Process and apparatus for finding stealthcraft

A process for distinguishing radar or sonar background returns from target returns, and comprising:

• (a) coding the transmitted signals for permitting recognition of the transmission sequence of said transmitted signals,
• (b) temporarily storing replicas of at least the sequence-recognizable portions of said transmitted signals,
• (c) comparing at least the sequence-recognizable portions of said background returns and said target returns with said temporarily stored replicas of said sequence-recognizable portions of said transmitted signals, and
• (d) distinguishing said background returns from said target returns on the basis of the sequence of said returns.

A process for detecting both stealth-modified and conventional targets from the background returns from radar or sonar beams, and comprising:

• (a) producing a first narrow beam with sequentially coded signals that produce background returns,
• (b) steering said first narrow beam for scanning a target area,
• (c) distinguishing said background returns of said first narrow beam from returns from the targets by comparing a sequence of said sequentially coded signals to a sequence of said returns,
• (d) constructing background images from said background returns, and
• (e) identifying as targets the dark patches in said background images that result when said first steerable narrow beam is at least one of absorbed, reflected and refracted by said targets.

A process for detecting stealth-modified and/or conventional targets from background returns, and comprising:

• (a) scanning a target area by transmitting a first coded narrow beam that produces background returns,
• (b) scanning said target area by transmitting a second coded narrow beam that produces background returns, said second coded beam scanning at least a part of said first coded narrow beam, said second coded narrow beam producing returns distinguishably different from those from said first coded narrow beam,
• (c) receiving the returns from said first and said second coded narrow beams, and
• (d) comparing the codes of suitably delayed replicas of said first and said second coded narrow beams with their returns to find missing background return pairs corresponding to points of intersection of said first and said second narrow coded beams.