TH15845A - Digital methods and instruments for measuring the frequency of intermediate frequency signals. - Google Patents

Abstract

The tuner system includes a digital automatic tuning unit (AFT) to produce a digital AFT signal to represent the deflection of the carrier frequency, the picture of the IF signal from the specified frequency, the combined digital AFT unit. To Counter for counting the internal carrier cycle during the counting interval. Repeats, which occur during measurement periods that are at least as long as one field of the television signal. The time interval and the interval of the counting interval are selected. So that at least one count interval occurs during Vertical blanking range Where the image carrier will not be modulated too much And so it won't make the low counts go wrong. The counter body is evaluated at the end of each counting cycle to determine if the first count corresponds to the specified frequency. Or the second count corresponding to the frequency at which the passive frequency deflection has been produced. At the end of the measuring range The frequency of the image carrier relative to the specified frequency is evaluated by determining which number. If there is a first and a second count Is produced, the low frequencies are indicated by the absence of both frequency counts within the established limits. The high frequency is indicated by the occurrence of the count, the two techniques do not require that the pulsating signal be Synchronized with vertical blanking intervals for reliable counting.

Claims (6)

1. In television receivers that include a tuner for tuning RF television signals that contain a picture carrier modulated with a repeating field of video signal information. That includes line ranges that include visual data and horizontal and vertical blanking ranges that include: Synchronization data to produce an IF signal with a carrier corresponding to an RF signal carrier, where the tuner provides a path for the carrier cycle counting of the IF signal during repeating counting channels. This occurs during a measurement interval of at least as long as the duration of one field. A path for producing cadence signals, which sets the cycle count in intervals. And interpolation so that at least one count interval takes place within the vertical blanking range and the path for finding any (if any) of the first and second pre-defined counts. Is produced during the measurement period. To assess the deviation of the IF image carrier frequency from the specified frequency. 2. The machine, as specified in claim 1, where the first predetermined count corresponds to the frequency range, the first surrounds the specified frequency of the IF image carrier and the second preset count corresponds to the range. The second frequency which is higher and close to the first frequency range. 3. Devices specified in claim 1, where the means for determining any number If the first and second predefined counts are produced, it includes a method for operating under the control of a software program for counting that is produced during the counting period. Sequence with first and second predetermined numbers 4. Machine as described in claim 1, where the means of operation under control of the software program; a) after each period. The count that is produced during the counting period is determined. B) after each counting period. The counts produced during the counting period are recorded, and c) at the end of the measuring range evaluate the recorded counts. 5. The machine, as stipulated in claim 3, where the path works under the software program. The means of working under the control of the software program: a) after each interval. Will find the count that has been produced During the counting period; b) after each counting period It records a predetermined number of indications. If a first count is produced during the counting period And record the second indication If a second predefined count is produced And c) After the measurement interval, the recorded count indication at the end of the measurement interval is evaluated for the recorded count. 6. The machine, as set out in claim 3, where such means for determining which numbers (if any) of the first and second predetermined numbers are produced. Including the first and second registers For the first and second indication notes respectively If the number of values The first and the second values are produced respectively.