Generation and fast switching of high frequency rotating fields for bubble memories

Generation and fast switching of rf-rotating fields for bubble memories becomes much easier, if only one rf-switching transistor is used outside the parallel resonant circuit formed by the field coil and a capacitor. In this case pulses to the basis of that transistor are not only used to start and stop the rotation, but also to feed back the energy lost by the circuit damping. The energy to build up the field and to maintain its amplitude is delivered to the coil system by a DC source only and is returned to that, when rotation stops. A versatile field generator is described, which is able to produce fields adjustable in amplitude and frequency up to 40 A/cm and 1 MHz within a coil volume of 36 cm³.