SU1198739A1 - Digital frequency synthesizer - Google Patents

Description

The invention relates to radio engineering and can be used in receiving devices, automatic and discrete information processing systems. five

The purpose of the invention is to increase the speed and the expansion of the frequency range.

The goal is achieved by reducing the tuning time during the transition from one synthesized frequency to another and by expanding the capture band, respectively. In addition, the purity of the spectral components of the output signal is enhanced by the implementation of the detector on the elements of discrete technology.

Fig, 1 shows the structural diagram of the device; figure 2 - timing charts of his work.

The digital frequency synthesizer consists of frequency divider 1, reference frequency generator 2, detector 3, integrator 4, low-pass filter 5, controlled oscillator 6, AND 7 and trigger 8, Detector 3 consists of the first and second elements 9 and 10 and the first And the second elements And 11 and 12. The generator 2 through the first input of the detector 3 is serially connected to the integrator 4, low pass filter 5 and the generator 6, the output of which is connected to the first input of the element 7, the second input of which is connected to the output of the trigger 8 and the second input of the detector 3, electric output ment 7 is connected to the input of the divider 1, the output of which is connected to the K input of flip-flop 8, 8-input of which is connected to the output of the generator 2.

Digital frequency synthesizer works as follows.

The required value of the synthesized frequency from the output of the generator 6 is determined by the division ratio of divider 1 and frequency P _op generator 2, which produces square wave oscillations with a duty cycle (} Τ / ΐ _Η = 2, (figure 2, a). Oscillations of the generator arrive at 8-input trigger 8 and the first input of the detector 3. The trigger on the leading edge is set to one and opens element 7, through which the divider 1 receives pulses from the generator 6. The kth pulse appears at the output of the divider and sets the trigger on the K input ν to zero condition. · By The read packet K of pulses (Fig. 2, d), the K th pulse (Fig. 2, d) determine uniquely the pulse duration at the trigger output (Fig. 2, b). In the case where the frequency of the generator 6 is higher than the specified one, the back front the trigger output pulse is shifted to the left relative to the middle of the period of the reference oscillation. At the same time, an error signal is produced at the output of the detector 3 (FIG. 2, c)

15 which is integrated, smoothed by filter 5 and fed to the input of oscillator 6, whose frequency changes so that the error signal tends to zero, and 20 it becomes equal to zero when the frequency at the generator output equals £ _r = 2KG _0P .

Due to synchronization between the signals of the reference frequency and the signals of divider 1, due to trigger 8 and element 7, the generator 6 is tuned at a speed proportional to ve. the error signal at the 30 detector output. This provides high speed synthesizer.

When tuning from a high frequency to a lower frequency, the capture region in the synthesizer can be limited 35 only by the speed of the element base, and when switching from a low frequency to a high one, is determined by the duty cycle of the reference frequency pulses, and for the considered case 9 = 2 40 the relative capture band is 100%, which is almost an order of magnitude higher than in the known.

The specific execution of the detroctor circuit on two inverters 9 and 10 / and two elements And 11 and 12, with precise synchronization in the frequency control loop, almost completely suppress components in the control signal with a frequency equal to the frequency of the reference oscillation, which ensures high purity of the output spectral lines signal. This is due to the fact that, at exact synchronization, the error signal of the zero output of the detector is zero, and the voltage at the integrator's output remains constant.

1198739

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Claims (2)

1. DIGITAL SYNTHESIZER OF FREQUENCIES, containing a frequency divider, serially connected reference frequency generator, detector, integrator, low pass filter and controlled oscillator, characterized in that, in order to improve performance and extend the frequency range, an element And and a trigger are entered into it controlled generator is connected to the first input element And, the output of which is connected to the input of the divider, the output of which is connected to the β-input of the trigger, the 5-input of which is connected to the output of the reference frequency generator, and the output to the second input The signals of the And element and the detector. 2. The synthesizer according to claim 1, characterized in that, in order to increase the purity of the spectral components of the output signal, the detector contains two pairs of series-connected elements NOT and AND, the input of the first element is NOT to the first input of the detector and is connected to the second input of the second element AND , the input of the second element is NOT the second input of the detector and is connected to the second input of the first element And, the outputs of the first and second elements And are the first and second outputs of the detector, respectively. ЗЦ 1198739 > Phie 1 one 2 1198 .