A microstrip tri-band bandpass filter (BPF) based on three embedded bending stub resonators (EBSRs) is proposed in this paper. Three resonant paths that resonate at three different frequencies can achieve three passbands. The lumped circuit models of the proposed filter are given for designing. The filter is extremely compact, whose area is about 0.047λg×0.12λg. There are two transmission zeros located between the first two passbands and a transmission zero between the second and third passbands, which results in good selectivity. For demonstrating the proposed filter structure, a filter at 0.9/2.14/3.6 GHz is designed and fabricated. The measured results are well agreed with simulated ones, which indicate the validity.
In recent years, the transmission/reflection (TR) method has been successfully emplolyed to determine the complex permittivity of dielectric material. Based on the principle that different coals have different abilities to absorb microwave energy at different frequencies, it is essential to analyze the electromagnetic property of coal to realize microwave desulfurization. Samples composed of a known dielectric and coal are manufactured in order to obtain the accurate permittivity of coal. In the article, we propose an improved TR method which is insensitive to the position of the sample in its cell. Additionally, we get the suitable mass ratio of the known dielectric and sample under test in the composite sample, and the suitable thickness of the composite sample in the permittivity measurements.
The reflectivity of three layer and four layer optical fiber based surface plasmon resonance sensors having silica material substrate and chalcogenide material substrate is plotted and studied. Using the transfer matrix method, the reflection coefficient for p-polarized incident lights at various wavelengths is obtained. It is observed that the sensitivity, detection accuracy and quality parameters of the sensor having silica substrates are much larger than the chalcogenide substrates. These parameters can also be increased by introducing an additional thin layer of silica/chalcogenide material on the metallic surface. Also, these sensor parameters are highly affected by the thickness of the additional thin layer.
The detailed analysis of localized elongated photonic nanojets generated by a graded-index microellipsoid is reported. Using high resolution finite-difference time-domain simulation, we have studied the distribution of the electric energy density within and in the vicinity outside a dielectric core-shell microellipsoid. Here we consider dielectric composite microellipsoid consisting of a core and several concentric shells having different types of index grading. It becomes possible to elongate the nanojet abnormally. The latitudinal and longitudinal sizes of a nanojet and its peak intensity depending on the optical contrast variation of shells are numerically investigated. The results may provide a new ultra-microscopy technique for optical detection of natural or artificially introduced nanostructures deeply embedded within biological cells.
A novel side-feed quasi-Yagi type antenna capable of triple-frequency operation at about 1900, 2400 and 3600 MHz is presented in this paper. The antenna is composed of a folded quasi-Yagi element and a modified CPW-to-CPS transition. The proposed antenna can be mounted perpendicularly to the feed circuit board of an array antenna so that it offers a novel design with a free degree of feed point so as to save device space, and its folded quasi-Yagi element can result in a low profile to the system. The experimental results demonstrate that the proposed antenna can operate over three frequency bands, with -10 dB reflection coefficient bandwidths of 200 MHz, 200 MHz, and 400 MHz at the central frequencies of 1.9, 2.4, and 3.6 GHz, respectively. Moreover, in the whole working bands, the antenna basically keeps the same radiation pattern and the gain is over 2.6 dBi.
A general design procedure of decoupling networks, between two coupled antennas, is proposed using a single transmission line connected between the input ports of the antennas at a specified distance. A rigorous analysis for the decoupling circuit is introduced considering the return loss of the antennas into calculations. Furthermore, using numerical optimization, enhancement of decoupling between the antenna ports achieved. Full-wave analysis and measurements are provided to verify the proposed technique.
A novel compact microstrip planar slot antenna with triple-band operations for WALN and WiMAX applications is proposed. The antenna, which occupies an overall dimension of 35×19×1.6 mm3, has a simple structure which consists of an asymmetric coplanar strip with a reverse G-shaped slot and a U-shaped open stub. The U-shaped open stub excites a resonant mode at 2.4 GHz. On the other hand the asymmetric coplanar strip could excite the resonant modes at 5.2 GHz. Meanwhile, the reverse G-shaped slot is aimed to excite resonant modes at 3.5 and 5.8 GHz. It has good omnidirectional radiation patterns in the azimuth plane and reaches 1.1 dBi at 2.4 GHz, 2.3 dBi at 3.5 GHz, 3.1 dBi at the band of 5 GHz. The designed antenna is simulated by HFSS software and a good agreement with experimental results is demonstrated.
