| 摘要 |
PURPOSE:To reduce the amplitude error of a modulator with a simple constitution, by making the temperature characteristic of a data signal amplifier equal to that of a reference voltage generating circuit, and inputting a data signal through the amplifier and an output of a reference voltage generating circuit to each modulation input terminal of the modulator. CONSTITUTION:A binary data signal inputted to an input terminal 1 is amplified at an amplifier 2, passes through a low pass filter 3 and a buffer circuit 4 and this output is applied to an input terminal 10 of a biphase modulator 8. Further, a reference voltage generating circuit 5 has the same temperature characteristic as that of the amplifier 2, and the output is attenuated at an attenuator 2, passes through a buffer circuit 4' and is applied to an input terminal 9 of the modulator 8. Even if the output of the amplifier 2 and the buffer circuit 4 is fluctuated due to temperature change, since the output of the circuits 5 and 4' is changed equally, a voltage between input terminals 9 and 10 of the modulator is unchanged, and the temperature characteristics of the modulator 8 are improved. |
