Identification of Q value of smart gear antenna by return loss analysis of receiving antenna

(Non-contact health monitoring system for gears manufactured by printing conductive ink)

Abstract

A “smart gear sensor system” consisting of an antenna connected to a network analyzer and another antenna having the same shape connected to a crack detection sensor was proposed in our previous paper. The results of this previous paper have shown that the return losses of the monitoring antenna changed depending on the sensor conditions, healthy or unhealthy. However, no parameters of the smart sensor on the gear side have been identified yet even though the use of this identification for the gear failure process wirelessly is inevitable. Hence, in this study, a method for wirelessly identifying the quality (Q) factor by executing a frequency analysis using the return loss of the observation antenna is proposed. In the first place, a model denoted the magnetic coupling phenomenon between the two antennas is introduced. Next, the derivation for the expression of the return loss of the observation antenna was conducted. Since the appearance of the unknown Q parameter in this expression is realized, necessary transforms have been executed to establish a simultaneous equation of Q factor. Then, by solving this equation, solutions of Q values are obtained. Furthermore, gradient descent method has been applied to optimize the identification process of Q value. This value of Q parameter later is validated by simulation and the consequences have demonstrated that this method could efficiently identify the Q parameter of the antenna on the gear side.