In this paper, band pass filters based on the microstrip configuration and utilizing coupled defected ground structures are presented. The 50 Ω microstrip line has a gap discontinuity in the middle and characterized by stepped impedance resonators on either half. The four fractal geometries tested for defected ground are the first and second iterations of the modified Moore curve, the closed staircase curve and a dual concentric closed staircase curve. The filters have a compact size and planar geometry. The modified Moore first iteration has a measured pass band from 2.27 GHz to 11.86 GHz, whereas the second iteration has a measured pass band from 1.85 GHz to 6.71 GHz. The measured pass band of the closed staircase is from 2.38 GHz to 7.21 GHz. The dual-concentric closed-staircase DGS filter offers a dual-band response with the measured pass band being from 2.41 GHz to 5.01 GHz and from 5.81 GHz to 8.35 GHz. All the filters are intended for UWB applications. A parametric study for the controlling parameters is also presented.

A passive millimeter-wave imager BHU-2D-U has been developed by Beihang University. This imager is designed for detecting concealed weapons on human body. It is a subsequent model of BHU-2D, which is also developed by the same group. In this paper, the improvements of BHU-2D-U over BHU-2D are introduced. Firstly, BHU-2D-U is used for whole body scan, which is different from BHU-2D. Thus, the field of view (FOV) of the new imager is enlarged and a new antenna array type is adopted. Secondly, the enlarged FOV requires smaller antenna spacing and compact receiver arrays. In order to reduce the volume of the receivers, I/Q demodulators operating in double side band mode are adopted because it does not need the image-reject filter, which is usually a bulky one. Thirdly, the quantity of the correlators increases because the number of receiving elements is doubled. To cope with the increase of the correlator quantity, a multiplexing technique is used in the FPGA internal layout of the correlator array unit. After a brief introduction, the system design and configuration is illustrated in detail. Finally, imaging experiments on a person with concealed weapon are conducted, by which the design and image reconstruction algorithms are verified. To conclude, initial results of BHU-2D-U have proved that the improvements are effective.

The one-step stair-shaped dielectric resonator antennas (DRAs)with a circular cross-section are studied theoretically and experimentally in this paper. The reasons why the one-step stair-shaped DRA shave a wideband performance have been investigated. It is shown in this paper that the modes excited in the one-step stair-shaped DRA with circular cross-section can be regarded as pseudo HEM₁₁₁ and pseudo HEM₁₁₃ modes. The pseudo HEM₁₁₁/ HEM₁₁₃ mode exhibits similar radiation patterns but a different resonant frequency and radiation Q factor to the HEM₁₁₁/ HEM₁₁₃ mode of the cylindrical DRA. By properly choosing the dimensions of the one-step stair-shaped DRA, the two modes can be used to obtain a wideband antenna.

A mathematical investigation of a normal mode helical antenna (NMHA) is presented to provide an equivalent model. The vector potential of a single-turn NMHA using a developed helix line is first derived. To avoid complexity in the vector potential, a useful relationship between the source point and the helix line is established. Employing this relationship, the integral of the vector potential can be calculated as that of a linear current antenna, and the result leads to an equivalent model that is a combination of the electric dipole and the magnetic dipole, i.e., exactly the same as assumed in previous work. A helix line of several turns can be regarded as a combination of the turns. Thus a general NMHA can be analysed as the sum of the vector potentials of the turns in the helix. To verify the obtained formulas, the calculated radiation characteristics are compared with the results of the commercial simulation, showing good agreement.

Two magnetless double-rotor (DR) dual-mode machines, namely the DR DCexcited multi-tooth switched reluctance (DR-DC-MSR) machine and the DR flux-switching DC (DR-FS-DC) machine, are proposed for special direct-drive applications where two rotating bodies are required to operate independently. Both machines can offer two different operation modes, namely the doubly-salient DC (DSDC) mode and MSR mode, normal and fault-tolerant operations, respectively. With the independent armature windings, both machines are able to couple their two rotors with two rotating bodies operating at various speeds. The proposed machines are designed and analyzed by using the time-stepping finite element method (TS-FEM). The simulation results confirm the validity of the proposed machines.

In this paper, a novel self-complementary shaped multiple-L slot loaded suspended microstrip patch antenna stacked with a polycrystalline silicon (poly-Si) solar cell is presented for 2.4/5.2 GHz band WLAN and 2.5/3.3/5.8 GHz band WiMAX networks. While the proposed self-complementary shaped multiple-L slot loaded suspended patch enables the propagation of multiple TMmn modes to be present, the poly-Si solar cell works as an RF parasitic patch element in addition to its photovoltaic function. The proposed stacked solar antenna combination topology enables the radiating patch to be easily modified by slot-loading to achieve multiband resonance characteristics and the poly-Si solar cell to operate without being shaded by any RF components of the antenna ensuring an optimum solar operation performance.

