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ABSTRACT This article proposes a novel, simple, microstrip-fed, circularly polarized, stacked, diagonal-slotted, wideband hexagonal microstrip patch antenna for Intelligent Transport System (ITS) applications. It has been found to operate in the Global Positioning Systems frequency L1 (GPS 1.575 GHz). The fabricated antenna shows an impedance bandwidth of 171 MHz which is around 11% (1.521-1.692 GHz) with 3 dB axial-ratio-bandwidth (ARBW) of 80 MHz which is around 5% (1.54-1.62 GHz) and for the entire 3 dB ARBW the gain achieved is over 6.5 dBi. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2548-2554, 2015 [ABSTRACT FROM AUTHOR]

Although conventional Yagi antenna has the advantage of unidirectional radiation patterns, it is not suitable for wideband applications due to its drawback of narrow bandwidth. In this communication, a compact wideband planar printed quasi-Yagi antenna is presented. The proposed quasi-Yagi antenna consists of a microstrip line to slotline transition structure, a driver dipole, and a parasitic strip element. The driver dipole is connected to the slotline through a coplanar stripline (CPS). The proposed antenna uses a stepped connection structure between the CPS and the slotline to improve the impedance matching. Two apertures are symmetrically etched in the ground plane to improve the unidirectional radiation characteristics. Simulation and experimental results show that the unidirectional radiation patterns of the proposed antenna are good. A 92.2% measured bandwidth with S 11 < -10~dB from 3.8 to 10.3 GHz is achieved. A moderate gain, which is better than 4 dBi, is also obtained. [ABSTRACT FROM PUBLISHER]

ABSTRACT A complementary staked microstrip antenna with a modified Minkowski fractal shaped defect is presented which has a wide bandwidth of 1.8-6.4 GHz with a fractional BW of 89.1%. The concept of the complimentary stacked parasitic fractal patch has been incorporated to enhance the impedance bandwidth in comparison to the conventional stacked patch antenna. The antenna has a dimension of 42 × 55 × 4.8 mm3, which is printed on a low cost FR4 substrate of dielectric constant 4 and a height of 1.6 mm. The gain of the antenna varies from 5 to 7 dBi throughout the operating band. Simulated and experimental characteristics of the antenna are in good agreement. The proposed antenna can be a potential candidate for wideband communication systems and also capable to operate satisfactorily in 3.3-3.7 GHz (WiMAX), 3.7-4.2 GHz (C-Band), and 5.15-5.825 GHz (WLAN) frequency bands. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:944-947, 2014 [ABSTRACT FROM AUTHOR]

Novel circular polarization (CP) design of planar broadband antenna with square slot for UHF RFID system is proposed and experimentally studied. By insetting the arc-shaped strip into the square slot, the proposed CP design can easily be achieved with the impedance bandwidth (RL \geqq 10 dB) of about 142 MHz (15.3% @ 931 MHz) and the 3 dB axial-ratio (AR) bandwidth of about 166 MHz (17.7 % @ 940 MHz) for UHF RFID applications. The measured peak gain and radiation efficiency are about 6.8 dBic and 98% across the operating band, respectively, with nearly bidirectional pattern in the XZ- and YZ-plane. [ABSTRACT FROM PUBLISHER]

A new microstrip monopolar patch antenna is proposed and analyzed. The antenna has a wide bandwidth and a monopole like radiation pattern. Such antenna is constructed on a circular patch antenna that is shorted concentrically with a set of conductive vias. The antenna is analyzed using a cavity model. The cavity model analysis not only distinguishes each resonating mode and gives a physical insight into each mode of the antenna, but also provides a guideline to design a broadband monopolar patch antenna that utilizes two modes (TM01 and TM02 modes). Both modes provide a monopole like radiation pattern. The proposed antenna has a simple structure with a low profile of 0.024 wavelengths, and yields a wide impedance bandwidth of 18% and a maximum gain of 6 dBi. [ABSTRACT FROM PUBLISHER]

A compact dual band-notched Ultra-Wideband antenna with sharp band-notched characteristics and controllable notched bandwidths is presented. The antenna consists of a spade-shaped microstrip-fed Ultra-Wideband planar monopole antenna and two sets of band-notched structures. The band-notched structures are employed to generate the desired lower and upper rejection bands with good frequency selectivity and sufficient rejection bandwidths. Moreover, the bandwidth of the lower and upper rejection bands can be independently adjusted by changing the size of the band-notched structures. Finally, a UWB antenna is successfully designed with the dual notched bands for the lower WLAN band (5.15- 5.35 GHz) and upper WLAN band (5.725-5.825 GHz). A good impedance match is obtained in 3.1-10.6 GHz frequency range (|S11 | < - 10dB), except the lower and upper WLAN band (|S11| > - 5dB). The ratios of the notched bandwidths between - 5dB and -10 dB in the two stop bands are greater than 0.73. [ABSTRACT FROM AUTHOR]

