Wireless and inexpensive sensors present a great attractiveness and are of growing interest in such fields as civil engineering. In this study, the feasibility of a wireless sensing system, which consists of a patch antenna sensor and an external wireless interrogator, has been investigated. The patch antenna is designed to operate at two fundamental radiation modes (TM010 & TM001) in the L Radar-frequency band according to the IEEE standard. The ground penetrating radar (GPR) interrogator consists of a printed Ultra-wide band Vivaldi antenna which is connected to a network analyzer. In order to evaluate its ability to monitor civil engineering structures, the performed patch antenna is placed behind various controlled slabs and its resonance frequency is varied artificially. The outside GPR interrogator permits to follow the frequency shift by measuring the reflected signal of the patch antenna. A series of preliminary experimental tests were carried out in order to demonstrate the principle.