Slot-coupled Microstrip Antenna Research Articles

Gain Stabilization Method for Wideband Slot-Coupled Microstrip Antenna

Wideband slot-coupled microstrip antenna (SCMSA) is a distinctive electromagnetic wave radiator in recent years with wide bandwidth and low profile. In such a wide frequency range, the electrical distance, i.e., normalized to operating wavelength, between dual equivalent magnetic currents increases obviously with upward frequency. Therefore, the realized gain is usually with a large variation, which limits the wideband performance of SCMSA. In this communication, a feasible method is proposed to stabilize the realized gain of an SCMSA over its entire impedance bandwidth by utilizing a properly designed reflector-plus-sidewall structure (RPSS), which includes a reflector with an optimized height and two vertical sidewalls. Each part has its own function in realized gain compensation and enhancement, performing a flatter and higher realized gain in a wide frequency range. To validate this method, an antenna prototype is fabricated and tested. Compared with the referenced SCMSA, the measured results indicate that the proposed one adding RPSS maintains a wide impedance bandwidth of 24.8% (3.75–4.81 GHz), but reduces gain variation from 4.1 to 0.5 dB (10.5–11 dBi) with an average realized gain increment of 2.1 dB.

Dual-Polarized Slot-Coupled Microstrip Antenna Array With Stable Active Element Pattern

A dual-polarized slot-coupled microstrip antenna array with stable active element pattern is investigated. The antenna element of the array is a slot-coupled microstrip antenna with a reflector. The effect of the ground size on the radiation pattern of the antenna element is analyzed based on the electric field and current distributions. The method of adding copper pillars around the antenna element is proposed to mitigate the influence of the ground plane. A prototype of ${1} \times {3}$ microstrip antenna array is fabricated and measured. Its measured impedance bandwidth for $\mathrm{VSWR} is 520 MHz (1.69–2.21 GHz). Within the operating band, the performances of low mutual coupling, low cross polarization, and stable active element pattern are achieved.

Compact Integrated Feeding Network for Excitation of Dual-Circular Polarization in Series-Fed Antenna Lattice

A novel approach for realization of a feeding network allowing for achieving dual-circular polarization in the slot-coupled microstrip antenna lattice has been proposed. The presented feeding network is an eight-port composed of four 3\mathchar"702DdB/90 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> directional couplers, and when appropriately integrated with the four-port series-fed antenna lattice ensures a full symmetry of the antenna layout and produces simultaneously right-handed and left-handed circular polarization. The proposed low-profile, low-cost solution can be easily integrated with the antenna lattice, and it allows for reduction of the introduced dissipation losses comparing to the known solutions, i.e., external feeding networks such as Butler matrices or power combiner/divider networks connected via coaxial cables. The proposed concept has been examined by measurements of the manufactured feeding network integrated with the previously developed antenna lattice operating at 5.4 GHz.

Series-Fed Microstrip Antenna Arrays and Their Application to Omni-Directional Antennas

The analysis of a series feed approach for N-element slot-coupled microstrip antenna arrays is presented. A cylindrical arrangement of six four-element arrays using this feeding mechanism is shown to achieve optimum omni-directional beam characteristics and exhibit pattern stability over frequency in the C-band. The cylindrical arrangement is measured to have a gain of 6 dB over 750 MHz of bandwidth. A closed-form omni-directional pattern analysis is also developed.

Low-Profile Planar Tripolarization Antenna for WLAN Communications

A tripolarization and low-profile planar antenna is designed, prototyped, and tested for WLAN application. The developed three-port antenna provides three orthogonal polarization radiations. Two slot-coupled microstrip antennas and a disk-loaded monopole are integrated into one structure. The total height of the antenna is 5.8 mm. Obtained gain for the two slot-coupled directive elements at 2.42 GHz is 7 dBi, while the gain for the monopole omnidirectional element is 2.5 dBi. The bandwidths of the three elements are 2.352.52, 2.32.54, and 2.382.49 GHz, respectively. Simulation results of the radiation patterns are presented and validated by experimental measurements.

