In many cases, the study of DOA estimation techniques is developed based on ideal condition of signal sources and array sensor antennas. But, there are much more errors as a result of signal shadow effects from noise contribution and interference of installation environment in real system. In this paper, the DOA estimation algorithm using the de-noising pre-processing based on time-frequency conversion analysis was proposed, and the performance was analyzed. This is focused on the improvement of DOA estimation at a lower SNR and interference environment.

An experimental Unmanned Aerial Vehicle (UAV) Synthetic Aperture Radar (SAR) Sensor has been designed and developed at Multimedia University, Malaysia. This airborne system is an inexpensive C-band, single polarisation, linear FM airborne radar sensor. The system will be used for monitoring and management of earth resources such as paddy fields, oil palm plantation and soil surface. A series of field measurements and flight test has been conducted to verify the performance of the RF transceiver. This paper highlights the design and development of the SAR RF transceiver, as well as its evaluation result.

A novel printed monopole antenna with a pair of parasitic patches for wideband operation is proposed and studied. With the use of parasitic patches along the microstrip feed line, a good performance of bandwidth enhancement is obtained. The measured impedance bandwidth, defined by voltage standing wave ratio (VSWR) ≤ 2, can operate from 2.3 to 6.2 GHz. A tri-band printed monopole antenna is created by introducing two notched bands in the wideband antenna. Etching an n-shaped slot on the radiating element and embedding a U-shaped parasitic strip on the bottom, two notched bands from 2.78 to 3.34 GHz and from 3.78 to 5.1 GHz are achieved. The measured impedance bandwidths of the tri-band antenna are 410 MHz (2.37-2.78 GHz), 440 MHz (3.34-3.78 GHz) and 1000 MHz (5.1-6.1 GHz), which can meet the bandwidth requirements of 2.4/5.2/5.8 GHz wireless local area network (WLAN) and 2.5/3.5/5.5 GHz worldwide interoperability for microwave access (WiMAX) standards. In addition, the proposed antennas have good omnidirectional radiation characteristics and stable gains over the whole operating bands.

This paper presents the electromagnetic field expressions for 3D cassegrain system embedded in a bi-isotropic chiral medium. Mathematical formulation of Maslov is used to find the field expressions in the focal region. Effect of chirality (both the week and strong) on focal region fields is analyzed. It is seen that when the chirality effect is weak (i.e., κ < 1), chiral medium will support positive phase velocity (PPV) for both the left circularly polarized (LCP) and the right circularly polarized (RCP) modes. However for strong chiral medium (i.e., κ > 1), one mode travels with PPV and the other mode travels with negative phase velocity (NPV). The line plots are given to show the behavior of fields in the focal plane of 3D cassegrain system by changing the chirality parameter (κ).

A variable coupling ratio Y-Branch plastic optical fiber (POF) coupler based on acrylic has been developed. This device utilized two optical designs: a Y-branch structure with a novel suspended waveguide taper and a simple attenuation technique based on lateral displacement of two fibers for the non-symmetrical coupling ratios. The high index contrast waveguide taper is constructed on the acrylic block itself where the area surrounding the waveguide taper has been designed in such a way that it is surrounded by an open air. A simple attenuation technique based on lateral displacement of two adjoining fibers for each of the two output ports has been proposed and presented for the non-symmetrical coupling ratios. Lateral displacement of the fiber is set from 4.4 mm down to 1.6 mm for output fiber 1 and 0.1 mm to 1.0 mm for output port 2. Numerical analysis has been done on the lateral displacement of the output fibers which shows the device is able to generate non-symmetrical coupling ratios. Device modeling has been performed using non-sequential ray tracing technique on the Y-branch coupler performing as a 3 dB coupler with an excess loss of 1.84 dB and a coupling ratio of 50:50. The designed coupling ratios vary from 1% to 45% for port 1 and 99% down to 55% for port 2 whereas in the simulated device, ratios vary from 7.65% to 39.85% for port 1 and from 92.35% down to 60.15% for port 2. Fabrication of the device is done by producing the device structures on an acrylic block using high speed CNC machining tool. The fabricated device has an excess loss of 5.85 dB while the coupling ratios are 56.86% and 43.14% when operating as a 3 dB coupler. In the variable coupling ratio mode, the coupling ratios are 10.09% to 32.88% for port 1 and 89.91% down to 67.12% for port 2. The excess loss of the fabricated device varies from 5.85 dB to 8.49 dB.

This paper investigates the near field focusing behavior corresponding to the hyperbolic dispersion regime at the second band of the square lattice photonic crystal (PC). Numerical studies reveal the influence of the corner part negative refraction in the observed focusing effect, though the major part of the refraction is divergent at this hyperbolic regime. It is further observed that the investigated dispersion shows the surface mode behavior when the effective index of the PC slab is higher than the air medium. This aspect may be implemented for the excitation and transfer of near fields for an evanescent wave microscopy.