A near-field focused antenna used as a feed for linear array is presented in this paper. This antenna is an H-plane sectoral horn with a biconvex dielectric lens placed in its aperture. This antenna focuses the beam in one plane (H-plane) to illuminate a linear array with a small width and provide a large aperture on the other plan to illuminate the length of the array. The simulated field distribution on the array is found to be in good agreement with the measurement of a prototype at 9.41 GHz.
Metal fiber content is often a measured parameter for electromagnetic shielding fabric (ESF). A commonly used method is combustion measuring, but measuring speed was slow and measured fabric damaged. This study proposes a new method based on computer image analysis for recognition of metal fiber content per unit area (MFCPUA) of the ESF, which aims at analyzing the MFCPUA without damage and providing a basis for the shielding performance evaluation of the ESF. Local region images of garment or fabric are obtained using high definition shooting system to build a gray matrix model which can describe the image. A recognition algorithm for fabric density based on gray extreme judgment is then given to construct a computation for the MFCPUA. The recognition results obtained with the proposed method is compared with the experimental results from manual combustion measuring, and the error reason and the application are also analyzed. Results of experiments and analyses show that the proposed method can identify the local fabric density with lossless and accurately calculate the MFCPUA, which provide a new method for electromagnetic shielding performance evaluation of the fabric and garment by computer technique.
A compact dual-band MIMO coupling element based antenna with high port isolation is proposed for the first time. The proposed antenna comprises four nonresonant coupling elements, the matching circuit, chassis of the mobile terminal, and de-coupling structures. The proposed antenna can cover two working bands of E-GSM900 and PCS1900. The measured results show that the isolation between the coupling elements operating at the same frequency is higher than 20 dB. The proposed structure can be applied to the MIMO system.
In this paper, a waveguide filter using miniaturized-element frequency selective surface (FSS) is presented. The proposed FSS is composed of periodic array of metallic patches separated by small gaps and metallic lines. The array of patches constitutes a capacitive surface and the lines a coupled inductive surface, which together act as a resonant structure. At about 5.0 GHz, a narrow bandpass response is designed. Dimensions of the FSS element are much smaller than the operating wavelength, which is less than 1/13λ. For this miniaturized element, grating lobes are restrained and do not appear event to 25 GHz. Moreover, the FSS has stable performances for various incident angles. Design procedure and measurement results of the FSS are presented and discussed.
In this paper, a compact three-order mixed-cross coupled bandpass filter (BPF) with enhanced frequency selectivity is proposed. Multiple transmission zeros (TZs) can be obtained near the passband for high frequency selectivity by introducing mixed-cross coupling between the nonadjacent resonators. The frequency-dependent mixed-cross coupling matrix of the proposed filter is presented to explain the occurrence of the TZs caused by mixed-cross coupling. A new BPF centered at 2.7 GHz with 11.5% fractional bandwidth has been designed and fabricated to verify the validity of the proposed method. The measurement result shows four finite TZs in the stopband, located at 1.74 GHz with 52.16 dB rejection, 2.53 GHz with 24.67 dB rejection, 3.83 GHz with 47.52 dB rejection, and 7.75 GHz with 54.83 dB rejection, respectively. The circuit only occupies 6.2×7.6 mm2.
A compact microstripbandpass filter using miniaturized hairpin resonators is presented in this letter. Two modified stepped impedance hairpin resonators connected by parallel coupling are designed for the bandpass filter. The proposed miniaturized hairpin resonator is composed of amicrostrip line and rectangular ring structures between parallel high impedance lines. A big capacitance in the hairpin resonator is provided by the gaps ofrectangular ring structures in the parallel high impedance lines. Therefore, the proposed bandpass filter using the hairpin resonators has a low insertion loss, low return loss and compact size. The proposed bandpass filter with acenter frequency of4.96GHz is designed with EM full wave simulator IE3D andverified with experiment.
This paper presents a compact band stop filter (BSF) based on the dual metal plane configuration with multiple rejection zeros (RZs). Quasi-lumped technique with novel patch-via-spiral dual mode resonator is applied to the design of the proposed filter. Multiple rejection zeros are introduced by open-end stubs for high selectivity. Design equations are obtained by using a lossless transmission line model. The calculated results show that the lower and upper rejection zeros can be easily tuned by the coupling capacitor and the open-end stubs respectively. By using the Microstrip-Coplanar-Waveguide (CPW) structure, the size of the proposed filter can be reduced to 12.8 mm x 9 mm(i.e., 0.24λg x 0.17λg), where λg denotes the guided wavelength at center frequency.
