RU2794104C1 - Digital oscillator of variable frequency - Google Patents

Abstract

FIELD: pulse engineering, radio engineering.

SUBSTANCE: the invention is intended for use in pulse engineering and radio engineering, in digital devices for the formation of cosine oscillations with two frequency values, in particular signals with minimal frequency manipulation. The device contains a clock input 1, an information input 2, a D-trigger 3, the first controlled frequency divider 4, the second controlled frequency divider 5, an initial phase decoder 6, a digital-analog oscillator 7 of cosine oscillation and output 8. The accuracy of the output signal generation is determined by the number of steps of the approximating function.

EFFECT: increasing the spectral efficiency of the generated signals due to the formation of signals with minimal frequency manipulation with the initial phases

which are an approximation of continuous cosine oscillations of various frequencies by a step function of time.

1 cl, 8 dwg

Description

Field of technology to which the invention relates

The invention relates to pulse technology and radio engineering and can be used to form cosine oscillations with two frequencies, in particular signals with minimum frequency shift keying (MFM signals) in discrete information transmission systems.

State of the art

Closest to the proposed is a digital variable frequency oscillator containing the first controlled frequency divider, the clock input of which is the clock input of the digital generator, the second controlled frequency divider and a D-flip-flop, the D-input of which is the information input of the digital generator, the direct output of the D-trigger connected to the control input of the first controlled frequency divider, the inverse output of the D-trigger is connected to the control input of the second controlled frequency divider, the output of which is connected to the C-input of the D-trigger, while the output of the first controlled frequency divider is connected to the input of the triangular pulse shaper, the first output which is connected to the clock input of the second controlled frequency divider, and the second output is the output of a digital generator [1].

A well-known digital variable frequency oscillator allows you to generate a signal without phase break with two frequency values and with a modulation index D=0.5.

However, the generated signal is a stepwise approximation of a triangular wave. Therefore, its spectrum does not decrease rapidly enough with increasing frequency detuning. Therefore, the disadvantage of the known digital variable frequency oscillator is the insufficient spectral efficiency of the generated signals.

In addition, in the known device, the operation cycles of the first and second controlled frequency dividers are not synchronized, therefore the initial phase of the generated triangular oscillation is not uniquely determined. In this case, an additional disadvantage of the known digital variable frequency oscillator is the low accuracy of the output signal.

.The technical result consists in increasing the spectral efficiency of the generated signals due to the formation of MFM signals with initial phases

.

An additional technical result is to increase the accuracy of the formation of cosine oscillations within one symbol of the generated MFM signals.

Disclosure of the essence of the invention

To achieve the specified technical result in a digital generator of variable frequency oscillations, containing the first controlled frequency divider, the clock input of which is the clock input of the digital generator, the second controlled frequency divider and a D-trigger, the D-input of which is the information input of the digital generator, the direct output D- trigger is connected to the control input of the first controlled frequency divider, the inverse output of the D-flip-flop is connected to the control input of the second controlled frequency divider, the output of which is connected to the C-input of the D-flip-flop, the initial phase decoder and the digital-to-analog cosine oscillation generator are introduced, the output of which is the output of the digital generator, while the clock input of the digital-to-analog cosine oscillation generator is connected to the clock input of the second controlled frequency divider and to the output of the first controlled frequency divider, the output of the current phase value of the digital-to-analog cosine oscillation generator is connected to the information input of the initial phase decoder, the synchronization input of which connected to the C-input of the D-flip-flop, to the reset input of the first controlled frequency divider and to the output of the second controlled frequency divider, while the output of the initial phase decoder is connected to the reset input of the digital-to-analog cosine generator.

The proposed digital generator of variable frequency oscillations provides an increase in the accuracy of the formation of MFM signals with increased spectral efficiency.

The proposed digital generator of variable frequency oscillations can be implemented using known functional elements.

Brief description of the drawings

In FIG. 1 shows a block diagram of the proposed digital variable frequency oscillator.

In FIG. 2 shows a comparison table of numerical sequences at the input and output of a digital-to-analog cosine oscillation generator, as well as the values of the MFM signal generated at its output.

In FIG. 3 shows timing diagrams explaining the operation of the proposed digital variable frequency oscillator.

The digital digital oscillator of variable frequency (Fig. 1) contains a clock input 1, an information input 2, a D-trigger 3, a first controlled frequency divider 4, a second controlled frequency divider 5, a decoder 6 of the initial phase, a digital-to-analog generator 7 of a cosine waveform, and exit 8.

