Microwave Radiometers for Fire Detection in Trains: Theory and Feasibility Study

Abstract

This paper introduces the theory of fire detection in moving vehicles by microwave radiometers. The system analysis is discussed and a feasibility study is illustrated on the basis of two implementation hypotheses. The basic idea is to have a fixed radiometer and to look inside the glass windows of the wagon when it passes in front of the instrument antenna. The proposed sensor uses a three-pixel multi-beam configuration that allows an image to be formed by the movement of the train itself. Each pixel is constituted by a direct amplification microwave receiver operating at 31.4 GHz. At this frequency, the antenna can be a 34 cm offset parabolic dish, whereas a 1 K brightness temperature resolution is achievable with an overall system noise figure of 6 dB, an observation bandwidth of 2 GHz and an integration time of 1 ms. The effect of the detector noise is also investigated and several implementation hypotheses are discussed. The presented study is important since it could be applied to the automatic fire alarm in trains and moving vehicles with dielectric wall/windows.

A Novel Sensor Based on a Single-Pixel Microwave Radiometer for Warm Object Counting: Concept Validation and IoT Perspectives

“…This aspect can be quantitatively explained by the so-called filling factor. The filling factor q , indeed, is defined as the power received from an extended source (i.e., the target) relative to that which would be received from a source having the same brightness but extending over the entire antenna power pattern [ 13 , 17 , 24 ].…”

“…Moreover, MW systems may be effective, for instance, in situations where insufficient lighting, smoke and fog prevent the direct visualization of the scenario that are typical conditions, for example, in rescue scenarios or in outdoor night-time situation. From this perspective, a microwave radiometer with high sensitivity [ 17 ] can potentially detect the presence of people by exploiting the higher physical temperature of human beings with respect to their surroundings without being jammed by clothes [ 18 ].…”

Experimental Implementation of a Passive Millimeter-Wave Fast Sequential Lobing Radiometric Seeker Sensor

“…The output signal is integrated and the corresponding signal processed in order to extract the information. As for first approximation it's possible to consider, for each beam, Gaussian power patterns as [7] f (ϑ, φ) = G o e −bϑ 2 (1) that depend only on the angle between the ordinary − → k versor and the generic positional versor − → p . For such patterns, the constant b is [7]:…”

“…Passive millimetre-wave sensors are widely used nowadays for different purposes. Principal civil applications of such sensors concern surveillance [1] [2] and navigation aid in adverse weather conditions [3] and concealed weapons and explosives detection in airports [4] [5]. Military applications span from surveillance through radiometric imaging to precision targeting [6].…”

Experimental Implementation of a Passive Millimeter-Wave Fast Sequential Lobing Radiometric Seeker Sensor

“…Principal civil applications of such sensors concern surveillance [1,2] and navigation aid in adverse weather conditions [3], as well as concealed weapon and explosive detection in airports [4,5]. Military applications span from surveillance through radiometric imaging to precision targeting [6].…”