Shuxi Gong

Circularly Polarized Stacked Annular-Ring Microstrip Antenna With Integrated Feeding Network for UHF RFID Readers

A novel circularly polarized (CP) annular-ring microstrip antenna (ARMSA) is proposed for American ultrahigh frequency (UHF) radio frequency identification (RFID) readers. The annular ring is fed by an equal-split power divider with 90° phase difference. For the compactness of the entire antenna, the divider with the shape of Archimedes gradual-change lines is designed at the inside of the annular ring. A circular parasitic patch is suspended above the ring to improve the impedance matching and bandwidth. It also enhances the performances of axial ratio (AR). The impedance bandwidth for S11 <; -10 dB and 3-dB AR bandwidth are 870-967 MHz (10.6% at 915 MHz) and 893-948 MHz (6%), respectively. The CP gain is 8.9 dBi at 915 MHz with the front-to-back ratio (F/B) of 16.5 dB. The proposed antenna is low profile as the total height is 0.043 λ0 (λ0 is the free-space wavelength).

Wideband RCS Reduction of a Slot Array Antenna Using Polarization Conversion Metasurfaces

A new approach to reducing the monostatic radar cross section (RCS) and preserving the radiation characteristics of a slot array antenna by employing polarization conversion metasurfaces (PCMs) is presented in this communication. The PCM is arranged in a chessboard configuration consisting of fishbone-shaped element. It is placed on the surface of the slot array antenna. The characteristics and mechanism of the RCS reduction are analyzed. Simulated and experimental results show that the monostatic RCS reduction band of the antenna with PCM ranges between 6.0 and 18.0 GHz for normally impinging both x- and y-polarized waves. The radiation characteristics of the antenna are well preserved simultaneously in terms of the impedance bandwidth, radiation patterns, and realized boresight gains.

Low RCS Dipole Array Synthesis Based on MoM-PSO Hybrid Algorithm

In this paper, a hybrid algorithm combined method of moments (MoM) with particle swarm optimization (PSO) is used to realize low radar cross section (RCS) array synthesis. Both the scattering factor and the radiation factor are involved in the proposed objective function to achieve the promising dipole array with a reduced RCS and satisfied radiation performance. To improve the optimization efficiency, radiation constraint conditions are adopted to avoid unnecessary scattering calculation. The symmetric matrix and block treatment are also used to fill the MoM impedance matrix. The optimization results show that the proposed algorithm is able to achieve RCS reduction of 5.5 dB for dipole array.

Dual-Band and Wideband Design of a Printed Dipole Antenna Integrated with Dual-Band Balun

A dual-band printed dipole antenna with integrated balun feed is given in this paper. First, the fork-shaped slot is etched on the arms of the printed dipole antenna to achieve the dual-band operation with resonances at WLAN bands. The radiating element without balun is optimized and operates at 2.4 GHz (2180–2750MHz) and 5.2GHz (5040 MHz–5480MHz) where return loss is less than −10 dB. In order to get a larger bandwidth, a modified Marchand balun is introduced for dual-band operation, which can provide two resonances in each band to enhance impedance bandwidth. By co-designing the radiating element with the dual-band balun, an antenna covering 2150–2750 MHz and 5050–6230 MHz bands has been achieved. The design equations for modified balun have been presented and agreement between calculation and measurement is good.

A Novel Miniaturized Broadband Dual-Polarized Dipole Antenna for Base Station

A novel dual-polarized dipole antenna for base-station applications is presented in this letter. The proposed antenna is composed of a cross dipole, a square loop, a square plate, and a small-size reflector. The square loop and the square plate act as a parasitic radiator and a director, respectively. By introducing the two parts, the impedance bandwidth of the cross dipole can be significantly enhanced, and broadside radiation patterns with narrow beam can be also obtained. Experimental results show that the proposed antenna can operate from 1.71 to 2.69 GHz with low VSWRs at the two ports. High isolation ( > 22 dB) and stable antenna gain (~ 8 dB) are also achieved over the entire operating frequency band. The antenna has symmetrical radiation patterns both in vertical and horizontal planes, and the half-power beamwidth is 70°±5°. Furthermore, the size of the proposed antenna is very compact, which is only 0.513 λ0 ×0.513 λ0 ×0.388 λ0 at the center of the operating frequency band.

