Search

In this letter, a design for broadband circularly slotted patch antenna fabricated on a single- layered printed circuit board (PCB) with unidirectional radiation is described. It is fed by a simple center-fed feeding scheme. Unlike conventional slotted patch antennas, the proposed antenna is loaded with four short pins such that both matching and axial-ratio (AR) bandwidths are improved. In addition to realize the CP radiation at higher frequencies, a cross-slot with different arm lengths, which is cut from the center-fed patch is used. Then, the proposed antenna operates as magnetic dipoles to generate circular polarization at low frequencies after four short pins are added to connect the patch to the ground. Thus, by combining the two modes, bandwidths of 30.2% (1.83-2.48 GHz) for |S11| < �10 dB and 21.2% (1.98-2.45 GHz) for axial ratio (AR) < 3 dB around the center frequency of 2.15 GHz are measured. Moreover, stable gain of over 8 dBic and good radiation patterns are also observed across the operating band.

A tri-band multiple-input-multiple-output (MIMO) antenna that covers all frequency bands required for WLAN and WiMAX applications is presented. Three resonant bands are achieved by a folded monopole with a compact size of 11.5 × 15. 6m m 2 . The MIMO system consists of two symmetrically placed monopoles. A stepped slot ended with an ellipse on the ground plane is etched to reduce the mutual coupling between the two monopoles. The overall dimension of this MIMO system is 50 × 50 mm 2 . The prototype of the antenna is fabricated and measured. Measured results show that the antenna's impedance bandwidth is 450 (18%), 350 (10%), 1200 (21.8%) MHz at the three resonant frequency points (2.5 GHz, 3.5 GHz, 5.5 GHz) with mutual coupling between the antenna elements less than �18 dB in whole frequency band, making this antenna a good candidate for portable application.

A compact coplanar waveguide-fed tri-band monopole antenna for WLAN/WiMAX applications is proposed. By employing a pair of inverted-L slots etched on the ground plane and a split-ring resonator (SRR) and further carefully adjusting the lengths and positions of these structures, two notched bands can be obtained. Measured results show that a tri-band of 280MHz (2.28–2.56 GHz), 920MHz (3.29–4.21 GHz), and 860MHz (5.05–5.91 GHz) with reflection coefficient less than −10 dB is obtained covering all the 2.4/5.2/5.8 GHz WLAN bands and 3.5/5.5 GHz WiMAX bands. In addition, good dipole-like radiation characteristics over the required bands is achieved in both Eand H-planes.

Stepped impedance resonator (SIR) and asymmetric coupled-line sections are used to design a novel fifth-order wideband bandpass filter in this paper. Even- and odd-mode technique is introduced to design and analyze the filter. The proposed filter possesses the characteristics of spurious-free response up to the third harmonic frequency with two transmission zeros on each side of the passband, thus resulting in the improved selectivity. One prototype with 3-dB fractional bandwidth of 53% (2.2–3.79 GHz) is fabricated for demonstration, and good agreement can be observed between simulated and measured results.

A wideband planar printed quasi-Yagi antenna with band-notched characteristic is presented. The proposed antenna consists of a microstrip-to-slotline transition structure, a gradient driver dipole, and two parasitic strips as directors. Meanwhile, the arms of the driver and two directors are rotated in a certain angle to improve the gain. To avoid the frequency interference from WLAN operating in the frequency band from 5.15 GHz to 5.825 GHz, an L-shape slot etched on the driver dipole is adopted to achieve a notched band ranging from 4.8 GHz to 6.1 GHz. The ground plane is symmetrically added two stubs to implement the lateral size reduction. The measured bandwidth, determined by the reflection coefficient less than −10 dB, covers from 3 GHz to 10.8 GHz. Better than 8.1 dB F/B ratio and the measured antenna gain varying between 4.7 and 8.3 dBi are also achieved in the operating bandwidth excepting in the notched band.

