On the Effects of Balun on Small Antennas Performance for Animal Health- Monitoring and Tracking

This paper presents the performance evaluation of a sleeve Balun integration in the design of a flexible loop antenna for wildlife health monitoring and tracking applications. To verify the design concept, an experimental antenna is designed, fabricated, and measured in free-space and muscle mimicking phantom. Moreover, investigations are carried out for wearable and implanted antennas in planar and conformal arrangements. In free-space, the antenna is operating within the industrial, scientific, and medical ISM 5.8 GHz band. Balun integration in the antenna design efficiently chokes the currents excited on the outer surface of the feeding cable and provides a good impedance match between antenna and feed line, as demonstrated by simulation and measurement results. On the other hand, in phantom, the antenna has a wide bandwidth characteristic that covers the most used frequency bands for in-body devices. Balun integration, in this case, showed a negligible effect on antenna’s matching properties for two studied implantation depths; 2.5 cm and 5 cm. The proposed study offers a promising guideline in the design and realization of wearable and implanted antennas.

Orthogonal Chirp Coded Excitation in a Capacitive Micro-machined Ultrasonic Transducer Array for Ultrasound Imaging: A Feasibility Study

It has been reported that the frequency bandwidth of capacitive micro-machined ultrasonic transducers (CMUTs) is relatively broader than that of other ceramic-based conventional ultrasonic transducers. In this paper, a feasibility study for orthogonal chirp coded excitation to efficiently make use of the wide bandwidth characteristic of CMUT array is presented. The experimental result shows that the two orthogonal chirps mixed and simultaneously fired in CMUT array can be perfectly separated in decoding process of the received echo signal without sacrificing the frequency bandwidth each chirp. The experimental study also shows that frequency band-divided orthogonal chirps are successfully compressed to two short pulses having the −6 dB axial beam-width of 0.26- and 0.31-micro second for high frequency and low frequency chirp, respectively. B-mode image simulations are performed using Field II to estimate the improvement of image quality assuming that the orthogonal chirps designed for the experiments are used for simultaneous transmission multiple-zone focusing (STMF) technique. The simulation results show that the STMF technique used in CMUT array can improve the lateral resolution up to 77.1% and the contrast resolution up to 74.7%, respectively. It is shown that the penetration depth also increases by more than 3 cm.

Design and Analysis of The IFA Bandwidth Enhancement for 639 MHz UHF Channel

Bandwidth characteristic enhancement of the antenna is engaging and challenging problems for antenna engineers. The design of the 639 MHz frequency of the low-profile inverted F antenna (IFA) on a finite conducting plane proposed and its characteristics are analyzed numerically. The IFA is typically a narrowband antenna, due to the bandwidth enhancement the antenna parameters are considered. When the size of the conducting plane is 115 mm by 230 mm, the return loss bandwidth (-10 dB) becomes 2.4 % and the gain becomes 6.58 dB. The results found that when the height of the antenna reduced the return loss bandwidth becomes narrower. However, the return loss bandwidth can be improved by extending the length of the short stub. The gains of IFA are more than 6.5 dB in all the calculation conditions. This means that the gain characteristics are not significantly affected by variations in short stub length, the antenna heights and the size of conducting plane. The results show that by extending the height of the antenna and enlarge the size of the conducting plane improved the bandwidth enhancement of the IFA. The proposed inverted F antenna is promising for the UHF channel receiver.