Vol. 71

A new microstrip lowpass filter using radial stub loaded resonators is presented. A microstrip high impedance main transmission line loaded with five radial stub loaded resonators by five high impendence transmission lines is introduced in the design of the filter. Owing to the introduction of the radial stub structure, the filter achieves compact size and ultra-wide stopband. A demonstration filter with 3 dB cutoff frequency at 0.8 GHz has been designed, fabricated and measured. Results indicate that the proposed filter is able to suppress the 17th harmonic response referred to a suppression degree of 15 dB, together with a small size of 0.060λ_g×0.080λ_g, where λ_g is the guided wavelength at 0.8 GHz.

A low-profile and broadband slot antenna with artificial magnetic conductor (AMC) surface is designed for X and Ku communications. Loaded with evolved C-shaped branches, the proposed coplanar waveguide (CPW)-fed slot antenna, which consists of two radiating slots, exhibits wide impedance frequency band performance. The presented AMC, the unit cell of which is made up of two central hexagonal circles with six rectangle branches, operates in a wide in-phase reflection frequency band ranging from 6.0 to 13.94 GHz (79.64%) at the reference plane 4 mm above the AMC surface. An AMC surface composed of 8×10 AMC unit cells is located under the slot antenna with a distance of approximately 0.107λ (λ denotes the free-space wavelength at 8.0 GHz), which improves the radiation and impedance match properties of the broadband slot antenna while maintaining low profile. A prototype of the proposed slot antenna with AMC surface is fabricated and measured. Measured results show that the composite antenna achieves a wide impedance bandwidth from 7.64 to 14.58 GHz (62.47%). The measured peak gain is up to 10.26 dBi, and the maximum cross-polarization level is -17.5 dB for both E and H planes. Good agreements between the measured and simulated results validate good performance of the presented slot antenna within the desired frequency band.

A small-sized loop antenna loaded with the series-connected capacitor and inductor for wireless local area network (WLAN) operation is proposed. The main radiator of an L-shaped, loop structure and its small ground were constructed on a single-layered FR4 substrate of thickness 0.8 mm and occupied a miniature size of 5 mm × 20 mm only. It was found that by loading the series-connected capacitor and inductor between the antenna feed port and the loop radiator, the quarter-wavelength loop resonance can be easily excited together with the controllable half-wavelength resonance. The design prototype was able to operate in the 2.4-GHz (2400-2484 MHz) and 5.8-GHz (5725-5825 MHz) WLAN bands. The proposed antenna was simple in structure and yet provided dual-band operation and good radiation performance.

This paper proposes a harmonic efficiency selectivity circuit (HESC) for achieving a broadband Class-J/F^-1 continuum mode power amplifier (PA) with enhanced efficiency. Design equations are derived through continuum mode condition analysis and are used in implementing the HESC. The implemented HESC topology is then used in attaining the broadband Class-J/F^-1 continuum mode PA. A theoretical parameter termed harmonic-alpha (ρ^h) acting as a sub-unit structure in HESC is introduced. Considering harmonic losses, ρ^h possesses a lookup table containing information on the harmonics. ρ^h operates in unison with the HESC in selecting the suitable harmonics with the best efficiencies. With ρ^h, the relationship among the HESC, the optimal impedance at the device's drain, and the terminal load impedance is defined for a greater freedom of harmonic impedance solutions space, efficiency improvement, and bandwidth extension, thus, indicating an increased flexibility in the design of broadband continuum mode PAs. This method is validated with a realized PA prototype operating from 1.3 to 2.4 GHz corresponding to a fractional bandwidth of 59.5%. The experimental results under continuous wave signals indicate that 79% peak efficiency, 42.68 dBm peak output power, and 16.96 dB peak gain are recorded. Moreover, at 1.7 GHz, when being tested with modulated signals at an average output power of 34.83 dBm, the lower and higher adjacent channel power ratios (ACPRs) without digital predistortion (DPD) are -34.9 dBc and -33.9 dBc, respectively, and a drain effifficiency (DE) of 45% is recorded. With DPD, -50.8 dBc and -50.3 dBc are respectively obtained at lower and higher ACPRs at an average output power of 34.6 dBm, and a DE of 44% is achieved.