A novel coax-fed wideband loop antenna loaded with rectangular patches and U-shaped elements is presented and studied. By inserting a pair of rectangular patches inside the strip loops and employing a pair of U-shaped elements as the parasitic resonators, two additional resonances are excited and a good performance of bandwidth enhancement can be obtained. The measured results indicate that the impedance bandwidth (VSWR≤2) is about 87.1% from 1.58 to 4.02 GHz, which covers the required operating bands of DCS1800 (1710-1880 MHz), PCS1900 (1850-1990 MHz), UMTS2100 (1920-2170 MHz), WLAN2400 (2400-2484 MHz), LTE2300/2500 (2300-2690 MHz) and WiMAX3500 (3300-3690 MHz). In addition, good radiation characteristics such as symmetrical radiation pattern, moderate peak gain, low back radiation, and low cross-polarization are observed over the entire operating band.
The design and ultra-wideband performance of a cavity-backed bowtie antenna with the parasitic dipole and parasitic circular ring is presented. Besides the elliptical bowtie dipole and the taper feeding microstrip for obtaining ultra-wideband impedance characteristics, the parasitic dipole and parasitic circular ring to effectively improve the radiation pattern can be used for obtaining the stable broadside unidirectional radiation patterns. An ultra-wideband impedance characteristic of about 118.2% for VSWR ≤ 2 ranging from 2.75-10.7 GHz is achieved. A unidirectional radiation pattern, a stable peak gain of around 7.4-10.8 dBi and low cross polarization over the whole operating band are also produced. A prototype has been fabricated and tested, and the experimental results validate the design procedure.
A novel structure of dual-composite right/left-handed transmission line (D-CRLH-TL) is proposed in this paper, and its electromagnetic characteristics are investigated in theory and simulation. The dispersion curve of the proposed structure has been derived by using Bloch-Floquet theory. The structure is composed with an "H"-shaped defected ground structure (DGS) and two stubs with rectangular patches, compared with the structure of D-CRLH-TL proposed in paper  and , this structure is simpler and more easily adjusted. Then, an ultra wide-stopband (UWSB) bandstop filter based on the proposed D-CRLH-TL is designed, fabricated, and measured. The simulated and measured results show that the centre frequency of the filter is 5.1 GHz, the bandwidth of stopband is 90.2%, and the filter has sharp transmissions at the two edges of the stop-band. Besides, the designed filter in this paper has a smaller size than traditional ones, and can be easily fabricated.
This paper presents a novel design of dual-linear-polarized broadband horn antenna for 6~18 GHz frequency band. Applying commercial software Ansoft HFSS, parametric analysis is taken with respect to the best antenna performance and manufacturing tolerance. The proposed antenna is finally fabricated and measured, and the measured results show that the designed antenna exhibits low VSWR (<2), high gain (13 dBi~19.5 dBi) and high isolation (>25 dB) without beam splitting in the entire operation band.
A novel Vivaldi antenna with low radar cross section (RCS) for ultra-wide band (UWB) applications is proposed in this paper. As a printed antenna with electrically large length, the Vivaldi antenna has large backscattering when the incident waves are in the grazing directions. By sleeking the edges of the proposed antenna, the reflected currents are reduced so that the peaks of the backscattering can be inhibited. Its radiation characteristics are simulated and verified. The RCS performance of the proposed antenna is studied and compared with that of a commonly used Vivaldi antenna. The result shows that the proposed antenna has lower RCS than the reference antenna in both the perpendicular and grazing directions while maintaining similar radiation characteristics. So the results illuminate that the proposed Vivaldi antenna is a good candidate in the design of printed UWB end-fire antennas requiring low RCS.
The design approach and development of a right hand circularly polarized wideband microstrip antenna for multi-constellation Global Navigation Satellite System (GNSS) is presented. The antenna is corner truncated square patch, parasitically excited by a dielectric covered straight probe. A thermacol layer of thickness λ/14 at center frequency is used to support the microstrip over the ground plane substrate. The simulated and measured results are presented. The antenna shows wide beam radiation patterns with axial ratio less than ± 1 dB. Its VSWR is better than 2.8:1 and the gain varies from 1.2 dBi to 3.5 dBi over the frequency band. L5