JPS55140340A - Mobile radio machine - Google Patents

Abstract

PURPOSE:To improve the intermodulation characteristic of a transmitter by deciding that the mobile radio machine, which issues transmission radio waves to the base station, has approached a fixed distance from the base station and by causing the operation of the final-stage amplification part to approach class ''A'' from class ''C''. CONSTITUTION:When the mobile radio machine is distant from the base station, switch circuit 6 is turned off, and transistors which constitute final-stage amplification part 2 are so set that part 2 may perform the class ''C'' operation. At this time, the third wave generated by the external carrier and the carrier of its own station has a characteristic to generate with a level lower than the external carrier level by -10--15 dB. In case that the mobile radio machine approaches the base station, discriminator 4 detects it to send the discrimination signal to excitation part 3 and switch circuit 6, and then, the output of excitation part 3 is lowered, and circuit 6 is turned on. Thus, bleeder bias circuit 5 causes the amplification part to approach the class ''A'' operation. At this time, the level of the third wave is further lowered by -10--15 dB, thereby improving the transmitter intermodulation characteristic.