Radio-frequency direction-finding arrangement

Claim 2

A scanning direction-finding system for reducing the effect of multipath reception on the accuracy of angular determinations, said system having means for developing at least first and second antenna patterns, through each of which, radio frequency energy emanating from a target is separately received, said first antenna pattern including a null along its axis of angular symmetry and said second antenna pattern having a maximum along its axis of angular symmetry, comprising: first means for displacing the effective symmetry axes of said patterns by a predetermined angle with respect to each other; second means for continuously and separately measuring the phase of energy received through each of said first and second patterns; third means for storing the phase value measured through one of said antenna patterns along with corresponding scan angle identifications whenever the amplitude of a selected one of said phase values crosses a predetermind threshold value; and fourth means for determining the target angle on the basis of equality of said phase value stored in said third means with the instantaneous phase measured through the other of said antenna patterns, said target angle being that corresponding to said stored phase value.

Claim 3

A direction-finding system according to claim 1 in which said antenna patterns are produced by two separate antennas mechanically offset to provide said symmetry axis displacement for determining said phase values.

Claim 4

A direction-finding system according to claim 1, in which said two radiation patterns are produced by a single antenna, the radiation patterns thereof being used successively for phase measurement, and said first means operates such that, each time said second pattern is used for phase measurement, the scanning angle is displaced by a predetermined angle from the value set for the phase measurement of the first received voltage.

Claim 5

In an rf direction-finding arrangement with scanned radiation patterns a first of which has a minimum along the symmetry axis, and a second of which has a maximum along the symmetry axis, particularly for elevation measurement by means of a radar set which includes means for continuously defining the scanning angle, means for reducing the effect of multipath interference, said antenna patterns having congruent symmetry axes and being produced by a single antenna, comprising: first means for generating an analog signal continuously representative of the angles of the symmetry axes of said patterns, said first means also including switching circuits for time sharing said patterns to produce an effective relative axis offset between said patterns; second means for continuously measuring the phases through said antenna patterns contemporaneously; a storage device in which the phase values of the first received voltage are stored together with the associated scanning angles of said first radiation pattern; third means for measuring the phase values of a second received voltage through said second antenna pattern, when said second received voltage falls below a predetermined value and for comparing with the phase values stored in said storage device; and fourth means for taking the target angle as that scanning angle whose associated phase value corresponds to the phase value determined in said comparison.

Claim 6

In an rf direction-finding arrangement with scanned radiation patterns a first of which has a minimum along the symmetry axis, and a second of which has a maximum along the symmetry axis, particularly for elevation measurement by means of a radar set which includes means for continuously defining the scanning angle, means for reducing the effect of multipath interference, said antenna patterns having congruent symmetry axes and being produced by a single antenna, comprising: first means for generating an analog signal continuously representative of the angles of the symmetry axes of said patterns, said first means also including switching circuits for time sharing said patterns to produce an effective relative axis offset between said patterns; second means for continuously measuring the phases through said antenna patterns contemporaneously; a storage device in which the phase values of the first received voltage are stored together with the associated scanning angles of said first radiation pattern; third means for measuring the phase values of a second received voltage through said second antenna pattern, when said second received voltage falls below a predetermined value and for comparing with the phase values stored in said storage device; and fourth means for taking the target angle as that scanning angle whose associated phase value corresponds to the phase value determined in said comparison.

Claim 7

A direction-finding arrangement according to claim 2 and including coherent phase detectors for the angle measurement of moving targets providing Doppler-frequency-dependent received voltages, including a third radiation pattern which is fixed and covers the scanning range of the two scanned radiation patterns for deriving an independent Doppler-frequency-dependent received voltage applied to generate a reference voltage for said phase detectors.

Claim 8

A direction-finding arrangement according to claim 5 including means for clutter rejection comprising low-pass filters following said phase detectors.

Claim 9

An rf direction-finding arrangement according to claim 6 in which said third antenna pattern is produced by an additional antenna which is substantially angularly stationary during the angle measurement.

Claim 10

A direction-finding arrangement according to claim 6 in which the first, second and third (C) radiation patterns are generated by a single antenna and including means whereby the three radiation patterns are switched on in succession such that each time the third radiation pattern is switched on, a constant scanning angle is set.

Claim 11

A direction-finding arrangement according to claim 1 including additional means for monitoring said angle measurement, said monitoring means being operated if, in the course of the scanning motion, within a predetermined angular range, the value Δφ, which begins when the second received voltage (UB) reaches a predetermined value UB o , the scanning-angle-dependent phase change d ψB/dφof said second received voltage reaches a predetermined value Y o , contemporaneously, said monitoring means indicating substantially error-free angle measurement under these circumstances.