Method of measuring the altitude of a target maneuvering at a very low elevation, and a tracking radar using same
First Claim
1. A method of operating a monopulse tracking radar with a given pass band for measuring the altitude of a target maneuvering at a very low elevation by determining the angular aiming error existing between the direction of the target and the aiming axis of said radar, comprising the following steps:
- deriving sum and difference signals from incoming energy reflected by a target and received by an antenna of the radar with the vector representing the sum signal;
separating an in-phase component of said difference signal colinear with the sum signal from a quadrature component thereof perpendicular to said sum signal;
successively generating a multiplicity of sampling frequencies within said pass band;
measuring said quadrature component and a deviation signal representative of an instantaneous angular aiming error, extracted from said sum signal and said in-phase component, for each of said sampling frequencies;
averaging said deviation signal and said quadrature components measured with overlapping series of successive sampling frequencies to obtain respective mean values therefor;
detecting an extreme point of substantially zero slope on a curve formed from said quadrature component; and
validating the mean value of said deviation signal for a sampling frequency corresponding to said extreme point.
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Abstract
A method of measuring the altitude of a target maneuvering at very low elevations is used to determine the instantaneous deviation of the target at various operating frequencies of a monopulse tracking radar. The quadrature component of the difference signal is evaluated at these frequencies, the mean values of the instantaneous deviation and of the quadrature component are determined for a certain number of frequency samples, and an extreme value of the mean value of the quadrature component is found to allow the corresponding mean value of deviation to be validated.
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Citations
14 Claims
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1. A method of operating a monopulse tracking radar with a given pass band for measuring the altitude of a target maneuvering at a very low elevation by determining the angular aiming error existing between the direction of the target and the aiming axis of said radar, comprising the following steps:
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deriving sum and difference signals from incoming energy reflected by a target and received by an antenna of the radar with the vector representing the sum signal; separating an in-phase component of said difference signal colinear with the sum signal from a quadrature component thereof perpendicular to said sum signal; successively generating a multiplicity of sampling frequencies within said pass band; measuring said quadrature component and a deviation signal representative of an instantaneous angular aiming error, extracted from said sum signal and said in-phase component, for each of said sampling frequencies; averaging said deviation signal and said quadrature components measured with overlapping series of successive sampling frequencies to obtain respective mean values therefor; detecting an extreme point of substantially zero slope on a curve formed from said quadrature component; and validating the mean value of said deviation signal for a sampling frequency corresponding to said extreme point. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A tracking radar of monopulse type for acertaining the altitude of a target, maneuvering at very low elevation, by processing reflected energy constituting a sum signal and a difference signal, said difference signal having an in-phase component colinear with said sum signal and a quadrature component perpendicular to said sum signal, comprising:
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a first and a second channel for respectively processing said sum signal and said difference signal; a third channel in parallel with said second channel including a π
/2 phase shifter for processing the quadrature component of said difference signal;a first demodulator with input connections to said first and second channels for deriving from the ratio of said difference and sum signals a deviation signal proportional to an angular aiming error between the direction of said target and an aiming axis of the radar at an operating frequency thereof; a second demodulator with input connections to said first and third channels for delivering a signal voltage representing said quadrature component; oscillator means for successively generating a multiplicity of different operating frequencies within a predetermined pass band, said channels being provided with mixer means connected to said oscillator means; first filter means connected to said first demodulator for smoothing short-term variations of said deviation signal to provide a frequency-dependent error signal; second filter means connected to said second demodulator for smoothing short-term variations of said signal voltage, thereby producing a resulting voltage varying with said operating frequencies; validating means connected to said second filter means for detecting an extreme value of said resulting voltage; and output means connected to said first filter means and to said validating means for passing said error signal upon the occurrence of said extreme value. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14)
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Specification