Shun-Shi Zhong

Compact Elliptical Monopole Antenna With Impedance Bandwidth in Excess of 21:1

A compact CPW-fed monopole antenna composed of an elliptical monopole patch and a coplanar trapeziform ground plane is introduced. The simulated and experimental results demonstrate that this antenna achieves a ratio impedance bandwidth of 21.6:1 for VSWR les 2, and exhibits a nearly omnidirectional radiation pattern, while its area is only about 0.19 lambda1 times 0.16 lambda1 where lambda1 is the wavelength of the lowest operating frequency. By comparing with various designs, it is shown that its bandwidth broadening comes from three factors: the optimum elliptical monopole shape, a trapeziform ground plane and a tapered CPW feeder.

A Printed Elliptical Monopole Antenna With Modified Feeding Structure for Bandwidth Enhancement

A printed extremely wideband antenna is studied and results presented. The proposed antenna is composed of a trapezoid ground plane and an elliptical monopole patch which is fed by a modified tapered CPW line. The simulated and measured results agree well and it indicates the antenna has a measured impedance bandwidth from 1.02 GHz to 24.1 GHz with a VSWR ≤ 2. It is shown that the antenna radiation pattern is nearly omni-directional over the entire frequency band and the antenna is suitable for wireless communication applications.

A broadband slotted ridge waveguide antenna array

A longitudinally-slotted ridge waveguide antenna array with a compact transverse dimension is presented. To broaden the bandwidth of the array, it is separated into two subarrays fed by a novel compact convex waveguide divider. A 16-element uniform linear array at X-band was fabricated and measured to verify the validity of the design. The measured bandwidth of S11les-15 dB is 14.9% and the measured cross- polarization level is less than -36 dB over the entire bandwidth. This array can be combined with the edge-slotted waveguide array to build a two-dimensional dual-polarization antenna array for the synthetic aperture radar (SAR) application

Corner-fed microstrip antenna element and arrays for dual-polarization operation

A systematic study on the dual-polarized corner-fed microstrip antenna element and arrays with thin single-layer structure is presented. The impedance matrices and S-parameters of the element and arrays are investigated by the proposed extended multiport network method (EMNM). The co- and cross-polarization patterns are also analyzed. It is shown that this kind of antenna element has an isolation about 10 dB higher than that of a conventional edge-fed square patch. A series of new dual-polarized arrays of corner-fed patches have been designed and analyzed based on the EMNM. The experimental results of five arrays indicate that these arrays achieve an isolation of 27/spl sim/38 dB with a maximum of higher than 28/spl sim/58 dB and cross-polarization level of lower than -23/spl sim/ -30 at boresight, which are substantially better than those of similar dual-polarized arrays of edge-fed patches. All theoretical results are in good agreement with experimental ones.

Study of an Extremely Wideband Monopole Antenna with Triple Band-Notched Charactersistics

Three notched bands are generated, at selected frequen- cies, in an extremely wideband base antenna to support multiple com- munication systems while avoiding inference from other existing nar- rowband systems. The design of a fully printed extremely wideband antenna and creating triple band-notched functions are addressed in this paper. Measurements demonstrate that the proposed printed base antenna has an extremely wide 2:1 VSWR bandwidth from 0.72GHz, to 25GHz with a ratio bandwidth of 34:1. The antenna has a simple structure and can be fabricated at low cost for multi-band and wide- band wireless communication devices. Besides, this paper presents a technique to form three notched bands within the operating frequency range of the base antenna. By introducing a half-wavelength U-shaped defected ground structure (DGS) and a pair of quarter-wavelength open arc-shaped slots to the radiating patch, three notched bands are created to prevent interference from WLAN (2.4{2.484GHz and 5.15{ 5.85GHz) systems and downlinks of X-band satellite communication (7.25{7.75GHz) systems.

