The radio wave propagation model in granary can provide technical support for the design and application of wireless grain situation monitoring and foreign-body detection in granary. The propagation of radio waves in granary with wheat is studied in this paper. Firstly, transmitting and receiving antennas are fixed in grain bulk. Then the parameters of multipath delay and received power at receiver are calculated by using ray-tracing algorithm, and the wave propagation model is established. The results show that only the direct and one-reflection paths of larger amplitude are considered in the wheat grain bulk. Finally, the path losses of simulation at different distances are compared with the theoretical value of the literature, the accuracy of the simulation results is verified and the effect of reflection is reflected.

Radio Frequency (RF) perception of humidity is the current research hotspot of grain condition monitoring for "three temperature and three humidity". In order to analyze the optimal detection parameters on humidity of storage environment, the Wireless Insite test platform is built to analyze the effects of antenna height, carrier frequency and grain and with different moisture content on Channel State Information (CSI) such as received power, path loss and time delay. The mathematical relations between the humidity and path loss, the humidity and time delay are deduced respectively. In simulation experiments, the frequency bands of 2.4GHz, 5GHz, 28GHz, 45GHz, 60GHz are selected. Study the changes of path loss and delay spread with humidity in the storage environment at different frequencies and antenna height. When the height of the transceiver antenna is set to 1m, the 28GHz, 45GHz and 60GHz millimeter wave signals are more sensitive to humidity changes, thereby which can provide more higher perception resolution of detecting humidity in the storage environment, compared with the 2.4GHz and 5GHz frequency bands. Besides, when space humidity is constant and the moisture content of wheat is changed, the arrival time of each ray in the channel at 45GHz is longer than that at 60GHz. The above work can provide reference for the application of RF sensing technology in the humidity detection scenario.

For limited distortion source coding, it is generally considered that the minimum value of the coding average distortion is 0, and the maximum value is the minimum distortion value of making R(D) = 0. This is the definition domain of the information rate distortion function. In this paper, the upper and lower bounds of the information rate distortion function R(D) are derived and computed for the typical sources. The results show that the lower bound of the coding average distortion D is related to the symbol distortion function, which can further improve the theory of limited distortion source coding.