Jian-Ying Li

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.

RECONFIGURABLE DUAL CIRCULARLY POLARIZED MICROSTRIP ANTENNA WITHOUT ORTHOGONAL FEEDING NETWORK

A polarization reconfigurable microstrip antenna is proposed without orthogonal feeding network. The antenna is composed of a suspended patch, two printed probes and a simple switch circuit. Reconfigurable circularly polarization, i.e., right-hand circular polarization (RHCP) or left-hand circular polarization (LHCP), is produced by controlling the states of the switch circuit. A prototype is designed and tested. The simulation and measurement results show that the proposed antenna demonstrates wide impedance bandwidth and a good axial ratio in the circularly polarized states.

Design of Wideband and Dual Polarized Cavity Antenna Planar Array

A 6 × 6 wideband antenna array with ±45° dual polarizations is proposed. To achieve good radiation efficiency, cavity antenna is used in this work as the basic element. Feeding probes and strip line feeding networks are printed on general PCB substrate. The feeding circuits for exciting different polarizations are stacked and multilayer substrate step structure is used. Here, strip line to downward SMA connector transitions is also designed, which aids in integrating the proposed array with T/R modules located below and extending it to larger phased array. The antenna array is fabricated and measured. Simulated and measured impedance and radiation performances are also given and compared. The proposed antenna arrays show wide bandwidth of 30% from 10.9 to 14.8 GHz, and isolation of higher than 33 dB is also exhibited across the bandwidth. Furthermore, symmetrical patterns and cross-polarizations of below -25 dB are also demonstrated.

A Wideband High-Gain Cavity-Backed Low-Profile Dipole Antenna

In this communication, a compact, wideband, low-profile, and high gain dipole antenna is proposed. A microstrip coupling line is used to feed the ellipse pairs, which is two arms of the antenna. This simple feeding structure can significantly enhance the impedance bandwidth (IBW). A cavity-backed structure is adopted to achieve the low-profile antenna. With the influence of the cavity-backed structure, the new antenna has a higher gain over the whole frequency band. An optimized antenna with a height of only 0.17λ (where λ is the free space wavelength at the lowest frequency) is designed and measured. The measured result shows that the IBW for VSWR <; 2 is 117% (2.48-9.51 GHz). Further, the gain bandwidth (Gain > 6 dBi) from 2.57 to 8.73 GHz is more than 108.9%. The antenna radiation pattern performs well over the whole band, and the peak gain can reach 11.8 dBi.

A Broadband Circular Polarizer Based on Cross-Shaped Composite Frequency Selective Surfaces

A cross-shaped composite with frequency selective surfaces is applied in the design of a broadband polarizer. The structure is multilayer, and the unit cell of each layer consists of a composite cross and a metal strip. The design takes advantage of both the similar amplitude and the stable phase difference of nearly 90° of the two orthogonal components of transmitted waves. The bandwidth of the polarizer reaches 74%, from 5.15 to 11.20 GHz, which is able to generate circular-polarization waves from incident linear waves. A sample polarizer is fabricated and tested. According to the measurement results, the polarizer operates from 5.75 to 11.20 GHz at normal incidence. In addition, its working frequency band can still cover the range of 5.80 to 11.00 GHz when the incident angle increases to 20°.

Broadband Circular Polarizer Based on Multilayer Gradual Frequency Selective Surfaces

This paper presents a broadband circular polarizer based on multilayer gradual frequency selective surfaces. The unit cell includes two identical circles and a bar, whose dimensions decrease layer by layer with a reduction factor. This design can provide a good phase difference that is close to 90°. The bandwidth of the polarizer reaches 66.7%, from 7.9 to 15.8 GHz, which can convert the incident linear polarization waves into circular polarization waves. A sample polarizer is fabricated and measured. The results show that the operation frequency ranges from 7.75 to 15.2 GHz, coinciding with the simulation. Meanwhile, the working frequency band covers the range of 8.2–14.5 GHz when the incident angle increases to 25°.

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 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.