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In this article, a three‐port circularly polarized (CP) multiple‐input multiple‐output (MIMO) antenna for wireless local area network (WLAN) application with pattern and polarization diversity is proposed. The proposed MIMO antenna system comprises of a broadside CP antenna element with a T‐shaped slot and two endfire CP antenna elements. Good impedance bandwidth of 16.9% and 5.5% are achieved by the broadside CP antenna and endfire CP antenna, respectively, and their corresponding axial ratio (AR) bandwidth is 7% and 10.47%. The isolation between the different antenna elements is better than 20 dB, and the polarization purity for all CP antenna is more than 25 dB along with the maximum radiation. [ABSTRACT FROM AUTHOR]

ABSTRACT A microstrip-fed circular slot antenna design is proposed. To excite good CP (circularly polarized) radiation, the technique of loading a cross patch (with unequal arm lengths) into the circular slot is initially applied. Here, good impedance matching can be further attained by dividing the cross patch into two equal sections with a gap loaded in between them, in which this gap will induce a capacitive loading effects on the proposed antenna. The measured results shown that the proposed antenna has 10 dB impedance bandwidth of 36.4% (2116-3124 MHz), and its corresponding CP bandwidth (along 3 dB axial ratio, AR) was 12.3% (2345-2655 MHz). In addition to that, the proposed CP slot antenna has also yielded peak gains of more than 3.3 dBic across the CP bandwidth. Detailed process of designing the proposed CP slot antenna is explicitly shown, and vital parametric studies were also conducted by simulation. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:715-720, 2016 [ABSTRACT FROM AUTHOR]

ABSTRACT The design of a small size 50 × 50 mm2 coplanar waveguide-fed square ring slot antenna is studied. To attain circular polarization (CP) radiation with broad 3-dB axial ratio (AR) bandwidth that can cover the worldwide interoperability for microwave access 2.3 GHz (2305-2320 MHz, 2345-2360 MHz) and wireless local area network 2.4 GHz (2400-2480 MHz) bands, a novel technique of extending a C-shaped branch from the vertical monopole is proposed. Good impedance matching and CP performance was achieved by further extending a vertical tuning strip from the C-shaped branch. From the measured results, 10-dB impedance bandwidth and 3-dB AR bandwidth of 63.89% and 7.93% were achieved. Furthermore, stable gain variation of approximately 2.7 dBic and radiation efficiency of more than 85% were also exhibited across the bands of interest. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:886-891, 2015 [ABSTRACT FROM AUTHOR]

ABSTRACT A small size (20 × 38.5 × 0.8 mm3) coplanar waveguide (CPW)-fed monopole antenna for wireless local area network and worldwide interoperability for microwave access applications is proposed. To achieve tripleband operation, the proposed monopole antenna is designed with a modified symmetrical U-shaped printed structure attached with a parasitic element behind it. Good impedance matching is also attained by loading two dissimilar notches separately into the two CPW ground planes. The measured 10-dB impedance bandwidths of the three operating bands (fL, fM, and fH) are 16.96% (2.105-2.495 GHz), 28.72% (3.22-4.30 GHz), and 23.32% (4.895-6.125 GHz), respectively, and all bands of interest have yielded peak gain and radiation efficiency of more than 2.7 dBi and 65%. Detail process of designing the proposed antenna is explicitly shown, and vital parametric studies were also conducted by simulation. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:342-348, 2015 [ABSTRACT FROM AUTHOR]

ABSTRACT A simple circularly polarized (CP) square loop antenna for UHF band RFID tag is proposed to overcome the polarization mismatch problem between reader antenna and tag antenna. To achieve good CP radiation, an open gap is introduced onto the square loop. Also, the technique of loading a matching stub across the RFID chip is applied to the proposed loop tag antenna, and good impedance matching between the antenna and RFID chip can be achieved by tuning the matching stub. The proposed loop tag antenna shows desirable antenna gain and good reading distance performance, and its measured reading distance reaches to 17.6 m. Therefore, the proposed antenna is an excellent candidate for various RFID applications in the UHF band, especially those that may require long reading distance. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2335-2341, 2014 [ABSTRACT FROM AUTHOR]

ABSTRACT A microstrip-fed slot antenna design for wireless local area network 2.4/5 GHz applications is proposed. To achieve dual-band operation that composed of four resonant modes located at approximately 2.28, 2.69, 5.36, and 5.94 GHz band, three separate slots are embedded into the ground plane, in which two of the slots are devised as step-impedance types, and one of the slots is an L-shaped slot type. By meticulously arranging the positions of these three slots located above the microstrip-fed line, two broad operating bands that operate between 2140-2750 MHz (∼25%) and 5050-6160 MHz (∼20%) are achieved. Detail process of designing the proposed antenna is explicitly shown, and vital parametric studies were also conducted by simulation. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:983-988, 2014 [ABSTRACT FROM AUTHOR]

