ANALYSIS OF FACTORS AFFECTING THE SENSITIVITY OF PYROELECTRIC HEAT RADIATION RECEIVERS IN MOTION TRANSMITTERS

Abstract

The article analyzes one of the types of transmitters used in Smart City technologies. In particular, sensors based on pyroelectric receivers that register thermal radiation, in particular the radiation of the human body, are considered. It has been established that a number of characteristics are used to assess the efficiency of radiation receivers, the most important of which are sensitivity and sensitivity threshold. Mathematical relations are presented that describe the sensitivity of the receiver as a complex frequency characteristic that connects the reaction of the pyroelectric receiver and the influence on it in the form of a harmonic flow. The characteristics of the sensitivity threshold of the receiver and the formulas for determining this characteristic are presented. It was established that in order to determine the sensitivity threshold of pyroelectric thermal radiation receivers, it is necessary to know the noise level of its sensitive element. To derive the corresponding formulas, an equivalent circuit of a pyroelectric receiver is presented. Sources of noise of pyroelectric elements are established, in particular, thermal (Johnson) noise of the load resistance, thermal (Johnson) noise of the dielectric loss resistance of the sensitive element, noise EMF of the measuring circuit, single noise current of the measuring circuit, temperature noise of the sensitive element. The graphical dependence of the amount of noise from various sources for a typical detector with electrical and thermal time constants is given. Appropriate conclusions were drawn based on the results of the analysis.