Method and device for matching the reflector of an acoustic echo ranging system
AssigneeBertin & Cie
InventorJean-Michel Fage
Life of this patent
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Abstract
The reflector of an acoustic echo ranging system is matched so as to make up for the influence of the temperature at the bottom of the reflector, on the measurement of the back-reflected signal. The acoustic signal receiver being stationary the transmission frequency is controlled by a temperature responsive electronic circuit so that the receiver is always located at the same pressure antinode. Alternatively, the transmission frequency being fixed, the position of the receiver is controlled by a temperature responsive mechanical gear causing the position of the receiver to coincide with the same pressure antinode.
Claims11
In an acoustic echo ranging system having a reflector paraboloid and designed for transmitting an acoustic signal towards a target, receiving the resulting echo signal and processing said signals for data acquirement, a method of matching the reflector in order to improve the quality of reception of said echo signal as picked up by a horn having an exit plane which, under optimum echo signal reception conditions, lies adjacent the focal point of said paraboloid, the focal length of which is a whole multiple of half the transmitted wavelength, this multiple being a characteristic of the configuration of said paraboloid whose reception conditions are upset by the appearance of a pattern of interference fringes which is established naturally between the bottom of the paraboloid and the horn and which evolves with the temperature prevailing at the bottom of the reflector, wherein the improvement comprises the step of automatically correcting this evolution in the pattern of interference fringes by an adjustment dependent on said temperature whereby the position of the exit plane of the horn is caused to coincide with the same pressure antinode located as being spaced from the bottom of the paraboloid by said multiple of the half-wavelength.
An acoustic echo ranging system of the kind designed for transmitting an acoustic signal towards a target, receiving the corresponding echo signal retro-diffused by said target and processing said signals for data acquirement, said system comprising the combination of:
- (i) a sound reflector having the shape of a paraboloid, the focal length of which is a whole multiple of half the transmitted wavelength, this multiple being a characteristic of the configuration of said paraboloid whose reception conditions are upset by the appearance of a pattern of interference fringes which is established naturally between the bottom of the paraboloid and the focal point thereof and which evolves with the temperature prevailing at the bottom of the paraboloid,
- (ii) a sound pick-up horn having an exit plane which, under optimum echo signal reception conditions, lies adjacent said focal point, and
- (iii) a temperature sensor positioned adjacent said horn for causing said exit plane to coincide with the same pressure antinode located as being spaced from the bottom of the paraboloid by said multiple of the half-wavelength, whereby the evolution in said pattern of interference fringes is automatically corrected by an adjustment dependent on said temperature.
Dependencies are inferred from the claim text.