Patent EP0124332A2 successfully refreshed from Google Patents.
EP0124332A2
Expired / Lapsed
EP
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A double conversion tuner
Assignee: RCA Corp
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Filing: 1984-04-19
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Granted: —
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Expires: 2004-04-19
Abstract
Abstract A double conversion tuner stabilized against drift includes a first local oscillator (7) included in a phase locked loop (PLL) and a second local oscillator (13) included in an automatic fine tuning (AFT) loop (15, 21, 43, 13, 11). A switching arrangement (43, 47) selectively allows the AFT signal to control the second local oscillator (13) only when the operation of the PLL has been completed and if the picture carrier of the IF signal produced at the output of the tuner is within the AFT control range to prevent the second local socillator (13) from being tuned incorrectly.
Inventors
- 👤 David John Carlson
- 👤 Juri Tults
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-28 23:12
CPC Classifications
H; H03; H03J; H03J7/00; H03J7/02; H03J7/04; H03J7/06; H03D; H03D7/00; H03D7/16; H03D7/161; H03J5/00; H03J7/065
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
340 words
Apparatus for tuning a receiver to various RF signals corresponding to respective channels, each RF signal having at least one information bearing carrier, comprising: RF input means (1) for providing one of said RF signals; first local oscillator means (7) for generating a first local oscillator signal having a frequency controlled in response to the amplitude of a first control signal applied to a first control input; channel selection means (37,39) for selecting one of said channels; first local oscillator control means (19,35) coupled to said channel selection means for generating said first control signal in accordance with the selected channel; first mixer means (5) for mixing said RF signal and said first local oscillator signal to produce a first IF signal; second local oscillator means (13) for generating a second local oscillator signal having a frequency controlled in response to the amplitude of a second control signal applied to a second control input; second mixer means (11) for mixing said first IF signal and said second local oscillator signal to produce a second IF signal, said second IF signal having at least one information bearing carrier corresponding to the information bearing carrier of said RF signal, said information bearing carrier of said IF signal having a nominal value corresponding to the correct tuning condition of said receiver; and automatic fine tuning (AFT) means (21,21a) for generating an AFT signal having an amplitude representing the deviation, if any, of the frequency of said information bearing carrier of said second IF signal from said nominal value; characterized by completion indicating means (45) coupled to said first oscillator control means for generating a completion signal indicating when said first control signal is substantially stabilized after a new channel has been selected; and AFT coupling control means for coupling (43,43a,55) said AFT signal to said control input of said second local oscillator means so that said AFT signal is selectively allowed to control the frequency of said second local oscillator signal as said second control signal after the generation of said completion signal.
Claim 2
Dependent Claim
340 words
Apparatus for tuning a receiver to various RF signals corresponding to respective channels, each RF signal having at least one information bearing carrier, comprising: RF input means (1) for providing one of said RF signals; first local oscillator means (7) for generating a first local oscillator signal having a frequency controlled in response to the amplitude of a first control signal applied to a first control input; channel selection means (37,39) for selecting one of said channels; first local oscillator control means (19,35) coupled to said channel selection means for generating said first control signal in accordance with the selected channel; first mixer means (5) for mixing said RF signal and said first local oscillator signal to produce a first IF signal; second local oscillator means (13) for generating a second local oscillator signal having a frequency controlled in response to the amplitude of a second control signal applied to a second control input; second mixer means (11) for mixing said first IF signal and said second local oscillator signal to produce a second IF signal, said second IF signal having at least one information bearing carrier corresponding to the information bearing carrier of said RF signal, said information bearing carrier of said IF signal having a nominal value corresponding to the correct tuning condition of said receiver; and automatic fine tuning (AFT) means (21,21a) for generating an AFT signal having an amplitude representing the deviation, if any, of the frequency of said information bearing carrier of said second IF signal from said nominal value; characterized by completion indicating means (45) coupled to said first oscillator control means for generating a completion signal indicating when said first control signal is substantially stabilized after a new channel has been selected; and AFT coupling control means for coupling (43,43a,55) said AFT signal to said control input of said second local oscillator means so that said AFT signal is selectively allowed to control the frequency of said second local oscillator signal as said second control signal after the generation of said completion signal.