Differential Evolution Algorithm and Method of Moments for the Design of Low-RCS Antenna

This letter introduces a novel technique for low radar cross section (RCS) antenna designs. The differential evolution algorithm (DEA) and the method of moments (MoM) are combined to achieve the RCS reduction and satisfied radiation performance. The antenna geometric parameters are extracted to be optimized by DEA, and a fitness function is evaluated by MoM to represent the performance of each candidate design. The optimization example of the slot patch antenna is presented as a test of the proposed DEA/MoM algorithm. By optimizing the slot location, the given slot antenna realizes the RCS reduction in the broad frequency range of 2-12 GHz at different incident angles, which demonstrates the feasibility of applying the proposed method to antenna RCS reduction.

Multiband Metamaterial-Loaded Monopole Antenna for WLAN/WiMAX Applications

A simple multiband metamaterial-loaded monopole antenna suitable for wireless local area network (WLAN) and Worldwide Interoperability for Microwave Access (WiMAX) applications is proposed in this letter. The rectangle monopole of the proposed antenna is originally designed to resonate at around 5.2 GHz. When the inverted-L slot is etched, the antenna produces a second resonance at around 4.1 GHz. Then, with the addition of the metamaterial reactive loading, the resonant frequency of the antenna will be shifted down, and a third resonance covering the 2.4-GHz band occurs. Consequently, the antenna can cover the 2.4/5.2/5.8-GHz WLAN and 2.5/3.5/5.5-GHz WiMAX bands with a very compact size of only 12.9 ×6.5 mm2. Monopole-like radiation patterns and acceptable gains and efficiencies have been obtained. Details of the antenna design as well as the experimental results are presented and discussed.

BIDIRECTIONAL HIGH GAIN ANTENNA FOR WLAN APPLICATIONS

Abstract—A bidirectional high gain four-element printed dipole array for WLAN (2.4/5.8GHz) applications is analyzed and successfully implemented in this paper. Each element used is a double-side printed dipole fed with a balance twin-lead transmission line. A wide-band balun is implemented for the dipole array. Both simulated and measured data are pretty matched. According to the measured results, the bandwidth with return loss less than −10 dB is about 280MHz (2250–2530MHz) and 510MHz (5470–5980MHz) in the two operating bands, the measured gain for 2.4GHz band is between 4.5 and 5.9 dB, and 6.1–8.9 dB for 5.8GHz respectively. Good shaped patterns have also been attained by tuning parameters of the dipole array.

A Novel Fractal Patch Antenna with Low RCS

The special space filling capability of Koch fractal is used in the Radar Cross Section (RCS) reduction of microstrip patch antenna. Compared with normal rectangular microstrip patch antenna, the resonance sides are designed in the shape of Koch fractal, while two Koch fractal shape slots are cut in the antenna. Based on the design, antenna prototypes were fabricated and tested, which shows that the gain loss was no larger than 1dB. The RCS of the fractal antenna is effectively reduced both in band and out of band compared with the rectangular patch antenna, while the radiation performance are almost maintained.

A Wideband Dual-Sleeve Monopole Antenna for Indoor Base Station Application

The design and enhanced bandwidth performance of a dual-sleeve monopole antenna for indoor base station application is presented. By a top-loading circular patch shorted to the ground plane through four shorting probes, the size reduction is achieved. The dual-sleeve structure is successfully employed to improve the impedance bandwidths through achieving another two resonant modes. A measured impedance bandwidth for VSWR ≤ 2 of about 137% ranging from 730 to 3880 MHz is achieved. It is very suitable for GSM900, DCS1800, PCS1900, UMTS, IMT2000, WiBro, WiMAX2350/3500, and wireless LAN (IEEE 802.11b).