Doppler speed meter

Claim 2

Radar apparatus for measuring a Doppler shift between the frequencies of a transmitted radar signal and a reflected radar signal, comprising means to provide a difference signal, means to select those cycles of the difference signal that have an amplitude above a predetermined limit and a period within predetermined limits of a mean period derived from the periods of previously selected cycles, means to provide pulsiform signals, each pulsiform signal corresponding to a resepective selected cycle and having an algebraic sign depedent on the period of said respective cycle compared to said mean period, and means for integrating the pulsiform signals for providing a signal proportional to the Doppler shift

Claim 3

Apparatus as claimed in claim 1 wherein the means to select comprises a trigger operative each time the amplitude of the difference signal passes in a predetermined direction through a predetermined value to provide a train of trigger pulses, means to initiate a ramp signal in response to a said trigger pulse, means respectively to sense when the ramp signal reaches first, second and third values, gating means to receive signals from the sensing means, and to receive the trigger pulses, the gating means producing a said pulsiform signal of one algebraic sign if the trigger pulse immediately following the aforementioned trigger pulse occurs while the ramp signal is between its first and second values, the gating means producing a pulsiform signal of the other algebraic sign if the said immediatedly following trigger pulse occurs while the ramp signal is between its second and third values.

Claim 4

Apparatus as claimed in claim 2 wherein the integrating means comprises means to provide a stored quantity, indicative of the Doppler shift and being the integral of previously-occuring pulsiform signals, and means to adjust said stored quantity according to the algebraic sign of each pulsiform signal, a feedback loop controlling the rate of change with time of the ramp signal as a function of said stored quantity.

Claim 5

Apparatus as claimed in claim 3 comprising a logic gate, the sensing means operating when the ramp signal reaches its third value to terminate said ramp signal and to set the logic gate to a predetermined state, the logic gate changing state in response to a subsequently occuring trigger pulse to re-initiate said ramp signal.

Claim 6

Apparatus as claimed in claim 1, comprising a microwave semiconductive device arranged to operate as an oscillator to provide the transmitted radar signal, and as a mixer to mix the transmitted radar signal and the reflected radar signal, for developing said difference signal.

Claim 7

Apparatus as claimed in claim 5 further comprising a cavity resonator, said device being a Gunn effect device disposed in said cavity resonator, a voltage stabilizing circuit being arranged to drive said Gunn effect device.

Claim 8

Apparatus as claimed in claim 6 wherein the voltage stabilizing circuit includes a Zener diode for providing a reference voltage, means to compare a drive voltage applied to the Gunn effect device with the reference voltage and means to stabilize the drive voltage according to said comparison.

Claim 9

Apparatus as claimed in claim 7 wherein the means for stabilizing and comparing the drive voltage comprises a transistor having its emitter-collector path in series with the Zener diode across the Gunn effect device, the base of the transistor being biassed by a potential divider also connected across the Gunn effect device.

Claim 10

Apparatus as claimed in claim 7 wherein the means for stabilizing and comparing the drive voltage comprises a transistor pair adapted to compare the said drive voltage with the reference voltage and to control the drive voltage by means of a further transistor.

Claim 11

Apparatus as claimed in claim 1 comprising means to derive from the integrator output an indication of speed.

Claim 12

Apparatus as claimed in claim 10 comprising an active integrator to integrate the integrator output to provide an indication of distance.

Claim 13

A measuring system comprising two radar apparatuses fixed relative to each other, one for sensing speed in one direction and the other for sensing speed in a direction orthogonal to the said one direction, each radar apparatus comprising means to transmit a radar signal and to receive a reflected said radar signal, each apparatus including means to provide a difference signal, means to select those cycles of the difference signal that have an amplitude above a predetermined limit and a period within predetermined limits of a mean period derived from the periods of previously selected cycles, means to provide pulsiform signals, each pulsiform signal corresponding to a respective selected cycle and having an algebraic sign dependent on the period of said respective cycle compared to said mean period, and means to integrate the pulsiform signals for providing a signal proportional to the Doppler shift, each apparatus having means for utilizing its integrator output as an indication of said speed.

