Frequency, phase and modulation control system which is especially useful in simulcast transmission systems
First Claim
1. A system for providing a signal controlled in frequency which comprises means for providing a source of reference signal, means for providing a standard signal, the frequency of which is responsive to a frequency error signal, means for providing measurements of the relative phase difference between said reference and standard signals at a plurality of times spaced in duration from each other, means for selecting said times such that said times are spaced in duration by durations that are at least greater than the period of said standard signal, means for computing a frequency error signal in terms of the ratio of the difference in said phase measurements at at least two of said times to said duration between said two times and means for applying said frequency error signal to said standard signal providing means.
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Accused Products
Abstract
A system enabling the frequency, and if desired, phase control of an oscillator which generates a standard signal useful as a carrier which is modulated by modulation signals. A multiplicity of such oscillators and associated transmitters may be used in a simulcast transmission system. The transmissions originate from a station which may be remote from the transmitters. The station has a system controller and the transmitters have transmitter controllers. For frequency control a reference signal generated in the system controller is transmitted over the same link and band width (e.g. the voice band width) with the voice modulating signals to the transmitter controllers of all of the transmitters. At the transmitter controllers, multiplicities of phase measurements are made from which statistical values of phase, deviations and times of occurrence are collected and used to provide error control signals in terms of the ratio of phase difference to time, notwithstanding that the reference signals may jitter in phase and amplitude due to noise and other errors and also notwithstanding that the phase measured at various of the times may include a multiplicity of phase wraps (the phase difference being greater than one cycle or 360°.) The frequency errors may be applied to the standard oscillator to lock the phase thereof in predetermined relationship with the reference. For modulation control codes representing deviations from matched correlation characteristics (delay, gain and frequency spectrum) are transmitted to each transmitter where modulation signal correction circuits are conditioned to process the modulating signals so that the transmissions from each transmitter will be matched in modulation characteristics.
22 Citations
36 Claims
- 1. A system for providing a signal controlled in frequency which comprises means for providing a source of reference signal, means for providing a standard signal, the frequency of which is responsive to a frequency error signal, means for providing measurements of the relative phase difference between said reference and standard signals at a plurality of times spaced in duration from each other, means for selecting said times such that said times are spaced in duration by durations that are at least greater than the period of said standard signal, means for computing a frequency error signal in terms of the ratio of the difference in said phase measurements at at least two of said times to said duration between said two times and means for applying said frequency error signal to said standard signal providing means.
- 4. A system for providing a signal controlled in frequency which comprises means for providing a source of reference signal, means for providing a standard signal, the frequency of which is responsive to a frequency error signal, means for providing measurements of the relative phase difference between said reference and standard signals at a plurality of times spaced in duration from each other, means for translating the ratio of the difference in said phase measurements at at least two of said times to said duration between said two times into said frequency error signal, means for applying said frequency error signal to said standard signal providing means, means for making a plurality of said phase measurements over an interval occurring at each of said times, means for deriving from said plurality of measurements over said intervals the means of said phase managements during said intervals and the variances of said measurements from said means, and means for enabling said applying means when said variances are within certain bounds.
- 10. A system for providing a signal controlled in frequency which comprises means for providing a source of reference signal, means for providing a standard signal, the frequency of which is responsive to a frequency error signal, means for providing measurements of the relative phase difference between said reference and standard signals at a plurality of times spaced in duration from each other, means for translating the ratio of the difference in said phase measurements at at least two of said times to said duration between said two times into said frequency error signal, means for applying said frequency error signal to said standard signal providing means, and wherein said plurality of items is at least 3, one of which is at a time intermediate said duration, and correlation determining means for determining whether the phase measurement at said intermediate time correlates with the phase measurements at the times spaced by said duration.
- 18. A system for providing a signal controlled in frequency which comprises means for providing a source of reference signal, means for providing a standard signal, the frequency of which is responsive to a frequency error signal, means for providing measurements of the relative phase difference between said reference and standard signals at a plurality of times spaced in duration from each other, means for translating the ratio of the difference in said phase measurements at at least two of said times to said duration between said two times into said frequency error signal, means for applying said frequency error signal to said standard signal providing means, and means responsive to said phase measurements for adjusting said measurement at the end of said duration to accommodate one or more wraps in said measurement where said phase difference exceeds one cycle or multiples thereof.
