This paper presents a comprehensive location scheme in a rich multipath environment. It is based on the estimation of the distance between two wireless nodes in line-of-sight (LOS) from the best statistical estimator of the round-trip time (RTT), assuming a linear regression as the model that best relates this statistical estimator to the actual distance. As LOS cannot be guaranteed in an indoor environment, the effect of non-line-of-sight (NLOS) is mitigated by a two-step correction scheme. At a first step, the severe NLOS error is corrected from distance estimates applying the prior NLOS measurement correction (PNMC) method. At a second step, a new multilateration technique is implemented together with received signal strength (RSS) information to minimize the difference between the estimated position and the actual one. The location scheme coupled with measurements in a real indoor environment demonstrates that it outperforms the conventional time-based indoor location schemes using neither a tracking technique nor a previous calibration stage of the environment and no need for time synchronization between wireless nodes.

Development of theory and experiments to retrieve Green's functions from cross correlations of recorded wave fields between two receivers has grown rapidly in the last seven years. The theory includes situations with flow, mechanical and electromagnetic disturbances and their mutual coupling. Here an electromagnetic theory is presented for Green's function retrieval from cross correlations that incorporates general bianisotropic media, which is the most general class of linear media. In the presence of dispersive non-reciprocal media, the Green's function is obtained by cross correlating the recordings at two locations of fields generated by sources on a boundary. The only condition for this relation to be valid is that the medium is non-dissipative. The principle of bianisotropic Green's function retrieval by cross correlation is illustrated with a numerical example.

Using cylindrical harmonics and Fourier series, a new integral equation formulation is derived for perfectly conducting 2D scattering problems. This new integral equation is based on the fact that, all of the electric and magnetic field components are zero inside a perfect electric conductor. The incident and scattered fields are expressed in the cylindrical coordinate system with respect to a common origin inside the scatterer, using the addition theorem for Bessel and Hankel functions. The resulting electric or magnetic field is set equal to zero for all the points inside the largest cylinder that is contained in and tangent to the surface of the scatterer. As a result the field point variables are eliminated from the integral equation and only the source points are present in this formulation. Therefore the size of the problem is reduced considerably. A dramatic improvement in the computation speed is seen compared to the classical method of moments. TE and TM scattering problems are considered and the integral equation formulation is derived and solved for both cases.

The objective of this paper is all-angle artificial magnetic conductor, i.e., artificial magnetic conductor that has stable magnetic-wall effect with respect to the incidence angle. Furthermore, we seek for a design that would be easy for manufacturing. In order to achieve this we use grounded uniaxial material slabs and we do not constrict ourselves to naturally available materials. Instead, we assume that the desired parameters can be synthesized using the emerging artificial electromagnetic materials. It is found that it is possible to have an all-angle magnetic-wall effect for both TE and TM polarization. Especially for the TM fields the structure would be easily manufacturable. The proposed structure has similar appearance as more well-known artificial impedance surfaces, but the design parameters and the physical properties behind the magnetic wall effect are novel. The performance of the proposed artificial magnetic conductor is verified with numerical simulations. This paper introduces a new approach how to obtain a magnetic-wall effect. It is possible to use this this approach also together with other ways of obtaining the magnetic-wall effect for dual-band operation.

For maneuvering target tracking, we propose a novel grey prediction based particle filter (GP-PF), which incorporates the grey prediction algorithm into the standard particle filter (SPF). The basic idea of the GP-PF is that new particles are sampled by both the state transition prior and the grey prediction algorithm. Since the grey prediction algorithm is a kind of model-free method and is able to predict the system state based on historical measurements other than establishing a priori dynamic model, the GP-PF can significantly alleviate the sample degeneracy problem which is common in SPF, especially when it is used for maneuvering target tracking. Simulations are conducted in the context of two typical maneuvering motion scenarios and the results indicate that the overall performance of the proposed GP-PF is better than the SPF and the multiple model particle filter (MMPF) when the tracking accuracy, computational complexity and tracking lost probability are considered. The performance improvements can be attributed to that the GP-PF has both model-based and model-free features.

