This paper presents a new quadrature voltage-controlled oscillator (QVCO), which consists of two p-core Colpitts cross-coupled voltage-controlled oscillators (VCOs) with an LC ring resonator to provide the quadrature outputs. The proposed CMOS QVCO has been implemented with the TSMC 0.18 μm CMOS technology and the die area is 0.478 x 0.82 mm². At the supply voltage of 1.5 V, the total power consumption is 20.4 mW. The free-running frequency of the QVCO is tunable from 9.69 GHz to 10.52 GHz as the tuning voltage is varied from 0.0 V to 2 V. The measured phase noise at 1 MHz frequency offset is -122.41 dBc/Hz at the oscillation frequency of 10.52 GHz and the figure of merit (FOM) of the proposed QVCO is -189.7 dBc/Hz.

In this study, refractive index changes associated with intersubband transitions in a spherical quantum dot, GaAs/Al_xGa_1-xAs, have been theoretically calculated in the presence of impurity. In this regard, the effect of dot radius, stoichiometric ratio, impurity and incident optical intensity on the refractive index changes have been investigated for the transitions between higher energy states, i.e., 1s-1p, 1p-1d and 1d-1f. The results show that these parameters have a great influence on the refractive index changes.

In this paper, we propose a simplified particle probability hypothesis density (PHD) filter and its hardware implementation for multiple-target tracking (MTT). In the proposed algorithm, the update step of particle PHD filter is simplified and the time-varying number of measurements is arranged in combination series/parallel mode. This may result in fixed hardware architecture and therefore present a convenient hardware implementation of particle PHD filter. Simulation results indicate that for the MTT problems, this proposed simplified algorithm shows similar performance with the standard particle PHD filter but has faster processing rate. Experiment study shows that the proposed simplified algorithm can be efficiently implemented in hardware and can effectively solve the MTT problems.

In the final step of any filter design process, the desired center frequency, coupling factor and external quality factor (Q_ext) are used to determine the physical parameters of the filter. Although in the most cases the physical dimensions of a single resonator for a given center frequency are determined using exact analytical or simple approximate equations, usually such simple equations cannot be found to easily relate the required coupling factor and Q_ext to the physical parameters of the filter. Analytical calculation of coupling factor and Q_ext versus dimensions are usually complicated due to the geometrical complexities or in some cases such as microstrip resonators due to the lack of exact solution for the field distribution. Therefore coupling factor and Q_ext of various kinds of resonators, especially microstrip resonators, are related to the physical parameters of the structure by the use of time consuming full wave simulations. In this paper a surprisingly fast and completely general approach based on a soft computing pattern-based processing technique, called active learning method (ALM) is proposed to overcome the time consuming process of coupling factor and Q_ext determination. At first the ALM technique and the steps of modeling are generally described, then as an example and in order to show the ability of the method this modeling approach is implemented to model the coupling factor and Q_ext surfaces of microstrip open-loop resonators versus physical parameters of the structure. Using the ALM-based extracted surfaces for coupling factor and Q_ext, two four pole Chebychev bandpass filters are designed and fabricated. Good agreement between the measured and simulated results validates the accuracy of the proposed approach.

A convergence study of a non-standard Schwarz domain decomposition method for finite element mesh truncation in electromagnetics is carried out. The original infinite domain is divided into two overlapping domains. The interior finite domain is modeled by finite elements and the exterior infinite domain by an integral equation representation of the field. A numerical study of the spectrum of the iteration matrix for non-convex mesh truncation boundaries is performed. The projection of the error between two consecutive iterations onto the eigenvector space of the iteration matrix is performed. The numerical results explain the observed convergence behavior of the Schwarz iterations.

A numerically efficient approach for the rigorous computation of bi-static scattering and radiation problems is presented. The approach is based on an improvement of a previous method scheme that combines the Characteristic Basis Function Method (CBFM) and the Multilevel Fast Multipole Algorithm (MLFMA). The approach combines Characteristic Basis Functions (CBFS) and subdomains functions for reducing the CPU time in the pre-process and in the solving iterative process for simple or multiple excitations. It is intended for use in very large cases where an iterative solution process cannot be avoided, even considering the matrix size reduction achieved by the CBFM. This reduction is particularly important for solving radiation or bistatic problems in which an integral equation is solved once.

