Wireless underground sensor networks (WUSN) consist of wireless devices that operate below the ground surface. These devices are buried completely under dense soil, thus electromagnetic wave transmits only through soil medium. However, the high attenuation that caused by soil is the main challenge for the electromagnetic wave transmission for WUSN. In this study, architecture of wireless underground sensor network communication was established. The experimental measurements were conducted using WUSN sensor nodes at three different carrier frequencies, respectively. Received signal strength and packet error rate were examined for communication links between the sensor nodes. The test results showed that carrier frequency was one of the main factors that affected electromagnetic wave propagation in the soil medium. It was concluded that the burial depth of the sensor nodes, horizontal inter-node distance, and soil volumetric water content have significant impacts on the signal strength and packet error rate during the electromagnetic wave propagation within a WUSN.

The insertion loss of different materials is measured at 2.4, 3.3 and 5.5 GHz bands. Directive antennas with a nominal gain of 19 dB are used in the measurement campaign. The height of the antennas has been selected to have the minimum possible reflection from around surfaces. Metallic door with porthole window, metallic grid, glass window, human beings and tree's insertion loss are measured. The metallic grid presents a band pass filter function with a resonance frequency between 3.2 to 3.3 GHz. Other materials have an insertion loss that increases with the increment of the operating frequency.

This paper presents a fully integrated broadband low power high isolation subharmonic mixer. The proposed mixer achieves a double-balanced architecture by adopting a single-to-differential frequency-doubling technique, and improves port-to-port isolations. The mixer fabricated by tsmc 0.18 μm Mixed Signal CMOS process achieves maximum power conversion gain of 7.1 dB, input third-order intercept point (IIP3) of -6.9 dBm, input second-order intercept point (IIP2) of 33.5 dBm, and single side-band noise figure of -19.6 dB over the 2.3-5.8 GHz fourth generation of mobile phone communications standards (4G) frequency band. The LO-RF, LO-IF and RF-IF isolations are 82.8 dB, 66.5 dB and 62.3 dB, respectively. The measured power consumption is 2.95 mW at a 1.8 V power supply.

A transparent monopole antenna operating at 2.30 GHz is presented in this paper. The radiating element and ground plane are both designed using AgHT-4, while the substrate is made of glass. The simulated and measured impedance bandwidths (BWs) are 41.89% (2.00-3.06 GHz) and 90.91% (1.5-4.00 GHz), respectively. These results were obtained by using a suitable arc-shape slot on the ground plane; and the BWs cover the IEEE 802.16e standard for WiMAX application in the 2.30 GHz band. The gain of proposed antenna is 3.16 dBi, and there is close agreement between measurement and simulation results, in terms of return loss and radiation patterns.

A reconfigurable beam forming antenna prototype using a spiral feed line is proposed in this paper. The presented antenna is integrated with PIN diode switches at a specific location of spiral feed line. It is discovered that the beam steering ability is greatly influenced by the spiral arm feed network. Four PIN diode switches have been incorporated at four different arms of spiral feed line to realize a beam forming ability. The intelligence behaviour of this antenna is conferred when the switches are connected to programmable intelligent computer (PIC) microcontroller. Certain configurations of PIC allow the antenna's radiation patterns to be adaptively changed within 0.01 ms. Therefore, the proposed antenna is capable of electronically forming the beam up to four different angles of +176°, +10°, -1° and -12°. This antenna is small in size with 100 mm by 100 mm of substrate dimension. In this research, the site field antenna performance relying on the received signal strength (RSS) testing is tested intensively in Universiti Malaysia Perlis with varied distant points of line-of-sight (LOS) and non-line-of-sight (NLOS) propagation. With good simulation and measurement results, this antenna could be a promising candidate to be installed in applications such as a smart antenna system, cognitive radio, WiMAX and long term evolution (LTE).

This paper introduces a mobile switchable antenna for long term evolution (LTE) of the 4^th generation (4G), applicable to all mobile service bands. The validity of this antenna is assessed by design, realization, and measurement. A new frequency-selecting method is used in the proposed antenna, based on capacitance switching among four states. Due to the limited antenna space in existing terminals, it is quite difficult to cover the entire low band with a single antenna. To overcome this difficulty, three single-pole double-throw (SPDT) switches, one 74HC04, and four capacitors are used. The resulting antenna covers the LTE (698-798 MHz) and GSM (824-960 MHz) bands in the low-band characteristic by realizing four capacitance states and at the same time covers the DCS (1710-1880 MHz)/PCS (1850-1990 MHz)/WCDMA (1920-2170 MHz) bands in the high-band characteristic. The antenna provides a gain of -1.04-6.00 dBi, a radiation efficiency of 32.73-74.99%, and omni-directional characteristics in the H-plane. Because of this outstanding performance, it is expected that the new frequency-selecting technique will be applied in 4G mobile communication terminals.

The design and evaluation of an active three dimensional (3D) millimeter wave imaging system for personnel security screening is presented in this work. The system is able to produce a highresolution 3D reconstruction of the whole human body surface and reveal concealed objects under clothing. Innovative multistatic millimeter wave radar designs and algorithms, which have been previously validated, are combined to significantly improve the previous reconstruction results. In addition, the system makes use of a reduced amount of information, thus simplifying portal design. Representative simulation results showing good performance of the proposed system are provided and supported by sample measurements.