A novel compact planar triple-band bandpass filter using two sets of short stub-loaded stepped impedance resonators (SSLSIRs) and a pair of embedded stepped impedance resonators (ESIRs) has been proposed. The SSLSIRs can adjust the bandwidths of the corresponding passbands over a wide range, and the ESIRs employing non 0° -feed coupled structure with mixed electric and magnetic coupling can obtain an extra transmission zero. The embedded resonators structure can further miniaturize the dimensions of the whole triple-band filter. The operating frequencies of the SSLSIRs and ESIRs are designed for the applications of the WLAN (2.45/5.2 GHz) and WiMAX (3.5 GHz) systems, respectively. The simulated and measured results are both presented and show good agreement.

A pyramidal horn monopulse array is proposed for working at Ka-band with circular polarization (CP) characteristic. The array is composed of 28 elements with a 28-way waveguide power divider network. The element has a pyramidal horn with a rectangular waveguide, which is placed downside the horn. And a 45° inclined slot cut in the wide wall of the rectangular waveguide. The inclined slot can convert the excitation into two orthogonal modes (TE₁₀ and TE₀₁) with equal amplitude, and 90° out of phase is produced due to different propagation constants of the two modes in the pyramidal horn. Therefore, the antenna can achieve CP by using a compact structure without polarizer. This paper also provides procedure of the compact power divider network for synthesizing monopulse pattern. This monopulse array has excellent performance: The simulated and measured reflection coefficients of the sum port and the difference port of the array are below -15 dB, the side lobe level of array less than -27 dB, and axial ratio <3 dB in the mainlobe beamwidth. The simulated and measured results are in good agreement.

This paper proposes a novel double-winding flux modulated permanent magnet machine (FMPM) for stand-alone wind power generation. Based on the flux-modulating effect, a concentrated winding set and a distributed winding set can be artfully equipped on one stator component. This makes the proposed machine possessing much simpler structure than traditional double-winding double-stator PM machines. Comparative study shows that the proposed FMPM can offer higher torque capability and stronger flux adjustability than the existing single-winding FMPMs.

An omnidirectional dual-polarized slot antenna with high port isolation for 2.4-GHz wireless local area network (WLAN) applications is proposed in this paper. The omnidirectional radiation patterns of the vertical polarization (VP) and horizontal polarization (HP) are achieved by individually cutting two orthogonal slots onto the metal walls of a cuboid antenna. The overall volume of the compact antenna is only 60 × 10 × 10 mm³ (0.488λ₀ × 0.081λ₀ × 0.081λ₀ ). A prototype of the designed antenna is manufactured and tested. Both simulated and measured results show that the -10 dB impedance bandwidths of dual polarizations cover the desired band of 2.4-2.484 GHz and the port isolation, in the operating frequency, is less than -35 dB. Stable measured gains are greater than 2.75 and 1.35 dBi for the VP and HP, respectively.

The application of an external electric field has been shown to enhance the impregnation of resin monomers used in restorative dentistry. Further to experimental investigations that have related the migration of monomers to their electrical properties, additional insight into the conduction mechanism within the tooth can be gained by numerical modelling of the current conduction through the tooth. This paper presents the development of a three-dimensional realistic voxel model of a human tooth from a data set of digital images and the computation of the currents in the dental tissues by means of a low-frequency numerical code (scalar potential finite difference). Results for the electric potential and current density magnitude in various cross sections of the tooth model are presented for an applied 10 V dc voltage between the electrodes.

A simple compact wideband aperture coupled rectangular dielectric resonator antenna (RDRA) loaded with similar parasitic dielectric elements separated by low dielectric spacers as air gap layers is designed. The bandwidths of the proposed RDRAs are significantly enhanced as compared with the bandwidth of the driven DRA without an air gap. The measurement results are verified experimentally for a one parasitic element case. A bandwidth of 18% and 27% with VSWR better than 2 is achieved for double and triple gaps, respectively. It is interesting to point out that radiation patterns are stable in the entire operation band.

This paper presents a circularly polarized compact antenna based on the concept of Yagi-Uda antenna. By properly arranging three ring resonators operating at the fundamental mode, a compact Yagi-Uda like antenna is proposed to form directional pattern. This proposed antenna has comparable size with the ring resonator of quarter-wavelength, while the performances are comparable with the conventional microstrip antenna of half-wavelength. To validate the proposed design methodology, an antenna working at UHF radio-frequency identification (RFID) band is benchmarked. Both simulated and measured results are shown for comparison.