A broadband CPW-fed circularly polarized square slot antenna for ultra-high-frequency (UHF) radio frequency identiflcation (RFID) applications is proposed. It consists of a square slot embedded with a spur line along diagonal and an F-shaped feeding structure. The proposed antenna achieves an impedance bandwidth about 307MHz (34.6% @886MHz) and a 3dB axial ratio (AR) bandwidth about 232MHz (24.3% @954MHz). The 3dB AR beam-width is about 96 degrees over the UHF band of 840{960MHz. The proposed reader antenna based on CPW structure is easy to integrate. With the symmetry and bidirectional radiation pattern, there are less readers needed in some applications, such as access control, than the reader with unidirectional pattern, which will deflnitely decrease the implemented cost. Therefore, this universal design with desired performance across the entire UHF RFID band (from 840MHz to 960MHz) can be applied to all the UHF RFID applications worldwide. Detailed considerations of the design and main parameters will be studied in this paper.

A closely spaced dual-band notched UWB MIMO antenna is proposed in this paper. A traditional semi-circular monopole with ultra-wideband operation is chosen as an element of the proposed MIMO antenna. When two of the UWB monopoles are put together closely, the mutual coupling between them is apparently strong. To reduce the coupling between the antenna elements, a T-shaped branch is inserted between them, which reduces the mutual coupling obviously over the entire operating band. Also, the T-shaped branch can perform as a compensating radiator which can lower the operating frequencies of the proposed antenna. In order to achieve dual band-notched characteristics, meandering slots are cut in the patches, and symmetrical C-shape strips are nearly placed to the monopoles' feed-lines. The meandering slot is for lower band notch (WiMAX, 3.3{3.7GHz) while the C-shape strips are for upper band (WLAN, 5.15{5.825GHz). The measured radiation e-ciencies, peak gains and radiation patterns are illustrated and show good agreement as anticipated.

A novel compact UWB antenna with 3.5/5.5GHz dual notch-band characteristics is presented. The proposed antenna has a simple structure and compact size of 30 £ 35mm 2 . Firstly, a compact modifled rotated monopole antenna that covers UWB band is achieved. Then by inserting a ‚/4 stub and etching two symmetrical ‚/4 L-shape slots on the UWB antenna achieved before, a dual band-notched ultra-wideband antenna is obtained. The prototypes of UWB antenna with and without notched bands were fabricated and measured. Good performance of dual notched bands, stable gain and omnidirectional radiation patterns make the proposed antenna promising for UWB application.

Equilateral-triangular slot antennas with modifled edges for wideband circular polarization are proposed in this paper. Circular polarization was flrstly obtained by adding two asymmetric perturbations to two edges of triangular slot. Then fractal-like boundaries were adopted in the antenna design for size reduction and broadband operation. Two antenna prototypes for RFID readers were fabricated to cover RFID UHF band and ISM 2.4GHz band, respectively. Measured results show that the presented antennas obtain fairly wide 3-dB axial ratio bandwidths of 15.7% (820{960MHz) and 19.8% (2.18{2.66GHz).

A novel broadband planar rotated cross monopole antenna, which consists of a vertical patch (area A) and a rotated horizontal patch (area B), is proposed. By rotating the horizontal patch, the bandwidth of the proposed antenna can be signiflcantly enhanced. The efiect of the rotated angle of the horizontal patch on the bandwidth has been deeply studied. The measured results show that the proposed antenna with compact size of 50 £ 50mm 2 can achieve a wide impedance bandwidth (10-dB re∞ection coe-cient) as large as 8.76GHz (2.33{11.09GHz) or about 130%, which is nearly two times of what the corresponding conventional cross monopole antenna was.

A compact multiple-input-multiple-output (MIMO) antenna that covers the WLAN (2.4GHz) and UWB (3.1{10.6GHz) bands for wireless device applications is presented. The proposed antenna consists of two open L-shaped slot (LS) antenna elements and a narrow slot on the ground plane. The antenna elements are placed perpendicularly to each other to obtain a high isolation, and the narrow slot is added to reduce the mutual coupling between antenna elements at the WLAN band (2.4GHz). The presented MIMO antenna has a small size of 40£40mm 2 , and the prototypes of antenna is fabricated and measured. The measured results show that the antenna has an impedance bandwidth of larger than 2.4{10.6GHz with the mutual coupling less than 20dB in WLAN band and 18dB in 3.1{10.6GHz, making the antenna a good candidate for portable applications.

