A new indoor facility for electromagnetic tests is presented and used here for the specific case of bistatic radar cross section (RCS) measurements. A metallic cube is selected as test case and the results are compared with the predictions obtained with different numerical methods. Good agreement is reported.
A novel out-of-line series-fed patch array with low cross-polarization is presented in this paper. The element in the array is fed by a stub through one-port. The feeding stub is designed to be a novel curled-horn-shaped geometry, which can effectively suppress the cross-polarization due to its symmetry. The linear array consists of two identical subarrays which are located oppositely. By the antiphase feeding of two subarrays, the cross-polarization is further reduced. Furthermore, the theory analyses of the series-fed array indicate that it is competent for being applied to phased array systems. The simulated results show the cross-polarization levels of the linear array with 20 novel elements in E and H plane are lower than −30 dB and −60 dB, respectively. And, a prototype array is fabricated. Its low cross-polarization levels confirm the effective performance of the proposed design.
A novel microstrip dual-mode tri-band bandpass filter is presented. The filter consists of an open stub loaded dual-mode resonator and two short stub loaded dual-mode resonators. By utilizing the odd- and even-mode resonance properties of the proposed dual-mode resonators and the introduced source-load coupling (S-L coupling), the filter is designed with two transmission zeros at both sides of each passband, which will improve the selectivity of the filter. To validate the design theory, one 100 MHz 3 dB absolute equal bandwidths dual-mode tri-band filter with three passbands located at the centre frequencies of 1.8, 2.4 and 5.0 GHz, respectively, is designed and fabricated. Both experimental results agree well with the simulations.
A compact dual-band patch antenna is proposed and measured in this paper. The proposed antenna employs a U-shaped slot and two mitered corners to achieve two operating frequency bands, 2.30-2.50 GHz and 4.50-6.36 GHz, which meet the specifications of IEEE 802.11b/g/a standard for WLAN applications. Full wave analysis is performed to simulate the characteristics of the proposed antenna using CST microwave studio. Moreover, a fabricated prototype which has compact dimensions of 20.0 mm × 25 mm × 1 mm exhibits agreement between measured and simulated parameters and radiation patterns.
Electromagnetic properties of conventional radar absorbing materials (RAM) make it difficult to use them to provide remarkable surface electromagnetic waves (SEMW) attenuation with thin thickness at low radar frequencies such as in the UHF and L bands. In this paper, a composite structure realized by a grounded RAM slab covered by a resistive sheet is proposed. The use of a resistive sheet results in a significant increase of SEMW attenuation performance at low frequency, but almost no increase in its thickness. The electromagnetic scattering properties for a target coated with the RAM with/without covered by a resistive sheet are considered for interpreting the improvement of SEMW attenuation with resistive loading. Using a method-of-moments (MoM) computational scheme, we explore the performance of the proposed composite structure as radar backscattering suppression for a metal slab at low radar frequencies. It is found that the RAM with resistive loading has significantly increased SEMW attenuation at low frequencies, and advances the large incidence angle or grazing angle mono-static radar cross section (RCS) reduction of the coating slab further than the RAM without resistive loading case.
A compact ultra-wideband (UWB) slot antenna based on a mesh-grid structure is designed. A Boolean differential evolution (BDE) algorithm is used to optimize the mesh-grid structure as well as other parameters of the proposed antenna for good impedance matching in the UWB band. The optimized UWB antenna has a compact size of 24.2 × 32.2 mm and is fabricated and measured. According to the measured results, the proposed antenna yields a wide bandwidth, defined by S11 < -10 dB ranging from 2.8 to 11.2 GHz. And it shows that the BDE algorithm is an effective method for antenna design.
A novel, tri-band, planar plate-type antenna made of a compact metal plate for wireless local area network (WLAN) applications in the 2.4 GHz (2400-2484 MHz), 5.2 GHz (5150-5350 MHz), and 5.8 GHz (5725-5825 MHz) bands is presented. The antenna was designed in a way that the operating principle includes dipole and loop resonant modes to cover the 2.4/5.2 and 5.8 GHz bands, respectively. The antenna comprises a larger radiating arm and a smaller loop radiating arm, which are connected to each other at the signal ground point. The antenna can easily be fed by using a 50 Ω mini-coaxial cable and shows good radiation performance. Details of the design are described and discussed in the article.
