Microstrip patch antenna for simultaneous temperature sensing and superstrate characterization

Abstract

This paper investigates a microstrip patch antenna for measuring the thickness and dielectric constant of the medium above the antenna (i.e. the superstrate) as well as the temperature. The intended application is simultaneous sensing of ash accumulation and temperature inside a boiler, with the aim of enhancing safety, improving efficiency, and reducing downtime associated with maintenance. A patch antenna, consisting of a dielectric substrate, a radiation patch, and a ground plane, functions as an electromagnetic resonator with specific fundamental frequencies. A dielectric medium placed above the patch antenna changes its effective dielectric constant and thus its resonant frequencies. Meanwhile, temperature also influences the antenna frequencies because of the thermal expansion of the conductors (i.e. the radiation patch and ground plane), and the dielectric constant of dielectric materials due to their temperature dependency. Since a rectangular patch antenna has two fundamental frequencies, it enables determining these two parameters simultaneously. Once the temperature and superstrate thickness are determined, the dielectric constant of the superstrate and its temperature dependency can also be extracted. To demonstrate this capability, a dual-frequency patch antenna was designed, fabricated, and characterized with a superstrate of various thicknesses and at different temperatures. By fitting the antenna resonant frequencies as functions of the superstrate thickness and temperature, these two parameters were inversely determined from the measured antenna frequencies. Using ash from charcoal briquettes as a superstrate, the measurement uncertainties were determined to be ±0.58 °C and ±58.05 μm for the temperature and the superstrate thickness respectively. The dielectric constant of the ash was found to be 2.64 at room temperature and its thermal coefficient of dielectric constant (TCDk) was found to be 918 ppm °C−1.

Paper‐Based Printed Antenna: Investigation of Process‐Induced and Climatic‐Induced Performance Variability

“…For this reason, ε r in GHz frequency range was calculated using a ring resonator, by fitting the measured and simulated resonance frequency of the resonator (as shown in Figure S1a,b, Supporting Information, as reported before in other studies). [38,39] The calculated value of ε r was 1.6, as also reported in the literature. [40] This was confirmed by both the simulated and the measured results of the fabricated copper tape antenna (as shown in the Experimental Section and Figure 3b).…”

Review of advances in microwave and millimetre-wave NDT&E: principles and applications

“…Microstrip patch antennas have also been used as sensors by either being embedded or attached to materials or structures [187,211]. As with the previously discussed types of sensors, this type of sensor has also been used for many different applications, including temperature [212,213], strain [214–217], dielectric properties [212,218,219] and crack sensing [220]. Being planar, patch antennas can also be made to be flexible and/or conformal to the structures they will monitor [214].…”

Simultaneous crack and temperature sensing with passive patch antenna

“…34 Besides, the temperature itself is also a parameter that should be monitored in structural health monitoring. Tchafa and Huang 38 proposed a patch antenna sensor which can simultaneously measure the environmental temperature and the dielectric constant of the medium above the sensor. This multiple physical variable monitoring sensor enabled dielectric constant and temperature sensing by a single antenna sensor, eliminating the need for additional temperature sensors.…”