This paper presents an angle sensor based on a sector ring patch antenna (SRPA) for loose bolt detection. The sensor is comprised of two parts, a ring substrate sandwiched between a ground plane and a sector ring radiation patch, and a sector ring substrate covered by a radiation patch. The two radiation patches are partially overlapped and the overlapped areas are in contact allowing the electric current to flow within the combined radiation patch. The resonant cavity theory is adopted to explain the relationship between the frequency shift and the overlapped angle. The Ansoft high Frequency Structure Simulator (HFSS) software is used to simulate SRPA, and the dimensional parameters of the antenna are optimized to make the antenna perform better. For verification, two sets of SRPAs are fabricated and tested.

This paper presents a capacitive displacement sensor based on a capacitively fed inverted-F antenna (CFIFA) for displacement detection. The sensor is composed of a grounded L-shape patch and a rectangular upper patch, forming a capacitor between them. The asymmetric dipole model is adopted to explain the frequency shift and current distribution of the proposed antenna sensor at its first-order resonance. The numerical simulation of the CFIFA using the Ansoft high-frequency structure simulator (HFSS) software is carried out to optimize the dimensional parameters, allowing the antenna to perform better. Two sets of CFIFAs are fabricated and tested for verification. Results show that the CFIFA has a good linear relationship between its first resonant frequency and the relative displacement, and is capable of a long range of displacement measuring.