Minimization of power loss in the tuning circuits of frequency-tunable small resonant antennas, such as microstrip patches, is studied. First, the frequency shift and the associated power loss in certain tuning circuits are theoretically calculated based on approximate circuit models of fairly narrow-band resonant antennas. By investigating the ratio of frequency shift and loss, an optimal conf...

In this paper, a novel method to model helical antennas working in the normal mode, as well as helix-monopole antennas with finite-difference time-domain (FDTD) code is presented. This method is particularly useful to model antennas used for personal wireless communication handsets, where the fairly small dimensions of the helical antennas with respect to wavelength and the grid cell size do no...

Current methods of designing and optimizing antennas by hand are time and labor intensive, limit complexity, and require significant expertise and experience. Evolutionary design techniques can overcome these limitations by searching the design space and automatically finding effective solutions that would not ordinarily be found. In recent years, evolutionary algorithms have shown great promis...

In this article the calculation, along with practical examples of near and far fields of acoustic antennas are presented. Knowing the near and far fields is important because the radiation patterns and physical measurements of the antennas depend on them. These antennas designed for measurements in air consist of transducers in flexural vibration, which give the best possibility to match acoust...

But first concerning controversies there is also a controversy concerning the use or non-use of baluns, and which balun to use. Since many antenna types are balanced, and present day HFTPA’s are unbalanced, and, since the preferred method of feeding antennas is to use coaxial cable, rather than 2-conductor balanced transmission line, a balun should, often must be used in the overall antenna sys...

These three quantities can be derived from expressions in antenna theory textbooks [1, 2]. Note that the radiation resistance increases as the fourth power of the ratio of the loop dimension (e.g., radius) to the wavelength, which is the same as the fourth power of the loop dimension times frequency. The loss resistance, arising from the skin effect, only increases as the square root of the fre...

Recently, wearable wireless devices or terminals have become hot a topic not only in research but also in business. Implantable wireless devices can temporarily be utilized to monitor a patient’s condition in an emergency situation or to identify people in highly secured places. Unlike conventional wireless devices, wearable or implantable devices are used on or in the human body. In this sense...