| 摘要 |
PURPOSE:To make it possible to eliminate a large noise completely in addition of the operation of noise AGC, by exercising control so that while the conduction of a variable impedance transistor is shallow, its gate pulse width will be large. CONSTITUTION:Since the on period of transistor TRQ5 is short with a small noise in an intense electric field, capacitor C2 of noise AGC circuit 9 is hardly charged and noise amplifier 5 operates with normal high detection sensitivity. Next, when the noise increase in a weak electric field, TRQ5 turns on frequently to charge capacitor C2 of circuit 9 and its output level drops, so that noise AGC will operate so as to decrease the sensitivity of amplifier 5. The conduction of this TRQ10 is shallow and its impedance is increased, increasing the gate pulse width. Therefore, large-noise elimination can be done perfectly in addition to the operation of noise AGC. |