This paper deals with an investigation on the polarization of an antenna array with a circular geometry. The theory shows that the polarization of a circular array exhibits a circular polarization independent of the antenna elements. Circular polarization is then achieved whatever the polarization of the elements of the array. Moreover, due to the circular geometry of the array, the entire far field pattern of the array can be obtained with the measurement or the simulation of only one antenna inside the array. The influence of the array radius on the polarization performances has been investigated. An antenna array has been built, and measurements have been performed in order to corroborate the theoretical results.

We investigate experimentally and theoretically Ultra-Wideband (UWB) wireless transmission in different WPAN scenarios. Short-range UWB wireless link (wireless fire-wire) have been studied theoretically and experimentally. Different mutual positions and distances between the antennas have been investigated. It was found that the reactive antenna coupling might decrease power budget as much as 15 dB by an antenna separation of 5 mm.

A cylindrical wave expansion method is used to obtain the scattering field for a two dimensional cylindrical invisibility cloak incorporating perfect electromagnetic conductor (PEMC) at perturbed void region. A near-ideal model of the invisibility cloak is set up to solve the boundary-value problem at the inner boundary of the cloak shell. It is confirmed that a cloak with the ideal material is a perfect cloak by observing the change of the scattering coefficients from the near-ideal case to the ideal one. However, because of the slow convergence of the zeroth-order scattering coefficients, a tiny perturbation on the cloak would induce a noticeable field scattering. A better convergence rate of the scattering coefficients has been observed for decreasing δ in PEMC case.

In this paper, we propose several array topologies to achieve good power-combining characteristics for the open slot antenna. By utilizing an appropriate feeding structure and injecting in-phase or out-of-phase signals, power-combining radiation patterns can be derived. Simulated surface current distributions of several antenna structures are presented to explain radiation mechanism. From the results of radiation performance, the advantages of gain enhancement and pattern reconfiguration are shown. By varying the phase difference of two injected signals of the open slot antenna array, two-dimensional beam-scanning radiation patterns are successfully demonstrated.

A fast method for electromagnetic imaging from monostatic full rotational near-field scattering is proposed in this paper. It is based on circular spectrum theory which exploits the Fourier decomposition of the targets distribution instead of point by point imaging in earlier works. The novelty of the proposed method is that it simplifies the relationship between the spatial frequency domain and the scattering field. The near-field scattering is analyzed by expanding the distance to Taylor series at the centre of the targets zone. The near-field focus function is then transformed to spatial frequency domain and evaluated by the method of stationary phase. The imaging result is given by two-dimensional inverse Fourier transformation from spatial frequency domain of targets. The proposed method is validated by comparing the simulation results of distributed targets with the tomographic imaging. The dynamic range of imaging result is derived by distributed targets with different reflection coefficient. Furthermore, the experiment is also conducted in microwave chamber at Ku band with target placed on the turntable.

Radome has strong effects on the radiation performances of the antenna in millimeter wave band. In this paper, the aperture integration-surface integration (AI-SI) method is adopted to analyze the electrically large antenna-radome system. The fast multipole method (FMM) is proposed to accelerate the aperture integration and inner surface integration in the AI-SI method. An electrically large antenna-radome system at W band is analyzed and measured. The radiation patterns of the system calculated using the AI-SI method with and without the fast multipole acceleration and the measured patterns are compared. The calculated patterns agree very well with each other, and both have the same agreement with the experimental results. However, the computational time of the proposed analysis with the fast multipole acceleration is reduced significantly.

On the basis of backward coupling and left-handed microstrip line, new designs of duplexers and multiplexers will be presented and tested in different configurations. By using microstrip lines with Complementary Split Ring Resonators (CSRRs) etched on the ground plane along with series capacitive gaps in the upper conductor, forward coupling will be inverted into backward coupling. Compact size and fully planar fabrication techniques are important characteristics in the devices proposed.

A compact dual-band ortho-mode transducer is presented in this paper. Two orthogonally polarized signals received by a square waveguide are separated into two orthogonal channels at 10.7-12.75 GHz and 10.3-11.9 GHz, respectively, while a single-polarized signal is transmitted at 14-14.5 GHz. To obtain good isolation between the transmit (Tx) and receive (Rx) channels of the same polarization with a compact size, an irregularly shaped diaphragm is proposed as a compact dual-function resonator, which has one transmission zero at the Tx band and one pole at the Rx band. The designed OMT is fabricated and measured in a back-to-back configuration. Measured results agree very well with simulated ones and the isolation improvement by the diaphragm is about 15 dB, which verifies our design.