A dual circularly polarized (CP) antenna is proposed in this paper. By employing suspended strip line to feed the patch at the two diagonal positions with 90 ◦ phase difference, single circular polarization is firstly obtained. Then dual circular polarization is excited by an L-shaped strip. The two feeding ports near the edges of the L-shaped strip arms provide the conversion between left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP). Measured results show that the proposed antenna has 10-dB return loss bandwidth of 30.5% (2.08-2.83 GHz), 10-dB isolation bandwidth of 15.7% (2.29-2.68 GHz), 3-dB axial ratio (AR) bandwidth of 25.1% (2.16-2.78 GHz).

This study proposes a difierential-fed microstrip antenna, which is characterized with an ultra-wideband of 120% (3{12GHz), improved radiation patterns, stable gains, and compact size. Two symmetrical trapezoid shaped slots and four triangle-cut corners on the ground are used to improve the impedance matching over the UWB frequency band. To clarify the improved radiation characteristics, the simulated radiation patterns of the proposed antenna are compared with the conventional single- ended feed UWB antennas. The measured results show that, in the entire frequency band, the designed antenna exhibits a stable radiation patterns and the gain variation is less than 2dB. Furthermore, the polarization purity are increased compared with the conventional ones, especially in the high frequency band.

A novel wideband bandpass filter (BPF) based on signal-interaction concepts is presented in this paper. Two transmission paths with a wideband double-sided parallel-strip line 180° inverter and a 3λ/4 transmission line are employed to transmit signals from Port 1 to Port 2. By introducing two λ/4 shorted lines, the passband transmission performance of the BPF can be improved effectively. The experimental results demonstrate that the proposed BPF can achieve three transmission zeros and good harmonic suppression in the whole operating band ranging from 1.35 to 3.41 GHz, with 3-dB fractional bandwidth of 86%.

A simple wideband antenna with parasitic element is proposed in this paper. The printed antenna is comprised of an L-shape monopole and a parasitic element. By optimizing geometrical parameters of the parasitic element structure, a good impedance bandwidth which covers DVB (470MHz»702MHz) for return loss being higher than 5dB and LTE/700 (704MHz»787MHz), GSM850/900 (824MHz»894MHz/880MHz»960MHz) for return loss being higher than 10dB is achieved. The protype of the antenna is in size of 150mm £ 56mm. The measured and simulated e-ciency, gain and radiation pattern which is quasi omni-directional in the yoz plane make it to be a good candidate of mobile communicational terminals.

In this paper, a novel miniaturized branch-line coupler (BLC) operating at 1.675GHz is proposed. Partially meandered lines and dual transmission lines equivalent technology are used as the coupler's shunt arms, producing signiflcant reduction by more than 68% compared with the conventional coupler. Moreover, the coupler can equally divide the input signal with 90 - phase of difierence while maintaining the initial power from the source with a simple structure. The simulated and measured results are in good agreement, thereby verifying the design concept.

In this study, a novel dual band-notched ultra-wideband (UWB) antenna has been proposed and discussed. The proposed antenna is fed by a micro-strip line and in the square-etched radiation patch a T-shape parasitic stub is attached. On the other hand, a pair of parasitic parallel micro-strip lines are also added on the ground plane, one of which is shorted to the radiation patch by a short-pin through dielectric substrate. The two parasitic units are to achieve band- notched characteristics at 3.3{3.7GHz and 5.15{5.85GHz, respectively. In order to realize impedance matching over the ultra-wideband, two arc-shape cuts are made symmetrically at the junction of feed-line and radiation patch. The simulated and measured results, including return loss, radiation pattern, group-delay and peak gains are in good agreement with theory analysis which validates our design concept.

Square slot antennas with modifled edges for broadband circular polarization are presented. Slots with only stubs or notches are studied and it is found that the axial ratio (AR) bandwidth is quite sensitive to the perturbations of the stubs and notches. To further enhance the AR bandwidth, slot antennas with combination of stubs and notches are proposed and wide 3-dB AR bandwidth of 15.5% (2.45{2.86GHz) is obtained. By placing a conducting re∞ector at the rear of the slot, another modifled square slot antenna is designed for practical applications, which achieves a 3-dB AR bandwidth of 6.5% (2.38{2.54GHz) and peak gain of 8.7dBic. Agreement between simulated and measured results is satisfactory.

