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This paper describes the use of two-dimensional (2-D) pattern measurements as a tool for evaluating new antenna configurations for reducing power absorbed in the head. The estimation is from comparisons of the total power in measured cuts of the power pattern in a plane containing the head (the principal cut) for various handheld antenna configurations. For the estimate to be reliable, the power in the cuts should be proportional to the total radiated power. In practice this may not always be the case, but useful results for guidance of antenna design can still be obtained. Configurations with parasitic reflecting elements for directing the power away from the head are demonstrated to be effective in reducing the absorbed power in the head. The results are consistent with those from existing forward differences in the time domain (FDTD) analysis for directive antennas. The resulting directive patterns are more efficient and so the in situ terminal can be expected to have an improved performance in a homogeneous multipath environment.

Revisions to the formula for secondary emission presented in a previous paper are suggested in relation to higher voltage applications. The revisions include the separation of the ksv and ksdelta smoothness factors for V and delta, assigned a 1.0 default value. This applies to typical dull srufaces in conventional working tube environments. Lower values are best for roughened surfaces while higher values are suited to smooth and oxide-free surfaces.

A frequency-reconfigurable microstrip patch antenna is implemented using a stretchable silicone TC5005 substrate. The stretchable patch is fabricated by injecting liquid metal alloy Galinstan into a square reservoir fabricated in the silicone elastomer substrate. An aperture-coupled feeding method is presented to enhance the strain by separating the fixed feed element from the stretched radiating element. The implemented prototype is demonstrated to be stretchable by a strain of up to 300% (and the material has the potential for more). The electrical length of the patch antenna varies with the stretching, and we demonstrate frequency tuning from 1.3 to 3 GHz. A maximum radiation efficiency of 80% is measured for the antenna. The fabrication process of the antenna system and experimental results for impedance and radiation pattern are presented. [ABSTRACT FROM AUTHOR]

A new blind channel estimation technique is presented for uncoded orthogonal frequency-division multiplexing (OFDM) systems. Instead of using pilots to sound the channel, a decision algorithm first makes primary estimates of the data symbol for each subcarrier based on a constrained linear minimum mean square error (MMSE) criterion. Then, these estimates are applied to optimal MMSE channel estimation. The technique requires only one value from the time–frequency correlation of the channel transfer function. Performance is evaluated by simulation so that comparison can be made with known optimal coherent/differential detection. Compared with known decision-directed Kalman-based estimation and two pilot-aided OFDM schemes (block pilots and comb pilots), the presented technique performs better for regions with mid to high signal-to-noise ratios (SNRs). Its robustness to the time variation of the channel is also quantified by simulation, showing only small degradation in performance relative to the quasistatic case of wireless local area network (WLAN) systems. Finally, the impact of covariance assumptions in the channel modeling is quantified using simulation, offering a feel for the performance with mismatch between the channel model and the receiver assumptions. [ABSTRACT FROM PUBLISHER]

The theory of propagating waves near a surface is reviewed with an eye to gain insight into the mechanisms involved, and to provide analytical-based models, for power-efficient on-body propagation. The Zenneck wave, and in particular the Norton wave, are appraised as candidate mechanisms for the propagation. For flush-mounted ("band aid") antennas, desired for on-body sensors, the Norton wave is the only direct propagation mechanism between the sensors. The Norton wave fits very well to simulation results presented here, and comparisons are also made with available published physical experiments, although these measurements typically feature the optical paths of elevated, or non-flush, antennas. [ABSTRACT FROM AUTHOR]

The article discusses various reports published within the issue, including one on antenna design and characterization, and another on innovations in MIMO systems.

In most modern textbooks on antennas, it is stated that receiving antennas scatter as much as they absorb under matchedload conditions. This is incorrect, as was shown 50 years ago. The reason for this discrepancy is an apparently incorrect use of the equivalent circuits. In this tutorial paper, a simple example of a two-element Yagi antenna and a test dipole in the far field is analyzed for transmission, reception, and scattering, through the use of the symmetric impedance matrix. It is shown that the correct equivalent circuit for the scattering case is more complicated, owing to the existence of more sources than in the transmitting case. Through a numerical example, it is also shown that the scattered power may be larger, equal to, or smaller than the absorbed power. [ABSTRACT FROM AUTHOR]

In a recent paper, Blumenfeld [1] outlined the continuous modeling approach to the description of the joint distribution of homes and workplaces in a city. In this note, the circularly symmetric form of the quarivariate normal model is further analyzed, and distributions of the desire line lengths and other variables are derived. [ABSTRACT FROM AUTHOR]

