A CPW-fed slot antenna for achieving dual-band dual-sense circular polarization is introduced. The dual-band circularly polarized operations are generated by the slots loaded in the two opposite corners and the halberd-shaped strip connected at the end of the signal line of the CPW. The left-hand and right-hand circularly polarized performances can be achieved simultaneously for the lower and the upper band, respectively. The measured impedance bandwidth for 10-dB return loss at 2.5 and 3.5 GHz operating bands can be up to 1100 MHz and 260 MHz, respectively. The measured 3-dB axial ratio bandwidths are 30.8% for lower band (LHCP) and 3.1% for upper band (RHCP), which are completely inside their respective impedance bands. The designed antenna has a simple uniplanar structure and occupies a compact size of 40×40 mm2, including the finite ground CPW feeding mechanism. Moreover, the antenna gain variations across the two operating bands are less than 1 dB.
A novel compact dual-band bandpass filter using spiral resonators and input/output (source-load) direct coupling structure has been presented. Two different transmission paths are utilized to realize independently controllable central frequencies and bandwidths for each passband. In addition, three transmission zeros has been introduced to improve the frequency selectivity. A dual-passband filter centered at 2.41 GHz and 4.22 GHz is designed, simulated, and fabricated to demonstrate the performance of the proposed filter structure. The measured results show good agreement with the simulated ones.
A novel compact monopole antenna with triple-band operation is proposed in this paper. The proposed antenna, fed by a 50-Ω microstrip line, consists of an inverted-L-shaped microstrip feed line loaded with a parasitic strip and a protrudent mirrored quasi-F-shaped strip on the ground plane, with a compact overall size of 20×25 mm². The protrudent mirrored quasi-F-shaped strip is aimed to excite a resonant mode at 2.4 GHz. Meanwhile, with the introduction of the parasitic strip to the inverted-L shaped strip, two adjacent resonant frequencies at 5.2/5.8 GHz are obtained. The numerical and experimental results exhibit the designed antenna operates over triple frequency ranges, satisfying the standards of wireless local area networks (WLAN) both in IEEE 802.11 b/a/g at 2.4-GHz, 5.2-GHz, and 5.8-GHz. Besides, the antenna is fabricated and measured, and the simulation and measurement results of the return loss, radiation patterns and peak antenna gains are studied showing that the presented antenna is in good performance.
A novel dual-side mushroom ground plane (DMGP) structure is proposed for the noise suppression in high-speed multilayer printed circuit boards (PCBs). The proposed method is localized suppression technique where a dual-side mushroom structure is placed below the noise-sensitive device. In multilayer PCBs with DMGP, noise between two ports with large or small ports spacing can be minimized effectively, which is flexible for the layout of mixed-signal system. Wideband noise suppression is achieved for the fabricated boards even though the port spacing is only 3.5 mm.
Novel compact multiband microstrip transversal bandpass filters (BPF) using short-circuited or open-circuited stub-loaded half-wavelength resonators (SLR) are presented. The dual-band BPF consists of two SLRs and two T-shaped feedlines, and the tri-band BPF can be implemented by a simple reconfiguration of adding one resonator above the original circuit of the dual-band BPF. Multiple transmission zeroes are created to improve the selectivity of the filters. Furthermore, the high degree of design freedom is obtained for every passband of dual- or triple-band BPF is achieved by independent resonators and independent signal paths. To verify the proposed concept, two dual-band bandpass filters (filter I and II) and one tri-band bandpass filter (filter III) are designed and fabricated. Both theoretical and measured results are presented, with good agreements.
A microstrip based Ultra-Wideband (UWB) Bandpass Filter (BPF) with a notch at WLAN and simultaneously improved stopband till 18 GHz is proposed. Meander shaped Defected Ground Structures (DGS) are used to implement the notch (which can be increased in width and number) within the passband and double U-shaped DGS present under the input and output feeding lines are used to attain the suppressed stopband. Experimental results are in good agreement with the simulated data.
In this paper, a novel circular ring patch antenna with tri-band operation is proposed for satisfying WLAN and WiMAX applications simultaneously. The proposed antenna consists of a circular ring patch, a straight strip and a door-shaped strip, all of which are printed on the top side of the substrate. The straight strip embedded in the rectangular slot is aimed to obtain resonant mode at 5.5GHz. With the use of a door-shaped strip symmetrically with the microstrip feed line, the proposed antenna can operate in three separate bands. The proposed antenna has been fabricated and tested. The numerical and experimental results exhibit the designed antenna operates over triple frequency ranges, and the 10 dB return loss bandwidths of the proposed antenna are 570 MHz (2.27-2.84 GHz), 470 MHz (3.35-3.82 GHz) and 1720 MHz (4.84-6.56 GHz), which can fulfill both the WLAN bands (2.4-2.484 GHz, 5.15-5.35 GHz, and 5.725-5.825 GHz) and the WiMAX bands (2.4-2.6 GHz, 3.4-3.6 GHz, and 5.25-5.85 GHz). In addition, a design evolution and a parametric study of the proposed antenna are presented to provide information for designing, modifying, and optimizing such an antenna. At last, the proposed antenna has an unusual advantage of omnidirectional radiation characteristics and stable gain over the whole operating bands.
