g-Zeng Yin

DESIGN OF NARROW BAND-PASS FREQUENCY SELECTIVE SURFACES FOR MILLIMETER WAVE APPLICATIONS

A design methodology of narrow band-pass frequency selective surfaces (FSSs) using the Fabry-Perot approach is presented. The whole FSS structure consists of two identical single layer FSSs separated by a foam layer, which forms a Fabry-Perot interferometer (FPI). The band-pass characteristic is a result of the FPI. The pass band can be controlled by the thickness of the foam, and the bandwidth can be controlled by the re∞ection coe-cients of the single layer FSSs. The efiects of both metallic and dielectric losses are discussed. It is interesting to note that the transmission peaks of FPI with high Q factor decline rapidly and flnally disappear as the losses increase, and the insertion loss is mainly due to the refection. The relationship between the insertion loss and the Q factor of the FPI is examined. As examples, narrow band-pass FSSs at about 96GHz with difierent bandwidths are designed.

A WIDEBAND MONOPOLE WITH G TYPE STRUCTURE

In this paper,a new monopole with G type structure is proposed,consisting of two wires rectangle rings with radius of 2 mm. The software Numerical Electromagnetic Code (NEC) is used to analyze the proposed antenna and a prototype is designed. The experimental and numerical results of the designed wideband antenna are presented and analyzed,and a 510 MHz bandwidth from 0.86 GHz to 1.37 GHz is demonstrated. The experimental and numerical results fit well.

FREQUENCY SELECTIVE SURFACES WITH FRACTAL FOUR LEGGED ELEMENTS

Frequency selective surfaces (FSSs) with fractal four legged aperture elements are studied. Three different order fractal elements are discussed for comparison. The results show that by using this novel kind of elements, multiband FSSs with miniaturized elements can be achieved. The ratio of the first resonant wavelength to the periodicity can be up to 10.36. Four passbands for normal incidence or two stable passbands for different incident angle and polarizations can be obtained. The FSS is analyzed by the spectral domain approach.

MULTIFUNCTIONAL MEANDER LINE POLARIZER

A multifunctional meander line polarizer is described. The polarizer is capable of effecting conversions between linear and circular polarization and between left-hand and right-hand circular polarization. It can also cause arbitrary rotation of linear polarization, including converting a wave from horizontal polarization to vertical. The polarizer is analyzed by the spectral domain approach.

A New Ultra-Wideband Microstrip-Line Fed Antenna with 3.5/5.5ghz Dual Band-Notch Function

A novel and compact planar ultra-wideband wide-slot antenna with dual band-notched function is proposed. The method of creating dual band-notch function is unique from traditional ones. By embedding a U-shaped parasitic strip and a pair of T-shaped stubs in the wide slot, dual bandstops around 3.5GHz and 5.5GHz can be obtained. The measured results demonstrate that the proposed antenna, with a compact dimension of 20 × 32.5mm, has a large bandwidth over the frequency band from 2.5 to 11.7GHz with voltage standing wave ratio (VSWR) less than 2, except the bandwidths of 3.3 ∼ 3.7GHz for WIMAX and 5 ∼ 6GHz for WLAN. In addition, the radiation pattern has an excellent omni-directional characteristic in H-plane and a typical monopole-like pattern in E-plane.

A Novel RX-TX Front-Ends for Passive RFID Reader with High Isolation

In passive radio frequency identification (RFID) system, the isolation between transmitter and receiver has been a critical problem because the TX and RX are simultaneous. A directional coupler has been used to isolate RX from TX, whereas some latent disadvantage of insertion loss of receiver signal and poor isolation have already emerged from conventional microstrip directional coupler because of low coupling and unequal phase velocity between even and odd mode. In this paper, a new RX-TX Front-Ends based on a 3dB branch-line coupler is proposed to reduce the insertion loss of the received signal and improve the isolation by Reflected Power Canceller (RPC) between TX and RX. The results of the proposed method show that the insertion loss of received signal is about 3dB and the transmit/receive isolation is more than 46dB in the UHF RFID frequency band.

Wideband printed dipole antenna for wireless LAN

A wideband printed dipole antenna array is proposed for WLAN and Bluetooth applications. The proposed antenna array, consisting of two printed-strip dipoles, the arms of which are printed on opposite side of an electrically thin dielectric substrate and connected through a parallel strip-line, is presented. The printed strip dipole antenna element is simulated by Ansoft HFSS 8.0. Several prototype antennas are designed and fabricated. Broadband antennas with bandwidth greater than 12% for VSWR /spl les/1.5 operating near 3.5GHz are obtained. This antenna is a good candidate for operation at 2.4GHz, 3.5GHz, or 5.8GHz. The important advantages of these antennas are simplicity in structure, low cost, and ease of manufacture and production largely as printed circuits.

A circular slot antenna with a pair of embedded L-strips for WLAN applications

A novel circular slot antenna is proposed for wireless local area network (WLAN) applications. By applying a monopole on the opposite side of the circular slot etched on the ground plane, a resonant frequency band is excited at about 2.4 GHz, with impedance bandwidth (return loss > 10 dB) from about 2.3 to 2.8 GHz, which covers WLAN 2.4 GHz and worldwide interoperability for microwave access (WiMAX) 2.5 GHz operating bands well. Then a pair of symmetrical L-strips are embedded into the slot to generate another resonant band from about 4.9 to 6.0 GHz, achieving a coverage of WLAN 5.2/5.8 GHz and 5.5 GHz WiMAX bands. The prototype of the proposed antenna has been successfully constructed and tested. Good characteristics of radiation have been also obtained.

A Dipole-disk Antenna with Equal Beamwidths

A novel method of radiation pattern shaped of dipole-disk antenna by adding a hemisphere conductor is proposed in this paper. The improved dipole-disk antenna has identical beamwidths in E- and H-plane, while its profile does not increase. A model of this antenna is built, stimulated and optimized by a commercial software Ansoft HFSS. Numerical analysis based on stimulation results is made and the design principles involved are described.

Self-structuring Antenna with Fractal Structure

In this paper, a self-structuring antenna (SSA) with fractal structure is proposed to achieve multi-frequency bandwidth. The proposed antenna is comprised of triangle rings in which wire segments are interconnected by controllable switches. The antenna can be reconfigured to meet different goals by changing the switches states that are open or closed. The SSA with fractal structure is simulated by numerical electromagnetic code (NEC), and numerical results are presented and shown that the proposed antenna has a VSWR bandwidth of 460 MHz to 690 MHz with VSWR less than 1. 7.