Ultra-Miniature Circularly Polarized CPW-Fed Implantable Antenna Design and its Validation for Biotelemetry Applications

Abstract

the paper presents a coplanar waveguide (cpW)-fed ultra-miniaturized patch antenna operating in Industrial, Scientific and Medical (ISM) band (2.4-2.5 GHz) for biotelemetry applications. The proposed antenna structure is circular in shape and its ground plane is loaded with a pair of slots for obtaining circular polarization. In the proposed design, asymmetric square slots generate phase condition for right-hand circularly polarized (RHCP) radiation. And, by merely changing the position of the slots, either RHCP or left-hand circularly polarized (LHCP) radiation can be excited. In the proposed design, a meandered central strip is used for miniaturization. The simulations of the proposed antenna are carried out using Ansys HFSS software with a single-layer and multilayer human tissue models. The antenna shows good performance for different tissue properties owing to its wide axial ratio bandwidth and impedance bandwidth. The antenna is fabricated and measurements are carried out in skin mimicking phantom and pork. Simulated and measured performances of the antenna are in close agreement. The power link budget is also calculated using an exterior circularly polarized (CP) receiving antenna.Recent advances in technology lead to the design of small and low-power consuming biomedical devices that can be implanted inside a patient's body through surgical operation or ingestion. These embedded devices can sense data from inside the human body in real-time, offering a unique opportunity for early diagnosis and treatment of diseases. The embedded devices communicate with the external world in terms of telemetry. Telemetry includes data transmission from the implanted device to an external one and vice-versa.The standard requirement of all implantable medical devices (IMD) is the wireless operation of equipment and bidirectional data communication. The implantable antenna is one of the critical components for IMD for exchanging body anatomy data with installed base stations 1,2 . In the last few years, several prototypes of implantable patch antennas are proposed; but their radiation efficiency lacks in one or the other parameters such as gain, impedance bandwidth, axial ratio bandwidth; in few cases, antenna footprints are also large for implantation 3-11 . In 12-16 , dimensions of the antenna are significantly reduced making them best prototypes for implantation, but are prone to multipath fading because of their omnidirectional linearly polarized radiations. Though these antenna designs are highly compact, their gain, and impedance bandwidths are very less. Various types of antennas with a defected ground, fractal shape, spiral, slotted, PIFA have been proposed in the literature for wide impedance and axial ratio bandwidth [17][18][19][20] . However, most of the proposed antennas are linearly polarized with large and complex geometry. Few antennas reported consist of ground plane as the primary radiator, but most of them are linearly polarized and proposed for wireless applications. Since the profile of such antennas is...

Design of CPW fed multiband antenna for wearable wireless body area network applications

“…Our design comprises of CPW fed inductive and capacitative coupling among the resonators as depicted in Reference 31 thus accounting for low SAR values. Also, our design is capable of resonating at five different frequencies extenuating higher SAR values as compared to numerous single band and multi band CPW fed wearable antennas 31,[48][49][50][51] The wearable antennas should confirm high immunity to the human body loading. The fabricated prototype of the proposed multiband antenna is attached to different parts of the human body.…”

“…Our design comprises of CPW fed inductive and capacitative coupling among the resonators as depicted in Reference 31 thus accounting for low SAR values. Also, our design is capable of resonating at five different frequencies extenuating higher SAR values as compared to numerous single band and multi band CPW fed wearable antennas 31,48‐51 …”

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“…And in [ 111 ], a button-shaped RFID tag antenna was proposed combining 3-D and inkjet printing technology. This antenna showed a maximum reading range of 2.1 m. A flexible 3-D printed RFID tag antenna [ 139 ] was shown that achieved a maximum 10.6 m read range, and even in several stretching conditions, it covers more than 7.4 m.…”

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“…Circularly polarized (CP) antennas have been widely used in many modern wireless communication systems due to their immunity to multipath propagation [ 12 , 13 , 14 , 15 ]. Moreover, the transmission or reception of signals does not depend on the antenna orientation [ 16 ].…”