Abstract-Presently, wireless capsule endoscopy (WCE) is the sole technology for inspecting the human gastrointestinal (GI) tract for diseases painlessly and in a non-invasive way. For the further development of WCE, the main concern is the development of a highspeed telemetry system that is capable of transmitting high-resolution images at a higher frame rate, which is also a concern in the use of conventional endoscopy. A vital task for such a high-speed telemetry system is to be able to determine the path loss and how it varies in a radio channel in order to calculate the proper link budget. The hostile nature of the human body's channel and the complex anatomical structure of the GI tract cause remarkable variations in path loss at different frequencies of the system as well as at capsule locations that have high impacts on the calculation of the link budget. This paper presents the path loss and its variation in terms of system frequency and location of the capsule. Along with the guideline about the optimum system frequency for WCE, we present the difference between the maximum and minimum path loss at different anatomical regions, which is the most important information in the link-margin setup for highly efficient telemetry systems in next-generation capsules. In order to investigate the path loss in the body's channel, a heterogeneous human body model was used, which is more comparable to the human body than a homogenous model. The finite integration technique (FIT) in Computer Simulation Technology's (CST's) Microwave Studio was used in the simulation. The path loss was analyzed in the frequency range of 100 MHz to 2450 MHz. The path loss was found to be saliently lower at frequencies below 900 MHz. The smallest loss was found around the frequency of 450 MHz, where the variation of path loss throughout the GI tract was 29 dB, with a minimum of −9 dB and a maximum of −38 dB. However, at 900 MHz, this variation was observed to be 38 dB, with a minimum of −10 dB and a maximum of −48 dB. For most positions of the capsule, the path loss increased rapidly after 900 MHz, reaching its peak at frequencies in the range of 1800 MHz to 2100 MHz. During examination of the lower esophageal region, the maximum peak observed was −84 dB at a frequency of 1760 MHz. The path loss was comparatively higher during examination of anatomically-complex regions, such as the upper intestine and the lower esophagus as compared to the less complex stomach and upper esophagus areas.

Abstract-Rubber tire dust-rice husk is an innovation in improving the design of pyramidal microwave absorbers to be used in radio frequency (RF) anechoic chambers. An RF anechoic chamber is a shielded room covered with absorbers to eliminate unwanted reflection signals. To design the pyramidal microwave absorber, rice husk will be added to rubber tire dust since the study shows that both have high percentages of carbon. This innovative material combination will be investigated to determine the best reflectivity or reflection loss performance of pyramidal microwave absorbers. Carbon is the most important element that must be in the absorber in order to help the absorption of unwanted microwave signals. In the commercial

Abstract-We investigated a dielectric resonator ceramic microstrip patch antenna. The antenna was formed using barium strontium titanate (BST), which had a dielectric constant of 15. A new approach, i.e., the use of a high temperature dielectric probe kit, was used to determine the dielectric constant of BST. A computer simulation technology (CST) microwave studio was used to simulate the BST array antennas, taking into consideration the dielectric constant. We also measured the gain of the antennas loaded with two-, four-, and six-element arrays of the BST antenna and found that the gain of a six-element BST array antenna was enhanced by a gain of about 1.6 dB over the four-element BST array antenna at 2.3 GHz. The impedance bandwidths of these BST array antennas for voltage standing wave ratio (VSWR) < 2 were in the application ranges,

Abstract-Split ring resonator (SRR) structure can potentially be incorporated onto the truncated pyramidal microwave absorber. This study considers three different patterns of edge couple split ring resonator (EC-SRR) designs. Each EC-SRR design is then placed onto the truncated pyramidal microwave absorber. Outer split gap dimension widths of the EC-SRR are varied, and the various S 21 performances are compared. This EC-SRR truncated pyramidal microwave absorber is simulated using CST Microwave Studio simulation software. The study and simulation are performed in low frequency range (0.01 GHz to 1 GHz) as well as in microwave frequencies range (1 GHz to 20 GHz). Simulation results of this EC-SRR show improvement of reflection loss and S 11 performance in the high frequency range of the pyramidal truncated microwave absorber.

Abstract-The need to find ways to effectively utilize the large quantities of agricultural waste that are produced is indicative of the huge potential associated with producing an alternative pyramidal microwave absorber for anechoic chamber-testing applications. We propose the development of a pyramidal microwave absorber that can use sugar cane bagasse (SCB), a byproduct from the production and processing of sugar cane, as the absorbent. In this paper, we report the results of our use of dielectric probe measurement to determine the dielectric constant and loss tangent of SCB. These values were used to model and simulate an SCB pyramidal microwave absorber in Computer Simulation Technology's (CST's) Microwave Studio. This absorber was operated in the microwave frequency range between 0.1 GHz and 20.0 GHz.

Abstract-Biomass used for energy, whether it is extracted from forest residues or agricultural waste, contributes in many areas, such as power production, the construction industry, and also as a major source of different organic and inorganic compounds in the petrochemical industry. In recent years, research has identified a very remarkable use of agricultural waste, especially rice husks, as a microwave absorber in a pyramidal shape. However, absorbers built in this shape are fragile and require a very high degree of care, especially near the access panels, doors, and high traffic areas of the anechoic facility. This paper presents the results of a detailed experimental investigation of a more-robust, new design that is based on the concept of impedance or dielectric grading of rice-husk material. The absorber was fabricated using multiple layers of rice-husk material with increasing dielectric loss along the incident wave propagation axis. This type of fabrication technique provides more robust design of the microwave, rice-husk absorber with less thickness, as compared to the geometricallytapered, pyramid, or wedge absorbers. Free-space transmission and radar cross section (RCS) methods have been used, to study the electromagnetic compatibility (EMC) performance over the frequency range of 4-8 GHz. After the receiving equipment was calibrated by the thru-reflect-line (TRL) calibration technique, the experiments were performed inside the anechoic chamber. The performance of the absorber was evaluated by incorporating the effects of circular-hole perforation, cross-polarized seams, and different metallic back plates. The proposed absorber demonstrated good performance (< −10 dB) for normal and 60 • off the normal incident angles over the frequency range of 4-8 GHz. Reflectivity performance also was found to be comparable to one of the commercially-available absorbers.

No abstract

No abstract