| 摘要 |
PROBLEM TO BE SOLVED: To obtain a transmitter in which a feedback loop operates stably even when the signal band is wide and the upper-limit frequency of the band is not-negligibly high as compared with the frequency at which the phase lag of the feedback loop excluding a low-pass filter becomes 90 deg.. SOLUTION: In a transmitter which inputs base-band input signals, modulates the signals, and obtains transmitting output signals by amplifying the signals to a high output, a feedback loop which fetches part of the transmitting output signals, demodulates the base-band signals, and synthesizes the demodulated base-band signals with the base-band input signals in an anti-phase state is formed. One-step of low-pass filters 3a and 3b which limit the band of the above-mentioned feedback loop is provided between synthesizers 2a and 2b which synthesize the base band-input signals with the demodulated base-band signals and a modulator 4 which modulates the synthesized base-band signals and the 3-dB cutting-off frequencies of the filters 3a and 3b are adjusted to one to three times higher than that of the base-band signal band and, at the same time, the open loop gain of the feedback is adjusted to 10dB or above. |