The clock input 1 of the device is connected to the clock input of the first controlled frequency divider 4. The information input 2 of the device is connected to the D-input of the D-flip-flop 3, the C-input of which is connected to the output of the second controlled frequency divider 5, as well as to the reset input of the first controlled frequency divider 4 and to the sync input of the decoder 6 of the initial phase. The direct output of the D-flip-flop 3 is connected to the control input of the first controlled frequency divider 4, the inverse output of the D-flip-flop 3 is connected to the control input of the second controlled frequency divider 5. The output of the first controlled frequency divider 4 is connected to the clock input of the second controlled frequency divider 5 and to the clock input of the digital-to-analog generator 7 of the cosine waveform. The output of the current value of the phase of the digital-to-analog generator 7 cosine waveform is connected to the information input of the decoder 6 of the initial phase, the output of which is connected to the reset input of the digital-to-analog generator 7 cosine waveform. The output of the digital-to-analog cosine waveform generator 7 is the output of a digital generator. Implementation of the invention

и функционирует следующим образом.The proposed digital digital oscillator of variable frequency generates MFM signals with initial phases

and functions as follows.

подают на тактовый вход первого управляемого делителя 4 частоты.From the clock input 1 of the device, clock pulses (Fig. 3.6) with a repetition rate

served on the clock input of the first controlled divider 4 frequency.

где L - число уровней L аппроксимирующего ступенчатого напряжения (на фиг. 3 для удобства отображения сигналов приняты значения L=8, n=2).From the information input 2 of the device, the input information signal (Fig. 3.6) is fed to the D-input of the D-flip-flop 3, on the direct and inverse outputs of which modulating signals are received (Fig. 3, c) and (Fig. 3, d), the boundaries of the symbols of which are determined by the clock pulses arriving at its C-input (Fig. 3, f) with a repetition rate

where L is the number of levels L of the approximating step voltage (in Fig. 3, for the convenience of displaying the signals, the values L=8, n=2 are taken).

The generated synchronous modulating signals (Fig. 3, c) and (Fig. 3, d) are fed from the direct and inverse outputs of the D-flip-flop 3 to the control inputs, respectively, of the first controlled frequency divider 4 and the second controlled frequency divider 5.

The first controlled frequency divider 4 has a variable value n or (n+1) of the frequency division factor depending on the value of "1" or "O" of the synchronous modulating signal (Fig. 3, c) supplied to its control input.

или

в зависимости от значения модулирующего сигнала (фиг. 3,в), поступающего на его управляющий вход.At the output of the first controlled frequency divider 4, clock pulses are received (Fig. 3, e) with repetition rates

or

depending on the value of the modulating signal (Fig. 3, c), coming to its control input.

или

подают на тактовые входы второго управляемого делителя 5 частоты и цифро-аналогового генератора 7 косинусного колебания.Clock pulses (Fig. 3e) with repetition rates

or

served on the clock inputs of the second controlled divider 5 frequency and digital-to-analog generator 7 cosine oscillations.

The second controlled frequency divider 5 has a variable value L(n+1) or Ln of the frequency division factor depending on the value of "1" or "0" of the synchronous modulating signal (Fig. 3d) supplied to its control input.

определяющих границы символов выходного МЧМ сигнала (фиг. 3,ж).At the output of the second controlled frequency divider 5, for any values of "1" or "O" of the synchronous modulating signal (Fig. 3, d), a sequence (Fig. 3, f) of clock pulses with a repetition rate is formed

defining the boundaries of the symbols of the output MFM signal (Fig. 3g).

также подают с выхода второго управляемого делителя 5 частоты на вход сброса первого управляемого делителя 4 частоты, что обеспечивает синхронное формирование на его выходе в течение длительности

символа L(n+1) или Ln тактовых импульсов (фиг. 3,д) в зависимости от значения «1» или «О» управляющего сигнала (фиг. 3,в).Clock pulses (Fig. 3, f) with a repetition rate

also served from the output of the second controlled frequency divider 5 to the reset input of the first controlled frequency divider 4, which ensures synchronous formation at its output for a duration

symbol L(n+1) or Ln clock pulses (Fig. 3, e) depending on the value of "1" or "O" of the control signal (Fig. 3, c).

Clock pulses (Fig. 3, e) from the output of the first controlled frequency divider 4 are fed to the clock input of the digital-analog generator 7 of cosine oscillation, the initial state of the counting cycle of which at the symbol boundaries of the generated MFM signal is controlled by pulses (Fig. 3, i) control applied to the reset input of the digital-to-analog generator 7 cosine oscillations.

