SU1737728A1 - Device for phase automatic-frequency control - Google Patents

Abstract

The invention relates to radio engineering and can be used in frequency synthesizers. The purpose of the invention is to increase the spectral frequency of the output oscillation in a wide frequency range. The device contains a tunable oscillator 3, the lead path 4. phase detector 1, low pass filter 2, forming a phase locked loop. The functional code converter 7 and the digital-to-analog converter 8 form a voltage that controls the slope of the phase detector 1 depending on the codes on the outputs of the pre-casting unit 4 and the range selection unit 5. At the same time, the static gain of the ring is constant when switching and changing the steepness of controlled generators 3.1-З.п and changing the division ratio of the frequency conversion path, which allows maintaining the optimum purity of the output oscillation spectrum when changing the output frequency of the device. 1 il.

Description

The invention relates to a frequency synthesis technique and can be used in frequency synthesizers constructed according to an active synthesis scheme.

A phase locked loop device is known comprising a phase-connected phase detector, a low-pass filter, a tunable oscillator, the output of which is the output of the device, and a lead path, the output of which is connected to the first input of the phase detector. The input of the device is the second input of the phase detector (see M. Zaretsky, M. Movshovich M. A. Frequency synthesizers with a phase self-tuning loop. M: Energiya, 1974, p.14,15).

The described device can operate only in a narrow frequency range not exceeding the pickup band of the PLL ring.

A phase locked loop device comprising a serially connected phase detector, a low pass filter, a tunable oscillator, a lead path, the output of which is connected to the first input of the phase detector, a second input of the phase detector and a control unit, the first output which is connected to the control input of the lead path (see M. Zaretsky, M. Movshovich. Frequency synthesizers with a phase self-tuning loop. M .: Energiya, 1974, p.207).

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Taken as a prototype, device-1 can operate in a frequency range equal to the frequency range of an adjustable oscillator.

The disadvantage of such a device is that due to a change in the static transmission coefficient as a result of a change in the division factor of the divider in the lead path and the steepness of the tunable generator, it cannot reach the limiting filtering degree of interference components and, therefore, the spectral purity of the output oscillation cannot be made high enough, and the frequency range is limited to the frequency range of the adjustable oscillator and cannot be made wide enough.

The aim of the invention is to increase the spectral purity of the output oscillation in a wide frequency range.

To achieve a goal in a phase locked loop device containing a phase detector connected in series, a low-pass filter, a tunable oscillator whose output is the device output, a lead path whose output is connected to the first input of the phase detector, the second input of the phase detector is the device input a frequency pre-casting unit and a control unit, the first output of which is connected to the control input of the lead path, the control unit is equipped with a second output and n outputs Switching, adjustable oscillator is made in API n controlled oscillators, preset tuning inputs and control inputs are respectively interconnected and are the corresponding adaptable oscillator inputs, controlled oscillator outputs are combined and are adjustable oscillator outputs, the controlled oscillator inputs are connected to the corresponding switching outputs of the control unit, the phase detector is made with a controlled steepness characteristic, and n Consequently, a functional code converter and a first digital-to-analog converter are connected, the first input of the functional code converter is connected to the output of the pre-casting unit, and the second input to the second output of the control unit, the output of the digital-to-analogue converter is connected to the control input of the phase detector, and between the pre-casting unit and tunable The generator included a second digital-to-analog converter.

The essence of the invention is that the only

adjusting the static gain factor by means of a phase detector, the slope of which is controlled by a constant voltage generated in series

a functional code converter, a digital-analog converter, and a functional code converter based on the output frequency code of the device, coefficient code

dividing the frequency divider in the casting path and the pre-casting voltage code generated by the pre-casting device generates the output voltage code of the second digital-to-analog converter so that the static gain of the device is close to constant. Thus, the proposed device allows to significantly reduce the change in the static Gain Kat. caused by the change in the slope of the control characteristic of the tunable generator and the division factor of the divider MD in the path to

the process of rebuilding the device by changing the steepness of the static characteristics of the phase detector.

 Snr Kfnch (0) RT-

where Kfnch (O) is the low-pass filter transfer coefficient for the constant component.

The calculation of the required code value of the phase detector control voltage is carried out by a functional converter.

The drawing shows a block diagram of the claimed device.