Present paper utilizes the time evolution for estimating the soil moisture and vegetation parameter with Radar remote sensing data. For this purpose, vegetation ladyfinger has been taken as a test field and experimental observations have been taken by bistatic scatterometer at X-band in the regular interval of 10 days for both like polarization (i.e., Horizontal-Horizontal, HH-; Vertical-Vertical, VV-) and at different incidence angles. At this interval, all the vegetation parameters and scattering coefficient have been recorded and computed. Three similar types of field of size 5 x 5 m have been especially prepared for this purpose. The observed data is critically analyzed to understand the effect of incidence angle and polarization effect on scattering coefficient of the ladyfinger. It is observed that VV-polarization gives better result than HH-polarization and incidence angle 55^ο is the best suited to observe composite effect of vegetation ladyfinger biomass (Bm) and vegetation covered soil moisture at X-band. This analysis is further used for retrieval of soil moisture and biomass of ladyfinger using Neural Network. The important aspect of the retrieval algorithm is that it includes the time evolution. The retrieval results for soil moisture and Bm are in good agreement with the actual values of the soil moisture and biomass.

Two new triple band small size composite-resonator microstrip antenna configurations for wireless communications are presented in this paper. The proposed antennas, each is built of three resonant elements. Two types of compact short-circuited resonators are used; stepped impedance and quarter-wave resonators. The design procedure based on composing the antenna resonators is straightforward and can be applied to design any triple band antenna at three pre-specified bands using simple relations and design curves. The resonator integration has been performed to maintain single feed, reduce the overall antenna size, and preserve the quality-performance at each band. The two designed antennas are simulated, optimized, and realized on RT-Duroid substrate to verify the concept. Simulation and experimental results are in good agreement and demonstrate the performance of both triple band compact antennas.

In this paper, a quasi-optical Bessel resonator (QOBR) for generating approximations to Bessel-type modes at millimeter wavelengths have been designed and analyzed. A design approach is based on the quasi-optical techniques. In order to analyze the designed QOBR rigorously, a new method based on iterative Stratton-Chu formula (ISCF) is developed from the classical Fox-Li algorithm. And its validity is demonstrated. Numerical results reveal that at the output plane the intensity distributions of the Bessel-type modes of the QOBR are modulated by a bell-shaped envelope, and their phase patterns have a block-shaped profile except slight distortion on the edges of the element due to aperture diffraction. The effect of varying the parameters of the designed QOBR on the relevant output characteristics is also examined in our study.

A microwave method has been proposed for accurate complex permittivity measurement of thin dielectric materials partially filling the waveguide. The method employs propagation constant measurements at two locations of the sample inside its holder. It increases the accuracy of permittivity measurements of similar methods in the literature since it utilizes the measurements of the distances between the inner waveguide walls and sample lateral surfaces instead of directly measuring the sample thickness. It has been validated by comparing the measured complex permittivity of a thin Plexiglas sample by the proposed method with that of the method in the literature.

This paper presents a new design of miniaturized wideband bandpass filter using microstrip hairpin in multilayer configuration for X-band application. The strong coupling required for wideband filter is realized by arranging five hairpin resonators in two layers on different dielectric substrates. Since adjacent resonator lines are placed at different levels, there are two possible ways to change coupling strength by varying the overlapping gap between two resonators; vertically and horizontally. In this paper, simulated and measured result for a wideband filter of 4.4 GHz bandwidth at 10.2 GHz center frequency with fifth order Chebyshev response is proposed. The filter is fabricated on 0.254 mm thickness R/T Duroid 6010 and R/T Duroid 5880 with dielectric constant 10.2 and 2.2 respectively using standard photolithography technique. Two filter configurations based on vertical (Type 1) and horizontal (Type 2) coupling variation to optimize the coupling strength are presented and compared. Both configurations produce very small and compact filter size, at 5.0 x 14.6 mm² and 3.2 x 16.1 mm² for the first and second proposed filter type respectively. The measured passband insertion losses for both filters are less than 2.3 dB and the passband return loss is better than -16 dB for filter Type 1 and -13 dB for filter Type 2. Very small and compact filter is achieved where measured results show good agreement with the simulated responses.

A new microwave method has been proposed for simultaneous broadband and stable complex permittivity and complex permeability determination of magnetic and nonmagnetic materials. The method utilizes complex transmission scattering measurements at different frequencies. For a change in constitutive parameters determination, we considered zero-order and higher-order approximations. We have verified the proposed method from measurements of two medium- and low-loss materials with another method and available reference data in the literature.

A modified particle swarm optimization (PSO) algorithm applied to planar array synthesis considering complex weights and directive element patterns is presented in this paper. The modern heuristic classical PSO scheme with asynchronous updates of the swarm and a global topology has been modified by introducing tournament selection, one of the most effective selection strategies performing in genetic algorithms the equivalent role to natural selection, and elitism. The modified PSO proposed combines the abilities of the classical PSO to explore the search space and the pressure exerted by the selection operator to speed up convergence. Regarding the optimization problem, the synthesis of the feeds for rectangular planar arrays consisting of microstrip patches or subarrays of microstrip patches is considered. Results comparing the performance and limitations of classical and modified PSO-based schemes are included considering both test functions and planar array complex synthesis to best meet certain far-field radiation pattern restrictions given in terms of 3D-masks. Finally, representative synthesis results for sector antennas for worldwide interoperability for microwave access (WiMAX) applications are also included and discussed.