This paper presents the design and development of corner truncated rectangular microstrip antenna comprising U and inverted U-slot for multiband tunable operation, wide impedance bandwidth, and high gain. By incorporating U and inverted U-slots of optimum geometry on the radiating patch the proposed antenna operates between 3 to 12 GHz at different frequency bands and giving a peak gain of 1.73 dB without changing the nature of broadside radiation characteristics, compared to conventional rectangular microstrip antenna. The experimental and simulated results are in good agreement with each other. Design concepts of the antenna are given. The experimental results are presented and discussed. The proposed antennas may find applications in WiMax, HIPERLAN/2, and radar communication systems. [ABSTRACT FROM AUTHOR]

This study demonstrates the feasibility of using microstrip L-shaped stepped impedance resonators in a dual-band filter, in conjunction with one of two coupled fed structures. Traditional single-band coupled filter design theory is used and each design parameter of the filter is controlled by two suitable physical parameters. Thus, the specifications, such as the central frequencies and the bandwidth of the two bands, can be fulfilled simultaneously. The filter maintains the geometry of the resonators without the need for additional matching networks. Design curves are constructed systematically, and used to obtain an appropriate pair of physical parameters that meet the desired specifications without trial and error. The L-shaped resonator makes the required values of the physical parameters possible to be found. Two dual-band filters operated at 2.4/5.2 GHz bands are fabricated and measured to verify the design concept. [ABSTRACT FROM AUTHOR]

In this study, a novel compact microstrip antenna with an ultra wide bandwidth is presented. The proposed antenna is a U-shaped square patch combined with two parasitic tuning stubs which is fed by a coplanar waveguide (CPW). The total size of the fabricated antenna is 24×28×0.787 mm3. The dimensional parameters for the antenna are introduced and their effects on the frequency characteristic have been investigated through a parametric study. Simulated and experimental results indicate that the antenna achieved an ultra wideband impedance bandwidth (S11 < -10 dB) as high as 129%. The radiation patterns of the antenna are measured and presented. The simulated results show good agreement with the measured results. The measured gains range from 1.6 to 5.3 dBi against frequency. These characteristics make the antenna suitable for UWB applications. [ABSTRACT FROM AUTHOR]

An effective method is introduced to improve the stopband performance of microstrip parallel-coupled line bandpass filters. The proposed filter is constructed by adding several partially coupled resonators close to each trace in the conventional microstrip parallel-coupled line bandpass filter. The lengths of the coupled section and the stub section in each partially coupled resonator are selected such that the desired transmission zero is obtained. Proper selection of the number and the frequency of each transmission zero eventually makes it possible to suppress the unwanted spurious responses. In order to demonstrate the characteristics of the proposed filter, a third-order bandpass filter, which is centred at the operating frequency of 1 GHz with 10% fractional bandwidth, is designed, tuned, fabricated and tested. Measurement and simulation results show that the proposed prototype has a broad upper stopband performance, whereas it keeps the desired passband loss and shape almost equal to that of the conventional ones. [ABSTRACT FROM AUTHOR]

A microstrip printed monopole antenna with defect ground plane is proposed. It provides wideband performance with radiation pattern similar to ideal monopole antenna. It is compact and has low profile. It is demonstrated that the antenna provides an impedance bandwidth ranging from 2.37 GHz to 6.12 GHz (for VSWR < 2) and supports a monopole type pattern. Extensive simulations are employed through varying its geometric parameters and discussed in the paper. [ABSTRACT FROM AUTHOR]

Microstrip-line-fed printed wide-slot antenna with a fractal- shaped slot for bandwidth enhancement is proposed and experimentally studied. By etching the wide slot as fractal shapes, it is experimentally found that the operating bandwidth can be significantly enhanced, and the relation between the bandwidth and the iteration order (10) and iteration factor (IF) of the fractal shapes is experimentally studied. Experimental results indicate that the impedance bandwidth, defined by -10 dB reflection coefficient, of the proposed fractal slot antenna can reach an operating bandwidth of 2.4 GHz at operating frequencies around 4 GHz, which is about 3.5 times that of a conventional microstrip-line-fed printed wide-slot antenna. It also achieved a 2-dB gain bandwidth of at least 1.59 GHz. [ABSTRACT FROM AUTHOR]

