I don't understand this part. How can the electronic scanned radar know which exact direction the signal come from to reject signal from the null?.
If the radar can know which direction the signal comming from to reject then why don't all side lobes become null on PESA and AESA?.
You do this by 2 way. First is to use external antenna. to cover the necessary angular sector and then compare the incoming reflection or signal to where the mainlobe of the antenna is actually pointing. This way one would now the originating point of the jammer and therefore adjust the antenna pattern to put some nulls.
This is example of the sidelobe/mainlobe canceller. This one is in AN/APG63V3 or APG-82. Notice the small group of 3 horns below the main array. That is the sidelobe/mainlobe canceller antenna.
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Another example is in this EL/M-2052 antenna. Notice the 4 Vivaldi antenna at top of the array
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If anyone ever ask what is the differences between Sidelobe and Mainlobe canceller ? They are the same except the external antenna. Sidelobe canceller can have Low gain antenna as the sidelobe gain is weaker while the mainlobe canceller or notcher have higher gain antenna to cover for mainlobe's stronger gain.
Another way is to sacrifice or set some elements in Receive mode to "dedicate" them to sidelobe/mainlobe cancellation group. That is when one concerned about Size and weight + power requirement for the additional receiver antenna outside the main array.
This AN/APG-83 doesnt have dedicated sidelobe canceller.
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