RU2498515C1 - Digital device for generating spectrally efficient signals - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: digital device for generating spectrally efficient signals has an analogue-to-digital converter, the control input of which is connected to the output of a clock unit, a first multiplexer, a parallel register, an adder and a first control unit, a digital-to-analogue converter, two multiplexers, two serial-parallel multi-bit registers, second and third control units, a feedback control unit and a low-pass filter. Multi-bit signal outputs of the first multiplexer are connected to signal inputs of the first serial-parallel multi-bit register, having groups of multi-bit outputs. The register is connected to signal inputs of the second multiplexer, the control inputs of which are connected to outputs of the first control unit, and the outputs are connected to the first group of inputs of the adder, the outputs of which are connected to inputs of the parallel register. The clock unit is connected to the first serial-parallel multi-bit register, the first control unit, the parallel register, the digital-to-analogue converter and the input of the feedback control unit. The first output of the feedback control unit is connected to the control input of the parallel register, its second output is connected to the control input of the second serial-parallel multi-bit register, the third and fourth outputs are connected to inputs of the second and third control units, respectively. Outputs of the third control unit are connected to control inputs of the first multiplexer, the first signal inputs of which are connected to outputs of the analogue-to-digital converter, and the second signal inputs are connected to outputs of the third multiplexer, the groups of multi-bit signal inputs of which are connected to multi-bit outputs of the second serial-parallel multi-bit register. Inputs of the register are simultaneously connected to outputs of the parallel register, the second group of inputs of the adder and the inputs of the digital-to-analogue converter, and the output is connected to the input of the low-pass filter, the output of which is the output of the digital device for generating spectrally efficient signals.

EFFECT: high-speed operation when generating spectrally efficient signals, high security of transmitted information.

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Description

The invention relates to communication technology and can be used in data transmission systems over the air to generate signals limited in spectrum.

A device known as “Signal conditioner” [A.S. SU No. 1598198]. The signal generator comprises a pulse generator, a counter, memory blocks, a pulse distributor, signal conditioning blocks, low-pass filters, analog multipliers, an adder, a harmonic signal generator, a phase shifter, a delay register, a decoder, and a logical multiplier. The disadvantage of this device is the inability to generate signals with a limited frequency spectrum with a high information speed and to be able to restructure the waveform in the process of transmitting information.

A device known as “Digital matched filter” [A.S. SU No. Г815796] The digital matched filter contains an analog-to-digital filter, a shift register, a multiplexer, read-only memory, a counter, an adder, a parallel register, a synchronization unit, and a comparison unit. However, when using the device for generating spectrally effective signals, there is no possibility of restructuring the waveform in the process of transmitting information.

The closest is the "Digital Consistent Filter", adopted as a prototype. [A.S. SU No. 944077]. The filter contains P programmable memory devices 1-i - 1-P, each of which consists of a programmer and a multiplexer, a binary counter, an analog-to-digital converter, a digital multiplier, a memory device, control units, an adder, a synchronization unit, a parallel register and a comparison unit .

The first disadvantage of the prototype is the low speed of the device during the formation or processing of spectrally effective signals with complex laws of change of the envelope of the signals. The second disadvantage of the prototype is the impossibility of tuning the impulse response of the digital matched filter in the process of signal transmission.

The objective of the invention is to increase the speed in the formation of spectrally effective signals, as well as increasing the degree of protection of transmitted information.

To solve this problem, a digital device for the formation of spectrally effective signals is proposed. The device includes an analog-to-digital converter, the control input of which is connected to the output of the synchronization unit, a first multiplexer, a parallel register, an adder and a first control unit, a digital-to-analog converter, two multiplexers, two series-parallel multi-bit registers, a second and third control unit, a block feedback control, low pass filter. The signal multi-bit outputs of the first multiplexer are connected to the signal inputs of the first series-parallel multi-bit register having groups of multi-bit outputs. The register is connected to the signal inputs of the second multiplexer, in which the control inputs are connected to the outputs of the first control unit, and its outputs are connected to the first group of inputs of the adder, the outputs of which are connected to the inputs of the parallel register. The synchronization unit is connected to the first serial-parallel multi-bit register, the first control unit, the parallel register, a digital-to-analog converter and the input of the feedback control unit. The first output of the feedback control unit is connected to the control input of the parallel register, its second output to the control input of the second series-parallel multi-bit register, the third and fourth outputs are connected respectively to the inputs of the second and third control units. The outputs of the third control unit are connected to the control inputs of the first multiplexer, in which the first signal inputs are connected to the outputs of the analog-to-digital converter, and the second signal inputs are connected to the outputs of the third multiplexer, in which the groups of multi-bit signal inputs are connected to the multi-bit outputs of the second series-parallel multi-bit register . The inputs of the register are connected simultaneously with the outputs of the parallel register, the second group of inputs of the adder, and the inputs of the digital-to-analog converter, and its output is connected to the input of a low-pass filter, the output of which is the output of a digital device for generating spectrally effective signals.

