The wireless link between a mobile phone and its surrounding crucially depends on the quality and properties of the mobile phone antenna. The process of antenna selection is a multi-criteria decision-making problem with conflicting and diverse objectives. In this work, a model was built to select the best GSM mobile phone antenna in the design phase to increase the overall performance in the band. The model includes building an analytic hierarchy structure with a tree of hierarchical criteria and alternatives to ease the decision-making. The antenna options considered were limited to retractable whip antenna, loop chip antenna, monopole antenna, planar inverted F-antenna (PIFA), microstrip patch antenna, and printed slot antenna. An Analytical Hierarchy Process (AHP) was used to assist in building the model and help draw decisions. As a result of the decision making process, the monopole antenna was found to be the best choice for the GSM mobile phone antenna. Expert Choice™ software was used to conduct the experimental assessments. The judgments were found to be consistent, precise and justifiable with narrow marginal inconsistency values. The paper also presents a thorough sensitivity analysis to demonstrate the confidence in the drawn conclusions.

This paper considers broadband signal transmission via high-voltage/broadband over power lines (HV/BPL) channels associated with overhead power transmission. To determine the end-to-end channel characteristics of various overhead HV/BPL multiconductor transmission line (MTL) configurations, the chain scattering matrix or T-Matrix (TM) method is adopted. The overhead HV/BPL transmission channel is investigated with regard to its spectral behavior, its {end-to-end} signal attenuation, and phase response. It is found that the above features depend critically on the frequency, the coupling scheme applied, the physical properties of the cables used, the MTL configuration, and the type of branches existing along the {end-to-end} BPL signal propagation. Unlike the older models that underestimate the broadband transmission potential of overhead HV lines significantly, the results demonstrate that the overhead HV grid is a potentially excellent communications medium, offering low loss characteristics over a 100 km repeater span well beyond 100 MHz and guarantees the imminent coexistence of low-voltage (LV), medium-voltage (MV), and HV BPL systems towards a unified transmission/distribution smart grid (SG) power grid.

The performance of high resolution subspace-based algorithms are particularly sensitive to the prior information of the source number, the Signal-to-Noise Ratio (SNR) and the snapshot. Although the existing direction-of-arrival (DOA) estimation methods without estimating the source number could eliminate the awful impact brought by incorrect source number estimation, yet its performance would get deteriorated by small snapshots and low SNR. Methods which exploit noise and signal subspaces information simultaneously, such as SSMUSIC, could provide a high resolution performance in such nonideal circumstances. However, its performance would degrade severely when the prior information of the source number is incorrect. To provide a DOA estimation method without estimating the number of source, which has a high resolution performance in small sample and low SNR scenario, using all information spreads in eigenvalues and eigenvectors, this paper reconstructs a new spatial spectrum which is very similar to the SSMUSIC algorithm. In order to enhance the robustness of the new method, we provide an empirical method to modify the eigenvalues to prohibit the spreading of noise eigenvalues caused by snapshot deficient and low SNR. To verify the validity of the new method, comparisons with other algorithms are made in computer simulations and the measured data test.

This paper proposes a compact printed ultra-wideband (UWB) multiple-input-multiple-output (MIMO) antenna with a dimension of 38 x 91 mm². The presented UWB-MIMO antenna is comprised of two identical patch elements with D separation distance on the same substrate. The basic single antenna structure has a novel design comprising seven circles surrounding a center circle with partial ground plane implementation. Furthermore, the experimental antenna has peak gain of 5.3 dBi between an operating frequency of 2.8 GHz and 8.0 GHz under a minimum reflection coefficient of less than -10 dB (S₁₁<-10 dB). Moreover, the antenna successfully achieved mutual coupling minimization of < -17 dB, eventually resulting in enhancement of radiation efficiency. Besides, the UWB-MIMO's correlation coefficient was effectively reduced to less than -22 dB, which reflected an improvement in the antenna's diversity. In this paper, the proposed antenna is examined both numerically and experimentally.

This paper presents the field trial measurement data of WiMAX base station; it includes the system coverage, signal strength and available transmission rate. Data consisting of real time images, VoIP internet telephone are transmitted through Skype software by using WiMAX, HSDPA (3.5G) and EDGE (2G) transmission techniques, and these data are connected to centrally equipped wireless monitoring servers to perform data monitoring and analysis. Finally, we make comparisons, analysis and discussions of these three transmission techniques from the measured and characterized data.

