripline coupled to a microstrip antenna using a circular coupling aperture. The theoretical results agree fairly well with the measurements. The analysis should have many applications in active array developments.     

Two-port higher mode circular microstrip antennas

For circular microstrip antennas, single-mode design techniques work well for the dominant mode (n=1, where n is the azimuthal dependence of the fields in the antenna), but this is not the case for zero-order (n=0) and higher order (n>1) modes, where a modal expansion is necessary. The design of higher order dominant mode circular microstrip antennas is addressed, with an example and measurements for the n=3 case. Measurements for the n =3 modes show reasonable agreement with theory in the forms of the impedance loci, but the frequency dependence is in error by the order of the bandwidth of the antenna. A design example is given for a roof-mounted circular patch for vehicular communications. The example indicates that an n=3 dominant mode patch can be used as a two-port antenna for diversity applications or with a 90° phase shifter and adder as a single-port antenna for omnidirectional coverage with (essentially) circular polarization     

Flat lens antenna concept using aperture coupled microstrip patches

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 from frequency selective surfaces, and the inadequacies of simpler geometries are explained     

Wideband and high-gain one-patch microstrip antenna coupled withH-shaped aperture

The design, fabrication, and experimental implementation of the one-patch microstrip antenna coupled with an H-shaped aperture are presented. The presented antenna has a wide bandwidth, high gain, and low cross-polarisation levels with only one-patch. The measured bandwidth of this antenna is 56.2% for the voltage standing wave ratio ⩽2.0. The cross-polarisation level is below -18.2 dB at the E-plane and below -25.7 dB at the H-plane. The maximum gain at 2.05 GHz is 10.4 dBi and the 3 dB gain bandwidth with a centre frequency at 2.17 GHz is 24%     

Transmission line analysis of nonlinear slot coupled microstrip antenna

The transmission line method is used for the analysis of microstrip antennas fed by several nonlinear slots with 'H' shapes or new geometries. This analysis allows the input impedance of nonlinear slot coupled microstrip antennas to be calculated for the four different structures.<>     

Hybrid edge, gap and directly coupled triangular microstrip antenna

A new hybrid type of configuration has been investigated to obtain wider bandwidth. In the proposed configuration, two parasitic resonators are directly coupled to the nonradiating edges of a central patch through short sections of the micro-strip lines and a third parasitic resonator is gap-coupled with its radiating edge.     

Aperture coupled microstrip patch antenna fed by nonradiating dielectric waveguide

Owing to its low loss property at millimetre-wave frequencies, the nonradiating dielectric (NRD) waveguide is very attractive for use as a feed network in planar arrays. The design, fabrication and testing of a microstrip patch antenna fed by NRD guide at X-band is described. Radiation patterns are measured and presented.<>     

Characterisation of aperture coupled microstrip patch antenna withthick ground plane

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 substrates, is particularly advantageous in millimetre wave phased array applications. It is found that the effect of ground plane thickness is to reduce the level of coupling from the feed line to the patch     

A novel scheme for reception using an active microstrip antenna

An unique aspect of the injection-locked active microstrip antenna incorporating a Gunn diode, i.e., the variation of the device current within the lock band, is exploited for the demodulation of an FM microwave signal. A simple experimental arrangement has been presented to demonstrate the demodulation performance of the receiver even in a multichannel environment. Using two such separate antennas as transmitter and receiver, a two-way short-range communication system has been demonstrated that may be suited for certain commercial and military applications     

Broadband active microstrip antenna design with the simplified realfrequency technique

This paper deals with the design of broadband active microstrip antennas where the amplifier is integrated with the radiator. Theoretically sound definitions for gain and noise figure of the active antenna are introduced, and their relationships with the definitions for the composing circuit and radiator parts are explained. A sequential design procedure is presented that allows the straightforward and optimal design of transmitting and receiving antennas with multiple active stages, taking into account input and output matching, the gain-versus-frequency curve as well as the noise performance. The theoretical concepts are illustrated with two examples: one of a transmitting active antenna and one of a receiving antenna. The former one is a two-stage design that achieves nearly 25% of bandwidth with regard to gain and matching and 24 dB gain improvement as compared to the matched passive antenna. The second one is a receiving antenna (one stage) with a measured noise figure of 1.2 dB in a bandwidth of over 17% and a gain improvement of 11.9 dB over the corresponding passive antenna. Finally co- and cross-polar radiation patterns in E- and H-plane prove that the antennas also have favorable radiation characteristics in a wide bandwidth (at least 18%)     

Design of aperture coupled microstrip antenna array fed bydielectric image line

A novel design for a linear array of microstrip antennas, aperture coupled to a dielectric image line has been developed. The design is based on a simplified theory to determine the impedances of the antennas at their apertures, and in turn, the coupling to each antenna from the image line. The theory developed is verified using an eight-element linear array and the experiment results are very good     

Some studies on two-layer electromagnetically coupled microstrip antenna with dielectric cover

Experimental investigations are carried out for two configurations, namely a driven hexagonal patch and an electromagnetically coupled microstrip antenna (EMCA), with different dielectric superstrates. Superstrate loading of the antenna is found to cause a considerable shift in the resonance frequency. The driven patch with superstrate behaves as an RL network. The maximum bandwidth of 6.21% is observed for the EMCA with a bakelite superstrate when the dielectric constant of the superstrate and the substrate of the antenna are equal.     

Aperture coupled microstrip patch antenna with thick ground planein millimetre waves

The finite thickness of the ground plane is taken into account in the cavity model to analyse some aperture coupled microstrip patch antennas at millimetre-wave frequencies (60 GHz). The thickness has a strong effect on impedance matching at high frequencies owing to the ratio between the thickness and the wavelength, which increases with frequency. The calculated results are compared to those obtained by experiment for several antennas with different input impedances due to different slot lengths. Close agreement is found between the calculated and experimental results     

Aperture coupled beam steering microstrip antenna array fed bydielectric image line

Five- and eight-element patch antenna arrays linearly fed by dielectric image lines have been developed with good E-plane and H-plane patterns. The measured results and the calculated beam steering angles agree very well. Crosspolarisations are 20 dB and side lobes are 15 dB below the main lobe     

Self-adjusting microstrip antenna

A microstrip circuit operating in the G band is presented. It allows all emitting printed antenna to self-tune its resonance frequency when it is disturbed, in order to stay resonant and matched at the desired transmit frequency. The principle, design and experimental results of the circuit are presented