Weihua Tan

Radiation of High-Gain Cavity-Backed Slot Antennas Through a Two-Layer Superstrate

The radiation of cavity-backed slot (CBS) antennas through a two-layer superstrate is studied in this paper. A novel transmission-line model is proposed to explain the gain-enhancement effect of the superstrate on cavity-backed slot antennas. Experimental result showed that a single cavity-backed slot antenna can achieve a high gain of 16.7 dBi through a properly designed superstrate, and this gain-enhancement property is valid for array configurations, as well. A rotationally arranged four-slot array, covered by the superstrate, is also investigated, to demonstrate that good circular polarization and high gain can be obtained from the superstrate-covered slot antennas.

A gain-enhanced microstrip-fed cavity-backed slot antenna

This paper describes a gain-enhanced cavity-backed slot antenna. A superstrate of high permittivity is placed at a certain distance above the substrate to enhance the gain of the slot antenna. The cavity-backed slot antenna is fed by a microstrip line printed on the top of the substrate. Both simulation results and experimental measurements show that this superstrate-covered cavity-backed slot antenna can attain a high gain, while it retains the broadband impedance characteristics.

Efficient Analysis of Open-Ended Coaxial Line Using Sommerfeld Identity and Matrix Pencil Method

An efficient method for calculating the reflection coefficient matrix of open-ended coaxial lines with an infinite flange is proposed in this letter. The matrix equation containing double surface integrals on the aperture can be derived using the mode-matching method. These surface integrals are then converted to line integrals in the spectral domain by the Sommerfeld identity. Then the matrix pencil method is employed to fit the integrands with exponential series so that the integrals can be analytically expressed in closed form. An open-ended coaxial line is considered to verify the validity of the formulation. It is shown that the proposed method is very efficient in calculating the reflection coefficient matrix of open-ended coaxial lines.

A planar multi-band antenna for portable devices

In this paper, a broad band printed antenna has been described and its measured performance has been provided. Two symmetrical patches, each of which is composed of two half ellipses sharing a common axis, have been used to realize the broad band characteristics. Measured results have shown that this design has a -10 dB return loss bandwidth from 470 MHz to 3.8 GHz, which spans the UHF band, GSM 900 MHz, GSM 1800 MHz band and 2.4 GHz band for 802.11b wireless LAN. Because of its good performance, this antenna is very suitable to be applied to portable devices such as laptops, tablet PCs or PDAs

Wide-Band Wide-Coverage Linear Array of Four Semi-Circular Sector Horns

A linear array antenna consisting of four semi-circular sector horns is proposed to achieve wide-band and wide-coverage radiation characteristics. The array can operate over a wide frequency band from 850 MHz to 2570 MHz and cover a wide range of 120° in the azimuth plane. Each semi-circular sector horn is fed by a centred coaxial probe loaded with a conducting cylinder to obtain a wide-band and symmetric radiation pattern of vertical polarization. Measured and simulated results of a designed array show its potential applications for base stations serving wide-range mobile users and other wide-band spectrum-monitoring systems.

Design of a wide-band high-gain linear array antenna

This paper presents a novel design of wide-band high-gain linear array antenna. The operating frequency of the array antenna is from 890MHz to 2500MHz. The antenna radiates or receives vertically polarized waves and can cover a sectored range of 120° in the azimuth plane. The minimum gain of the array antenna is 10dBi over the entire frequency range covering the whole sector. Measured results for a two-element array are in excellent agreement with simulated ones. This array antenna should be very useful for base stations serving wide-range mobile users and can be readily scaled to other ultra-wideband applications.

A Circularly Polarized Microstrip-Fed T-Slot Antenna Array on a Conducting Cylinder

A circularly polarized T-slot antenna array wrapped on a conductive cylinder is presented in this letter. This cylindrical antenna array consists of four independent cavity-backed T-slot elements, which are fed by four microstrip lines. The designed array is to be used in a switched-beam mode so that the arrays radiation beam can be selected using a single-pole 4-throw (SP4T) switching circuit. Simulated and measured results show that the radiation pattern of each element is able to cover a quadrant in the horizontal plane while the radiated wave in each quadrant is circularly polarized. Furthermore, the four elements are well isolated and exhibit wide bandwidth. Measured results of one slot element in the array configuration show that it has a 13.8% bandwidth for

A Dual-Band Dual-Sleeve Monopole Antenna

10~ dB

Efficient Analysis of Open-Ended Waveguides Using Sommerfeld Identity

return loss and a 7% bandwidth for 3 dB axial ratio.

A dual-band beam-switched slot array for GSM 900/1800MHz

This letter proposes a dual-band monopole antenna with two sleeves. The lower sleeve is short-circuited to the monopole at its bottom end, while its top end is an open circuit since the length of the coaxial line formed by the sleeve and the monopole is one quarter-wavelength at the higher operating frequency. Meanwhile, the upper sleeve is so designed that a short circuit is produced across the gap between these two sleeves at the lower operating frequency, and therefore, these sleeves are virtually connected. As a result, this antenna is able to operate like a quarter-wavelength monopole at both frequency bands. A prototype of this dual-sleeve monopole is fabricated, and its measured results are in good agreement with simulated ones. It is found that this dual-sleeve monopole not only has good impedance matching, but also can radiate like a quarter-wavelength monopole at both bands.