A simple and effective method of bandwidth enhancement for the printed meander line antenna (MLA) is proposed. This approach is characterized by symmetrically printing two meandering sections on both sides of a dielectric substrate and connecting them via shorting pins at the bottom of meandering sections, which are connected to a capacitive stripe for impedance matching. The illustrative equivalent circuit and the corresponding principle of bandwidth enhancement of this double-layered MLA are presented. The measured results of these double-layered and single-layered MLAs manifest the validity of our design approach.
In this paper, a rectangular metallic monopole antenna with normal rectangular stubs is presented for application in ultra-wide band communication systems. It is shown by computer simulations (HFSS and CST) and actual fabrication and measurement that the addition of protruding normal metallic stubs lead to the increase of impedance band width. The optimum design of geometrical dimensions of the antenna (consisting of the monopole plate and stubs) achieves up to 10 dB return loss in the UWB (3.1-10.6 GHz) frequency range. The radiation efficiency of antenna is better than 95%. Furthermore, the antenna provides linear polarization, with quite low cross-polarization levels.
In this paper, a quad-antenna system for laptop computers is studied. Because two dual-antenna systems can construct a quad-antenna system, the dual-antenna systems in the open literature are utilized. The mutual coupling between the two dual-antenna systems is analyzed and reduced. To validate the design of a quad-antenna system, the quad-antenna system, consisting of two dual-antenna systems proposed in the open literature and a decoupling element, is fabricated and tested. Its measured -10 dB impedance bandwidths are 200 MHz (2.33-2.52 GHz) and 1.62 GHz (4.5-6.12 GHz). The measured mutual couplings are below -15.5/-19 dB at the 2.4- and 5.2/5.8-GHz WLAN bands, respectively. The measured gains are better than 2.4/3.9 dBi with efficiencies higher than 70%/72% at the two bands, respectively. The envelop correlation coefficient is evaluated based on the measured results.
This paper investigates the use of double concentric circular ring elements arranged in a sub-wavelength grid on a single layer of substrate, in an effort to enhance the beam-scanning capability of reflectarrays. The work is done at 10 GHz on a 405 mm×405 mm aperture. In addition to a broad gain bandwidth, the reflectarray with a sub-wavelength grid exhibits a superior beam-scanning performance compared to the one with λ/2 grid. The measured results show that the reflectarray with 0.3λ grid spacing achieves a 1-dB gain bandwidth of 22% with an aperture efficiency of 56.6%. With the reflectarray fixed, this paper studies the possibility of beam scanning by displacing the feed horn laterally. The results show that beam scanning of ±15º is possible while preserving the broadband characteristics. It is also observed that a 1-dB gain bandwidth of 28% is achieved for the 0.3λ array when the feed is displaced laterally with an angle of 30º.
In this paper, a compact asymmetric coplanar strip (ACS)-fed printed monopole antenna for tri-band WLAN/WiMAX applications is presented. The proposed antenna is composed of a circular-arc-shaped stepped monopole with dual operating frequencies at 2.4/5.7 GHz and a simple circular-arc-shaped strip with the third operating frequency at 3.5 GHz. The three resonant frequencies of the antenna can be controlled by adjusting the geometries and the sizes of the stepped monopole, the strip and the ground plane. The antenna occupies a very compact size of 22.1×12 mm2 including the ground plane, has nearly omnidirectional radiation characteristics and reasonable gain in the operating bands. The simple feeding structure, compactness and uniplanar design make it easy to be integrated within the portable device for wireless communications.
Equilateral-triangular slot antennas with modified edges for wideband circular polarization are proposed in this paper. Circular polarization was firstly obtained by adding two asymmetric perturbations to two edges of triangular slot. Then fractal-like boundaries were adopted in the antenna design for size reduction and broadband operation. Two antenna prototypes for RFID readers were fabricated to cover RFID UHF band and ISM 2.4 GHz band, respectively. Measured results show that the presented antennas obtain fairly wide 3-dB axial ratio bandwidths of 15.7% (820-960 MHz) and 19.8% (2.18-2.66 GHz).
An analytical expression of AC resistance of a single-layer air-core Helmholtz coil is presented. Proximity effects between both bundles and strands of litz-wire as well as skin effect are considered. To obtain an accurate analytical expression of proximity effect on bundle level and strand level, a precise distribution of magnetic field is discussed. The analytical expression of AC resistance and quality factor is verified with the experimental results, and the theoretical predictions are in agreement with the measured results.