This paper presents a frequency reconfigurable cedar-shaped fractal antenna. The special shape of the patch makes it simpler to integrate RF switches to connect consecutive branches. The proper activation/deactivation of the switches alters the current flow and changes the resonance frequency. Simulated and measured results show the characteristics of the presented design.

In circular synthetic aperture radar (CSAR), the radar collects data over a circular not a linear trajectory. The two-dimensional (2D) CSAR image also contains three-dimensional (3D) information about the target. In this paper, we propose an imaging algorithm for 3D target reconstruction with two-pass CSAR observations so as to overcome the problem of limited azimuthal persistence for real anisotropic targets, and avoid the assumption that target falls into the same resolution cell for each elevation pass when multi-pass observations are used. In the algorithm, the first step is to divide both of the two full-aperture CSAR data into subapertures in the same way; the second step is to obtain, for each subaperture, the height of target according to the established relationship between the pixel displacements in the image pair of two observations on the same focal plane and the pixel displacements in the image pair of one observation on two different focal planes; the third step is to obtain the 3D target coordinates based on the retrieved height information and the 2D image coordinates; the last step is to get the final 3D image by combining the obtained 3D images of all subapertures. The results of point target simulation indicate that the 3D information (both amplitudes and positions) are well reconstructed. At the same time, the processing results of backhoe data simulated by the Xpatch software show that the outline of the 3D structure is also well reconstructed although the available data corresponding to the depressing angles are not as good as expected.

Signal variation caused by motions along the lift shaft in a campus environment and on board a ship is compared. The guiding effect is common for both lift shafts, and the variation in amplitude of the guided signals is more significant for the lift shaft with larger dimensions. Unlike the lift shaft within the campus, the ship with its lift shaft forms a `waveguide within waveguide' structure. Therefore, the reflected signals within the ship enclosure outside the lift shaft are significantly affected by the motion along the lift shaft. Due to the difference in the degree of the signal variations in these two environments, the rms delay spread is found to be closely related to the lift door status and the lift car position in the campus environment, whereas it is not significantly affected by the motions along the lift shaft in the ship environment. From the statistical study and comparison of the signal variations in the two environments, the Weibull probability density function is found to be the most suitable model to describe analogous waveguide channels such as the lift shaft and the ship enclosure.

In this paper we present a modification to the QHA whereby a gap is introduced at the current minima points at the centre of the helical sections of the QHA. The linear and rotational movement between the two halves of the QHA against each other is optimised to get current distribution, so that when tilted 90°, it generates omnidirectional radiation pattern required for land communications in addition to hemispherical radiation pattern for space mode which is obtainable in conventional configuration. This makes it possible to use the single antenna for both terrestrial and satellite communications. The simulated results are validated by experimental measurements.

Multi-beam antenna arrays have important applications in the field of communications and radar. The reconfigurable design problem is to find the element in a sector pattern main beam with side lobes. The same excitation amplitudes applied to the array with zero-phase should be in a high directivity, low side lobe pencil shaped main beam. This paper presents a new method of designing a reconfigurable antenna with quantized phase excitations using an improved artificial bee colony, called IABC. Compared with subsequent quantization, experimental results indicate that the performance of the discrete realization of the phase-excitation value can be improved.

In this paper, new microstrip bandstop filters with single band, dual-band and tri-band by using U-shaped defected ground structures are presented without the assistance of coupled lines or certain resonators, and the application of DGS is developed. The proposed bandstop filters have good performances of low loss, multi-band operation, transmission zeros which improve the filter frequency selectivity, and miniaturization because of the cascade of DGS and minimum defected patterns which reduce the circuit size. The new designs are demonstrated by measurement.

In this article, a genetic algorithm (GA) is employed to the design of low radar cross section (RCS) patch antennas. Combined with the high frequency simulation software (HFSS) for antenna simulations, the GA performs the optimization of geometric parameters. In order to reduce the RCS while holding the satisfying radiation performance of antennas, the radiation model and scattering model are respectively calculated. The combination of proportionate selection and elitist model for the selection strategy is used to speed up the convergence of the GA. Two-point crossover is adopted to accelerate the converging speed and results in more fit individuals. Moreover, the whole design procedure is auto-controlled by programming the VBScript in the HFSS. Two examples of low RCS slot antennas are provided to verify the accuracy and efficiency of the proposed method.

We consider a topological derivative based imaging technique for non-iterative imaging of small and extended perfectly conducting cracks with Dirichlet boundary condition. For this purpose, we introduce topological derivative imaging function based on the asymptotic formula in the existence of narrow crack. We then mathematically analyze its structure in order to investigate why it yields the shape of crack(s). Analyzed structure gives us an optimal condition to get a better image of them. Various numerical experiments support our analysis.

