AESA-based synthetic nulling for enhanced radar ground clutter suppression
A radar system uses multiple nulls to improve detection capabilities. Multiple radar pulses are transmitted and or received, each with a different null pattern. The returns from each pulse are averaged together to form a null window that is less noisy and potentially wider than a single null pattern. This approach can improve the signal-to-noise ratio and make it easier to detect objects of interest. The system may generate individual pulses from an AESA divided into several subarrays. Each subarray produces a pulse with a null in a different location in the radiation pattern centered about a location of interest. The contemporaneous return signals are averaged together.
1 . A computer apparatus comprising:
an electronically scanned array (ESA); and
at least one processor in data communication with a memory storing processor executable code for configuring the at least one processor to:
determine, for a desired null window corresponding to a source of interference, a plurality of signals each defining a null narrower than the desired null window and offset in location relative to the desired null window;
apply each of the plurality of signals to the ESA sequentially over multiple pulses and/or contemporaneously across subarrays of the ESA;
receive one or more return signals corresponding to each of the plurality of signals; and
coherently combine the return signals to synthesize a composite null window spanning the desired null window.
2 . The computer apparatus of claim 1 , wherein the at least one processor is further configured to filter each of the one or more return signals before producing the composite null window.
3 . The computer apparatus of claim 1 , wherein:
applying each of the plurality of signals to the ESA comprises applying each of the plurality of signals separately and sequentially over a plurality of pulses; and
producing the composite null window comprises:
receiving two or more return signals; and
combining the two or more return signals.
4 . The computer apparatus of claim 3 , wherein combining the two or more return signals comprises averaging the two or more return signals.
5 . The computer apparatus of claim 3 , wherein combining the two or more return signals comprises weighted averaging the two or more return signals based on a known location of the desired null window.
6 . The computer apparatus of claim 1 , wherein:
applying each of the plurality of signals to the ESA comprises:
electronically dividing the ESA into two or more subarrays; and
applying each of the plurality of signals separately to one of the subarrays.
7 . The computer apparatus of claim 1 , wherein the at least one processor comprises a field programmable gate array.
8 . A method comprising:
determining, for a desired null window corresponding to a source of interference, a plurality of signals to apply to an electronically scanned array (ESA), each defining a null narrower than the desired null window and offset in location relative to the desired null window;
applying each of the plurality of signals to an ESA sequentially over multiple pulses and/or contemporaneously across subarrays of the ESA;
receiving one or more return signals corresponding to each of the plurality of signals; and
coherently combining the return signals to synthesize a composite null window spanning the desired null window.
9 . The method of claim 8 , further comprising filtering each of the one or more return signals before producing the composite null window.
10 . The method of claim 8 , wherein:
applying each of the plurality of signals to the ESA comprises applying each of the plurality of signals separately and sequentially over a plurality of pulses; and
producing the composite null window comprises:
receiving two or more return signals; and
combining the two or more return signals.
11 . The method of claim 10 , wherein combining the two or more return signals comprises direct complex addition of the two or more return signals.
12 . The method of claim 10 , wherein combining the two or more return signals comprises weighted averaging the two or more return signals based on a known location of the desired null window.
13 . The method of claim 8 , wherein:
applying each of the plurality of signals to the ESA comprises:
electronically dividing the ESA into two or more subarrays; and
applying each of the plurality of signals separately to one of the subarrays.
14 . A radar system comprising:
an electronically scanned array (ESA); and
at least one processor in data communication with a memory storing processor executable code for configuring the at least one processor to:
determine, for a desired null window corresponding to a source of interference, a plurality of signals each defining a null narrower than the desired null window and offset in location relative to the desired null window;
apply each of the plurality of signals to the ESA sequentially over multiple pulses and/or contemporaneously across subarrays of the ESA;
receive one or more return signals corresponding to each of the plurality of signals; and
coherently combine the return signals to synthesize a composite null window spanning the desired null window.
15 . The radar system of claim 14 , wherein the at least one processor is further configured to filter each of the one or more return signals before producing the composite null window.
16 . The radar system of claim 14 , wherein:
applying each of the plurality of signals to the ESA comprises applying each of the plurality of signals separately and sequentially over a plurality of pulses; and
producing the composite null window comprises:
receiving two or more return signals; and
combining the two or more return signals.
17 . The radar system of claim 14 , wherein the radiation patterns and nulls are applied to both Tx and Rx.
18 . The radar system of claim 14 , wherein the radiation patterns and nulls are applied to one of Tx or Rx.
19 . The radar system of claim 14 , wherein:
applying each of the plurality of signals to the ESA comprises:
electronically dividing the ESA into two or more subarrays; and
applying each of the plurality of signals separately to one of the subarrays.
20 . The radar system of claim 14 , wherein the at least one processor comprises a field programmable gate array.