| 摘要 |
1. SECAM coder comprising a generating circuit of the CHROMA subcarrier and a luminance signal processing circuit, characterized in that said CHROMA subcarrier generating circuit includes an oscillator (V) having a symmetrical structure consisting of : - two diodes (D 2) and (D 1) for receiving the input signal from the oscillator, each diode being connected one terminal of an adjustable coil (L 1) ; - a capacitor (C 13) connected, on the one hand, to one terminal of said adjustable coil (L 1) and, on the other hand, to a follow-up transistor (IC1a), further a capacitor (C 12) connected, on the one hand, to the other terminal of said coil (L 1) and, on the other hand, to a follow-up transistor (IC1d) ; - two transistors (IC1b) and (IC1c) which alternatively switch the current flowing through the resistor (R 25) onto one terminal of said coil (L 1) or onto the other terminal of the coil, the output of the oscillator being transmitted to a current generator that only depends on the difference of potential appearing at the terminals of said coil (L 1) ; - a CHROMA amplifier (III) using a C.MOS gate (IC3c) associated to a capacitor (C 19) mounted in parallel with a resistor (R 29), a capacitor (C 18), an adjustable resistor (P), a resistor (R 28), acting as a pre-accentuation means. |