A novel compact dual band-notched ultra-wide band antenna with hexagonal slotted ground is proposed. By inserting two pairs of L-shaped branches symmetrically into the slotted ground plane, two notched bands, 3.3–3.7 GHz for worldwide interoperability for microwave access and 5.15–5.825 GHz for wireless local area network, are achieved, respectively. A prototype of the proposed antenna is designed, fabricated, and tested. By optimizing the length of the L-shaped branches and the gap between them, the desired bandwidth of VSWR (voltage standing wave ratio) less than 2.0 can be achieved, ranging from 2.5 to 11 GHz, except two stop-bands of 3.1–4.0 and 5.0–6.0 GHz. The simulated and measured results of the proposed antenna have shown a reasonable agreement between them. The proposed antenna has a compact size, ultra wide bandwidth, good radiation characteristics, and good time-domain behaviors. It is very suitable for modern wireless communication applications.

A novel dual-band dual-polarized antenna design with high isolation and low cross-polarization is presented. An arc-coupled annular ring and a special coaxial-fed slot patch are employed as the radiating elements at lower and upper bands, respectively. Measurements show that the 10-dB impedance bandwidths reach 27.9% (1.66–2.19 GHz) and 18.4% (5.09–6.12 GHz). The port isolation for both bands is better than 30 dB. Moreover, stable and symmetrical radiation patterns at slanted polarizations are achieved, and the measured cross-polarization level is less than dB within the above-mentioned bands.

A novel coaxial-feed dual-polarized slot antenna with high isolation and low cross-polarization is presented. Special slots are employed for symmetrical radiation patterns at slanted polarization and low cross-polarization under dB, which include two pairs of T-shaped slots and two pairs of cross-shaped slots in the radial directions of a circle patch. Moreover, high isolation of more than 36 dB between the two feeding ports is achieved by introducing two shorting pins. The experimental results demonstrate the proposed antenna is capable to operate over the frequency range of 2.23–2.91 GHz, suitable as the base station antenna for WiMAX applications.

The design of a novel printed dipole antenna with bandwidth enhancement is proposed for wideband applications. The antenna consists of an integrated balun, two rectangular radiating arms and a modified inductive coplanar stripline (CPS) impedance tuner. By adjusting the parameters of the CPS-tuner and the balun properly, a good performance of bandwidth enhancement is achieved. The measured results indicate that the impedance bandwidth of the proposed antenna, defined by 10-dB return loss, is about 73.9% from 2.54 to 5.52GHz. In addition, good omnidirectional radiation characteristics are also obtained over the whole operating band. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1585–1590, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26883

A novel multiband rhombic slot antenna with a truncated corner is proposed for wireless local area network (WLAN) and worldwide interoperability for microwave access (WiMAX) applications simultaneously. By introducing a pair of straight strips and two etched ∩-shaped slots, the proposed antenna can operate in multibands. The prototype of the proposed antenna has been successfully constructed and tested. The 10 dB return loss bandwidths of them are 550 MHz (3.15–3.70 GHz) and 920 MHz (5.05–5.97 GHz), respectively, which can cover both the WLAN bands (5.15–5.35 GHz and 5.725–5.825 GHz) and the WiMAX bands (3.4–3.6 GHz and 5.25–5.85 GHz). In addition, good monopole-like radiation characteristics with sufficient antenna gains are obtained over the operating bands. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1466–1469, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26837

In this article, a novel compact UWB antenna with dual band-notched characteristics is proposed. The original UWB antenna is realized by etching an open-slot on the ground plane. The 5.2- and 5.8-GHz WLAN rejected bands are achieved by inserting a slot on the ground plane and a slot-type split ring resonator inside a circular exciting stub on the front side, respectively. The antenna has a compact structure with an area of 16 × 27 mm2. The small size makes it an excellent candidate for UWB operation. Prototype of the antenna are fabricated and tested. The simulated and measured results show that the proposed antenna achieves a wide impedance bandwidth (VSWR 2) are 4.85–5.37 GHz and 5.68-5.98 GHz. Radiation patterns and antenna gains are also given in this article. Detailed design steps, parametric studies and experimental results for the antenna are investigated in the following section. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1159–1163, 2012