Wideband dual-polarized slot-coupled microstrip array for synthetic aperture radar application

An 8 × 1-element wideband dual-polarized slot-coupled microstrip antenna array with high isolation and low cross-polarization in X-band is presented. The array antenna offers an impedance bandwidth (VSWR≤2) of 23% and 21% for dual polarization ports, respectively. The measured isolation between two polarization ports is better than 35 dB and the measured cross-polarization level below −25 dB in the main beam over the operation frequency band of 9.35 GHz to 9.75 Ghz. This array is well suitable for X-band SAR (synthetic aperture radar) antenna application.

Optimized ADI-FDTD analysis of circularly polarized microstrip and dielectric resonator antennas

A dispersion-optimized alternating-direction implicit finite-difference time-domain (ADI-FDTD) method is presented in this letter for the accurate modeling of complex electromagnetic structures. The analysis focuses on circularly polarized slot-coupled microstrip and dielectric resonator antennas. Introducing a class of three-dimensional spatial/temporal operators, the novel algorithm yields robust curvilinear grids which efficiently treat fine details and interfaces. Hence, the serious dispersion errors of the usual schemes, as time-steps surpass the Courant limit, are greatly reduced, enabling fast broad-band simulations. Numerical validation confirms the above merits via various realistic structures.

Compact slot‐coupled microstrip antennas with circular polarization

AbstractA compact circularly‐polarized (CP) design of a microstrip patch antennas is presented. The proposed antenna is fed by the coupling of a ring slot in the ground plane of a microstrip line. The results show that the required patch size of the proposed design at a fixed CP operating frequency has a reduction of 48%, as compared to a conventional CP microstrip antenna but, at the same time, its CP bandwidth is not decreased. Details of the simulated and experimental results are presented and discussed. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 57–59, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21080

Dual-polarized slot-coupled microstrip antenna with very high isolation

A wideband dual-polarized slot-coupled stacked microstrip antenna with very high isolation and low cross-polarization is presented. To improve isolation between two polarization ports, the stacked patches are excited by an open-ended and a T-shaped micros-trip lines both via two H-shaped slots placed in a “T” configuration. The measured isolation is better than 40.5 dB over the bandwidth from 8.8 to 9.8 GHz with cross-polarization level less than −28.5 dB. The measured VSWR⩽2 bandwidths reach 20.7% and 19.1% at the vertical and horizontal polarization ports, respectively. This antenna is suitable to be used as array elements in spaceborne synthetic aperture radars (SAR) and active phased array radars.

Design of a high isolation dual-polarized slot-coupled microstrip antenna

The design of a wideband dual-polarized slot-coupled stacked microstrip antenna with high isolation is introduced. The proposed stacked-patch antenna is excited by both open-ended and T-shaped microstrip lines via two H-shaped slots placed orthogonally so as to improve the isolation between the two polarization ports. The measured isolation is better than 40.5 dB over the bandwidth from 8.8 to 9.8 GHz with cross-polarization level of less than −28.5 dB. The measured VSWR ≤ 2 bandwidths reach 20.7% and 19.1% for the two polarization ports, respectively. This antenna is suitable as an array element for spaceborne synthetic aperture radar (SAR) and active phased-radar applications. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 212–215, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21126

Dual-frequency dual-polarized slot-coupled compact microstrip antenna for communication systems

A new design of a dual-frequency dual-polarized square microstrip antenna fed along the diagonal, embedded with a square slot having three extended stubs for frequency tuning, is introduced. The proposed antenna was fabricated using a standard photolithographic method and the antenna was tested using the HP 8510C Vector Network Analyser. The antenna is capable of generating dual resonant frequencies with mutually perpendicular polarizations and broad radiation pattern characteristics. Such dual-frequency designs find wide applications in personal mobile handsets combining GSM and CDS 1800 modes, and applications in which different frequencies are used for emission and reception such as personal satellite communications and cellular network systems.

