A new technique for broadband material characterization, using a whispering-gallery-mode (WGM) resonator, is proposed. The resonant perturbation method is applied for the measurement of both the dielectric constant and loss tangent of various types of materials and over a wide frequency band. A comprehensive study on the reliability of using such technique, via simulations and measurements, is conducted as well. The feasibility of this device in sensing small variations of the dielectric properties of the material is investigated. Furthermore, the geometry of the resonator is slightly modified to fit liquid materials as well. This can be a promising solution for sensing human-body tissues or liquids such as blood or urine due to the sensitive nature of these resonators. The experimental setup is successfully utilized to measure the dielectric constant of a water droplet as a liquid sample as well as different material samples of arbitrary shapes and dielectric properties. The measurements are performed over the whole X- and K-bands where the obtained results are with a maximum deviation of only 3.3% for solids and 4.5% for liquids.

A modified ultra-wideband (UWB) printed rectangular antenna fed by a microstrip line is proposed. Overall dimension of the antenna is as compact as 14 (0.2 λ) × 14 (0.2 λ) × 1 mm3 where λ is the wavelength of the first resonance of the antenna. The main features of the proposed antenna are its compact size and its filtering characteristic over WLAN band. Through adjusting the dimensions of the elements of the antenna, notch frequency in different ranges of the UWB can be obtained. The resulting VSWR<1.5 impedance bandwidth is between 3.6-9.6GHz. Antenna presents a stable gain and omnidirectional radiation pattern in its operational frequencies.

In this paper, a frequency reconfigurable antenna for cell-phone applications is presented. The proposed structure is based on a conventional PIFA. In addition, two stubs, each with a varactor diode, are incorporated. In order to to achieve wideband characteristics, the first two resonant frequencies (f₁ and f₂) of the proposed antenna are controlled independently by the supplied voltages with variation of the capacitances. The equivalent circuit of the varactor diode has been extracted in order to accurately predict the performance of the proposed antenna. In addition, parametric studies regarding the capacitance and antenna length have been conducted. The measurement results show that the proposed antenna has a tunable bandwidth defined by a VSWR < 2.5 of 45.7% (606 MHz ~ 965 MHz) and 47.5% (1343 MHz ~ 2181 MHz) at f₁ and f₂, respectively. Therefore, f₁covers the LTE (698 MHz ~ 798 MHz), CDMA (824 MHz ~ 894 MHz), GSM (880 MHz ~ 960 MHz) bands, and f₂ covers the DCS (1710 MHz ~ 1880 MHz), PCS (1850 MHz ~ 1990 MHz), WCDMA (1920 MHZ ~ 2170 MHz) bands. The measured average gains varied from -4.3 dBi to -1.5 dBi at f₁ and -6.4 dBi to -2.7 dBi at f₂.

A new technique for designing the substrate integrated waveguide (SIW) frequency-agile slot antenna is presented in this paper. Similar to the metallic waveguide counterpart, the SIW is a uniconductor guided-wave structure and inherently difficult in the electronically tunable applications. To solve this problem, a single slot etched on the top conductor layer of a conventional antenna is instead of two slots to construct an isolated area, which is convenient for the DC bias. The electric length of slots can then be adjusted through two shunt varactors welded near the center of slot. As such, a SIW frequency-agile slot antenna is realized and fabricated to cover the frequency of 2.30~2.74 GHz with different bias voltages. Experiments verify our theory analysis and design process. Then, a frequency-agile multibeam antenna is developed to cover several frequency bands while switching between four different radiation patterns pointing at different spatial locations for each frequency. It presents an excellent candidate for software and cognitive radio system applications.

In this paper, a new computation model of the shielding effectiveness (SE) is proposed in order to calculate the SE of blended electromagnetic shielding fabric (BESF) by some fabric structural parameters. Some computation equations of the SE for the BESF are given according to the theoretical deduction and previous experimental results. And then a shielding coefficient in the computation model is determined by further experiments. The linear region boundary for the model is introduced to segment the computation of the SE. Results show that the SE obtained from the proposed model is consistent with that from experiments and the error is less than 2%. It can be concluded that the proposed model can accurately calculate the SE of plain, twill and satin weaves fabrics.

In this paper, a new approach to build a dual-band impedance transformer is presented. The transformer can handle impedances that are complex and vary with frequency. This transformer contains a Pi-section structure, which can be equivalent to having two different electrical lengths at the two operating frequencies. One of the electrical lengths serves as complementary angle of the other. In this way, the conjugate impedances obtained through previous process are transformed to real impedance concurrently. All parameters are derived from closed-form equations. In addition, several simulations as well as a fabricated power amplifier (PA) are presented to verify the proposed transformer. The measured result performs a good agreement with the simulated one in return loss and gain. This transformer may find use in different stages of a transceiver such as power amplifiers which operate at two independent frequencies.