A novel RCS (radar cross section) reduction configuration for a reflectarray antenna, employing the appropriate FSS (frequency-selective surface) as a ground, is proposed. The performance of a reflectarray element backed either by a solid metal ground plane or a frequency-selective surface is compared. To optimize the performance of the designed frequency-selective surface, a parametric study is carried out using Ansoft HFSS. Then, a prime-focus FSS-backed reflectarray is fabricated and tested. The measurements demonstrate that the gain of a FSS-backed reflectarray is about 0.5 dB lower than its counterpart backed by a solid ground plane. The RCS is nearly the same at the operating band of 10 GHz, while out of this band the FSS-backed reflectarray reduces the RCS strongly, especially at 1 GHz with the reduction up to 20 dB. Compared with the RCS reductions obtained in the other papers, the FSS-backed reflectarray using a ring element can also obtain a good result.
A compact printed dipole antenna using fractal shape for Radio Frequency IDentification (RFID) is presented. The proposed antenna consists of a third iteration fractal tree structure with the aim of reducing the antenna size. It occupies a volume of 78 × 30 × 1.58 mm3 and the radiator is composed of two arms. The antenna has been designed and optimized to cover the bi-band for passive RFID tag at 915 MHz and 2.4 GHz. A parametric study of the proposed antenna was carried out in order to optimize the main parameters. Details of the proposed antenna design and measurement results are presented and discussed.
A compact circularly polarized (CP) printed antenna for global positioning system (GPS) is proposed. The antenna adopts a two-layered stacked structure, in which a diagonally positioned rectangular patch is used as the driven part and capacitively loaded patch-based crossed dipoles are used as the main radiators. Good impedance matching is obtained conveniently by using magnetic-coupling feeding technique, and antenna size reduction is realized by using capacitively-loaded structure (50% size reduction in comparison with the conventional half-wave dipole antennas). A prototype of the antenna with the size of 46 mm × 46 mm is fabricated and tested. Good agreement is achieved between the simulated and measured results, which shows that the impedance bandwidth defined by 10 dB return loss is 34.8 MHz. In addition, the 3 dB-axial-ratio bandwidth is 8 MHz, and the antenna gain is about 7 dB.
In this paper, defected microstrip structure (DMS) is applied to design a compact microstrip rat-race hybrid coupler. The proposed structure introduces both harmonic signal suppression and a significant reduction of size because half of the ring is embedded in upper section. By embedding the DMS, it is observed that the third harmonic signal is suppressed to -25 dB with respect to a conventional rat-race hybrid coupler. Besides, this structure also effectively reduces the occupied area to 25% of the conventional case. Finally, using even and odd modes analysis the ABCD matrix of the proposed rat-race coupler was extracted. It is observed that the results are in good agreement with the full wave analysis and measurement.
This paper presents a novel CPW-fed band-notched UWB antenna for the 3.5 GHz wireless local area network (WiMAX) applications. The prototype consists of planar diamond shaped monopole and ground plane. By inserting a novel coupling band-notched filter, which consists of an isosceles trapezoid slot in the radiation patch and a same sized isosceles trapezoid patch on the back of the substrate, with the slot connecting to the patch below through shorting hole, band-rejected filtering property in the WiMAX band is achieved. The proposed antenna is successfully designed with broadband matched impedance, good radiation patterns and constant group delay.
A compact microstrip-fed ultra-wideband (UWB) planar monopole antenna with dual band rejected characteristic is presented in this paper. By etching two identical square complementary split ring resonators (CSRRs) in the radiation patch, dual band rejections in the WiMAX and WLAN bands are achieved. The proposed antenna, with the size of 30 × 34 mm2, has been constructed and tested. And the measured results show that the antenna can operate over the frequency band between 3 and 11 GHz for VSWR<2 with dual band notches of 3.4-3.6 GHz and 5.1-5.9 GHz. Besides, in the working bands, the antenna shows good omnidirectional radiation patterns in the H-plane and monopole-like radiation patterns in the E-plane and has good time-domain characteristic as well.
