RF communication between dual band implantable and on body antennas for biotelemetry application

Abstract This paper investigates two antennas for implantable communication, which are a wide-band, low-profile transmitting antenna with a circular polarization (CP) merit immersed in a lossy medium and a corresponding wide-band, low-profile receiving antenna with a linear polarization (LP) merit placed on human tissue. The first antenna is implantable inside a human body for sensing, monitoring, and transmitting various vital signs, while the second antenna acts as a nearby receiving end. These antennas work in the 2.4-2.4835 GHz and 5.725-5.875 GHz industrial, scientific, and medical (ISM) bands. The main features of the designed transmitting antenna are its simplicity, the wide-band characteristics, which preserve the detuning effect caused by environmental heterogeneity, and the CP property at both operational ISM bands. Moreover, for introducing an electrically small antenna footprint with proper performance, the implantable antenna is designed with an entire size of 25.4 (5 $$\times$$ 5 $$\times$$ 1.016) $$\hbox {mm}^3$$ . This antenna is designed and dissected in a homogeneous skin model (HSM) as well as a three-layer phantom. On the other hand, the wide-band receiving antenna is designed on flexible material for patients’ comfort with a compact size of 134.6 ( $$20\times 26.5\times 0.254$$ ) $$\hbox {mm}^3$$ . In addition, the implantable antenna performance is evaluated in a chicken slab as well as a saline solution, while the on-body antenna is placed on the chicken slab to measure its reflection coefficient. The measured impedance BWs of the implantable antenna are 13.04 % and 33.2 % in the chicken slab while 19.5% and 25.2 % in the saline solution at the two ISM bands, respectively. While, the measured impedance BWs of the on-body antenna are 24% and 50.4 % at two operating ISM frequencies. Finally, the measured transmission coefficient between the two antennas is evaluated.