A novel microstrip-fed ultrawideband elliptical antenna with dual band-notched characteristics is proposed and fabricated. Dual band-notched characteristics are achieved by a defected ground structure and using a tuning stub embedded in the microstrip feed line. The operation bandwidth of the designed antenna is from 2.6 to 12 GHz for voltage standing wave ratio less than 2, except two frequency notched bands of 3.2–4.1 GHz for WiMAX and 4.9–6.0 GHz for wireless local area network. Moreover, the proposed antenna provides a good radiation pattern and a relatively flat gain over the entire frequency band excluding the rejected bands. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:780–783, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26625

In this paper, an electromagnetic band-gap (EBG) structure is proposed to achieve tri-band operation for a novel circular slot patch antenna, which is suitable for WLAN and WiMAX applications. The proposed antenna consists of a rectangular radiation patch with an etched circular slot, a circular ring, and a mushroom-like EBG structure, all of which are printed on the top side of the substrate. By embedding a circular ring in the circular slot, the antenna can generate two impedance bandwidths. With the use of EBG structure, the proposed antenna can operate in three separate bands. Simulation results are compared with the measurements, and a good agreement is obtained. The measured results show that the 10 dB return loss bandwidths of the proposed antenna are 530 MHz (2.28–2.81 GHz), 470 MHz (3.29–3.76 GHz) and 1250 MHz (4.87–6.12 GHz), which can cover all the 2.4/5.2/5.8 GHz WLAN bands and 2.5/3.5/5.5 GHz WiMAX bands. In addition, a design evolution and a parametric study of the proposed antenna are prese...

This article presents a compact multiband planar inverted-F antenna design for mobile phone applications. The proposed antenna comprises dual twisted lines, a shorting strip and an L-shaped coupling strip. The dual twisted lines are excited by the coupling strip to generate four resonance modes around 900, 1800, 2100, and 3500 MHz and covers six bands including the global system for mobile communication 850/900 (824–894 MHz), (880–960 MHz), digital communication system (1710–1880 MHz), personal communication system (1850–1990 MHz) universal mobile telecommunication system (1920–2170 MHz) and worldwide interoperability for microwave access (3400–3600 MHz). The antenna shows a planar structure and occupies a very small-size of 15 × 26 mm2, making it especially suit for mobile phone applications. This research performed simulation by high frequency structure simulation and CST to design and analyze the antenna, and a practical structure was fabricated and tested. The measured and simulated return loss show good agreement. Moreover, the radiation patterns and the specific absorption rate are discussed too. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1233–1236, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25996

A novel tri-band monopole antenna design employing Tshaped quasi-self-complimentary (QSC) resonators is presented. The proposed antenna is composed of a pair of symmetrical QSC resonators, an octagonal monopole radiator and two L-shaped slots. By utilizing these structures, the antenna can yield different resonances to cover the desired bands while maintaining small size and simple structure. Based on this concept, a prototype of tri-band antenna is designed, fabricated and tested. The experimental results show that the antenna has the impedance bandwidths of 190 MHz (2.36–2.55 GHz), 680 MHz (3.37–4.05 GHz) and 1760 MHz (5.12–6.88 GHz), which can cover both WLAN in the 2.4/5.2/5.8 GHz bands and WiMAX in the 3.5 GHz band.

In this paper, a novel microstrip antenna with a self-similar flame-shaped slot fed by a microstrip-line is presented, which can work at both 2.4–2.5 GHz (WLAN) and 3.1–10.6 GHz (UWB). A C-shaped slot is etched on the patch to produce a notched band which can eliminate 5.15–5.825 GHz band-limited by IEEE 802.11a and HIPERLAN/2. Effects of varying the C-shaped slot parameters on the antenna's performance show that the notched band can be finely tuned. The proposed antenna is simulated and measured. The measured results agree reasonably with the simulated ones. According to the measured results, the proposed antenna operates at the range of 2.36–11 GHz with VSWR < 2, except the notched band of 4.6–6 GHz for 5 GHz WLAN. The radiation characteristics of the proposed antenna satisfy UWB systems. The size of the actual antenna is 35 × 35 mm2.

