Chang-Fa Yang

Novel CPW-Fed Planar Monopole Antenna for WiMAX/WLAN Applications

A coplanar waveguide (CPW)-fed planar monopole antenna with triple-band operation for WiMAX and WLAN applications is presented. The antenna, which occupies a small size of 25(L) × 25(W) × 0.8(H) mm3, is simply composed of a pentagonal radiating patch with two bent slots. By carefully selecting the positions and lengths of these slots, good dual stopband rejection characteristic of the antenna can be obtained so that three operating bands covering 2.14-2.85, 3.29-4.08, and 5.02-6.09 GHz can be achieved. The measured results also demonstrate that the proposed antenna has good omnidirectional radiation patterns with appreciable gain across the operating bands and is thus suitable to be integrated within the portable devices for WiMAX/WLAN applications.

A New Planar Artificial Transmission Line and Its Applications to a Miniaturized Butler Matrix

A miniaturized quadrature hybrid coupler, a rat-race coupler, and a 4 times 4 Butler matrix based on a newly proposed planar artificial transmission line are presented in this paper for application in ultra-high-frequency (UHF) radio-frequency identification (RFID) systems. This planar artificial transmission line is composed of microstrip quasi-lumped elements and their discontinuities and is capable of synthesizing microstrip lines with various characteristic impedances and electrical lengths. At the center frequency of the UHF RFID system, the occupied sizes of the proposed quadrature hybrid and rat-race couplers are merely 27% and 9% of those of the conventional designs. The miniaturized couplers demonstrate well-behaved wideband responses with no spurious harmonics up to two octaves. The measured results reveal excellent agreement with the simulations. Additionally, a 4 times 4 Butler matrix, which may occupy a large amount of circuit area in conventional designs, has been successfully miniaturized with the help of the proposed artificial transmission line. The circuit size of the Butler matrix is merely 21% of that of a conventional design. The experimental results show that the proposed Butler matrix features good phase control, nearly equal power splitting, and compact size and is therefore applicable to the reader modules in various RFID systems.

Compact Monopole Antenna With Band-Notched Characteristic for UWB Applications

A compact planar monopole antenna with standard band-notched characteristic suitable for ultrawideband (UWB) applications is presented. This microstrip-fed antenna, consisting of a square slot patch with a vertical coupling strip, only occupies a small size of 15 (L) × 15 (W) × 1.6 (H) mm3. By properly designing the strip placed at the center of the patch, good frequency rejection performance of the antenna with a wide operating band from 3.05 to 11.15 GHz can be obtained. Compared to other designs, the antenna has a quite simple structure to make the band-notched property to reduce the effect caused by the frequency interference. Furthermore, fairly good omnidirectional radiation patterns and transmission responses both indicate that the proposed antenna is well suited to be integrated within various portable devices for UWB operation.

A doubly periodic moment method solution for the analysis and design of an absorber covered wall

A periodic moment-method solution for scattering from a doubly periodic array of lossy dielectric bodies is developed. The purpose is to design electromagnetic wedge and pyramidal absorbers for low reflectivity so that one can improve the performance of anechoic chamber measurements. The spectral-domain formulation and the moment-method volume polarization current approach are used to obtain the expressions for determining the scattering from a doubly periodic array of lossy dielectric bodies. Some wedge and pyramidal absorber configurations that have been designed, fabricated, and tested in the OSU/ESL compact range measurement facility are presented. By taking into account the complexity of real-world material structures, good agreement between calculations and measurements has been obtained. >

A periodic moment method solution for TM scattering from lossy dielectric bodies with application to wedge absorber

The periodic moment method (PMM) solution for the scattering from two-dimensional lossy dielectric bodies is developed. The purpose is to design a microwave wedge absorber for low reflectivity so that one can improve the performance of anechoic chamber measurements. With PMM, the reflection and transmission coefficients of periodically distributed bodies illuminated by a plane wave have been accurately calculated using a Cray Y-MP supercomputer. Through these studies, some wedge absorber configurations have been designed, fabricated, and then tested in the OSU/ESL compact range measurement facility. Two 8-in commercial wedges, a curved wedge, and a four-layer wedge, were studied. In all cases, good agreement between calculations and measurements was obtained. >

