Patent GB-1466275-A (GB)
Title: Frequency synthesizer
IPC: H03B21/04
Filed: 1974-06-27
Abstract: 1466275 Frequency synthesizers ADRET ELECTRONIQUE 27 June 1974 [15 March 1974] 28489/74 Heading G4D [Also in Division H3] In a frequency synthesizer generating frequencies expressable in a base 4 in which a cascade of stages is provided, each stage inserting a digit, the inserting means comprises a mixer, one input of which is derived from the preceding stage or, in the first stage, from a fixed frequency source, and the other a selected one of four frequencies which succeed one another with constant steps and are derived by variable divider means. In an embodiment, the first stage Q1 comprises a mixer 7 which adds to the input frequency 21A-where A is a constanteither 63, 64, 65 or 66A these frequencies being generated from 24A in a chain comprising x 3 or x 4 divider 1 producing 6 or 8A, followed by harmonic generator 2 from which 40 or 42A are filtered out by bandpass filter 3. The output from filter 3 is applied to divider 4 which can be set to divide by 5, 6, 7 or 8, followed by harmonic generator 5 from whose output bandpass filter 6 selects 63, 64, 65 or 66A. In the output from mixer 7 bandpass filter 8 selects 84, 85, 86 or 87A for application to a 4/1 divider 9 which produces 21A, 21“A, 21¢A or 21¥A which in effect translates the position or the digits, ten such stages in all being arranged in cascade. The last of these produces an output in the range 21-22A which is applied to the mixer of a further identical stage Q11, the output from which is in the evenly-divided range 84-88A and is applied to the mixer 27 of a final stage Q12. Stage Q12 differs in that the input is 48A, filter 20 produces 80 or 84A and filter 23 produces 126, 128, 130 or 132A it is followed by 2/1 divider 24 and harmonic generator 25, so that filter 26 provides one of the frequencies 252, 256, 260, 264A. Thus the output of filter 28 comprises frequencies evenly spaced over the range 336 to 352A, forming one input of mixer 29. The second input is one of the frequencies 256, 272, 288, 304, 320 or 336A derived from a filter 47 which is preceded by an 8/1 multiplier 46 fed by bandpass filter 45 with one of the frequencies 32, 34 ... 42A derived from a mixer 44. One input of mixer 44 comprises 126, 128, 130 or 132A derived from 48A via a settable divider 32, harmonic generator 33, filter 34, settable divider 35, harmonic generator 36, and filter 37. The second input comprises 160 or 168A derived from 48A by means of settable divider 38, harmonic generator 39, filter 40, 2/1 divider 41 harmonic generator 42 and filter 43. The output from mixer 29 lying in the range 0- 96A is selected by bandpass filter 30 and constitutes the output, after amplification in amplifier 31. The frequency multipliers may be of known type using recovery time diodes, while the settable dividers can comprise shift registers with parallel synchronous inputs or alternatively decimal counters controlled by a logic device from binary signals. The Specification also discloses with reference to Fig. 2 (not shown) an arrangement, using voltage-controlled oscillators 43, 57, for generating the fixed frequencies 21A, 24A and 48A under control of a single stable 10 MHz oscillator and using phase discriminators (52, 56) and dividers (such as 54, 55). It also describes a modification of the frequency synthesizing arrangement in which stages (Q1 to Q12, Fig. 3, not shown) identical with those described are followed by further stages in a basically similar arrangement which extends the frequency range to 0-1536A.