This paper describes the dcsign of a dircct frequcncymodulator with high modulation sensitivity. With a diclcctric resonator, two hyper-abrupt-junction varactors, and a GaAs FET, this design achieves a modulation scnsitivity greater than 20 MHz/V in a 42-GHz-band frcqucncy-modulator developed for HDTV radio cameras. When this design is used in a 7-GHz-band frequency-modulator for a ficld pick-up transmittcr gathering cmcrgency news, it provides an output power of 22 dBm, a differential gain of less than 396, and a differential phase of less than 2". All transmitters using this new frcquency-modulator havc high broadcast cfficicncy .