A 14-Watt Transistor CW Amplifier with a 50-mc Bandwidth

An experimental FM optical communication system under active study required an amplifier capable of delivering a one-ampere rms signal to an optical phase modulator over a 60-mc band centered at 70 mc. The optical phase modulator 1 consists of a one-meter long 15ohm strip line partially filled with K D P (potassium dihydrogen phosphate) . The amplifier must amplify the FM input signal with a minimum harmonic distortion. Since the signal is FM modulated, the amplitude linearity of the amplifier is unimportant. Rather than embark on a new design using stagger tuned amplifier sections, it was decided to modify a high-power transistor pulse amplifier 2 to operate as a CW amplifier. The general description of this modified amplifier appears in Section II of this paper. Amplifier performance and the modifications made to it are then described in Section III. Its design is presented in Section IV and a discussion of results is contained in Section V.