RU2776973C1 - Frequency shift keying signal conditioner - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: invention relates to radio engineering and can be used to generate signals with minimum frequency shift keying and controlled intersymbol interference at two symbol intervals in discrete information transmission systems. A signal generator with continuous frequency shift keying contains a generator (1) of elementary signals, a delay element (2), a switch (3), a device (4) for selecting a signal path, a synchronizer (5) and a delay device (6). The input of the device is the input of the synchronizer 5, the sync input of which is connected to the sync output of the elementary signal former (1), the output signal bus of which is connected to the input signal bus of the switch (3). The output of the switch (3) is the output of the device, and its input control bus is connected to the output bus of the signal path selection device (4) directly and to the second control input of the signal path selection device (4) through the delay device (6). The output of the synchronizer (5) is connected to the information input of the device (4) for selecting the signal path directly and to the first control input of the device (4) for selecting the signal path through the delay element (2).

EFFECT: increasing the spectral efficiency of the generated signals due to the formation of signals with minimal frequency shift keying and controlled intersymbol interference at two symbol intervals (2MFM).

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Description

The technical field to which the invention belongs

The invention relates to radio engineering and can be used to generate signals with minimal frequency shift keying and controlled intersymbol interference in two symbol intervals in discrete information transmission systems.

State of the art

Closest to the present invention is a signal generator with continuous frequency shift keying (frequency manipulator) containing an elementary signal generator (first and second master oscillators, the outputs of which form the output signal bus of the elementary signal generator and are connected to the first and second inputs of the mixer, the output of which is connected to the input frequency doubler, the output of which is the sync output of the elementary signal generator), the sync output of which is connected to the sync input of the synchronizer, the input of which is the input of the device, the switch (frequency switch), the output of which is the output of the device, the delay element and the converter of elementary signals (the first and second phase switches, information inputs and outputs of which form, respectively, the input and output signal buses of the elementary signal converter, the control inputs of the first and second phase switches are connected to the outputs of the first and second three, respectively. ggers, the counting inputs of which are connected to the outputs of the first and second AND elements, respectively, the first input of the second AND element is connected through the inverter to the first input of the first AND element and is the first control input of the elementary signal converter, the second control input of which is connected to the second inputs of the first and second, respectively elements AND), the input signal bus of which is connected to the output signal bus of the elementary signal generator, and the output signal bus is connected to the input signal bus (with the first and second information inputs of the frequency switch) of the switch, the control input of which is connected to the first control input of the elementary signal converter and to the output of the synchronizer, the synchronization input of which is connected through the delay element with the second control input of the converter of elementary signals [1].

Known signal generator with continuous frequency shift keying (frequency manipulator) allows you to generate MFM signals with minimal frequency shift keying (frequency-shift keyed signals with a modulation index D=0.5 and without phase discontinuity). However, the spectrum of MFM signals does not decrease fast enough with increasing frequency detuning. Therefore, a disadvantage of the known signal generator with continuous frequency shift keying is the insufficient spectral efficiency of the generated signals.

The technical result consists in increasing the spectral efficiency of the generated signals by generating signals with minimal frequency shift keying and controlled intersymbol interference over two symbol intervals (2MFM).

Disclosure of the essence of the invention

To achieve the specified technical result, a signal generator with continuous frequency shift keying, containing a delay element, an elementary signal generator, the sync output of which is connected to the sync input of the synchronizer, the input of which is the input of the device, as well as the switch, the output of which is the output of the device, has a delay device and a selection device signal path, the information input of which is connected to the output of the synchronizer and to the input of the delay element, the output of which is connected to the first control input of the signal path selection device, the output bus of which is connected to the input control bus of the switch and to the input bus of the delay device, the output bus of which is connected to the second to the control input of the device for selecting the signal path, while the output signal bus of the elementary signal generator is connected to the input signal bus of the switch.

The proposed signal generator with continuous frequency shift keying provides an increase in the spectral efficiency of the generated signals due to the formation of 2MFM signals.