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22. A system for providing a signal controlled in frequency which comprises means for providing a source of reference signal, means for providing a standard signal, the frequency of which is responsive to a frequency error signal, means for providing measurements of the relative phase difference between said reference and standard signals at a plurality of times spaced in duration from each other, means for selecting said times such that said times are spaced in duration by durations that are at least greater than the period of said standard signal, means for translating the ratio of the difference in said phase measurements at at least two of said times to said duration between said two times into said frequency error signal, means for applying said frequency error signal to said standard signal providing means, and means for changing said frequency error signal by an amount corresponding to a predetermined frequency offset thereby locking said standard signal to a frequency which differs from the frequency of said reference source by said offset.
- 23. The method of deriving a measurement of the frequency error between a standard signal and a reference which may be corrupted by noise and other error signals, which method comprises the steps of collecting a multiplicity of sample phase measurements of the phase difference between said reference and standard signal at a predetermined rate during an initial interval of predetermined duration and at a plurality of other intervals each occurring later in time, generating a table for each of said measurements containing its mean value, its statistical deviation and the time of its occurrence, adjusting the mean phase values in the table except for the mean phase value for the initial interval until the values lie within a predetermined multiple of their standard deviation from a line between the last and initial ones of said mean phase values which line represents an indicated frequency error thereby indicating a correlation condition, outputting said indicated frequency error as said frequency error when said indicated frequency error is less than a predetermined multiple of the sum of the standard deviations of the initial and last of said standard deviation values in said table.
- 26. A communication system for matching signals transmitted simultaneously by a plurality of transmitters in their modulation characteristics which comprises a station for generating said signals, said station having system controller means for generating calibration signals, a plurality of transmitter controller means each connected to a different one of said transmitters, each of said transmitter controller means having means for controlling the modulation characteristics transmitted therethrough, means for transmitting said calibration signals at different times to different ones of said transmitters, means at said station for receiving said calibration signals from said transmitters, said system controller having means for correlating said calibration signals received from said transmitters with each other and for transmitting digital control signals to each of said transmitters representing differences in said modulation characteristics therebetween, and means in said transmitter controller means responsive to said digital control signals for operating said modulation characteristic controlling means to match said modulation characteristics of said transmitters.
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29. A system for providing a signal controlled in frequency which comprises means for providing a source of reference signal, means for providing a standard signal, the frequency of which is responsive to a frequency error signal, means for providing measurements of the relative phase difference between said reference and standard signals at a plurality of times spaced in duration from each other, means for selecting said times such that said times are spaced in duration by durations that are at least greater than the period of said standard signal, means for translating the ratio of the difference in said phase measurements at at least two of said times to said duration between said two times into said frequency error signal, means for applying said frequency error signal to said standard signal providing means, and means for selecting said times so that a plurality of said durations are unequal from each other and are not integral multiples.
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30. A system for providing a signal controlled in frequency which comprises means for providing a source of reference signal, means for providing a standard signal, the frequency of which is responsive to a frequency error signal, means for providing measurements of the relative phase difference between said reference and standard signals at a plurality of times spaced in duration from each other, means for selecting said times such that said times are spaced in duration by durations that are at least greater than the period of said standard signal, means for translating the ratio of the difference in said phase measurements at at least two of said times to said duration between said two times into said frequency error signal, means for applying said frequency error signal to said standard signal providing means, and said means for providing a source of reference signal including means operative to provide said reference signal intermittently at times spaced in duration from each other corresponding to the times when said measurements are made.
- 31. In a communications system wherein information signals are transmitted over a certain bandwidth from a station for retransmission by transmitters remote from said station and each of which has an oscillator, a control system for controlling said oscillators of said transmitters which comprises means for transmitting reference signals in said bandwidth from said station to said transmitters at a plurality of times the interval between which is varied, means for selecting said times such that said times are spaced in duration by durations that are at least greater than the period of said reference signal, transmitter controlling means in each of said transmitters having means for providing measurements of the phase differences between said reference signals and signals from the oscillator thereof at each of said times, means for providing outputs corresponding to the slope of said phase measurements to provide frequency error signals, and means for providing said error signals to said oscillator.
- 35. In a communication system having a plurality of transmitters for transmitting signals simultaneously, said system having a station for generating said signals and also for generating control signals, apparatus for controlling the modulation characteristics of said signals, which said transmitters are transmitting comprising transmitter controllers in each of said transmitters, means for operating said transmitter controllers with said control signals, CODECS in said transmitter controllers for applying said signals which said transmitters are transmitting to said transmitters, said CODECS having means for converting said signals into PCM signals and back from PCM signals into said signals which said transmitters are transmitting, and means in said transmitter controllers for addressing said CODECS to interpose selective delay on said signals being applied to said transmitters.
Specification