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In this paper, a wide-band scattering of one-dimensional (1-D) soil surface with exponential spectrum is investigated by the finite-difference time-domain (FDTD) algorithm with pulsed wave excitation. Soil is regarded as isotropic and dispersive media, and it satisfies the two-pole Debye model. And the auxiliary differential equation (ADE) technique is incorporated into the FDTD scheme to deal with the dispersive soil. To ensure the validity of our present method, the wide-band scattering of dispersive soil surface by the ADE-FDTD method is computed and compared with the result by the conventional method of moments (MOM), which requires an individual calculation for every frequency point of interest. Finally, the scattering characteristic of dispersive soil surface is analyzed for different parameters in detail. [ABSTRACT FROM PUBLISHER]

A CPW-fed slot antenna for achieving dual-band dual-sense circular polarization is introduced. The dual-band circularly polarized operations are generated by the slots loaded in the two opposite corners and the halberd-shaped strip connected at the end of the signal line of the CPW. The left-hand and right-hand circularly polarized performances can be achieved simultaneously for the lower and the upper band, respectively. The measured impedance bandwidth for 10-dB return loss at 2.5 and 3.5 GHz operating bands can be up to 1100MHz and 260 MHz, respectively. The measured 3-dB axial ratio bandwidths are 30.8% for lower band (LHCP) and 3.1% for upper band (RHCP), which are completely inside their respective impedance bands. The designed antenna has a simple uniplanar structure and occupies a compact size of 40 x 40mm², including the finite ground CPW feeding mechanism. Moreover, the antenna gain variations across the two operating bands are less than 1 dB. [ABSTRACT FROM AUTHOR]

A novel broadband monopole antenna design with wideband circular polarization (CP) characteristic is presented. This antenna consists of a feed line and a step-shaped ground plane which is formed by cutting a notch in the upper left corner of an asymmetric ground plane. The asymmetric ground plane is capable of exciting two orthogonal electric field vectors with equal amplitude and 90° phase difference (PD) for CP. By cutting a notch, the 10-dB impedance-bandwidth can be enhanced greatly and the 3-dB axial ratio (AR) bandwidth is also improved meanwhile. The measured impedance- bandwidth is about 5.96 GHz (84.7%) from 4.06 to 10.02 GHz, and the measured AR-bandwidth is about 2.64 GHz (36.5%) from 5.91 to 8.55 GHz. The results show that the antenna can achieve wide impedance-bandwidth and wide AR-bandwidth simultaneously. [ABSTRACT FROM AUTHOR]

This paper presents a novel CPW-fed band-notched UWB antenna for the 3.5GHz wireless local area network (WiMAX) applications. The prototype consists of planar diamond shaped monopole and ground plane. By inserting a novel coupling band- notched filter, which consists of an isosceles trapezoid slot in the radiation patch and a same sized isosceles trapezoid patch on the back of the substrate, with the slot connecting to the patch below through shorting hole, band-rejected filtering property in the WiMAX band is achieved. The proposed antenna is successfully designed with broadband matched impedance, good radiation patterns and constant group delay. [ABSTRACT FROM AUTHOR]

In this paper, a novel design of open slot antenna for bandwidth enhancement is proposed and investigated. The bandwidth enhancement of the proposed antenna is achieved by simply attaching a rectangular stub to the circular radiating patch. Experimental results indicate that the bandwidth of the antenna can achieve an operating bandwidth of about 139% over a wideband frequency range from 2.57 to 14.23GHz. This antenna has a small size of dimensions 20 x 35 mm² and is suitable for wideband applications in various wireless communication systems. [ABSTRACT FROM AUTHOR]

A novel coplanar waveguide (CPW) fed wide tapered slot antenna (WTSA) is presented in this paper. A wideband CPW-to-wide slotline (WSL) transition is employed to feed the antenna. The corrugated edge structure and broken line tapered profile are also applied in this design to achieve wideband performance, as well as maintain compact size. A prototype of the antenna is fabricated. The measured results indicate that the antenna is a good candidate for UWB detection and imaging applications. [ABSTRACT FROM AUTHOR]