New microelectronic fabrication techniques enable the creation of high-performance on-chip antennas by using new or modified antenna designs. A system's performance is normally improved by a high antenna gain which requires an electrically large aperture typically supporting an array. Consequently, array design is of particular interest for high-performance on-chip systems. The feed for an array is a challenge because it must be low loss while extending over the large aperture. A solution is the waveguide slot array which integrates antenna elements with a low-loss feeding structure. This study presents a new slot array structure which is motivated by advanced microelectronic fabrication. It comprises a triangular waveguide as the array feed, and slots for the elements. This allows fabrication by a self-assembly technique which lithographically controls the shape of a three-dimensional structure. This process is complementary metal-oxide-semiconductor compatible, enabling radio and radar system-on-chip solutions. For production, the low mass of the structure makes it inherently robust, although hermetic packaging with a radio window akin to UV-erasable eproms would be required (not included here). The design concept is demonstrated with a physical prototype operating at a low frequency. The fabrication concept is demonstrated by a physical onchip prototype, and its performance is assessed by simulation. [ABSTRACT FROM AUTHOR]

A Rice factor (K) estimator is described which uses simple operations on the phase of the well-defined Rice channel. Multiple receive channels, such as used in MIMO communications, enable spatial sampling which enhances the accuracy. For an example configuration of four uncorrelated receive antennas with a ten wavelength linear trajectory in isotropic scattering, the estimator works well for small to medium K (i.e., K \lesssim7). Limitations of the estimator include an assumption of isotropic scattering and that the angle-of-arrival of the dominant component is fixed and cannot be perpendicular to the mobile trajectory. [ABSTRACT FROM PUBLISHER]

Presents a study which discussed a method for evaluating antenna diversity systems with an example of a handset using antennas in indoor mobile communication. Issues on antenna matching; Conclusion.

Examines the empirical justifications for the lognormal, Rayleigh and Suzuki probability density functions in multipath fading channels. Statistical descriptions of fading processes; Quantification of the rate of convergence of the central limit theorem (CLT) for the lognormal and Rayleigh distributions; Conclusion.

A micro-electro-mechanical systems fabrication process has been developed to create self-assembled on-chip high efficiency antennas. The self-assembly creates out-of-plane antenna structures, which can have good radiation efficiency on low resistivity substrates. The structural material is SU-8 and the self-assembly curvatures are defined lithographically. The losses are reduced by having the antennas, transmission lines, and an isolating conducting ground plane placed on top of the supporting (and lossy) dielectric layer. The fabrication process includes deposition of a thick metal layer, which envelopes the antenna structure. This paper presents the fabrication process for a self-assembled monopole antenna, and numerical and physical experiments for the antenna pattern characteristics. The physical measurements show a realized gain (includes mismatch loss) of −1.29 dBi at 59 GHz. [ABSTRACT FROM AUTHOR]

Parasitic elements are rotated around a monopole on a groundplane to attain rotated patterns for diversity. A parametric study of the geometry using simulation is used to demonstrate how the parasitic rotation can attain uncorrelated patterns in an idealized multipath propagation environment. Various parasitic designs such as wires and loops, and other shapes can be used for realizing a low- or medium-gain pattern, and high bandwidth including multiband operation. A proof-of-concept prototype is implemented with the rotation using an electro-active polymer actuator and a triangular parasitic element, and physical experiments confirm low correlations (inner products) between the patterns. [ABSTRACT FROM PUBLISHER]

A beam steering antenna is described which uses bending parasitic elements controlled by bending fluidic actuators (BFAs). The structure is a monopole antenna surrounded by four parasitic elements on a groundplane. The BFAs are controlled by linear controllers located below the groundplane. In this way, the parasitic elements comprise BFAs and the action of bending them away from the monopole to alter the mutual impedances is analogous to the reactance variation of switched parasitic antenna. When a parasitic element is not bent, it can act as a reflector or director for low-gain beam formation, while the other parasitic element is bent away from the monopole and hence not affecting the beam. Two configurations have been realized with different numbers of bent parasitic elements, and experimental results for these configurations are presented. Patterns with low cross correlations can be attained while keeping the return loss below a reasonable limit. [ABSTRACT FROM AUTHOR]

We present two new fisheye image datasets for training object and face detection models: VOC-360 and Wider-360. The fisheye images are created by post-processing regular images collected from two well-known datasets, VOC2012 and Wider Face, using a model for mapping regular to fisheye images implemented in Matlab. VOC-360 contains 39,575 fisheye images for object detection, segmentation, and classification. Wider-360 contains 63,897 fisheye images for face detection. These datasets will be useful for developing face and object detectors as well as segmentation modules for fisheye images while the efforts to collect and manually annotate true fisheye images are underway., (© 2019 The Author(s).)