A Fourier Analysis of Radio-Frequency Power Amplifier Wave Forms

A theoretical treatment of class B and C radio-frequency amplifier wave forms by means of the Fourier series is presented. Assuming constant plate tuned circuit impedance, general expressions for the Fourier coefficients for any value of grid bias from cut-off to the position for class A operation are derived. The variation in plate circuit efficiency as the bias is moved from the position for class A operation to cut-off is considered. Ideal wave forms with which class C operation would be obtained are analyzed. The extent to which the ideal forms may be approached in actual operation is considered and a wave form which may be approximated in practice is analyzed. The efficiency of the several wave forms is discussed.