| 摘要 |
PURPOSE:To enable to monitor the S/N of channel with good accuracy independently of the reception level, by transmitting/receiving the S/N tone singal adjacent to transmission signal band in mobile radio system, and comparing the signal level and the noise level. CONSTITUTION:Tone signal fT produced from a S/N tone signal generating circuit of the base station, is modulated at a transmitter 8, it transmitted to a mobile station from a transmission antenna 9, and electromagnetic waves returned from the mobile station are received at an antenna 1, and the reception S/N tone signal fT(R) converted into voice band is mixed with a transmission tone signal fT at a mixer 10. Noise component fN is output from the mixer 10, and the noise voltage EN proportional to the noise level filtered and detected is input to a comparator 5. On the other hand, the signal voltage Es corresponding to the level of the signal fT(R) obtained from instantaneous values ea, eb of the reception tone signal fT(R) from commutating filters 17a,17b, is input to the comparator to obtain Es/EN, that is, S/N. |
