Compact ingestible planar inverted-F antenna (PIFA) for biotelemetry systems

Abstract

Bleeding from the gastrointestinal (GI) tract is a common medical problem. The GI tract starts at the mouth, going to the oesophagus, stomach, small intestine, colon and end at the rectum and anus. The traditional wired endoscopy made it possible to diagnose the oesophagus, stomach, colon, rectum and anus, but limited by physical reasons, leaving the remaining 20 feet of the small intestines regardless using upper or lower endoscopy procedures. An ingestible wireless biomedical device or wireless capsule endoscope fitted with a mini video camera and small enough to swallow can painlessly examine the parts that wired endoscopy cannot reach for diagnosing unexplained bleeding or other abnormalities. The challenging demand of ingestible wireless biomedical device performance reflects on the difficulties of designing the antenna for those device since the antenna plays a key role for having an abundance of quality communication links and miniaturization of the whole device, compared to the other essential components. In this thesis, a compact planar inverted-F antenna (PIFA) is proposed to be integrated with an ingestible tablet antenna system for biotelemetry application in the 2.4-2.48 GHz industrial, scientific, and medical (ISM) band. By taking the tissue properties and its losses, the design of the proposed antenna was performed inside a phantom box filled with body tissue simulating liquid (BTSL) (εr = 52.7). Besides reducing simulation time, this is mainly due to the practical ease to validate and measure its similar performance within the environment of a human small intestine (εr = 54.4). The proposed antenna is compact and is sized at 859 mm3 (15 mm x 12 mm x 4.7748 mm). It is built using twostacked structures; Taconic TLY-5 (εr = 2.2, tan δ = 0.0009) substrate and Eccostock HiK500F ceramic material (εr = 30, tan δ = 0.002). The resonance characteristic, radiation performance, specific absorption rate (SAR) distribution and communication link of the proposed antenna inside the BTSL is evaluated and compared with its performance inside a four-layer canonical tissue model (skin, fat, muscle and small intestine). Most importantly, the proposed antenna achieved the highest bandwidth per unit volume (BW/Vd) compared to other work in literature for in-body applications.