US6868073B1
Expired / Lapsed
US
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Distance/ranging by determination of RF phase delta
Assignee: Battelle Memorial Institute Inc
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Filing: 2000-06-06
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Granted: 2005-03-15
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Expires: 2020-06-06
Abstract
Abstract A method and system can locate an RF transponder based on phase differences between signals transmitted to the RF transponder. The method transmits from a first transponder to a second transponder first and second signals at first and second frequencies, respectively. The second signal is compared with the first signal and a distance between the first and second transponders is determined based on the phase difference between the first and second signals. In one embodiment, the first transponder is an interrogator, the second transponder is an RF tag, and the RF tag determines the phase difference between the two signals. In another embodiment, the first and second transponders are the interrogator and RF tag, respectively, but the interrogator determines the phase difference between the two signals after the two signal are reflected back to the interrogator. The method can also determine a position (distance and direction) of the RF tag by measuring the distances from two different locations of the interrogator to the RF tag. In one embodiment, the two distances are measured from two spaced-apart antennas of the interrogator. In another embodiment, the interrogator is moved from one known location to another known location. With distance measurements from both known locations, the location of the RF tag can be determined by simple geometry.
Inventors
- 👤 Curtis Lee Carrender
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 11:04
CPC Classifications
G; G01; G01S; G01S13/00; G01S13/74; G01S13/82; G01S13/84; G01S5/00; G01S5/02; G01S5/14
Claims Analysis
Total Claims: 29
Claim 1
Independent Claim
108 words
A method of radio frequency communication, the method comprising: transmitting a first signal at a first frequency from a first transponder to a second transponder; phase locking on the first signal to create a reference signal; transmitting a second signal at a second frequency from the first transponder to the second transponder; comparing the second signal to the reference signal, comprising mixing the reference signal with the second signal to obtain a mixed signal; and determining a distance between the first and second transponders based on a phase difference between the second and reference signals, comprising determining how many nulls or peaks there are in the mixed signal.
Claim 2
Independent Claim
108 words
A method of radio frequency communication, the method comprising: transmitting a first signal at a first frequency from a first transponder to a second transponder; phase locking on the first signal to create a reference signal; transmitting a second signal at a second frequency from the first transponder to the second transponder; comparing the second signal to the reference signal, comprising mixing the reference signal with the second signal to obtain a mixed signal; and determining a distance between the first and second transponders based on a phase difference between the second and reference signals, comprising determining how many nulls or peaks there are in the mixed signal.
Claim 3
Dependent Claim
20 words
The method of claim 1 wherein the first transponder is an interrogator and the second transponder is an RF tag.
Claim 4
Dependent Claim
43 words
The method of claim 2 , further comprising receiving a radio frequency interrogation signal from the interrogator; modulating the interrogation signal according to an information code to produce a response signal; and transmitting the response signal from the RF tag to the interrogator.
Claim 5
Dependent Claim
73 words
The method of claim 1 wherein: the step of transmitting the second signal includes transmitting a plurality of frequency portions each at a different frequency; the comparing step includes comparing each of the frequency portions to the reference signal by mixing each of the frequency portions with the reference signal to produce a plurality of mixed signals; and the distance determining step includes counting nulls or peaks in each of the mixed signals.
Claim 6
Dependent Claim
74 words
The method of claim 1 wherein the step of determining how many nulls or peaks there are in the mixed signal is performed at the second transponder and the step of determining the distance between the first and second transponders includes transmitting to the first transponder an indication of the how many nulls or peaks there are in the mixed signal and determining the distance from the indication and the first and second frequencies.
Claim 7
Dependent Claim
103 words
The method of claim 1 wherein the distance determined is a first distance and the first and second signals are transmitted via a first antenna of the first transponder, the first transponder having a second antenna spaced apart from the first antenna, the method further comprising: determining a second distance between the second antenna of the first transponder and the second transponder based on a phase difference between the signals transmitted through the second antenna; and determining a direction from the first transponder to the second transponder based on the first and second distances and a distance between the first and second antennas.
Claim 8
Dependent Claim
137 words
The method of claim 1 wherein the reference signal is a first reference signal and the first and second signals are transmitted via a first antenna of the first transponder, the method further comprising: transmitting a third signal at the first frequency from a second antenna of the first transponder to the second transponder; phase locking on the third signal to create a second reference signal; transmitting a fourth signal at the second frequency from the second antenna of the first transponder to the second transponder; comparing the fourth signal to the second reference signal; determining a distance between the second antenna of the first transponder and the second transponder based on a phase difference between the fourth signal and the second reference signal; and determining a location of the second transponder based on the distances determined.
