A Detuning-Resilient Wideband Microstrip Antenna for Wearable Biomedical Telemetry Through Progressive Interdigital Slot Integration and Patch Defect Engineering

This paper presents the systematic design, equivalent circuit analysis, and experimental validation of a compact wideband circular microstrip patch antenna for use in biomedical telemetry. The antenna, loaded with interdigital capacitive slots and a defected patch structure (DPS), was fabricated on a Rogers RO3006 substrate (relative permittivity 6.5, loss tangent 0.002, thickness 0.8 mm) with overall dimensions of 25 × 36.96 mm2. A stepwise design evolution through five variants (ANT1–ANT5) illustrates the progressive bandwidth enhancement mechanisms. The final design (ANT5) achieved a simulated −10 dB impedance bandwidth of 1.50 GHz (2.51–4.01 GHz), corresponding to a fractional bandwidth of 46%. The fabricated prototype exhibited a measured −10 dB bandwidth of 1.42 GHz (2.54–3.96 GHz), representing a fractional bandwidth of 43.7%. An equivalent lumped-element circuit model was derived and validated against the full-wave simulation results. The antenna exhibited a simulated peak free-space gain of 3.2 dBi at 3.8 GHz, with free-space radiation efficiency exceeding 90%. Under multi-layer tissue phantom loading, the antenna maintained a robust 910 MHz operational bandwidth with a safe maximum specific absorption rate (SAR) of 0.724 W/kg and an on-body efficiency of 8.4%. The compact size and wide fractional bandwidth provide enhanced resilience against environmental detuning, making this design particularly suitable for robust wearable biomedical telemetry.