Abstract
Controlled measurements by a low-cost single-pixel microwave radiometer operating at 12.65 GHz were carried out to assess the detection and counting capability for targets warmer than the surroundings. The adopted reference test targets were pre-warmed water and oil; and a hand, both naked and wearing a glove. The results showed the reliability of microwave radiometry for counting operations under controlled conditions, and its effectiveness at detecting even warm targets masked by unheated dielectric layers. An electromagnetic model describing the scenario sensed by the radiometer antenna is proposed, and comparison with the experimental observations shows a good agreement. The measurements prove that reliable counting is enabled by an antenna temperature increment, for each target sample added, of around 1 K. Starting from this value, an analysis of the antenna filling factor was performed to provide an instrument useful for evaluating real applicability in many practical situations. This study also allows the direct people counting problem to be addressed, providing preliminary operational indications, reference numbers and experimental validation.
Highlights
The continuous expansion of the Internet of Things (IoT), allowing objects to be sensed and remotely integrated across wireless network infrastructures, covers a growing number of applications.The IoT encompasses several technologies able to gather information from the environment by employing both contact and remote sensors with low cost and low energy consumption features.With regard to remote sensors applied to the IoT scenario, an interesting application is the counting of warm targets and, in particular, of people.The use of microwave (MW) radiometers for IoT applications aimed at detecting and counting targets warmer than their surroundings, especially when optically masked, is certainly a stimulating challenge
The counting issue is mainly focused on person counting, since many situations, such as security, safety and customer monitoring, can require people to be counted: specific non-restrictive examples being the estimation of queue length in shopping centres, the monitoring of entry points, train stations, bus terminals, and the evaluation of people flux in shops, stores, etc
Automated systems based on contact sensors have been developed for this over the years, such as pedestrian barriers and gateways
Summary
The continuous expansion of the Internet of Things (IoT), allowing objects to be sensed and remotely integrated across wireless network infrastructures, covers a growing number of applications.The IoT encompasses several technologies able to gather information from the environment by employing both contact and remote sensors with low cost and low energy consumption features.With regard to remote sensors applied to the IoT scenario, an interesting application is the counting of warm targets and, in particular, of people.The use of microwave (MW) radiometers for IoT applications aimed at detecting and counting targets warmer than their surroundings, especially when optically masked, is certainly a stimulating challenge. The IoT encompasses several technologies able to gather information from the environment by employing both contact and remote sensors with low cost and low energy consumption features. With regard to remote sensors applied to the IoT scenario, an interesting application is the counting of warm targets and, in particular, of people. The use of microwave (MW) radiometers for IoT applications aimed at detecting and counting targets warmer than their surroundings, especially when optically masked, is certainly a stimulating challenge. The idea of providing a method for the contactless grading and counting of agricultural products by using a MW radiometer at Ku band was proposed [1], but experimental results in the open literature are still missing. Several technologies that have the potential to count people, as described in [2], encompass video cameras, passive infrared (IR) cameras, infrared beam counters, piezoelectric pad, laser scanner. The counting performance of different technologies, Sensors 2017, 17, 1388; doi:10.3390/s17061388 www.mdpi.com/journal/sensors
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