The paper deals with a method to measure the unknown impedance of metamaterial antenna made in Composite Right/Left-Handed (CRLH) Co Planar Wavegiude (CPW) technique for the millimeter wave frequency domain. The method uses a measurement setup made of a high frequency vector network analyzer (VNA) and an on-wafer characterization equipment. The measurement procedure consists in placing the probe-tip of the on-wafer equipment and to move it along the feedline of the antenna radiating structure until the minimum values of the return loss is reached. Using the facilities of the on-wafer equipment (micrometric screws to move the probe-tips) and knowing the geometrical dimensions of the antenna structure, the dimension and the position of an equivalent open-circuit matching stub are obtained. Then, using relationships derived from the transmission lines theory, real and imaginary parts of the unknown antenna impedance are computed.
We theoretically find that a bi-layer structure composed of two kinds of dispersive metamaterials can possess an asymmetric reflection spectrum due to Fano-type interference between a discrete reflection resonance and a broadband strong reflection. The discrete reflection resonance appears at the frequency around which the dispersive permeability is near to zero at oblique incidence. Based on analytical and numerical analysis, the asymmetric factor in the Fano-type reflection is found to be linked with the angle of incidence.
A novel hybrid design of Bluetooth and UWB antenna with dual band-notched functions is proposed. The proposed antenna structure consists of a microstrip-fed main patch and electromagnetically coupled parasitic patch with arc-shaped strips, achieving Bluetooth and UWB performance. Additionally, the split ring resonator (SRR) slot etched on the main patch and the square patch close to microstrip feedline are aimed to obtain dual notched bands. The numerical and experimental results exhibit that the designed antenna operates over the wide frequency band from 3 to more than 12 GHz, while showing the extra resonant mode at 2.4-GHz Bluetooth and the band rejection performance at 3.5-GHz WiMAX and 5.2-GHz WLAN.
A novel dual-mode bandpass filter (BPF) using stub-loaded defected ground open-loop resonator is proposed in this article. Defected arrow-shaped stub is loaded to a defected ground open-loop resonator, and two non-degenerate modes are excited for dual-mode characteristics. Based on even- and odd-mode theory, dual-mode characteristics of the resonator is analysed. Design equations for the defected-ground resonator are investigated. A two-pole dual-mode bandpass filter operating at 2.4 GHz with fractional bandwidth of 7.97% is designed, fabricated, and measured. Good agreement between simulated and measured results verifies the validity of this design methodology.
A novel microstrip-fed slot antenna with triple-band operation in compact size is proposed. The proposed antenna structure consists of a L-shaped microstrip feed line and open-ended slot on the ground plane, having small overall size of 14 x 34 mm2. The open-ended slot constructed of crossed double T-shaped slots is aimed to obtain resonant modes at 2.4/3.5 GHz. Meanwhile, with the use of a via-loaded metal patch connected to the edge of ground, the upper resonant frequency point at 5.8 GHz is achieved. The numerical and experimental results exhibit the designed antenna operates over triple frequency ranges, fulfilling the standards of 3.5-GHz WiMAX and 2.4/5.8-GHz WLAN. In addition, acceptable radiation characteristic is obtained over the operating bands.
A low-cost, high isolation, printed loop-antenna system for multiple-input multiple-output (MIMO) applications in the 2.4 GHz WLAN band is presented. By feeding the orthogonal eigenmodes of the array, port decoupling (S21< -20 dB) with tightly coupled elements (only 0.07λ separation) is obtained. The orthogonal eigenmodes are realized based on 180° coupler. Then decoupled external ports of the feed network may be matched independently by using conventional matching circuits. With this low-cost and high isolation characteristic, it is very suitable for being embedded inside a wireless access point (AP).
We present an empirical mixing model for rectangular cuboid metal inclusions in a host dielectric, suitable for replacing the detailed structure of a layer of on-chip interconnects with a homogeneous dielectric slab. Such an approximation is required to facilitate the accurate and efficient package-level electromagnetic modelling of complicated miniaturised systems, such as System-in-Package. Without such an approach, the direct inclusion of large areas of on-chip interconnect structures often results in intractable computation times. Our model allows us to predict the reflection (transmission) coefficient of impinging plane waves to within 3.5% (0.2%) error for incident angles up to 30o off-normal, aspect ratios 0.6-3, metal fill factors 0.3-0.6, and host dielectric constants 1-11.7, over the frequency range 1-10 GHz.
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