TH19584B - Digital methods and instruments for measuring the frequency of intermediate frequency signals. - Google Patents

Abstract

The TV's tuning system includes an automatic digital fine tuning unit (AFT) for producing digital AFT signals, for representing the deflecting of the IF signal carrier frequency from a specified frequency. to Counter for counting internal carrier cycles during a single counting interval. repetitions which occur during a measurement period with an interval of at least as long as the time of one field of the television signal. The interval and the interval of the counting interval are selected. so that at least one counting interval occurs in between Vertical Blanking Range where the image carrier is not overly modulated. and therefore won't make a mistake in the low count. The body of the counter is evaluated at the end of each counting cycle to determine if the first count corresponds to the specified frequency. or the second integer corresponding to the frequency at which the passive frequency deflection is produced. at the end of the measurement range The image carrier frequencies relative to the specified frequencies are evaluated by any counting. If there is a number of the first and the second The low frequencies are indicated by the non-occurrence of counts on both frequencies within the predetermined limits. The high frequencies were indicated by the occurrence of counting, both techniques used did not require that the rhythmic signal be correct. Synchronized with vertical blanking range 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 interval. 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.