Apparatus for degrading Q in a high-Q RF pulse transmitting system and the like

Apparatus for degrading the Q of a resonant circuit during quiescent periods and the like, having, in combination, a resonant circuit adapted to be excited by impulses to generate therein current oscillations of predetermined frequency, pulse generating means connected with the resonant circuit to excite the same into oscillation in response to a predetermined pulse, loss-producing means connected between said pulse generating means and said resonant circuit and operative, when so-connected, to lower the Q of said circuit such that resonant excitation thereof is inhibited, and switching means operable synchronously with the said pulse generating means for effectively removing said loss-producing means during the time of the generated pulse, thus to restore the Q and enable such pulse to excite the resonant circuit into said oscillations of predetermined frequency, said last-named means comprising switch-controlled rectifier bridge means connected with resonant capacitor charging and discharging circuits, the rectifier bridge means being normally back-biased by the charged capacitor to maintain the effective connection of the loss-producing means operative, and the discharging circuit, upon operation of said switching means, causing conduction of the rectifier bridge means effectively to remove said loss-producing means to permit the generated pulse to excite the resonant circuit, the time of re-charging through the resonant capacitor charging circuit being adjusted to open the switching means and back-bias the rectifier bridge, thus to restore the loss-producing means and lower the Q of the resonant circuit again.