Present study shows the development of integrated rain drop size distribution (DSD) model and gives a comparative study with DSDs of different regions in India. This work is useful for estimation of rain induced attenuation. Rain data of five different regions (Ahmedabad, Shillong, Thiruvananthapuram, Kharagpur and Hasan) was used for this work. Attenuation characteristics are different for different regions because DSD varies according to the climatic conditions. Development of DSD model for each location is not feasible. It is a demand to develop a integrated DSD model which gives the tolerable error in DSD for different regions, so that, it can be adjusted in fade margin of the communication system. The result of this work shows the good correlation between the proposed integrated DSD model and DSDs of different regions.
In this paper, the problem of predicting far field magnitude from near field measurements of an equipment under test (EUT) is studied. Firstly, a multiple magnetic dipole model is developed to simulate the magnetic behavior of the EUT. The parameters of the model (dipoles positions and magnetic moments) are calculated using the values of the near field applying the Particle Swarm Optimization (PSO) algorithm. For the evaluation of the method, extended simulations were conducted, producing theoretical values and distorting them with noise, and then the developed algorithm was used to create the proper model. Finally, the theoretical results are compared to the field assessments the proper models produced.
A new design for circularly-polarized (CP) slot antennas is first described. The antenna is a combination of a shorted square-ring slot and an L-shaped linear slot, and its CP operation frequency can be easily tuned under the condition that the slot area is unchanged. Based on the CP design, two reconfigurable slot antennas are then developed. One is a frequency reconfigurable antenna, whose CP operation frequency can be switched between two adjacent frequencies. The other is a polarization reconfigurable antenna, whose polarization can be switched between two orthogonal CP senses. The two reconfigurable antennas are realized using PIN diodes. Details of the designs and experimental results are shown.
A new design of a circularly-polarized (CP) trapezoidal dielectric resonator antenna (DRA) for wideband wireless application is presented. A single-layered feed is used to excite the trapezoidal shaped dielectric resonator to increase resonant frequency and axial ratio. Besides its structure simplicity, ease of fabrication and low-cost, the proposed antenna features good measured impedance bandwidth, 87.3% at 4.21GHz to 10.72 GHz frequency bands. Moreover, the antenna also produces 3-dB axial ratio bandwidth of about 850 MHz from 5.13 GHz to 6 GHz. The overall size of DRA is 21 mm x 35 mm, which is suitable for mobile devices. Parametric study and measurement results are presented and discussed. Very good agreement is demonstrated between simulated and measured results.
A novel K-band harmonic dielectric resonator oscillator (DRO) is presented. Two identical parallel feedback DROs constitute a symmetric structure by sharing the same dielectric resonator (DR). As a result of this special structure, the odd frequency output components offset while the even harmonic frequency components superimposed at the output port. Odd and even mode analysis method is used in theoretical analysis. As the experimental results shown, the fundamental frequency is 9.45 GHz and the output power at the second harmonic frequency of 18.9 GHz is 9.45 dBm. The suppression of fundamental frequency is about 15.5 dBc. A phase noise of -97 dBc/Hz@100 KHz and -78 dBc/Hz@10 KHz is achieved at the output frequency.
Material properties in radio frequency and microwave regimes are limited due to the lack of molecular resonances at these frequencies. Metamaterials are an attractive means to realize a prescribed permittivity or permeability function, but these are often prohibitively lossy due to the use of inefficient metallic resonators. All-dielectric metamaterials offer excellent potential to overcome these losses, but they provide a much weaker interaction with an applied wave. Much design freedom can be realized from all-dielectric structures if their dispersion and anisotropy are cleverly engineered. This, however, leads to structures with very complex geometries that cannot be manufactured by conventional techniques. In this work, artificially anisotropic metamaterials are designed and then manufactured by 3D printing. The effective material properties are measured in the lab and agree well with model predictions.
This paper presents a novel compact microstrip hybrid four-mode bandpass filter (BPF) with good selectivity and multi-transmission zeros. By adding an external resonator to a triple-mode stub-loaded uniform impedance resonator, four modes are generated in the desired passband and a hybrid four-mode BPF is implemented. Even- and odd-mode theory is introduced to investigate the mode characteristics of triple-mode resonator in detail. Circuit model and coupling matrix are built to further explain the proposed methodology. A microstrip BPF with central frequency of 3.4 GHz for wireless communication was designed and fabricated. Three transmission zeros are obtained at 3.2 GHz, 3.55 GHz and 3.73 GHz, which improve selectivity and out-of-band rejection of the filter. The measured results of the fabricated filter represent good in-band and sharp sideband characteristic, which match well with simulated results.
