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This letter presents an impressive optimization method for determining the optimal model hyperparameters of a deep neural network (DNN) targeted to model the characteristics of antennas. In this paper we propose an innovative approach of efficient yield analysis for modeling and sizing antennas. It is based on the long short-term memory (LSTM) DNN aiming to forecast the extended frequency responses, where various stochastic methods are applied for determining the optimal hyperparameters while training a DNN. Among the various methods, the one which models the antenna accurately in terms of input scattering parameter, gain, and radiation patterns is the winner. The proposed method is compact and addresses the problem of heavy reliance to the designer experience in determining the hyperparameters. Additionally, forecasting the future frequency responses of the antenna reduces the designers effort substantially in measuring large frequency band; hence, measuring whole frequency band would not be needed. For validating the effectiveness of the proposed method, the fabricated two element antenna array is used for modeling where the results demonstrate that the Thompson sampling (TS) algorithm can determine optimal hyperparameters with minimum error in comparison with other reported stochastic methods leads to predict the future frequency band accurately. IEEE

The non-redundant sampling representations of electromagnetic fields and the image principle are properly applied in this work to develop an effective probe-compensated spherical near-field to far-field (NFTFF) transformation, which makes use only of the NF data measured over the upper hemisphere, due to the presence of an infinite perfectly conducting ground plane. According to these representations, the considered antenna under test (AUT) and its image are assumed as enclosed in a surface consisting of a cylinder ended in two half-spheres. Then, an efficient 2-D optimal sampling interpolation scheme is used to reconstruct the NF data required by the standard spherical NFTFF transformation from the NF samples collected over the upper hemisphere and from those properly synthesized from these last over the lower one. Numerical examples are shown to assess the effectiveness of the developed non-redundant spherical NFTFF transformation.

The characteristics of the intra-body propagation channel between implanted antennas are highly application dependent. Measurements of the forward path gain between identical implant antennas within two multi-layered tissue mimicking liquid phantoms were used to investigate the nature of the intra-body channel at 2.38 GHz. One of the antennas was held in fixed locations in the phantoms and a robotic positioner with millimeter accuracy was used to vary the second antenna's position. The results show that the shortest line-of-sight path is not always dominant and depending on the particular geometry of material layers and their dielectric properties other propagation paths may also be important. This highlights the importance of careful system design in intra-body networks as the link budget between implanted nodes may need to consider alternative propagating paths, depending on the application scenario.

The use of $\ell_{p}\ (0 norm minimization will improve the performance of array diagnosis provided that the issue of local minima associated to its non-convex nature is properly handled. In order to figure out this drawback, a hybrid diagnosis method of random perturbation-convex local minimizer is addressed in this paper. Theoretical analysis and numerical simulations indicate the effectiveness of the proposed method to overcome this deficiency and outperforms the standard $\ell_{1}$ norm minimization in terms of locating broken elements with a smaller number of far-field measurements. Although it suffers from a higher computational burden, the trade-off between an accurate diagnosis with high probability and the computational time appears to be acceptable, suggesting that the proposed method can be a suitable candidate used to improve the performance of array diagnosis.

The recently proposed near-field/far-field (NF/FF) transformation technique with spherical spiral scan, which, by properly exploiting the non-redundant representations of electromagnetic fields and the unified theory of spiral scans for non-volumetric antennas under test (AUTs), allows one to properly account for a mounting of an elongated AUT in offset configuration, is here experimentally validated. It is based on the prolate spheroidal source modelling and requires the same number of NF data as in the case of an onset AUT mounting, depending such a number only on the surface of the adopted AUT modelling. Moreover, it makes use of an efficient 2-D optimal sampling interpolation formula to recover the NF data needed to perform the standard NF/FF transformation, whose amount is related to the radius of the minimum sphere enclosing the AUT and centred at the scanning sphere centre. As it will be shown, the experimental results will further confirm the practical effectiveness of the proposed technique.

A laboratory assessment of a recently proposed spherical near-field to far-field (NF-FF) transformation technique for a long antenna under test (AUT) mounted in offset configuration, which requires an amount of NF measurements minimum and equal to that needed for the onset mounting, is provided in this work. The interest for this technique is due to the fact that sometimes, for practical limitations, it can be impossible an onset mounting, where the AUT center and the scanning sphere one coincide. In this case, the amount of NF measurements and the corresponding acquisition time required by the traditional spherical NF-FF transformation can remarkably raise, owing to the minimum sphere rule. Instead, in the proposed NF-FF transformation, the massive data necessary for the traditional one are efficiently recovered from the measured nonredundant samples using an optimal sampling interpolation formula, got by suitably exploiting the nonredundant sampling representations and modeling the AUT by a prolate spheroid. Some laboratory results, fully confirming the efficacy of such a nonredundant NF-FF transformation from the practical viewpoint, are reported.

