Crystal controlled all-band television tuning system
阅读：475发布：2021-07-10
专利汇可以提供Crystal controlled all-band television tuning system专利检索，专利查询，专利分析的服务。并且A continuous tuning system for a television receiver operable over all VHF and UHF broadcast bands and over a cable band of substantial range, in which all channel selection is controlled by a single fixed-frequency precision pulse signal source, preferably derived from a crystal-controlled oscillator. The system comprises a tunable oscillator incorporated in a phaselock loop that includes a modulator which modulates the tunable oscillator output with a low-duty-cycle pulse signal of precisely controlled frequency to develop a braod spectrum signal with sidebands at intervals corresponding to the pulse frequency. A selector circuit in the loop selects one sideband from the modulator output for application to a phase comparator for comparison with a reference signal, adjustable over a limited span, to offset the tunable oscillator output and compensate for variations of the beating frequencies required for different reception channels from integral multiples of the channel separation frequency. The comparator, in turn, controls the frequency of the tunable oscillator. The reference signal generator is precisely controlled in frequency by the same crystal control circuit as the pulse signal source.，下面是Crystal controlled all-band television tuning system专利的具体信息内容。
1. A continuous tuning system for a communication receiver operable over at least one reception band including a plurality of transmission channels, displaced from each other by a given channel separation frequency, comprising: pulse signal generator means for generating a low duty cycle pulse signal of precisely controlled standard frequency, harmonically related to said channel separation frequency; a main signal-controlled oscillator tunable over a broad frequency range, for generating a demodulation signal for control of demodulation of received signals; a modulator, coupled to said oscillator and to said pulse signal generator, for modulating said demodulation signal with said pulse signal to develop a broad spectrum signal including multiple sidebands of said demodulation signal at many different integral multiples of said standard frequency; selector means, coupled to said modulator, for deriving one selected sideband signal, within a given limited frequency span, from said broad spectrum signal; reference signal generator means, for generating a reference signal of predetermined precisely controlled frequency within said given frequency span; a phase comparator, coupled to said reference signal generator means and to said selector means, for developing an error signal representative of variations in frequency and phase between the selected sideband signal and said reference signal; channel offset control means for adjusting the frequency of one of said reference signal and said selected sideband signal, within said given frequency span, to compensate for different offsets of the beat signals required for different transmission channels from integral multiples of said channel separation frEquency; and means to apply said error signal to said oscillator to complete a main phase-lock loop and lock said demodulation signal on a fixed frequency.
2. A continuous tuning system for a communication receiver, according to claim 1, and further comprising precision frequency determination means, comprising a crystal, coupled to said pulse signal generator means and to said reference signal generator means, to control the frequency of both said pulse signal and said reference signal.
3. A continuous tuning system for a communication receiver, according to claim 1, in which said channel offset control means comprises an offset control phase-lock loop and means for adjusting said offset control loop to lock the frequency of said one signal at any one of a series of fixed incremental levels within said given frequency span.
4. A continuous tuning system according to claim 3, wherein said communication receiver comprises a television receiver employed for reception of television signals with a channel separation frequency of 6 MHz and requiring offsets of 1, 2 or 3 MHz, plus or minus, for different reception bands, in which said offset control means is incorporated in said reference signal generator means to adjust the frequency of said reference signal, and in which said reference signal generator means comprises: a 6 MHz crystal-controlled oscillator; a frequency divider having a division factor of six, coupled to said oscillator, for developing a signal including multiple harmonics of one MHz; and a bandpass filter, coupled to said frequency divider, for producing a signal including increments of up to five distinct integral multiples of one MHz within said given frequency span and for applying that signal to said offset control loop as a reference.
5. A continuous tuning system according to claim 3, wherein said communication receiver comprises a television receiver employed for reception of television signals with a channel separation frequency of 6 MHz and requiring offsets of 1, 2 or 3 MHz, plus or minus, for different reception bands, in which said selector means includes a mixer incorporated in said main phase-lock loop and a variable-frequency oscillator coupled to said mixer to apply a beat signal thereto, in which said offset control means adjusts the frequency of the selected sideband signal by varying the output frequency of said variable-frequency oscillator, and in which phase comparison, in said main loop, is effected at a frequency harmonically related to 6 MHz.
6. A continuous tuning system according to claim 5, in which said variable-frequency oscillator in incorporated in an auxiliary phase-lock loop and in which said offset control means comprises: a 6 MHz crystal-controlled oscillator included in said reference signal generator means; frequency divider means, coupled to said oscillator, for developing output signals at frequencies of 6 MHz divided by factors of 672, 336, or 112; a balanced modulator, coupled to said oscillator and said frequency divider means, for developing an offset reference signal at a frequency of 6 MHz plus the output signal frequency of said frequency divider and for applying that offset reference frequency to said offset control loop to develop an intermediate signal of 6 MHz plus one of the output signal frequencies of said frequency divider; and means, including a frequency multiplier, for applying said intermediate signal to said auxiliary loop for offset control.