Parallel-plate mode suppression in a slot-coupled microstrip antenna with a triplate line feed

Experimental and numerical considerations on parallel-plate mode suppression have been performed on a slot-coupled microstrip antenna with a triplate line feed. In the measurements, the effect of multiple reflection of the parallel-plate mode is caused by the edge of the dielectric substrate. We have proposed a technique to solve the problems concerning multiple reflection, and obtained good agreement between measurements and calculations. Measured results demonstrate the effective performance of the configuration with a shunt-stub in the isolated geometries. We have also performed considerations numerically on mutual coupling due to the parallel-plate mode in the array configuration with two elements. Numerical results indicate drastic suppression of the mutual coupling due to the parallel-mode in comparison with the conventional configuration.

Small slot-coupled circularly-polarised microstrip antenna with modified cross-slot and bent tuning-stub

A novel design of small slot-coupled circularly-polarised circular microstrip antenna with a modified cross-slot cut in the patch and a bent tuning-stub aligned along the patch boundary is proposed and experimentally studied. Results show that, for fixed circular polarisation (CP) operation, the antenna proposed can have an antenna size reduction of /spl sim/80%, as compared to a regular-size CP design. The significant size reduction of the proposed antenna is due to the novel modified cross-slot cut in the patch, and CP operation is obtained using a bent tuning-stub incorporating a properly oriented coupling-slot in the ground plane of the microstrip feed line.

Slot-coupled microstrip antenna for broadband circular polarisation

Broadband circular polarisation (CP) operation of single-feed slot-coupled microstrip antennas is achieved using an inclined nonlinear coupling slot. This nonlinear slot, end-loaded with two V slots, significantly broadens the CP bandwidth to about 2.1 times that obtained using a simple inclined coupling slot for CP operation. Details of the antenna design are described, and experimental results of the CP performance are presented.

Slot-coupled microstrip antenna with a triplate line feed where parallel-plate mode is suppressed

In a slot-coupled microstrip antenna with a triplate line feed, the parallel-plate mode is excited by the slot, resulting in a decrease of radiation efficiency. The authors present a technique for suppressing the parallel-plate mode in this type of the antenna. Measured results confirm the effective performance of the proposed method.

Dual slot-coupled microstrip antenna for dual frequency operation

A new dual slot-coupled circular microstrip antenna for dual frequency or dual polarisation operation is proposed. By optimising the placement of the two slots, high isolation between two ports is achieved. Experimentally, an isolation of more than 35dB is obtained at L-band.

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 [see ref. 1] or new geometries ‘└┘’, ‘└┐’ and ‘└─’ types. This analysis allows the input impedance of nonlinear slot coupled microstrip antennas to be calculated for the four different structures. The theoretical results are in good agreement with experiments.

Superstrate effects on slot-coupled microstrip antennas

An analysis for studying the superstrate (cover) effects on the slot-coupled microstrip antennas is presented. The approach is based on the reciprocity theorem and uses the grounded double- and single-layer dielectric slab Green's functions in a moment method solution for the unknown slot fields and patch currents. From these fields and currents, various characteristics of the antenna can be extracted, such as the radiation efficiency, directivity, input impedance, and resonant frequency. Numerical calculations showing superstrate effects on these antenna characteristics are presented. The input matches obtained from proper adjustment of the slot and patch dimensions are discussed. >

On slot-coupled microstrip antennas and their applications to CP operation-theory and experiment

A simple theory based on the cavity model is developed to analyze microstrip antennas excited by a slot in the ground plane. By using an equivalent magnetic current source at the feed, the electric field under the patch is obtained in terms of a set of cavity modes. In particular, the loci of the slot feed location for achieving the circular polarization and the input impedance are computed and found to be in excellent agreement with the experimentally measured results. Simple but surprisingly accurate formulas for slot-fed circularly polarized microstrip antennas are derived and compared with those for probe-fed counterparts.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Modal expansion method of analysis for slot-coupled microstrip antenna

A modal field expansion technique together with the Poynting theorem are used to derive the input impedance of slot-coupled microstrip antenna. The approach leads to easier and lower computational requirements. Predicted values of input impedance are compared with previous theoretical and experimental results.