US 5,706,012 A · Radar system method using virtual interferometry

Abstract

The virtual interferometer is an improved method for generating multiple ultaneous transmit beams as effected by a phased array radar. The technique is particularly suited to a solid state active radar array having a transmit/receive (T/R) module that is located at each radiating element. Potential applications to radar systems include environments such as air traffic control in which wide area surveillance with high search rates may be required. With multiple simultaneous beam generation coupled with parallel receiver beamformers and processors, such a radar system could support large volume searches while preserving the narrow beam characteristics by using the full aperture for generation of each of the multiple beams. The multiple simultaneous beams are generated by applying a particular phase shift at each radiating element, with no requirement for amplitude modulation. To form the multiple simultaneous beams on transmit, the antenna is logically divided into a series of equal segments, with a quadratic or near-quadratic phase profile applied to each of the logical antenna segments. The curvature of the phase function determines the angular extent covered by the series of beams being generated. This phase function has the effect of focusing the radiation at a specific distance either in front of or behind the phased array antenna, depending on the sign of the curvature. Each of the logical antenna segments interferes coherently with the others, resulting in a constructive/destructive interference pattern in the far-field of the antenna.

Claims14

Dependent claims

A method of selectively generating and simultaneously forming a plurality of at least two radar focused coherent transmit segment beams as well as simultaneously forming a receive beam as effected by radar phased array antenna means having both transmit and receive apertures that uses the technique of virtual interferometry during the transmit mode for any operative cycle thereof, the method comprising the steps of:

selecting a phase function of desired extent and curvature as represented by either a quadratic or nonquadratic nonlinear function for generating a coherent focused transmit segment beam,
dividing the transmit aperture of the antenna means into a plurality of at least two corresponding transmit subaperture segments with the extent of any transmit subaperture segment being identical to the extent of the selected phase function, and
simultaneously generating a plurality of at least two coherent focused transmit segment beams from the corresponding transmit subaperture segments after selection of any phase function and after dividing up the transmit aperture into at least two transmit subaperture segments during any operative cycle of the radar antenna means so as to effect simultaneous generation and projection of at least two coherent focused transmit segment beams from the corresponding transmit subaperture segments with each focused transmit segment beam having a near-field convergent portion adjacent its associated subaperture and also having a far-field divergent portion with a common focal point between these portions, so that each transmit subaperture segment generates an identical segment beam in the far field and adjacent overlapping portion of the transmit segment beams coherently interfere in the far field to form a multi-lobed transmit cluster beam.

A method of selectively generating and simultaneously forming more than two radar focused subaperture transmitted beams as well as simultaneously forming at least one receive beam as effected by radar phased array antenna means having both transmit and receive apertures that uses the technique of virtual interferometry during any transmit mode for any operative cycle thereof, the method comprising the steps of:

selecting a phase function of desired extent and curvature as represented by either a quadratic or nonquadratic nonlinear function for generating a focused transmitted subaperture beam during any transmit mode for any operative cycle of the radar phased array antenna means,
dividing the radar antenna means into more than two corresponding transmit subaperture segments with the extent of any transmit subaperture segment being identical to the extent of the selected phase function, and
simultaneously generating more than two coherent focused transmitted subaperture beams from the corresponding subaperture segments after selection of any phase function and after division of the transmit aperture into transmit subaperture segments corresponding to the number of transmitted segment beams during any transmit mode for any operative cycle of the radar antenna means so as to effect simultaneous generation and projection of more than two coherent focused transmitted segment beams from the corresponding transmit subapertures with each focused transmitted segment beam having a near-field convergent portion adjacent its associated transmit subaperture segment and a far-field divergent portion with a common focal point between these portions;
and with adjacent corresponding far-field portions of adjoining transmitted subaperture beams of more than two simultaneously generated transmitted subaperture beams during the transmit mode for any operative cycle of the radar antenna means having a constructive/destructive interference region so as to form a transmit cluster beam made up of multiple transmit lobes;
with the multiple lobes being made up of a series of main lobes and opposed series of side lobes of lesser gain with adjacent main lobes of the series being spaced and separated by sidelobes of reduced gain as compared to the series of main lobes, with this spacing between adjacent main lobes of the series contributes to reduction in side lobe gain upon formation of a two-way beam during any combined simultaneous transmit/receive mode for any operative cycle of the radar antenna means.

2 more elements

Dependencies are inferred from the claim text.

Radar system method using virtual interferometry

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Radar system method using virtual interferometry

Life of this patent

Abstract

Claims14