Adaptive Processing of clutter rejection improvement for Transmit Antenna having arbitrary Profile (patent) Kaichiang Chang and Bill Kennedy 1/26/2007

Outline Background Problem statement How the invention solves the problem Why you believe that the invention is new Conclusion

Background For surveillance radar at high ground, the inverted Cosecant-squared antenna pattern is used to optimize SNR over the range of targets underneath the radar. Low sidelobes close to the radar site are essential to avoid receiver saturation or compression in a high ground clutter environment In azimuth plane, the beam is required to be broadened for coverage improvement.

Transmit Array Configuration with auxiliary antennas and dummy elements

Problem statement For a rectangular phased array without element failures, using the pattern synthesis for a linear array, element weightings are obtained to produce the Cosecant- squared antenna pattern with low sidelobes. In practice for a two dimensional phased array, an arbitrary profile of excited elements is produced due to irregular array building blocks and unexpected failed elements. As a result, the transmit Cosecant-squared antenna pattern has high sidelobes due to irregular array profiles to degrade effective clutter rejection operation.

Typical CSC pattern with low sidelobes for a linear array

Typical broaden beam pattern for a linear array

Partial transmit array configuration to account for element weighting factor

Transmit CSC pattern using traditional method shows high sidelobes

How the invention solves the problem A novel process is used to obtain array element weighting for a two dimensional phased array having arbitrary profile of excited elements. –Perform amplitude and phase pattern synthesis for a linear array –Use collapsed method to select excited elements in a two dimensional array –Based on the configuration of excited elements in the two dimensional array, new amplitude weightings in a linear array are obtained. –Based on these new amplitude weightings, phase-only pattern synthesis is performed for Cosecant-squared antenna pattern with low sidelobes. –Apply phase weighting to the two dimensional array.

Transmit CSC pattern using novel method shows low sidelobes

Transmit azimuth pattern using novel method maintains beam broadening.

Why you believe that the invention is new Prior art is the ASDE reflector antenna having inverted CSC pattern with high sidelobes using the extensive analysis. The inverted Cosecant-squared antenna pattern with -50 dB sidelobes is obtained for the first application for a two dimensional phased array having arbitrary profile due to irregular building blocks, failed elements and auxiliary antenna blockage.

Conclusion A novel process is used to obtain the inverted Cosecant-squared antenna pattern with -50 dB sidelobes for the first application for a two dimensional phased array having arbitrary profile due to irregular building blocks and auxiliary antenna blockage. This process can be used to perform array healing while elements fail for increasing array reliability.