Compact broadband microstrip antennas have recently received much attention due to the increasing demand for extremely small antennas covering a wide operation bandwidth for many radar and satellite communication applications. This paper reports a method to enhance the impedance bandwidth of a rectangular microstrip antenna by suitably modifying its geometry in the form of plus shape. The experimental results show that there is an improvement of 12.27% impedance bandwidth, when compared to conventional microstrip antenna. Further, after incorporating the optimum slot in the ground plane, the impedance bandwidth increases to 29.4%. This impedance bandwidth becomes 39.5% when two-element array is constructed. This enhancement is achieved at X-band frequency without much change in the radiation pattern. The wideband operation of the proposed antennas may find applications in modern communication systems. [ABSTRACT FROM AUTHOR]

In this article, one wideband circularly polarized microstrip antenna array has been proposed and investigated. The technique of sequential rotation subarray has been employed to construct the whole antenna array, which enhances the impedance bandwidth and axial ratio (AR) bandwidth by 54.65 and 220.93%, respectively, when compared with the traditional way of CP array formation. One 8 × 4 antenna array has been fabricated and measured, agreement can be observed between the experimental and simulation results, the measured VSWR bandwidth is 7.33%, the AR bandwidth is 4.31%, and the gain is about 19 dB. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1624–1627, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24438 [ABSTRACT FROM AUTHOR]

This work looks at the use of wideband cavity-backed U-slot microstrip antennas in finite phased arrays. This configuration retains the single-patch and single-layer characteristics of conventional microstrip antenna arrays and provides a good impedance matching over wider scan angles when electrically thick substrates are used to improve the frequency bandwidth. The characteristics of finite phased arrays of U-slot rectangular microstrip patches enclosed in cylindrical cavities are analyzed from a validated hybrid methodology based on the finite element method, the modal analysis, and the properties of spherical waves. The results are compared with those obtained using an infinite array model. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009. [ABSTRACT FROM AUTHOR]

An optimized coplanar-waveguide-fed quasi-magnetic printed antenna for ultra-wideband applications is described. A parameter study, motivated by a design procedure, allowed a substantial increase in the return-loss operational bandwidth. The numerically predicted performance was validated by means of physical measurements of fabricated samples. The measured radiation patterns of the antenna demonstrated its adequate radiation characteristics. The feed radiation was also investigated by means of physical measurements. [ABSTRACT FROM AUTHOR]

Coplanar waveguide (CPW)-loop fed wideband multilayered microstrip antennas with and without via combinations are presented. The antenna consists of two dielectric substrates, CPW-loop on the ground plane layer, main patch on the middle layer and four asymmetric parasitic patches on the upper layer. The feed consists of a CPW, a loop on a ground plane and a via between main patch and feeding strip on the ground plane layer. Using via, the gain flatness over the impedance bandwidth and return loss are improved. The proposed antenna with four feeding structures is also studied. The 10 dB return loss bandwidths of the antenna with and without via are 34% (3.12–4.41 GHz) and 33.7% (3.18–4.47 GHz), respectively. The measured gain is >5.0 dBi over the impedance bandwidth. [ABSTRACT FROM AUTHOR]

A printed, Linearly Tapered Slot Antenna for 11.0 GHz was theoretically designed using the Stepped Approximation Method (SAM). The designed and calculated values have been optimized for wide band performance using the Computer Simulation Technology (CST) Microwave Studio. This microstrip antenna was fabricated on polytetra fluoroethylene (PTFE) and finally tested for its RF wideband performance. Various antenna parameters such as Voltage Standing Wave Ration (VSWR), radiation pattern, energy loss and 1:2 VSWR bandwidth were measured and the same recorded in the plots. The performance of this antenna system indicated its multi-frequency operation as a wideband Traveling Wave Antenna in the end fire mode. Also, the dielectric constant performance variation with frequency was tested in RF lab to confirm the effectiveness of its wideband multi-frequency operation. [ABSTRACT FROM AUTHOR]