Claim 9
Dependent Claim
26 words
The method of claim 1 wherein the second signal is a frequency modulated signal that includes a plurality of frequency portions at a plurality of frequencies.
Claim 10
Independent Claim
109 words
A method of radio frequency communication, the method comprising: transmitting a first signal at a first frequency from a first transponder to a second transponder; transmitting a second signal at a second frequency from the first transponder to the second transponder; comparing the second signal to the first signal, and phase locking on the first signal to create a reference signal and mixing the reference signal with the second signal to obtain a mixed signal; and determining a distance between the first and second transponders based on a phase difference between the first and second signals, comprising determining how many nulls or peaks there are in the mixed signal.
Claim 11
Independent Claim
109 words
A method of radio frequency communication, the method comprising: transmitting a first signal at a first frequency from a first transponder to a second transponder; transmitting a second signal at a second frequency from the first transponder to the second transponder; comparing the second signal to the first signal, and phase locking on the first signal to create a reference signal and mixing the reference signal with the second signal to obtain a mixed signal; and determining a distance between the first and second transponders based on a phase difference between the first and second signals, comprising determining how many nulls or peaks there are in the mixed signal.
Claim 12
Dependent Claim
26 words
The method of claim 9 wherein the second signal is a frequency modulated signal that includes a plurality of frequency portions at a plurality of frequencies.
Claim 13
Dependent Claim
20 words
The method of claim 10 wherein the first transponder is an interrogator and the second transponder is an RF tag.
Claim 14
Dependent Claim
43 words
The method of claim 11 , further comprising: receiving a radio frequency interrogation signal from the interrogator; modulating the interrogation signal according to an information code to produce a response signal; and transmitting the response signal from the RF tag to the interrogator.
Claim 15
Dependent Claim
73 words
The method of claim 9 wherein: the step of transmitting the second signal includes transmitting a plurality of frequency portions each at a different frequency; the comparing step includes comparing each of the frequency portions to the reference signal by mixing each of the frequency portions with the reference signal to produce a plurality of mixed signals; and the distance determining step includes counting nulls or peaks in each of the mixed signals.
Claim 16
Dependent Claim
74 words
The method of claim 10 wherein the step of determining how many nulls or peaks there are in the mixed signal is performed at the second transponder and the step of determining the distance between the first and second transponders includes transmitting to the first transponder an indication of the how many nulls or peaks there are in the mixed signal and determining the distance from the indication and the first and second frequencies.
Claim 17
Dependent Claim
103 words
The method of claim 10 wherein the distance determined is a first distance and the first and second signals are transmitted via a first antenna of the first transponder, the first transponder having a second antenna spaced apart from the first antenna, the method further comprising: determining a second distance between the second antenna of the first transponder and the second transponder based on a phase difference between the signals transmitted through the second antenna; and determining a direction from the first transponder to the second transponder based on the first and second distances and a distance between the first and second antennas.
Claim 18
Dependent Claim
34 words
The method of claim 10 wherein the first and second signals are reflected back to the first transponder by the second transponder and the comparing and determining steps are performed by the first transponder.
Claim 19
Dependent Claim
122 words
The method of claim 10 wherein the distance determined is a first distance, the method further comprising: moving the first transponder from a first position, from which the first distance is determined, to a second position; transmitting a third signal at the first frequency from the first transponder to the second transponder; transmitting a fourth signal at the second frequency from the first transponder to the second transponder; comparing the fourth signal to the third signal; determining a second distance between the first and second transponders based on a phase difference between the third and fourth signals; and determining a location of the second transponder based on the first and second distances and the first and second positions of the first transponder.
Claim 20
Dependent Claim
139 words
A radio frequency transponder, comprising: an antenna that receives from an interrogator first and second signals having first and second frequencies, respectively; a phase lock loop coupled to the antenna and structured to phase lock on the first signal to create a reference signal; a comparator coupled to the antenna and phase lock loop and structured to compare the second signal to the reference signal, the comparator comprising a mixer structured to mix the reference signal with the second signal to obtain a mixed signal; and means for determining a phase difference between the second and reference signals, the phase difference corresponding to a distance between the first and second transponders, the means for determining comprising a counter coupled to the mixer and structured to determine a null count of how many nulls there are in the mixed signal.
Claim 21
Dependent Claim
139 words
A radio frequency transponder, comprising: an antenna that receives from an interrogator first and second signals having first and second frequencies, respectively; a phase lock loop coupled to the antenna and structured to phase lock on the first signal to create a reference signal; a comparator coupled to the antenna and phase lock loop and structured to compare the second signal to the reference signal, the comparator comprising a mixer structured to mix the reference signal with the second signal to obtain a mixed signal; and means for determining a phase difference between the second and reference signals, the phase difference corresponding to a distance between the first and second transponders, the means for determining comprising a counter coupled to the mixer and structured to determine a null count of how many nulls there are in the mixed signal.
