| 摘要 |
PURPOSE:To prevent the lowering of the signal quality as well as to secure the wide-band characteristics by fetching in separation the 2nd higher harmonic from the output of the traveling wave tube and then giving the feedback to the higher harmonic via the external feedback circuit composed of the phase shifter and the attenuator. CONSTITUTION:The input signal of angular frequency omega is amplified via pre-amplifier 1 featuring the linear action and then compounded with the feedback higher harmonic of angular frequency 2omega via branching filter 2 to be supplied to traveling wave tube amplifier 5. Amplifier 5 operates at the level near the saturation in order to obtain a high efficiency and cobtains a sufficient amount of the 2nd higher harmonic, and the 2nd higher harmonic only is fetched out of the output via filter 2 to be led to the external feedback circuit. And the basic signal wave of angular frequency omega is eliminated through HPF6, and the control is given through phase shifter 3 in order to secure the 180 deg.-shifted pahse from the 2nd higher harmonic generated inside amplifier 5. Then the attenuation quantity is controlled through attenuator 4 to secure the coincidence with the gain to the 2nd higher harmonic of amplifier 5. Accordingly, the feedback higher harmonic is increased as the 2nd higher harmonic delivered increases to secure the reduction, thus forming a steady feedback loop. Furthermore, the wide-band characteristics can be secured since the feedback circuit is formed with the passive element. |