начальной фазы на границах символов необходимо обеспечить синхронизацию цикла счета цифро-аналогового генератора 7 косинусного колебания с синхроимпульсами (фиг. 3,е). С этой целью сигналы (фиг. 3,з) с выхода текущего значения фазы цифро-аналогового генератора 7 косинусного колебания подают на информационный вход дешифратора 6 начальной фазы.For the formation of MFM signals with given values

of the initial phase at the boundaries of the symbols, it is necessary to ensure synchronization of the counting cycle of the digital-analog generator 7 of the cosine oscillation with clock pulses (Fig. 3, e). For this purpose, the signals (Fig. 3, h) from the output of the current phase value of the digital-to-analog generator 7 cosine oscillations are fed to the information input of the decoder 6 of the initial phase.

If the signals (Fig. 3, h) have the values "1111" or "0111", then the decoder 6 of the initial phase does not pass the clock pulses to its output (Fig. 3, f). If the signals (Fig. 3, h) have other values, then the decoder 6 of the initial phase passes the clock pulses to its output (Fig. 3, f). As a result, at the output of the decoder 6 of the initial phase, control pulses are received - a signal (Fig. 3, i), which takes the value either "0" (no clock pulse), if the signals (see Fig. 3, h) at its inputs have the values " 1111" or "0111", or the value "1" (there is a clock pulse) in other cases. Pulses (Fig. 3, i) control, providing the initial state of the counting cycle of the digital-analog generator 7 cosine oscillations, served at the reset input of the latter.

The digital-analog generator 7 of the cosine oscillation generates an approximation of the cosine oscillation in the form of a step function (Fig. 3g). If there is a symbol "0" at the information input of the device, the output signal of the digital-analog generator 7 of the cosine oscillation contains n half-periods of the approximating oscillation for the duration of one symbol, and if there is a symbol "1" at the information input of the device - (n + 1) a half-period of the approximating oscillation for the duration of one character.

The number of levels L of the approximating step voltage for the duration of one half-cycle determines the accuracy of the approximation of the output sinusoidal oscillation and is set in advance when choosing the type of DAC. Calculations show that at L=2 (approximation of cosine oscillations by rectangular pulses of the "meander" type) the approximation error is approximately П≈10%. As L increases, the accuracy of the approximation sharply increases. So, at L=4 P≈2.5%, and at L=8 P≈0.6%). A further increase in the value of L does not provide a significant increase in the accuracy of the formation of the output signal.

представлена на фиг. 2.Correspondence table of multi-bit codes with the number of binary digits equal to log ₂ 2L (with a value of L=8, the number of digits is equal to D=4), as well as the values of the cosine oscillation of the MFM signal generated at the output of the digital-analog generator 7 (Fig. 3, g) with initial phase

shown in Fig. 2.

As a result, at the output of the digital-to-analog generator 7 of the cosine oscillation, an MFM signal 19 is obtained (Fig. 3, g) without a phase break with the initial phases

Thus, a positive technical result is achieved - an increase in the spectral efficiency of the generated signals in comparison with the prototype, the generated signal of which is a stepwise approximation of a triangular oscillation.

An additional technical result is to increase the accuracy of the formation of cosine oscillations within one symbol of the generated MFM signals.

Information sources

1. Digital variable frequency oscillator: Aut. certificate USSR No. 1636998 / A. V. Anoshkin, D. I. Kupriychuk, O. V. Firsov; publ. 03/23/1991, Bull. No. 11. - 4 s.

Claims (1)

A digital generator of variable frequency oscillations, containing the first controlled frequency divider, the clock input of which is the clock input of the digital generator, the second controlled frequency divider and the D-flip-flop, the D-input of which is the information input of the digital generator, the direct output of the D-flip-flop is connected to the control input of the first controlled frequency divider, the inverse output of the D-trigger is connected to the control input of the second controlled frequency divider, the output of which is connected to the C-input of the D-trigger, characterized in that an initial phase decoder and a digital-to-analog cosine oscillation generator are introduced, the output of which is the output of a digital generator, while the clock input of the digital-to-analog cosine oscillation generator is connected to the clock input of the second controlled frequency divider and to the output of the first controlled frequency divider, the output of the current phase value of the digital-to-analog cosine oscillation generator is connected to the information input of the initial phase decoder, the synchronization input of which is connected to the C-input of the D-flip-flop , with the reset input of the first controlled frequency divider and with the output of the second controlled frequency divider, while the output of the initial phase decoder is connected to the reset input of the digital-to-analog cosine generator.

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