The proposed signal generator with continuous frequency shift keying can be implemented using known functional elements.

Brief description of the drawings

In FIG. 1 shows a block diagram of the proposed signal generator with continuous frequency shift keying.

In FIG. 2 shows the decoding table of the signal path selector 4 when generating 2FMK signals.

In FIG. Figure 3 shows signal transition diagrams of signals with continuous frequency shift keying: MFM signals (Fig. 3, a) and 2MFM signals (Fig. 3, b), as well as timing diagrams of the corresponding elementary signals (Fig. 3, c).

In FIG. Figure 4 shows the sequence of transmitted logical symbols (Figure 4, a), the timing diagram of the generated 2MFM signal (Figure 4, b) and its signal path (Figure 4, c).

In FIG. 5 shows the spectra of signals with continuous frequency shift keying: in Fig. 5a - spectrum of the MFM signal, in Fig. 5b - spectrum of the 2MFM signal.

The signal generator with continuous frequency shift keying contains a chip generator 1, a delay element 2, a switch 3, a signal path selector 4, a synchronizer 5 and a delay device 6 (see Fig. 1).

The input of the device is the input of the synchronizer 5, the sync input of which is connected to the sync output of the elementary signal generator 1, the output signal bus of which is connected to the input signal bus of the switch 3. The output of the switch 3 is the output of the device, and its input control bus is connected to the output bus of the device 4 for selecting the signal path directly and with the second control input of the signal path selection device 4 via the delay device 6 . The output of the synchronizer 5 is connected to the information input of the device 4 select signal path directly and to the first control input of the device 4 select signal path through the delay element 2.

Implementation of the invention

The proposed signal generator with continuous frequency shift keying generates signals with minimum frequency shift keying and controlled intersymbol interference over two symbol intervals and operates as follows.

Shaper 1 elementary signals on any k-th symbol interval with duration Will generate twelve elementary signals

- амплитуда и начальная фаза сигнала на границе к-го символа,where A and

- amplitude and initial phase of the signal at the boundary of the k-th symbol,

и ƒ_н - частоты элементарных сигналов.

and ƒ _n - frequencies of elementary signals.

Chips S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, S11 and S12 are shown in FIG. 3, c.

When forming an MFM signal without controlled intersymbol interference, only eight of the indicated elementary signals are used: S2, S3, S5, S6, S8, S9, 11 and S12. In this case, in accordance with the diagram of signal transitions of the MFM signals (see Fig. 3, a), the transmission of the logical symbol "1" corresponds to elementary signals S2, S6, S9 and S12 with a frequency of ƒ ₁ with initial phases, respectively, 0, π/2, π and -π/2. The transmission of the logical symbol "0" corresponds to elementary signals S3, S5, S8 and S11 with a frequency ƒ ₀ with initial phases of 0, π/2, π and -π/2, respectively.

When forming a 2MFM signal with controlled intersymbol interference on two symbol intervals, all twelve of these elementary signals are used. At the same time, in accordance with the diagram of signal transitions of 2MFM signals (see Fig. 3, b), the transmission of the logical symbol "1" corresponds to elementary signals S2, S6, S9 and S12 with a frequency of ƒ ₁ with initial phases, respectively, 0, π/2, π and -π/2. The transmission of the logical symbol "0" corresponds to elementary signals S3, S5, S8 and S11 with a frequency ƒ ₀ with initial phases of 0, π/2, π and -π/2, respectively. The alternation of logical symbols "1" and "0" in any order corresponds to elementary signals S1, S4, S7 and S10 with a frequency ƒ _n with initial phases, respectively, 0, π/2, π and -π/2.