Claim 14

A measuring system comprising two radar apparatuses fixed relative to each other, one for sensing speed in one direction and the other for sensing speed in a direction orthogonal to the said one direction, each radar apparatus comprising means to transmit a radar signal and to receive a reflected said radar signal, each apparatus including means to provide a difference signal, means to select those cycles of the difference signal that have an amplitude above a predetermined limit and a period within predetermined limits of a mean period derived from the periods of previously selected cycles, means to provide pulsiform signals, each pulsiform signal corresponding to a respective selected cycle and having an algebraic sign dependent on the period of said respective cycle compared to said mean period, and means to integrate the pulsiform signals for providing a signal proportional to the Doppler shift, each apparatus having means for utilizing its integrator output as an indication of said speed.

Claim 15

A system as claimed in claim 12 comprising means to compute from the indications provided by each said apparatus the magnitude and direction of a velocity vector whose components are the said indications.

Claim 16

A system as claimed in claim 13 comprising a resolver having orthogonal axes of resolution, a rotor, and two stator coils, means to derive respective A.C. signals from said indications of speed, means to apply said A.C. signals to the two stator coils of the resolver, means to rotate the rotor of the resolver and to utilize the angular position thereof as an indication of the direction of said vector when the resolved output on the other axis of resolution is zero, and means to utilize the rEsolved output on the other axis of resolution as an indication of the magnitude of said vector in said direction.

Claim 17

A system as claimed in claim 14 comprising an active integrator arranged to integrate the said indication of the magnitude of the said velocity to provide an indication of distance.

Claim 18

A system as claimed in claim 14 comprising means to utilise the said angular position of the rotor to correct a steering compass.

Claim 19

Apparatus as claimed in claim 1 comprising means to derive from the integrator output an indication of a quantity related to speed by time.

Claim 20

A measuring system comprising two radar apparatuses fixed relative to each other, one for sensing a quantity related to speed by time in one direction and the other for sensing a quantity related to speed by time in a direction orthogonal to said one direction, each radar apparatus comprising means to transmit a radar signal and to receive a reflected said radar signal, each apparatus including means to provide a difference signal, means to select those cycles of the difference signal that have an amplitude above a predetermined limit and a period within predetermined limits of a mean period derived from the periods of previously selected cycles, means to provide pulsiform signals, each pulsiform signal corresponding to a respective selected cycle and having an algebraic sign dependent on the period of said respective cycle compared to said mean period, and means to integrate the pulsiform signals for providing a signal proportional to the Doppler shift, each apparatus having means for utilizing its integrator output as an indication of said quantity related to speed by time.

Claim 21

A measuring system comprising two radar apparatuses fixed relative to each other, one for sensing a quantity related to speed by time in one direction and the other for sensing a quantity related to speed by time in a direction orthogonal to said one direction, each radar apparatus comprising means to transmit a radar signal and to receive a reflected said radar signal, each apparatus including means to provide a difference signal, means to select those cycles of the difference signal that have an amplitude above a predetermined limit and a period within predetermined limits of a mean period derived from the periods of previously selected cycles, means to provide pulsiform signals, each pulsiform signal corresponding to a respective selected cycle and having an algebraic sign dependent on the period of said respective cycle compared to said mean period, and means to integrate the pulsiform signals for providing a signal proportional to the Doppler shift, each apparatus having means for utilizing its integrator output as an indication of said quantity related to speed by time.

Claim 22

A system as claimed in claim 18 comprising means to compute from the indications provided for each said apparatus the magnitude and direction of a velocity and time-related vector whose components are the said indications.

