SU801261A1 - Frequency synthesizer - Google Patents

Description

(54) FREQUENCY SYNTHESIZER

The invention relates to radio engineering and can be used in devices for amplitude-phase synchronization of frequency. A known frequency synthesizer contains a ring-coupled voltage-controlled oscillator, a first frequency divider with a variable division factor, a pulse-phase detector and a low-pass filter, as well as a series-connected frequency generator and a second frequency divider with a variable division factor The output of which is connected to another input of the pulse-phase detector C. However, in the known device, the acquisition band is not wide enough to simultaneously suppress noise multiple to the reference frequency. The purpose of the invention is to expand the capture band while suppressing interference that is a multiple of the reference frequency. The goal is achieved by the fact that, in a frequency synthesizer, a ring controlled oscillator, a voltage controlled first frequency divider with a variable division factor, a pulse phase detector and a low pass filter, and a serially connected reference frequency generator and a second frequency divider with neumennvl the division ratio, the output of which is connected to another input of the pulse-phase detector, between the output of the pulse-phase detector and the control input of the second frequency divider The split-ratio was introduced using a sequential-connected ghosting device and an analog-to-digital converter. The drawing shows a structural electrical circuit of a frequency synthesizer. The frequency synthesizer contains a voltage-controlled oscillator 1, the first 2 and second 3 frequency dividers with a variable division factor, a pulse-phase detector 4, a low-pass filter 5, a reference oscillator 6, analog-digital converter 7, and device 8 galvanically isolated . The proposed frequency synthesizer works as follows. In the stationary mode, the division factor of the 3 frequency divider does not change, and the frequency ujg corresponds to the step

synthesizer frequency grids. In the transfer mode (when changing the frequency of the synthesizer), the error signal voltage (variable component, coming from the output of the pulse-phase detector 4 through the device 8 to the input of the analog-digital converter 7, changes the division factor of the divider 3 frequency (and hence the frequency C1 hm-) so that the system provides capture conditions.

Dynamics of a frequency synthesizer based on a pulse-phase-locked loop with a frequency divider 2 in the feedback branch, having a division factor N, with a hold band fi, the transfer coefficient of the low-pass filter 5 K (P pulse-phase detectors 4 types sample-memory, The sampling pulse period TQ (T and the pulse phase detector characteristic 4 F () is described by the equation

-Tr

P.Kp ± V-F.))

- .o y VA

where P g- is a differential operator,. vani on time; о (+ - пТо) - delta - Dirac function) - the frequency of the reference pulses to the pulse-phase detector 4; guNy - frequency generator 1;

controlled by the voltage at the time of the ring closure by the pulse-phase auto-tuning of the frequency;

Tn is relative initial detuning. Provided

(2)

where the band capture ring pulsed-phase-locked loop. Due to the periodicity of the function F (p) after closing the loop of the auto-tuning in the system, the beating mode is set. In the beat mode, the voltage of the error signal at the output of the pulse-phase detector 4 periodically changes in proportion to the difference (2), and simultaneously in proportion to periodically changes

qac QTacJp HIf we change the value of cJjf for the duration of the transition process so as to reduce the difference ((21 and ensure that the condition

NV Cx; 3Tit) HyH ≈MB g

then the system captures and sets the synchronism mode. In synchronism mode i) et const, i) gun const.

(four)

M “-i ;, the pulse-phase-locked loop system works in the same way as the known system.

In the proposed device, the change in a) at the time of the transition process is carried out using a 3 frequency divider controlled by an analog-digital converter 7 and connected to the output of a pulse-phase detector 4 tepe3 device 8.

5 completion of the transient process at the threshold of sensitivity of the analog-to-digital / converter 7, is higher, the fluctuation level of the output voltage of the pulse-phase detector 4, the division factor of the frequency divider 3 is set to the same, providing the frequency of the synthesizer frequency grid.

The use of the proposed device allows to expand the capture band of the pulse-phase-locked loop system and to provide the required suppression of the interference frequency of Comparisons 01) 37 in the output voltage of the 3D pulse-phase detector 4.

Claims (1)

Invention Formula Frequency synthesizer, containing a ring-connected voltage-controlled oscillator, a first variable frequency divider with a variable division factor, a pulse-phase a detector and a low-pass filter, as well as a series-connected reference frequency generator and a second frequency divider with a variable division factor, the output of which is connected to the other input of the pulse-phase detector, characterized in that, in order to broaden the capture band while suppressing interference, multiples of the comparison frequency, between the output of the pulse-phase detector and the control input of the W: oro frequency divider with a variable division factor, serially connected galvanic devices are introduced second decoupling and analog-to-digital converter. Sources of information taken into account in the examination 1. US Patent No. 3813610, cl. 331-1A, 05/28/74 (prototype). shzt