A new indoor facility for electromagnetic tests is presented and used here for the specific case of bistatic radar cross section (RCS) measurements. A metallic cube is selected as test case and the results are compared with the predictions obtained with different numerical methods. Good agreement is reported.

In this paper, we consider the problem of bistatic multiple-input multiple-output (MIMO) radar systems design for parameters estimation. Maximum channel capacity is used as criterion for the problem of optimal systems design under transmitted power constraint and channel constraint. We obtain that the system design based on maximum channel capacity can be expressed as a joint optimization problem. Given the number of transmit antenna, the number of receive antenna and signal-noise ratio (SNR), the maximum channel capacity can be determined. This maximum channel capacity can be obtained from a unique appropriate power allocation and antenna placement strategy, which is very important for system design.

A novel out-of-line series-fed patch array with low cross-polarization is presented in this paper. The element in the array is fed by a stub through one-port. The feeding stub is designed to be a novel curled-horn-shaped geometry, which can effectively suppress the cross-polarization due to its symmetry. The linear array consists of two identical subarrays which are located oppositely. By the antiphase feeding of two subarrays, the cross-polarization is further reduced. Furthermore, the theory analyses of the series-fed array indicate that it is competent for being applied to phased array systems. The simulated results show the cross-polarization levels of the linear array with 20 novel elements in E and H plane are lower than −30 dB and −60 dB, respectively. And, a prototype array is fabricated. Its low cross-polarization levels confirm the effective performance of the proposed design.

A compact double-balanced monolithic star mixer for Ka-band applications using 0.25 μm GaAs pHEMT process is presented. With multi-coupled lines technology, the proposed dual 180° hybrid is produced and applied to a star mixer successfully. The proposed hybrid adopts the power divider and two types of multi-coupled lines to improve the return loss and isolation at the balance outputs of a traditional dual Marchand balun. Output ports are allowed to locate arbitrarily, eliminating a complex layout while the dual 180° hybrid is applied to double balanced star mixers. As the measurement results show, the proposed mixer achieves an operation bandwidth of 27 to 36 GHz with the best conversion loss of 6.3 dB at 28 GHz. In addition, the chip dimension can be manufactured as small as 0.81 mm².

A tunable microwave notch filter is developed on magneto-dielectric material having low saturation magnetization to attain low external dc magnetic field for biasing. A simple microstrip line at 10 GHz is developed on nickel ferrite/low density polyethylene nanocomposite system as substrates and its microwave transmission response is studied in X-band. Composite system is developed by dispersing nano sized nickel ferrite (~6.63 nm) in low density polyethylene to obtain a homogeneous flexible substrate. Saturation magnetization of 4% volume fraction of the composite is found to be 1.8745 emu/g. Tunability of Q value and insertion loss is studied with magnitude of external dc magnetic field and at different angles of its orientation with the axial plane. A very low field up to 250 G is sufficient to tune the selectivity. An insertion loss of ~-30 dB and Q ~ 375 at 10.2 GHz is observed. The interaction of magneto static modes with orientation of the applied dc magnetic bias with respect to rf magnetic field is discussed with couple mode theory. Good cut-off behaviour of more than 28 dB is observed at magnetic field angles from 23.52° to 34.21°. The experimental and theoretical couplings show close proximity.

A novel approach for the design and optimization of spherical lens antennas (SLAs) including practical feed model (PFM) is proposed. The vector spherical wave function expansions (VSWE) combined with differential evolution (DE) algorithm is adopted for the optimal design of SLAs. Moreover, the near-field aperture distributions of a Ku band dielectric loaded horn feed and a Ka band corrugated horn feed were obtained using the full wave simulation and were then taken into account in the DE optimization. The performances of the optimized 2-layer design are compared with previous works, higher directivity is obtained. Additionally, the radiation characteristics of an optimized SLA are presented, and numerical results of a 650 mm diameter 2-layer hemispherical lens antenna (HLA) with ground plane are compared to the experimental results, and good agreements are obtained. An investigation of the influence of the various lens-to-feed distances as well as aperture sizes of SLA on the aperture efficiency for a 2-layer design is also proposed.