This paper presents a switched-beam antenna using circumferential-slot on a concentric sectoral cylindrical cavity excited by coupling slots to operate at 5.8 GHz. The advantages of this antenna are conformal structure, high directivity and capable of switched-beam pattern in six directions. The antenna design starts from a single sector which is capable of switching between radiating and non-radiating modes. The L-shaped coupling slots are proposed to accommodate the switching circuit. Each RF switch is made of two PIN diodes connected in a reverse series connection and placed across the slot at the appropriate location. Subsequently, the exciting probe is designed for matching TM₀₁ mode of the circular waveguide. The measured results of the proposed antenna give a gain of 7 dBi and |S₁₁| less than -20 dB at 5.8 GHz. This antenna is suitable for base station applications that require the switched-beam pattern in the azimuthal plane.

This study focuses on the evaluation of the performance of a rectangular waveguide for deep hyperthermia when different antennas are used. Although there are several models of hyperthermia applicators, there are no studies of the advantages of employing different antennas for waveguides used in deep seated tumor treatments. Monopole antennas are the most used radiating elements inside waveguides. Here, the modeling of a monopole and two new proposed antennas, inverted T and plate, in order to find their optimal performance is presented. Parameters like output power, SWR and transmission coefficient generated for each modeled antenna were calculated by using the finite element method. The antennas with the best performance were selected in order to model an applicator-phantom system, which was used to calculate the temperature distributions generated inside the muscle phantom. The models were based on Maxwell and bioheat equations. Finally, thermal distributions were obtained and compared. The results indicate that the plate antenna generated a better focusing. The SWR obtained was 1.25, the output power was 54.71 W of 66 W applied, and the 42°C isotherm had a size of 2 cm x 2 cm.

The number of children suffering from heat-related illness has been increasing in recent years. Children are more susceptible to heat-related illness than adults, which is considered to be caused by morphological and functional differences between adults and children. In the present study, the temperature change and perspiration in adult and child models during a simultaneous exposure to solar radiation and a hot environment are evaluated computationally. First, the power absorbed in the human body due to solar radiation is computed by the FDTD method for the Maxwell equations. Then, the temperature distribution inside the human body is modeled by the bioheat equation taking into account the thermophysiological response. Anatomically-based Japanese adult male and 3-year-old child phantoms are used. An approximative analytical solution for the core temperature elevation is also derived to clarify the dominant factors affecting the temperature elevation. From our computational results, the core temperature elevation in the child phantom for both the solar and hot-environment exposures was larger than that in the adult phantom. The temperature elevation in the child was found to be mainly caused by the exposure to a hot environmental temperature while that in the adult was due to the environmental heat and solar radiation almost equally. This difference was mainly attributed to the difference in the surface area-to-mass ratio between the adult and child phantoms. This finding was confirmed by comparison with an approximative analytical solution.

A compact circularly polarized (CP) printed antenna for global positioning system (GPS) is proposed. The antenna adopts a two-layered stacked structure, in which a diagonally positioned rectangular patch is used as the driven part and capacitively loaded patch-based crossed dipoles are used as the main radiators. Good impedance matching is obtained conveniently by using magnetic-coupling feeding technique, and antenna size reduction is realized by using capacitively-loaded structure (50% size reduction in comparison with the conventional half-wave dipole antennas). A prototype of the antenna with the size of 46 mm × 46 mm is fabricated and tested. Good agreement is achieved between the simulated and measured results, which shows that the impedance bandwidth defined by 10 dB return loss is 34.8 MHz. In addition, the 3 dB-axial-ratio bandwidth is 8 MHz, and the antenna gain is about 7 dB.

In this paper, defected microstrip structure (DMS) is applied to design a compact microstrip rat-race hybrid coupler. The proposed structure introduces both harmonic signal suppression and a significant reduction of size because half of the ring is embedded in upper section. By embedding the DMS, it is observed that the third harmonic signal is suppressed to -25 dB with respect to a conventional rat-race hybrid coupler. Besides, this structure also effectively reduces the occupied area to 25% of the conventional case. Finally, using even and odd modes analysis the ABCD matrix of the proposed rat-race coupler was extracted. It is observed that the results are in good agreement with the full wave analysis and measurement.

In this paper we present the design and fabrication of an RF MEMS tunable band-pass filter. The band-pass filter design uses both distributed transmission lines and RF MEMS capacitances together to replace the lumped elements. The use of RF MEMS variable capacitances gives the flexibility of tuning both the centre frequency and the band-width of the band-pass filter. A prototype of the tunable band-pass filter is realized using parallel plate capacitances. The variable shunt and series capacitances are formed by a combination of parallel plate RF MEMS shunt bridges and series cantilevers. The filter operates at C-X band. The measurement results agree well with the simulation results.