In this paper, we propose a wideband internal Planar Inverted-F Antenna (PIFA) by novel feeding structure at practical mobile handset. The proposed antenna by novel feeding structure shows 33.49% wideband impedance bandwidth, compared to 16.92% impedance bandwidth of normal feeding structure of PIFA. We explain novel feeding structure antenna by using equivalent circuit. The normal feeding structure of conventional PIFA has the inductive reactance structurally. To reduce its inductive reactance, a shunt inductive reactance using a novel feeding structure is added to normal feeding structure of conventional PIFA, structurally. So, reactance of PIFA is decreased and impedance bandwidth of PIFA is increased. The size of proposed antenna is 29.2 × 8.2 × 8.3 mm³. As well as, the implemented antenna has a good radiation pattern and high antenna gains despite very small volume.

In microwave induced thermo-acoustic tomography (MITAT) system, radiation of an antenna is a near field problem which gives rise to a non-uniform distribution of microwave radiation power in detection area. Due to this non-uniform distribution, the contrast of MITAT image which is proportional to the absorbed microwave energy will not reflect the real characteristics (dielectric properties) of biological tissues. In this paper, an image correction method based on electromagnetic simulation is proposed to correct the image contrast affected by the non-uniform microwave radiation distribution. First, the distribution of the microwave radiation power is simulated through a numerical simulation framework. Conventional time-reversal mirror (TRM) technique is applied to reconstruct the image. Then the microwave power distribution is applied to correct the image. The method is numerically demonstrated. The two samples with the same microwave absorption property and with different microwave absorption properties are experimentally investigated. Both numerical simulations and experimental results demonstrate the good performance of the proposed method.

The track-before-detect (TBD) methodologies jointly process more consecutive scans and show superior detection performance for the low signal-to-noise ratio (SNR) targets over the conventional methods. A TBD algorithm based on improved Randomized Hough Transform for dim target detection is proposed in this paper. This algorithm uses the sequence numbers of scans to make sure that the point pairs are selected from different scans, avoiding the unreasonable situation that the point pairs may be selected from the same scan in the traditional Randomized Hough Transform (RHT). Second, it introduces a new voting method. Based on the minimum Euclidean distance criterion, this voting method finds the optimal parameter cell to vote, making the voting result better than the traditional RHT. In addition, we not only increase score of the optimal parameter cell but also update the corresponding parameter, thus suppressing the deviation between the recovered track and the target's track. Simulation results demonstrate the proposed algorithm can detect the dim target more rapidly and accurately than traditional RHT, especially under the background of low SNR.

The idea behind the coupling matrix identification is to find the coupling matrix corresponding to the measured or designed scattering characteristics of the microwave filter. The typical attitude towards coupling matrix parameter extraction is to use some optimization methods to minimize the appropriate cost function. In this paper we concentrate on the analytic solutions - how they may be found and their application in further optimization processes. In general case the suggested method generates complex-valued coupling matrix. For a special case of the filter without cross-couplings we give fast and simple recursive method of finding such complex-valued coupling matrix. The method is based on Laplace's formula for expanding the determinant. The complex-valued coupling matrix is used as a good starting point for the optimization methods to find the regular coupling matrix. The examples are presented showing that the optimization arrives to global minimum starting from real parts of complex-valued entries considerably more often than when the starting point is selected randomly.

This paper presents a modified Gysel power divider (PD) with harmonic suppression performance by utilizing equivalent Π-shaped, T-shaped and Π-T-hybrid-shaped open stubs transmission line (TL) models. Explicit closed-form expressions for generating parameters of the equivalent TL models are derived based on the ABCD matrix analysis. The proposed PD not only features suppression at the hoped harmonic frequencies and flexible layout, but also maintains Gysel PD's high power handling advantage. For demonstration, the simulated and experimental results of three proposed PDs at 1 GHz implemented on microstrip are given.

This paper presents an end-user evaluation of aircraft detection and identification capacity of the surveillance system deployed in terminal 4 apron of Madrid-Barajas international airport. The main goal of the system is to provide real-time surveillance information about aircraft and vehicles on the apron area, including stands, facilitating airport operation centre tasks concerned with delay minimizing and apron resources use optimizing. In order to describe system performance, a set of indicators are defined to quantify the output information reliability and to measure the capabilities of this system to automate routine airport operations.

Using the geometrical optics approximation, a theoretical prediction of the deflection angle correlation of a laser beam propagating in a hot turbulent jet is found as a functional form of the turbulent spectrum of the refractive index fluctuations. By applying the modified Von Karman model and Tatarskii model, the structure coefficient of the refractive index and the deflection angle correlation of the laser beam are then computed by means of a numerical procedure. Experiments to measure the structure coefficient are performed. A good agreement between the experimental results obtained and the theoretical predictions demonstrates the validity of the theoretical approach.

