Abstract: A quadrifilar antenna for use in satellite communications comprises four conductive elements arranged to define two separate helical pairs, one slightly differing in electrical length than the other, defined by a cylinder of constant radius supported by itself or by a cylindrical non-conductive substrate. The two separate helical pairs are connected to each other in such a way as to constitute the impedance matching, electrical phasing, coupling and power distribution for the antenna. In place of a conventional balun, the antenna is fed at a tap point on one of the conductive elements determined by an impedance matching network which connects the antenna to a transmission line. The matching network can be built with distributed or lumped electrical elements and can be incorporated into the design of the antenna.

Abstract: A quadrifilar helix antenna for use in satellite communications comprises four conductive elements arranged to define two separate helically twisted loops, one slightly differing in electrical length than the other, to define a cylinder of constant radius supported by itself or by a cylindrical non-conductive substrate. The two separate helically twisted loops are connected to each other in such a way as to constitute the impedance matching, electrical phasing, coupling and power distribution for the antenna. In place of a conventional balun, the antenna is fed at a tap point on one of the conductive elements determined by an impedance matching network which connects the antenna to a transmission line. The matching network can be built with distributed or lumped electrical elements and can be incorporated into the design of the antenna.

Abstract: A variable FET attenuator uses feedback in a control loop to correct the attenuator automatically for input/output return loss as the attenuator is varied with a control signal input. Both the series and shunt variable FETs are set to the proper conductance to maintain a proper input match with a desired attenuation value. A second, reference attenuator circuit provides feedback control of the primary attenuator circuit through an operational amplifier. The reference circuit is designed to be electrically equivalent to the attenuator circuit in terms of characteristic impedance. The control nodes, and attenuation control signal input and an output from the operational amplifier, are paralleled so that both the reference and primary attenuator circuits behave identically, without having to RF decouple the feedback loop from the attenuator circuit. Preferably, identical bridged-T variable attenuators are used for both the attenuator circuit and the reference circuit.

Abstract: An improved method of completely erasing images stored by memory-type electroluminescent display panels. The method comprises interrupting the a.c. sustaining bias signal normally applied to the panel and impressing an erase pulse that is opposite in polarity to the last-preceding sustaining pulse or cycle. The amplitude and duration of the erase pulse are chosen to effect relaxation of the EL layer's internal field. The sustaining bias signal is then restored to place the panel in an erased, ready-to-write condition.

Abstract: A direct view cathode ray storage tube utilizes a thin film electroluminescent layer as a part of the target structure so that the electron beam writes information on the phosphor layer and written areas of the phosphor layer activate corresponding areas of the electroluminescent layer so that these areas are illuminated thereby visibly displaying such information which are stored by the electroluminescent layer so long as sustain pulses are applied thereto. Selective erasure of the written displayed information can also be accomplished.