Abstract-A design is described of a broadband circularly-polarized (CP) slot antenna. A conventional annular-ring slot antenna is first analyzed, and it is found that two adjacent CP modes can be simultaneously excited through the proximity coupling of an L-shaped feed line. By tuning the dimensions of this L-shaped feed line, the two CP modes can be coupled together and a broad CP bandwidth is thus formed. The design method is also valid when the inner circular patch of the annular-ring slot antenna is vertically raised from the ground plane. In this case, the original band-limited ring slot antenna is converted into a wide-band structure that is composed of a circular wide slot and a parasitic patch, and consequently the CP bandwidth is further enhanced. For the patchloaded wide slot antenna, its key parameters are investigated to show how to couple the two CP modes and achieve impedance matching. The effects of the distance between the parasitic patch and wide slot on the CP bandwidth and antenna gain are also presented and discussed in details. [ABSTRACT FROM AUTHOR]

A wideband circularly polarised slot antenna is presented. The slot antenna is fed by four microstrip line feeds orientated to have relative phases of 0°, 90°, 180° and 270° using a feed network comprising a pair of broadband 90° hybrid. The proposed antenna delivers measured and simulated impedance bandwidths of 77.8% (1.02–2.32 GHz) and 89.1% (1.02–2.66 GHz), respectively, for standing wave ratio (SWR)<2, measured and simulated axial-ratio bandwidths of 88.9% (1–2.6 GHz) and 81% (1.1–2.6 GHz), respectively, for axial ratio < 3 dB and measured and simulated gain bandwidths of 33% (1.5–2.1 GHz) and 27% (1.6–2.1 GHz), respectively, for gain >3 dB. A good agreement is observed between simulation and measurement. [ABSTRACT FROM AUTHOR]

A novel method to extend the operation bandwidth and reduce the size of the ultralow-profile microstrip antenna is presented in this paper. Printed on a dielectric substrate of FR4 with relative permittivity of 4.4, loss tangent of 0.02 and thickness of h = 1 mm (≈ 0.005λ0, where λ0 is the center frequency wavelength at free space), and fed by coaxial probe from the back, the microstrip antenna loaded by slots is demonstrated to generate three closer resonant frequencies of 1.625 GHz, 1.682 GHz and 1.752 GHz to achieved wideband characteristic (1605–1776 MHz, 10.1%). The antenna size is only 23% of the traditional microstrip antenna for the same frequency with the same substrate. Details of the antenna design is presented and discussed in this paper. [ABSTRACT FROM AUTHOR]

A small-sized active integrated antenna (AlA), consisting of a transmission feedback oscillator loaded with a microstrip antenna is presented in this paper. The oscillator antenna, which consists of a NEC super low noise high frequency field effect transistor (HF FET) integrated into the center of a segmented patch antenna, was designed for X-band at 8.50 GHz, and occupies a 5 x 6 mm2 area. The active integrated antenna demonstrates stable oscillations and excellent radiation patterns at X-band design frequencies. When biased using a single 1.5 volt battery connected between the source and drain and with the gate terminal open, the antenna effective isotropic radiated power (EIRP) and direct current (DC)-to-radiated radio frequency (RF) conversion efficiency are +11.2 dBm and 10.5%, respectively. The radiated power level and directivity are +4.5 dBm and 6.7 dBi, respectively. The phase noise at 100 kHz offset from the carrier is -87.5 dBc/Hz, which is a notable improvement over existing AlA designs. The AlA features compact size and simple geometry, yet provides radiated power levels and radiation efficiencies that are comparable to values typically obtained using circuits that occupy larger areas, and use thicker substrates with much lower dielectric constant values. [ABSTRACT FROM AUTHOR]

A compact single feed dual-band electronically tunable microstrip antenna for operation in GSM/DCS-1800 system is presented. The antenna consists of two resonant elements designed separately and integrated while preserving their designed bands. The two bands are separately tuned using two biasing control circuits. A significant size reduction and bandwidth selection are achieved using a varactor diode as a voltage control capacitance. The design and implementation is carried out on a foam substrate of thickness 2.44 mm and with a dielectric constant 1.2. Simulation and experimental results show that the required bandwidth of the GSM/DCS-1800 system can be easily covered with voltage changes from 1 to 3 V, which is suitable for mobile hand phones. [ABSTRACT FROM AUTHOR]

A wideband circularly polarized reconfigurable microstrip patch antenna fed by L-shaped probes is presented. Right hand circular polarization and left hand circular polarization could be excited by L-shaped probes feeding a perturbed square patch. The L-shaped probes are connected to a switch which is fabricated underneath the ground plane, such that circularly polarized radiation pattern reconfiguration could be realized. An antenna prototype was fabricated and it attains a bandwidth of over 10% with both SWR < 2 and axial ratio < 3dB. [ABSTRACT FROM AUTHOR]

