| 摘要 |
PURPOSE:To increase the apparent sensitivity for radio control units, by taking the DC component output of the AGC amplifying circuit as the gain control input through the voltage limit diode. CONSTITUTION:The DC component being the output of the AGC amplifier of the composite amplifying circuit 11 having the functions of detection, AGC amplification and low frequency amplification is picked up with the low pass filter 7, and it is inputted to the AGC line 8 via the Zener diode 9 as the voltage limit diode. Further, at non-signal, the circuit is set to satisfy the relation of (output voltage of filter 7)<= (voltage on line 8)<((output voltage of filter 7)+(Zener voltage of diode 9)). Even if the output voltage of the filter 7 is lowered even with the electric field strength increased, while the above mentioned relation is kept, no change is present to the voltage of the line 8 and no lowering in the sensitivity of weak electric field. But, when the relation is (voltage on line 8)>=((filter 7 output voltage)+(Zener voltage)), the voltage on the line 8 is lowered, the sensitivity is rapidly decreased, and saturation is avoided. |