Claim 22
Dependent Claim
141 words
A radio frequency interrogator, comprising: a variable frequency signal source that produces a first signal at a first frequency and a second signal at a second frequency; antenna means coupled to the signal source for transmitting to a transponder the first and second signals and for receiving the first and second signals reflected back from the transponder; a comparator coupled to the antenna and structured to compare the reflected second signal to the reflected first signal, the comparator comprising a mixer that mixes the second signal with the reflected first signal to produce a mixed signal; and means for determining a distance between the first and second transponders based on a phase difference between the reflected first signal and the second signal, the means for determining comprising a null or peak counter that counts nulls or peaks in the mixed signal.
Claim 23
Dependent Claim
141 words
A radio frequency interrogator, comprising: a variable frequency signal source that produces a first signal at a first frequency and a second signal at a second frequency; antenna means coupled to the signal source for transmitting to a transponder the first and second signals and for receiving the first and second signals reflected back from the transponder; a comparator coupled to the antenna and structured to compare the reflected second signal to the reflected first signal, the comparator comprising a mixer that mixes the second signal with the reflected first signal to produce a mixed signal; and means for determining a distance between the first and second transponders based on a phase difference between the reflected first signal and the second signal, the means for determining comprising a null or peak counter that counts nulls or peaks in the mixed signal.
Claim 24
Dependent Claim
234 words
A radio frequency communication system, comprising: an interrogator that transmits a radio frequency interrogation signal and receives a response signal; and a transponder that receives the interrogation signal and transmits the response signal to the interrogator, the transponder including: a memory that stores an information code; a modulator coupled to the memory and structured to produce the response signal by modulating the interrogation signal according to the information code wherein a first one of the transponder and interrogator includes a variable frequency source that transmits to a second one of the transponder and interrogator a first signal at a first frequency followed by a second signal at a second frequency; one of the transponder and interrogator includes a phase comparison circuit that detects phase shifts in the second signal relative to the first signal; and one of the transponder and interrogator includes a distance determiner that determines the transponder and the interrogator based on the phase shifts; and the phase comparison circuit comprising a phase lock loop that phase locks on the first signal to produce a reference signal; and a mixer coupled to the phase lock loop and structured to mix the reference signal with the second signal to obtain a mixed signal and a counter coupled to the mixer and structured to determine one of a null and peak count of how many nulls or peaks there are in the mixed signal.
Claim 25
Dependent Claim
234 words
A radio frequency communication system, comprising: an interrogator that transmits a radio frequency interrogation signal and receives a response signal; and a transponder that receives the interrogation signal and transmits the response signal to the interrogator, the transponder including: a memory that stores an information code; a modulator coupled to the memory and structured to produce the response signal by modulating the interrogation signal according to the information code wherein a first one of the transponder and interrogator includes a variable frequency source that transmits to a second one of the transponder and interrogator a first signal at a first frequency followed by a second signal at a second frequency; one of the transponder and interrogator includes a phase comparison circuit that detects phase shifts in the second signal relative to the first signal; and one of the transponder and interrogator includes a distance determiner that determines the transponder and the interrogator based on the phase shifts; and the phase comparison circuit comprising a phase lock loop that phase locks on the first signal to produce a reference signal; and a mixer coupled to the phase lock loop and structured to mix the reference signal with the second signal to obtain a mixed signal and a counter coupled to the mixer and structured to determine one of a null and peak count of how many nulls or peaks there are in the mixed signal.
Claim 26
Dependent Claim
22 words
The communication system of claim 20 wherein the interrogator includes the variable frequency source and the transponder includes the phase comparison circuit.
Claim 27
Dependent Claim
15 words
The communication system of claim 20 wherein the second signal is a frequency modulated signal.
Claim 28
Dependent Claim
37 words
The communication system of claim 20 wherein the interrogator includes means for calculating the distance between the interrogator and the transponder based on the null or peak count which is sent to the interrogator by the transponder.
Claim 29
Dependent Claim
19 words
The communication system of claim 20 wherein the interrogator includes the variable frequency source and the phase comparison circuit.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2008-03-14 | 2008-09-13 | 2009-03-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2012-03-14 | 2012-09-13 | 2013-03-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2016-03-14 | 2016-09-13 | 2017-03-15 | $7700.00 | Window Closed / Lapsed |