Patent RU-2765727-C1 (RU)
Title: Frequency method for range measurement with the measurement of the beat frequency by a holographic measuring system
Inventor: Gabrielyan Dmitrij Davidovich
IPC: G01S13/00
Filed: 2021-04-26
Granted: 2022-02-02
Abstract: FIELD: radar technology.  
     SUBSTANCE: invention relates to the field of radar technology and can be used in equipment for measuring the range of a location object. Essence: in the frequency method for measuring range, which consists in forming a radio signal with linear frequency modulation, the frequency of which varies according to a sawtooth law, and the generated radio signal is radiated in the direction of the target, the radio signal reflected by the target is received, the frequency of the radio signal reflected by the target is measured, a signal is formed at a beat frequency equal to the difference between the frequency of the radio signal emitted at a given time and the frequency of the radio signal at a time preceding the present for a delay time, the value of the beat frequency is determined, based on the measured value of the beat frequency, a decision is made about the range to the target. According to the method, the exact measurement of the beat frequency is carried out using a holographic measuring system based on a holographic interferometer implementing the spatial-spectral method for holographic interferometry. The spectral analysis of the signal at the beat frequency is carried out not using a set of narrow-band filters, but according to the parameters of the spatial-spectral distribution of the intensity of the optical field in the generated interferogram. A coherent light stream with a spherical wavefront is formed and directed to a reflective-transmitting hologram of a holographic interferometer. This coherent light stream partially diffracts from the reflective-transmitting hologram of the holographic interferometer, and partially passes through the reflective-transmitting hologram of the holographic interferometer and is reflected by its flat mirror. An electric signal proportional to the generated signal at the beat frequency modulates the phase or curvature of the wavefront of a coherent light flux with a spherical wavefront, or modulates a signal at the beat frequency of a part of this coherent light flux that has passed through a reflective-transmitting hologram of a holographic interferometer and is reflected by a flat mirror of a holographic interferometer. The coherent light flux reflected by the flat mirror of the holographic interferometer is directed to the reflective-transmitting hologram of the holographic interferometer, through which it partially passes again, but in the opposite direction. Using a coherent luminous flux with a spherical wavefront incident on a reflective-transmitting hologram of a holographic interferometer and partially diffracted from this hologram, and a coherent luminous flux passed through a reflective-transmitting hologram of a holographic interferometer, reflected through a flat mirror of a holographic interferometer and partially re-passed through a reflective-transmitting hologram of a holographic interferometer, but in the opposite direction, an interferogram is formed. The spatial-spectral distribution of the intensity of the optical field in the plane of the generated interferogram is analyzed, changing in accordance with changes in the electrical signal at the beat frequency modulating the phase or curvature of the wavefront of one of the two interfering light streams. Based on the results of the analysis of the parameters of the spatial-spectral distribution of the intensity of the optical field in the generated interferogram, the value of the beat frequency is determined. 
     EFFECT: increasing the accuracy and resolution of measuring the range of the location object.  
     1 cl, 2 dwg