Sensitivity Enhancement in Cardio-Pulmonary Stethoscope Applications Through Artificial Magnetic Conductor-Backed Antenna Design

This paper presents an antenna for the cardio-pulmonary stethoscope (CPS) to improve sensitivity in detecting pulmonary edema. The CPS employs a dual-antenna system for monitoring the transmission coefficient. However, conventional patch antennas used in CPS setups often exhibit limited sensitivity due to frequency detuning. This study addresses this limitation through a two-stage approach. Firstly, the design goals of the CPS antenna are characterized. The results prioritize a broad impedance bandwidth, large half-power beamwidth (HPBW), and high front-to-back ratio (FBR) as key design objectives. Secondly, an antenna backed with an artificial magnetic conductor (AMC) is proposed to meet the specified goals. The fabricated prototype, operating at 2.4 GHz with an AMC size of 81.0 × 81.0 mm ² , exhibits a fractional bandwidth of 27.6%, a FBR of 18.5 dB, and HPBWs of 60° and 70°. Validation is conducted using phantom models simulating different water content levels. The conventional patch antenna yields transmission coefficients between –49.6 dB and –63.5 dB; in contrast, the proposed antenna achieves transmission coefficients ranging from –35.5 dB to –45.7 dB. The sensitivities for normal and severe water contents are improved by 14.1 dB and 17.8 dB, respectively, indicating higher sensitivity and performance enhancement in CPS remote monitoring.