Clutter tracker using a smoothed doppler frequency measurement

Claim 2

A radar clutter tracker system responsive to clutter frequencies, said system having a dual channel delay subsystem, comprising the combination: a dual channel analog-to-digital converter fed by a pair of quadrature signals; a first digital circuit electrically connected to the converter; a second digital circuit electrically connected to the converter; and a crossing detector the input of which is electrically connected to the converter and the first and second digital circuits.

Claim 3

The system of claim 1 including a pair of binary logic AND gates electrically connected to the crossing detector.

Claim 4

The system of claim 2, including an up-down counter electrically connected to the outputs of the AND gates.

Claim 5

The system of claim 3, including: a clutter detector circuit; and a dividing circuit electrically connected to the up-down counter and the clutter detector circuit.

Claim 6

The system of claim 4 including a digital filter circuit electrically connected to the output of the dividing circuit.

Claim 7

The system of claim 1, including a clutter detector circuit electrically connected to the converter.

Claim 8

The system of claim 6, wherein the clutter detector circuit includes a pair of comparators electrically connected to the output of the converter.

Claim 9

A radar clutter tracker system responsive to radar signals for controlling the clutter frequency comprising: phase angle measurement means responsive to said radar signals, said phase angle measurement means having a resolution of 90° and submultiples thereof; scaling means for developing a digital error signal from the resultant of said phase angle measurement means; digital-to-analog converter means for accepting converted error signals; voltage controlled oscillator means accepting said converted error signal for controlling the frequency thereof; coding means wherein a phase angle excursion greater than one resolution unit is ignored; delay means responsive to signals from a radar system; threshold means for eliminating radar signals below a predetermined signal level; first logic means determining a clutter gate, said phase angle measurement means also being responsive to signal output from said delay means and signals from said radar system; second logic means responsive to signal output from said phase angle measurement means and said clutter gate; first counter means for counting the number of clutter gates existing during a given sample interval; second counter means for counting phase angle units occurring during a given sample interval, said scaling means also being responsive to both first and second counter means and developing therefrom a numerical frequency error signal; and αβ tracking and predicting means for deriving a linear error prediction to said digital-to-analog converter means.

Claim 10

A radar clutter tracker system responsive to radar signals for controlling the clutter frequency comprising: phase angle measurement means responsive to said radar signals, said phase angle measurement means having a resolution of 90° and submultiples thereof; scaling means for developing a digital error signal from the resultant of said phase angle measurement means; digital-to-analog converter means for accepting converted error signals; voltage controlled oscillator means accepting said converted error signal for controlling the frequency thereof; coding means wherein a phase angle excursion greater than one resolution unit is ignored; delay means responsive to signals from a radar system; threshold means for eliminating radar signals below a predetermined signal level; first logic means determining a clutter gate, said phase angle measurement means also being responsive to signal output from said delay means and signals from said radar system; second logic means responsive to signal output from said phase angle measurement means and said clutter gate; first counter means for counting the number of clutter gates existing during a given sample interval; second counter means for counting phase angle units occurring during a given sample interval, said scaling means also being responsive to both first and second counter means and developing therefrom a numerical frequency error signal; and αβ tracking and predicting means for deriving a linear error prediction to said digital-to-analog converter means.

Claim 11

The system of claim 8 wherein said first logic means comprises a logic OR circuit responsive to output signal from said threshhold means; shift register means responsive to signal output from said OR circuit; logic AND means responsive to signal output from said OR circuit and said shift register means; and bistable circuit means responsive to signal output from said logic AND circuit and said shift register means.

Claim 12

A radar clutter tracker system using a smoothed doppler frequency measurement comprising in combination: delay means responsive to in-phase and quadrature signals from a radar system; comparison level means responsive to in-phase and quadrature signals from the radar system; phase angle measurement means responsive to both instant and delayed in-phase and quadrature signals from a radar system; first logic means responsive to both in-phase and quadrature signal levels supplied from the comparison level means; shift register means responsive to output signal from said first logic means; second logic means responsive to output signal from said first logic means and said shift register means and forming therefrom a clutter gate; third logic means responsive to output signals from said phase angle measurement means and said clutter gate; scaling means for developing a digital error signal from the resultant of said phase angle measurement means and said clutter gate; signal smoothing means for reducing second order error signal effects; digital-to-analog converter means for converting said digital error signal; and voltage controlled oscillator means accepting said converted error signal for controlling the frequency thereof.

Claim 13

A radar clutter tracker system using a smoothed doppler frequency measurement comprising in combination: delay means responsive to in-phase and quadrature signals from a radar system; comparison level means responsive to in-phase and quadrature signals from the radar system; phase angle measurement means responsive to both instant and delayed in-phase and quadrature signals from a radar system; first logic means responsive to both in-phase and quadrature signal levels supplied from the comparison level means; shift register means responsive to output signal from said first logic means; second logic means responsive to output signal from said first logic means and said shift register means and forming therefrom a clutter gate; third logic means responsive to output signals from said phase angle measurement means and said clutter gate; scaling means for developing a digital error signal from the resultant of said phase angle measurement means and said clutter gate; signal smoothing means for reducing second order error signal effects; digital-to-analog converter means for converting said digital error signal; and voltage controlled oscillator means accepting said converted error signal for controlling the frequency thereof.

Claim 14

The system of claim 10 wherein said phase angle measurement means has a resolution of 90° and submultiples thereof.

Claim 15

The system of claim 11 including coding means wherein a phase angle excursion greater than one resolution unit is ignored.

Claim 16

The system of claim 12 wherein said signal smoothing means comprises αβ frequency tracking and prediction means.