Cheng-Li Ruan

A PLANAR U TYPE MONOPOLE ANTENNA FOR UWB APPLICATIONS

An ultra-wideband (UWB) U type monopole antenna fed by a coplanar waveguide (CPW) is proposed. It has low profile and very compact size (14.48 mm × 28.74 mm × 0.8 mm). It provides an wide impedance bandwidth ranging from 3.08 GHz to about 12.75 GHz adjustable by variation of its parameters, such as the relative permittivity and thickness of the substrate, width, and feed and ground plane dimensions. Parametric study is presented. Details of the proposed ultra-wideband design are described. Simulation results are presented and discussed in this paper.

UWB Band-Notched Monopole Antenna Design Using Electromagnetic-Bandgap Structures

A new approach is proposed to reject certain bands within the passband of an ultra-wideband planar monopole antenna. The proposed approach that utilizes a mushroom-type electromagnetic-bandgap (EBG) structure is proven to be an effective way for band-notched designs. The approach has many advantages, such as notch-frequency tunability, notch-band width controllable capacity, efficient dual-notch design, and stable radiation patterns. Several design examples using conventional mushroom-type EBG and edge-located vias mushroom-type EBG are presented. The examples exhibit good bandstop characteristics to reject the wireless local-area network interference bands (5.2- and 5.8-GHz bands). Besides, the causes that lead to the discrepancies between the simulations and measurements are discussed.

A NOVEL ULTRA-WIDEBAND BOW-TIE SLOT ANTENNA IN WIRELESS COMMUNICATION SYSTEMS

Anovel ultra-wideband bow-tie slot antenna fed by CPW is proposed in this paper. This antenna has been demonstrated to provide an UWB with return loss less than −10 dB from 9.5 GHz to 22.4 GHz. The bandwidth is up to 80%, which is quite better than the traditional bow-tie slot antenna. Simulated and measured results are presented.

Design and Operation of Dual/Triple-Band Asymmetric M-Shaped Microstrip Patch Antennas

Novel designs for compact dual/triple-band microstrip antennas are proposed with an asymmetric M-shaped patch. The designs utilize vias on the longer arm of the patch for the purposes of compactness and separating of the operational bands. As the two resonant frequencies of antenna 1 are related to certain parts of the patch, one resonant frequency can be flexibly tuned with little effect on the other. A prototype of antenna 1 operating at 2.44 and 5.77 GHz is fabricated and measured. It has a low profile of 0.016 λr1, where λr1 is the wavelength of the first resonant frequency fr1 = 2.44 GHz at free space, and a compact patch size of 0.195 λr1 × 0.177 λr1. The antenna also presents low cross polarization and symmetrical patterns in both E- and H-planes. Finally, a triple-band antenna (antenna 2) with enhanced bandwidth is designed.

A Novel Band-Notched Elliptical Ring Monopole Antenna with a Coplanar Parasitic Elliptical Patch for UWB Applications

A novel band-notched ultra wide-band antenna with a coplanar parasitic elliptical patch in an elliptical ring is presented in this paper. Printed on a dielectric substrate of FR4 with relative permittivity of 4.4 and fed by a 50Ω microstrip line, the proposed monopole antenna demonstrate a 10 dB return loss bandwidth of 2.91–11.91 GHz, with a band-notched at 5.15–5.98 GHz band and good radiation patterns. The proposed antenna is utilize the coplanar parasitic elliptical patch to reject the frequency band (5.15–5.85 GHz) limited by IEEE802.11a and HIPERLAN/2. The parameters which affect the performance of the antenna in terms of its frequency domain characteristics are investigated in this paper.

