Y.-C. Jiao

Dual circularly polarized antenna of compact structure for rfid application

A compact structure is proposed to realize dual circularly polarized antenna for RFID system. In this paper, a cross-shaped aperture in the ground plane provides coupling between the patch and a single microstrip line with two ports underneath the ground plane, the means of feeding is constructed. For system requirements, some modifications are made to improve the performance. This design realizes low profile, separating the radiating patch and the feeding layer, particularly saving space by avoiding the traditional scheme based on microstrip branch line coupler. In the wireless communication system for RFID applications, circular polarization modulation (CPM) is implemented, which reduces the requirement for bandwidth effectively, and simplifies the data communication. Therefore, a dual circularly polarized antenna is an indispensable key part of this RFID system, and in some case the compact structure is necessary. In this design process, the dimensions and performance of this antenna are calculated and optimized by HFSS (High Frequency Structure Simulator). The results agree well with the measurement, and show the practicability of this scheme.

A Reconfigurable Microstrip Antenna with Switchable Polarization

A novel reconfigurable small microstrip antenna with switchable slots is proposed to achieve circular polarization diversity. Slots are cutting in the square patch and, by using the diodes to adjust the lengths of the slots, this antenna can radiate with either right hand circular polarization (RHCP) or left hand circular polarization (LHCP) using the same feeding probe. Simulation and experimental results are presented and it is demonstrated that this design is valid. The proposed antenna demonstrates useful features for wireless communication applications.

A Miniaturized Broadband 4 : 1 Unequal Wilkinson Power Divider

This paper presents the design of a miniaturized unequal 4 : 1 Wilkinson power divider operated across a broadband 1 to 11 GHz, which has a compact size with overall dimensions only of 10 mm × 26 mm. By using a simple defected ground structure (DGS), the microstrip line can be realized with very high impedance of over 150Ω, and consequently a 4 : 1 power dividing ratio can be obtained. Meanwhile, the fabrication problems caused by the very thin conductor microstrip width can be prevented. For verification, the measured results of good dividing ratio, better than 10 dB return loss and better than 15 dB isolation across the whole operating band, are also given.

Modified Particle Swarm Optimization for Patch Antenna Design Based on IE3D

An evolutionary optimization method for patch antenna designs is presented in this paper. The modified particle swarm optimization (MPSO) based on fitness distance ratio (FDR) is combined with standard software IE3D to achieve the optimum antenna satisfying a certain design criterion. The antenna geometric parameters are extracted and optimized by a MPSO program, and simulated by IE3D. The fitness function of the optimization is calculated by the MPSO program according to the simulation results extracted from IE3D to represent the performance of each candidate design. A microstrip line fed low-profile E-shaped patch antenna is designed and optimized using the MPSO/IE3D method. The designed patch antenna is simulated, fabricated, and measured to validate the effectiveness of the MPSO/IE3D method.

Frequency Notched UWB Slot Antenna with a Fractal-Shaped Slot

A frequency notched ultra-wideband planar slot antenna is presented. By introducing a modified fractal-shaped slot to the patch, a notched band within a wide operation bandwidth is achieved. The designed antenna satisfies the voltage standing wave ratio requirement of less than 2.0 in the frequency band from 3.01 to 13 GHz above while showing the band rejection performance about 500 MHz in the frequency band of 5.59 to 6.09 GHz. Simulation and measurement results are presented for the proposed antenna.

Pattern Synthesis of Concentric Ring Array Antennas by Differential Evolution Algorithm

In this paper, we propose a computational global optimization method based on differential evolution (DE) algorithm for synthesizing large multiple concentric rings arrays to generate a pencil beam with minimum peak side lobe level (PSLL) and constrained first null beam width (FNBW). The synthesis is performed with a differential evolution technique to optimize the ring spacing, the number of the elements in each ring as well as the amplitude distribution. Simulated results of the designed synthesis illustrate the efficiency and reliability of our proposed method.

A Microstrip-Fed Logarithmically Tapered Slot Antenna for Wideband Applications

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.

A Novel Compact UWB Antenna with Dual Band-Notched Characteristics

The design and analysis of a novel hut-shaped UWB antenna with dual band-notched characteristics are presented in this paper. By embedding two different resonating structures (spade-shaped slot and a pair of hook slots) in the reference UWB antenna, dual notched frequency bands are achieved. The measured impedance bandwidth defined by VSWR < 2 of 8.2 GHz (2.8–11 GHz), with the dual notched bands of 3.3–3.7 GHz and 5.0–6.0 GHz, is obtained. The proposed antenna with an overall dimension of only 24 × 32 mm2 is successfully simulated, designed and measured, showing broadband matched impedance and stable radiation patterns. The conceptual equivalent circuit models, which are based on the surface current distributions on the resonating structures, are also shown to further analyze the band-notched characteristics.

A novel small CPW-fed T-shaped antenna for MIMO system applications

A novel small CPW-fed T-shaped antenna for MIMO application is presented. The size of the antenna is only 35% of that of conventional CPW-fed T-shaped antenna, which has satisfied return loss bandwidth and omnidirectional radiation characteristics. A multifeed 8-element planar array is fabricated and measured. It shows that the features of small size, uniplanar structure, good radiation characteristics and small mutual coupling are promising for MIMO applications in compact portable devices.

Compact Dual-Band Circularly Polarized Monopole Antenna

A novel monopole antenna with dual-band circular polarization for the reception of WiMAX and WLAN is presented in this article. The radiating patch of the proposed antenna consists of a square loop surrounded by a concentric open rectangular loop, which is fed by a 50-Ω microstrip transmission line. The measured 3-dB axial ratio (AR) bandwidths are about 0.52 GHz from 3.23 to 3.75 GHz approximately 15.6% with respect to the center frequency at 3.34 GHz and 0.54 GHz from 4.98 to 5.52 GHz approximately 10.3% with respect to the center frequency at 5.23 GHz. The radiation characteristics of the implemented antenna are also presented.