Wireless communication is very valuable in underground mines, in which channel characterization plays an important role. In this paper, both narrowband and wideband measurements at three typical ultra-high frequencies of 433, 900 and 2400 MHz in a real mine shaft are performed. To our knowledge, this is the first work focusing on radio propagation in the mine shaft environment. Important channel characteristics, such as the path loss, delay spread and the number of multipath components were extracted from the measured data and compared with that in tunnel channels. The effects of frequency and antenna position on the path loss were investigated. The relationship between the root-mean-square (RMS) delay spread and the transmitter-receiver distance was also analyzed. The results will deepen our understanding of the mine shaft channel and help to design shaft wireless systems.

The standard expression for the magnetic interaction energy used in the study of the Aharonov-Bohm effect is investigated. We calculate the magnetic interaction energy between a point charge and an infinite solenoid from first principles. Two alternative expressions are used: the scalar products of the currents with the vector potentials and the scalar product of the magnetic fields. The alternatives are seen to agree. The latter approach also involves taking into account surface integrals at infinity, which are shown to be zero. Our model problem indicates no classical Aharonov-Bohm effect, but we also discuss the normally neglected fact of energy non-conservation. The problem is treated from the point of view of Lagrangian and Hamiltonian mechanics.

This paper aims to study the synthesis of negative magnetic permeability and how this leads into some physical phenomena such as the appearance of backward waves and the propagation below cutoff. The extraction of the polarizability tensors of the edge coupled split ring resonator is derived, and the existence of bianisotropic effects of this case is investigated. It is shown how to avoid the bianisotropic effects through using a proposed design. inally, the backward wave of the proposed design with lower losses than the edge coupled split ring resonator is shown by simulation.

A low profile dual-band passive Ultra High Frequency Radio Frequency Identification (UHF RFID) tag antenna designed to operate at two RFID bands allocated for use in Europe (865-868 MHz) and Japan (950-956 MHz) is proposed. The antenna has two eccentric circular rings of different radii to provide dual band response. An arc-shaped strip with Impinj Monza-4 IC chip is used to feed the two rings simultaneously by microstrip-line coupling-feed technique. The proposed design is simulated using Ansoft HFSS, and the prototype is fabricated. The return losses at 866 MHz and 952 MHz are measured to be -12.25 dB and -12.99 dB, respectively, which are in good agreement with the simulated results. The proposed antenna exhibits a 10 dB bandwidth of 9 MHz from 862 to 870 MHz and an 8 MHz 10 dB bandwidth from 949 to 956 MHz covering the UHF RFID bands in Europe and Japan. The maximum read ranges are measured to be around 3 m in the 865-868 MHz band and 2.6 m in the 950-956 MHz band.

Space-time antijamming problems cause widespread concern recently in global navigation satellite system. Space-time adaptive procession (STAP) is an effective method to suppress interference signals, which contains two adaptive filters, i.e., spatial filter and temporal filter, and the array pattern can be automatically optimized by adjusting the weights obtained from a prescribed objective function. However, mismatch may occur between adaptive weights and data, due to the change of the interference location when receiver is shaking. In this case, the performance of STAP will degrade dramatically. To solve this problem, an effective nulling widen method based on uniform circular array (named as UCA-NW algorithm) is proposed for space-time antijamming. Through this method, an extension matrix is given to modify the covariance matrix and the formed null can be broadened from azimuth angle and pitch angle, respectively. Thus, this algorithm can suppress interference signals effectively when the receiver is shaking, and the width of nulls can be controlled easily. Simulation results are presented to verify the feasibility and effectiveness of the proposed algorithm.

A metamaterial sensor is designed in this paper which can be used to detect the refractive index of an unknown dielectric loaded on the top surface of a metamaterial absorber. The resonant frequency of the absorber will be changed with various refractive indexes of the loaded dielectrics. Especially, the resonant frequency of the sensor is uniquely related to the refractive index of the unknown dielectric with the constant thickness, the linear relation of which is obtained by simulation fitting. A prototype of the absorber is manufactured and measured, which testify the design theory and simulation results. The S_fre of the proposed sensor is 0.3537GHz/RIU, and the FoM can reach 11.0531RIU^-1.