A NOVEL COMPACT ARCHIMEDEAN SPIRAL ANTENNA WITH GAP-LOADING

A novel compact Archimedean spiral antenna with gap- loading is investigated in this paper. A circular frame sharing the same centre with the spiral elements introduces a capacitive gap. By adjusting the width of the gap and the width of the circular frame, the initial resonant frequency of the proposed antenna is shifted from 2.79 to 1.93 GHz. Compared with the traditional Archimedean spiral antenna with the same lowest operation frequency, the area of the proposed antenna can be reduced by more than 30simulated radiation pattern results.

Design and Time - Domain Analysis of Compact Multi - Band - Notched UWB Antennas with EBG Structures

Four ultra-wideband (UWB) antennas are proposed: one referenced antenna without notch and three novel antennas with one, two and three notched bands, respectively. The UWB referenced antenna consists of a beveled rectangular metal patch, a 50› microstrip line and a defective ground plane. Then, by utilizing one, two and three electromagnetic band-gap (EBG) structures on the UWB antenna, the antennas present one, two and three notched- band responses, respectively. The frequency domain characteristics including VSWR, transfer coe-cient S21, radiation patterns and group delay are investigated. It is found that the EBG design approach is a good candidate for frequency rejection at the certain frequencies, owing to high performance of notch design and the notched-band bandwidth control abilities. Meanwhile, these abilities also enable less useful frequencies rejected. The design examples exhibit good band- rejected characteristics in the WiMAX/WLAN interference bands (3.4, 5.2 and 5.8-GHz bands). Moreover, good time-domain characteristics of the antennas are checked based on group delay, waveform response, correlation coe-cient and pulse width stretch ratio (SR).

Compact EBG for Multi-Band Applications

A novel electromagnetic band-gap (EBG) structure with a compact size and multi-band-gaps is proposed. The proposed EBG (denoted as DAU-EBG) is formed by etching dual U-shaped slots symmetrically with respect to one axis of the edge-located vias mushroom-type EBG (ELV-EBG). As the surface current paths of the DAU-EBG are prolonged by the etched U slots, the size of our proposed DAU-EBG is only 25.9% of the conventional mushroom-type EBG (CMT-EBG) and 37.3% of the ELV-EBG. Due to the asymmetry introduced by the dual U slots, different band-gap properties in X- and Y-directions are obtained. Three band-gaps and two band-gaps are achieved in X- and Y-directions, respectively. The working mechanism of the proposed EBG and some parameter study are also given. This DAU-EBG can find its use in future compact multi-band rejection applications.

A Novel Compact and Polarization-Dependent Mushroom-Type EBG Using CSRR for Dual/Triple-Band Applications

In this letter, a novel compact electromagnetic band-gap (EBG) structure constructed by etching a complementary split ring resonator (CSRR) on the patch of a conventional mushroom-type EBG (CMT-EBG) is proposed. The first bandgap is defined in all directions in the surface structure. Compared to the CMT-EBG structure, the CSRR-based EBG presents a 28% size reduction in the start frequency of the first bandgap. However, asymmetrical frames of the CSRR-based EBG result in different properties at X and Y-directions. Another two tunable bandgaps in Y-direction are observed. Thus, the proposed EBG can be used for multi-band applications, such as dual/triple-band antennas. The EBGs have been constructed and measured.

A Microstrip Fed Monopole Patch Antenna with three Stubs for Dual-band WLAN Applications

A microstrip fed dual-band design of monopole patch antenna with three stubs is presented in this paper. Printed on a dielectric substrate and fed by a 50 Ω microstrip line, a rectangular patch antenna with 3 stubs is demonstrated to generate two separate resonant modes to cover 2.4/5.2/5.8 GHz (wireless local area network) WLAN bands with satisfactory radiation properties. The impedance bandwidth of the proposed antenna is 400 MHz at 2.4 GHz band (2250–2650 MHz, 16.3%) and 920 MHz at 5 GHz band (4990–5910 MHz, 16.9%). The performances of this antenna are highly desirable for 2.4 and 5 GHz dual-band WLAN applications. The parameters which affect the performance of the antenna in terms of its frequency domain characteristics are investigated in this paper.