A Comparative Study of the Performance of a Class C Harmonic Generator with Fractional Sine Wave, Isosceles Triangle, and Rectangular Pulse Drives

Abstract

The full sine wave drive to a class C harmonic generator is limited at the most to the fourth or fifth order harmonic, because of the limitations in the driving power. The rectangular pulse drive through a wide band circuit, as proposed here by the author, however, does not suffer from these disadvantages. In such a system, generation of harmonics higher than the fifth order is practical. The performance of such a generator is calculated out in terms of (C_n)_opt, (d/T)_{n critical} and (A_v)_n, i.e., the values of the harmonic amplitude, angle of flow and the d.c. value of plate current in the optimum case. The (d/T)_{n critical} is inversely proportional to the harmonic number n and (C_n)_opt and (A_av)_n are also similarly related. The calculations extended to the case of fractional sine waveband isosceles triangle pulse waveforms show similar relation between the parameters. Besides, the ratio remains sensibly constant and independent of harmonic number for the three pulse waveform drives. This means that the efficiency of harmonic conversion from d.c. is constant for all harmonics in the optimum condition. Finally, the relative merits of each drive are discussed. Full sine wave drive voltages for different (d/T) ratio for the tube type QQE 06/40 is also given for comparison.