# US 7,411,548 B2 · Reference beacon identification using transmission sequence characteristics

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- Number: US 7,411,548 B2
- Document ID: US7411548B2
- Status: Granted
- Kind: B2
- Application number: 11/279,419
- Filed: 2006-04-12
- Published: 2007-11-08
- Granted: 2008-08-12
- Earliest claimed: 2006-04-12
- Assignees: The Boeing Company
- Inventors: Layne D. Lommen
- Web page: https://patentgrep.com/patent/US7411548B2

## CPC

- G01S 5/06: Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements (G01S5/12 takes precedence)
- G01S 5/021: {Calibration, monitoring or correction (G01S5/0252 takes precedence)}
- 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

A method and apparatus for encoding information in a reference beacon signal for use in a time-difference-of-arrival/frequency-difference-of-arrival (TDOA/FDOA) geolocation system. Information is encoded in the reference beacon signal using variations in the times and frequencies of sequential reference signal transmissions. The encoded information may include an identifier associated with the transmitter of the reference beacon signal. A geolocation system receiving the reference beacon signal can thus differentiate it from non-cooperative target emissions as well as from other reference beacon signals.

## Claims

### Claim 1

A method of transmitting transmitter identification information, compnsing:
sequentially transmitting a plurality of signal segments, each signal segment being characterized by a frequency parameter and a time parameter, wherein at least one of the frequency and the time parameters of each signal segment is determined in accordance with the transmitter identification information,
wherein a difference in the frequency parameters of adjacent signal segments is indicative of a portion of the transmitter identification information,
wherein the time parameter of each signal segment includes a start time of the signal segment, and
wherein the start time of a signal segment relative to the other signal segments is indicative of a position of the signal segment within the plurality of signal segments.

### Claim 2 (depends on 1)

The method of claim 1, wherein the portion of the transmitter identification information is a bit, the bit having a first binary value if the difference in frequency parameters has a first differential frequency value and the bit having a second binary value if the difference in frequency parameters has a second differential frequency value.

### Claim 3 (depends on 1)

The method of claim 1, wherein the start times of the sequentially transmitted signal segments follow a predetermined progression.

### Claim 4 (depends on 3)

The method of claim 3, wherein the predetermined progression is in accordance with the following expressions:
D=D0+D1*N/2 for N=even, and
D=D0−D1*(N+1)/2 for N=odd,
where D is the time interval between the start of the Nth and (N+1)th signal segments, and D0 and D1 are predetermined parameters, with D1=f*D0, wherein 0<f<1.

### Claim 5 (depends on 1)

The method of claim 1, wherein the portion of the transmitter identification information is a bit, the bit having a first binary value if the frequency parameters follow a first predetermined progression and the bit having second binary value if the frequency parameters follow a second predetermined progression.

### Claim 6 (depends on 1)

The method of claim 1, wherein each of the plurality of signal segments includes a pseudo-random waveform.

### Claim 7 (depends on 1)

The method of claim 1, comprising:
receiving at least a portion of the plurality of signal segments; and
extracting the transmitter identification information from the received signal segments.

### Claim 8

A method of transmitting transmitter identification information, comprising:
sequentially transmitting a plurality of signal segments, each signal segment being characterized by a frequency parameter and a time parameter, wherein at least one of the frequency and the time parameters of each signal segment is determined in accordance with the transmitter identification information,
wherein the time parameter of each signal segment is indicative of a portion of the transmitter identification information,
wherein the frequency parameter of each signal segment includes a frequency of the signal segment, and
wherein the frequency of a signal segment is indicative of a position of the signal segment within the plurality of signal segments.

### Claim 9 (depends on 8)

The method of claim 8, wherein the portion of the transmitter identification information is a bit, the bit having a first binary value if the time parameter has a first value and the bit having a second binary value if the time parameter has a second value.

### Claim 10 (depends on 8)

The method of claim 8, wherein the frequencies of the sequentially transmitted signal segments follow a predetermined progression.

### Claim 11

An apparatus for transmitting transmitter identification information, comprising:
means for sequentially transmitting a plurality of signal segments, each signal segment being characterized by a frequency parameter and a time parameter, wherein at least one of the frequency and the time parameters of each signal segment is determined in accordance with the transmitter identification information,
wherein a difference in the frequency parameters of adjacent signal segments is indicative of a portion of the reference beacon identifier, wherein the time parameter of each signal segment includes a start time of the signal segment, and
wherein the start time of a signal segment relative to the other signal segments is indicative of a position of the signal segment within the plurality of signal segments.

### Claim 12 (depends on 11)

The apparatus of claim 11, wherein the portion of the transmitter identification information is a bit, the bit having a first binary value if the difference in frequency parameters has a first differential frequency value and the bit having a second binary value if the difference in frequency parameters has a second differential frequency value.

### Claim 13 (depends on 11)

The apparatus of claim 11, wherein the start times of the sequentially transmitted signal segments follow a predetermined progression.

### Claim 14 (depends on 13)

The apparatus of claim 13, wherein the predetermined progression is in accordance with the following expressions:
D=D0+D1*N/2 for N=even, and
D=D0−D1*(N+1)/2 for N=odd,
where D is the time interval between the start of the Nth and (N+1)th signal segments, and D0 and D1 are predetermined parameters, with D1=f*D0, wherein 0<f<1.

### Claim 15 (depends on 11)

The apparatus of claim 11, wherein the portion of the transmitter identification information is a bit, the bit having a first binary value if the frequency parameters follow a first predetermined progression and the bit having second binary value if the frequency parameters follow a second predetermined progression.

### Claim 16 (depends on 11)

The apparatus of claim 11, wherein each of the plurality of signal segments includes a pseudo-random waveform.

### Claim 17 (depends on 11)

The apparatus of claim 11, comprising:
means for receiving at least a portion of the plurality of signal segments; and means for extracting the transmitter identification information from the received signal segments.

### Claim 18

An apparatus for transmitting transmitter identification information, compnsing:
means for sequentially transmitting a plurality of signal segments, each signal segment being characterized by a frequency parameter and a time parameter, wherein at least one of the frequency and the time parameters of each signal segment is determined in accordance with the transmitter identification information,
wherein the time parameter of each signal segment is indicative of a portion of the transmitter identification information,
wherein the frequency parameter of each signal segment includes a frequency of the signal segment, and
wherein the frequency of a signal segment is indicative of a position of the signal segment within the plurality of signal segments.

### Claim 19 (depends on 18)

The apparatus of claim 18, wherein the portion of the transmitter identification information is a bit, the bit having a first binary value if the time parameter has a first value and the bit having a second binary value if the time parameter has a second value.

### Claim 20 (depends on 18)

The apparatus of claim 18, wherein the frequencies of the sequentially transmitted signal segments follow a predetermined progression.