Ekti, Ali Rıza (Balikesir Author), Digital revolution and recent advances in telecommunications technology enable to design communication systems which operate within the regions close to the theoretical capacity limits. Ever-increasing demand for wireless communications and emerging numerous high-capacity services and applications mandate providers to employ more bandwidth-oriented solutions to meet the requirements. Trend and predictions point out that marketplace targets data rates around 10Gbps or even more within the upcoming decade. It is clear that such rates could only be achieved by employing more bandwidth with the state-of-The-Art technology. Considering the fact that bands in the range of 275GHz-3000GHz, which are known as Terahertz (THz) bands, are not allocated yet for specific active services around the globe, there is an enormous potential to achieve the desired data rates. Although THz bands look promising to achieve data rates on the order of several tens of Gbps, realization of fully operational THz communications systems obliges to carry out a multidisciplinary effort including statistical propagation and channel characterizations, adaptive transceiver designs, reconfigurable platforms, advanced signal processing algorithms and techniques along with upper layer protocols equipped with various security and privacy levels. Therefore, in this study, several important statistical parameters for line-of-sight (LOS) channels are measured. High resolution frequency domain measurements are carried out at single-sweep within a span of 60GHz. Impact of antenna misalignment under LOS conditions is also investigated. By validating exponential decay of the received power in both time and frequency domain, path loss exponent is examined for different frequencies along with the frequency-dependent path loss phenomenon. Furthermore, impact of humidity is also tested under LOS scenario. Measurement results are presented along with relevant discussions and future directions are provided as well. © 2017 IEEE.

in this letter, a new microstrip antenna for UWB applications is suggested. The antenna is able to filter both of the interference frequency bands of WiMAX and WLAN. The antenna consists of two radiating stubs, a partial ground, and a feed-line. In the configuration, by etching an inverted T- shaped slot on the ground plane, extra resonance is excited, thus broad impedance bandwidth can be obtained. The measured results exhibits that the antenna can cover the bandwidth from 2.7 to 13.0 GHz for VSWR≤ 2 excluding the rejected bands from 3.0 to 3.7 GHz and from 4.9 to 6.0 GHz.

The use of biosensors attached to the body for health monitoring is now readily accepted, and the merits of such systems and their potential impact on healthcare receive much attention. Wearable medical systems used in clinical applications to monitor vital signs must be comfortable to wear, yet have robust performance to ensure reliable communications links. Additionally, and vital to the success of these innovations, is that these solutions are disposable to avoid risk of patient infection and this means that they must be ultra-low cost. Antennas optimized for printing using conductive inks offer new exciting advances in making a truly disposable solution.

A diversity antenna system with antennas embedded in rear view mirrors of a vehicle is proposed for satellite digital audio radio system. Antenna diversity is needed because hidden antennas exhibit limited capability and composite body vehicles have poor reception due to no ground plane availability. Pattern gain diversity achieved with the proposed system is proven with on-vehicle antenna simulations and gain measurements. Selection combining diversity receiver architecture is also proposed and the system is tested in real time under two fading scenarios: weak satellite signal in dense foliage and multipath terrestrial environment with frequent satellite blockages. In both cases, the diversity system outperformed the reference antenna system with less mutes times (0.6% versus 0.8% in multipath, 0.1% versus 0.25% in dense foliage) and Reed-Solomon block errors (1.75% versus 2.18% in multipath, 0.87% versus 1.18% in dense foliage). The proposed rear-view mirror location is ideal for minimum signal degradation compared to windshield, backlite, and dashboard antenna installations. © 1963-2012 IEEE.

Conventional antenna radiation efficiency measurement techniques, such as the Wheeler cap, are generally narrow-band and, thus, well suited for resonant antennas. In this work, the Johnston-Geissler (J-G) method based on the Wheeler cap principle is used in a wide frequency range. First, a good agreement between measurement and simulation in an ultrawide frequency band is shown on a straight wire monopole antenna with different attenuators emulating antenna losses. Then, this technique is used to measure the radiation efficiency of several ultrawideband (UWB) antennas.

We present an approach for the synthesis of array-based generalized plane wave synthesizers (GPWSs) to generate plane waves in the quiet zone (QZ) region of a test-range. The method allows flexibly accounting for disconnected QZ domains and for disconnected panels of radiators. It permits dimensioning, locating and orienting the panels. By optimizing the singular values behavior (SVB), corresponding to a singular value decomposition (SVD) of the relevant linear, parametric radiation operator, it further enables determining the proper locations of radiators and QZ grid points (enforcing the synthesis constraints) to mitigate the problem ill-conditioning of determining the radiators' excitation coefficients. A proper strategy is also employed to control the overall computational burden. The validity and performance of the method are verified following a numerical analysis, by choosing examples aimed at enlightening the key points of the problem.