Range measurement method and apparatus having scanning interferometers and range signal processor
First Claim
1. An apparatus for determining the range of a source of electromagnetic emission from a monitoring location, comprising:
- movable platform means;
first and second interferometer means mounted on said platform at a spacing d along a base line and having parallel receiving axes for receiving such source of emission;
means for moving said platform means so that said receiving axes scan at an angular rate ω
s relative to such source of emission and thereby produce interferometer signals having a relative time difference t21 ;
angle of arrival means for sensing and producing a signal representing an angle of arrival φ
of the source of emission relative to the base line of said first and second interferometer means;
time difference signal processing means for producing a signal t21 representing a rate of change of said time difference t21 ; and
range signal processing means coupled to receive signals representing the angle of arrival φ and
the rate of time difference change t21 to produce an output signal of range R as a function thereof in accordance with the relationship ##EQU11##
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Accused Products
Abstract
An array of antenna elements is arranged along a common, rotating platform so as to form a pair of mechanically scanned interferometers exhibiting spaced, parallel receiving axes for ranging on a distance emitter. As the receiving lobes of the pair of interferometers scan across the emitter, lobe modulated signals are received having a relative time difference t21 that varies as a sinusoidal function of time due to the platform'"'"'s rotation and includes a dc error value due to slight but unavoidable nonparallelism of the interferometer beams. The rate of change of t21 is derived to produce a signal t21 which drops the dc error component of t21, and which is applied as an input to a rate dependent range signal processor producing an output signal of range R as a function of the relationship ##EQU1## In this relationship d is the separation of the interferometer centers along the base line, and φ is the varying angle of arrival of the emitter relative to the rotating base line of the antenna array. In a preferred embodiment, the individual antenna elements that form the pair of interferometers, are mounted and servo controlled on the rotating platform so as to maintain tracking alignment of the principal antenna beams on an emitter of interest, independently of the rotating platform so as to optimize received signal strength.
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Citations
11 Claims
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1. An apparatus for determining the range of a source of electromagnetic emission from a monitoring location, comprising:
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movable platform means; first and second interferometer means mounted on said platform at a spacing d along a base line and having parallel receiving axes for receiving such source of emission; means for moving said platform means so that said receiving axes scan at an angular rate ω
s relative to such source of emission and thereby produce interferometer signals having a relative time difference t21 ;angle of arrival means for sensing and producing a signal representing an angle of arrival φ
of the source of emission relative to the base line of said first and second interferometer means;time difference signal processing means for producing a signal t21 representing a rate of change of said time difference t21 ; and range signal processing means coupled to receive signals representing the angle of arrival φ and
the rate of time difference change t21 to produce an output signal of range R as a function thereof in accordance with the relationship ##EQU11## - View Dependent Claims (2, 3, 4, 5)
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6. The apparatus for determining the range of a source of electromagnetic emission from a monitoring location, comprising:
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movable platform means; first and second interferometer means mounted on said platform at a spacing d along a base line and having parallel receiving axes for receiving such source of emission; means for moving said platform means so that said receiving axes scan at an angular rate ω
s relative to such source of emission and thereby produce interferometer signals having a relative time difference t21 ;angle of arrival detection means for sensing and producing a signal representing an angle of arrival φ
of the source of emission relative to the base line of said first and second interferometer means; andrange signal processing means responsive to said interferometer signals having said relative time difference t21 and including means for producing a signal t21, representing the rate of change of said relative time difference t21, and further being responsive to said signal representing an angle of arrival φ
to produce an output signal of range R as a function of said rate of change signal t21 of said relative time difference t21 between said interferometer signals. - View Dependent Claims (7, 8, 9, 10)
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11. A method of ranging on a nonscanning emitter in which error in the resulting range signal output attributed to nonparallelism of receiving axes of scanning antennas is substantially eliminated, comprising the steps of:
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rotating on a common, rigid platform, first and second interferometers mounted at a spacing d along a base line on said platform so that the interferometers exhibit substantially parallel receiving axes scanning across a source of electromagnetic emission at an angular scan rate ω
s so as to produce interferometer output signals representing the source of emission modulated by the scanning interferometers and having a relative time difference t21 ;measuring an angle of arrival φ
of the source of emission with respect to the base line of said first and second interferometer means;processing the output signals from the interferometers to produce a signal representing the time rate of change of said time difference t21 ; and processing signals representing said angle of arrival φ and
said signal t21 representing said rate of change of said time difference t21 so as to produce an output signal of range R as a function thereof in accordance with the relationship of ##EQU12##
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Specification