This article presents a compact dual band-notched UWB antenna with a pair of L-shaped and modified L-shaped slots on either side of the ground plane for the 3.5/5.5GHz dual band-notched characteristics. The radiating patch of the proposed antenna has a ladderlike structure symmetrically and fed by a 50-Ω microstrip transmission line. By etching two sets of L-shaped slots on the ground plane, dual band-notched properties in the WiMAX/WLAN bands are achieved, respectively. The proposed antenna has the promising performance including matched impedance, consistent radiation pattern and stable gain. [ABSTRACT FROM AUTHOR]

In this letter, a modified broadband 90° phase shifter is proposed. By using a dentate microstrip and a patterned ground plane, an extremely tight coupling can be obtained, and consequently a constant phase shift over a wide bandwidth can be achieved. To verify the proposed idea, a topology is implemented, the measured results of a phase difference of 90 ± 5° in 79.5% bandwidth, better than 10 dB return loss across the whole operating band, are also given. The measurement results agree well with the full-wave electromagnetic simulated responses. [ABSTRACT FROM AUTHOR]

A compact ultra-wideband (UWB) printed monopole antenna with triple band-notched characteristic is proposed. By using a single C-shaped slot etched on the radiation patch, a notched band for WiMAX (3.3-3.7 GHz) is achieved. Moreover, two layer substrates are used, and two resonators are placed between the feed line and the ground plane, which achieves another two notched bands (4.95-5.36 GHz and 5.6-5.94 GHz). The proposed antenna yields an impedance bandwidth of 2.75-11.4 GHz with VSWR < 2, except the notched bands for WiMAX and WLAN application. The simulated and measured data show that there is a good tri-band-notched characteristic. Also, near omni-directional radiation characteristics are obtained in desired frequency range. [ABSTRACT FROM AUTHOR]

In this article, a compact ultra-wideband monopole antenna with dual band-notched characteristic is proposed, in which the C-shaped slot creates one band-notch at 3.5 GHz, and the pair of inverted-L-shaped slots produce another band-notch at 5.8 GHz. Simulated and measured results show that the operating frequency band (VSWR < 2) of the proposed antenna is from 2.7 to 11.5 GHz, with the dual bands of 3.3–3.7 GHz and 5.5–6.4 GHz notched. By changing the lengths of the C-shaped slot and the pair of inverted-L-shaped slots, the central frequencies of the dual notched bands can be adjusted easily. [ABSTRACT FROM AUTHOR]

This paper proposes a novel planar Wilkinson power divider operated in 2.4 GHz/UWB with a notch characteristic in the 5.2 GHz WLAN band (4.7–5.7 GHz) by using a simple defected ground structure (DGS). Over the whole operating band except the notched frequency band, the measured results explore broadband operation with return loss of higher than 10 dB, a low insertion loss of less than 0.8 dB and good isolation of higher than 10 dB. It shows good agreement with the simulation results. [ABSTRACT FROM AUTHOR]

A novel microstrip-fed logarithmically tapered slot antenna (TSA) for wideband applications is presented. The wideband impedance matching and antenna gain are improved by introducing a logarithmically tapered slot. The experimental results demonstrate that this antenna achieves an impedance bandwidth ratio of 15.5:1 for VSWR ≤2 from 0.89 to 13.80 GHz and has an antenna gain varying from 4.2 to 15.6 dBi and a cross-polarization level of more than 15 dB within the operating frequency range. The performances of the TSAs with different shapes of the tapered slot over a wide bandwidth are also compared and discussed in detail. [ABSTRACT FROM AUTHOR]

