Doppler pseudorandom noise velocimeters

Apparatus for measuring velocity and distance of a moving target within a conveying medium comprising:

• first means for generating a continuous pseudorandom ultrasonic noise signal formed of a repetitive code composed of a plurality of different elementary segments;
• means for transmitting said continuous pseudorandom ultrasonic noise signal to said moving target and said conveying medium;
• receiver means for receiving echo signals from said moving target and said conveying means, said receiver means having one output for each of said plurality of different elementary segments in said repetitive code;
• second means for generating a continuous pseudorandom ultrasonic noise signal identical to that generated by said first means, said second means for generating being selectively actuatable and having at least one output for each of said plurality of different elementary segments;
• control means interconnected to said first and second means for generating for selectively actuating said first and second means for generating to develop a delayed continuous pseudorandom ultrasonic noise signal from said second means corresponding to said continuous pseudorandom ultrasonic noise signal generated by said first means and delayed therefrom by a value representative of the distance to be scanned;
• a plurality of correlation means corresponding in number to said plurality of different elementary segments in said repetitive code, each of said plurality of correlation means being connected to a corresponding one of said outputs from said receiver means and said second means for generating to form a separate band for each of said plurality of different elementary segments;
• a plurality of sampling means, each of said plurality of sampling means being connected to one of said plurality of correlation means to receive correlation values to be sampled therefrom;
• a plurality of filter means for removing constants in each of said correlation values representing echo signals from said conveying medium, each of said plurality of filter means being connected to one of said plurality of sampling means;
• and
• summing means connected to each of said plurality of filter means for reconstituting a DOPPLER low frequency signal from the correlation values sampled by said plurality of sampling means.