Microwave interference pattern sensor

Claim 2

Velocity sensing apparatus comprising: a. means to illuminate an area on the ground with radar energy; b. at least two receiving antennas spaced in the direction in which velocity is to be sensed; c. means to measure the time required for the back-scattered radar energy to transverse the distance between the two antennas whereby from said time, velocity may be determined said means comprising: d. a first power sensor coupled to one receiving antenna; e. a second power sensor coupled to the other receiving antenna; f. first means to sum the outputs of said first and second power sensors; g. first means to difference the outputs of said first and second power sensors; and h. first means to track the cross over of the sum and difference outputs obtained from said summing and differencing means.

Claim 3

The invention according to claim 1 wherein said tracking means comprise: a. a variable frequency oscillator; b. a first mixer having as inputs the output of said oscillator and the output of said summing means; c. a second mixer having as inputs the output of said oscillator and the output of said differencing means; d. a first square law detector; e. a second square law detector; f. a first low pass filter coupling the output of said first mixer to said first square law detector; g. a second low pass filter coupling the output of said second mixer to said second square law detector; and h. second differencing means having as inputs the outputs of said first and second square law detectors and providing its output as a control input to said variable frequency oscillator whereby the oscillator frequency will be the crossover frequency of the sum and difference signals.

Claim 4

The invention according to claim 2 wherein three receiving antennas are provided with first and second antennas placed side by side along a direction prependicular to that along which velocity is to be measured and a third spaced from said first and second along the direction of velocity measurement with its center equal distance from the centeRs of said first and second antennas and wherein said first and second power sensors are coupled to said first and third antennas and further including: a. a third power sensor coupled to said second antenna; b. second means to sum the outputs of said third and second power sensors; c. third means to difference the outputs of said third and second power sensors; d. second tracking means identical to said first tracking means to track the crossover of the sum and difference outputs from said second summing and differencing means; and e. means having as inputs the outputs of said first and second tracker to resolve said outputs to provide an output indicative of the time to traverse the distance from a line connecting the centers of said first and second antennas to the center of said third antenna and a drift angle representing the angle which the velocity vectors makes with a line along said distance.

Claim 5

The invention according to claim 3 wherein said resolving means comprise: a. third means to sum the outputs of said first and second trackers; b. fourth means to difference the outputs of said first and second trackers; c. first means to multiply the output of said third summing means by sin epsilon where epsilon is the angle which a line from the center of said first to the center of said third antenna make with a line from the center of said third antenna perpendicular to a line passing through the centers of the first and second antennas; d. second means to multiply the output of said differencing means by cos epsilon ; e. a resolver having the outputs of said first and second means as primary inputs; and f. a servo system including an amplifier and a motor said motor coupled to the shaft of said resolver and said system obtaining its error input from one secondary winding of said resolver and adapted to position said resolver shaft to null out said error whereby the output of the second secondary winding of said resolver will represent said time and said resolver shaft angle will represent said drift angle.

Claim 6

The invention according to claim 4 and further including means to convert said time output to an output representative of velocity.

Claim 7

The invention according to claim 5 wherein said means to convert is a voltage controlled period generator.

Claim 8

The invention according to claim 6 wherein said first and second variable frequency oscillators are voltage controlled period generators.

Claim 9

The invention according to claim 7 wherein each of said voltage controlled period generators comprise: a. a first comparator referenced to ground; b. a second comparator referenced to the input to said generator; c. a flip flop having its set and reset inputs coupled respectively to the outputs of said first and second comparators and d. an integrator having an input from the output of said flip flop and providing its output as second inputs to said first and second comparators.

Claim 10

The invention according to claim 4 wherein each of said first, second, third and fourth power sensors comprise: a. means to generate a sidestep local oscillator (LD) signal from the transmitted signal; b. a third mixer to mix said LO signal with the receiving antenna input; and c. a third square law detector coupled to said mixer and providing the final signal output.

Claim 11

The invention according to claim 9 and further including a leakage elimination filter (LEF) between said mixer and said third square law detector.

Claim 12

The invention according to claim 10 wherein said LO means comprise: a. a quadrature circuit having an input from the transmitter and providing first and second outputs in quadrature. b. an intermediate frequency (IF) oscillator providing first and second outputs in quadrature; c. a fourth mixer having as inputs said first quadrature circuit output and said first IF oscillator output; d. a fifth mixer having as inputs said second quadrature circuit output aNd said second IF oscillator output, and e. fourth means to sum the outputs of said fourth and fifth mixers.

Claim 13

The invention according to claim 11 wherein said LEF comprises: a. a sixth mixer having as inputs the output of third mixer and said first IF oscillator output; b. a seventh mixer having as inputs the output of said third mixer and said second IF oscillator output; c. a first high pass filter obtaining its input from said sixth mixer; d. a second high pass filter obtaining its input from said seventh mixer; e. an eighth mixer having as inputs the output of said first high pass filter and said first IF oscillator output; f. a ninth mixer having as inputs the output of said second high pass filter and said second IF oscillator output and, g. fifth means to sum the outputs of said eighth and ninth mixers.