GB542077A - Signal amplitude limiting circuits - Google Patents

Abstract

542,077. Wireless receiving apparatus. PHILCO RADIO & TELEVISION CORPORATION. April 18, 1940, No. 7028. Convention date, May 13, 1939. [Class 40 (v)] An arrangement for limiting the amplitude of undesired signals comprises a tuned coupling transformer the input of which is shunted by a biased diode, and the output of which is shunted by a diode having in series with it a resistance shunted capacity. As shown, a high frequency valve 3 is coupled by a double tuned transformer 4 to signal utilization means having input terminals X, Y. The primary 20 is shunted by a diode 5 biased by resistance 11, while secondary 23 is shunted by a diode 6 in series with a circuit 22, 24. Noise impulses of greater than a predetermined amplitude cause diode 5 to conduct to short circuit the primary 20. Also the time constant of 22, 24 is made large enough so that impulses of steep wave front cause diode 6 to conduct and short circuit the output circuit. This increases the impedance of the tuned primary circuit presented to valve 3 and hence a higher voltage appears across the primary. This will cause diode 5 to conduct even for signals of a lesser amplitude than would cause it to conduct in the absence of diode 6.