| 摘要 |
PURPOSE:To improve the articulation of a received voice signal by applying amplitude modulation to a tone signal at a subcarrier frequency in a transmission band of a carrier line, sending both side bands, allowing a base station to apply envelope detection and inputting the obtained tone signal to a radio transmitter. CONSTITUTION:A tone signal ft generated in an oscillator 8 is amplitude- modulated by an output fc of an oscillator 9 at an amplitude modulator 10, converted into a double side band transmission amplitude modulation signal and combined with a voice signal whose band is limited via a high pass filter 11 at a low pass filter 1 and the result is inputted to a carrier line 2. A low pass filter 3 of a base station extracts the voice signal and inputs it to a radio transmitter 5, uses a high pass filter 4 to extract fc-ft, fc, fc+ft and a detector 7 demodulates (envelope detection) the tone signal ft and it is inputted to the radio transmitter 5. Thus, the synchronization transmission of the tone signal is attained and the listening sense of the mobile body radio equipment is considerably improved. |