In this paper, a surface micromachined microwave tunable low pass filter, consisting of tunable shunt capacitors and series inductors, has been realized. The filter exhibits insertion loss of less than 1 dB (up to 10 GHz), stop band attenuation of 20 dB at 20 GHz, and cut-off frequency is changed to 8 GHz with the application of DC actuation voltage in the structure. The filter has an overall dimension of 5.5 mm x 2 mm. The characteristics of tunable filter are investigated with and without packaging.

A novel System-on-Package (SoP) implementation is presented for a transmitter (TX) module which makes use of electromagnetic coupling between the TX chip and the package antenna. The TX chip is realized in 0.13 μm CMOS process and comprises an on-chip antenna, which serves as the oscillator's inductor as well. The TX chip is housed in a Low Temperature Co-fired Ceramic (LTCC) package with a patch antenna. The on-chip antenna feeds the LTCC patch antenna through aperture coupling, thus negating the need for RF buffer amplifiers, matching elements, baluns, bond wires and package transmission lines. This is the first ever demonstration of wireless-interconnect between on-chip and package antennas which increases the gain and range of the TX module manyfold with respect to the on-chip antenna alone. Though the range of the TX SoP increases considerably, power consumption remains the same as that of the TX chip only. A simple analytical model for the new wireless-interconnect has been developed which helps determine the optimum position of the chip with respect to the aperture in the ground plane.

We have built Fabry-Pérot resonators based on microstructured silicon and a liquid crystal. The devices exhibit tuning of the resonance peaks over a wide range, with relative spectral shifts of up to Δλ/λ = 10%. In order to achieve this substantial spectral shift, cavity peaks of high order were used. Under applied voltages of up to 15 V, a variation in the refractive index of the nematic liquid crystal E7 from Δn_LC = 0.12 to Δn_LC = 0.17 was observed. These results may have practical applications in the near-, mid and far-infrared range.

In order to detect a buried object quickly and accurately, a fast radar imaging method is presented in this paper. At first, complex backscatter data are computed by using propagation-inside-layer expansion combining the forward and backward method (PILE + FB). Then, a conventional synthetic aperture radar (SAR) imaging procedure called back projection method is used to generate 2-D image. The random rough surface with Gauss spectrum is used to simulate the ground. Tapered incident wave is chosen to reduce truncation error. Because backscatter data are computed by fast numerical method, this method is proper for rough surface with any parameters with a buried complex object, which is very useful for realistic object detection.

Detecting an on-the-ground object is a subject of interest for use in some applications. Foreign Object Detection (FOD), which is an important issue in aviation safety, is a possible application. In this way, radar imaging, has several inherent advantages over other on-the-ground object detection techniques. This paper will introduce a ground-based Circular Synthetic Aperture Radar, which detects and localizes various objects, based on their reflection properties of microwaves. Here, wideband Linear Frequency Modulated (LFM) chirp pulses are employed for the transmission and reception of reflection pulses, both to and from the object under test. Once the pulses are received by the radar, a processing algorithm (proposed later in this paper) is executed to confirm detection. In order to verify the validity of the model, a prototype was developed and a series of field experiments was carried out. The results show that the proposed system has the ability to detect and localize on-the-ground objects with dimensions as small as 2 cm high and 1 cm diameter, located several metres away. Furthermore, the resolution of the system was analysed and results indicate that the system is capable of distinguishing multiple objects in close proximity to each other, which therefore, makes it suitable for FOD applications by some small modifications.

This paper presents a new range Doppler algorithm (RDA) for bistatic synthetic aperture radar (SAR) processing in a general configuration based on a bistatic point target reference spectrum: the improved extended Loffeld's bistatic formula (ILBF). The ILBF spectrum is proved to be comparably accurate with the spectrum derived using the method of series reversion (MSR). Based on the expansion of the ILBF spectrum, a new bistatic RDA is developed to process the azimuth invariant and variant bistatic SAR data. Compared with existing bistatic RDA, the new algorithm has a simpler formulation and is able to cope with moderate or high squint bistatic SAR data. The simulated data in the azimuth invariant and variant bistatic configurations are used to validate the new algorithm.

It is well-known that, at low frequency, far-field RCS can be measured using a suitable implementation such as outdoor range or large anechoic chamber. The aim of this paper is to propose a new algorithm to predict RCS from near-field measurements. The comparison between RCS values obtained from the proposed method and those obtained from direct far-field values shows a good agreement between the two results.