This paper reports the design and development of rectangular microstrip antenna comprising a novel slot for enhancing the impedance bandwidth and gain. By incorporating a slot of optimum geometry at suitable location on the radiating patch, the antenna provides 78.08% (3.39 - 7.73 GHz) of impedance bandwidth and 3dB of gain without changing the nature of broadside radiation characteristics when compared to conventional rectangular microstrip antenna. The proposed antenna may find applications in mobile WiMax, IEEE802.11a, HIPERLAN/2, cordless phones, fixed wireless etc. Design concept of antennas is given, and experimental results are discussed.

A compact planar ultra-wideband (UWB) dipole antenna having band-notched characteristic is presented. The dipole antenna has the shape of a modified annular ring and is fed by a 50-Ω microstrip line. Cutting a slot in each radiating annular ring improves the input impedance bandwidth. With the design, the return loss is lower than -10 dB in 3.1 GHz-10.6 GHz frequency range. In addition, band-notched filtering properties in the 5.15 GHz-5.825 GHz are achieved by etching four rectangular slits in the ground plane, and the radiation pattern is similar to a conventional dipole antenna. A good agreement is found between the simulation and the experiment. Details of the proposed antenna design and the experimental results are presented.

A narrowband reflection and/or transmission filter made of heterostructured multilayer with two different ultrathin metallic films is proposed. The multilayer structure is a cascaded system that is formed by using two narrowband reflection-and-transmission filters. Each individual filter is made of an ultrathin metal film in front of a planar Fabry-Perot resonator. Using the transfer matrix method in a stratified system, the optical filtering properties are theoretically investigated and analyzed. It is found that the reflection peak at the design wavelength in the original individual filter becomes a dip in the heterostructured filter. The role played by the stack number of Bragg reflector in the design of narrowband filter is also clearly elucidated.

The T-matrix approach is effective in analyzing electromagnetic scattering from finite scatterers. Yet for scatterers with extreme geometry, this approach may fail. One example is its inability to analyze scattering from dielectric cylinders with large aspect ratios. To deal with such difficulty, recently we proposed a method based on an extension of the T-matrix approach, where a long cylinder is hypothetically divided into a cluster of identical sub-cylinders, for each the T matrix can be numerically stably calculated. Special care was paid to fulfill the boundary conditions at the hypothetic surface of any two neighboring sub-cylinders. The resultant coupled equations are different from that of multi-scatterer theory. The model results were in good agreement with experiment data available in the literature. However, the validity region of the proposed method was not fully characterized. Now we have developed and validated a method of moment (MoM) code, and are in a position to carry on the task of characterizing the validity region. The proposed method is found to be applicable to dielectric cylinders of arbitrary length as long as the T matrix is attainable for the elementary sub-cylinder. The conditions for the T matrix to be numerically stably calculated in terms of the equivalent volumetric radius and relative dielectric constant are also empirically obtained.

This paper derives its link of direction of arrival (DOA) and direction of departure (DOD) estimation problem for multi-input multi-output (MIMO) radar to the trilinear model. With the exploitation of this link, we present a trilinear decomposition-based blind algorithm for angle estimation in MIMO radar. After the algorithmic presentation and discussions for identifiability results, trilinear decomposition-based angle estimation under different array conditions has also been investigated. Our proposed algorithm works well without either spectral peak searching or pair matching, has better angle estimation performance than ESPRIT, and even supports small sampling sizes. Simulation trials testify that the merits of our algorithmic performance are in collaboration with theoretical findings.

This paper presents a novel spurious suppressed bandpass filter designed with triangular stepped-impedance resonators. The proposed resonators are folded for a triangular schematic, which creates two transmission zeros. By varying the line width of resonators, one of the zeros is tuned to suppress the first and second spurious responses, and the other is used to improve skirt selectivity. The current study analytically derives explicit design equations and fabricates a three-pole Chebyshev bandpass filter centered at 1.5 GHz based on the direct-coupled structure. The experimental results show spurious suppression improvement more than 20 dB up to 5.6 f₀.