A substrate-integrated-waveguide (SIW) antenna with high directivity for data transmission between a missile and a control platform, usually an aircraft, is presented. By simply setting vias and loading parasitic elements to a rectangle patch on an FR4 substrate, good resonance with effective concentration of current was therefore achieved. For verification, constructed prototypes of both the proposed SIW antenna and the 2/3 scaled system of the designed SIW antenna mounted on the missile were simulated and measured. Good agreement between both has been obtained. The original SIW antenna working at C band has an operating bandwidth of 100 MHz (4.78-4.88 GHz ) and an average gain of about 5 dBi as well, whereas the scaled missile-mounted antenna system has an operating bandwidth of 160 MHz (7.15-7.31 GHz ) with a peak gain of 3.7 dBi at 7.24 GHz. Also, directive radiation patterns suitable for use on data transmission in a missileaircraft transceiver system have been measured for the both cases.

A novel dual-band annular ring slot antenna is investigated. The antenna consists of a center-fed circular microstrip patch antenna with a coupled annular ring. And it is shorted concentrically with a set of conductive vias. By adjusting the parameters of the antenna, the dual resonant frequencies for two modes (TM₀₁ and TM₀₂ modes) are achieved. The antenna is fabricated and tested. Results show that the proposed antenna with height of 0.0217λ₀ can provide gains of 3.01 dBi at 2.6 GHz (the receiving frequency) and 5.74 dBi at 2.95 GHz (the transmitting frequency). Good agreement between the measurement and simulation for the return loss and radiation patterns is achieved. The proposed antenna has dual-band characteristics, simple structure, low profile, and omni-directional azimuth radiation pattern. It is suitable for aircraft both receiving and transmitting signals and frequency division duplex (FDD) applications.

Magnetic induction tomography (MIT) is a tomographic technique utilising inductive coils and eddy currents to map the passive electromagnetic properties of an object. Eddy current methods are widely used for non-destructive testing (NDT) in inspection of metallic structures. Eddy current based NDT uses a single coil or a pair of coils to scan the samples. As an emerging NDT technique, MIT scans the sample with a coil array through an eddy current based tomographic approach. In this paper, a planar array MIT system (PMIT) is proposed for 3D near subsurface imaging. This is of great importance as there are large numbers of potential applications for MIT that allow limited access to the materials under testing. The system development, practical implication, capability and limitations of PMIT are discussed. The fundamental principles are demonstrated through simulations. Experimental data are used to evaluate the capability and detectability this system has as a potential 3D subsurface imaging tool.

In high squint spotlight mode SAR, the coupling of the range and azimuth is very serious, which brings challenges to the imaging. In this paper, an extended frequency scaling algorithm is proposed, in which the range migration correction is divided into two steps. Firstly the range walk correction is implemented in 2D time domain. In the second step, the residual range migration is corrected by the frequency scaling and bulk shift operations. Though the second range compression does not consider the range space variance, the range compression is precise. In the azimuth compression, because of the range walk correction, the azimuth modulation frequency rate becomes dependent on the azimuth position. In order to equalize the azimuth modulation frequency rate, the azimuth nonlinear chirp scaling method is involved to remove the dependence. The simulation experiments verify the validity of the proposed algorithm. The comparison of the imaging quality among traditional frequency scaling algorithm, nonlinear frequency scaling algorithm and the proposed method indicates the proposed method is more suitable for the high squint spotlight SAR.

A single-side-access ring resonator topology is presented. It employs a single quarter-wavelength coupled-line that couples to a one-wavelength ring to exhibit a single-mode resonance with transmission zeros. A global synthesis is presented, in order to control the transmission zeros in its response. As the transmission zeros of the ring resonator maintains their positions when multiple identical rings are used, the global synthesis can further be used for the design of higher order filters with multiple rings. Furthermore, since only one coupled-line is used in the resonator topology, only one section of line is present in the ring, other than the coupled-line. Hence, there will be no second section of the ring that needs to be adjusted to obtain the symmetrical response during its realization, as compared to other types of ring topologies. To show the advantage of the synthesis, it is applied in the design of higher order ring-based bandpass filters, which also involve extra quarter-wavelength coupled-lines to create additional poles. Five bandpass ring filters up to 5th-order were realized using microstrip technology, and measured to validate the proposed concept. Measurement results showing good agreement with those from the simulation are also presented throughout the paper.

An improved UWB non-coplanar power divider is presented. Based on the theory of microstrip-to-slotline transition, the principle of this power divider is discussed. To improve the performances of the power divider, a tapered slot and a fan-shaped slot take the place of a circular slot in the circuit design. The simulated and measured results show a progressive return loss of input port.

