SU1059673A1 - Frequency synthesizer - Google Patents

Abstract

A FREQUENCY SYNTHESIZER containing a series-connected reference frequency generator and pulse shaper, a serially connected binary counter, a first switch, a first adder and a first pulse sequence converter, as well as a ring-mounted oscillator / frequency divider with a variable division factor, a phase detector and a low-pass filter moreover, the output of the first band-pass filter is connected to another input of the phase detector, and the control inputs of the divider, frequencies with variable frequency the AenealiH and the first switch are combined and connected to the outputs of a coarse installation of the control unit1, which is also distinguished by the fact that, in order to increase the frequency grid step while simultaneously increasing the spectral purity of the output oscillations, between binary outputs of the binary counter and the input of the first band filter entered in series are connected the second CS 1mutator, the second adder, the second impulse sequence converter, the first frequency divider, the mixer, the second band-pass filter and the second i divider The binary counter input is combined with another input (L of the second pulse sequence converter and connected to the output of the first pulse sequence converter, the other input connected to the output of the pulse generator, the output of the reference frequency generator is connected to another input of the mixer, and the exact unit setting The control cords are connected to the control inputs of the second switch. --1 oo

Description

The invention relates to radio engineering and can be used in radio communication devices and radio metering equipment, in particular, as receive oscillators for:;

A frequency synthesizer is known, comprising a reference frequency generator, a ring-connected self-oscillator, a frequency divider with a variable division factor, and a phase detector, to another input.

phase detector connected output frequency divider, the input of which

connected to a controlled oscillator of the second phase-locked loop; there is also a third phase-locked loop and a control unit, the outputs of which are connected to the setting inputs of frequency dividers with a variable division factor ClL

The disadvantage of such a frequency synthesizer is the impossibility of implementing a fine tuning step without degrading the parameters of the output signal,

 . The closest in technical essence to the present invention is a frequency synthesizer containing serially connected reference frequency generator and pulse shaper, serially connected binary counter, first switch, first adder and first pulse sequence converter, as well as ringed auto oscillator, variable frequency divider division factor, phase detector and low-pass filter, with the output of the first bands connected to another input of the phase detector th filter, and control inputs to que frequency divider with a variable division factor and a first switch coupled and connected to the outputs of the coarse setting control unit 2.

However, in the well-known frequency synthesizer, when a fine tuning step is formed, interference occurs, which, falling into the passband of the filter, degrades the spectrum of the output signal in the zone of close offsets from the useful frequency,

The purpose of the invention is to reduce the frequency step while simultaneously increasing the spectral purity of the frequency; running fluctuations.

The goal is achieved by the fact that a frequency synthesizer containing serially connected reference frequency oscillator and pulse former, serially connected binary counter, first switch, first adder and

the first pulse train and a ring-connected auto-oscillator; a frequency divider with a variable division factor; a phase detector

5 and a low-pass filter, with a k-, to another input of the phase detector connected to the output of the first band-pass filter, and the control inputs of a frequency divider with a variable coefficient- /

0 dividing the first switch and the first commutator are combined and connected to the output, I will give a rough installation of the control unit, between the binary outputs of the binary counter and the input of the first bandpass filter are entered

Consistently connected second switch, second adder, -second impulse sequence converter, first divider

0 frequency, a mixer, a second band-pass filter and a second frequency divider, the input of a binary counter is combined with another input of the second pulse-wave converter and connected to the output of the first

a pulse sequence converter, another input of which is connected to the output of the pulse former, the output of the reference frequency generator is connected to another input of the mixer, and the outputs for precise installation of the control unit are connected

to the control inputs of the second switch.

The drawing shows the structure of the proposed device. The frequency synthesizer contains the reference / frequency generator 1, the mixer 2, the pulse shaper 3,

0 the first converter 4 of the pulse sequence, binary, counter 5, the first switch b, the first adder 7, the second converter 8 of the pulse sequence,

5 second switch 9, second adder 10, control unit 11, variable frequency division divider 12 (DFD), first frequency divider 13, second band-pass filter 14, second frequency divider 15, first band-pass filter 16, phase detector 17, autogenerator 18, low pass filter 19 (low pass filter j.

