Canadian Patents & Development Ltd.

Government of the United States of America, As Represented by the Secretary of Commerce

Societe Canadienne Des Brevets Et D'exploitation Limitee

David M Farmer

George A May

Steven F Clifford

Jane A Verrall

R Del Huston

Signal phase delay may be accurately measured by transmitting a pseudo-random noise coded reference signal, deriving in-phase and quadrature components of the received coded signal and then separately decoding the in-phase and quadrature components. This technique effectively compresses the transmitted signal pulse to a very narrow width (thereby simplifying discrimination of separate pulses with similar arrival times) while magnifying the pulse amplitude (thereby enhancing the signal to noise ratio).

Phase measurements using pseudo-random code

A method of simulating phase coherent signal reflections in media containing randomly distributed targets capable of scattering signals transmitted through the media, wherein the energy of signals directly scattered by the targets is significantly greater than the energy of signals multiply scattered by the targets. A reference signal having a wavelength which is small in comparison to the mean spacing between the targets is modulated and then transmitted through the target-containing medium. The targets produce scattered echoes of the signal, from which normalized in-phase and quadrature components are derived and separately, cumulatively summed, 'n' times, until their variance becomes a linear function of 1/n.

Method and apparatus for simulating phase coherent signal reflections in

A method of determining the bearing 'S' of a signal transmitter relative to a remote signal receiver. A signal pulse having a high signal to noise ratio is transmitted and sampled at closely spaced receivers displaced from the transmitter by a distance 'D'. Sampled phase components are derived at each receiver by deriving in-phase and quadrature components of the sampled pulse and by deriving the arctangent of each such component. The arrival time of the sampled pulses is measured by applying a least squares Gaussian fit to the modulus or to the amplitude envelope of the pulse samples. The difference '.delta.t' between the time of arrival of the pulse at each receiver is determined and then the approximate phase difference 2.pi..omega..delta.t between the sampled pulses is determined where '.omega.' is the carrier frequency of the transmitted pulse. The phase difference is then applied to resolve the phase ambiguity of the phase components and the bearing 'S' is then calculated. The method also facilitates correction of errors in the apparent transmitter bearing which are introduced by relative medium movement, in which the signal pulse is transmitted through a medium which moves with a component of velocity 'u' perpendicular to the acoustic path between the transmitter and receivers, thereby causing the bearing to appear to deviate from the actual bearing of the transmitter relative to the receivers; and, by small scale fluctuations in sound speed between the transmitter and each of the receivers.

Method for underwater acoustic direction sensing

A system and method are disclosed for acoustic scintillation liquid flow measurement. Measurement is carried out by acoustic beams transmitted perpendicular to the direction the component of liquid flow to be measured, with both phase and amplitude measurements being made to enable generation of accurate speed of flow indications which are indicative of liquid flow through a broad area being monitored as opposed to a single point therein. In one realization of this invention, a pair of projectors are mounted on one side of the flow area, such as a channel to be monitored, and a pair of receivers are mounted on the other side of the flow area with pulsed acoustic signals from each of the projectors being transmitted in separate parallel paths through the liquid, such as water, to the receivers. At the receivers, electrical signals indicative of received acoustic signals in each path are complex demodulated after which the demodulated outputs are shaped, converted and then coupled to a microcomputer for evaluation and, responsive thereto, providing the indication of liquid flow speed.

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Saanichton, Canada

David M Farmer