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.

A regular cross terms algorithm is derived for the parameter estimation of the multi-component polynomial phase signals in additive white Gaussian noise. The basic idea is first to separate its phase parameters into two sets by nonlinear procedures£¬and then each set has half of the parameters in its auto-terms. Furthermore, using two linear transforms to deal with the two signals respectively, the phase coefficients of cross terms can be regulated for the identification and elimination of false peaks caused by the cross terms. Simulations are presented to illustrate the performance of the proposed algorithm.

This work deals with the inverse source problem starting from the knowledge of the radiated field in the near field zone. The inverse problem is stated as the inversion of a linear integral equation and the Singular Value Decomposition (SVD) is exploited as an analysis and inversion tool. In particular, here, we deal with a 2D geometry and aim at comparing the features of the inverse problem in dependence on the nature of the source (electric or magnetic).

A one-dimensional electromagnetic bandgap (1-D EBG) ground plane was designed and characterized. The 1-D EBG ground plane, composed of metal patches, metal lines, and a ground plane, has in-phase reflection characteristics when the polarization of the incident electromagnetic waves is parallel to the direction of the EBG unit-cell array. The proposed 1-D EBG ground plane was applied to the design of low-profile directive dipole antennas. The radiators of the designed antennas could be placed very close to the 1-D EBG ground plane without noticeable performance degradation of the antennas. In particular, the dipole antenna designed with the 1-D EBG ground plane and directors has higher directivity and a better F-B (front-to-back) ratio as compared to a conventional dipole antenna backed with a normal ground plane.

In this paper, tunable single-negative (TSNG) metamaterials based on microstrip with varactor diodes loading are investigated. By tuning the external voltage, our structure can provide either an epsilon-negative or a mu-negative band gap, with varying gap width (the ratio of bandwidth to center frequency can be from 0 to over 100%) and depth (from 0 dB to about -30 dB). Moreover, the tunneling mode in a heterostructure constructed by epsilon-negative and TSNG metamaterials is also studied. The results show that its transmission, Q-factor, and electromagnetic localization can also be controlled conveniently. All these properties make our structure promising to be utilized as a practical switching device, or a suitable platform for the study of nonlinear effect in metamaterials.

The paper deals with a method to measure the unknown impedance of metamaterial antenna made in Composite Right/Left-Handed (CRLH) Co Planar Wavegiude (CPW) technique for the millimeter wave frequency domain. The method uses a measurement setup made of a high frequency vector network analyzer (VNA) and an on-wafer characterization equipment. The measurement procedure consists in placing the probe-tip of the on-wafer equipment and to move it along the feedline of the antenna radiating structure until the minimum values of the return loss is reached. Using the facilities of the on-wafer equipment (micrometric screws to move the probe-tips) and knowing the geometrical dimensions of the antenna structure, the dimension and the position of an equivalent open-circuit matching stub are obtained. Then, using relationships derived from the transmission lines theory, real and imaginary parts of the unknown antenna impedance are computed.

A method to enlarge the omnidirectional photonic bandgaps (PBGs) has been presented in the one-dimensional photonic crystals by sandwiching a superconductor layer between two dielectric materials to form a one-dimensional ternary periodic structure. The angle- and thickness-dependence of these PBGs have been investigated in detail, and then the thermally-tunability of these omnidirectional PBGs by controlling external temperature of the superconductor is discussed. It is shown that these omnidirectional PBGs can be extended markedly in the one-dimensional ternary photonic crystal and the gap width or the wavelength range can also be tuned by varying external temperature.

In this work, a novel multi-carrier Tx-Rx system based on rationally synchronized oscillators to be used in RF-source localization applications is presented. The Tx subsystem is composed by two rationally synchronized oscillators, with different operation frequency, which share the reference signal. This signal is transmitted together with the one generated by the oscillators. In the Rx subsystem, the reference signal is provided by an oscillator which is synchronized with the received reference signal. According to the simulation results, with the proposed approach, the determination of the relative phase variation suffered by the transmitted signals, due to the propagation channel, can be achieved with an error less than 0.6^o. It is also shown that the dynamic response of the system can be optimized by properly selecting the operation point of all oscillators.

Achieving and controlling highly selective response in an electronic component could be particularly beneficial for numerous practical applications. In this work, we consider a simple configuration of a discontinuous parallel-plate waveguide with a narrow rectangular ridge filled with axially anisotropic material. The formulated boundary value problem is rigorously treated with help from mode matching technique. The variables with respect to which the device exhibits highly selective behavior and the parameters through which the regulation of sharp variations becomes possible, have been identified. Several graphs demonstrating these properties are analyzed and discussed.

In this paper, a novel and computationally efficient algorithm which combines Array Signal Processing (ASP) approach with Fourier Optics (FO) is developed in the realm of gain enhancement achieved by placing Uniplanar Compact-Photonic Band Gap (UC-PBG) structures on top of microstrip antennas. The proposed scheme applies FO to the well-known sampling theorem borrowed from Digital Signal Processing (DSP) analysis in the framework of ASP approach which we refer to as the FDA algorithm. The FDA algorithm is suitable for lossless UC-PBG structures with 1-D, 2-D and 3-D lattice of canonical geometrical apertures, such as circular, octagonal, hexagonal, and square. In order to validate the proposed approach, two different UC-PBG structures of octagonal and circular apertures are considered at 2.6 GHz. The UC-PBG structures under consideration consist of two layers positioned above a microstrip antenna; each layer is an array of 9×9 apertures separated by half of the focal length distance of the lens in the near-field of the microstrip antenna. The performance of the microstrip antenna with and without the UC-PBG is reported using numerical simulations performed using CST Microwave Studio (CST MWS) based on the Finite Integration Technique (FIT). The radiation patterns and directivity of the microstrip antenna based on UC-PBG structures are evaluated using the proposed FDA algorithm and validated against numerical results obtained from CST MWS where an excellent agreement is found between the FDA algorithm and the 3-D full wave simulations. The UC-PBG structure of octagonal apertures provides a remarkable enhancement in the bore-sight gain of about 7.8 dBi at 2.6 GHz with respect to that obtained from the conventional microstrip antenna, while the circular apertures provide gain enhancement in excess of 10 dBi above the gain of the same microstrip antenna.