An open L-slot antenna with triple-band operation for WLAN and WiMAX applications has been designed and implemented with a slit and a strip, which can be used to generate two band-rejected characteristics. Both the strip and the slit play a very important role in suppressing the dispensable bands. By adjusting the dimensions of the slit and strip, the proposed antenna shows three separated operating frequencies with a bandwidth of 14% from 2.24 to 2.58GHz, a bandwidth of 19% from 3.02 to 3.66GHz, and a bandwidth of 10% from 5.62 to 6.21GHz, respectively. Detailed designs and experimental results are reported in this paper.

In this paper, a novel triple-band monopole antenna with double coupled C-shaped strips for WLAN/WiMAX applications is presented. By adjusting the dimensions of the outer and inner C-shaped strips, three separated impedance bandwidths of 20% (2.28 ∼ 2.78 GHz), 14% (3.33 ∼ 3.83 GHz) and 19% (4.86 ∼ 5.86 GHz) can be obtained. Especially, the asymmetry inner C-shaped strip can be used to adjust the middle and high band characteristics. With these double coupled C-shaped strips, the proposed antenna shows a good triple-band property to satisfy the requirements of 2.4/5.2/5.8 GHz WLAN bands and 2.5/3.5/5.5 GHz WiMAX bands.

A novel microstrip-fed ultra wideband (UWB) elliptical antenna with dual band-notched characteristics is proposed. Dual band-notched characteristics are achieved by employing a pair of U- shaped slots on the ground plane and a T-shaped parasitic strip on the backside of the substrate. The operation bandwidth of the designed antenna is from 2.9 to 12GHz for voltage standing wave ratio (VSWR) less than 2, except two frequency stop-bands of 3.2{3.9GHz for WiMAX system and 4.9{6.1GHz for WLAN system. Moreover, the proposed antenna provides good radiation patterns across the working bands and a relatively ∞at gain over the entire frequency band excluding the rejected bands.

A butterfly-shaped dual-band antenna with low cross-polarization levels is presented. The proposed antenna rame-dipoles nested within each other and a couple of strips. The antenna prototype is designed, fabricated and tested. The experimental results show the antenna covers 2.2–2.74 GHz and 3.15–3.75 GHz bands with 10 dB return loss, satisfying the desired standards of WiMAX application. Besides, the design provides omni-directional characteristics in H-plane and low cross polarization in both H and E planes over the operating bands.

A Y-shaped tri-band monopole antenna is proposed in this paper. The antenna consists of a parasitic M-strip and an elliptical slot etched in the ground. With the helps of the parasitic M-strip and the slot, the Y-shaped monopole antenna can easily obtain tri-band characteristic. The proposed antenna has been constructed and tested. The simulated and measured results show that the proposed antenna has three good impedance bandwidths (VSWR < 2) of 220 MHz (about 26% centered at 1.85 GHz), 580 MHz (about 24% centered at 2.4 GHz) and 886 MHz (about 16% centered at 5.4 GHz), which make it easily cover the required bandwidths for PCS band (1850–1990 MHz), and WLAN band (2400–2480 MHz, 5150–5350 MHz, and 5725–5825 MHz) applications.

In this paper, a technique using a novel cross-shaped defected ground structure (DGS) to broaden the operating bandwidth and reduce the size of a conventional DC bias line is proposed. The conventional DC bias line is composed of a λ/4 high impedance transmission line and a proper fan-shaped capacitor. Due to the slowwave characteristics introduced by the DGS, the original length of the λ/4 high impedance transmission line can be shortened while maintain the same electrical length. The experimental result shows that the proposed DC bias line has a much wider operating bandwidth than that of the conventional one by 153% and 83.3% of the initial λ/4 length.

In this paper, the Powell algorithm design methodology is presented for the synthesis of frequency selective surfaces (FSSs) with circular ring patch elements. The Powell algorithm is a local optimizer. It is used to optimize the element dimensions, periodicity and skewed angle of the array, to produce a band-stop FSS. The mode matching method is employed to efficiently evaluate the fitness of a candidate design. The result shows that the initial design is greatly improved after optimized.

