A symmetrical terahertz metamaterial for dual-band operation is designed and fabricated. The proposed metamaterial is composed of periodically arranged cruciform and square metal loops. Due to the symmetrical structure, this metamaterial is insensitive with the polarization of the incident wave. Transmission and reflection characteristics of the proposed structure are simulated using Ansoft HFSS, and the negative permittivity is figured out in 378-500 GHz and 626-677 GHz bands. The designed sample is fabricated on a gallium arsenide layer, and experiments are performed in Terahertz Time-Domain Spectroscopy. The experimental results agree well with the simulations.
three novel structures of coplanar waveguide (CPW) cross-coupling-fed antenna with different kinds of broadband radiant loads, which are applied in C wave band, are presented. The simulated results by CST MICROWAVE STUDIO® indicate that these structures of antenna are able to expand bandwidth, improve gain and maintain good omnidirectional radiation characteristics while the sizes of the structures are relatively small. The antenna surface current simulated by CST is extracted, explaining the mechanism of broadband, high-gain and omnidirectional radiation characteristics of the antenna. Three structures of antenna with different kinds of broadband radiant loads are designed, manufactured and measured. The antenna is printed on FR-4 epoxy substrate with 0.5 mm thickness. According to the measured results of these three structures, the operating bandwidths with a reflection coefficient lower than -10 dB are 4.27~4.90 GHz, 4.04~5.07 GHz and 4.05~4.87 GHz. The relative bandwidths are up to 13.7%, 22.6% and 18.4% respectively. The H-plane maximum omnidirectional gains are 6.6 dB (4.8 GHz), 6.8 dB (4.6 GHz) and 7.8 dB (4.6 GHz), and the maximum magnitudes of un-roundness are 3.0 dB, 2.8 dB and 2.8 dB (4.5 GHz) respectively. The measured and simulated results do not differ much from each other. The overall sizes of the antennas are 133.5 mm × 4.4 mm (triangular load), 148.2 mm × 8 mm (cutting semi-circular load) and 145.65 mm × 6.1 mm (circular load) respectively, and the gains per electronic length on the polarization direction are 3.2 dB, 3.0 dB and 3.5 dB, which are relatively high. These three structures of antennas are suitable for communication systems working in C wave band.
In this paper in order to reduce the size and improve the performance of microwave filter, novel single and dual band matched band-stop filters are developed. A stepped impedance dual mode resonator is used, resulting in a much more compact size, compared to the conventional dual mode ring resonator that has an electrical length of 360˚. The proposed prototype is able to achieve high stop band attenuation even with low Q factor values. Moreover, for the short electrical length of this filter, the first spurious resonance occurs at 4.7 times the fundamental resonance frequency. Therefore, the proposed technique selectively removes only the fundamental resonance frequency when such a resonator is implemented. A theoretical analysis, along with an experimental prototype is proposed in order to demonstrate the feasibility of these proposed networks.
A procedure based on the analytical model of a lumpedelement, crossover circulator has been developed to maximize its operating bandwidth. The procedure considers the circulator as a network and employs the circulation impedance - the load associated with perfect circulation - as a metric to optimize the bandwidth. Using this procedure, we find that a maximum 194% bandwidth can be obtained for an ideal circulator for any above-FMR range operation. By applying this same procedure to an actual circulator device in 225-400 MHz frequency range, we achieve a 125% bandwidth from a numerical simulation model. We have verified this result from the measurement of a fabricated device; the measured data reveals a bandwidth of 129%.
In this letter, a novel compact tri-band bandpass filter (BPF) with high selectivity is presented. The proposed tri-band performance measure is realized by using eight sets of resonators, i.e., two- and three-section stepped impedance resonators (SIRs). The three-section SIR is designed for determining the three passbands and providing the electric coupling, while the two-section SIR is used for determining each passband respectively and providing the magnetic coupling. Then, coupling structures with two transmission zeros near each passband edge are presented, therefore, the band selectivity of the filter is much improved. The three passband frequencies could be independently designed and tuned. This novel tri-band BPF is fabricated and the measured results are in good agreement with the full-wave simulation results.
In this paper, a planar coupled-fed monopole antenna with eight-band LTE/WWAN (LTE700/2300/2500/GSM850/900/1800/1900/UMTS) operation for mobile handset device application is proposed. It simply consists of a T-shaped driven strip and a coupled radiating structure, which occupy a small PCB area of 50(L)x15(W) mm2. This antenna, which is printed on a 0.4 mm FR4 substrate and fed by a 50-Ω coaxial cable, can provide two wide operating bandwidths covering 697-1012 MHz and 1598-2795 MHz for LTE/WWAN communication systems. A prototype of the proposed antenna is fabricated, tested and analyzed. From the measurement results, nearly omnidirectional coverage and stable gain variation across the desired LTE/WWAN bands can be obtained with the antenna.