Simulations and Measurements of Wave Propagations in Curved Road Tunnels for Signals From GSM Base Stations

This paper presents a ray-tube tracing method for wave propagations in curved tunnels. The waves from a transmitting antenna are modeled with many ray tubes, and those ray tubes are traced by including multiple reflections and diffractions from curved structures. Measurements for signals in curved road tunnels from GSM900/1800 base stations have been performed and are compared with those obtained from the ray-tube tracing method.

Compact Multibranch Inverted-F Antenna to be Embedded in a Laptop Computer for LTE/WWAN/IMT-E Applications

A multibranch inverted-F antenna with multiband operations for long-term evolution (LTE), pentaband wireless wide area network (WWAN) and IMT-E (2.6 GHz) applications is presented. The antenna consists of multibranch strips and is fabricated on a direct bond copper (DBC) substrate, which has a compact size of 96 (L) × 11.2 (W) × 0.5 (H) mm3 to be embedded in the laptop computer as an internal antenna. Three operating bands covering 663-993, 1689-2190, and 2449-2783 MHz for the LTE, GSM850/900 and DCS/PCS/UMTS, and IMT-E systems are achieved with good radiation efficiencies. The proposed antenna can be embedded in the laptop computer for the LTE, WWAN, and IMT-E applications.

A Compact Multiband Inverted-F Antenna for LTE/WWAN/GPS/WiMAX/WLAN Operations in the Laptop Computer

An inverted-F antenna with multiband operations for Long-Term Evolution (LTE700/2300/2500), wireless wide area network (WWAN), GPS, WiMAX (2.3/2.5/3.5 GHz), and WLAN (2.4 GHz) applications is presented. The antenna consists of multibranch strips and is fabricated on both sides of an Al2O3 ceramic substrate, which has a compact size of 97 (L) × 11.2 (W) × 0.5 (T) mm3 to be embedded inside the laptop computer as an internal antenna. Four operating bands covering 646-983, 1503-1589, 1696-2963, and 3396-3646 MHz for the LTE, WWAN, GPS, WiMAX (2.3/2.5/3.5 GHz) and WLAN (2.4 GHz) systems are achieved with good radiation efficiencies.

Compact Inverted-F Antenna With Meander Shorting Strip for Laptop Computer WLAN Applications

In this letter, a novel compact inverted-F antenna with dual-band property for WLAN applications is presented. It comes with a C-shaped radiator and two meander shorting strips, which only occupy a small size of 35 (L)3 (W) mm to be easily embedded inside a laptop computer as an internal antenna. This design can radiate with two operating bands covering 2.38-2.54 and 4.99-5.96 GHz. By properly forming these two shorting strips, the effects due to the antenna near the external casing can be suitably tackled for actual application. Nearly omnidirectional coverage to enhance the communication quality can be obtained with our design. Therefore, the proposed antenna with a compact size is well suitable for WLAN operation in a laptop computer.

Miniaturized Branch-Line Coupler with Harmonic Suppression for RFID Applications using Artificial Transmission Lines

A miniaturized branch-line coupler based on a newly proposed planar artificial transmission line (ATL) is presented in this paper for UHF RFID applications. This planar artificial transmission line consists of quasi-lumped elements and their discontinuities, and can synthesize microstrip lines with a wide variety of characteristic impedances and electrical lengths. The measurement results agree well with the simulation ones. The experiments demonstrate that the proposed hybrid has a compact size of 24.4 mm times 25.8 mm, or equivalently 0.12lambdag times 0.13lambdag at the operation frequency, 915 MHz. This corresponds to a 73% size reduction as compared to that of a conventional branch-line coupler. The wideband response reveals that the proposed hybrid is well-behaved with no spurious harmonics up to 11.1 GHz.