| 摘要 |
1291849 Echo sounding; phase measuremerit AUSTRALIA DEPARTMENT OF SUPPLY SECRETARY OF STATE FOR 22 Dec 1969 [23 Dec 1968] 62456/69 Headings H3A and H4D In an acoustic pulse-echo system for atmospheric sounding, the echo time and/or duration and/or intensity and direction of reception of upwardly transmitted energy back-scattered from regions of turbulence is recorded. The invention has application in the detection of clear air turbulence, the landing of aircraft, the determination of fog depth and diffusion of pollutants, gun-laying and general tropospheric research. In the Fig. 2 embodiment arrays 1, 2, 3, 4 of transducers are switched by relay group 6 between a transmitting (TX) and a receiving (RX) mode. In the TX mode all four arrays are pulsed together with a selected carrier frequency or frequency band (e.g. a "chirp" signal). In the RX mode the outputs of arrays 1 + 2 + 3 + 4 are summed at receiver 11 and the combined amplitude intensity modulates a facsimile recorder 10 to give e.g. a height/time of day plot. The mean wind velocity deviates the sounding beam and its north-south component is measured by determining the delay or phase difference between the combined output of arrays 1+ 2 and the combined output of arrays 3+ 4 in detector 12. In detector 12, signals 1+ 2 and 3 + 4 are converted to I.F. signals in mixers 14, 18 to which are fed local oscillator signals from fixed frequency oscillator 15 and variable frequency oscillator 19 respectively. The I.F. signals are amplified and limited at 17, 20, then phase compared at 16 to provide an error signal which is low-pass filtered at 21 and locks the frequency of oscillator 19. The phase difference between the two oscillators is then a measure of the wind velocity component and is detected at 22 and indicated at 23. The East- West velocity component is similarly derived at 13 from the phase difference between 2 + 3 and 1+4. In a modification a tristatic or bistatic transmission/reception arrangement is used, e.g. comprising a pair of spaced trans- ducer arrays with their beams offset from the vertical and energy transmitted from one being received at both on return, whereby Doppler techniques can be used to determine radial components of wind velocity. A transducer may comprise a concrete paraboloid reflector. |
