US5349332A
Expired / Lapsed
US
⏱️ 0.0 years remaining
EAS system with requency hopping
Assignee: Sensormatic Electronics LLC
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Filing: 1992-10-13
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Granted: 1994-09-20
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Expires: 2012-10-13
Abstract
Abstract An EAS system in which a transmitter transmits an RF transmitter signal into an interrogation zone and a receiver receives RF signals from the interrogation zone. The received RF signals include any RF tag signals generated by tags situated in the zone and adapted to respond to the RF transmitter signal. In order to reduce interference effects, the RF carrier frequency of the transmitter signal is adapted to take on a plurality of different frequency values during different ones of a plurality of finite dwell time periods of the RF transmitter signal.
Inventors
- 👤 David B. Ferguson
- 👤 LeRoy A. Booker
- 👤 Craig R. Szklany
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 14:29
CPC Classifications
G; G08; G08B; G08B13/00; G08B13/22; G08B13/24; G08B13/2402; G08B13/2405; G08B13/2414; G08B13/2465; G08B13/2468; G08B13/2477; G08B13/248; G08B13/2488
Claims Analysis
Total Claims: 37
Claim 1
Independent Claim
148 words
An EAS system for use with a tag, said EAS system comprising: transmitting means for transmitting an RF transmitter signal into an interrogation zone, said RF transmitter signal having a RF carrier which is controlled by said transmitting means to have a plurality of different values each occurring over a different one of a plurality of finite dwell time periods of said RF transmitter signal, each finite dwell time period being spaced by a finite time interval from the preceding finite dwell time period; and receiving means adapted to be responsive to RF signals for making a determination and providing an indication that an RF tag signal has been received, said RF tag signal being produced by said tag in response to said RF transmitter signal and having a RF carrier frequency whose value is related to the value of the RF carrier of said RF transmitter signal.
Claim 2
Dependent Claim
148 words
An EAS system for use with a tag, said EAS system comprising: transmitting means for transmitting an RF transmitter signal into an interrogation zone, said RF transmitter signal having a RF carrier which is controlled by said transmitting means to have a plurality of different values each occurring over a different one of a plurality of finite dwell time periods of said RF transmitter signal, each finite dwell time period being spaced by a finite time interval from the preceding finite dwell time period; and receiving means adapted to be responsive to RF signals for making a determination and providing an indication that an RF tag signal has been received, said RF tag signal being produced by said tag in response to said RF transmitter signal and having a RF carrier frequency whose value is related to the value of the RF carrier of said RF transmitter signal.
Claim 3
Dependent Claim
32 words
An EAS system in accordance with claim 1 wherein: each finite dwell time period has an extent which is equal to the extent of each of the other finite dwell time periods.
Claim 4
Dependent Claim
30 words
An EAS system in accordance with claim 1 wherein: each finite dwell time period has an extent which is greater than the extent of the preceding finite dwell time period.
Claim 5
Dependent Claim
29 words
An EAS system in accordance with claim 1 wherein: each finite dwell time period has an extent which is less than the extent of the preceding dwell time period.
Claim 6
Dependent Claim
44 words
An EAS system in accordance with claim 1 wherein: said transmitter means determines as to whether the extent of a particular finite dwell time period is equal to, greater than or less than the preceding finite dwell time period one of fixedly and pseudorandomly.
Claim 7
Dependent Claim
47 words
An EAS system in accordance with claim 1 wherein: said RF transmitter signal is controlled to be at a reduced amplitude level during each of said finite time intervals relative to the amplitude level of said RF transmitter signal during each of said finite dwell time periods.
Claim 8
Dependent Claim
27 words
An EAS system in accordance with claim 6 wherein: said reduced amplitude level is at or less than the level allowed by governmental regulations for out-of-band signals.
Claim 9
Dependent Claim
59 words
An EAS system in accordance with claim 6 wherein: said plurality of different values of said RF carrier are within a predetermined RF frequency band; and said receiving means is responsive to signals within said RF frequency band and when said receiving means receives a signal during a finite time interval said receiving means identifies the presence of interference.
