Circularly Polarized Annular Ring Antenna With Wide Axial-Ratio Bandwidth for Biomedical Applications

Abstract

This paper proposes a novel circularly polarized antenna operating at 2.4-2.48-GHz industrial, scientific, and medical (ISM) band for biomedical applications. This proposed structure is developed from a simple pin-loaded patch antenna, whose circular polarization (CP) is mainly attributed to the loading of shorting pins and L-shaped open-end slot. Based on this, pin-loaded annular ring (PLAR) with dual-mode operation is adapted to introduce another resonance. In addition, two closely coupled rectangular patches are added to bring these two resonant frequencies close to each other in muscle. Furthermore, by introducing arcshaped slots, CP property and improved impedance matching are achieved with size miniaturization. This proposed structure shows a simulated impedance bandwidth of 8% and a wide axial-ratio (AR) bandwidth of 19.1%. Finally, measurement is performed for the proposed antenna, and the results coincide well with the simulation ones, indicating that it is a good candidate for biomedical applications. INDEX TERMS Biomedical application, circular polarization, implantable antenna, pin-loaded annular ring.

A Compact Hollow Dual Circularly Polarized Antenna With Folded Coupled Feed Structure for Distance Detection Application

“…This comparison shows that just the proposed antenna has not only a dual CP radiation but a compact hollow structure, and a wide 3-dB beamwidth. The antenna [18] has a compact volume than the proposed antenna, but it does not have dual CP radiation. Therefore, the proposed compact hollow dual CP antenna is more suited to install at compact bodies for distance application than the other antennas.…”

“…However, it was fed by a probe, meaning that it is not suitable to be manufactured on a thick substrate. In [18], a loaded CP ring antenna for biomedical applications was designed, in which several slots and patches were added to the ring antenna for CP radiation. In [19], a polarization reconfigurable differential-fed CP ring antenna was simulated and measured.…”

Realization of Circular Polarization and Gain Enhancement for Implantable Antenna

“…feed has drawn extensive attention [1]- [11]. As analyzed in [1], the high loss of human tissue leads to low quality factor of antenna, which means wide CP bandwidth can be achieved inside human tissue.…”

“…Consequently, the commonly known drawback of narrow bandwidth for patch antenna operating in air can be overcome for implantable applications. And those traditional methods for CP are now adopted in implantable applications, such as truncating the corners [1]- [4], adding protruding slits [5]- [7], introducing complementary splitring resonator [8], or loading shorting pins [9]- [11]. In most of these works, two degenerated modes, mostly TM 01 and TM 10 mode, were excited to achieve CP performance, while others of these works, the two modes giving rise to the CP property were not discussed.…”

A Compact Size Implantable Antenna for Bio-medical Applications

“…Xu et al proposed an annular ring antenna for implantable applications in [16]. The volume of the antenna is π× 5 2 ×1.25 mm 3 .…”