GB1514557A - Colour television signal converter and process of conversion - Google Patents

Abstract

1514557 Television THOMSON-BRANDT 15 Oct 1975 [15 Oct 1974] 42342/75 Heading H4F A line sequential chrominance input signal is converted into a PAL type chrominance signal by supplying the input signal to a suppressed carrier modulator 18 which receives a sub-carrier wave from oscillator 12 directly and via a 90 degree phase shifter 11 line sequentially (switch 6). The resulting line sequential chrominance modulated (in phase quadrature) sub-carrier is then fed via a one line period delay 21 and via a line sequential sign-changing circuit 17 to a mixer circuit 26 (which also receives the luminance signal Y), to thereby derive at ouput 28 a PAL type chroma signal. Amplifier-adder 3 receives colour burst envelope pulses I which may have different amplitudes in consecutive lines. The input signal at 1 may be derived from HF or IF decoding circuits receiving SECAM (RTM) type signals, and the output signal at 28 may be fed via HF or IF coding circuits to an unmodified PAL receiver. Amplitude weighting circuits 9 and 10 which calibrate the relative levels of the two subcarrier waves may be connected as shown, or at input 1 to amplifier-adder 3 (Fig. 5, not shown) or before or after modulator 18 (Fig. 6, not shown).