In this paper, a wide bandwidth and wide dynamic range AGC amplifier is presented. A push-pull variable gain amplifier (VGA) structure is proposed for wide dynamic rang. Moreover the bandwidth enhancement technique is used in the post amplifier design to ensure the wide bandwidth and gain of whole circuit. The experimental results demonstrate that the proposed AGC amplifier that is fabricated in 0.13 μm SiGe BiCMOS process, achieves a 23-GHz bandwidth and 36-dB dynamic rang among the recently published AGC amplifiers, whereas the power and area consumption are 57.6 mW and 1.9 mm², respectively.

A great deal of researches have so far been conducted on the analysis of eccentricity in induction machines. However, they mostly consider radial non-uniformity and neglect nonuniformity in the axial direction, but in practice, the axial non-uniformity due to rotor misalignment faults is quite common. This paper presents a modified model of a three-phase squirrel cage induction machine under different rotor misalignment conditions. For this purpose, general expressions for air gap and mean radius of induction machine, considering axial non-uniformity, have been developed. The proposed model is able to calculate the time varying inductances versus rotor angle for three-phase squirrel cage induction machines under general rotor misalignment, including static, dynamic and mixed rotor misalignment in the frame of a single program. Simulation results were verified by the experimental ones.

A compact decoupling network for enhancing the ports isolation of two coupled antennas is proposed in this letter. Parallel coupled lines (PCLs) and transmission lines (TLs) with different electrical lengths are considered to control the magnitude and phase of this decoupling network, respectively. The coupling coefficient of the PCLs is adjusted with various line widths and coupled gaps so that the magnitude of this network will be equal to that of the coupled antennas. And the electrical length of the series TLs can be controlled to make the signals of coupled antennas and decoupling network out of phase. Thus, the mutual coupling between the coupled antennas can be canceled. A prototype is fabricated on a RO4003 print circuit board (PCB) for demonstration. The measured results agree quiet well with the simulation ones. High antenna isolation and good matching are simultaneously achieved at the center frequency, i.e., 925 MHz for global system mobile communications (GSM) which shows the compact decoupling network is suitable for reducing the isolation of size limited multi-antenna systems.

Based on technical analysis and budget link experimentation, the main purpose here is to show improvement of HF half loop antennas in terms of signal-to-noise ratio (SNR) and stealthy for a combat ship. A special designed HF antenna brings a high quality communication over 1000 NM. A suitable integration of a HF half loop antenna at ship corners contributes to the ship stealthy. This paper shows the antenna performance and the benefit of the completely body integrated HF half loop antenna regarding whip antennas. The corresponding SNR is 15 to 20 dB better than for a conventional antenna.

A highly sensitive, passive relative humidity (RH) sensor using polyvinyl-alcohol (PVA) dielectric film is presented. For the first time, PVA is investigated in microwave RF sensing devices for low cost, high resolution and accurate chipless RH sensor realization. Comparative study with traditional humidity sensing Kapton polymer is presented to validate superior performance of PVA film. Results are presented for two different passive high Q resonators to validate sensing performance in wide applications. Moreover, a new sensing parameter is described to investigate sensitivity measurement through resonance frequency and Q factor variation. The RH sensor has the potential to be integrated with mm and μm-wave high frequency passive RFID for ubiquitous sensing.

Constrained Least Mean Square (CLMS) algorithm is used to adapt the antenna array weights. CLMS in its simple form fails to capture the Signal of Interest (SOI) if there is an error in the Direction of Arrival (DOA) estimation. Moreover, it will consider the SOI as an interferer and create null in the desired DOA. The large gain will be towards the detected wrong direction. Derivative constraints and Bayesian beamformer are two techniques used to overcome such a problem. Derivative constraints destroy a lot of Degrees of Freedom (DOF). Bayesian beamformer destroys only one DOF but vulnerable to binning error. The proposed algorithm overcomes the problem of binning error in the Bayesian beamformer with only one extra DOF.

The near-field surrounding devices can be arbitrarily sculpted if they are placed inside a spatially variant anisotropic metamaterial (SVAM). Our SVAMs are low loss because they do not contain metals and are extraordinarily broadband, working from DC up to a cutoff. In the present work, a microstrip transmission line was isolated from a metal object placed in close proximity by embedding it in an SVAM so that the field avoided the object. Our paper begins by outlining a simple finite-difference modeling approach for studying transmission lines embedded in SVAMs. We then present our design and experimental results to confirm the concept.