US3857997A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Cable converter with phase lock loop techniques
Assignee: OCI Communcations Inc
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Filing: 1973-03-08
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Granted: 1974-12-31
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Expires: 1993-03-08
Abstract
Abstract A cable television converter is used with a cable system that transmits a pilot signal, which is harmonically related to the desired converter IF signal, along with the video and sound frequency carriers for each TV channel. The converter includes phase locked loop means connected to the converter input for producing an output signal locked to the carrier frequency of the particular selected channel. The converter also includes pilot signal conversion means which produces as an output signal the difference between the IF frequency and the output signal of the phase locked loop means. A mixer combines the output signal from the pilot signal conversion means with the modulated carrier frequency to provide the desired converter IF signal.
Inventors
- 👤 P Toonder
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 21:26
CPC Classifications
H; H04; H04N; H04N7/00; H04N7/16
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
174 words
In a cable television converter having channel selection means associated with a system that transmits a pilot signal which is harmonically related to the desired IF signal along with the video and sound frequency carrier received at the input of said converter for each TV channel, phase locked loop means (PLLM) connected at the input of said converter for producing an output signal locked to the carrier frequency for the selected channel, pilot signal conversion means (PSCM) having two inputs, the first of said inputs being connected to the input of said converter, the second of said inputs being connected to the output signal of said PLLM, said PSCM producing an output signal which is the difference between the IF frequency and the output signal of said PLLM, and combining means having two inputs, the first of said inputs being connected to the modulated carrier frequency, the second of said inputs being connected to the output signal of said PSCM, said combining means processing said input signals to produce a constant IF output signal.
Claim 2
Dependent Claim
174 words
In a cable television converter having channel selection means associated with a system that transmits a pilot signal which is harmonically related to the desired IF signal along with the video and sound frequency carrier received at the input of said converter for each TV channel, phase locked loop means (PLLM) connected at the input of said converter for producing an output signal locked to the carrier frequency for the selected channel, pilot signal conversion means (PSCM) having two inputs, the first of said inputs being connected to the input of said converter, the second of said inputs being connected to the output signal of said PLLM, said PSCM producing an output signal which is the difference between the IF frequency and the output signal of said PLLM, and combining means having two inputs, the first of said inputs being connected to the modulated carrier frequency, the second of said inputs being connected to the output signal of said PSCM, said combining means processing said input signals to produce a constant IF output signal.
Claim 3
Dependent Claim
25 words
The circuit of claim 1 further characterized in that said IF output signal of said combining means is a constant frequency for all channels selected.
Claim 4
Dependent Claim
21 words
The circuit of claim 2 further characterized in that said pilot signal is a predetermined constant frequency for all channels selected.
Claim 5
Dependent Claim
43 words
The circuit of claim 3 further characterized in that said PLLM includes pre-selector circuit means and oscillator circuit means, said pre-selector circuit means being connected at the input of said converter and being tracked so as to tune with said oscillator circuit means.
Claim 6
Dependent Claim
22 words
The circuit of claim 4 further characterized in that said pilot signal is equal to a submultiple of the IF output frequency.
Claim 7
Dependent Claim
69 words
The circuit of claim 1 further characterized in that said PLLM includes a phase detector, a DC amplifier and an oscillator, said phase detector including an output and two inputs connected to compare said oscillator frequency and said carrier frequency for the selected channel, said DC amplifier being connected to the output of said phase detector having an output connected so as to control the frequency of said oscillator.
Claim 8
Dependent Claim
34 words
The circuit of claim 1 further characterized in that the frequency of said pilot signal and said IF frequency is different in various converters to achieve an address code for special areas or groups.
Claim 9
Dependent Claim
45 words
The circuit of claim 7 further characterized in that said PSCM includes a decoding means connected at the input of said converter, said decoding means being arranged to provide a disconnect signal when a given code is sent to disconnect the converter from the system.
Claim 10
Dependent Claim
70 words
The circuit of claim 8 further characterized in that said PSCM includes clipper means connected at the input of said converter to remove said modulation on the pilot signal for use in producing the output signal equal to the difference between the IF frequency and the output signal of the PLLM so as not to pass the modulation on the pilot signal to said IF output of the combining means.
Claim 11
Dependent Claim
30 words
The circuit of claim 6 further characterized in that conventional carrier sync pulses are deleted from the carrier signal and transmitted with the pilot signal for a pay television system.
Claim 12
Dependent Claim
44 words
The circuit of claim 6 further characterized in that the carrier signal is FM modulated and in that said PLLM includes decoding means for a pay television system to switch said PSCM on and off by processing the output signal of said DC amplifier.
Claim 13
Dependent Claim
33 words
The circuit of claim 1 further characterized in that said PSCM includes a selector and a multiplier, said selector being connected to said converter input and said multiplieR being connected to said selector.
Claim 14
Dependent Claim
47 words
The circuit of claim 12 further characterized in that said PSCM includes a subtraction circuit, one input of said subtraction circuit being connected to said multiplier and the other input being connected to said PLLM, the output of said subtraction circuit being connected to said combining means.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-12-30 | 1978-07-01 | 1978-12-31 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-12-30 | 1982-07-01 | 1982-12-31 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-12-30 | 1986-07-01 | 1986-12-31 | $7700.00 | Window Closed / Lapsed |