This article presents an efficient method for characterization of substrate integrated passive circuits. The analysis is based on the wave concept formulation and the iterative resolution of a system of two equations between incident and re ected waves. Simulations obtained are compared with analytical references and HFSS simulations. A good agreement is achieved with computation time saving.
In this paper, a full-wave analysis technique of lossy substrate integrated waveguides, based on the dyadic Green's function of the parallel plate waveguide, is presented. The field inside the waveguide is expressed in terms of cylindrical vector wave-functions and the finite conductivity of the top and of the bottom plates, and of the metallic vias are taken into account. Losses into the dielectric substrate are also included. Coaxial ports are considered as sources and self and mutual admittances are evaluated. Cases of practical structure taken from literature are presented showing a very good agreement with the most used commercial software.
According to the intracellular electromanipulation model, bacteria can be killed at as high as 106 V/m electrical fields on microwave band. We designed and constructed a modified microwave coaxial cavity resonator for liquid sterilization. The cavity could concentrate the field on a very small area, and the liquid can pass it in milliseconds. The bacteria can be killed by the very high field, but with a slight temperature increase. The designed resonator is simulated and analyzed by the electromagnetic simulation code, the results indicated that when the input power reaches 100 W, the electric field on the area of liquid can reach 106 V/m. Preliminary experimental results indicated that when the input power was 100W, the bactericidal rate was > 90%, and the temperature of the liquid only increased 8.6°C.
In this paper, a compact near field reader antenna is proposed for ultra-high frequency (UHF) radio frequency identification (RFID) applications. The antenna structure is composed of two split-ring-resonators (SRRs) and miniaturized to a special small size of 25 * 25 * 1:6mm³. The measured bandwidth of antenna prototype is 13 MHz (914.5-927.5 MHz) with reflection coefficient less than -10 dB, which covers the China RFID band II (920-925 MHz). Simulation shows that the proposed antenna achieves a strong and uniform magnetic field distribution in the near field region, and the reading range is up to 42 mm with near field RFID tag. Through modifying the parameters of SRRs, the antenna can operate on different UHF RFID bands (Europe band, China band I&II etc.).
The design of a fully planar microstrip crossover for beamforming networks is presented. The design starts by using a conventional half-wavelength square patch and two sets of orthogonal feeding lines. Rectangular and circular slots are introduced on the square patch in order to reduce the required area of the patch by 82%. The proposed crossover is fabricated and tested for performance confirmation. The measured data shows less than 1 dB insertion loss, more than 13 dB isolation, and around 0.1 ns deviation in the group delay across 12% fractional bandwidth. The proposed crossover is suitable for planar Butler matrix which is a key component in beamforming networks.
This paper presents a design procedure for the generation of circular polarization (CP) from the composite right/left handed (CRLH) transmission line-(TL) with a coupled inter-digit structure and an inductive stub. The Ex and Ey components are generated from the parallel stubs and the fingers, respectively. The 90°-phase difference can be obtained by optimizing the dimension of the unit cell. In addition, the suitable amplitude ratio of |Ex| and |Ey| for CP generation is obtained by selecting a suitable position of the CRLH-TL between both edges of the ground. As a result, a CP with a measured bandwidth of 30.5% for an axial ratio (AR) of < 3 dB in the boresight direction is obtained. Using the behavior in both the left-handed (LH) and right-handed (RH) frequency regions, a scanning angle of the main beam of approximately 30° can be obtained by varying the frequency between 2.58 GHz and 2.99 GHz. Furthremore, the principle of CP generation is discussed.
In this paper the concept of static electric permittivity and its measurement are discussed. A classical description of polarization via a harmonically bound charge model is revisited and the evolution of the polarization concept in the presence of free electrons is shown. Various electrostatic problems are defined under ideal conditions. The measurement procedures for characterizing the static permittivity of dielectrics and conductors via the measurement of induction-electric field, charge-potential difference and electrostatic energy variation are discussed. Two basic experiments with a lossy dielectric are described. In one case we reach an electrostatic equilibrium with an indeterminate solution. In the other case we define a magnetostatic problem. Finally, we comment on the case of a laboratory experiment remarking on the proper use of the low-frequency limit of dielectric constant and showing experimental results performed on a supercapacitor.
