Abstract-Research of antenna Radar Cross Section (RCS) is very important for low observable platform. Aperture coupled microstrip antenna is fit for the low RCS antenna design because the feed network produce less effect on scattering of microstrip patch. A novel aperture coupled microstrip antenna is proposed, which utilizes the chip-resistor load, ground slot and miniaturization, to realize RCS reduction. Aperture coupled antenna with rectangular patch is chosen as the reference antenna. Two antennas are simulated and measured. The measured results show that the designed antenna realizes only 0.5 dB gain loss while RCS are reduced in almost all the frequency band.
Abstract-A compact dual-band dual-polarized antenna is proposed in this paper. The two pair dipoles with strong end coupling are used for the lower frequency band, and cross-placed patch dipoles are used for the upper frequency band. The ends of the dipoles for lower frequency band are bent to increase the coupling between adjacent dipoles, which can benefit the compactness and bandwidth of the antenna. Breaches are introduced at the ends of the dipoles of the upper band, which also benefit the compactness and matching of the antenna. An antenna prototype was fabricated and measured. The measured results show that the antenna can cover from 790 MHz to 960 MHz (19.4%) for lower band and from 1710 MHz to 2170 MHz (23.7%) for upper band with VSWR < 1.5. It is expected to be a good candidate design for base station antennas.
Abstract-This paper presents the design of a novel wideband omnidirectional antenna with the usable bandwidth enhanced. The antenna is designed for wireless applications and proposed to operate within WLAN (2.4 GHz-2.484 GHz) and WiMAX (2.3 GHz, 2.5 GHz and 3.5 GHz) frequency bands. The bandwidth is enhanced through the use of balun, while the radiation patterns remain stable. This antenna has a much wider VSWR band (47.5% for VSWR < 2) with high radiation pattern stability compared with printed dipole antennas. Details of design, simulated and experimental results of this omnidirectional antenna are presented and discussed. The measured results confirm the validity of this design which meet the requirements of wireless applications.
Abstract-In this paper, a wideband differential phase shifter has been analyzed and designed using Genetic Algorithm (GA). The differential phase shifter consists of two fixed main lines of length λ/2, and parallel open and short stubs of length λ/8, which are shunted at the edge points of the main lines, respectively. With the application of GA, an impedance match and minimum phase deviation for the desired phase shift over a wide frequency band are obtained. In order to verify the optimum results, simulation experiments are made and a 45 • phase shifter is fabricated and measured. The phase shifter exhibits an impedance bandwidth (|S 11 | < −10 dB) and a consistent 45 • (±2 • ) phase difference bandwidth around 66%.
A novel printed top-loaded monopole antenna with a pair of sleeves on the ground plane for multiband wireless local area network (WLAN) applications is presented. This antenna is composed of a top-loaded monopole and two sleeves on a ground plane. Both the antenna and the ground plane are printed on the same side of an inexpensive FR4 substrate. This antenna has light weight and compact size of only 29 × 45 × 0.5 mm 3. The operation bandwidth of this proposed antenna covers 2.4 GHz/5.2 GHz/5.8 GHz WLAN bands and 7.4 GHz∼8.8 GHz for UWB application, which perfectly meet the requirement of multiband working. The measured and simulated results agree well with each other.
Abstract-An annular-ring element for building a miniaturized bandstop frequency selective surface (FSS) structure which possesses a superior performance with respect to electromagnetic wave polarizations and incident angles is introduced in this paper. The proposed element has prominent miniaturization characteristics with a unit dimension of 0.061λ × 0.061λ, where λ represents the freespace wavelength corresponding to resonant frequency. Miniaturization of the proposed FSS element is achieved by constructing special meandered strips in geometry and arranging lumped components between the elements. The advantage of this method lies in its great simplicity in tuning the resonant frequency of FSS by adjusting values of the printed capacitors rather than rebuilding the geometry. The obtained FSS also exhibits a stable performance in terms of angle stability and polarization insensitivity. Prototypes of the proposed FSS are fabricated and measured to verify design method. Measurements are well in line with simulation results.
Abstract-By combining a horizontal bowtie electric dipole and a vertical rhombic loop antenna which is realized by a pair of folded shorted patches, a very wideband dipole-loop composite patch antenna is designed. Four tuning stubs are attached to the edges of the bowtie dipole to improve the impedance matching. The bowtie dipole and the rhombic loop antenna are excited simultaneously by a simple feed structure which not only forms a folded balun but also makes the antenna itself be direct current grounded. Results show that a wide impedance bandwidth of 121.6% for |S 11 | < −10 dB from 3.5 to 14.35 GHz is obtained. Good radiation patterns, low back radiation, low cross polarization level, and peak antenna gains of 7.7 to 9.8 dBi are achieved over the operating bands.
Abstract-A composite wideband absorbing material (WAM) covering dual bands is designed, to reduce the in-band radar cross section (RCS) for broadband antenna in this paper. The upper layer is a traditional absorber while the lower one is a dual-band frequency selective surface (FSS), which is formed by a square ring and an improved Jerusalem cross structure. The absorbing band has been broadened to 112% compared with the magnetic sheet without FSS. Over C and X bands, the absorption rate is over 90%. By using the FSS-based WAM as the ground plane of a Vivaldi antenna, substantial RCS reduction is obtained from 2-18 GHz. Moreover, the RCS is reduced remarkably over −80 • -80 • incident angles except for minority angles, with the radiation performance preserved at the same time.The experimental results are in good agreement with the simulated ones.
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