Dual-Band 3-D MIMO Antenna for Deep Tissue Devices

In this paper, a multiple-input multiple-output (MIMO) capsule endoscopic antenna is proposed for the 915 and 2450 MHz Industrial, Scientific, and Medical (ISM) bands. The single element of the MIMO antenna system has a small size of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5×4.75× 0.1\ mm³</tex> . It has simulated 10-dB bandwidths of 90 and 730 MHz at the low-frequency (915 MHz) and high-frequency (2.45 GHz) bands, respectively. Then, four elements are arranged in a cubical form to develop a quad-element MIMO antenna. The proposed three-dimensional (3-D) MIMO antenna has an overall size of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5× 5× 4.75\ mm³</tex> . It has simulated realized gains of -28.85 and -20.68 dBi at 915 and 2450 MHz, respectively. The proposed antenna is designed and integrated into a capsule device. The other parts of the capsule device include batteries, a camera, light-emitting diodes (LEDs), a printed circuit board (PCB), and surface-mounted devices (SMDs). The endoscope is placed in the human model's stomach. The fabricated 3-D MIMO antenna is validated inside minced pork meat.