Zijian Xing

Mutual Coupling Reduction by Novel Fractal Defected Ground Structure Bandgap Filter

This paper presents a novel fractal defected ground structure (FDGS) to reduce mutual coupling between coplanar spaced microstrip antenna elements. The structure of the proposed FDGS is studied. Bandgap characteristic of second and third iterative FDGS is achieved. The second and third iterative FDGSs are used to reduce mutual coupling between microstrip antenna elements. Mutual coupling reduction performance of third iterative FDGS is better than that of second iterative FDGS. And dimension of FDGS can be decreased by using higher level iterative FDGS. The third iterative FDGS is fabricated and measured. Simulated and measured results both show that more than 35-dB mutual coupling reduction is obtained by using the third iterative FDGS. Moreover, the envelope correlation of antenna elements with FDGS is quite smaller than that of antenna elements without FDGS.

Characteristics and Application of a Novel Loop Antenna to UHF RFID Receivers

A broadband two-layer and two quasihalf loops antenna (TTLA) at UHF is characterized and analyzed for ultrahigh frequency (UHF) near-field radiofrequency identification (RFID) applications. The antenna is investigated in terms of impedance matching and distribution of magnetic field as well as applied in two scenarios which are the experiments of interrogation range and receiver circuit of RFID systems.

A New Technique to Design Circularly Polarized Microstrip Antenna by Fractal Defected Ground Structure

A new technique to design single-feed circularly polarized (CP) microstrip antenna is proposed. The CP radiation is obtained by adjusting the dimension of the etched fractal defected ground structure (FDGS) in the ground plane. Parameter studies of the FDGS are given to illustrate the way to achieve CP radiation. The CP microstrip antennas with the second and third iterative FDGS are fabricated and measured. The measured 10-dB return-loss bandwidth of the CP microstrip antenna is about 30 MHz (1.558 to 1.588 GHz), while its 3-dB axial-ratio bandwidth is 6 MHz (1.572 to 1.578 GHz). The gain across the CP band is between 1.7 and 2.2 dBic.

Study of Multi-Band Circularly Polarized Microstrip Antenna with Compact Size

In some satellite navigation receiver systems, there is not enough space to settle several antennas for multi-port multi-band application generally. A triple-deck circularly polarized antenna with three ports for receiving and sending satellites signal is studied in this paper. The design idea in this paper is to place several single-feed microstrip antennas layer by layer for saving space. All patch antennas are probe-fed, and the probe connected with the upper patch goes through the clear hole in lower substrates. The structure of the multi-band antenna is investigated thoroughly. How to tune this kind of antenna is a big problem in application, and one special parameter is given to adjust the performance of the antenna. The designed triple-deck antenna works at the bands of GPS, BDS and 1.66 GHz independently. The formal two bands are RHCP, and the third band is LHCP, so it can receive and send signals at the same time. Both simulated and measured results show that all three working bands can cover the system use differently. Axial ratio less than 3 dB at center frequency is obtained, and absolute gain at center frequency is more than 4 dBic. The advantages of this antenna are compact in size for multi-port multi-band use and easy fabrication.

Mutual coupling reduction of microstrip antenna array by periodic defected ground structures

A periodic defected ground structure (DGS) was proposed to reduce mutual coupling between antenna elements in coplanar linear polarization microstrip antenna array. The defected ground structure is three U-shaped elements etched off from ground plane periodically between microstrip antenna elements. Coupled polarization is rotated 90deg by the proposed periodic DGS, 10dB mutual coupling reduction between microstrip antenna elements is achieved and barely influence on microstrip antenna far-filed main radiation properties.

Study of novel antenna radome for circular polarizer and director

Abstract This study presents the use of contiguous rectangle-patches radome as a method of generating circularly polarized signals from linearly polarized antenna or antenna array that are covered by the structure. Experiment results of the novel structure with 2 × 2 antenna array are demonstrated for L-band operation. It is shown that left hand circular polarization of antenna array can be achieved with appropriate parameters design of radome. In addition, the structure is also built as a director that can greatly improve the gain of the antenna.

Study on Horizontally Polarized Omnidirectional Microstrip Antenna

A horizontally polarized omnidirectional microstrip antenna is proposed in this paper. The structure of designed antenna is with two back-to-back horizontally polarized microstrip antenna elements. Gain variation on main radiation plane of this new antenna is analyzed and radiation theory is deduced; formula of directivity on main radiation plane is given. Better omnidirectional characteristic of this antenna can be obtained by decreasing patch physical length. Both simulated and measured results verify the omnidirectional radiation patterns and input impedance characteristics. Good omnidirectional radiation patterns (gain variation in -plane less than ±0.4 dBi) and input impedance characteristics are obtained; moreover, cross polarization less than −20 dBi is achieved.

A novel circular polarization antenna radome

This study presents the use of contiguous aperture radome as a method of generating circularly polarized signals from linear polarization antenna or antenna arrays which are covered by the structure. The experiment results of the novel structure with microstrip antenna are demonstrated for L-band operation. In addition, the structure is also built as a director which can greatly improve the directivity of the antenna.

One terminal improving method of open-circuit near-field antenna of UHF RFID system

A novel broadband dual-loop antenna is presented for the ultra high frequency (UHF) near-field radio frequency identification (RFID) applications. Owing to the novel structure, the current distribution along the loop is kept in phase, as well as the metal terminals exert less influence on the z-orientation magnetic field. The antenna with novel terminals is described and the principle of operation is explained. A comprehensive parametric study of the new model is carried out and the results are presented and discussed in detail. To prove the novel structure, a prototype is developed and fabricated. The measurement results demonstrate that the antenna could achieve a broad bandwidth and low gain, and produce a strong magnetic field with a relatively small z-orientation magnetic field empty hole in the near field. Hence, the work is very promising for UHF near-field RFID reader applications.

Fast Carrier Cancellation for UHF Near Field RFID Systems

Abstract A novel carrier cancelation circuit is presented for ultra high frequency (UHF) near field radio frequency identification applications.A directional coupler, logarithmic detector and controlling circuit are used for improving the sensitivity of the receiver. The cancelation circuit, which consists of vector multiplier and SCM (Single Chip Micyoco), can be adaptively tuned to generate an optimum canceling signal for carrier cancelation. In order to secure good and fast carrier cancelation, logarithmic detector is used as a feedback component to transmit power information of the tag signal channel. The implemented reconfigurable carrier cancelation exhibits good performance on reduction of carrier level in tag signal channel when the adaptive control voltage of SCM is applied. Furthermore, the carrier cancelation control system could be operated real time as well as applied for hopping-frequency systems.