Method for measuring grain moisture content based on microwave frequency sweep technology

Abstract

The invention discloses a method for measuring the grain moisture content based on a microwave frequency sweep technology. The measuring method adopts a grain moisture content measuring device based on a frequency sweep microwave penetration method. The method mainly comprises the steps of setting an initial microwave frequency sweep signal MSS according to the characteristics of different kinds of grains, removing poor frequency points corresponding to a great reflection coefficient [Gamma] and standing-wave ratio [Rho] in the MSS by taking the automatic alignment of microwave antennas as a basis to obtain an optimized frequency sweep signal MSS'; determining and adjusting to the optimum measurement distance and inter-antenna distance according to three conditions such as an antenna far field condition, the representativeness of the moisture content measurement result and microwave space transmission loss reduction; mutually interacting the radiation optimized frequency sweep signal MSS' and the grain to be measured, inputting the microwave attenuation A and the microwave phase shift [Phi] into a grain moisture content prediction model to calculate the grain moisture content measurement result. The method not only uses the microwave frequency sweep technology, but also optimizes the used frequency sweep signal, is comprehensive in consideration when the microwave attenuation is calculated, and improves the accuracy of the grain moisture content measurement.

Description

technical field [0001] The invention relates to agricultural product quality detection, in particular to a method for measuring grain moisture content based on microwave frequency sweep technology, which is mainly suitable for fast and non-destructive measurement of grain moisture content. technical background [0002] Moisture content is an important characteristic of grain, which has a great influence on its physical and chemical properties. The moisture content of grain affects its harvesting, storage, transportation, processing and other aspects, and it is also a key indicator for judging the quality of certain grains. Microwave detection method, as an emerging material moisture content measurement method, can realize fast and non-destructive measurement of grain moisture content. It can detect the moisture inside the material, and the moisture content measurement results are representative. Therefore, the microwave penetration method is more and more applied to the moi...

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Problems solved by technology

[0004] The purpose of the present invention is to solve the problems in the current grain moisture content measuring device based on the microwave penetration method, such as the interference of multiple reflections on microwave attenuation and phase shift measurement; the influence of reflected microwave signals is not considered when calculating microwave attenuation; The alignment between the antennas is usually completed with simple measurement tools combined with human eye observation. The alignment accuracy between the microwave transceiver antennas is poor, the coincidence degree of the main lobes of the two antenna beams is not high, and the microwave signal transmission is incomplete; The measurement distance of the grain to be measured and the distance between the microwave transceiver antennas are relatively arbitrary, and it is difficult to ensure that the microwave antenna is in a sensitive position when measuring the moisture content of different grains. On the basis of reasonable setting of the distance between antennas and antennas, set the sweep signal according to the type of grain to be measured, optimize the sweep signal according to the characteristics of the antenna, and consider the influence of reflected microwave signal when measuring microwave attenuation. Grain moisture content measurement method

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