This paper presents the design and demonstration of an optimized land grid array (LGA) structure for low noise amplifier (LNA). In order to achieve better circuit performance, the novel chip-package co-design method based on embedded inductors is used. The optimized structure is accurately modeled by ANSYS software. S-parameter is utilized to help in understanding the contributing to the optimized LGA structure. The simulation results for the novel LNA co-design structure show the gain 14.35 dB (> 10 dB), input reflection coefficient -15.63 dB (< -10 dB), output reflection coefficient -24.43 dB (< -10 dB), reverse-isolation -44.7 dB (< -20 dB), and noise figure 2.99 dB (< 4 dB), and indicate that the optimized LGA structure based on embedded inductors is fully capable of supporting 5.8 GHz LNA application.

T matrix characterizes the scattering property of a single PEC object and does not depend on the incidence. In this work, we propose a method to derive a reduced-order T matrix for a single 3D PEC object with arbitrary shape. The method is based on the vector addition theorem and the conventional EFIE, MFIE or CFIE methods. Given the T matrix for a PEC object, the scattered fields can be directly calculated from any incidence. For multiple objects, a matrix equation system is built based on the T-matrix and the position of each object. Finally, numerical examples show the accuracy and efficiency for solving the scattering of both spherical and non-spherical arrays. Compared to the moment methods, the computational cost of solving the final matrix equation is reduced by several orders of magnitude.

In this paper the design and implementation of a patch antenna array using Dolph Chebyshev current distribution operating in C-Band is demonstrated. The proposed novel omnidirectional triangular patch antenna array is a nonuniform array type with equal or uniform spacing between the antenna elements, but having the nonuniform amplitude excitation with Dolph-Chebyshev current distribution. Dolph-Chebyshev amplitude excitation suppresses the side lobes as well as the designed antenna works like an omnidirectional antenna. The proposed antenna array has a gain of 0.52 dB and return loss of -35.0649 dB which works as an omnidirectional antenna. This proposed antenna is suitable for C-band applications such as Wi-Fi devices, cordless phones, and keyless entry systems.

A novel method to determine the transfer functions of power line networks is presented. Although a number of the evaluation methods have been proposed, the major drawbacks are on approximation, complexity and intuitiveness. The presented method overcomes those by making use of backward impedance transfer and forward voltage transfer techniques. Additionally, the novel method offers an extra feature that transfer functions at any points throughout the network can be simultaneously determined in one implementation. This paper first reviews some major existing methods. Then, the method of impedance and voltage transferring is derived and fulfilled with an implementation algorithm and mathematic description. Lastly, an implementation of the method on a sample network for the transfer function is demonstrated. Channel capacity is adopted as the measure for the quality of the channels.

In this paper a waveguide is introduced as an absorbing modulator using GaN/AlN structure based on spherical quantum dots. The role of waveguide (modulator) dimensions on optical profile of light in the channel and coupling efficiency is also investigated. These parameters can affect the main characteristics of modulator like absorption and depth of modulation. First we will give a brief explanation about the all optical modulator structure based on spherical quantum dots and its optical properties. Then the electrical fields in optical fiber and modulator will be introduced, and the effects of dimensions on these fields will be discussed. The results show that the electric field distribution determines the insertion loss and also effects on modulation. Finally we will determine the proper dimensions of modulator for coupling to optical fiber.

By analyzing the characteristics of the super low frequency (SLF) electromagnetic wave in through the earth (TTE) communication, an orthogonal array of magnetic antenna is proposed for receiving SLF signal, and a new robust adaptive beamformer is used to process the received signals. The proposed beamformer is a multi-input generalized sidelobe canceller (GSC) with a coefficient constrained adaptive blocking matrix and a filter based on minimum mean-square error (MMSE) criterion. It can reduce the leakage of the desired signal and enhance the capability of interference cancellation. The received signals of the main antennas and the reference antennas of the antenna array are input to the beamformer as desired signal and reference signal, respectively. Both simulated and experimental results show that the proposed beamformer can suppress the single-tone and phase modulation interference, whose frequency is close to the desired signal's frequency. The proposed beamformer has better effect and robustness on interference cancellation than the traditional GSC.