The elementary signals S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, S11 and S12 are supplied from the output signal bus of the elementary signal generator 1 to the input signal bus of the switch 3. The switch 3 outputs one of the elementary signals so as to obtain a 2MFM signal without phase discontinuity. To do this, the switch 3 is controlled by the signal path selection device 4, which generates in accordance with the decoding table (see Fig. 2) and outputs a control signal from its output bus to the input control bus of the switch 3. The first and second columns of the decoding table show the values of the previous control signal symbol, respectively, in decimal and binary representation forms. The third column of the decoding table shows the values of the previous symbol of the video signal only for those cases when an elementary signal with a frequency of ƒ _n was transmitted in the previous symbol interval (in other cases, the value of the previous symbol of the video signal does not affect the value of the current symbol of the control signal). The fourth and fifth columns of the decoding table show the values of the current symbol of the control signal, respectively, in decimal and binary representation forms at a value of "0" of the current symbol of the video signal. In the sixth and seventh columns of the decoding table, the values of the current symbol of the control signal are given in decimal and binary representation forms, respectively, at a value of "1" of the current symbol of the video signal.

The formation of the control signal is carried out as follows. From the sync output of the shaper 1 of the elementary signals to the sync input of the synchronizer 4, sync pulses are received, which provide at the output of the synchronizer 4 a video signal with a duration of T symbol interval, carrying a sequence of transmitted logical symbols (see Fig. 4, a). The video signal from the output of the synchronizer 4 is fed to the information input of the device 4 select signal path directly and to the first control input of the device 4 select signal path through the delay element 2. Therefore, at any k-th symbol interval of duration T, the current symbol "0" or "1" of the video signal arrives at the information input of the signal path selection device 4 (column headings 4-7 of the decoding table in Fig. 2), and its first control input - the previous symbol of the video signal (column 3 of the decoding table in FIG. 2). At the same time, the control signal from the output bus of the signal path selection device 4 is fed through the delay device 6 to the second control input of the signal path selection device 4 . At the same time, at any k-th symbol interval of duration T, the previous control signal symbol (columns 1 and 2 of the decoding table in Fig. 2) is supplied to the second control input of the device 4 for selecting the signal path. As a result, the current symbol of the control signal is formed on the output bus of the device 4 for selecting the signal path at a value of "0" of the current symbol of the video signal (columns 4 and 5 of the decoding table in Fig. 2) or at a value of "1" of the current symbol of the video signal (columns 6 and 7 of the table decoding in Fig. 2). The sequence of symbols at the output of the signal path selector 4 is shown in FIG. 4b. The signaling pathway corresponding to this sequence is depicted in FIG. 4, c.

The symbols of the control signal from the output bus of the device 4 for selecting the signal path are fed to the input control bus of the switch 3.

As a result, at the output of the switch 3, a 2MFM signal is received without a phase break (see Fig. 4, b).

In FIG. Figure 5 shows the spectra of signals with continuous frequency shift keying: MFM signals (see Fig. 5, a) and 2MFM signals generated by the proposed device (see Fig. 5, b). An analysis of these spectra shows that the spectrum of 2MFM signals decreases with increasing frequency detuning faster than the spectrum of MFM signals. Therefore, the proposed CFM signal generator makes it possible to generate 2MFM signals with a more compact spectrum than the spectrum of MFM signals.

This ensures the formation of 2MFM signals with minimal frequency shift keying and controlled intersymbol interference on two symbol intervals. As a result, a positive technical result is achieved - an increase in the spectral efficiency of the generated signals.

Sources of information:

1. Frequency keyer: Aut. certificate USSR No. 604177 / Anoshkin A.V., Gerasimov Yu.S.; publ. 04/25/1978, Bull. No. 15. - 2 s.

Claims (1)

Signal shaper with continuous frequency shift keying, containing a delay element, a generator of elementary signals, the sync output of which is connected to the sync input of the synchronizer, the input of which is the input of the device, as well as the switch, the output of which is the output of the device, characterized in that a delay device and a signal path selection device are introduced , the information input of which is connected to the output of the synchronizer and to the input of the delay element, the output of which is connected to the first control input of the signal path selection device, the output bus of which is connected to the input control bus of the switch and to the input bus of the delay device, the output bus of which is connected to the second control input a device for selecting a signal path, wherein the output signal bus of the elementary signal generator is connected to the input signal bus of the switch.

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