A new technique is developed to increase the axial ratio (AR) bandwidth of circularly polarized stacked microstrip antennas (CPSMAs) to about 15.0% by optimizing the location of the C-type single feed and a few other parameters. The stacked microstrip antenna with a quasi-planar surface-mounted short horn (SMSH) has achieved 13 dBi gain, 15.5% 3dB AR bandwidth, 0.37 dB minimum AR and 25.0% impedance bandwidth. The measured gain is more than 11.5 dBic over the impedance bandwidth. The proposed technique simplifies the design of wideband circularly polarized antenna for medium to high gain applications. [ABSTRACT FROM AUTHOR]

An original leaky-wave antenna (LWA), conceived from a microstrip line which is laterally shielded by parallel plates, is presented in this paper. This structure shows, for the first time, that the leakage rate of a microstrip leaky-mode can be easily controlled while negligibly affecting the pointing direction. The antenna is based on the radiation from the second higher order mode of the microstrip line, which is perturbed by the addition of the two conductor walls to control the level of the leakage rate. The parallel-plates also serve as a mechanism to obtain a single main beam in the azimuthal plane, therefore improving the radiation pattern compared to common dual-beam second-higher order mode microstrip LWAs. The proposed antenna is analyzed by obtaining the corresponding leaky-mode complex propagation constant, which is calculated by a specific method of moments approach. The modal results obtained from the leaky-mode dispersion curves are validated with analysis performed on a three-dimensional structure using commercial finite element method solver. Also, a prototype is fabricated to experimentally confirm the advantages of this novel leaky-wave line source. [ABSTRACT FROM AUTHOR]

A novel 900 broadband balun comprising a broad- band 90° Schiffman phase shifter is introduced as a means of enhancing the wideband circular polarization performance of dual-fed type microstrip antennas. The proposed 90° broadband balun delivers good impedance matching, balanced power splitting and consistent 90° (±50) phase shifting, across a wide band- width ( -`57.5%). A circular patch antenna utilizing the proposed 90° broadband balun is shown to attain measured impedance (S11 < -10 dB) and axial ratio (AR < 3 dB) bandwidths of 60.24% and 37.7%, respectively, for the dual L.probe case; and 71.28% and 81.6% respectively, for the quadruple L-probe case. [ABSTRACT FROM AUTHOR]

A novel microstrip slot antenna for UWB (Ultra Wideband) antenna applications is proposed. A slot antenna is filled by an isosceles triangle. This structure is fed by a single microstrip line with a fork-like tuning stub. Experiments are carried out to investigate its return loss, its radiation and its time domain behavior, which exhibit good radiation pattern and impedance bandwidth over the entire band of frequency. Time domain consideration also exhibits that this antenna can be used with short pulses. [ABSTRACT FROM AUTHOR]

Based on the conventional microstrip antenna, a broadband circularly polarized microstrip antenna fed by electromagnetism coupling is designed, which is composed of three substrates. The frequency band is broadened not only, but also the circular polarization axial ratio is effectively improved. Then four such cells are constructed to a circularly polarized array. Through calculating and testing, the 14.4% and 39.65% (VSWR < 2) bandwidth and 8.34% and 21.4% 3-dB axial ratio bandwidth are achieved, respectively. Such circularly polarized array can be used extensively in communications field. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2936–2939, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22916 [ABSTRACT FROM AUTHOR]

A theoretical design of single coaxial-feed wideband circular polarized rectangular stacked microstrip antennas (CPSMAs) with dielectric cover is present by using optimization of feed location and other parameters. The location of the single coaxial feed, foam thickness between driven and parasitic patches and aspect-ratio of parasitic patch is optimized for wideband and quality of circular polarization (CP). Prototype antenna designed, fabricated, and measured its performance. The antenna has measured 3-dB AR bandwidth of 13.5%, minimum AR of 0.5 dB, a 10-dB return loss bandwidth of 21.5%. The gain of antenna is more than 7.5 dBic over the 3-dB AR bandwidth and peak gain about 9 dBic at 5.6 GHz. The total antenna height is 8.583 mm or 0.157 λ0 at 5.5 GHz, where λ0 is the free space wavelength. The proposed techniques simplify the design of wideband circularly polarized antennas with cover for medium to high gain applications. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 3027–3033, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22937 [ABSTRACT FROM AUTHOR]