A through wafer vertical micro-coaxial transition flushed in a silicon substrate has been designed, fabricated, and tested. The transition has been designed using radio frequency (RF) coaxial theory and consists of a 100μm inner diameter and a 300 μm outer diameter, which corresponded to a 1:3 inner/outer diameter ratio. The transition's through silicon structure has been achieved using standard photolithography techniques and Bosch's process for deep reactive ion etching (DRIE). The coaxial vias of the transition have been successfully metalized with a diluted silver paste using a novel filling method. To measure the behavior of the transition at high frequencies, coplanar waveguide (CPW) lines matched at 50 ohms have been integrated on the front and backside of the device. Measurement results show that the transition demonstrate good results with a reflection coefficient better than -10 dB at high frequencies from 15 GHz-to-60 GHz. Results also indicate that the transition has good signal transmission with less than -1.8 dB insertion loss up to 65 GHz. By eliminating the need for rigorous bonding techniques, the transition is a low-cost and durable design that can produce high input/output ratios ideal for commercial products.

This paper discusses the characterization of landmine by using the electromagnetic induction technique (EMI). The proposed approach is based on the identification of the physical and geometrical properties of a landmine, from the sensor response. But in such an identification, the inverse problem is unavoidable. At first, we begin by simulating the landmine signature by solving a direct problem using the finite element method which constitutes the direct model. After that, we determine the landmine characteristics by using an inverse model based on a cost function optimization. This model is based on an iterative process which coupling nite element analysis and Particles Swarm Optimization (PSO). In this step, we apply two PSO techniques: the Standard PSO (SPSO) and the Improved PSO (IPSO), and discuss the problem of local minima of the cost function. The proposed iterative model is applied to determine the conductivity, geometry, and depth of metallic landmine from its signature measured by EMI. The numerical solution gives good results for the identification of landmine.

In this work, we propose a merged coil structure for wireless chip-to-chip communication technology. Using the proposed coil structure, the chip size can be reduced, and the transmitted power can be improved by approximately 5 dB compared to typical coil structure. To verify the feasibility of the coil, an electromagnetic simulation and a schematic simulation are performed. The coil was implemented using 50-nm digital CMOS technology. From the experimental results, the feasibility was proved.

An ultra-wideband (UWB) antenna with a novel multi-layer frequency selective surface (FSS) reflector is presented. A significant enhancement in the gain has been achieved in a low profile design while maintaining the excellent impedance bandwidth of the UWB antenna. The average peak gain of the antenna has been increased from 4 dBi to 9.3 dBi as a consequence of the use of the FSS reflector. More importantly the gain variation within the frequency range from 3 GHz to 15 GHz is only ±0.5 dB. This is a significant improvement from ±2 dB gain variation of the UWB slot antenna without the reflector. This optimized FSS reflector provides the exibility of mounting a planar antenna close to conducting bodies, including screens and cases.

A method to control the transmission zero of TE_01δ mode dielectric-resonator (DR) filters for wireless base stations is proposed. Instead of using folder structures, dedicated coupling probes, or extra cavities, as required by conventional techniques, transmission zeros are realized. The feeding probes, extended along ring dielectric resonators, are used to excite the TE_01δ mode and introduce transmission zeros. By rotating the angle of feeding position, transmission zeros can be shifted to the lower or the upper stopband. Thus, TE_01δ mode dielectric resonator filters with quasi-elliptic responses are realized with only iris coupling components. Based on this method, fourth-order inline TE_01δ mode DR filters with different responses are designed and fabricated. Measured results confirm the predicted performance.

A compact waveguide(CPW)-fed dual-frequency planar monopole antenna is proposed, which can excite two modes.The antenna is composed of a epsilon negative (ENG) meta-structured transmission line (MTL) unit cell and a monopole. The first resonance is zeroth-order mode,which is described using dispersion relation of ENG MTL based on Bloch and Floquet and designed on a CPW single layer where vias are not required. And the second is electromagnetically coupled monopolar mode. The zeroth-order resonant phenomenon is employed to reduce the antenna size. To design and analyze the proposed antenna, the circuit simulation of the ENG MTL unit resonator is executed by the equivalent circuit, and the results are compared with those of full wave simulation and experiment. The results show that the presented antenna reasonable radiation characteristics of bandwidth gain and size, verified by a commercial EM simulation software HFSS11, and is suitable for compact dual-frequency antenna. Then the antenna is fabricated and measured. The realized antenna has a compact size of 0.288λ₀ x 0.199λ₀ x 0.011λ₀(25.1mm x 17.4 mm x 1 mm) at 2.43 GHz. Simulated and experimentally measured results show that the proposed antenna can operate at 2.41(2.43) GHz and 4.11(4.14) GHz bands, respectively. Good agreement between the simulated and measured results is obtained.

This paper presents two simple analytical models of the switched reluctance motor. The first model is constructed on two flux linkage-current characteristics, the aligned position one calculated via finite element analysis (FEA), and the unaligned position characteristic calculated by using motor geometry data. The second model is based on three flux linkage-current characteristics, the aligned, unaligned and average one, obtained by employing the FEA. In both cases the direct and inverse models are defined. The models consider the core nonlinearity and the influence of the rotor position on the motor behavior. The estimated magnetizing and torque characteristics are compared with that calculated via two dimensions FEA for a switched reluctance motor (SRM) sample and with the test bench obtained ones. The merits and the drawbacks of the models are evinced.