A broadband printed quadrifilar helical antenna (BPQHA) integrated with a broadband feeding network for satellite communications is proposed. Using a multiple arm technique, satisfactory antenna characteristics over a wide bandwidth are realized. To feed the antenna, a novel compact broadband feeding network composed of a frequency independent 180° out-of-phase power divider, two Wilkinson power dividers and two broadband 90° phase shifters is designed. The measured boresight gain remains positive with a reflection coefficient lower than -11 dB over a bandwidth of approximately 26%. The axial ratio is below 1.7 dB and the half-power beamwidth is more than 120° over the same bandwidth. Details of the proposed antenna design are provided and discussed, as well as the experimental results.
In this paper, a new approach for the radar cross section (RCS) reduction of patch array antenna is proposed. Complementary split-ring resonators (CSRRs) are etched on the ground of the proposed patch antenna array. A conventional 1 × 4 patch antenna array is designed with the central frequency of 5.0 GHz. The monostatic RCS of the patch antenna array with CSRRs can be reduced as much as 14 dB compared to that of the conventional array while maintaining almost the same radiation characters. For the case of φ-polarized incident wave, the RCS has been reduced in the angular range of -90° ≤ θ≤+90° in xoz-plane and this angular range is usually less than ±45° when using conventional methods of RCS reduction.
The design of a dual-frequency single-layer circularly polarized reflectarray with frequency selective surface (FSS) backing is presented in this paper. The proposed reflectarray consists of rotated cross dipole elements etched on an FSS-backed substrate. Compared with the conventional design, the FSS layer reduces the mutual effect between the elements of two bands between the elements of two frequencies. The technique of element rotation ensures the proposed reflectarray obtain excellent performance of circular polarization. A dual-frequency circularly polarized reflectarray with FSS backing is fabricated and tested. All the simulated and measured results demonstrate these advantages.
A miniaturized Gysel power divider/combiner(PDC) based on planar artificial transmission line (ATL) is presented in this paper. This planar ATL is composed of microstrip quasi-lumped elements and their discontinuities, and the ATL is capable of synthesizing microstrip line with various characteristic impedances and electrical lengths. For demonstration, the simulated and experimental results of the proposed PDC @1 GHz implemented on microstrip are given. Experimental results of the designed PDC agree well with the theoretical predictions. The proposed Gysel PDC circuit not only demonstrates low insertion loss at the fundamental frequency with compact size and high frequency suppression features, but also maintains Gysel PDC's high power-handling advantage. The occupied sizes of the proposed Gysel PDC are merely about 40% of the conventional Gysel PDC.
In this paper, initially a Planar Inverted Cone Metal Antenna (PICMA) is optimized for wideband wireless communication. Finally, a compact Shorted Planar Inverted Cone Metal Antenna (SPICMA) is developed by introducing a shorting strip on the radiating element of optimized PICMA. The PICMA is optimized to operate from 1.7 GHz to more than 20 GHz, and the SPICMA is optimized to extend the operating band from 1.05 GHz to more than 20 GHz resulting in size reduction of 38%. The proposed antenna yields bidirectional radiation pattern in E and H planes. Various characteristics of the antenna have been analyzed using Finite Integration Technique (FIT) based commercial software CST studio. The measured reflection coefficient agrees with the simulated result for the optimized SPICMA.
An eight-way waveguide-based power combiner/divider is presented and investigated in the frequency range 7.5-10.5 GHz. A simple approach is proposed for design purposes. The measured combiner shows a good agreement between the simulated and measured results. Insertion loss is about -0.3 dB, return loss is less than -15 dB and isolation between adjacent output ports is better than -11 dB at 8.5 GHz and reaches about -14 dB at 9.5 GHz.
The hybrid approach based on the coupling of the Wave Concept Iterative Procedure method and the Frequency Domain Transmission Line Matrix method is improved. The proposed method reduces the computation time by solving waves at the planar circuit interface: the volumic method is replaced by an equivalent surface condition. Thanks to this new approach, planar circuits presenting inhomogeneous dielectric substrates are studied. The proposed approach is compared to other methods on several examples.
In this paper, flux of permanent magnet tubular linear generator (PMTLG) is modeled and analyzed. With the model, air-gap leakage flux coefficient can be expressed analytically in terms of permanent magnet dimensions and air-gap width. The validity of analytical expression of air-gap leakage flux coefficient is verified by finite element analysis (FEA) with a maximum error of 6.8%. Furthermore, longitudinal end flux's influence on the detent force of PMTLG is analyzed in detail with the model. A detent force minimization technique is deduced from the analysis results, and confirmed by FEA. Finally, after optimization of air-gap leakage flux coefficient and detent force, a PMTLG is built and experimented.