The microstrip planar monopole-like antenna, MPM, capable of multiband operation is proposed. The MPM antenna constructed as microstrip 50-Ω line loaded by the two planar resonant strips. The strips and the microstripline are photo-etched on microwave laminate Rogers TMM4. The inner loaded strips resonating as a quarter-wavelength structure and the outer folded strip resonating as both a quarter-wavelength and a half-wavelength structure. The flat (∼0.002 λ) MPM antenna, 12 mm (<0.1 λ) in height and 30 mm in width has been constructed, and the obtained bandwidths cover the four bands of three digital communication systems, centered: at 900 MHz and at 1800 MHz for the GSM, at 1900 MHz for PCS, and at 2050 MHz for UMTS, respectively. Results of design, simulations, and experiments are presented. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2766–2769, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22867 [ABSTRACT FROM AUTHOR]

Simple design guidelines for an ultra wideband aperture-coupled vertical microstrip–microstrip transition are presented. The proposed transition uses broadside coupling between elliptical-shaped microstrip patches at the top and bottom layers via an elliptical-shaped slot in the mid-layer. Theoretical analysis indicates that the best performance concerning the insertion loss and the return loss over the maximum possible bandwidth can be achieved when the between the top and bottom coupled patches is equal to 0.8 (or 1.94 dB). Simulated and measured results show that the proposed transition has an insertion loss of <0.7 dB and a return loss of >15 dB across the frequency band 3.1–10.6 GHz. [ABSTRACT FROM AUTHOR]

A new feed system is presented for improving the quality and bandwidth of circularly polarised stacked microstrip antennas (CPSMAs). The feed system consists of a microstrip line and a via (or pin) from the microstrip line to a driven patch. A systematic design process to achieve near-optimal CP performance from these antennas is presented. An example design demonstrated a measured 3 dB axial-ratio (AR) bandwidth of 17% and a measured 10 dB return bandwidth of 35%. The measured gain is more than 8 dBic over the 3 dB AR bandwidth. The total height of the antenna is 8.536 mm or 0.156λo at 5.5 GHz. The new feed system is found to be very useful for the design of wideband, compact, low-cost, CP microstrip antennas and arrays. [ABSTRACT FROM AUTHOR]

A VHF microstrip patch antenna was developed to achieve a bandwidth of 45 MHz (30%) from 127 to 172 MHz with dual-linear-polarization capability. This microstrip antenna, having a size of 117 cm x 117 cm x 27 cm, used low-di-electric-constant foam substrates and dual-stacked patches with capacitive probe feeds to achieve the required wide bandwidth. Four such capacitive feeds were used to achieve dual polarizations with less than -20 dB of cross-polarization level. Twenty-four shorting pins were uniquely used here on the lower patch to achieve 40 dB of isolation between the two polarization ports. This antenna has a measured gain of 8.5 dB at 137 MHz and 10.3 dB at 162 MHz. One advantage observed here at the low frequencies of VHF is that more electrical structures can be easily integrated into the microstrip antenna to improve its performance. [ABSTRACT FROM AUTHOR]

Design and experiment is given of differentially-driven microstrip antennas. First, the design formulas to determine the patch dimensions and the location of the feed point for single-ended microstrip antennas are examined to design differentially-driven microstrip antennas. It is found that the patch length can still be designed using the formulas for the required resonant frequency but the patch width calculated by the formula usually needs to be widen to ensure the excitation of the fundamental mode using the probe feeds. The condition that links the patch width, the locations of the probe feeds, and the excitation of the fundamental mode is given. Second, the wideband techniques for single-ended microstrip antennas are evaluated for differentially-driven microstrip antennas. A novel H-slot is proposed for differentially-driven microstrip antennas to improve impedance bandwidth. Third, the effects of imperfect differential signal conditions on the performance of differentially-driven microstrip antennas are investigated for the first time. It is found that they only degrade the polarization purity in the H-plane with an increased radiation of cross-polarization. Finally, both differentially-driven and single-ended microstrip antennas were fabricated and measured. It is shown that the simulated and measured results are in acceptable agreement. More importantly, it is also shown that the differentially-driven microstrip antenna has wider impedance bandwidth of measured 4.1% and simulated 3.9% and higher gain of measured 4.2 dBi and simulated 3.7 dBi as compared with those of measured 1.9% and simulated 1.3% and gain of measured 1.2 dBi and simulated 1.2 dBi of the single-ended microstrip antenna. [ABSTRACT FROM AUTHOR]