5. The frequency synthesizer works as follows.

The signal frequency fl from the output of the generator 1 of the reference frequency is fed to mixer 2 and to the input of the engine 3 pulses, which converts this signal into a sequence of pulses that start binary counter 5, the bit outputs of which are connected to the signal inputs of the first and second commutators 6 and 9. Each of the switches b and 9 is turned on by the control unit 11. The first and second adders 7 and 10 carry out the summation of pulses from the outputs of the first and second switches b and 9. The pulse repetition frequencies at the output of the first and second sumlator 7 and 10 are expressed as follows P. F, FoL: 2 n-Fo; (U. (, .Р ,,, where FQ is the frequency at the output of the lower bit of the binary counter .5; the number of binary bits switched by the first switch 6,, i О, 1, 2, ... is the number of binary bits , commute with the second switch 9, j O, 1, 2, .... H}.; I tu - integer Discrete values lying in the range from O to h {jj, and from O to jMaicc. The first and second converters 4 and 8 realize the operation of the differential transformation of the pulse sequences fed to their inputs. At the output of the first transform, body 4 receives the signal 0 PI, and at the output of the second transform I ate 8 - signal / V -P2- oo () because fo where A is the division ratio of the binary counter 5. Substituted in (5J the F value from (11, we get (Lm ,. / vv.ho r - If the division ratio of the first frequency divider 13 is equal to N,; then the frequencies obtained at the output of: mixer 2 can be represented by the following dependence F.A-t. f I.) (.) / (3 These frequencies are then selected by the second band-pass filter 14 and are divided the second frequency divider 15 by the factor M, the frequency of the signal that is removed from the output of the first band-pass filter 16 can be written as i,: kLt ±). A-tri; . F 7f .. / 19) M MN VI The output frequency of the autogenerator 1§, included in the phase-locked loop, is 0 {H, where K is the coefficient of division of the CCD 12. If the coefficient K is numerically equal, the value of A + n, then the output frequency of the synthesizer can be expressed as follows) Ar (i) i (A - j). (i) The first term in Equation 11 represents the major step of the synthesizer's tuning. The second term displays the small step of the synthesizer rearrangement. The fine tuning step control is performed by the control unit 11. The size of the large and small tuning steps do not depend on the capacity of the binary counter 5, therefore, by varying the division values of the first and second frequency dividers 13 and 15, the discretization of the tuning can be varied with one and the same capacity of the binary counter 5. Auto-oscillator 18, DCPD 12 , phase detector 17 and low pass filter 19 form a phase auto tuning system that operates in frequency multiplication mode, with the nominal frequency multiplied by more than two orders of magnitude of the synthesized frequency BbDiie. In addition, the frequency synthesizer provides a significant detuning of interference from the useful frequency and makes it less likely that they will fall into the filter bands, with the first band-pass filter 16 having a very small relative bandwidth. This allows to execute its high-quality (e.g., quartz) filament and thereby ensure reliable filtering of interference beyond the limits of its passband.

Claims (1)

A FREQUENCY SYNTHESIZER, comprising a reference frequency generator and a pulse shaper connected in series, a binary counter, a first switch, a first adder and a first pulse sequence converter connected in series, as well as a self-oscillator, a variable frequency division divider, a phase detector and a low-pass filter, moreover, the output of the first bandpass filter is connected to the other input of the phase detector, and the control inputs of the divider, frequencies with a variable coefficient the division volume and the first switch are combined and connected to the outputs of the coarse installation of the control unit, and join and with the fact that, in order to reduce the step of the frequency grid while increasing the spectral purity of the output oscillations, between the bit outputs of the binary counter and a second switch, a second adder, a second pulse train, a first frequency divider, a mixer, a second bandpass filter and a second frequency divider are introduced in series with the input of the first bandpass filter, the binary counter stroke is combined with another input of the second pulse sequence converter and connected to the output of the first pulse sequence converter, another input which is connected to the output of the pulse shaper, the output of the reference frequency generator is connected to the other input of the mixer, and the outputs of the exact setting · of the control unit are connected to the control inputs of the second switch.