The improved configurations with dual-mode double-square-loop resonators (DMDSLR) for tri-band application are proposed in this paper. Two sets of loops including double-square-loop and G-shaped loop are involved in the resonators. The resonant frequency equations related to DMDSLR geometries are introduced for simply designing tri-band bandpass filter (BPF). Resonant frequencies and transmission zeroes can be controlled by tuning the perimeter ratio of the square rings and the couples. To obtain lower insertion loss, higher out-of-band rejection level, wider bandwidth of tri-band, and compact applications, the miniaturized DMDSLR structure is designed. The effective design procedure is provided. The proposed filter is successfully simulated and measured. It can be applied to WLAN (2.45, 5.20 and 5.80 GHz) and WiMAX (3.50 GHz) systems.

Inverse synthetic aperture radar (ISAR) imaging is one of the most well-known techniques of radar target recognition. One of the most important issues in ISAR imaging is the improvement of the image smeared by a target with complicated motion. In this paper, we propose the discrete Gabor representation (DGR) in an oversampling scheme as an effective means of obtaining a well-focused ISAR image with a short calculation time. In contrast to other linear time-frequency transforms, the DGR obtains Gabor coefficients using the analysis window frames derived from the clearly defined synthesis window. The oversampling scheme of the DGR leads to accurate calculations of the Gabor coefficients, which denote signal time-frequency amplitude. Since each Gabor coefficient is compartmentally assigned to the associated unit cell of the time-frequency grid, the DGR can show an excellent time-frequency concentration and can effectively discriminate the Doppler components of prominent point-scatterers. The simulation results demonstrate that the DGR not only has enhanced focusing performance but also retains computational efficiency. The DGR in the oversampling scheme is expected to facilitate high-quality ISAR imaging in radar target recognition.

We consider MUltiple SIgnal Classification (MUSIC)-type imaging of perfectly conducting cracks arising in inverse scattering problems. We first explore the structure of a MUSIC-type imaging function by finding a relationship between it and the Bessel function of order zero of the first kind. Then, we design multi-frequency based MUSIC-type imaging in order to improve the traditional one, and establish a relationship with the Bessel function of integer order of the first kind. Some numerical experiments are presented to support the results of our investigation.

We propose a loop switching technique to improve the efficiency of wireless power transfer (WPT) systems using magnetic resonance coupling. The proposed system employs several loops with different sizes, one of which is connected to the system with various distances between the transmitter and the receiver. It enables the coupling coefficient to be adjusted with the distance, which allows high efficiency over a wide range of distances. The proposed system is analyzed using an equivalent circuit model, and electromagnetic (EM) simulation is performed to predict the performance. It is shown from the experimental results at 13.56 MHz that the proposed loop switching technique can maintain high efficiency over a wide range. The efficiency is measured to be 50% at 100 cm, which corresponds to a 46% increase compared to a conventional WPT system without the loop switching technique.

This paper presents herein experiments and calculations of electromagnetic induction between jointless track circuits (JTCs) and track-circuit readers (TCRs). The paper uses transmission-line theory to simulate JTC currents ahead of shunt points and electromagnetism to calculate voltages induced in the TCR antenna. Based on these calculations, the JTC-to-TCR range is defined. The paper derives expressions for the amplitude and phase of the voltage induced in the TCR antenna by the JTC current and uses them to quantitatively analyze the train control system. Experiments verify the conclusions reached based on the calculations.

The Debye expansion integrals obtained by application of the Modified Watson Transformation and Debye series expansion to the Mie series for the high frequency plane wave transmitted into a double negative(DNG) cylinder are solved in the geometrically lit regions of the corresponding Debye series terms. The Debye series expansion is made up to the possible maximum term after which double ray field formation is first observed. Using the steepest descent method and the geometrical optics approximation, the role of the lower ray in the double-ray field formation is pointed out. For refractive indices satisfying |n| ≥ 10, it is shown that the maximum Debye series term index up to which simple single-ray tracing can be performed is bigger for a DNG cylinder than that for a DPS cylinder and the difference between the term indices incrases as |n| increases.

In this paper, a miniature ultrawideband (UWB) bandpass filter with dual notch bands and wide upper stopband is presented. The ultrawide passband characteristic is achieved using a microstrip to slot line transition, and a wide upper stop band is realized using an elliptical lowpass filter. The dual band notches at 5.46 GHz and 8.04 GHz are obtained by incorporating defected microstrip structure in the input and output section. A prototype of the proposed UWB bandpass filter is fabricated and measured. The equivalent circuit of the proposed filter is also presented. A good agreement between the measured, EM simulated and circuit simulated responses is obtained.

We present a dualband terahertz metamaterial based on a hybrid 'H'-shaped cell of different sizes. The proposed 'H'-shaped metamaterial (HSM) structure, fabricated on a quartz (SiO₂) substrate, exhibits two intense electrical resonances at ~0.95 THz and ~1.26 THz, respectively. Extracted effective permittivity show negative values in 0.95-1.01 THz and 1.26-1.42 THz bands. Measured results from the terahertz time-domain spectroscopy (THz-TDS) experiments show good agreement with the simulated results.

The wideband and omnidirectional performance of a printed dipole antenna with a novel coupling feed structure is presented. Besides using printed dipole for omnidirectional radiation patterns, the coupling feed structure, which includes the transmission line coupling to a slot line to effectively improve the impedance matching, can be used for bandwidth enhancement. A wideband impedance characteristic of about 45.6% for VSWR ≤2 ranging from 1.54 to 2.45 GHz is obtained. The omnidirectional radiation patterns in the whole operation bands are achieved which the un-roundness in H-plane is less than 1.6dB. It is sufficient for accommodating recent wireless communication services such as DCS1800, PCS1900, UMTS, IMT2000, Wibro, etc. Furthermore, the proposed antenna should be a good candidate as a unit of the omnidirectional array. A prototype has been fabricated and tested, and the experimental results validate the design procedure.

A novel microwave filter tuning method based on vector fitting and aggressive space mapping (VF-ASM) technology is presented in this paper. The filter tuning is performed as a two step procedure. First, the equivalent circuit parameters are extracted through vector fitting method by a series of S-parameter measurements. Second, the optimal screw positions are calculated through ASM techniques. this novel tuning technique has been tested successfully with cross-coupled six-resonator and direct coupled eight-resonator filters.

Ultra-wideband synthetic aperture radar (UWB SAR) is a sufficient approach to detect landmines over large areas from a safe standoff distance. Feature extraction is the key step of landmine detection processing. On one hand, the feature vector should contain more scattering characteristics to discriminate landmines from clutters; on the other hand, the dimension of feature vector should be lower to avoid the "curse of dimensionality". In this paper, a novel feature vector extraction method is proposed. We first obtain the scattering information in the four-dimensional domain, i.e., range, azimuth, frequency and aspect-angle, via the space-wavenumber distribution (SWD). Since the data after SWD are with higher dimension and local nonlinear structures, a typical manifold learning method, Isomap, is used to reduce the dimension. The validity of the proposed method is proved by using the real data collected by an airship-borne UWB SAR system.

Switch mode power amplifiers offer high efficiency approaching 100% for an ideal case. This paper discusses the operation mode of broadband switch mode class-E power amplifier designed previously by the authors for UHF applications (600-1000 MHz). A method to extract the waveforms at the die reference plane from the time domain analysis using 50 Ω environment systems is discussed. It has been observed that the designed class-E power amplifier operation was not maintained ideally over the entire band; however, it was operating close to the class-E operation.

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.