Comprehensive Design and Propagation Study of a Compact Dual Band Antenna for Healthcare Applications
Journal of Sensor and Actuator Networks
In this paper, a dual band planar inverted F antenna (PIFA) has been investigated for cooperative on-and off-body communications. Free space and on-body performance parameters like return loss, bandwidth, radiation pattern and efficiency of this antenna are shown and investigated. The on-and off-body radio propagation channel performance at 2.45 GHz and 1.9 GHz have been investigated, respectively. Experimental investigations are performed both in the anechoic chamber and in an indoor
... an indoor environment. The path loss exponent has been extracted for both on-and off-body radio propagation scenarios. For on-body propagation, the path loss exponent is 2.48 and 2.22 in the anechoic chamber and indoor environment, respectively. The path loss exponent is 1.27 for off-body radio propagation situation. For on-body case, the path loss has been characterized for ten different locations on the body at 2.45 GHz, whereas for off-body case radio channel studies are performed for five different locations at 1.9 GHz. The proposed antenna shows a good on-and off-body radio channel performance. OPEN ACCESS J. Sens. Actuator Netw. 2015, 4 51 Keywords: dual band; planar inverted F antenna; on/off-body communications; on/off-body radio channel; path loss; body area networks; body-centric wireless communications Introduction Wireless sensor and body area networks are attractive solutions that can be used in healthcare applications, which will enable constant monitoring of health data and constant access to the patient. It was estimated that wireless sensor solutions could save $25 billion worldwide in annual healthcare costs by reducing hospitalizations and extending independent living for the elderly . Body-centric wireless communications (BCWCs) is a central point in the development of fourth generation mobile communications. In body-centric wireless communication, the wireless connectivity between body-centric units is provided through the deployment of sensor and compact antennas  . Body-worn antennas can suffer from reduced efficiency and gain due to electromagnetic absorption in tissue, radiation pattern fragmentation, variations in feed point impedance and frequency detuning [3, 4] . In common healthcare monitoring scenarios, it is very important for the antenna to communicate among the devices mounted on the body as well as off-body devices. There are two main channels of interest for wireless body area networks: off-body and on-body. The on-body-communications-describe the link between body mounted devices communicating wirelessly, while off-body communication defines the radio link between body worn devices and base units or mobile devices located in surrounding environment  . Recently, there has been increasing interest in research and development for designing wearable antennas. In previous studies, most researchers have designed the antennas for on-body communications at 2.45 GHz and ultra wideband (UWB) at 3.1~10.6 GHz . Researchers also investigated the on-body radio propagation channel both in narrowband at 2.45 GHz and ultra wideband (3~10 GHz) technologies . However, there is a need of antenna design for cooperative on-body and off-body communications. In this paper, a dual band planar inverted F antenna (PIFA) is designed and the performance parameters of that antenna are investigated in close proximity to the human body. The proposed PIFA operates at two different frequency bands, 2.45 GHz (ISM band) and 1.9 GHz (PCS band). The 2.45 GHz is used for the communication (on-body) among the devices located over the human body surface and 1.9 GHz is used for the communication from body mounted devices to off-body units (off-body). The on-body radio channel behavior at 2.45 GHz and off-body radio channel performance at 1.9 GHz of the proposed PIFA has also been experimentally investigated. The rest of the paper is organized as follows; Section 2 discusses about the PIFA antenna design and its free space and on-body performance parameters, Section 3 talks about on-body radio channel measurements setting and on-body results, section 4 presents off-body radio channels measurement settings and results, and finally Section 5 draws the conclusion of the presented study.