Assessing the Intrinsic Radiation Efficiency of Tissue Implanted UHF Antennas

Dielectric loss occurring in tissues in close proximity to UHF implanted antennas is an important factor in the performance of medical implant communication systems. Common practice in numerical analysis and testing is to utilize radiation efficiency measures external to the tissue phantom employed. This approach means that radiation efficiency is also dependent on the phantom used and antenna positioning, making it difficult to understand antenna performance and minimize near-field tissue losses. Therefore, an alternative methodology for determining the intrinsic radiation performance of implanted antennas that focuses on assessing structural and near field tissue losses is presented. The new method is independent of the tissue phantom employed and can be used for quantitative comparison of designs across different studies. The intrinsic radiation efficiency of an implant antenna is determined by assessing the power flow within the tissue phantom at a distance of at least λg/2 from the radiating structure. Simulated results are presented for canonical antennas at 403 MHz and 2400 MHz in homogeneous muscle and fat phantoms. These illustrate the dominance of propagating path losses in high-water content tissues such as muscle, whereas nearfield dielectric losses may be more important in low-water tissues such as fat due to the extended reactive near-field

Propagation Characteristics of Groove Gap Waveguide Below and Above Cutoff

(c) 2015 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.Recently, gap waveguides have been shown as a potential alternative to convenational waveguides in the millimeter-wave band. Until now, groove gap waveguide (GGW) has been studied through direct correspondence with rectangular waveguide with the same physical dimensions. However, there have been observed differences in the above cutoff propagation characteristics between these two waveguide types. Furthermore, the behavior of GGW below cutoff remains unknown. This work presents a discussion of both below and above cutoff propagation characteristics of GGW, and introduces a simple model that explains the observed GGW behavior and establishes well its propagation characteristics. Two thru-reflect-line calibration kits have been manufactured, and the measurements have good agreement with the proposed analysis model results.This work was supported by the Spanish Ministerio de Economia y Competitividad under Project TEC2013-47360-C3-3-P and Project TEC2013-47037-C5-1-R and by the Spanish Ministerio de Educacion under FPU Research Fellowship Program AP2010-4227.Berenguer Verdú, AJ.; Fusco, V.; Zelenchuk, DE.; Sánchez-Escuderos, D.; Baquero Escudero, M.; Boria Esbert, VE. (2016). Propagation Characteristics of Groove Gap Waveguide Below and Above Cutoff. IEEE Transactions on Microwave Theory and Techniques. 64(1):27-36. https://doi.org/10.1109/TMTT.2015.2504501S273664

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Architecture Abstract This paper proposes a hybrid scanning antenna architecture for applications in mmwave intelligent mobile sensing and communications. We experimentally demonstrate suitable Wband leaky-wave antenna prototypes in substrate integrated waveguide (SIW) technology. Three SIW antennas have been designed that within a 6.5% fractional bandwidth provide beam scanning over three adjacent angular sectors. Prototypes have been fabricated and their performance has been experimentally evaluated. The measured radiation patterns have shown three frequency scanning beams covering angles from 11 to 56 degrees with beamwidth of 10±3 degrees within the 88-94GHz frequency range. Keywords Millimeter-wave mobile sensing and communications· W-band antennas· Leaky wave antennas