A method for distance measurement according to the echo running time method

摘要

1464424 Echo ranging ELECTROACUSTIC GmbH 3 April 1974 [7 April 1973] 14852/74 Heading G1G A sonic or ultrasonic pulse echo-location system including a visible or audible indicating arrangement includes means for modulating an auxiliary signal, on to the transmitted signal, at a frequency distinct therefrom. The detected signal is demodulated to extract the auxiliary signal which is used to control the indicator so that extraneous received signals may be distinguished or removed, In Fig. 1, the main signal e.g. 25KHz is mixed with the auxiliary signal e.g. 1KHz in modulator 3. Switch 4, activated by timer 5 provides pulses of the combined signal at the input of power amp. 6, the output from which is fed via T-R switch 7 to transmit/ receive transducer 8. Signals received by transducer 8 are passed through T-R switch to input amplifier 9. The amplified signal 10 is fed to both demodulator 16, and delay 12, which may be a delay line or a shift register. The output from delay 12 is amplified at 13 and used to modulate the horizontal deflection circuit for C.R.T. display 14. The auxiliary signal is extracted from the received signal in demodulator 16 and further selectivity is obtained in filter 17, which has a particular delay corresponding to its time constant, which delay is introduced into the signal amplified at 13 by delay 12. The auxiliary signal is then rectified by diode 18 and applied as a further control signal for C.R.T. display 14 whereby any echo signal may reach the horizontal deflection circuit in CRT 14 but the trace is only brightened when the auxiliary signal is simultaneously detected to produce bright traces (22), whereas extraneous signals produce dim traces (23). In further embodiments, the frequency of the auxiliary signal produced by oscillator 2 may be varied - with corresponding variation of filter 17 and delay 12, or the indicating arrangement may be by electro-sensitive paper, in which case amplifier 13 is outputted by line 20 and the combined signal used to vary input sensitivity.