A Dual-mode Microstrip Antenna for Sensing Applications

In this paper, we propose a low-cost, immersive, dual-mode electromagnetic sensing antenna with ultra-highly sensitivity for edible oil detection, achieved by two magnetic-LC (MLC) resonators loaded on the radiation microstrip patch. The proposed antenna is developed on a Rogers RT/duroid 5880 substrate, and resonates at 12.61GHz and 16.21GHz simulated with High Frequency Structure Simulator (HFSS). It is found that current path of the antenna is longer at the first resonance point of 12.61GHz, while at the second frequency resonance point of 16.21GHz, the current path is shorter. The electric field of the designed microstrip antenna in both frequencies is concentrated at the edge of the MLC resonators, making the region much sensitive to the changes of nearby dielectric materials. The antenna is fabricated through traditional PCB processing technology, and S-parameter of the designed antenna is tested with vector network analyzer (VNA). The measured results are basically consistent with the simulated results. Moreover, a sensing experiment platform using the VNA (AV3672C, 10MHz–43.5GHz) is constructed with fixed bracket and lifting platform, which can minimize the measurement error. When the proposed dual-mode electromagnetic sensing antenna is immersed in peanut oil, heated at different time and cool down to room temperature, it is found that the resonance frequencies of the antenna will shift greatly due to the changes of the effective dielectric constant, thus the sensing ability of the proposed dual-mode antenna is verified. The relationship between the heated time of peanut oil and resonance frequency is calculated to estimate quality of samples to be tested.