Influence of transverse deformation on resonant frequency of patch antenna

The strain sensor based on microwave patch antenna is presented to monitor structural strain. Theoretically, the resonant frequency of antenna is determined by both the length and the width of the antenna. When the antenna is stretched uniaxially, the resonant frequency of the antenna shifts mainly due to its length change in longitudinal direction. However, the effect of the transverse deformation due to Poisson effect on resonant frequency of the antenna is yet to be confirmed and evaluated. Two sets of experiments are prepared to study the effect. The resonant frequencies of 2.45GHz chipless patch antennas with fixed length and varying width are tested; and the 920MHz chipped patch antennas are attached to the surface of specimens with the stretching direction parallel to length direction of antennas and perpendicular to length direction, respectively. Both types of specimens are stretched under different levels of tension force to determine the sensitivity coefficient between resonant frequency shift and antenna strain. Both results show that the influence of the transverse deformation of antennas on resonant frequency can be neglected, and its resonance frequency has a good linear relationship with the longitudinal strain.