A novel rectangular ring patch antenna with tri-band operation is presented for WLAN and WiMAX applications. The proposed antenna consists of a rectangular ring patch and a pair of straight strips with different lengths. By placing the two strips asymmetrically with respect to the microstrip feed line, the proposed antenna can operate in triple bands. The 10 dB return loss bandwidths of them are 310 MHz (2.39–2.70 GHz), 490 MHz (3.38–3.87 GHz) and 2680 MHz (4.82–7.50 GHz) respectively, which can cover both the WLAN bands (2.4–2.484 GHz, 5.15–5.35 GHz, and 5.725–5.825 GHz) and the WiMAX bands (2.4–2.6 GHz, 3.4–3.6 GHz, 5.25–5.85 GHz). In addition, the overall dimensions of this proposed antenna are 36 mm (length) × 20 mm (width) × 1 mm (thickness), which is compact compared to conventional tri-band antennas.

A very low-profile conical antenna with a simple structure and wideband characteristic is proposed in this article. The antenna structure consists of a monoconical conducting body, a parasitic ring shorted to a finite-sized ground plate to achieve low-profile characteristic (Nakano et al., IEEE Trans Antennas Propag 56 (2008) 1187-1192), and a sleeve attached to the ground for yielding an extreme wide VSWR bandwidth. The experimental result shows that the proposed antenna, with a height of only 0.0625 wavelength at the lower edge frequency of the bandwidth, exhibits a 7.9:1 impedance bandwidth from 747 to 5900 MHz with VSWR below 2.5. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2620–2623, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24713

A novel and compact planar ultra-wideband wide-slot antenna with dual band-notched function is proposed. The method of creating dual band-notch function is unique from traditional ones. By embedding a U-shaped parasitic strip and a pair of T-shaped stubs in the wide slot, dual bandstops around 3.5GHz and 5.5GHz can be obtained. The measured results demonstrate that the proposed antenna, with a compact dimension of 20 × 32.5mm, has a large bandwidth over the frequency band from 2.5 to 11.7GHz with voltage standing wave ratio (VSWR) less than 2, except the bandwidths of 3.3 ∼ 3.7GHz for WIMAX and 5 ∼ 6GHz for WLAN. In addition, the radiation pattern has an excellent omni-directional characteristic in H-plane and a typical monopole-like pattern in E-plane.

A compact ultra-wide band printed monopole antenna with dual band-notched characteristic is proposed. By using only one H-shaped slot etched on the radiation patch, two notched band, 3.3–3.6 GHz for WiMAX and 5.15–5.825 GHz for WLAN, are achieved. Moreover, the size adjustment of the key structure aiming at the band notched characteristic is discussed. The proposed antenna yields an impedance bandwidth of 3.1–10.6 GHz with VSWR < 2, except the notched bands. The antenna is successfully simulated and measured, showing dual band rejected characteristic can be obtained by using the only one H-shaped slot.

Design investigations are presented for double screen frequency selective surfaces (DSFSSs) with multi-resonant elements. The DSFSS is composed of two identical single layer frequency selective surfaces (FSSs) separated by a foam layer. By tuning the thickness of the foam, a four-band FSS with improved S-band performance and a dual-band band-stop FSS with broad bandwidths and rapid rolloffs are designed. Both designs are angle and polarization insensitive. The Fabry-Perot interferometer (FPI) theory demonstrates that DSFSSs with a large distance between the metallic arrays are not suitable for broadband band-stop applications due to the interruptions of undesired transmission peaks, which are the results of array interference. An equivalent circuit model is developed to give an insight into the response of the DSFSS. Experimental verifications are carried out. The calculated results agree well with the measured ones.

A novel fractal triangular monopole antenna with truncated and notched ground for the ultra-wideband (UWB) application is presented and studied in this paper. The proposed antenna is designed based on the fractal theory. By inserting three small triangles and three thin slots central symmetrily in the radiation patch, smaller antenna size and more resonant frequencies in the required frequency range are obtained. The antenna has been simulated, fabricated and measured. It is shown that high performance of the designed-antenna is obtained and the Voltage Standing Wave Ratio (VSWR) requirement of less than 2.0 in the frequency band from 2.6 GHz to 14.26 GHz is well satisfied.

A multifunctional meander line polarizer is described. The polarizer is capable of effecting conversions between linear and circular polarization and between left-hand and right-hand circular polarization. It can also cause arbitrary rotation of linear polarization, including converting a wave from horizontal polarization to vertical. The polarizer is analyzed by the spectral domain approach.