Square-ring Microstrip Antenna Research Articles

Broadband proximity-fed square-ring microstrip antennas

The fundamental and higher-order modes of a compact ring microstrip antenna are discussed. This provides insight into the functioning of this configuration. To increase its bandwidth and gain, various broadband proximity-fed configurations of a ring microstrip antenna in the 1000 MHz frequency band are proposed. A detailed explanation for the broadband behavior of all these configurations is presented. The proximity-fed square-ring antenna yielded a bandwidth of more than 250 MHz. A further increase in its bandwidth was realized by cutting a pair of rectangular slots on the edges of the ring patch. The pair of slots reduced the orthogonal TM02 mode's resonance frequency of the patch and, along with the fundamental TM10 mode, yielded a bandwidth of more than 350 MHz. Furthermore, the proximity-fed gap-coupled configurations of rectangular-slot-cut C-shaped patches, which were derived from the ring patch, are proposed. These yielded a bandwidth of more than 500 MHz (>43%). Both of these slot-cut compact configurations gave broadside radiation patterns with gains of more than 6 dBi over the bandwidth. To further increase the gain and bandwidth of the slot-cut ring antenna, a multi-resonator configuration with parasitic ring patches, gap-coupled along the two coordinate axes, is proposed. This configuration yielded a bandwidth of more than 400 MHz with a peak gain of 9 dBi. In this configuration, a further increase in the bandwidth was realized by cutting a pair of rectangular slots on the edges of the ring patches that were gap-coupled along one of the coordinate axes. This configuration gave a bandwidth of more than 500 MHz with a peak gain of 9 dBi.

Circular polarisation from dual-layer square-ring microstrip antennas

Stacked microstrip square-ring antennas are investigated for circular polarisation (CP). Enhancement of axial ratio bandwidth is obtained using stacked square rings and applying corner perturbations to both parasitic and driven rings. Both negative and positive corner perturbations are used and wide axial ratio bandwidths are demonstrated. A novel approach is presented, where a combination of positive and negative perturbations is adopted in the driven and parasitic rings, respectively, which resembles a sequential rotation and offers broad axial ratio bandwidth, along with a wide axial ratio beamwidth. The effects of finite ground plane on the CP performance of this antenna are studied, and methods are presented to overcome the problems associated with the degradation of the CP performance because of the finite ground plane. The effect of positioning the antenna asymmetrically on the ground plane is also studied, which shows that the ground plane symmetry is important for the CP antenna. The measured 3 dB axial ratio bandwidth of approximately 5.15% is achieved for dual-layer square-ring antennas. The measured right-hand CP (RHCP) gain is in excess of 7 dBic for a wide frequency range. The simulation results are in good agreement with the measured data.

A Novel Wearable Circularly Polarized Antenna in Body-Centric Wireless Communications

Wearable, textile-based antennas are dominated research topics for body-centric communications because it could be easily worn on body and integrated into clothes. Since the antenna will operate on a moving person, a circularly polarized antenna is needed in order to optimize the off-body communication link. A wearable circularly polarized textile antenna for body-centric wireless communications is designed in this paper. The proposed antenna is a square-ring microstrip antenna with truncated corners with the bandwidth of 9% when off the body. When it is near the body, we simulate the human body as three-layer model including skin, fat and muscle and put the antenna at different distances to the body. The situation of antenna bending is also simulated at different radii. Specific Absorption Rate was evaluated at last.

Design of a Compact GPS and SDARS Integrated Antenna for Automotive Applications

This letter describes a novel compact solution for integrating a Global Positioning System (GPS) and a Satellite Digital Audio Radio Service (SDARS) antenna in a very small volume to satisfy the requirements of the automotive market. The GPS antenna is a classic small commercial ceramic patch, and the SDARS antenna is designed in order to fit in the reduced space without affecting radiation and band performance of the GPS antenna. The SDARS basic geometry is a square-ring microstrip antenna operating in the frequency range 2.320-2.345 GHz with left-hand circular polarization (LHCP), and it is wrapped around the GPS patch, which receives a right-hand circular polarization (RHCP) signal at 1.575 GHz. The overall volume of the presented integrated antenna solution is only 30 x 30 x 7.6 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , rendering it attractive for the automotive market.

Investigation into Polarization of Unloaded and Loaded Microstrip Square-Ring Antennas

The polarization characteristic of unloaded and loaded square-ring microstrip antennas is investigated. Several different loading types like single-stub, dual-stub, notch, gap and shorting-pin are considered and their effects are studied. Loading enables feeding using a 50-Omega probe. The simulation and measurement results show that the loading techniques excite a loaded TM <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode that is orthogonal to the unloaded TM <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode. This indicates that by loading the ring antenna its polarization can be switched adaptively. However, the purity of the loaded and unloaded modes depends on the loading type. For some loading types like gap and shorting-pin, the excitation of the unloaded mode seems negligible, in comparison to the loadings by stub and notch. For the stub and notch loaded antennas the unloaded mode is also present, and its excitation efficiency is frequency dependent. Thus, their polarization plane, which is due to both loaded TM <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> and unloaded TM <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> modes, also becomes frequency dependant. The results of this investigation can be useful in selecting the loading methods for high-impedance microstrip ring antennas, and control of their impedance and polarization. The knowledge of the antenna polarization is essential in communications, and its dependence on the loading type can be used as an important parameter in design of adaptive antennas and sensors.

