Within-pulse doppler scanning

Claim 3

A method according to claim 1 wherein the stored replica signal is wholly or partly refreshed between samples of the electrical signal.

Claim 4

A method according to claim 1 wherein correlation is performed against two stored replica signal profiles having a mutual phase difference.

Claim 5

A method according to claim 2 or 3 wherein the waveform is that of a sonar pulse.

Claim 6

Apparatus for detecting a Doppler-shifted waveform in an electrical signal including: (a) means for generating a replica signal derived from the waveform prior to Doppler shift; (b) means for storing samples of the electrical signal comprising a first storage device having a plurality of storage positions and a sampling clock connected to the storage device and arranged for sampling the electrical signal at uniform sampling intervals; (c) means for storing samples of the replica signal comprises a second storage device having a plurality of storage positions and a sampling clock connected to the second storage device and arranged for sampling the replica signal at intervals changing in accordance with a first geometric progression such that the profile of the stored replica samples has a progressively increasing distortion along its length compared to the replica signal; (d) scanning means connected to the second storing device for cyclically moving the stored replica signal profile through a range of storage positions; and (e) correlating means including an array of multipliers connected to respective selected storage positions of the first and second storage devices, the connected storage positions being uniformly spaced in the first signal storage device and being spaced in the second replica profile storage device such that the ratio of the numbers of storage positions between successive multiplier connections to said first storage device is substantially a geometric progression in the same sense as said first geometric progression so as to cancel the progressively increasing distortion of the replica signal profile.

Claim 7

Apparatus for detecting a Doppler-shifted waveform in an electrical signal including: (a) means for generating a replica signal derived from the waveform prior to Doppler shift; (b) means for storing samples of the electrical signal comprising a first storage device having a plurality of storage positions and a sampling clock connected to the storage device and arranged for sampling the electrical signal at uniform sampling intervals; (c) means for storing samples of the replica signal comprises a second storage device having a plurality of storage positions and a sampling clock connected to the second storage device and arranged for sampling the replica signal at intervals changing in accordance with a first geometric progression such that the profile of the stored replica samples has a progressively increasing distortion along its length compared to the replica signal; (d) scanning means connected to the second storing device for cyclically moving the stored replica signal profile through a range of storage positions; and (e) correlating means including an array of multipliers connected to respective selected storage positions of the first and second storage devices, the connected storage positions being uniformly spaced in the first signal storage device and being spaced in the second replica profile storage device such that the ratio of the numbers of storage positions between successive multiplier connections to said first storage device is substantially a geometric progression in the same sense as said first geometric progression so as to cancel the progressively increasing distortion of the replica signal profile.

Claim 8

Apparatus according to claim 5 wherein each storage device comprises an array of discrete series-connected elements providing discrete storage positions, and each sampling clock is operative to move a stored signal one element along the respective array to accommodate each successive signal sample.

Claim 9

Apparatus according to claim 6 wherein the elements are charge-coupled devices.

Claim 10

Apparatus according to claim 5 wherein the scanning means is arranged to move the replica signal profile through a cycle of storage positions in each interval between successive samples of the electrical signal.

Claim 11

Apparatus according to claim 8 wherein the correlating means is arranged to provide an output signal indicating degree of correlation and the apparatus includes a visual display device adapted to display the output signal as a function of storage position of the replica signal profile.

Claim 12

Apparatus according to claim 9 wherein the visual display device is calibrated to indicate degree of Doppler shift in terms of replica signal profile storage position at maximum correlation.

Claim 13

Apparatus according to claim 10 wherein the visual display device is arranged to indicate time elapsed between generation of the replica signal and detection of maximum correlation.

Claim 14

Apparatus according to claim 11 wherein the output intensity of the visual display device varies in accordance with degree of correlation.

Claim 15

Apparatus according to claim 12 incorporated in a pulse-echo target location system and wherein the visual display device has a horizontal time base responsive to replace signal profile storage position and a vertical time base responsive to time elapsed from replica generation or pulse emission, the horizontal and vertical time bases being calibrated respectively in terms of range and relative velocity of target.

Claim 16

Apparatus according to claim 13 wherein the target location system is a sonar system.

Claim 17

Apparatus according to claim 5 in which the replica signal storage device is adapted for storing two replica signal profiles having a 90° phase difference therebetween, the correlating means is arranged to produce respective output signals from each stored replica signal profile and the electrical signal, and there is provided signal processing means arranged to sum the squares of the correlation output signals.

Claim 18

Apparatus according to claim 5 including a digital store arranged to store the sampled replica signal prior to storage in the replica profile storage device and to refresh the stored replica signal profile periodically.

Claim 19

Apparatus according to claim 16 including a multiplexing device arranged between the digital store and the replica signal profile storage device for selective partial refreshing of the stored replica signal profile.

Claim 20

Apparatus according to claim 5 wherein the array of multipliers is an analogue switch network.

Claim 21

Apparatus according to claim 5 wherein the multiplier array is an array of microprocessors.