Hong-Twu Chen

A compact meandered circular microstrip antenna with a shorting pin

By using a shorting pin and meandering the circular patch, a compact circular microstrip antenna with a patch size of less than 10% of the conventional circular patch antenna can be easily obtained. The design of such compact circular microstrip antennas is described, and experimental results are presented and discussed.

PIFA with a meandered and folded patch for the dual-band mobile phone application

In this communication, a novel design of the planar inverted-F antenna (PIFA) is proposed for the dual-band mobile telephone application. To reduce the antenna size, the radiating patch is meandered and folded. The studies begin with a folded-patch PIFA that has two tunable resonant modes. Next, by loading three slits on the patch, the surface current path is meandered and the antenna length is reduced significantly. The IE3D simulation software is employed for optimizing the design parameters, and the simulation results in general agree with the measured data. Results also show that, the excitation of the 900 and 1800 MHz resonant modes can be achieved for the proposed antenna with a small volume of 24/spl times/10/spl times/7.2 mm/sup 3/. Radiation patterns for both resonances are measured and shown. The maximum antenna gain is estimated to be 2.5 dBi for both 900/1800 band operations.

Analysis of a hemispherical dielectric resonator antenna with an airgap

A probe-fed hemispherical dielectric resonator antenna with an airgap of hemispherical shape between the dielectric and the ground plane is investigated theoretically by using a Greens function formulation. Input impedance of the efficiently radiating mode of TE/sub 111/ is calculated and analyzed. It is found that, with the presence of the airgap, the antenna bandwidth, obtained from the 3-dB impedance bandwidth, can be considerably enhanced. This study provides a new design for bandwidth enhancement of the dielectric resonator antenna.<<ETX>>

Resonance and radiation of a superstrate-loaded spherical-circular microstrip patch antenna

The effects of the dielectric superstrate cover on the resonance and radiation problems of a spherical-circular microstrip patch antenna are studied, using the Greens function formulation in the spectral domain and the Galerkin moment method calculation. Numerical results for the resonant frequency, half-power bandwidth, and radiation pattern of the superstrate-loaded antenna are presented. The effects of curvature on these characteristics are also shown. >

Novel design of printed monopole antenna for WLAN/WiMAX applications

In recent years, wireless communications have progressed very rapidly. Wide-band antenna and multi-band antenna designs have become very important for wireless communications. Several promising monopole antennas for WLAN and WiMax applications have been reported recently. According to the WiMax protocol, there is three bands have been allocated for WiMax application: the lower band is 2.5-2.69 GHz, the middle band is 3.3-3.8 GHz, and the higher band covers from 5.25 GHz to 5.85 GHz. In practical use of WiMax applications, the lower band and the middle band are very close to each other, which lead to cause large effects of coupling and interference. To reduce the coupling and interference between the lower and middle bands, filters must be attached to the antenna to suppress the dispensable bands. However, the cost and the overall antenna size are increased due to the attached filters. In this paper, a CPW-fed printed monopole antenna for dual-band operation of 2.3-4.15 GHz and 4.93-5.83 GHz are proposed. Furthermore, by etching a pair of slits on the proposed monopole antenna, band rejection of frequency range from 2.93 GHz to 3.12 GHz can be achieved. Results show that, this novel design of CPW-fed monopole antenna is suitable for both WLAN and WiMax applications.

Resonance in a spherical-circular microstrip structure with an airgap

The resonance problem of the spherical-circular microstrip structure with an airgap between the substrate layer and the ground conducting sphere is studied by using a rigorous Greens function formulation in the spectral domain and Galerkins moment method calculation. Complex resonant frequencies are obtained in this study, which provide the resonant frequencies and half-power bandwidth of the structure. From the numerical results, it is found that with the increasing of the airgap thickness, the half-power bandwidth of the structure is considerably increased. This improves the low-bandwidth characteristics of microstrip structures. Details of the numerical results are presented and discussed. >

Planar inverted-F antenna with a hollow shorting cylinder for internal mobile phone antenna

Planar inverted-F antennas (PIFAs) have been very popular as an internal antenna in small handheld wireless communication devices. Recently, in many wireless devices, a digital camera is embedded and is in competition with the PIFA internal antenna for the very limited space on the system circuit board. We propose a novel design of the PIFA with a large hollow shorting cylinder for application in a mobile phone with an embedded digital camera. The hollow shorting cylinder has a large diameter (8 mm in this case), and it is easy to fit the lens of a practical embedded digital camera inside it. In this case the proposed PIFA and the embedded digital camera together occupy a minimum space, and very small or negligible coupling effects of the embedded camera with the PIFA are expected. A design example of the proposed PIFA for application in a UMTS (Universal Mobile Telecommunication System, 1920-2170 MHz) mobile phone is demonstrated. The experimental results obtained are also presented.

Dual-polarized probe-fed patch antenna with highly decoupled ports for WLAN base station

In this paper we present a novel dual-polarized patch antenna using two probe feeds for achieving high port decoupling. By using a thick air-layer substrate, which makes possible a wide impedance bandwidth. The two probe feeds have a short probe pin and a triangular transition patch (F.S. Chang and K.L. Wong, Microwave Opt. Technol. Lett. vol. 30, pp. 341-343, 2001), which makes good impedance matching over a wide frequency range very easy to obtain. In addition, an additional shorted inverted-L patch is added, which is for the purpose of decreasing the excited patch surface currents flowing from the excited port toward the other one, such that great improvement in port decoupling can be obtained. Details of the proposed design are described, and a prototype suitable for the dual-polarized WLAN base-station application at 2.45 GHz band (2400-2485 MHz) is constructed and studied.

Analysis of spherical-circular microstrip antennas on a uniaxial substrate

Many substrate materials commonly used for microstrip antennas exhibit uniaxial anisotropy, and several related studies have been published. However, these studies on uniaxial substrates have been confined to planar microstrip antennas. Since conformal capability is one of the major advantages of microstrip antennas, the study of conformal microstrip antennas on a uniaxial substrate is also worthy of investigation. This motivates the present paper for the analysis of spherical-circular microstrip antennas on a uniaxial substrate. For the study, the Greens function in the spectral domain is first formulated, and Galerkins moment method incorporating the cavity-model basis functions is then used for calculating the complex resonant frequency of the microstrip structure, which gives the information of the resonant frequency and the half-power bandwidth of the patch antenna. Furthermore, the probe-feed excitation is also included in the study. The surface current distribution on the circular patch is calculated and shown. The copolarized and cross-polarized fields are also calculated.<<ETX>>

A novel broadband antenna for WLAN applications

This paper presents a novel monopole antenna backed by a U-shaped ground plane and broadside radiation for broadband dual-frequency operation. By varying the angle of inclined ground plane, dual-band operation with its operating mode center at about frequency 2.4GHz, 5.2GHz and 5.8GHz have been obtained. Good broadside radiation characteristics for the proposed antenna have also been observed.