Studies of dual channel, polarisation agile, quad-ridge and octo-ridge feeds suggest that mode degeneracy in multi-ridge structures severely constricts operational bandwidths, for a large range of ridge dimensions. Mode characteristics in dual-ridge, quad-ridge and octo-ridge waveguide are examined in this paper, with a view to identifying both the nature of the degeneracy, and its implications for bandwidth. The results presented have been generated using a full-wave finite element electromagnetic field simulator.

In this paper, a novel multi-band EBG structure is presented. By making slots on Sievenpiper High Impedance Surface(HIS) to increase the inductance and capacitance, the resonant frequency of the EBG structure can be significantly reduced.Transmission line method is used to determine the band-gap of the EBG structure.The simulated and experimental results show that the novel EBG structure can provide multiple band-gap. This proposed EBG can be usefully applied to multiple frequency antennas and low profile antennas.

A bandpass filter (BPF) using CPW combined with microstrip is proposed. The target BPF is composed of two element filters built from combined CPW and microstrip structure. The design of element filter is based on the lumped elements approach with each circuit component built from a CPW or microstrip. In the circuit model, transmission zeros are created by the passband edges to enhance the signal selectivity. The element filter's characteristics are analyzed by the lumped L-C circuit model. Experiment is conducted, and a good agreement is observed between the measurement and simulation.

Wet antenna attenuation during rain events is examined through carrying out simulated rain experiments. These were conducted on the receiving antenna located at Penang, Malaysia. The findings from these experiments are used to estimate rain attenuation data for that path by adjusting the collected data for wet antenna attenuation. This was done for the 1-year period of March 2007 to February 2008 and includes average and worst month cumulative distribution functions. The results of the measurement indicated that the wet antenna effect is a significant attenuator, and should be included in a link budget. The measured attenuation values were 4 dB for the wet feed window and total reflector plus feed window attenuation value of 6.3 dB at 20.2 GHz, at a rain rate of 100 mm/h.

The paper presents the ionospheric effect on the power transmitted by satellite solar power station. Consequently, the Faraday rotation and losses due to ionospheric layer are calculated at 2.45 GHz frequency. It is observed that the fluctuation in the Faraday rotation in day time is found to be the maximum as compared to the night hours and. Loss due to depolarization is found to have the maximum value at noon hours for all the seasons (summer, winter and spring) however, the loss is the highest for summer season as compared to winter and spring season. This is logically correct because the ionization is the highest in summer in comparison to winter which gives rise to maximum electron content and maximum depolarization.

Ultra Wideband (UWB), an impulse carrier waveform, was applied at HF-VHF frequencies to utilize surface wave propagation. Due to the low duty cycle of the pulse, the energy requirements are significantly reduced. UWB involves the propagation of transient pulses rather than continuous waves which makes the system easier to implement, inexpensive and small. The use of surface wave propagation (instead of commercial SHF UWB) extends the communication range. The waveform, transmitter, receiver, modulation and channel characteristics of the novel system design will be presented.

The scattering of electromagnetic plane wave from an artificial object containing thin long perfectly conducting needles embedded in a homogeneous background material is characterized by parameters like positioning, orientations and lengths of needles. Firstly, models of random errors in positioning and orientation of perfectly conducting needles are proposed. Secondly, their effects upon ensemble averaged RCS is analyzed. It is investigated theoretically that increasing error in positioning and orientation of conducting needles reduces ensemble averaged RCS.

Inaccurate range estimates often restrict indoor positioning systems, resulting in a more remarkable drawback when using an already-deployed IEEE 802.11 network. This is the case of the time delay based location system that this paper deals with. The main causes of these inaccuracies are multipath and non-line-of-sight (NLOS) effects. These effects can be solved to a large degree by characterizing arrival times and range estimation errors. For this reason, this paper analyzes multipath and NLOS effects involved in the round-trip time (RTT) discrete measuring process, which is conducted before each range estimate. RTT observations obtained in this process for different real indoor environments provide useful statistical information that allows making the work extendable to other similar scenarios. Moreover, from this statistical information, the nodes in the network can estimate several parameters of the range estimates distribution while performing the location process. These are used to reduce the error caused by multipath components and to predict and correct the NLOS biases produced. In this way, the NLOS error is dynamically estimated and corrected, achieving better results than classical approaches based on static parameters.