| 摘要 |
PURPOSE:To reduce both the noise of a transmitter and the detouring to the receiving side, by setting the oscillating frequency of a frequency synthesizer which is used for both transmission and reception at a level twice a receiving intermediate frequency fd as high as the transmitting frequency fT. CONSTITUTION:The oscillating frequency fl of a frequency synthesizer 11 is set at fl=fT+2fd+DELTA, where fT is the transmitting frequency, fd is the receiving intermediate frequency and DELTA is the channel space. The output frequency of a modulating circuit 15 is mixed with the frequency fl to obtain the frequency fT. In this case, the output frequency of the circuit is set at 2fd+DELTA. At the same time, the receiving frequency fR is converted into the frequency fd when it is mixed with the frequency fl through a mixing circuit 19. As a result, the receiving intermediate frequency is set at fd+DELTA. In other words, no effect is given to the intermediate frequency part and its subsequent parts by setting the difference between the frequencies fT and fR at fd to secure a distance DELTA from the intermediate frequency although the frequency fT detours to the receiving side. |