7. A continuous tuning system according to claim 5, in which said offset control means further comprises fine tuning means for minor adjustment of the frequency of the television receiver IF signal to compensate for limited frequency variations in the carrier of a given channel and for any misalignment of the IF stages of the receiver.
8. A continuous tuning system according to claim 3, in wHich said main phase-lock loop includes a frequency divider interposed between said main oscillator and said modulator, and in which phase comparison is effected in said phase comparator at a frequency much lower than the operating frequency of said main oscillator.
9. A continuous tuning system for a communication receiver, according to claim 3, in which said communication receiver is a television receiver operable over low, medium, and high VHF reception bands and the UHF band, in which said channel separation frequency is 6 MHz, and in which said main oscillator is a UHF oscillator tunable over a range of approximately 230 MHz above and below a center frequency of approximately 720 MHz, said receiver further comprising VHF tuner means controlled by said demodulation signal.
10. A continuous tuning system according to claim 9, in which said VHF tuner means comprises a frequency multiplier, coupled to said reference signal generator means, for generating a signal in the UHF range at a high integral multiple of said reference signal frequency, and a mixer coupled to said frequency multiplier and to said UHF oscillator, for generating a beat signal for VHF band demodulation.
11. A continuous tuning system according to claim 9, said receiver further comprising CATV tuner means controlled by said demodulation signal, for reception of signals within a CATV band in the VHF frequency range. p
12. A continuous tuning system according to claim 11, in which said CATV tuner means comprises: a first mixer, coupled to said main oscillator, employing said demodulation signal to heterodyne a received CATV signal up to an initial intermediate frequency over twice the highest received CATV frequency; a frequency multiplier, coupled to said reference signal generator means, for generating a second demodulation signal at a high fixed multiple of said reference signal frequency, displaced from said initial intermediate frequency by 44 MHz; and a second mixer, coupled to said first mixer and to said frequency multiplier, for developing a second intermediate frequency signal at 44 MHz.
13. A continuous tuning system according to claim 11, in which all-band reception is effected by a single main tuning shaft actuating said main oscillator, UHF tuning being accomplished over a given integral number of half-revolutions of said shaft, and VHF and CATV tuning being accomplished over a corresponding number of half-revolutions of said shaft, the total tuning frequency range of said main oscillator being approximately the same for UHF tuning as for both VHF and CATV tuning.
14. A continuous tuning system for a communication receiver, according to claim 1, and further comprising a detector, coupled to said main phase-lock loop, for detecting movement of the error signal amplitude in said main loop through a zero level indicative of a precise lock on a given reception channel frequency to develop an externally usable precision lock signal.
15. A continuous tuning system for a communication receiver, according to claim 1, in which said modulator comprises a double balanced hot carrier diode bridge fed by an inductive loop, excited at high amplitude with said demodulation signal by inductive coupling to the inductive loop and excited at low amplitude with said pulse signal.
16. A continuous tuning system for a communication receiver, according to claim 15, in which the duty cycle of said pulse signal is of the order of two percent.
17. A continuous tuning system according to claim 1, wherein said communication receiver comprises a television receiver operating over VHF, UHF and CATV reception bands and in which said main oscillator comprises the demodulation oscillator for all of said bands.
18. A continuous tuning system according to claim 17, in which said main oscillator is a UHF oscillator and said demodulation signal is employed directly in demodulation of UHF band signals, and In which said demodulation signal is mixed with multiples of said pulse signal for demodulation of said VHF and CATV bands.
19. A continuous tuning system for a communication receiver, according to claim 1, and further comprising frequency divider means, interposed in said main phase-lock loop between said selector means and said phase comparator, to reduce the bandwidth requirements of said phase comparator and said reference signal generator means.
20. A high-frequency phase-lock loop, operable in the UHF frequency range, for operation on any one of a multiplicity of integral multiples of a standard frequency, comprising: pulse signal generator means for generating a low duty cycle pulse signal of precisely controlled standard frequency: a signal-controlled oscillator, tunable over a broad frequency range, for generating a high-frequency signal, much higher in frequency than said standard frequency; a modulator, coupled to said oscillator and to said pulse signal generator, for modulating said high frequency signal with said pulse signal to develop a broad spectrum signal including multiple sidebands of said high-frequency signal at different integral multiples of said standard frequency; selector means, coupled to said modulator, for deriving one selected sideband signal, within a given limited frequency span, from said broad spectrum signal; reference signal generator means, for generating a reference signal of predetermined precisely controlled frequency: a phase comparator, coupled to said reference signal generator means and to said selector means, for developing an error signal representative of variations in frequency and phase between the selected sideband signal and said reference signal; frequency divider means, interposed in said loop between said oscillator and said phase comparator, for reducing the bandwidth requirements of said loop; and means to apply said error signal to said oscillator to complete a phase-lock loop and lock said high-frequency signal on a fixed frequency.
21. A high-frequency phase-lock loop, according to claim 20, in which said modulator comprises a double balanced inductive loop hot carrier diode bridge, excited at high amplitude with said demodulation signal by inductive coupling to the inductive loop and excited at low amplitude with said pulse signal, and in which the duty cycle of said pulse signal is of the order of two percent.
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