Acoustic sounding
First Claim
1. A method of locating temperature and/or velocity discontinuities in the lower atmosphere, comprising the steps of:
- generating an input signal comprising a chirp including a sequence of different audio tones, employing said input signal to drive an acoustic transmitter to effect the transmission of an acoustic chirp into the atmosphere, receiving and detecting an acoustic echo from said transmitted acoustic chirp and generating an echo signal comprising at least a portion of said sequence of tones, comparing the sequence of tones in the input signal with the time-shifted sequence of tones in the echo signal and deriving a first output signal indicative of the time delay between transmission of the transmitted chirp and detection of said echo, said time delay also being indicative of the location of a discontinuity in the atmosphere.
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Accused Products
Abstract
Methods and apparatus for atmospheric sounding using acoustic chirps are disclosed, the transmitted and echo chirps being compared in a mixer that yields frequency sums and differences. Preferably, the mixing is performed as a complex multiplication in the Fourier domain. In one system (1) a signal generator (5) such as a PC sound card drives a loudspeaker (3) that serves as a transmitter and echo pulses are detedcted by a microphone (4) that serves as a receiver. Chirps transmitted by the loudspeaker (3) travel by different paths (7a and 7b) due to reflection from TILS or thermal inversion layers (2a and 2b) at different altitudes. The transmitted and echo chirp signals are compared in a mixer (6) from which various outputs (8 and 9) can be generated. One output (8) might be the magnitude of the difference between the transmitted and echo chirp tones, instant by instant, which is indicative of the altitudes of the respective TILs. The other output (9) might be the phase shift in an echo tone with transit time, which is indicative of vertical wind velocity at different altitudes. Such sounding methods and apparatus are useful for weather research, prediction of plume dispersal and the design of microwave links to minimize multipath fading.
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Citations
14 Claims
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1. A method of locating temperature and/or velocity discontinuities in the lower atmosphere, comprising the steps of:
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generating an input signal comprising a chirp including a sequence of different audio tones, employing said input signal to drive an acoustic transmitter to effect the transmission of an acoustic chirp into the atmosphere, receiving and detecting an acoustic echo from said transmitted acoustic chirp and generating an echo signal comprising at least a portion of said sequence of tones, comparing the sequence of tones in the input signal with the time-shifted sequence of tones in the echo signal and deriving a first output signal indicative of the time delay between transmission of the transmitted chirp and detection of said echo, said time delay also being indicative of the location of a discontinuity in the atmosphere. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. Apparatus for use in atmospheric sounding comprising:
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means for generating and input signal comprising a chirp that includes a sequence of different audio tones, an acoustic transmitter connected to said generating means adapted to effect the transmission of an acoustic chirp into the atmosphere upon receiving said input signal, means for receiving and detecting an acoustic echo from an acoustic chirp transmitted into the atmosphere by said transmitter, said receiving means being adapted to generate an echo signal comprising at least portion of said sequence of tones, and comparator means connected to said generator means for receiving said input signal and connected to said receiving means for receiving said echo signal, said comparator means being adapted to compare the tones in said input signal with the tones in said echo signal as they are received and to derive a first output signal indicative of the frequency difference there between. - View Dependent Claims (11, 12, 13, 14)
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Specification