Miniaturised implantable circular polarized antenna with a high ARBW

Abstract

For biological applications, this communication uses an implanted antenna loaded with metamaterial and a sorting pin. The suggested antenna operates at 2.44 GHz in the ISM band. The first antenna's resonant frequency is lowered from 2.53 GHz to 2.46 GHz by applying a sorting pin. This causes the antenna to become circularly polarized and have an ARBW of 580 MHz (2.15 GHz - 2.73 GHz). Strong CP behavior with an ARBW of 830 MHz from 2.01 GHz to 2.84 GHz in the ISM band is produced by incorporation of an H-shaped metamaterial on the antenna's superstrate. Additionally, the reasonable value of the specific absorption rate improved from 960.5 to 952.1. Highlights of the suggested antenna include its miniature size (10.67 mm3), strong CP properties, the significant value of SAR 952.1 W/KG, and unslotted ground plane to detract from designing labyrinthine backscattering radiation. After building the recommended antenna, experiments are conducted using a skin-mimicking gel solution that approximates the electrical characteristics of human skin tissues at 2.44 GHz. In the ISM band, actual and simulated impedance bandwidths of 90 MHz and 110 MHz are acquired, respectively. Together with parametric analysis, simulation and measurement results are consistent.

Fig 1. Configuring the suggested antenna for simulation in a single-layer skin phantom.

Fig 2. (A) Design of patch surface of proposed antenna from top view (B) ground plane of proposed antenna from bottom view (C) Design of Metamaterial on superstrate (D) Side view of proposed antenna.

Fig 3. (A) Design of A/N 1 radiating surface.

(B) Design of A/N 2 radiating surface. (C) Design of metamaterial of A/N 3 on the superstrate surface.

Fig 4. (A) Reflection coefficient comparison of several antenna designs.

(B) Comparison of axial ratio bandwidth of different antenna designs. (C) Position of sorting pin on patch surface. (D) The axial ratio of different positions of sorting pin on patch surface (A/N 2). (E) Characteristics curve of metamaterial design with effective permittivity and permeability.

Fig 5. (A) The suggested antenna’s (A/N 3) reflection coefficient at various penetration depths.

(B) The reflection coefficient of the proposed antenna in several human tissue models. (C) Various dielectric substrate materials and the reflection coefficient of the proposed antenna.

Fig 6. (A) Reflection Coefficient of different superstrate materials.

(B) SAR of Alumina superstrate material. (C) SAR of FR-4 epoxy superstrate material. (D) SAR of polyethylene superstrate material. (E) SAR values of different superstrate material of proposed antenna. (F) Reflection coefficient of different shaped superstrate of proposed antenna.

Fig 7. The SAR, Axial ratio bandwidth, and Reflection coefficient (S₁₁) of proposed antenna with biocompatible layer of Roger rt duroid.

Fig 8. (A) Radiating patch surface of the fabricated implantable antenna.

(B) H-Shaped metamaterial design on the superstrate surface.

Fig 9. (A) Measurement setup of the proposed implantable antenna with saline solution.

(B) Comparison of the reflection coefficient of simulated and fabricated proposed implantable antenna.

Fig 10. (A) SAR of A/N 1 according to IEEE standard for 1 gram of tissue.

(B) SAR of A/N 2 according to IEEE standard for 1 gram of tissue. (C) SAR, using an IEEE standard, of the suggested antenna (A/N 3) for one gram of tissue.

Fig 11. (A) Surface current distribution of radiating path (patch) proposed implantable antenna with 0⁰ phase angle at 2.44 GHz.

(B) at 90⁰ (C) at 180⁰ (D) at 270⁰.

Fig 12. (A) Normalized simulated gain of suggested antenna at 2.44 GHz.

(B) Normalized measured gain of the proposed antenna at 2.44 GHz. (C) LHCP and RHCP gain of suggested antenna at 2.44 GHz.

Fig 13. (A) Path loss of Transmitting antenna at a different distance.

(B) Link margin of the proposed implantable antenna at 2.44 GHz frequency for different bit rates at different distances.