| 摘要 |
A non-linear filter which reduces high signal-to-noise ratio due to sharp and erratic variations in an input signal by charging a storage capacitor through a long time constant charging circuit so that the stored signal level lags an increasing input. A parallel path with a much lower time constant rapidly discharges the capacitor upon input decreases, so that the stored signal matches the more accurate lower input signal level. A practical application is for car space measurements in railroad yard storage tracks to substantially reduce erratic distance measurements due to poor shunting under moving cars. The distance measurement signal is applied through an integrator network to a first of four FET operational amplifiers, whose input and feedback networks have selected time constants to substantially filter out background noise due to the track signal frequency. The second amplifier provides a perfect rectifier for the discharge of the storage capacitor through a low time constant path when the input signal decreases. A T-shaped resistor network and the third amplifier provide longer time constants to delay the charging of the storage capacitor, in accordance with an increasing output level from the first amplifier, without requiring excessively large component values. A final amplifier provides a representative distance measurement signal output from the storage capacitor from which noise due to poor shunting by a moving car is largely eliminated for increased accuracy.
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