# US 8,542,145 B2 · Locating system based on noisy type waveforms

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 8,542,145 B2
- Document ID: US8542145B2
- Status: Granted
- Kind: B2
- Application number: 12/737,664
- Filed: 2009-08-06
- Published: 2011-06-02
- Granted: 2013-09-24
- Earliest claimed: 2008-08-07
- Assignees: Universita' Degli Studi Di Roma "Tor Vergata"
- Applicants: Gaspare Galati
- Inventors: Gaspare Galati
- Web page: https://patentgrep.com/patent/US8542145B2

## CPC

- G01S 13/003: {Bistatic radar systems; Multistatic radar systems}
- G01S 13/0209: {Systems with very large relative bandwidth, i.e. larger than 10 %, e.g. baseband, pulse, carrier-free, ultrawideband}
- G01S 13/878: {Combination of several spaced transmitters or receivers of known location for determining the position of a transponder or a reflector (G01S13/874 takes precedence)}
- G01S 7/38: Jamming means, e.g. producing false echoes
- G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES

## Abstract

The present invention relates to a system for locating non-cooperating objects by means of a random or pseudo-random noisy type waveform generator, an amplifier, of said waveforms and an antenna which radiates them towards the object, which object generates an electromagnetic echo which is detected by a passive subsystem of antennas and receivers. The time delay and Doppler shift values are determined in the latter subsystem and in turn forwarded from encoding and modulating blocks to a central processor which estimates the position and the speed of the object. The passive subsystem receives, through a transmission channel or storage element, the reference signal which represents the transmitted noisy type waveform and uses it for calculating the bi-dimensional cross correlation (ambiguity function), which permits to estimate the time delay and the Doppler shift.

## Claims

### Claim 1

A process for locating moving or temporarily steady objects (A), by means of an integrated multistatic system comprising: a controlled generator able to emit a broadband, noisy type waveform (B); so as to illuminate said objects; a passive subsystem (4), comprising a plurality of antennas (7-i) distributed in an operating environment and a respective plurality of receivers (8-i), each receiver (8-i) being connected to a respective antenna (7-i), said passive subsystem (4) being able to receive an electromagnetic echo signal (C) produced by each object (A) illuminated by said waveform; processing means (5) able to process first data supplied by said receivers (8-i) so as to locate each object (A) by extracting second data (D) related to position and/or speed of said object (A), wherein the receivers (8-i) of the passive subsystem (4) are able to perform measurements of said first data, comprising time delay and Doppler shift measurements, by calculating a bi-dimensional cross correlation function between the electromagnetic echo signal (C) produced by each object (A) and a reference signal (E) consisting of a replica of the waveform (B) transmitted onto the object itself by means of the generator, said method comprising the following steps: emitting a noisy type waveform (B) by means of said broadband controlled generator, so as to illuminate said objects; receiving an electromagnetic echo signal (C), produced by each object (A) invested by said waveform, by said passive subsystem (4); locating each object (A) by extracting second data (D), related to position and/or speed of said object (A), obtained by processing the first data transmitted by said receivers (8-i), using processing means (5), said first data comprising time delay and/or Doppler shift measurements obtained by calculating a bi-dimensional cross correlation function between the electromagnetic echo signal (C) produced by each object (A) and a reference signal (E) consisting of a replica of the waveform (B) transmitted onto the object itself by means of the generator, wherein the reference signal (E) is transmitted by the controlled generator able to emit a broadband, noisy type waveform (B) to the passive subsystem (4) by means of a transmission channel and a reference signal (E) is read from a storage device (12) of the synthesizer (1), said synthesizer being directly connected to said passive system (4) and wherein said waveform (B) is of pseudo-random type, not predictable by an external observer, synthesized by the synthesizer (1) so as to have a lower spectrum occupancy than that capable of creating interference in predetermined frequency bands to be protected and an (average power)/(peak power) ratio sufficiently large enough to allow a good transmission efficiency, wherein the synthesis of said waveform (B), which is recorded on said storage device (12), includes the following steps
a) generating a waveform in the frequency domain by means of a generator of samples of Gaussian pseudo-random variables, which samples form the spectrum samples of the waveform,
b) filtering said waveform so as to attenuate undesired frequency components by applying a frequency-domain weighting function,
c) transforming the filtered waveform from the frequency domain to the time-domain,
d) limiting the amplitude of said time-domain waveform in by comparing, sample by sample, its amplitude with a predetermined threshold value,
e) analyzing the spectrum of the amplitude-limited, filtered waveform and verifying the absence of significant interferences in frequency ranges of other users, and
f) recording the amplitude-limited, filtered waveform on the storage device (12) if the result of said spectrum analysis is satisfactory with regards to the absence of said interferences, otherwise repeating steps from b) to f).