Shiqiang Fu

Single-Fed Broadband Circularly Polarized Stacked Patch Antenna With Horizontally Meandered Strip for Universal UHF RFID Applications

In this paper, a horizontally meandered strip (HMS) feed technique is proposed to achieve good impedance matching and symmetrical broadside radiation patterns for a single-fed broadband circularly polarized stacked patch antenna, which is suitable for universal ultrahigh frequency (UHF) RF identification (RFID) applications. The antenna is composed of two corner truncated patches and an HMS, all of which are printed on the upper side of the FR4 substrates. One end of the HMS is connected to the main patch by a probe, while the other end is connected to an SMA connector. Simulation results are compared with the measurements, and a good agreement is obtained. The measurements show that the antenna has an impedance bandwidth (VSWR <; 1.5) of about 25.8% (758-983 MHz), a 3-dB axial ratio (AR) bandwidth of about 13.5% (838-959 MHz), and a gain level of about 8.6 dBic or larger within the 3-dB AR bandwidth. Therefore, the proposed antenna can be a good candidate for universal UHF RFID readers operating at the UHF band of 840-955 MHz. In addition, a parametric study and a design guideline of the proposed antenna are presented to provide the engineers with information for designing, modifying, and optimizing such an antenna. At last, the proposed antenna is validated in RFID system applications.

Dual-Band Probe-Fed Stacked Patch Antenna for GNSS Applications

A novel proximity-coupled probe-fed stacked patch antenna is proposed for Global Navigation Satellite Systems (GNSS) applications. The antenna has been designed to operate for the satellite navigation frequencies in L-band including GPS, GLONASS, Galileo, and Compass (1164-1239 MHz and 1559-1610 MHz). A key feature of our design is the proximity-coupled probe feeds to increase impedance bandwidth and the integrated 90deg broadband balun to improve polarization purity. The final antenna exhibits broad pattern coverage, high gain at the low angles (more than -5 dBi), and VSWR <1.5 for all the operating bands. The design procedures and employed tuning techniques to achieve the desired performance are presented.

Broadband Circularly Polarized Slot Antenna Array Fed by Asymmetric CPW for L-Band Applications

A novel broadband circularly polarized (CP) slot antenna array fed by asymmetric coplanar waveguide (CPW) with an inverted L-shaped strip for L-band applications is proposed. Broadband CP is obtained by an array composed of elliptically polarized elements using sequential rotation feed technique. Experimental results show that the VSWR les 1.5 impedance bandwidth and the 3-dB axial ratio bandwidth can be greatly raised to be as high as 52% (1.151.95 GHz) and 49% (1.151.9 GHz), respectively. The proposed antenna can provide a peak antenna gain of about 8 dBi at 1.5 GHz, with gain variations less than 1.5 dB for frequencies within the CP bandwidth. Good agreement is observed between simulation and measurement.

Broadband Circularly Polarized Microstrip Antenna with Coplanar Parasitic Ring Slot Patch for L-Band Satellite System Application

A novel capacitive-coupled probe-fed circularly polarized (CP) microstrip antenna with coplanar parasitic ring slot patch has been proposed for the International Maritime Satellite (INMARSAT) and the Global Positioning System (GPS) applications. The key feature of the design is employing capacitive-coupled four-probe feeds to increase impedance bandwidth and adopting coplanar parasitic ring slot patch to enhance CP bandwidth. The feed network is compact and neat using only T-junction power dividers and phase shifters with shunted short-circuited microstrip stubs for lightning protection. The characteristics of the proposed antenna have been studied by simulation and experiment. The final antenna can produce a S11 <; -14 dB impedance bandwidth of nearly 27%, a 3-dB axial-ratio bandwidth of nearly 16%, and a gain of higher than 8 dB in the whole maritime satellite communication work band.