Reconfigurable microstrip antenna with pattern and polarisation diversities

A microstrip antenna with the functions of switchable pattern and polarisation is presented. The antenna is composed of a square-ring radiating patch and four shorting walls. The shorting walls are connected to each edge of the square-ring patch through one pin diode. By controlling the states of the pin diodes, the square-ring microstrip antenna can radiate two complementary patterns (conical and broadside); moreover, dual orthogonal linear polarisations are provided for the broadside radiation. These diversity functions are operated at the same frequency band. An antenna prototype has been implemented and the results obtained are given.

Probe-feed Circularly Polarized Square-ring Microstrip Antennas With Thick Substrate

The design of a circularly polarized square-ring microstrip antenna fabricated on thick foam substrate and excited by a coaxial probe is proposed. To achieve 50Ω impedance at the antenna input port, an L-typed matching network is formed by coupling the series probe inductance to a parallel capacitance introduced by adjusting the inner slot size of the square-ring patch. Simulated results are first used to indicate the designs of the key parameters for the proposed antenna. Follow by fabricating and measured several prototypes of the square-ring microstrip antennas with various foam thicknesses, their CP performances are illustrated and discussed.

Hybrid perturbation scheme for wide angle circular polarisation of stacked square-ring microstrip antennas

A unique hybrid perturbation scheme is proposed for circular polarisation of stacked square-ring microstrip antennas, where both positive and negative perturbations are used. It is shown that the method broadens the angular range of circular polarisation. Measured results confirm the simulations.

A NOVEL DUAL-BAND RECONFIGURABLE SQUARE-RING MICROSTRIP ANTENNA

A novel compact dual-band reconfigurable square-ring microstrip antenna is presented. The tuning is achieved using a single varactor diode connected to a small square patch attached to an inner corner of the square-ring. The square patch perturbs the symmetry and splits the two degenerate modes to create dual-band operation. The frequency ratio in the range of 1.04 to 1.4 can be achieved by the proper selection of the square patch size. The lower resonance frequency can be further decreased by loading the square patch at its corner by a reverse biased varactor diode. The diode has almost no effect on the upper resonance frequency. This technique is used to implement an electronically tunable dual-band antenna on FR4 material with er =4 .5 and 1.5 mm thickness. The size of the ring,the square patch,and the varactor used,are selected to yield a fixed upper resonance frequency at about 1.93 GHz. The resulting lower resonance frequency is tuned from 1.37 to 1.7 GHz in the voltage range from 0 to 30 V,respectively. The measurements agree well with simulation results.

Design of a single-feed dual-frequency microstrip antenna

This paper presents a new dual-frequency design for microstrip patch antennas. The proposed dual-frequency antenna is excited by a single probe feed, and the feed position is on the rectangular patch that is surrounded by a square-ring patch. The rectangular patch not only acts as a coupling-strip feed to the square-ring microstrip antenna at a lower frequency, but can also be resonant at a higher frequency. In addition, the two operating frequency bands can produce the same linear polarization or dual polarizations. Details of the antenna designs are described. The experimental and simulated results are also shown and discussed. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 114–116, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21096

Design of square-ring microstrip antenna for circular polarisation

The design of a square-ring microstrip antenna with circular polarisation (CP) is presented. To compact the antenna size and overcome the high impedance problem, the CP antenna is excited by a coupling strip located inside the square-ring patch. Several prototypes of the square-ring CP antennas with various substrate thickness (0.013–0.09λ0) have been constructed and studied experimentally, and their coupling-strip designs and CP performance are described.

Square-ring microstrip antenna with a cross strip for compact circular polarization operation

A novel design of square-ring microstrip antenna with a cross strip for achieving compact circular polarization (CP) operation is proposed and experimentally studied. The cross strip can be placed in the centerlines or diagonals of the square-ring patch. Either design can make its excited fundamental mode patch surface current path much longer than that in a conventional square microstrip antenna with same antenna size. By incorporating a small tuning stub for splitting the fundamental mode into two near-degenerate resonant modes with equal amplitudes and 90/spl deg/ phase-difference compact CP operation for the proposed design can he obtained.

Designs for an aperture-coupled compact circularly polarised microstrip antenna

Designs of a square-ring microstrip antenna with a cross-strip, and a square microstrip antenna with a cross-slot for circular polarisation (CP) operation, are proposed and experimentally studied. Both the cross-strip and cross-slot are of equal arm lengths, and the two proposed designs can make their respective fundamental-mode patch surface current path much longer than a simple square microstrip antenna of the same size. By adjusting the coupling cross-aperture in the ground plane of the microstrip feed line, the fundamental mode can further be split into two near-degenerate orthogonal modes with equal amplitudes and 90/spl deg/ phase difference. Results show that, for a fixed frequency, a reduction in antenna size of 24/spl sim/30% can be achieved by using the proposed designs. Details of the proposed antenna design are described, and experimental results for the CP performance are presented and discussed.

Single-feed square-ring microstrip antenna with truncated corners for compact circular polarisation operation

A novel circular polarisation (CP) design of a single-feed square ring microstrip antenna with truncated corners is described. Experimental results show that the proposed design has a reduced antenna size as compared to the conventional circularly-polarised square microstrip antenna with truncated corners at a given operating frequency. Also, the required size of the truncated corners for CP operation is larger for the present design than for the conventional design using a square microstrip patch, which suggests that the fabrication tolerance is relaxed for the present design. Typical results are presented and analysed.