Miniaturized Dual-Port Frequency-Isolated Implantable Antenna for Self-Duplexing Capsule Endoscopy

This letter presents a miniaturized dual-port self-duplexing implantable antenna for wireless capsule endoscopy (WCE) applications. The proposed antenna provides two independently excited frequency isolated channels centered at 0.868 (Port 2) and 1.41 GHz (Port 1), intended to support self-duplexing WCE telemetry without an external antenna duplexing network. The antenna occupies a compact volume of only π ×(2.5)² × 0.26 = 5.11 mm³ and employs a planar stub-loaded configuration with a full ground plane. The two ports provide isolation levels of approximately 22 and 35 dB at 0.868 and 1.41 GHz, respectively, while maintaining impedance bandwidths of approximately 120 and 110 MHz. The corresponding peak realized gains are −38 and −34.9 dBi. The specific absorption rate (SAR) performance is investigated in a human-body environment to assess the allowable excitation levels for safe implant operation. A prototype of the proposed antenna is fabricated and experimentally characterized in tissue-representative media, with the measured response showing reasonable agreement with the numerical results. The compact footprint, independent frequency-selective ports, high interport isolation, and experimentally verified operation make the proposed antenna a suitable candidate for bidirectional telemetry in WCE systems.