ABSTRACT A coupled-fed antenna that combines the long term evolution operation with the wireless wide area network operation is proposed. The antenna is mainly composed of a T-shaped radiator linked to the ground plane via a narrow meandered line. Good impedance matching throughout all bands of interest is achieved by embedding a C-shaped coupling structure into the narrow meandered line, followed by protruding a small stub at the right bottom corner (vertical structure) of the T-shaped radiator. Furthermore, by reconstructing the coupled-fed structure as a halved-tapered fed design, two wide operating bands that operate between 680 and 1380 MHz (68%), and 1550 and 2830 MHz (58.4%) are achieved. The process of designing the proposed antenna is explicitly shown, and parametric studies were carried out by simulation. Typical experimental measurements were also conducted and compared to the simulated results. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1851-1856, 2013 [ABSTRACT FROM AUTHOR]

An electroconductive polyester yarn is used to fabricate an embroidered wearable monopole antenna for ultrawideband applications.Here, the structure of this embroidered antenna is a common coplanar waveguide-fed circular disk monopole antenna. From the experimental results, a 10-dB impedance bandwidth from 2.7 to 10.62 GHz is measured, while steady gains with near omnidirectional radiation patterns are exhibited within the bands of interest. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2597-2600, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27133 [ABSTRACT FROM AUTHOR]

The design of a hybrid antenna with double layer structures that allow multiband operation in the global system for mobile communications/digital communication systems/personal communication system/universal mobile telecommunications system and wireless local area network band bands is presented. By combining the resonant modes excited separately by the upper layer planar inverted-F antenna structure (0.88, 0.97, and 1.18 GHz) and lower layer monopole antenna type structure (1.38, 1.76, and 2.45 GHz), a dual-frequency operation with broadband characteristics can be observed, whereby the lower and upper frequency bands are operating between 0.86 and 1.00 GHz and between 1.15 and 2.63 GHz, respectively. From the experimental results, stable gain and good radiation efficiency are also exhibited within the bands of interest. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1543-1548, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26863 [ABSTRACT FROM AUTHOR]

A compact size slot antenna designed for ultrawideband (UWB) applications is proposed.The slot embedded into the antenna was comprised an open-ended hemicircular slot and a narrow rectangular slot. To achieve good impedance matching within the desired band of interest, the 50 Ω microstrip feed-line is loaded with an elliptical slot, while an extended substrate was protruded above the upper edge of the antenna. The experimental results such as return losses, radiation patterns, and gain properties are studied, and good characteristics are demonstrated. Typical frequency domain responses are also measured to ensure that the proposed antenna can provide stable signal transmission within the UWB spectrum. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:86-91, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26514 [ABSTRACT FROM AUTHOR]

A compact size (15 × 40 mm2) microstrip-fed printed planar inverted-F antenna (PIFA) for mobile applications operating in the GSM/DCS/PCS/UMTS/WLAN and WiMAX bands is proposed. The main structure of this antenna is simply a double-folded PIFA with two wide open-ended radiating sections. By tuning the dimensions of the shorter open-ended section, optimum impedance matching can be achieved, while additional slits loaded to the longer open-end section are for the inclusion of universal mobile telecommunications system band. To allow shifting of the higher frequencies modes so that a wide impedance bandwidth from 5 to 6 GHz can be achieved, the technique of adjusting the position of the shorting post horizontally along the ground plane is also introduced. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:2952-2960, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26429 [ABSTRACT FROM AUTHOR]

A novel microstrip-fed polygon slot antenna with dual-band operation for WLAN (Wireless Local Area Network) applications in the 2.4/5.2/5.8 GHz bands is proposed. The polygon slot is formed by embedding two right-angle triangular ground patches into both upper-corners of the rectangular slot. To allow the excitation of three resonant modes located exactly around 2.4, 5.2, and 5.8 GHz bands, besides tuning the length of the hypotenuse of the triangular ground patches, an L-shaped slit is also loaded into the rectangular radiating element. The design of this proposed antenna via simulation is illustrated in detail, and typical experiments were performed on the fabricated prototype. From the experimental results, the lower band measured along VSWR 2:1 operates from 2.36 to 2.63 GHz, while a broad upper band from 4.98 to 6.8 GHz is also observed. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1394-1398, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26018 [ABSTRACT FROM AUTHOR]

A printed compact size folded inverted-F antenna with simple configuration for mobile handset operating within the global system for mobile communication/personal communication system/digital communication system bands is initially proposed.To additionally cover the wireless local-area network frequency spectrum at 2.4 GHz, a narrow stub is protruded from the printed shorting wall. The excitation of these operating bands with desirable bandwidth is achieved by feeding a 50-Ω microstrip line to the folded radiating element through a via hole. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1045-1050, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25919 [ABSTRACT FROM AUTHOR]

A novel coplanar rectangular slot antenna with dual band operation is proposed.By loading two dissimilar inverted L-shaped slit into the rectangular radiating element, broad impedance bandwidth at both lower and upper operating bands are achieved to allow the operation for 2.4/5.2/5.8 GHz wireless local area network and 2.6/3.5/5.5 GHz worldwide interoperability for microwave access bands. The design evolution of this proposed antenna by simulation is clearly demonstrated, and a prototype was fabricated and experimentally investigated. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:987-991, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25936 [ABSTRACT FROM AUTHOR]