A small size microstripline-fed linearly tapered slot antenna (LTSA) with the design of tilt grooves is presented in this paper. A parameter discussion of the grooves shows some important features affect the wide-band and wide-beam characteristic of the antenna. By adopting the tilt grooves, impedance bandwidth is increased and improved across a broad frequency band. The low frequency is largely improved compared with the identical LTSA without grooves. Measured results of the half-power beamwidth (HPBW) of the proposed antenna show an excellent characteristic of radiation pattern at the frequency of 7.5 GHz, 9 GHz and 11 GHz, which make it a good candidate for wide-scan phased arrays. [ABSTRACT FROM AUTHOR]

In this article, a new design of a broadband dual circularly polarized square slot antenna loaded with metallic strips is presented. The proposed dual circular polarization (CP) radiations are achieved by loading the square slot with a T-shaped strip and two microstrip T-junctions. The designed antenna is implemented and measured. The experimental results show that the proposed antenna has good dual CP characteristics and a 3-dB axial ratio bandwidth is more than 19%. The isolation between two ports is better than 20 dB within the CP operating band. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2639–2642, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23741 [ABSTRACT FROM AUTHOR]

In this paper, a broadband CPW-fed slot antenna with a gradual-changed ground plane for bandwidth enhancement is proposed and experimentally studied. The effect of various shapes of the slot on broadband operation is investigated. From the experimental results, the measured impedance bandwidth, defined by 10 dB return loss, could be as large as 3.75 GHz or about 105% centered at about 3.56 GHz. The antenna radiation patterns within the operation band were also measured and studied. [ABSTRACT FROM AUTHOR]

A compact ultra-wideband (UWB) microstrip-fed planar monopole antenna with the band-notched characteristic is presented. This antenna comprises an annular-shape radiating element and a tuning stub which is inserted into the annular structure to obtain the band-notched characteristic. The notch frequency can be easily adjusted from 5 to 6.3 GHz by tuning the length of the stub. The VSWR characteristic from (3–24 GHz) and quasi omni-directional radiation pattern is observed. The proposed antenna is suitable for all UWB communication applications and prevents interference with the WLAN systems. [ABSTRACT FROM AUTHOR]

This paper proposed a frequency reconfigurable CPW center-fed slot antenna. Four pin-diodes are utilized to switch the length of the slot. By tuning the different pairs of diodes on or off, three resonant frequency bands can be obtained. The simulated and measured results validate this concept. This antenna architecture is interesting for wireless applications because it is easily fabricated and integrated with RF circuitry. [ABSTRACT FROM AUTHOR]

In this article, a novel particle swarm optimization method based on IE3D is used to design a low-profile modified U-slot microstrip antenna. The antenna is printed on a substrate thickness of 0.008λ. Details of the particle swarm optimization method based on IE3D are presented. Experimental results including return loss and far field patterns of the antenna are given. The obtained antenna bandwidth (S11 = -10 dB) can be as large as 1.85 times that of a corresponding unslotted rectangular microstrip antenna at 2.4 GHz. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1111–1114, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI.10.1002/mop.22369 [ABSTRACT FROM AUTHOR]

A compact broadband microstrip to slotline transition is designed and experimentally studied. An elliptical tapered profile and patches are used to minimise the discontinuity effect of field variation from microstrip to slotline within a short range. A prototype of the back-to-back version transition is also fabricated. Measured results validate the design concept. [ABSTRACT FROM AUTHOR]

A 5.2 GHz band-notched ultra-wideband monopole antenna using a proximity coupled resonator is proposed. Compared with conventional methods which transform antenna/ground structures to achieve band-notches, the proposed monopole antenna uses a coupled resonator to obtain a band-notch at 5.2 GHz and does not change the antenna surface current distribution. Two layer substrates are used and the resonator is placed between the feed line and the ground plane. An experimental prototype was fabricated and the measured data display an impedance bandwidth of 2.5–11 GHz with VSWR<2 except for the rejected band of 5.06–5.52 GHz for HIPERLAN application. Also, near-omnidirectional radiation characteristics in the desired frequency band can be obtained. [ABSTRACT FROM AUTHOR]