Claim 3
Dependent Claim
50 words
Apparatus as recited in Claim 1 characterized in that: said first local oscillator control means (19,35) includes a closed loop control means (23,25,27,33) for controlling the amplitude of said first control signal to establish a predetermined relationship between the frequency of said first local oscillator signal and a reference value.
Claim 4
Dependent Claim
24 words
Apparatus as recited in Claim 2 characterized in that: said closed loop control system continuously controls the frequency of said first local oscillator signal.
Claim 5
Dependent Claim
83 words
Apparatus as recited in Claim 2 or 3 characterized in that: said AFT coupling control means includes offset detector means (47) for generating an offset signal indicating that the frequency of said carrier of said second IF signal is not within a predetermined range of said nominal value after the generation of said completion signal; and said closed loop control means changes said predetermined relationship between the frequency of said first local oscillator and said reference value in response to said offset signal.
Claim 6
Dependent Claim
39 words
Apparatus as recited in Claim 4 characterized in that: said AFT coupling control means (43,43a) includes initialization means for setting the amplitude of said second control signal to a predetermined amplitude level until the generation of said completion signal.
Claim 7
Dependent Claim
39 words
Apparatus as recited in Claim 4 or 5 characterized in that: said AFT coupling control means is responsive to the absence of said offset signal for allowing said AFT to control the frequency of said second local oscillator signal.
Claim 8
Dependent Claim
89 words
Apparatus as recited in Claim 6 characterized in that: said offset detector means (47) includes ramp signal generating means (51) for selectively coupling a ramp signal to said second control input as said second control signal in response to the generation of said completion signal; and amplitude comparator means (57) responsive to the amplitude of said AFT signal means for generating said offset signal if the amplitude of said AFT is not brought within a predetermined amplitude range while said ramp signal is coupled to said second control input.
Claim 9
Dependent Claim
70 words
Apparatus as recited in Claim 5 characterized in that: said AFT coupling control means (43,43a,55) is responsive to said completion signal for allowing said AFT signal to control the frequency of said second local oscillator signal immediately after the generation of said completion signal and is responsive to the generation of said offset signal thereafter for disabling said AFT signal from controlling the frequency of said second local oscillator signal.
Claim 10
Dependent Claim
71 words
Apparatus as recited in Claim 8 characterized in that: said information bearing carrier of said IF signal is a picture carrier modulated with a video signal including a synchronization signal component; and said offset detector means (247) includes sync comparison means (249) responsive to said synchronization signal component for generating said offset if said synchronization signal component is not correct at a predetermined time after the generation of said completion signal.
Claim 11
Dependent Claim
60 words
Apparatus as recited in Claim 9 characterized in that: said initialization means (in 21a) couples a DC signal substantially equal to the amplitude of said AFT signal which represents substantially no deviation between the frequency of said picture carrier and said nominal value to said second control input as said second control signal until the generation of said completion signal.
Claim 12
Dependent Claim
114 words
Apparatus as recited in Claim 9 characterized in that: said AFT means (21a) provides two complementary AFT signals referenced to the same reference level at respective outputs, said reference level being substantially equal to the amplitude of each of said complementary AFT signals which represents substantially no deviation between the frequency of said information bearing carrier and said nominal value, one of said outputs being connected to said second control input; and said initialization means (in 21a) includes switch means (43a) for coupling said outputs of said AFT means together until the generation of said completion signal and decoupling said outputs of said AFT means from one another when said completion signal is generated.
Claim 13
Dependent Claim
105 words
12 . Apparatus as recited in Claim 4 characterized in that: said closed loop means (23,25,27,33) is a phase locked loop means for controlling the amplitude of said first control signal to establish the frequency of said first local oscillator signal in a proportional relationship to a reference frequency by a programmable proportion factor, said phase locked loop means including proportional factor control means (25) coupled to said channel selection means (37,39) for setting said programmable proportion factor in accordance with said selected channel and coupled to said offset detector means (4 7 ) for changing said proportion factor in response to said offset signal.
Claim 14
Dependent Claim
42 words
Apparatus as recited in Claim 12 characterized in that: said completion indicating means includes lock detector means (45) coupled to said phase locked loop means for generating said completion signal when said proportional relationship is established after said proportion factor is changed.
References Cited (Backward Citations)
No citation records indexed.
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