| 摘要 |
1446351 Television transmission SIEMENS AG 8 Aug 1973 [11 Aug 1972 17 May 1973 11 July 1973] 37577/73 Heading H4M To transmit television programmes in frequency bands normally reserved for telecommunication channels in a carrier frequency system the programmes are first modulated on a common carrier frequency of 6799 kHz then converted in pairs to occupy a position between 20 and 40 MHz allotted to the basic quinary group of the system at which the carriers (e.g. 31041 and 32759 kHz) are separated by substantially 1À7 MHz and are centred on a frequency (31900) which is an integral multiple of 1À1 MHz, further pairs of TV channels being converted to positions each side of the basic quinary group by carrier frequencies which are different multiples of 2À2 MHz, those above the basic quinary group being spaced by 9 times 2À2 MHz. In this way interference products lie in frequency bands between channel pairs. All the carrier frequencies above 6799 kHz are provided by multiplication of a fundamental 0À44 MHz oscillator (Fig. 3, not shown). |