A novel printed dual circular ring monopole antenna with low radar cross section (RCS) for ultra-wide band (UWB) application is proposed. The proposed antenna is designed to realize RCS reduction. The two circular rings are connected by several metallic via holes to improve the radiation characteristics of the proposed antenna. Its UWB-related characteristics are simulated and experimentally verified. The RCS performance of the proposed antenna under different loads is studied and compared with that of a commonly used circular-disc monopole antenna. The results show that the proposed antenna has good radiation performances and lower RCS than the reference antenna. The proposed antenna serves as a good candidate in the design of UWB antenna with the requirement of RCS control.

In this paper direction-of-arrival estimation (DOA) of multiple narrow-band sources, based on higher-order statistics using propagator, is presented. This technique uses fourth-order cumulants of the received array data instead of second-order statistics (auto-covariance) and then the so-called propagator approach is used to estimate the DOA of the sources. The propagator is a linear operator which only depends on the array steering vectors and which can be easily extracted from the received array data. But it does not require any eigendecomposition of the cumulant matrix of the received data like MUSIC algorithm. Computer simulations are carried out to compare the performance of the proposed method to those of methods based on auto-covariance using MUSIC and propagator algorithms.

A new approach of imaging reconstruction of concealed PEC targets in a dielectric closed box, using azimuth multi-angle measurements, is developed. As the broadband stepped-frequency radar transmits planar wave from different azimuth directions around the target, the backscattered electrical fields in both the amplitude and phase are obtained. The two-dimensional fast Fourier transform (2D-FFT) algorithm for spline interpolation is adopted for uniformly sampled backscattering fields. Then, 2D images of a dielectric box with and without the concealed targets can be numerically simulated. Multi-azimuth backscattering electri- cal fields of complex shaped PEC targets and dielectric surrounding walls are calculated by the method of moments (MoM), which is based on the coupled volume-surface integral equation (VSIE). The concealed targets can be well identified from the imaging reconstruction.

This paper presents a basic analysis about experiment results using planar coils inner ring coils, defining a transformer, when this system is excited by square wave voltage. In this study phenomena of response to step voltage due to parasitic capacitances is analyzed, and a sum of responses when the input square wave frequency increases is given too. These phenomena are uncommon in literature, which can be applied to several areas of researches in electrical engineering, pulse transformers and power electronics.

A highly miniaturized low-pass filter using microstrip open-loop and semi-hairpin resonators is designed and analyzed to enhance the bandwidth and further size reduction of this kind of elements. Initially, two microstrip open ring resonators and separately, two semi-hairpin resonators are arranged and attached back-to-back to each other respectively. A compact LPF is designed and simulated using these modified resonators. The size reduction of this proposed filter is reported about 65% with 190% enhancement of bandwidth in analogy with the conventional low-pass filters.

This paper presents a de-interleaved subsampling receiver architecture suitable for homodyne receivers. The proposed topology requires only a single branch to down-convert and extract the in-phase (I) and quadrature (Q) baseband signals. Using a single-branch receiver eliminates the I/Q mismatch issue of traditional direct down-conversion receivers. The simplicity of the proposed receiver architecture makes it an alternative solution for multi-band and multi-standard applications.

A design methodology of narrow band-pass frequency selective surfaces (FSSs) using the Fabry-Perot approach is presented. The whole FSS structure consists of two identical single layer FSSs separated by a foam layer, which forms a Fabry-Perot interferometer (FPI). The band-pass characteristic is a result of the FPI. The pass band can be controlled by the thickness of the foam, and the bandwidth can be controlled by the reflection coefficients of the single layer FSSs. The effects of both metallic and dielectric losses are discussed. It is interesting to note that the transmission peaks of FPI with high Q factor decline rapidly and finally disappear as the losses increase, and the insertion loss is mainly due to the refection. The relationship between the insertion loss and the Q factor of the FPI is examined. As examples, narrow band-pass FSSs at about 96 GHz with different bandwidths are designed.