In this paper, a new ultra-wideband (UWB) disc antenna compatible with cognitive radio is presented. The proposed antenna is developed to operate from 0.77 to 11.23 GHz. It consists of a circular disc radiator with a rectangular slot on the patch and the implementation of the bevel technique on the ground plane. A prototype of the antenna has been constructed and shows adequate impedance matching, radiation pattern and gain for cognitive radio applications.
A low-profile microstrip planar monopole antenna with triple-band operation for WiMAX and WLAN applications is proposed. The antenna has a simple structure which consists of a rectangular radiation patch with an L-shaped slot and an inverted L-shaped stub extending from the ground plane. By etching an L-shaped slot on the rectangular radiation patch, the antenna can excite two resonant modes. The third resonant mode is introduced by extending an inverted L-shaped stub from the ground plane. The designed antenna has a small overall size of 17*30 mm2. A prototype is designed, fabricated, and then measured. The experimental and simulation results show good impedance bandwidth, radiation pattern and stable 9gain across the operating bands.
A multi-monopole-antenna system capable of generating two wide operating bands with good input matching by a voltage standing wave ratio (VSWR) of 1.5 to cover the 2.4 GHz (2400-2484 MHz), 5.2 GHz (5150-5350 MHz), and 5.8 GHz (5725-5825 MHz) bands for wireless local area network (WLAN) applications is introduced. The design mainly comprised three, metal-plate, monopole antennas symmetrically located on a main, hexagonal, ground plane and backed by vertical, step-shaped grounds protruding thereon. The step-shaped grounds not only facilitated the attaining of wide impedance bandwidth but also good port isolation. In addition, directional antenna radiation was also produced. Further, a triangular-cylinder shielding wall was placed in the center of the main ground plane for integration of the wireless, surveillance-camera module into the proposed antenna system. Details of the design prototype are described and discussed in the article.
This article presents a coplanar printed monopole antenna for digital television (DTV) in the UHF band (470-862 MHz) application. The antenna structure consists of a meander loop monopole for radiation, a step-shaped ground plane for impedance matching, and a 50-mini coaxial feedline for excitation. The meander loop monopole and step-shaped ground plane are printed on the same side of a substrate with an area of 15×170 mm2. The measured impedance bandwidth for 2.5:1 voltage standing wave ratio (VSWR) is 550 MHz (465-1015 MHz, 74%), covering the DTV band. In addition, the proposed antenna shows a real reception performance on a notebook computer. The reception results for audio and video signals exhibit stable characteristics.
A circular polarization microstrip antenna with a single feeding point is designed in this paper. The microstrip patch has a structure of Koch fractal edges, and the circular polarization is realized by inspiring two degenerate modes that are orthogonal to each other. The software CST MWS® is used to simulate the designed antenna. The simulation results indicate that circular polarization radiation could be achieved though feeding at one of the diagonal lines of the patch by a probe. Antennas considering substrate medium loss are also simulated, and the results are approximate to those with ideal substrates. According to the simulated results of the surface currents at the edges of the patch, an equivalent line current radiation model is proposed to describe the radiation characteristics of the designed antenna. A circular polarization microstrip antenna is fabricated and tested. The simulated, calculated, and the measured results agree well. The designed antenna operates at 1.575 GHz, with an impedance bandwidth of 3% for VSWR < 2, the gain of the antenna is 2.6 dB, and the axial ratio in the maximum radiation direction is 2.7 dB.
In this paper, a numerical study based on the Finite Element Method (FEM) formulation of Ansoft's High Frequency Structure Simulator (HFSS) is reported to investigate the performance of a conformal Broadside Coupled Rectangular Split Ring Resonators (BC-SRR) of negative effective permeability around a resonant frequency of 1.27 GHz for non-linear polarization applications. The size of the BC-SRR is 15 mm x 15 mm x 0.8 mm on a polyimide substrate with a relative permittivity of 3.5 and a loss tangent of 0.004. The performance of the BC-SRR is characterized in terms of reflection and transmission spectra, effective relative permittivity and permeability, and the dispersion diagram for both flat and twisted profiles. The flat BC-SRR operates over the frequency range from 1.2615 to 1.2842 GHz. The twisted BC-SRR inclusions are investigated at 90°. It has been found that the resonant frequency is changed to 1.1064 GHz and bandwidth becomes from 1.08 GHz to 1.0537 GHz for the twisted profile. Moreover, it is found that the unit cell of the twisted BC-SRR profile is based on two BC-SRRs inclusions. Furthermore, it is found that the twisted profile exhibits negative relative permittivity and permeability simultaneously.