GB735940A - Improvements in or relating to harmonic generators - Google Patents

Abstract

735,940. Changing frequency. BRITISH TELECOMMUNICATIONS RESEARCH, Ltd. July 8, 1953 [July 10, 1952], No. 17449/52. Class 38 (2). A harmonic generator suitable for use in telecommunication systems may comprise a source of constant substantially sinusoidal voltage which feeds a capacitor CS in series with a rectifier W1 biased from a D.C. source, the harmonic output being derived at P1, P2 from across a small inductor LS shunted by rectifier W2 connected in opposition to W1 whereby the stepped current waveform produced is differentiated. Curves (i), (ii) of Fig. 1B show respectively the capacitor voltage and current, which would be sine waves displaced by 90 degrees (but for circuit resistance) but for rectifier W1 which at A prevents the current rising above the value set by its bias and keeps it constant until B. At B the source voltage becomes greater than the capacitor volts and the current reverses sharply to take up the value it would have had but for rectifier W1. The CS, LS circuit may be made resonant. LS is kept small to provide narrow pulses and a wide range of harmonics, and rectifier W2 damps out all but the first half period of the damped oscillations. The A.C. supply may be derived through a pentode arranged as a cathode follower, the rectifier may be combined in a double diode, Fig. 4 (not shown). In an alternative arrangement a source of constant sinusoidal current is connected in parallel with an inductor and a suitably biased rectifier, the harmonic output being obtained by differentiating the stepped voltage wave form produced, Fig. 2 (not shown).