Radio-photon multiplex conversion of radio images of small-sized objects in complex conditions

Problem statement. Traditional analog-to-digital converters, such as parallel analog-to-digital converters, do not have sufficient bandwidth and sampling frequency to process nanosecond radio images of objects under study with subnanosecond resolution. Time-scale conversion methods that have the required bandwidth and sampling frequency have a feature associated with the need to form a sequence of probing pulses to digitize a radio image, which leads to several problems at once. The first is that the object under study can change its position in space or state during irradiation with probing pulses, which will reduce the reliability of radio image recognition. The second is that when the object under study is irradiated with a sequence of probing pulses, the phenomenon of multipath propagation of ultrashort pulses occurs in difficult conditions such as urban development, low flight altitude of a small object above the ground, complex terrain. Thus, a scientific problem arises, consisting in the need to improve the reliability of recognition of nanosecond radio images obtained in difficult conditions leading to the emergence of multipath propagation of ultrashort pulses. Objective. To increase the reproducibility of signal radio images of small-sized objects using the radio-photonic multiplex conversion method. Results. The reproducibility of nanosecond radio images with subnanosecond resolution under Rician interference conditions was studied. The inclusion of a radio-photonic multiplex converter in the receiving circuit of the radio imager allows increasing the reproducibility of the signal radio image by 28% at a selected threshold of the correlation coefficient of 0.90 under the influence of multipath interference with a signal-to-interference ratio of 12 dB for 30 cycles of iterative formation of an ultrashort pulse, relative to the use of a radio-photonic repeater with feedback. Practical significance. The obtained results allow us to conclude that it is reasonable to use the radio-photonic multiplex conversion method to increase the reliability of reproducing single nanosecond radio images under difficult conditions for active radio imaging tasks.