Circularly polarized single-layer U-slot microstrip patch antenna has been proposed. The suggested asymmetrical U-slot can generate the two orthogonal modes for circular polarization without chamfering any corner of the probe-fed square patch microstrip antenna. A parametric study has been carried out to investigate the effects caused by different arm lengths of the U-slot. The thickness of the foam substrate is about 8.5% of the wavelength at the operating frequency. The 3 dB axial ratio bandwidth of the antenna is 4%. Both experimental and theoretical results of the antenna have been presented and discussed. [ABSTRACT FROM AUTHOR]

A new design of a U-slot microstrip antenna with an E shaped stacked patch is presented that achieves an impedance bandwidth of 59.7%. Parameters such as substrate thickness, slot length, width are investigated and design results from parametric simulations are presented. The electric current distributions on the patch and the radiation patterns are also demonstrated in this paper. [ABSTRACT FROM AUTHOR]

In this paper, microstrip-line-fed rectangular microstrip antenna with open-end meandering slots in the ground plane for compact broadband operation is presented. The proposed design consists of a rectangular patch which is fed by a 50-Ω center fed microstrip-line feed. Three identical narrow open-end meandering slots were embedded in the antenna's ground plane parallel to the rectangular patch's radiating edge. Experimental study is carried out by varying the length of the open-end meandering slots. Using open-end meandering slots in the ground plane, the resonant frequency of the antenna is greatly lowered with large enhancement in bandwidth when compared with conventional microstrip antenna. With the proposed design, an extreme reduction of 82.9% in the antenna size is obtained with a wide bandwidth of 40%. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 824–827, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22267 [ABSTRACT FROM AUTHOR]

Two wideband tapered slot antennas are designed, fabricated, and tested. The first antenna, which is fabricated on a high dielectric constant substrate (εr = 10.2), shows a measured return loss of better than 10 dB from 1.6 to 12.4 GHz (7.7:1 bandwidth), and an antenna gain varying from 3.6 to 7.8 dBi. The second antenna is built on a low dielectric constant substrate (εr = 2.2), and demonstrates return loss of better than 10 dB from 1.8 to 15.2 GHz (8.4:1 bandwidth). The second antenna also has improved antenna gain, from 5 to 15.6 dBi, and is used to build a wideband 1 × 4 H-plane phased array with a total gain of 9–17 dBi and a beam steering angle of ±15° from 3 to 12 GHz. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007. [ABSTRACT FROM AUTHOR]

A broadband microstrip-to-coplanar strip (CPS) and a microstrip-to-coplanar waveguide (CPW) transition, both employing composite right/left-handed (CRLH) transmission line (TL) technology are presented. These metamaterial lines are known to possess unique ‘backward wave’ characteristics. The transition design concept is based on taking advantage of controlling the phase slope and offset of the CRLH-TL. The pairing of a microstrip delay line and the CRLH-TL has a broadband out-of-phase characteristic, thus enabling the broadband transition between microstrip and CPS. A 3 dB insertion loss bandwidth of 85% was achieved for a back-to-back microstrip-to-CPS transition. A broadband microstrip-to-CPW transition is implemented by adding one microstrip delay line at both sides parallel to a CRLH-TL. A 3 dB insertion loss bandwidth of 95% was obtained experimentally. To demonstrate the applicability of the proposed microstrip-to-CPS transition, a modified quasi-Yagi antenna is built and tested. An impedance bandwidth of 65% was obtained, showing a 15% bandwidth enhancement over the original antenna. [ABSTRACT FROM AUTHOR]

Various suspended broadband and compact circular microstrip antennas using variations of U-slot, V-slot, and a pair of rectangular slots cut either on the periphery or inside the patch are proposed. These antennas have larger bandwidth with a broadside radiation pattern. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 435–439, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21373 [ABSTRACT FROM AUTHOR]

A wide-band probe fed patch antenna with low cross polarization and symmetrical broadside radiation pattern is proposed and studied. By employing a novel meandering probe feed and locating a patch about 0.1⅄0 above a ground plane, a patch antenna with 30% impedance bandwidth (SWR < 2) and 9 dBi gain is designed. The far field radiation pattern of the antenna is stable across the operating bandwidth. Parametric studies and design guidelines of the proposed feeding structure are provided. [ABSTRACT FROM AUTHOR]

A method based on the volume-surface-wire integral equation and precorrected-fast Fourier transform (FFT) method is presented for accurate analysis of probe-fed microstrip antennas on arbitrarily-shaped, finite-sized ground plane and substrate. The method of moments (MoM) is used to solve the integral equation. Three triangular-type basis functions are used to represent the unknown currents in the substrates, on the conducting surfaces, and probes respectively. The connection of a vertical probe feed to the patch is rigorously modeled by an attachment mode at the junction. The precorrected-FFT method is applied to reduce the memory requirement and computational cost of the traditional MoM to facilitate analysis of large antenna arrays. [ABSTRACT FROM AUTHOR]

