Telecommunications – Receiver or analog modulated signal frequency converter – Signal selection based on frequency
Patent
1994-03-29
1995-06-27
Eisenzopf, Reinhard J.
Telecommunications
Receiver or analog modulated signal frequency converter
Signal selection based on frequency
4551613, 4551651, H04B 116
Patent
active
054288266
ABSTRACT:
An automatic tuning system in a high-speed scanning radio receiver provided with (a) a noise squelch circuit, first and second detecting circuits, first and second control circuits, a CPU circuit providing PLL data, and a scanning stop function. The squelch circuit generates a first (SP) signal when a decreasing trend in a noise detection voltage becomes lower than a preset reference voltage. The first detecting circuit judges whether or not the SP signal is generated within first predetermined time period (M1). The first control circuit causes the second detecting circuit to detect whether or not the SC signal is generated within a second predetermined time period (M2; M2>M1) when the first detecting circuit detects the SP signal has been generated, and the second control circuit causes the second detecting circuit to detect whether or not the SC signal is generated within a third predetermined time period (M3; M3>M1) when the first detecting circuit detects the SP signal for the current channel being scanned has not been generated and the SP signal for the preceeding scanning was generated. Accordingly, even if no SP signal for the current channel being scanned has been detected, the system is capable of securely detecting the SC signal by extending a SC signal monitoring period to the period M3, and thus securely stopping searching whenever the SC signal is generated.
REFERENCES:
patent: 4580285 (1986-04-01), Richards, Jr.
patent: 5125105 (1992-06-01), Kennedy et al.
patent: 5161253 (1992-11-01), Hirano
patent: 5199109 (1993-03-01), Baker
patent: 5212817 (1993-05-01), Atkinson
Eisenzopf Reinhard J.
Uniden Corporation
Vo Nguyen
LandOfFree
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