Moving target radar
First Claim
1. The method of suppressing clutter in the operation of a moving-target radar, said clutter being produced by an object which moves backward and forward about a fixed position, the received signal of said radar being converted into quadrature signals, herein called an I signal and a Q signal, the said method comprising, converting the I signal into quadrature signals, herein called I3 and I4 signals, I3 lagging I4 by 90°
- , converting the Q signal into quadrature signals, herein called Q3 and Q4, Q3 lagging Q4 by 90°
, deriving at least one of the products I3Q4 or I4Q3 and producing responsive to said product an indication of the target and the direction of movement of the target while suppressing the clutter.
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Accused Products
Abstract
There is disclosed a direction-sensitive doppler radar particularly for detecting intruders into a protected area which is free of the mechanically controlled parts of the prior art. To distinguish between an intruder and the clutter produced by the movement back and forth of trees or like growth in a wind, the doppler side bands of the clutter produced by the growth moving or swaying in opposite directions are processed so that they counteract each other. The incoming signals, both clutter and from intruders, are converted into I and Q quadrature signals, frequency or sensitivity compensated and passed through a variable bandwidth bandpass filter whose bandwidth is reduced at the low-frequency end as the clutter increases. The I and Q signals are then each converted into quadrature I3 and I4 and Q3 and Q4 signals respectively, and the products I3Q4 and I4Q3 derived and subtracted. The resulting signal produces the alarm if there is an intruder and indicates the direction of movement of the intruder.
There is also disclosed a variable-bandwidth filter whose bandpass is set by time modulation of resistance of the filter. There is also disclosed a multiplier including a balanced network. One of the parameters to be multiplied is impressed as an actuating potential on the network and the other to unbalance the network for an interval dependent on the magnitude of the latter parameter.
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Citations
12 Claims
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1. The method of suppressing clutter in the operation of a moving-target radar, said clutter being produced by an object which moves backward and forward about a fixed position, the received signal of said radar being converted into quadrature signals, herein called an I signal and a Q signal, the said method comprising, converting the I signal into quadrature signals, herein called I3 and I4 signals, I3 lagging I4 by 90°
- , converting the Q signal into quadrature signals, herein called Q3 and Q4, Q3 lagging Q4 by 90°
, deriving at least one of the products I3Q4 or I4Q3 and producing responsive to said product an indication of the target and the direction of movement of the target while suppressing the clutter. - View Dependent Claims (9)
- , converting the Q signal into quadrature signals, herein called Q3 and Q4, Q3 lagging Q4 by 90°
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2. Moving-target radar apparatus for detecting a target moving in a region in which clutter is at the same time produced by an object in said region moving backward and forward about a fixed position, the said apparatus comprising means for transmitting a beam of high-frequency energy into said region, said beam producing a resulting reflected beam by reflection from said target and object, means for receiving said reflected beam and deriving therefrom a signal of doppler frequency corresponding to the movement of said object and clutter, first converting means connected to said receiving means for converting said signal and clutter into substantially quadrature signals, herein called an I signal and a Q signal, second converting means connected to said first converting means for converting said I signal into substantially quadrature signals, herein called I3 and I4 signals, I3 lagging I4 by about 90°
- , third converting means connected to said first converting means for converting said Q signal into substantially quadrature signals, herein called Q3 and Q4 signals, Q3 lagging Q4 by about 90°
, multiplying means connected to said second and third converting means for deriving from said last-named means at least one product signal I3Q4 or I4Q3, and means connected to said multiplying means for indicating the movement of said object and its direction of movement. - View Dependent Claims (3, 4, 5, 6, 7, 8, 10, 11, 12)
- , third converting means connected to said first converting means for converting said Q signal into substantially quadrature signals, herein called Q3 and Q4 signals, Q3 lagging Q4 by about 90°
Specification