A compact size planar microstrip-fed monopole antenna designed for mobile handset applications is proposed. To operate at global system for mobile communication (GSM)/global positioning system/digital communication system/personal communication system/universal mobile telecommunications system and 2.4-GHz wireless local-area network bands, a hybrid technique of joining the horizontal section of a T-monopole to an open-loop back coupling strip and loading a pair of monopole slot into the ground plane is used. Two operating bands are observed (along 3:1 VSWR) with the lower band covering only the GSM application, while the wide upper operating band covers the remaining applications. The effects on the antenna performances by tuning the various vital parameters have also been studied. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:910-915, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25889 [ABSTRACT FROM AUTHOR]

A novel coplanar equilateral triangular-ring slot antenna with dual frequency operation is proposed for WLAN (Wireless Local Area Network) system in the 2.4/5.2/5.8 GHz operating bands.Impedance matching for both lower and upper operating bands at 2.4 and 5.8 GHz, respectively, are achieved by capacitively loading the inner triangular patch. To excite the 5.2-GHz band, two T-shaped slits are inserted into the triangular patch. The design flow of this antenna is clearly illustrated, and a prototype was constructed and experimentally investigated. Good radiation patterns and stable gain variation are measured for all operating bands. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2775-2780, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25601 [ABSTRACT FROM AUTHOR]

The numerical design method for a microstrip-fed circular-disc monopole (CDM) antenna operating within the ultrawideband (UWB) from 3.1 to 10.6 GHz is initially studied. By simply embedding a pair of U-shaped slots into the ground plane, a band-rejection (band-notch) function at around 5 GHz is achieved. For impedance matching and fine tuning of this proposed antenna, a small rectangular slit is inserted at the top centre of the ground plane. Except within the rejection band, the gain and time-domain characteristics of this antenna has successfully demonstrated that it is applicable to any high data rate short-range wireless communication system that requires a stable signal transmission in the UWB application. The performances of a common UWB CDM antenna without band-rejection function and a similar one with a slot loaded in the radiating circular patch are also investigated and compared with the proposed antenna. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1607–1613, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24379 [ABSTRACT FROM AUTHOR]

The design of a dual and triple-band planar inverted-F antenna (PIFA) is proposed for WLAN 802.11 a/b/g applications. Dual-band operation is achieved by simply truncating one of the top rectangular radiating plate's corners, and wide bandwidth for the upper-band is obtained by applying an additional small rectangular slit. By further extending the slit length, a triple-band operation can also be achieved with a maximum gain of around 5 dBi. Simulated results are provided to validate the measured results. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2159–2162, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22682 [ABSTRACT FROM AUTHOR]

The compact designs of a shorted triangular patch antenna embedded with a V slot are proposed and studied. A broadband V-slotted triangular patch antenna with one shorting wall is initially constructed as a reference. By inserting an additional shorting wall to this reference antenna, a new broadband operation can be obtained and its operating frequency is decreased by 22%, which corresponds to a reduction of 40% in the antenna area. The antenna area can be further reduced by symmetrically halving the patch size, and it is found that the impedance bandwidth of the broadband operation demonstrated no obvious variation and the operating frequency is only increased by around 8%. Details of the antenna designs and obtained results are presented. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 34–37, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22061 [ABSTRACT FROM AUTHOR]

The characteristics of circular-polarization (CP) square-ring microstrip antennas loaded with superstrate are studied in this paper. Firstly, several CP antenna prototypes with various substrate thicknesses and inner-slot sizes are designed, and they are excited by a coupling-strip feed in order to overcome the high-impedance problem of the square-ring microstrip antenna. Then, superstrates with different thicknesses and permittivities are attached to the antenna prototypes in order to evaluate their effects on the CP performances. The experimental results show that the effects are more obvious for the square-ring microstrip antenna with a larger inner-slot size. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 567–570, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21231 [ABSTRACT FROM AUTHOR]

The design of a square-shaped patch antenna loaded with an Olympic-like logo slot for 900 MHz UHF RFID reader applications is studied.To achieve good circularly polarized (CP) radiation, an additional narrow perturbation slot is also loaded centrally across the logo. By further applying the L-shaped probe-fed method, desirable 3-dB Axial Ratio (AR) and 10-dB impedance bandwidth of 3.72% and 30%, respectively, can be achieved. From the experimental results, gain level and efficiency of more than 6 dBic and 89% were also measured, respectively. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1358-1360, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27591 [ABSTRACT FROM AUTHOR]

The design of a compact coplanar waveguide-fed monopole antenna partially surrounded and coupled by a folded ground strip is presented. By properly tuning the gap between the monopole antenna and the ground strip, it is able to operate in the 5-GHz band for wireless application. From the experimental results, a resonant mode excited at around 5.5 GHz is observed with 10-dB bandwidth measured from 4.88 to 6.3 GHz. Good radiation patterns with near omnidirectional pattern in the azimuth plane are also observed. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26330 [ABSTRACT FROM AUTHOR]

Originally published Microwave Opt Technol Lett 49: 2159–2162, 2007. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 3192, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22885 [ABSTRACT FROM AUTHOR]