| 摘要 |
A modulator for an instrument landing system includes a source of a radio frequency carrier wave and a first power divider coupling the carrier wave to a first hybrid combining circuit and through a second power divider to first and second constant input impedance audio frequency double sideband suppressed carrier generators with good isolation. The sideband generators are coupled to a second hybrid combining network having a double sideband suppressed carrier difference signal output, constituting a "sideband" output of the modulator, and a double sideband suppressed carrier sum output which is combined with the carrier wave in the first hybrid combining circuit to provide a "carrier wave" output of the modulator. The sideband generators each include a capacitor bridge, and phase shift means are provided so that the signals on one side of the bridge are reversed in phase with respect to signals on the other side thereof. The bridges are each formed by a pair of spaced parallel stator plates having four facing conductive patterns and a motor driven rotor having a plurality of pie-shaped conductive patterns positioned therebetween. The shape and size of the stator conductive patterns, the number of rotor conductive patterns, and the speed of rotation of the rotor are so selected that a sinusoidal audio frequency modulation of the carrier wave is effected.
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