Tadpole-shaped (Ni, Al)/AlN nanoparticles were synthesized via evaporating Ni-Al alloy in a mixed atmosphere of N₂ and H₂. As a counterpart, the spherical-shaped (Ni, Al)/Al₂O₃ The electromagnetic parameters of as-made nanoparticles/paraffin composites were then investigated in the frequency range of 2-18 GHz. Excellent microwave absorption can be obtained for the tadpole-shaped (Ni, Al)/AlN-paraffin composite at high frequencies and in a thin layer, which is thought to be the result of the enhanced polarization in the anisotropic tadpole-shaped nanoparticles. With the increasing of the composite thickness, the frequency of effective reflection loss shifts towards lower frequencies due to an improved impedance match and absorption.

This paper presents a novel CPW-fed band-notched UWB antenna for the 3.5 GHz wireless local area network (WiMAX) applications. The prototype consists of planar diamond shaped monopole and ground plane. By inserting a novel coupling band-notched filter, which consists of an isosceles trapezoid slot in the radiation patch and a same sized isosceles trapezoid patch on the back of the substrate, with the slot connecting to the patch below through shorting hole, band-rejected filtering property in the WiMAX band is achieved. The proposed antenna is successfully designed with broadband matched impedance, good radiation patterns and constant group delay.

An antenna integrated sensor implementation for hand or finger proximity recognition is developed. Capacitive sensor was installed on the antenna of functional Nokia 6021 phone. The sensitivity of the phone with planar inverted F antenna (PIFA) integrated sensor was measured with active TRP (total radiated power) and TIS (total isotropic sensitivity) measurements. Phone active measurements were performed with/without data cables and compared to reference phones. Passive cable phone measurements were compared with active measurement results. TRP results had no significant decrements due to integration compared with the reference phone. Some TIS channels suffered from detrimental effects due to interfering signals, which were measured with a spectrum analyzer.

In the paper, an Illuminating Modes concept is introduced in order to find microstrip antenna parameters - resonant frequency, resonant resistance and radiation pattern. The concept is based on illuminating the rectangular patch by a single normally-incident plane wave. It results in the surface current density induced on the patch which is found by means of two-dimensional Spectral Domain Approach. Then, the resonant frequency, the quality factor, the resonant resistance and the radiation pattern of the analysed antenna are found. Application of Illuminating Mode concept in Spectral Domain Approach effects in analysis simplification and less time consuming calculations with no waste of the accuracy. Exemplary results for several kinds of radiators are presented, showing satisfactory level of agreement with published data.

This paper presents a two-stage optimization method for accurately extracting the coupling matrix (CM) and the unloaded quality factor (unloaded Q) of each resonator from the measured (or simulated) S-parameters of lossy cross-coupled resonator bandpass filters. The method can be used in computer-aided tuning (CAT) of microwave filters to accelerate filter design and physical realization. In our method, the Cauchy method is employed for determining characteristic polynomials of the S-parameters in the normalized low-pass frequency domain, and the CM and unloaded Q are extracted by two-stage optimization method using genetic algorithm. With respect to the previous methods available in the literatures, the proposed method allows the CM extraction of the filter with source-load coupling. Moreover, the accuracy and robustness of the method can be improved due to the usage of the second stage optimization. The proposed method is applied to the diagnosis of a general coupled resonator filter with/without source-load coupling.

A compact microstrip-fed ultra-wideband (UWB) planar monopole antenna with dual band rejected characteristic is presented in this paper. By etching two identical square complementary split ring resonators (CSRRs) in the radiation patch, dual band rejections in the WiMAX and WLAN bands are achieved. The proposed antenna, with the size of 30 × 34 mm², has been constructed and tested. And the measured results show that the antenna can operate over the frequency band between 3 and 11 GHz for VSWR<2 with dual band notches of 3.4-3.6 GHz and 5.1-5.9 GHz. Besides, in the working bands, the antenna shows good omnidirectional radiation patterns in the H-plane and monopole-like radiation patterns in the E-plane and has good time-domain characteristic as well.

This paper presents an innovative design approach that improves the characteristics of rectangular dielectric resonator antenna (RDRA). In this design the dielectric resonator (DR) fed by microstrip line feed through a rectangular ring slot. This slot represents the coupling mechanism between the resonator and microstrip line. Both DR and slot are resonant structures. Further a comparative study is made by depicting a metallic patch over the DR. The antenna has been fabricated and measured for the study, such as impedance bandwidth, return loss, radiation pattern and antenna gain. Measurement results show dual band property with an achievable impedance bandwidth of 63.67% with return loss of -34.3 dB and antenna gain 2.32 dB.

We investigate the properties of nonlinear envelope pulses developed in a coupled composite right- and left-handed (CRLH) transmission line with regularly spaced Schottky varactors. It is found that the dispersive distortion of the envelope pulses carried by each mode is well compensated by nonlinearity introduced by the varactors. In addition, we numerically observe that the collision of two nonlinear envelope pulses leads to the development of a new pair of envelope pulses (one traveling forward and the other backward). The newly developed pulses become maximal when phase-matching with the original pulses is established, and their carrier frequency is close to that of the harmonics of the colliding pulses.