Patent WO-2018162756-A1 (WO)
Inventor: GIANCRISTOFARO DOMENICO
IPC: G01S13/76
Filed: 2018-03-09
Abstract: The present invention concerns a localization method for locating a target that is coupled with a locator transponder (5) associated with a permanent identification code permanently assigned to said locator transponder (5); the localization method comprising: upon reception of a user request for locating the target, transmitting, by a paging system (3,200) or by a radar-based system (4,300,500), a spread spectrum paging signal carrying the permanent identification code and a temporary identification code temporarily assigned to the locator transponder (5), wherein said temporary identification code is shorter than said permanent identification code; receiving, by the locator transponder (5), the spread spectrum paging signal and extracting, by said locator transponder (5), the temporary identification code carried by said spread spectrum paging signal received; transmitting, by the radar-based system (4,300,500), radar signals towards one or more areas of earth' s surface or sky, and receiving, by said radar-based system (4,300,500), echo signals from said one or more areas of the earth' s surface or sky; upon reception by the locator transponder (5) of one or more radar signals transmitted by the radar- based system (4,300,500), generating and transmitting, by said locator transponder (5), a sequence of watermarked radar echo signals in which a spread spectrum watermarking signal is embedded, wherein said spread spectrum watermarking signal carries the temporary identification code extracted. In particular, generating and transmitting, by the locator transponder (5), the sequence of watermarked radar echo signals includes: generating a sequence of radar echo signals on the basis of the radar signal (s) received; modulating the generated sequence of radar echo signals on the basis of the spread spectrum watermarking signal, thereby obtaining the sequence of watermarked radar echo signals; and transmitting said sequence of watermarked radar echo signals. The spread spectrum watermarking signal includes a synchronization portion and an information portion; wherein the synchronization portion of the spread spectrum watermarking signal is generated on the basis of a first predefined pseudo noise code; wherein the information portion of the spread spectrum watermarking signal is generated by applying a first predefined spread spectrum technique to a given signal carrying the temporary identification code extracted; wherein said first predefined spread spectrum technique is applied by using a second predefined pseudo noise code, that is the same as, or different than, the first predefined pseudo noise code. Moreover, the localization method further comprises carrying out, by the radar-based system (4,300,500), localization operations that include: detecting, in the received echo signals, the sequence of watermarked radar echo signals transmitted by the locator transponder (5) by detecting the synchronization portion of the spread spectrum watermarking signal embedded in said sequence of watermarked radar echo signals; extracting the temporary identification code carried by the spread spectrum watermarking signal embedded in the sequence of watermarked radar echo signals detected, by extracting said temporary identification code from the information portion of the spread spectrum watermarking signal embedded in said sequence of watermarked radar echo signals detected; and determining a location of the locator transponder (5) on the basis of the sequence of watermarked radar echo signals detected.