Magnetic properties were imparted to a naturally nonmagnetic material by metallic inclusions. A patch antenna tested the performance of the magnetic metamaterial as a substrate and validated that a single substrate can achieve a range of miniaturization values. The effective medium metamaterial substrate employed electromagnetically small embedded circuits (ECs) to achieve permeability and permittivity greater than that of the host dielectric. Geometric control of the ECs allowed μ and ε to be tailored to the application. The magnetic metamaterial exhibited enhanced μ and ε with acceptable loss-factor levels. Models for predicting μ and ε are presented, the benefits of employing metamaterial substrates are discussed, and the results in this antenna experiment are presented. The meta material exhibits performance characteristics not achievable from natural materials. Of particular significance is that with the permeability varying strongly and predictably with frequency, the miniaturization factor may be selected by tuning the operating frequency. Simulations indicate that such performance can be extended to several gigahertz with current technology. Relative permeability values in the μr = 1-5 range are achievable for moderately low-loss applications. Representative antenna miniaturization factors on the order of 4-7 over a moderate (approximately 10%) transmission bandwidth and efficiencies in a moderate range (20%-35%) are demonstrated with the possibility of higher efficiencies indicated. [ABSTRACT FROM AUTHOR]

The U-slot patch antenna, a single-layer single-patch antenna on a relatively thick substrate (∼0.08λ0), is a wide-band antenna with an impedance bandwidth in a range of 20%-30%, which is about an order of magnitude larger than that of the reg- War patch antenna. Recently, it was shown that a half U-slot patch antenna, with half of one of the dimensions of the U-slot patch, maintains similar wide-band behavior. The half-structure was also successfully applied to the U-slot with shorting wall. In this paper, new results on half structures, not previously published, are presented. First, the shorting pin technique is used to reduce the size of the half U-slot patch antenna. By both simulation and experimental studies, it is concluded that the impedance bandwidths, radiation patterns, radiation efficiencies and gains of the haifa structures are comparable to the corresponding full structures. Bandwidth of 28.6% and radiation efficiencies exceeding 90% are obtained for the half U-slot patch with shorting pin. Radiation patterns are stable across the matching band. Second, it is shown that a structure obtained from baking the E-shaped patch, which is a derivative of the U-slot patch, also maintains its wide-band behavior. [ABSTRACT FROM AUTHOR]

Based on the use of space-filling curves, broad-band and circularly polarized microstrip-fed slot antennas are proposed. Broad-band performance is achieved through merging different downscaled versions of a composition of "island-like" space-filling slot antennas without increasing the overall antenna size. This technique provides different resonant slot lengths corresponding to a wide range of frequencies. By merging three downscaled versions of a composite second-iteration Moore slot antenna, a broad-band slot antenna is developed. The proposed antenna has a bandwidth (VSWR < 2) of 87.6% around 4.5 6Hz, which is higher by a factor of 13.5 compared to the square ring slot antenna, and by a factor of 3 compared to the nested square rings slot antenna. The developed slot antenna has a maximum gain of 5 dB and a total area of 3 × 3 cm². Furthermore, by introducing asymmetry in the proposed slot antenna, which is implemented by replacing all parallel slots on one side of the structure and all inner slots by a ground plane, circular polarization is achieved. The circularly polarized slot antenna version has a 3-dB axial ratio bandwidth of 22% with VSWR < 2. The design and simulation of the proposed slot antennas have been performed using a moment-method-based full-wave electromagnetic simulator. Measurements of fabricated antennas are in good agreement with simulation results. [ABSTRACT FROM AUTHOR]

This paper shows the performance of a reflect array using the QUAD-EMC patch as the radiating element. The phase adjustment is made at a sub-array level by tuning the length of each driven patch. Therefore, this new design uses fewer of the required phase shifter elements. The phase diagram provides the shared phase to each QUAD-EMC unit. The return loss plot of a radiating unit excited by the microstrip line is studied. The connection between the phase diagram and the return loss plot is also discussed. Experiments have shown that we can get comparable results with those obtained by controlling the phase on each individual element. Bandwidth of 23% with 1.5 dB gain variation can be achieved when built on an FR4 substrate. The cross polarization level may be improved since there is enough room to place the straight delay lines. [ABSTRACT FROM AUTHOR]