The phase locked loop contains a phase detector 1 connected in series, a low pass filter 2, an adjustable oscillator 3, a lead path 4, the output of which is connected to

the first input of the phase detector 1, the second input of the phase detector 1 is the device input, the frequency preconfiguration unit 5 and the control unit 1 b, the first output of which is connected to the control input of the conversion path 4. The control unit b is equipped with a second output, n switching outputs. Adjustable generator 3 is made in the form of n controlled generators 3.1-З.п, presetting inputs and control inputs of which are respectively interconnected and are the corresponding inputs of adjustable oscillator 3. The outputs of controlled oscillators are combined and are the output of adjustable oscillator 3, output devices. The switching inputs of controlled generators 3.1-3, n are connected to the corresponding switching outputs of the control unit 6.

Phase detector 1 is made with a controlled slope.

A functional code converter 7 and a digital-analog converter 8 are entered in the device, the first input of the function converter 7 is connected to the output of the preliminary frequency adjustment unit 5, and the second input to the second output of the control unit 6. The output of the digital-analog converter 8 is connected to the input control of phase detector 1. A digital-to-analog converter 9 is connected between the preliminary frequency-bringing block 5 and the adjustable oscillator 3, which is connected by the output n with the input of the preset being adjusted generator 3.

The device works as follows.

The control unit 6, in accordance with the required output oscillation frequency, switches on one of the controlled 3.1-W.P generators in the adjustable oscillator 3, sets the required division factor in the lead-in path 4 and outputs the output oscillation frequency code to the functional code converter 7.

The frequency pre-casting unit 5, through a digital-to-analog converter 9, introduces the frequency of the switched-on controlled oscillator into the pickup band of the device and outputs the code of the preliminary cocking voltage to the functional code converter 7, which digitally processes the input codes and generates the control voltage code of the phase detector 1 generated by a digital-to-analog converter 8. This voltage provides a value 5fd at which Kst is close to some calculated value, constant for all output frequencies. Thereafter, a known process of capturing and adjusting the output oscillation of the controlled oscillator is automatically carried out in the phase self-tuning ring (controlled oscillator-path conversion 4 - phase detector 1 - low pass filter 2).

As a result, by processing the code, a functional converter of code 7 takes into account all three of these factors that influence the change in 5 static ring gain factors: changing the controlled oscillator (through the output oscillation frequency code), changing the division factor of the frequency divider in the path 4 and changing

10 operating point of the characteristic of the controlled oscillator (via the voltage pre-cast voltage code). At the same time, due to the introduction of digital information processing, the structure of the system significantly

5 is simplified while maintaining a high degree of control over the static ring gain factor, therefore, the improved spectral characteristics of the output oscillation. The proposed device phase-locked loop has the following advantages compared with the prototype. If, in a device made according to the prototype scheme, the control characteristic slope of the controlled generator Sn, r changes n times, and the division factor of the divider Md changes m times, and at the frequency where Sn.r is maximum, and at MD minimal due to

0 optimizing the phase-frequency characteristic of the transmission ratio of an open ring achieves the maximum possible suppression of interfering components, then at a frequency where Sqr is minimum and Md is maximum, interference suppression will be nxm times smaller, and therefore guaranteed suppression of interfering components in the phase-locked loop , made according to the prototype scheme, will be in ph

0 x m times less than the limit.

In the PLL device made according to the proposed scheme, the phase-frequency characteristic does not depend on the frequency of the output oscillation of the ring, therefore, having achieved optimization of the characteristic for any of the output oscillation frequencies, we thereby make the characteristic optimal in the entire frequency range of the output oscillation, and therefore reach in all

0 frequency range of the maximum possible interference suppression. This means that in the device made according to the proposed scheme, a greater guaranteed suppression of the interference components can be achieved in the m x n oaz than in the device made according to the prototype scheme.

Claims (1)

The claims of a phase locked loop device comprising a series connected phase detector, a low pass filter adjustable oscillator whose output is a device output, a lead path whose output is connected to a first input of a phase detector, a second input of a phase detector frequency, the output of which is connected to the pre-tuning input of the adjustable oscillator, and the control unit, the first output of which is connected to equalization input path, characterized in that, in order to increase the spectral purity of the output oscillation in a wide frequency range, the control unit is equipped with a second output and switching outputs, the adjustable oscillator is designed as controlled oscillators, the preset tuning inputs and control inputs are connected between are the respective inputs of the adjustable generator, the outputs controlled by the generator are combined and are the output of the adjustable generator, the switching inputs of the control Generators are connected to the corresponding switching outputs. the control locator, the phase detector is made with a controlled slope, and a serially connected functional code converter and a first digital-to-analog converter are entered into the device, with the first input of the functional code converter connected to the output of the pre-casting unit and the second input to the second output of the control unit , the output of the first digital-to-analog converter is connected to the control input of the phase detector, and the second digital-to-analog converter, with the output block preliminary driving frequency is connected to the pre-entry tunable oscillator settings via second digital-to-analog converter.