Frequency synthesizer for a television receiver

Abstract

Abstract 1. A frequency synthesizer for synthesizing a frequency (FO) which is determined on the basis of two reference frequencies (FR and FH) and which is determined such that ¦FR-FO¦ = n . FH, n being N1/N2 and N1 and N2 being positive integers, comprising a controlled oscillator, the free frequency F of which is close to FO, a first multiplier (3) receiving FR and F and supplying the frequency FR-F, a first divider (6), whose return to zero input receives the frequency FR-F and which supplies the frequency FR-F/N1, a second divider (8) whose return to zero input receives the frequency FH and which supplies the frequency FH/N2, a first coincidence detector (7) receiving the output signals of the first and second dividers and supplying to the controlled oscillator (1) a control signal of positive or negative polarity according to whether the output signal of the first divider proceeds the output signal of the second divider or vice versa, characterized in that it further comprises validation means (20 to 24) acting on the return to zero inputs of both dividers in order to validate them whenever two pulses of the signals at the frequencies ¦FR-F¦ and FH appear substantially at the same moment, the validation lasting until the outputs of the two dividers show simultaneously a high level.

Inventors

• 👤 Michel Imbert
• 👤 Michel Van Den Driessche

Bibliographic Details