An Inmarsat BGAN Terminal Patch Antenna Array With Unequal Input Impedance Elements and Conductor-Backed ACPW Series-Feed Network

A novel 2 × 2 sequentially rotated patch antenna array with unequal input impedance elements and a conductor-backed asymmetric coplanar waveguide (ACPW) series-feed network is proposed. The corner truncated patch element is fed by a three-dimensional meander strip, which can easily control the input impedance and has slight effects on the radiation performance. Compared to microstrip-line feed networks, the radiation loss of the proposed feed network is lower. Furthermore, the maximum characteristic impedance of transmission lines in the proposed feed network is 91.2 Ohm. As a result, it can be easily realized with printed circuit board (PCB) techniques. The measured results show that the proposed antenna array has an impedance bandwidth (VSWR <; 1.5) of about 40.5% (1244-1876 MHz), a 3-dB axial ratio (AR) bandwidth of about 25.6% (1412-1826 MHz), and a gain-level larger than 11.6 dBi across the broadband global area network (BGAN) operating bands. Therefore, the proposed antenna array can be a good candidate for Inmarsat BGAN portable terminal applications.

Wideband dual-layer patch antenna fed by a modified L-strip

A wideband patch antenna is proposed. By using the dual-layer patch configuration and modified L-strip feed technique, the impedance bandwidth of the patch antenna for VSWR<1.2 is broadened to 22% with respect to 900 MHz, which is superior to the other available patch antennas. In addition, by means of the modified L-shaped strip, the high cross polarization levels of the proposed antenna are suppressed effectively. Simulation results are compared with the measurements, and a good agreement is obtained. The measurements show that the antenna has a low cross-polarization level (<-20dB) and an acceptable gain level (~9dBi) across the operating bandwidth. At last, a parametric study and a design guideline of the proposed antenna are also presented to facilitate the design and optimization processes for engineers.

Single-fed single-patch broadband circularly polarized antenna for UHF RFID reader applications

A single-fed single-patch broadband circularly polarized (CP) antenna is proposed for radio frequency identification (RFID) reader operating at 865–928 MHz. The antenna comprises a novel probe-fed meandered strip and a corner truncated square patch. Broadband CP operation is achieved by selecting an optimal size of the truncated corners and using a thick air-layer substrate (about 0.12λ0). To obtain good impedance matching (VSWR<1.5) within the 3 dB axial ratio bandwidth, the probe-fed meandered strip feed technique is proposed and adopted. In addition, the commercial software called HFSS was also used to simulate the antenna performance. Simulation results show that the proposed antenna has an impedance bandwidth (VSWR<1.5) of about 74 MHz (858–932 MHz), a 3dB axial ratio bandwidth of about 71 MHz (860–931 MHz), and a gain level of 8.6 dBi or larger within the operating bandwidth.

Printed quadrifilar helix antenna with integrated feed network

A new printed quadrifilar helix antenna with integrated feed network was designed for satellite mobile communication systems. The input impedance of this antenna in each port is about 50Ω without a matching circuit. It makes the feed network simplified and miniaturized. Parameter tradeoffs have a direct bearing on antenna performance in antenna design. A trial and error approach to this problem is both costly and unreliable. The purpose of this work is to use computer electromagnetic simulation to predict antenna properties for optimum performance. The proposed antenna displays small size, light weight, low cost, large bandwidth, hemispherical radiation pattern and excellent circular polarization.

Circularly polarized antenna with U-shaped strip for RFID reader operating at 902–928 MHz

A circularly polarized patch antenna is proposed to operate at 902–928 MHz for Radio Frequency Identification (RFID) reader applications. The antenna is composed of a U-shaped strip and a square patch with truncated corners. By means of the U-shaped strip feed technique, the VSWR of the patch antenna is less than 1.2. In addition, the structure of the proposed antenna is simple and low-cost. Simulation results show that the proposed antenna has an impedance bandwidth (1.2:1 VSWR) of about 123 MHz (865–988 MHz), a 3dB axial ratio bandwidth of about 28 MHz (902–930 MHz), and a gain level of about 8.8 dBi.

Novel Coupled Line 180

This paper presents a novel coupled line 180° hybrid with non-interspersed input/output ports. With the combination of a weak coupling parallel coupled line and strong coupling trans-directional coupler, a non-interspersed input/output ports coupled line 180 ° hybrid is obtained by using printed circuit board fabrication process, and reduced substrate area is achieved. The proposed hybrid owns the features of reducing the complexity of dc biasing for the next-stage active circuits. Moreover, it requires no bond wires, via-holes, or multilayer structures. The formula of the proposed hybrid is derived, and the characteristics of the hybrid are analyzed. Two prototypes are designed to verify the concept. One is arranged with the two couplers perpendicular to each other, and the other is constructed with the two couplers arranged in a line. The measured results are in good agreement with the simulated ones.