| 摘要 |
The type of transmitter used is of the broad band type, and comprises a local oscillator (10) and one stable (11), and a back-coupled shift register or so-called pseudo noise register controlled by the stable oscillator (11). A multiplier (13) partly receives the carrier wave from the local oscillator and partly the pulse signal from the pseudo noise register. An amplifier (14), and an aerial (15) for transmission of the phase-modulated signals produced by the multiplier are also provided. The oscillator frequency can be from 1-30 MHz and the pseudo noise shift register frequency can be 0.1 MHz, giving a pulse length of 10 micro-seconds. The shift register produces a pseudo-random pulse sequence of alternating positive and negative pulses. In the multiplier are multiplied the produced carrier wave and the PN register pulse sequence, the positive signal from the register signifying that the carrier wave is unaltered, whilst the negative signal shows that the carrier wave has been phase-switched through 180 degrees. (Provisional Basic advised week 85/44) |