In this work, a polarisation agile antenna based on an array of two injection locked oscillators is presented. The proposed topology provides a theoretical relative phase shift range of 360 degrees between the output signals, which can be easily controlled through two DC voltages. The behaviour of the system is studied, both through simulations and measurements of the manufactured prototype, focusing on the joint performance of the oscillators. The data transmission capabilities of the system are analysed, proposing a solution for phase modulated signals.

In this paper, two broadband measurement methods, shorted microstrip method and microstrip trnasmission method, are discussed, and the complex permeability of ferromagnetic thin films is measured from 100MHz to 18GHz. The S-parameters of the two measurement fixtures are measured by vector network analyzer (VNA). The perturbations of the thin film loaded in the measurement fixture are analyzed; the discontinuity between coaxial and microstrip is considered; the effective permeability is deduced from measured S-parameters; the permeability of ferromagnetic thin films is extracted from effective permeability by using conformal mapping. The results show that the experimental results agree with the theoretical ones closely, and higher measurement sensitivity and accuracy are achieved by using shorted microstrip method.

In this paper, a novel microstrip bandstop filter by etching a square split ring in the center of microstrip line is proposed. Low insertion loss in the passband, high rejection level and integrated structure should be mentioned as advantages for this resonator. A transmission line model for this resonator is introduced and its resonant frequency is calculated analytically. Good agreement between the experimental results, full-wave simulation, transmission line model and analytical result has been achieved.

In this paper, a new technique that combines adaptive transmit antenna selection, transmit power allocation and iterative detection is introduced for the modified Turbo-BLAST system. At the transmitter, in order to minimize the BER performance of the overall system, an adaptive transmit antenna selection scheme is proposed to select the appropriate antenna subset for the actual transmission, and the proper power is allocated for the selected antennas subject to the total transmit power constraint. At the receiver the modified MMSE detector taking the imperfect CSI into account is used to remove the co-antenna interference. Finally the turbo principle is employed for iterative detection to further lower the BER results. Simulation results show that the introduced adaptive transmit antenna selection and power allocation algorithm can significantly improve the BER performance, and the iterative detection technique can further enhance the performance.

This paper presents an analysis about the results of experiments using planar coils inner ring coils to determine a transformer. The excitation of this system was a square wave voltage, where experiments were realized in two ways: considering planar coil as primary and observing responses on secondary being ring coil (direct system) and the inverse (ring coil as primary and planar coil as secondary-inverted system). In this study, a phenomenon not common in literature on system response is analyzed, showing effects of changes on transfer function in both cases when varying turn numbers of each coil and several variations on responses due to changes on resistances, parasitic capacitances, self and mutual inductances of the coils. The uncommon phenomenon appears as modulated response on specific turn ratio. The obtained results can be used to researches in areas as power electronics and pulse transformers.

Radio over Fiber (RoF) system has attracted much industry and research interest to extend the wireless cell coverage and reduce the cost by using the distributed remote antenna units (RAUs). However, the effective transmission fiber length in the RoF systems would be limited due to the time division duplex (TDD) mode used in the practical WiMAX access. Here, we study the transmission limitations and performances of the standard WiMAX signal for RoF systems. The throughputs and packet-losses at different fiber lengths are also investigated and analyzed. Besides, in order to increase the emitting power of the RAUs, a robust TDD switching mechanism is proposed in each RAU for RoF system.

In this paper, an approach based on a multi-scaling strategy for the reconstruction of the non-measurable components of equivalent current distributions is tested against experimental data. An extensive set of simulations is carried out considering single and multiple scatterers with homogeneous as well as inhomogeneous properties. Selected results are reported and discussed to show potentialities and limitations of the method.