Active mills cross arrangement systems and methods
Techniques are disclosed for systems and methods to provide high resolution interpolation of arrival direction of echo return signals using an active mills cross arrangement, such as in sonar or other ranging sensor systems. A system may include an active mills cross arrangement with high resolution interpolation of echo returns in two planes. The active mills cross arrangement may include a transmitter configured to emit one or more signals, a first line array including a first plurality of elements defining a first plane, and a second line array including a second plurality of elements defining a second plane orthogonal to the first plane. At least one of the first line array and the second line array may be configured to receive echo returns of the emitted signals from one or more objects or targets.
1 . A system comprising:
an active mills cross arrangement with interpolation of echo returns in two planes, the active mills cross arrangement comprising:
a transmitter configured to emit one or more signals forming one or more transmit beams;
a first line array comprising a first plurality of elements defining a first plane;
a second line array comprising a second plurality of elements defining a second plane orthogonal to the first plane; and
a third line array comprising a third plurality of elements, wherein the third line array extends parallel to the second line array, and wherein the third line array is spaced away from the second line array along the first line array;
wherein the second line array and the third line array are configured to receive echo returns of the emitted signals from one or more objects or targets, and the system is configured to form one or more receive beams based on the echo returns;
wherein the first line array defines the transmitter, the transmitter defined as a transmitter array which is a phased array;
wherein the second line array defines a first receiver array for receiving echo returns of the signals emitted from the transmitter; and
wherein the third line array defines a second receiver array for receiving echo returns of the signals emitted from the transmitter;
wherein the system is configured to provide a result of a multiplicative combination of the transmit and receive beams in a configuration reducing the echo returns to only those that occur within an intersection of the transmit and receive beams, the system being configured to determine a direction of arrival of the echo returns from the multiplicative combination.
2 . The system of claim 1 , further comprising a logic device configured to control the first line array, the second line array, and the third line array, wherein a spacing between the second line array and the third line array is proportional to a resolution of an interpolation of the received echo returns.
3 . The system of claim 1 , further comprising a logic device, wherein each of the first line array, the second line array, and the third line array is configured to communicate with the logic device, wherein the logic device applies an interpolation algorithm to the received echo returns to interpolate the direction of arrival of the echo returns in both the first plane and the second plane.
4 . The system of claim 3 , wherein the interpolation algorithm comprises half beam processing.
5 . The system of claim 3 , wherein the interpolation algorithm comprises estimation of signal parameters via rotational invariant techniques (ESPRIT).
6 . The system of claim 3 , wherein the interpolation algorithm comprises a MUSIC interpolation technique.
7 . The system of claim 3 , wherein the logic device is configured to:
weight the echo returns symmetrically across a center channel of a plurality of receiver channels according to a weighting scheme to produce a signal pattern;
perform one or more sidelobe calculations to calculate sidelobe levels of the signal pattern;
reject sidelobe levels greater than a stored best sidelobe level to produce a post process signal; and
analyze the post process signal.
8 . The system of claim 7 , wherein:
the plurality of receiver channels comprise at least part of at least one of the first, second, or third line arrays; and
in the at least part of the at least one of the first, second, or third arrays, at least one channel has a weight of zero, and at least two channels on opposite sides of the at least one channel in the at least one of the first, second, and third line arrays have non-zero weights.
9 . The system of claim 7 , wherein the logic device is configured to perform a first pass of the one or more sidelobe calculations at a first resolution at a first step angle, and wherein the logic device is configured to perform a second pass of the one or more sidelobe calculations at a second resolution higher than the first resolution at a second step angle.
10 . The system of claim 7 , wherein the logic device is configured to:
weight the received one or more signals according to a plurality of weighting schemes; and
sort the plurality of weighting schemes according to their respective sidelobe levels, and wherein the transmitter comprises a sonar transducer configured to emit sonar signals.
11 . A method comprising:
emitting, by a transmitter controlled by a logic device, one or more signals along a first plane, the transmitter being a phased array, the one or more signals forming one or more transmit beams;
receiving, by a first line array in communication with the logic device, echo returns of the emitted signals along a second plane;
receiving, by a second line array in communication with the logic device, echo returns of the emitted signals along a third plane parallel to the second plane;
forming one or more receive beams based on the echo returns of the emitted signals along the second and third planes; and
interpolating, by the logic device in a plurality of planes, a direction of arrival algorithm to the received echo returns;
wherein the method comprises providing a result of a multiplicative combination of the transmit and receive beams in a configuration reducing the echo returns to only those that occur within an intersection of the transmit and receive beams;
wherein the method comprises determining a direction of arrival of the echo returns from the multiplicative combination.
12 . The method of claim 11 , wherein the interpolating comprises one or more of the following interpolation techniques: estimation of signal parameters via rotational invariant techniques (ESPRIT), MUSIC, or half-beam processing.
13 . The method of claim 11 , wherein the second and third planes are spaced away from each other along the first plane.
14 . The method of claim 11 , wherein emitting the one or more signals comprises emitting the one or more signals by the phased array arranged along the first plane.
15 . The method of claim 11 , further comprising:
weighting the received echo returns symmetrically across a center channel of a plurality of receiver channels according to a weighting scheme to produce a signal pattern;
calculating sidelobe levels of the signal pattern;
rejecting sidelobe levels greater than a stored best sidelobe level to produce a post process signal; and
analyzing the post process signal.
16 . The method of claim 15 , further comprising:
setting a channel level of a center section of the plurality of receiver channels to 1; and
limiting channel levels of one or more channels adjacent to the center section to within +/−1.
17 . The method of claim 15 , further comprising:
performing a first pass of the sidelobe level calculations at a first resolution at a first step angle; and
performing a second pass of the sidelobe level calculations at a second resolution higher than the first resolution at a second step angle.
18 . The method of claim 15 , further comprising:
weighting the received echo returns according to a plurality of weighting schemes;
sorting the plurality of weighting schemes according to their respective sidelobe levels; and
adjusting one or more mid-level channels of the plurality of receiver channels to find a lowest sidelobe level.
19 . The method of claim 15 , further comprising using an angular resolution based on a uniform beam width to reduce the number of angular calculations for a wide beam.