In order to effectively improve the communication quality in the extremely-low frequency (ELF) communication, a whole model of analog circuits and transform domain algorithm is constructed. Analog circuits include a pair of magnetic antennas, an amplifier and a group of filters. The distributed capacitance of the magnetic antenna is effectively reduced by the segmented winding method. Analog circuits used to amplify and filter received signal are designed. Besides, a magnetic sensor with high sensitivity is produced. The Karhunen Loève transform (KLT) algorithm applied to the field of interference suppression is deduced in detail. The transform successfully passes the received signal along the basis vector in sub-band, but the interference signal along the vector is attenuated. Therefore, the problem of the optimal filter converted into the solution of transform factor for each sub-band. Then the relationship between the KLT transform and the time domain algorithm in the interference suppression problem is given. Based on the KLT algorithm, Fourier transform (FT) that makes the correlation matrices of the received signal diagonalized approximately is applied to the interference suppression algorithm. Based on the deduction results, the final optimal filter expressions are basically the same as the KLT algorithm. Finally, the experiments are carried out by using the simulated signal and real collected data in the laboratory, respectively. The schematic diagram of the real collected device is presented. The experimental result shows that, no matter the analog signal or the real collected data, the proposed algorithm can effectively suppress the interference. For the simulation, the performance of KLT algorithm is basically same as that of FT algorithm, but KLT algorithm is obviously better than FT algorithm for real collected data.

In this paper, based on different saliency ratios ρ, three interior permanent magnet (IPM) synchronous machines respectively owning a large ρ, a low ρ and an inverse ρ are proposed for the potential applications of electrical vehicles (EVs). To grasp the impacts of saliency ratio on machine performances, comparative studies are conducted at low speed operation (constant torque region) and high speed operation (constant power region), respectively. In particular, the overload capability referring to magnet demagnetization is emphasized in low-speed heavy-duty operation region. And in high speed, the constant power speed range (CPSR) and high efficiency range are investigated. The main results put in evidence the different behaviors of the three machines in terms of EVs operating conditions. Though all three machines reveal considerable behaviors in CPSR, the inverse saliency ratio machine shows a larger high efficiency region and extends the high efficiency region to a wider speed-and-torque range due to its unique characteristic of L_q<Ld.

Effects of a superstrate layer on the resonant frequency and bandwidth of a high T_c superconducting (HTS) circular printed patch are investigated in this paper. For that, a rigorous full-wave spectral analysis of superconducting patch in multilayer configuration is described. In such an approach, the spectral dyadic Green's function which relates the tangential electric field and currents at various conductor planes should be determined. Integral equations are solved by a Galerkin's moment method procedure, and the complex resonance frequencies are studied with basis functions involving Chebyshev polynomials in conjunction with the complex resistive boundary condition. To include the superconductivity of the disc, its complex surface impedance is determined by using London's equation and the model of Gorter and Casimir. Numerical results are compared with experimental results of literature as well as with the most recent published calculations using different methods. A very good agreement is obtained. Finally, superstrate loading effects are presented and discussed showing interesting enhancement on the resonant characteristics of the superconducting antenna using combinations of Chebyshev polynomials as set of basis functions.

In some cases, such as at a boiler tank and other large-size mechanical systems, it is more realistic to employ a non-contacting sensor to detect small displacement or vibration. In this paper, a non-contacting sensor for monitoring small displacement or vibration based on measurement of antenna reflection coefficient is proposed. A theoretical and numerical study is performed to investigate the proposed method and to determine the post processing method associated with the antenna reflection coefficient data. To avoid the ambiguity in the measured data, the detection of both the magnitude and phase components of the antenna reflection coefficient is required to compute the small displacement of the target. The distance between antenna and target has to be determined in order to minimize the ambiguity range in the data. The frequency domain observation is more appropriate for determining the amplitude and frequency of the target vibration. Magnitude detection, phase detection and Fourier analysis are used as main tools in the post-processing part of the proposed method.