Claim 10
Dependent Claim
72 words
An EAS system in accordance with claim 1 wherein: said transmitter means controls said RF transmitter signal such that each of said plurality of different values of said RF carrier frequency of said RF transmitter signal is one of: selected to be greater than the preceding value in accordance with a predetermined fixed sequence; selected to be less than the preceding value in accordance with a predetermined fixed sequence; and selected pseudorandomly.
Claim 11
Dependent Claim
95 words
An EAS system in accordance with claim 1 wherein: said transmitter means further transmits an IF transmitter signal at an IF carrier frequency into said interrogation zone; said tag signal is related to said IF carrier frequency, said tag including first means for mixing said RF transmitter signal and said IF transmitter signal to develop said tag signal; and said receiving means includes second means for mixing any received RF signals with the RF carrier frequency of said RF transmitter signal to extract and "first" signal content in a band including said IF carrier frequency.
Claim 12
Dependent Claim
69 words
An EAS system in accordance with claim 10 wherein: said IF carrier frequency is modulated based upon a modulation frequency; said tag signal is related to said modulation frequency; and said receiving means includes: means for detecting in said "first" signal content and "second" signal content in a band including said modulation frequency; and means for comparing said detected "second" signal content with a signal at said modulation frequency.
Claim 13
Dependent Claim
42 words
An EAS system in accordance with claim 10 wherein: the RF carrier frequency of said RF transmitter signal is in the 902-928 MHz frequency range; and said IF carrier frequency of said IF transmitter signal is in the 40-150 kHz frequency range.
Claim 14
Dependent Claim
30 words
An EAS system in accordance with claim 10 wherein: said RF carrier frequency of said RF transmitter signal is in the microwave frequency range (i.e., greater than about 900 MHz).
Claim 15
Dependent Claim
20 words
An EAS system in accordance with claim 10 wherein: said RF carrier of said RF transmitter signal is frequency modulated.
Claim 16
Dependent Claim
42 words
An EAS system in accordance with claim 10 wherein: said transmitting means controls said IF carrier frequency to have a plurality of different values each occurring over a different one of a plurality further finite dwell periods of said IF transmitter signal.
Claim 17
Dependent Claim
69 words
An EAS system in accordance with claim 15 wherein: each further finite dwell period is spaced by a further finite time interval from the preceding further finite dwell period; and said IF transmitter signal is controlled to be at a reduced amplitude level during each of said further finite time intervals relative to the amplitude level of said IF transmitter signal during each of said further finite dwell periods.
Claim 18
Dependent Claim
29 words
An EAS system in accordance with claim 1 wherein: said RF carrier frequency of said RF transmitter signal is at a microwave frequency (i.e., greater than about 900 MHz).
Claim 19
Dependent Claim
12 words
An EAS system in accordance with claim 1 further comprising: said tag.
Claim 20
Independent Claim
143 words
A method of operating an EAS system for use with a tag, said method comprising: transmitting an RF transmitter signal into an interrogation zone, said RF transmitter signal having a RF carrier frequency which is controlled to have a plurality of different values each occurring over a different one of a plurality of finite dwell time periods of said RF transmitter signal, each finite dwell time period being spaced by a finite time interval from the preceding finite dwell time period; receiving RF signals; determining whether an RF tag signal is included in said received RF signals, said RF tag signal being produced by said tag in response to said RF transmitter signal and having an RF carrier frequency whose value is related to the value of the RF transmitter signal; and generating an indication that a RF tag signal has been received.
Claim 21
Independent Claim
143 words
A method of operating an EAS system for use with a tag, said method comprising: transmitting an RF transmitter signal into an interrogation zone, said RF transmitter signal having a RF carrier frequency which is controlled to have a plurality of different values each occurring over a different one of a plurality of finite dwell time periods of said RF transmitter signal, each finite dwell time period being spaced by a finite time interval from the preceding finite dwell time period; receiving RF signals; determining whether an RF tag signal is included in said received RF signals, said RF tag signal being produced by said tag in response to said RF transmitter signal and having an RF carrier frequency whose value is related to the value of the RF transmitter signal; and generating an indication that a RF tag signal has been received.
Claim 22
Dependent Claim
31 words
A method in accordance with claim 19 wherein: each finite dwell time period has an extent which is equal to the extent of each of the other finite dwell time periods.
