| Fire is one of the most destructive natural disasters.Effective pre disaster warning,fire detection in disaster and post disaster treatment are of great significance to reduce the loss of life and property.In the practical application of conventional sensors,infrared and other detection methods,due to the large smoke,complex environment and many interference information,there are still some shortcomings in the timely realization of pre disaster warning,accurate positioning of fire source and collection of smoldering fire source information under shallow cover.Microwave detection is mainly achieved by passively receiving the energy radiated by fire,which has the characteristics of all day,all-weather,strong smoke penetration ability and strong anti-interference information ability,and can be used as an effective supplement to the existing detection methods.However,the microwave radiometer at this stage does not have the characteristics of high imaging efficiency and portability required by emergency rescue imaging equipment.Therefore,starting from the design of portable microwave fire detector,this thesis studies the key technologies of the detector imaging system,such as unit antenna design,high isolation feed receiving antenna array design and focal plane imaging systemIn this thesis,a new antenna with phase g radient wall structure is proposed as the unit antenna of portable fire detector imaging system.The structure is placed on both sides of the unit antenna in the form of a wall,and the electromagnetic wave radiated by the antenna is precisely controlled by using the super surface technology,so as to optimize the electromagnetic field distribution of the antenna and improve the performance of the antenna.Through simulation and experiment,the 3d B beamwidth of E-plane and H-plane is increased by 4 ° and 13 ° respectively,and the gain and sidelobe are not deteriorated.This performance improvement effectively increases the field of view of the imaging system,expands the scanning coverage,and plays a key role in improving the imaging efficiency of portable fire detector.Then,the focusing and defocusing characteristics of the bifocal wide-angle focusing lens antenna and the performance of the unit antenna based on the phase gradient wall structure are comprehensively analyzed.A high isolation feed receiving antenna arrangement is proposed,and an imaging system for fire environment detection is completed.The imaging system consists of a 3 * 3 high-performance feed receiving antenna array and a bifocal wide-angle focusing lens antenna array It is composed of focal lens antenna,and the field of view covered by its nine beams reaches 18 ° * 18 ° which meets the design requirements of portable fire detector for large field of view imaging system.Finally,the imaging experiment of the imaging system is completed.From the analysis of the experimental results,it can be concluded that the spatial resolution and field of view of the imaging system are basically consistent with the theoretical values,which verifies the correctness and rationality of the design of the imaging system. |
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