Microstrip Array Antenna Design for a 24 GHz Radar-Based Vital Signs Monitoring System
Murtini Murtini,
Nurhayati Nurhayati,
Usman Rizqi Iman,
Fitri Yuli Zulkifli,
Dewiani Dewiani and
Lilik Anifah
Non-contact vital signs monitoring using radar technology has become increasingly important in modern healthcare, as it enables continuous physiological measurement without direct skin contact, minimizing patient discomfort and the risk of infection. To address these needs, this study presents the design and analysis of a 24 GHz microstrip array antenna developed for a radar-based vital signs monitoring system. Array configurations consisting of one to five circular patch elements were analyzed to optimize reflection coefficient, gain, and radiation characteristics, aiming to achieve high sensitivity, compactness, and safety for biomedical radar applications. Simulation results indicate that the four-element array achieves optimal performance, with a reflection coefficient of -39.27 dB, gain of 5.29 dBi, and bandwidth of 1.35 GHz at 24 GHz. To evaluate electromagnetic safety, Specific Absorption Rate (SAR) analysis using a three-layer human tissue model (skin, fat, and muscle) yielded values of 0.637 W/kg (1 g) and 0.205 W/kg (10 g) at a 50 mm separation distance, both within ICNIRP and FCC limits. Furthermore, bending simulations with curvature radii of 5 mm, 15 mm, and 50 mm confirmed stable impedance matching and minimal frequency variation, demonstrating strong mechanical flexibility. Overall, the proposed antenna exhibits high gain, reliable performance, and safety compliance, making it suitable for integration into portable radar-based medical devices for continuous and contactless monitoring of heart rate and respiration.
