Performance of beamforming and mimo technique in an indoor ricean clustering channel

In this paper, we present a hybrid indoor MIMO channel model for predicting the performance of multiple-element antenna system. The model incorporates the wave clustering phenomena and combines the statistical characteristics of clusters with deterministic ray tracing method. The capacity of the MIMO channel is expressed as a function of spatial correlation at both the transmitter and the receiver. The results obtained by using the channel model are compared with measurement results available in the literature. Simulation results verify that the MIMO technique effectively exploits multipath fading. The paper also presents a comparison between MIMO and beamforming techniques in indoor environments

Breast cancer detection in highly dense numerical breast phantoms using time reversal

In this paper we investigate the detection of breast cancer using two-dimensional slices of realistic numerical phantoms employing time reversal microwave imaging. We used maximum-likelihood estimation coupled with time reversal technique to detect and estimate the location of tumor using FDTD based breast phantoms that contain dense fibroglandular tissue clutter. We show that time reversal maximum-likelihood estimation can detect and accurately localize tumors even in highly dense breasts where the dielectric contrast between healthy dense breast tissue and cancerous lesions is quite low without requiring any contrast enhancing agents. © 2013 IEEE

The performance of dual-band CPW-fed printed antennas for wireless body-worn applications

In this paper, we investigate the performance of two dual-band printed CPW-fed antennas, which have C-shaped and T-shaped geometrical shapes, for wireless body-worn applications. The simulated results in reflection coefficient, radiation characteristics and specific absorption rate (SAR) are presented. Copyright 2006 IEICE

A circularly polarized stacked electromagnetically coupled patch antenna

In this communication, we present a high-performance circularly polarized (CP) stacked electromagnetically coupled patch antenna and its subarray at X band. In addition to low boresight axial-ratios, the subarray has measured 10-dB impedance and 3-dB axial-ratio bandwidths of 25.6% and 23.5% respectively as compared to the measured 20.2% and 8.0% for a single element. The mutual coupling for this element is shown to be lower than other reported stacked patch antennas and obtained a gain (> 10 dbic) bandwidth of 23.5%. The calculated antenna efficiency is 89% around center frequency for the single element whereas the subarray has an overall efficiency of >71% (-1.5 dB) over 21% bandwidth

A hybrid boundary condition for robust particle swarm optimization

The particle swarm optimization (PSO) technique is a powerful stochastic evolutionary algorithm that can be used to find the global optimum solution in a complex search space. However, it has been observed that there is a great variation in its performance due to the dimensionality of the problem and the location of the global optimum with respect to the boundaries of the search space. The present paper attempts to resolve this problem by proposing a simple hybrid "damping" boundary condition that combines the characteristics offered by the existing "absorbing" and "reflecting" boundaries. Simulation results on microwave image reconstruction have shown that with the proposed "damping" boundary condition, a much robust and consistent optimization performance can be obtained for PSO regardless of the dimensionality and location of the global optimum solution. © 2005 IEEE

Localization of electromagnetic radiating sources in the near-field of a uniform circular array

In this paper we present a parameter estimation problem for practical electromagnetic signals generated by dipóle antennas positioned close to a receiving antenna of uniform circular array (UCA). The positions (direction of arrival and range) and the radiation characteristics of emitting sources are being estimated using super resolution techniques. We also estimate the time difference of arrival (TDOA) to calculate range by using generalized cross correlation of eigenvectors in the signal sub-space. The technique discussed here may be generalized to define a methodology to localize and characterize the radar imaging techniques and may be applicable to the separation of dielectric layers by reflecting signals. Copyright 2006 IEICE

Experimental investigation of indoor MIMO Ricean channel capacity

We investigate the variation of measured multiple-input multiple-output (MIMO) channel capacity for line-of-sight (LOS) Ricean scenarios inside a typical indoor environment for various transmitter-receiver positions at a center frequency of 2.45 GHz. In order to quantify the effect of LOS component on indoor MIMO performance, an absorber-loaded metal panel was utilized to artificially obstruct the LOS path between the transmit and receive antennas. Our results confirm that MIMO capacity decreases with the increase in the values of Ricean K factor. We have also observed that the variation in channel capacity closely follows the corresponding deviations in root mean square (rms) delay spread of the channel. © 2005 IEEE

Beamspace time reversal maximum likelihood estimation for microwave breast imaging

© 2014 IEEE. We consider maximum likelihood based beamspace time reversal beamforming for breast cancer localization. We reduce the computational burden of maximum likelihood estimation through reduced dimensional beamspace processing. Beamspace processing also provides additional beamspace gain which contributes to suppress strong clutter effects. We collect multistatic scattering fields through FDTD simulation and further process it in beamspace for maximum likelihood based time reversal imaging. The imaging technique is used to localize a small tumor in a dense breast. It is observed that the proposed imaging technique can localize tumors unambiguously even in dense breast phantom

Miniaturized implantable DS-PIFA antenna for biomedical applications

© 2015 ICST. This paper presents an implantable miniaturized planar inverted-F antenna (PIFA) for biomedical applications. We propose small sized PIFA that can operate over 2.45 GHz Industrial, Scientific, and Medical (ISM) band. We have investigated the effect of antenna parameters on resonant frequencies using empirical parametric studies and achieved highly compact PIFA antenna occupies a volume of 92 mm3 with a size of 8.1×7.1×1.6 mm3. Moreover, the effects of the variation of surrounding environment such as skin and fat thickness on the antenna performance are also considered. The impedance characteristics of the proposed antennas are measured using experimental tissue mimicking phantoms. We have also evaluated the calculated Specific Absorption Rate (SAR) by using an indirect thermal method to measure the SAR inside the mimicking phantom