A novel radar energy control strategy based on an improved Interacting Multiple Model Particle Filter (IMMPF) tracking method is presented in this paper. Firstly, the IMMPF tracking method is improved by increasing the weight of the particle which is close to the system state and updating the model probability of every particle. Based on this improved IMMPF method, an energy control method for Low Probability of Intercept (LPI) is then presented, which controls the emission time and power of radar according to the target's range and radar cross section (RCS), under the condition of constant detection probability. The tracking accuracy and LPI performance are demonstrated in the Monte Carlo simulations. The results are validated through the comparisons with other methods.
A novel Koch fractal printed Yagi-Uda antenna fed by coplanar waveguide (CPW) is proposed and analyzed. The antenna has first-order Koch fractal monopoles, and the monopoles' ground plane acts as the ground plane of the antenna. The radiation characteristics of the antenna are simulated by CST Microwave Studio® and explained by the simulated results. The antenna's currents distribution becomes more uniform after being fractal, which is conducive to increasing antenna's radiation directivity. The proposed Koch fractal Yagi-Uda antenna has an operating band of 885-913 MHz (relative bandwidth 3.1%) with the center frequency of 900 MHz. The total antenna size is 171 mm×85 mm (0.51λ×0.25λ) and the length in the antenna's polarization direction is only 25% of the wavelength corresponding to the center frequency. Compared to traditional Yagi-Uda antenna, the proposed antenna can achieve a 50% miniaturization effect.
A novel design concept of a compact printable orientation independent chipless RFID tag is presented. The tag consists of a circular patch loaded with multiple slot ring resonators. This symmetric frequency domain based tag has the advantage to be read from any orientation with the reader antennas. The tag can be read in close proximity by chipless RFID tag reader with waveguide(s) and also can be read in both near field and far-field of the RFID tag reader with antennas. This tag does not have a ground plane and has higher data density compared to the existing printable chipless tags. The usability of this single sided tag in close proximity is verified by waveguide measurements for both proximity applications such as on ID access cards, item level tagging etc. and slot reading application such as on banknotes, credit cards etc.
The paper deals with the modelling, practical implementation and characterization of a directional antenna controllable through 360° in the [2-2.5 GHz] frequency band. The antenna is composed of a central omnidirectional broadband monopole feed surrounded by a metamaterial made of one or two controllable layers of metallic strips printed on a dielectric substrate, which can be electrically continuous or discontinuous. Following the electrical state of these strips, the metamaterial can be reflective or transparent. Then by controlling the distribution of reflective and transparent regions of the latter metamaterial around the central feed, a directional emission having an angular beamwidth lower or equal to 60° and controllable through 360° is produced in the UMTS and WIFI frequency bands, demonstrating the wideband operation of this antenna.
A novel fourth-order half-mode substrate integrated waveguide (HMSIW) filter with dual-mode microstrip resonator is presented. The dual-mode resonator is etched on the top metal layer of HMSIW cavity, so the size can be reduced greatly. The filter has compact size and wide stopband in comparison with conventional SIW filters. Microstrip resonators and cavity resonators are integrated in one filter to achieve the goal of smaller size and better performance. Two filter samples are designed and fabricated, with good agreement between the measured and the simulated S-parameters.
The aim of this study is to address the management of urinary problems by detecting changes in the volume of urine within the human bladder using low cost, low power, wearable Ultra Wideband (UWB) sensors and signal processing techniques. The paper describes experiments on the classication of six three-layer dielectrically representative bladder phantoms, mimicking a range of muscle and bladder wall-to-wall distances. The process involves the illumination of the bladder with a UWB pulse. Due to the dielectric contrast between urine and bladder wall tissue at microwave frequencies, an electromagnetic reection is generated at both the anterior and posterior bladder wall. These reflections are recorded, the salient features are extracted and processed by a classification algorithm to estimate the volume of urine present in the bladder. To evaluate the prototype system, a number of physical bladder phantoms were constructed, each mimicking bladders of different volumes. Principal Component Analysis (PCA) was applied and the processed features were classified by a k-nearest neighbour learning algorithm to estimate the state of the bladder (small, medium or full). The paper describes the bladder phantom prototype systems and the experimental setup. Results illustrate detection of phantom bladder states with an accuracy of up to 91%.
This paper proposes a rectifying antenna (rectenna) for operation in the ISM (Industrial, Scientific and Medical) band centered at 2.45 GHz. It consists of a modified circular monopole loaded with a rectangular ring and a half-wave rectifier. Numerical and experimental data are reported and discussed. From measurements, it is demonstrated that, when the power density incident on the monopole is 155 μW/cm², the device here presented exhibits values of the RF-to-DC conversion efficiency higher than 30 % in the frequency range 2.35-2.5 GHz with a maximum of about 50 % at 2.45 GHz.