GB1049775A - Improvements in or relating to apparatus for and methods of frequency synthesis - Google Patents

Abstract

1,049,775. Automatic frequency-control. PLESSEY CO. Ltd. Feb. 15, 1963 [Nov. 16, 1961], No. 41056/61. Heading H3A. An oscillator generator operating by frequency synthesis comprises a source of standard frequencies and a number of identical stages A, B and C each including a discriminator 11, a variable frequency oscillator 10, a mixer 12, filter 14 and a decade switch 13. The generator provides an output in 100 c/s. steps in the range 2-3 Mc/s. and includes means 18, 19 for dividing the output of a 5 Mc/s. standard 17 to a 100 kc/s. signal which is applied to harmonic generator 20 to provide on lines 16 a series of signals from 1À8 to 3À0 Mc/s. in 100 kc/s. steps. Decade switch 13d selects one frequency in the range 2À1-3À0 Mc/s. and decade switches 13a-13c each select a frequency in the range 1À8-2À7 Mc/s. The signal f1 selected by switch 13d which sets the 100 c/s. figure of the final frequency, is divided by 10 in unit 15c before application as one input to discriminator 11a which has a second input obtained via filter 14a from mixer 12a to which the output of variable frequency oscillator 10a and a frequency f2 selected by switch 13a, which sets the 1 kc/s. figure of the final frequency, are applied. The discriminator controls the frequency of the oscillator to f1 10<SP>-1</SP>+f<SP>2</SP>. The output of oscillator 10a is divided by 10 in unit 15a before application to stage B which includes the 10 kc/s. setting switch 13b which selects a frequency f3 for application to mixer 12b and the output of this stage is again divided by 10 before application to the final stage C which includes the 100 kc/s. setting switch 13c which selects frequency f4 for application to mixer 12c. The final frequency from variable frequency oscillator 10c then equals f4+f3.10<SP>-1</SP>+f2.10<SP>-2</SP>+f1.10<SP>-3</SP>.