| 摘要 |
719,780. Generating high frequency oscillations. GENERAL ELECTRIC CO., Ltd., and BRYDEN. J. E. June 25, 1952 [July 9. 1951], No. 16265/51, Classes 40, (5) and 40 (6) A harmonic generator and selector comprises a mixer 1 fed with a variable frequency oscillation and with the harmonics of the second harmonic of a reference oscillator 3. A voltage derived from a difference frequency output of the mixer is fed to a further mixer 11 together with a reference frequency oscillation or the second harmonic thereof (according to the position of a switch 12). An output from this mixer is fed through either of two band pass filters 13, 14 having their midfrequencies spaced by the reference frequency and a voltage derived from the filter is fed to a further mixer, 17 to which is fed a second variable frequency oscillation. The desired harmonic is selected from the output of this mixer. The two variable frequency oscillations are derived from a single oscillator 2 and the circuit is such that the particular harmonic selected is determined by the frequency of the variable oscillator, the position of the switch 12 and which of the two band pass filters are used, and the output frequency is independent of small variations of the frequency of the variable frequency oscillations. In the circuit shown, with both switches 12 and 15 to the left the output frequency is the (2N-1)th harmonic of the reference oscillation and with the switches to the right the (2N-2)th harmonic is selected, N being determined by the frequency of the oscillator 2. Thus by varying the frequency of oscillator 2 in steps and using both switch positions at each step a range of adjacent harmonics may be produced. The filter 8 preferably has a mid-frequency which falls midway between two of the harmonics from the harmonic generator 6. |