In this paper, we propose a dual-band frequency selective surface (FSS) in low frequencies with miniaturized element. A dual-concentric square element with two different slot sizes is constructed to realize dual-band passband responses. Each passband is realized by a square slot structure. Besides, we reduce the slot sizes to make the element miniature and compact. Based on this technique, a dual-band FSS with miniaturized element in low frequencies is designed. Both the simulation and experiment results show that such a FSS owes its advantages to miniature element, stable performance with various incident angles and different polarizations, which is suitable for dual-band shipboard communication.

We consider the relativistic polarization of a rotating magnetized medium in the framework of the approach suggested earlier (A L Kholmetskii and T Yarman 2010 Eur. J. Phys. 31 1233), which is based on the charge conservation law and relativistic generalization of the first Kirchhoff law to a closed moving circuit carrying steady current. We show that the polarization of a magnet brought to a rotation differs, in general, from the relativistic polarization of a translationary moving magnet, and on this way we give one more explanation to the familiar Wilson & Wilson experiment, with the explicit demonstration of the implementation of the charge conservation law.

A new design consideration is explored for a hair-pin resonator. A grounding via at the mid-point of the resonator acts as a perturbation to split the resonant frequencies. The via also suppresses even harmonics of the fundamental. The principle operation of the hair-pin resonator with a via is analyzed and verified by measurement. It is shown that such a hair-pin resonator can be made more compact using stepped impedance line. A compact 4-pole bandpass filter using the modified compact hair-pin resonator with a via is demonstrated. Simulation and measured results showed good agreement.

A new type of low-profile frequency selective surface (FSS) with an overall thickness of λ/40 and a second-order band pass frequency response is presented. The proposed FSS is composed of two metal layers, separated by a thin dielectric substrate. Each layer is a two-dimensional periodic structure with sub-wavelength periodic unit cells. By printing the same topology on each side of the substrate, a second-order frequency response is realized. To provide a physical insight into the operating mechanism, equivalent circuit networks are also investigated in each step of design procedure. Using the proposal technique, low profile and reduced sensitivity to angle of incident wave for both TE and TM polarizations are obtained and the overall thickness of the substrate is fairly thin. FSS samples are designed, fabricated, and installed in waveguide operating at X-band and a good agreement between the simulated and measured results is achieved.

The growing interest of Radar community in retrieving the 3D reflectivity map makes both polarimetric SAR interferometry and SAR tomography hot topics in recent years. It is expected that combining these two techniques would provide much better discriminating ability for scatterers lying in the same pixel. Generally, this is about reconstruction of scattering profiles from limited and irregular polarimetric measurements. As an emerging technique, Compressive Sensing (CS) provides a powerful tool to achieve the purpose. In this paper, we propose a l_2,1 mixed norm sparse reconstruction method for jointly processing multibaseline PolInSAR data based on multiple measurement vector compressive sensing (MMV-CS) model, and also address the signal leakage problem with MMV-CS inversion by presenting a window based iterative algorithm. The results obtained by processing simulated data show that the proposed method possesses superior performance advantage over existing methods.

Nonsynchronous noncommensurate impedance transformers consist of a combination of two types of transmission lines: transmission lines with a characteristic impedance equal to the impedance of the source, and transmission lines with a characteristic impedance equal to the load. The practical advantage of such transformers is that they can be constructed using sections of transmission lines with a limited variety of characteristic impedances. These transformers also provide comparatively compact size in applications where a wide transformation ratio is required. This paper presents the data which allows to estimate the achievable total electrical length and in-band reflection coefficient for transformers consisting of up to twelve transmission line sections in the range of transformation ratios r=1.5 to 10 and bandwidth ratios χ=2 to 20. This data is obtained using wave transmission matrix approach and experimentally verified by synthesizing a 12-section nonsynchronous noncommensurate impedance transformer. The measured characteristics of the transformer are compared to the characteristics of the conventional tapered line transformer.

This paper presented an estimation method of maximum effective isotropic radiated power (EIRP) and electro-magnetic field (EMF) strength of a wideband code-division multiple-access (WCDMA) base station based on over-the-air measurements of a pilot channel in a code domain. To verify the feasibility of the proposed method, we estimated the maximum EIRP and EMF strengths of the self-designed test base station, and compared them with EIRP and EMF values measured by the traditional test scheme. Then, we applied our estimation scheme to the inspection test for a commercial base station. The maximum difference between the estimated EIRP values from our method and the reported values is 1.3 dB. The estimated EMF results show more than 90% agreement with both the traditional EMF measurement value under a full-traffic load condition and the theoretical value. Therefore, it can be concluded that our proposed estimation method should be an effective inspection test for domestic base stations.