| 摘要 |
<p>The network is interactive (return of information to the server). It operates in two frequency ranges distinct in transmission and in reception. These two frequency ranges are divided into sub-ranges and there is a head-end modem for each sub-range. A user modem comprises a first oscillator (1) whose frequency is equal to the difference between the reception frequency (FR) and the frequency desired as intermediate frequency (FI), and a second oscillator (4) provided with a frequency slaving circuit (11). A mixer (5) mixes the signals from the two oscillators, then the signal passes through a frequency divider (2) and is brought to the slaving circuit (11). After passing through a divider (3), the signal from the second oscillator provides the transmission signal (FE). <IMAGE></p> |