A novel omnidirectional circularly polarized (CP) antenna with single feed is proposed for 2.4 GHz WLAN applications. Based on the zeroth-order resonance (ZOR) mode of epsilon negative (ENG) transmission line (TL), the antenna excites uniform vertically polarized E-field just as the monopole does. A modified Alford loop with electromagnetic coupling fed by L-shaped strip consists of four curved branches, which is placed on the top of the antenna and generates an equivalent horizontally polarized magnetic dipole mode. Once the two orthogonally polarized components are equal in amplitude but different in phase by 90˚, omnidirectional CP wave can be obtained. The measured results show that the impedance bandwidth (S11<-10 dB) is 6% (2.38-2.53 GHz), and the 3-dB axial ratio bandwidth in the azimuth plane is very wide which achieves 54% (1.60-2.80 GHz). Additionally, the 3-dB axial ratio beamwidth is over 50˚ for radiation pattern in elevation plane. Moreover, the antenna achieves excellent omnidirectional right-hand CP performance with a variation of 0.5 dB in the azimuth plane and an average gain over 1.5 dB across the operating band, which are well applied to the wireless system.
A single-feed dual-band dual-sense circularly polarized (CP) microstrip antenna is proposed. The antenna consists of a circular radiating patch with a ring slot, two substrates with an air layer sandwiched between them and a capacitive coupling feed. The two resonant frequencies are controlled by the size of the circular radiating patch and the ring slot. By introducing the perturbation, the fundamental resonant mode splits into two orthogonal degenerate modes, and the CP radiation pattern is obtained. Capacitive disk coupling feed is also used in the design to enhance the band-width. The key parameters of the design are investigated to show how to obtain dual-band and dual-sense CP. The proposed antenna prototype is fabricated and measured. Experimental results show that good CP radiation performances are obtained at both resonant frequencies.
A compact band-notched ultra-wideband (UWB) spatial diversity antenna is presented in this paper. The antenna is fabricated on an FR4 substrate and consists of two tapered microstrip feeding lines and two radiating elements. The wireless local area network (WLAN) for IEEE 802.11a operating in 5.15-5.825 GHz and-notched function is achieved by introducing two slits in the radiators as λ/4 resonators. The simulated and measured results show that the presented antenna has a broadband impedance bandwidth which covers UWB band and also has a band-notched characteristic. Additionally, the antenna has a good transmission coefficient better than -15 dB across the UWB. The radiation patterns, peak gain, and envelope correlation coefficient are measured and discussed.
A novel dual-band circularly polarized (CP) antenna with wide axial ratio (AR) and impedance bandwidths is proposed. Based on a rectangular ground, the antenna consists of a trapezoid patch, an L-shaped strip, a cavity, and T-shaped and L-shaped perturbations. By embedding a feeding line with a trapezoid patch and an L-shaped strip, dual-band input impedance performance and a CP performance at upper band are obtained. In order to achieve a CP performance at the lower band, a T-shaped perturbation is embedded inside the slot. Moreover, the CP performance is enhanced by inserting an L-shaped perturbation at the right bottom corner of the slot. Furthermore, using a cavity underneath the antenna, unidirectional radiation patterns with greatly gain enhancement are obtained. The measured results show that the impedance bandwidths for S11<-10 dB are 22.7% (2.34-2.94 GHz) and 79.8% (4.64-10.8 GHz) while the axial ratio bandwidths (AR<3 dB) are 26.4% (2.3-3 GHz) and 12.6% (5.2-5.9 GHz) at the lower and upper bands, respectively. Additionally, the measured gain is more than 7.4 dB and 2.4 dB in the two operating bands, respectively. Thus, the antenna can be well applied for both 2.4/5.8 GHz WLAN bands and 2.5/5.5 GHz WiMAX bands.
In this paper two novel antennas, suitable for access and backhaul links, are designed, fabricated and tested for a Relay Station in a WiMAX wireless network. A single modified E-shaped patch antenna is described, presenting 10 dB gain over 12.4% bandwidth. This antenna element is used for the design of a 4×4 planar array which provides experimental gain of 21.2 dB. The antenna system on the Relay Station operates at 3.4 GHz and includes one single antenna element for access link realization and an antenna array for the backhaul link realization. These antennas are installed in two configuration arrangements and tested in terms of their radiation performances and coupling effects. The simulated and measured results are quite satisfactory and in good agreement at which the maximum coupling between the access and backhaul antennas is found below -25 dB for all tested cases.
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