Claim 23
Dependent Claim
29 words
A method in accordance with claim 19 wherein: each finite dwell time period has an extent which is greater than the extent of the preceding finite dwell time period.
Claim 24
Dependent Claim
28 words
A method in accordance with claim 19 wherein: each finite dwell time period has an extent which is less than the extent of the preceding dwell time period.
Claim 25
Dependent Claim
43 words
A method in accordance with claim 19 wherein: the determination as to whether the extent of a particular finite dwell time period is equal to, greater than or less than the preceding finite dwell time period is made one of fixedly and pseudorandomly.
Claim 26
Dependent Claim
44 words
An EAS system in accordance with claim 19 wherein: said RF transmitter signal is at a reduced amplitude level during each of said finite time intervals relative to the amplitude level of said RF transmitter signal during each of said finite dwell time periods.
Claim 27
Dependent Claim
26 words
A method in accordance with claim 24 wherein: said reduced amplitude level is at or less than the level allowed by governmental regulations for out-of-band signals.
Claim 28
Dependent Claim
55 words
A method in accordance with claim 19 wherein: said plurality of different values of said RF carrier frequency are within a predetermined RF frequency band; and said method further includes identifying the presence of interference in said system when RF signals within said RF frequency band are received during one of said finite time intervals.
Claim 29
Dependent Claim
61 words
A method in accordance with claim 19 wherein: each of said plurality of different values of said RF carrier frequency of said RF transmitter signal is one of: selected to be greater than the preceding value in accordance with a predetermined fixed sequence; selected to be less than the preceding value in accordance with a predetermined fixed sequence; and selected pseudorandomly.
Claim 30
Dependent Claim
84 words
A method in accordance with claim 19 further comprising: transmitting an IF transmitter signal at an IF carrier frequency into said interrogation zone; said tag signal being related to said IF carrier frequency, said tag producing said tag signal by mixing said RF transmitter signal and said IF transmitter signal; and said step of receiving includes mixing any received RF signals with the RF carrier frequency of said RF transmitter signal to extract first signal content in a band including said IF carrier frequency.
Claim 31
Dependent Claim
66 words
A method in accordance with claim 28 wherein: said IF carrier frequency is modulated based upon a modulation frequency; said tag signal is related to said modulation frequency; and said step of receiving further includes: detecting from said "first" signal content and "second" signal content in a band including said modulation frequency; and comparing said detected "second" signal content with a signal at said modulation frequency.
Claim 32
Dependent Claim
39 words
A method in accordance with claim 28 wherein: the RF carrier frequency of said RF transmitter signal is in the MHz frequency range; and said IF carrier frequency of said IF transmitter signal is in the kHz frequency range.
Claim 33
Dependent Claim
22 words
A method in accordance with claim 28 wherein: said RF carrier of said RF transmitter signal is in the microwave frequency range.
Claim 34
Dependent Claim
20 words
A method in accordance with claim 28 wherein: said RF carrier frequency of said RF transmitter signal is frequency modulated.
Claim 35
Dependent Claim
36 words
A method in accordance with claim 28 wherein: said IF carrier frequency has a plurality of different values each occurring over a different one of a plurality further finite dwell periods of said IF transmitter signal.
Claim 36
Dependent Claim
65 words
A method in accordance with claim 33 wherein: each further finite dwell period is spaced by a further finite time interval from the preceding further finite dwell period; and said IF transmitter signal is at a reduced amplitude level during each of said further finite time intervals relative to the amplitude level of said IF transmitter signal during each of said further finite dwell periods.
Claim 37
Dependent Claim
22 words
A method in accordance with claim 19 wherein: said RF carrier frequency of said RF transmitter signal is at a microwave frequency.
References Cited (Backward Citations)
US4063229A
Cited
US3868669A
Cited
US4212002A
Cited
US4139844A
Cited
US4352098A
Cited
US4356477A
Cited
US4429302A
Cited
US4642640A
Cited
US4736207A
Cited
US5109217A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1997-09-19 | 1998-03-21 | 1998-09-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2001-09-19 | 2002-03-21 | 2002-09-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2005-09-19 | 2006-03-21 | 2006-09-20 | $7700.00 | Window Closed / Lapsed |