Low noise quadrupole amplifier as a circuit element

This paper reports on recent progress and experience in building and operating low-noise electron-beam parametric amplifiers in the frequency range from 400 to 900 mc. Particular attention is devoted to characteristics which are of interest from a circuit or systems standpoint: bandwidth, gain stability, phase shift and input match. To realize the potential broad-band characteristics of the quadrupole amplifier, the resonant behavior of the electron beam is utilized by making the beam form one branch of a bandpass filter network which is then completed by appropriate external circuits. Methods of adjusting practical amplifiers for optimum bandwidth are illustrated. Measured data agree well with the theory, permitting systematic design of future models.