Claim 23

A system as claimed in claim 19 comprising a resolver having orthogonal axes of resolution, a rotor, and two stator coils, means to derive respective A.C. signals from said indications of speed, means to apply said A.C. signals to the two stater coils of the resolver, means to rotate the rotor of the resolver and to utilize the angular position thereof as an indication of the direction of said vector when the resolved output on the other axis of resolution is zero, and means to utilise the resolved output on the other axis of resolution as an indication of the magnitude of said vector in said direction.

Claim 24

In combination with an air cushion vehicle, a measuring system comprising two radar apparatuses fixed relative to each other, one for sensing speed in one direction and the other for sensing speed in a direction orthogonal to the said one direction, each radar apparatus comprising means to transmit radard signal and to receve a reflected said radar signal, each apparatus including means to provide a difference signal, means to select those cycles of the difference signal that have an amplitude above a predetermined limit and a period within predetermined limits of a mean period derived from the periods of previously selected cycles, means to provide pulsiform signals, each pulsiform signal corresponding to a respective selected cycle and having an algebraic sign dependent on the period of said respective cycle compared to said mean period, and means to integrate the pulsiform signals for providing a signal proportional to the Doppler shaft, each apparatus having means for utilizing its integrator output as an indication of said speed, said measuring system being located in said vehicle and said directions being in the yaw plane of the vehicle.

Claim 25

In combination with an air cushion vehicle, a measuring system comprising two radar apparatuses fixed relative to each other, one for sensing speed in one direction and the other for sensing speed in a direction orthogonal to the said one direction, each radar apparatus comprising means to transmit radard signal and to receve a reflected said radar signal, each apparatus including means to provide a difference signal, means to select those cycles of the difference signal that have an amplitude above a predetermined limit and a period within predetermined limits of a mean period derived from the periods of previously selected cycles, means to provide pulsiform signals, each pulsiform signal corresponding to a respective selected cycle and having an algebraic sign dependent on the period of said respective cycle compared to said mean period, and means to integrate the pulsiform signals for providing a signal proportional to the Doppler shaft, each apparatus having means for utilizing its integrator output as an indication of said speed, said measuring system being located in said vehicle and said directions being in the yaw plane of the vehicle.

Claim 26

In combination with a road vehicle, a measuring system comprising two radar apparatuses fixed relative to each other, one for sensing speed in one direction and the other for sensing speed in a direction orthogonal to the said one direction, each radar apparatus comprising means to transmit a radar signal and to receive a reflected saId radar signal, each apparatus including means to provide a difference signal, means to select those cycles of the difference signal that have an amplitude above a predetermined limit and a period within predetermined limits of a mean period dervied from the periods of previously selected cycles, means to provide pulsiform signals, each pulsiform signal corresponding to a respective selected cycle and having an algebraic sign dependent on the period of said respective cycle compared to said mean period, and means to integrate the pulsiform signals for providing a signal proportional to the Doppler shift, each apparatus having means for utilizing its integrator output as an indication of said speed, said measuring system being affixed to said vehicle and said directions being in the longitudinal and transverse directions of said vehicle.

Claim 27

In combination with a road vehicle, a measuring system comprising two radar apparatuses fixed relative to each other, one for sensing speed in one direction and the other for sensing speed in a direction orthogonal to the said one direction, each radar apparatus comprising means to transmit a radar signal and to receive a reflected saId radar signal, each apparatus including means to provide a difference signal, means to select those cycles of the difference signal that have an amplitude above a predetermined limit and a period within predetermined limits of a mean period dervied from the periods of previously selected cycles, means to provide pulsiform signals, each pulsiform signal corresponding to a respective selected cycle and having an algebraic sign dependent on the period of said respective cycle compared to said mean period, and means to integrate the pulsiform signals for providing a signal proportional to the Doppler shift, each apparatus having means for utilizing its integrator output as an indication of said speed, said measuring system being affixed to said vehicle and said directions being in the longitudinal and transverse directions of said vehicle.