An Electrically Small Flexible Microstrip Antenna with Stable Performance

In this letter, a uniplanar, flexible, electrically small antenna is proposed. Evolving from the monopole antenna, the antenna achieves electrically small size by folding the metal line. The size of the antenna is only 26 mm × 26 mm × 0.127 mm
$(0.07 \lambda\times 0.07\lambda\times 0.0004\lambda,\ ka=0.35)$
and the bandwidth of the antenna is 12.3%. The flexibility of the antenna is experimentally analyzed under different bending conditions, and the maximum change are only 1.8% and 0.24 dB for the resonant frequency and gain respectively. The measured results confirm that its performance characteristics are substantially maintained, which is well suitable for wireless biomedical devices.