EP0812069A2
Expired / Lapsed
EP
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Dual-mode cellular telephone system
Assignee: Sharp Corp
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Filing: 1997-06-04
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Granted: —
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Expires: 2017-06-04
Abstract
Abstract The present invention is directed to provide a dual-mode cellular telephone system which is capable of suppressing a narrow-band disturbing signal appearing in a mobile station of a dual-mode cellular telephone system adapted to an analog system and digital CDMA system. A CDMA signal from a CDMA base station and a narrow-band signal from an analog system are received through an antenna (101) by receiver (102) whereby they are amplified, subjected to frequency conversion and, then, input to a variable notch filter (105). A disturbing signal detection circuit (106) supplies the variable notch filter (105) with a control signal for making its frequency be variable. Namely, the disturbing signal detection circuit (106) detects a case that an output level of the variable notch filter (105) becomes minimal by changing the notch frequency by sweeping control signals. A control signal at which the output level of the variable notch filter (105) is minimal is fed to the variable notch filter (105).
Inventors
- 👤 Masamori Tokuda
- 👤 Masao Miyazaki
- 👤 Takeshi Okamoto
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-04 22:22
CPC Classifications
H; H04; H04B; H04B1/00; H04B1/69; H04B1/707; H04B1/7097; H04B1/71; H04B1/06; H04B1/10; H04B1/1027; H04B1/1036; H04B1/7101; H04B1/7102; H04B2001/1063
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
59 words
A dual-mode cellular telephone system adapted to an analog system and a digital CDMA system, characterized in that a mobile station receiver is provided with a narrow-band disturbing signal suppression circuit having a notch filter (105, 108) for suppressing a disturbing signal resulted from intermodulation distortion produced by a plurality of transmission channel signals from an analog base station.
Claim 2
Dependent Claim
63 words
A dual-mode cellular telephone system adapted to an analog system and a digital CDMA system, characterized in that a mobile station receiver is provided with a narrow-band disturbing signal suppression circuit with a notch filter (105, 108) for suppressing a disturbing signal resulted from intermodulation distortion produced inside the receiver when receiving a plurality of transmission channel signals from an analog base station.
Claim 3
Dependent Claim
28 words
A dual-mode cellular telephone system as defined in claim 1 or 2, characterized in that the notch filter (105, 108) has at least one previously determined notch frequency.
Claim 4
Dependent Claim
63 words
A dual-mode cellular telephone system as defined in claim 3, characterized in that the mobile station is provided with a receiver (102) and a level detecting circuit (109) that monitors an output level of the receiver (102) and, only in the case of the output level exceeding a previously determined reference level, controls the notch filter (108) to possess a specified notch characteristic.
Claim 5
Dependent Claim
42 words
A dual-mode cellular telephone system as defined in claim 1 or 2, characterized in that a notch frequency of the notch filter (105, 108) is variable and is controlled to be the same as a presumable frequency of a narrow-band disturbing signal.
Claim 6
Dependent Claim
71 words
A dual-mode cellular telephone system as defined in claim 1 or 2, characterized in that the notch filter (105) has a variable notch frequency under control and is provided with a disturbing signal detecting circuit (106) for detecting a specified value of the variable notch frequency, at which the notch filter (105) has a minimal output, and supplying the notch filter (105) with a control signal corresponding to the detected frequency.
Claim 7
Dependent Claim
87 words
A dual-mode cellular telephone system as defined in claim 1 or 2, characterized in that the notch filter (105) has a plurality of notch frequencies under control being variable at a time and is provided with the disturbing signal detecting circuit (106) for detecting a combination of the plurality of notch frequencies under control, at which the notch filter (105) has a minimal output, and supplying the notch filter (105) with a control signal corresponding to the detected combination of the plurality of notch frequencies under control.
Claim 8
Dependent Claim
52 words
A dual-mode cellular telephone system as defined in claim 7, characterized in that the notch filter (105) has two notch frequencies being variable at a time, one of which is variable within a lower sub-band of a desired band and the other is variable within a higher sub-band of the desired band.
Claim 9
Dependent Claim
58 words
A dual-mode cellular telephone system as defined in claim 7 or 8, characterized in that a combination of the plurality of notch frequencies under control is determined, then several of the notch frequencies are fixed and the other notch frequencies are continuously changed while detecting a change in an output level of the notch filter (105) during communications.
Claim 10
Dependent Claim
58 words
A dual-mode cellular telephone system as defined in any one of claims 6 to 9, characterized in that the disturbing signal detecting circuit (106) monitors an output level of the notch filter (105) and, only in the case of the output level exceeding a predetermined reference level, controls the notch filter (105) to have a specified notch characteristic.
Claim 11
Dependent Claim
64 words
A dual-mode cellular telephone system as defined in claim 1 or 2, characterized in that the notch filter (105) has a variable notch frequency under control and is provided with a frequency detecting circuit (107) for analyzing a frequency component exerting a narrow-band disturbance on a CDMA-band signal and supplying the notch filter (105) with a control signal corresponding to the detected frequency component.
Claim 12
Dependent Claim
21 words
A dual-mode cellular telephone system as defined in claim 11, characterized in that the frequency detecting circuit (107) performs Fourier transformation.
Claim 13
Dependent Claim
55 words
A dual-mode cellular telephone system as defined in claim 11 or 12, characterized in that the frequency detecting circuit (107) monitors a received signal level of the mobile station and, only in the case of the received signal level exceeding a predetermined reference level, controls the notch filter (105) to have a specified notch characteristic.
Claim 14
Dependent Claim
60 words
A mobile station receiver operable for digital CDMA communication in a cellular telephone system, said receiver being provided with a narrow-band disturbing signal suppression circuit including a notch filter (105, 108) for suppressing a narrow band disturbing signal which results from intermodulation distortion produced by a plurality of analogue transmission channel signals and which lies within the CDMA frequency bandwidth.
References Cited (Backward Citations)
No citation records indexed.
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