Waveguide slotted antenna array with broadband, dual-polarization and low cross-polarization for X-band SAR applications

A broadband dual-polarization slotted waveguide planar antenna array for X-band SAR application is presented. The vertical polarization (VP) is realized with a ridged-waveguide longitudinal slot linear antenna array, while the horizontal polarization (HP) is realized with an untilted narrow-wall slot linear array. The basic part of the array is a subarray comprising an HP and a VP slotted waveguide single-polarization linear array. Each single-polarization linear array with 16 uniformly radiating elements is divided into four groups and fed by a 4-way waveguide power divider to broaden the bandwidth. The ridged slotted waveguide linear array for the VP is fed by a novel waveguide power divider which adapts to the compact width of the radiating guide. An untitled narrow-wall slot waveguide (half height) linear array excited by shaped irises for the HP, which can achieve very low cross polarization, is used. The benefits of this dual-polarization waveguide array, particularly when compared to microstrip arrays, are very low loss and good cross-polarization suppression. A panel of 16/spl times/16 dual-polarized waveguide slotted antenna array is designed, fabricated and measured. The measured results show a good agreement with the calculated ones, verifying the design. With the active transmit/receive module used, an active phased array antennas consisting of several hundreds of dual polarized subarrays can be carried out.

Tri-Band Dual-Polarization Shared-Aperture Microstrip Array for SAR Applications

The design of a tri-band dual-polarization (TBDP) shared-aperture microstrip array antenna for synthetic aperture radar (SAR) applications is presented. It operates at L-, Sand X-bands with a frequency ratio of 1:2.8:8. This TBDP shared-aperture array is assembled by two L/S and L/X DBDP shared-aperture sub-arrays with one L-band dual-polarized sub-array. A prototype array has been fabricated and measured, which exhibits wide impedance bandwidth (VSWR ≤ 2) of 13.4%, 14.8%, and 16.8% in L-, S-, and X-bands, respectively. The measured array isolation is better than -27 dB in all three bands. The measured radiation patterns agree well with the simulation, confirming the cross-polarization level of below dB within the main lobe region, and the array scanning capability of ±27° in S- and X-bands. This array design approach can be further extended to shared-aperture arrays with more than three bands.

Compact dual-frequency microstrip antenna

A new type of compact dual-frequency microstrip antenna is presented, which is designed by utilizing a cross-slot and two shorting-pins. Comparing with the conventional rectangular patch antenna, the bandwidths for dual-frequency are both extended to more than 3.8 times and the spacing between the feed and shorting-pin position is larger and easier for manufacturing. The finite-difference time-domain (FDTD) method is used to calculate the return loss and input impedance properties.

Polarization-agile microstrip antenna array using a single phase-shift circuit

A novel polarization-agile microstrip antenna array is proposed, in which the polarization agility from linear to circular polarization for the whole array is realized easily by controlling a single phase-shift circuit. Using the corner-fed square patch element, a new 16 element dual-polarized array with high isolation and low cross-polarization is designed and analyzed by the extended multiport network method. A special FET phase shifter circuit is created, where 0/spl deg/ or 90/spl deg/ phase shift between dual ports is electrically switched. Experimental results are presented to verify the theory, and measured circularly-polarized radiation patterns show a boresight axial ratio of 0.5 dB. Another experiment that connects a low noise amplifier together with the phase-shift circuit is also introduced, realizing both polarization agility and power amplification with one active circuit.

Effects of Printed UWB Antenna Miniaturization on Pulse Fidelity and Pattern Stability

A printed full-size UWB antenna and its two miniaturized configurations are presented. By modifying the monopole and the ground plane, 49% and 77% reductions in antenna area are realized, respectively. An investigation is carried out to examine the effect of antenna miniaturization on pulse fidelity and pattern stability. The far-field electric field waveforms and frequency-domain correlation patterns of the three antennas are presented and compared. The results indicate that the pulse fidelity factor (PFF) and pattern stability factor (PSF) have been improved by the proper miniaturization procedure. It is demonstrated that the improvements of the fidelity factor is 21% in the azimuth plane and 4% in the elevation plane. Moreover, the compact antenna also demonstrates 6.7% and 1.1% enhancement of PSF in the azimuth and elevation planes, respectively. Furthermore, the reduction in antenna size does not cause noticeable negative effects on impedance matching.