The first series-parallel multi-bit register, the second multiplexer, the third control unit, the adder, the synchronization unit, the parallel register, as well as the feedback circuit formed by the feedback control unit, the second series-parallel multi-bit register, the third multiplexer, the second and third control units form Digitally matched filter, which underlies the operation of the device for the formation of spectrally effective signals.

The introduction of feedback allows you to generate an arbitrary impulse response and repeatedly repeat the operation of convolution of the input signal and the impulse response of a digital matched filter. This together leads to a smoothing of the input signal shape and, as a result, firstly, to an increase in the decay rate of out-of-band emissions and, secondly, to a decrease in the occupied frequency band. An increase in the decay rate is due to rounding of the waveform, and a decrease in the frequency band is due to an increase in the duration of the signals.

Such a change in the waveform may be necessary to increase the degree of information protection from unauthorized radio interception of messages. The transmitted signals must have the ability to change the shape of the envelope sequence with a certain frequency automatically, in the process of operation of information transmission and reception devices.

The digital matched filter operation procedure can be described by the expression:

- выборочные значения выходного сигнала на выходе цифрового согласованного фильтр в форме q-разрядных чисел; g^(p)(iΔt) - выборочные значения импульсного отклика цифрового согласованного фильтра в форме p-разрядных чисел;

- выборочные значения входного сигнала в форме n-разрядных чисел; N - число выборочных значений на длительности Т импульсного отклика цифрового согласованного фильтра; Δt - интервал дискретизации, равный T/N.Where

- sample values of the output signal at the output of a digital matched filter in the form of q-bit numbers; g ^(p) (iΔt) - sample values of the impulse response of a digital matched filter in the form of p-bit numbers;

- sample values of the input signal in the form of n-bit numbers; N is the number of sampled values over the duration T of the pulse response of the digital matched filter; Δt is the sampling interval equal to T / N.

The above mathematical confirmation of the operation of the matched filter is valid for rectangular video signals, but arbitrary signals can be used. If the filter has, for example, an impulse response in the form of a rectangular video pulse of unit amplitude, then

g ^(p) (iΔt) = 1

In this case, the operation procedure of the digital matched filter is greatly simplified, namely, the selective values of the output voltage will be determined by the following expressions:

k = 0

k = 1

k = 2

... ...

k = N-2

k = N-1

Based on these expressions, the filter operation procedure can be performed without using a programmable memory device and a memory device. This will increase the performance of the matched filter and the entire device as a whole.

An increase in the degree of protection of information from unauthorized reception is achieved by dynamically changing the shape of the signals during the transmission of information. A dynamic change in the waveform is achieved by changing the number of convolution operations of the input signal and the impulse response of the digital matched filter. This procedure occurs in the device feedback loop. In this case, in the process of transmitting a sequence of signals, their shape will change. Considering that the law of changing the waveform is known only to the receiving side, with unauthorized reception it will be impossible to reliably receive information. This is especially important in multi-channel wireless information transfer systems.

Thus, the distinguishing features are necessary and essential for the implementation of the task.

A digital device for generating spectrally effective signals (FIG. 1) comprises an analog-to-digital converter 1, a first multiplexer 2, a third control unit 3, a feedback control unit 4, a first series-parallel multi-bit register 5, a second multiplexer 6, a third multiplexer 7, a second serial-parallel multi-bit register 8, a second control unit 9, a first control unit 10, an adder 11, a synchronization unit 12, a parallel register 13, a digital-to-analog converter 14, a low-pass filter 15.

A continuous signal is fed to the information input of the analog-to-digital converter 1 (ADC), the control input of which is connected to the output of the synchronization unit 12. At the n outputs of the ADC, a sample value of the amplitude of the received signal is generated as an n-bit binary number. The number of quantization levels M of the sample value of the amplitude of the input signal is determined by the expression M = 2 ⁿ . This sequence goes to the first group of inputs of the first multiplexer 2. Passing without changes (at the first moment there is no signal on the second group of inputs of multiplexer 2), the signal goes to the input of the first series-parallel multi-bit register 5. This first series-parallel multi-bit register acts as a multi-bit delay lines in a digital matched filter. For S _O (kΔt) voltage digital convolution is necessary to organize read sample values of the signal output from the first serial-parallel multi-bit register that is carried by the second multiplexer, and their summation by the adder 11 and the register 13 parallel.

From the output of the parallel register 13, sample values of the output signal of the matched filter via the feedback line are fed to the input of the second serial-parallel multi-bit register 8.

The device operates as follows. First step. A square wave signal (video pulse) is input to the ADC, a triangular wave signal is generated in digital form (in the form of codes) at the output of parallel register 13, which coincides with the type of response of the matched filter to the input signal in the form of a square video pulse. In this case, the duration of this signal is equal to twice the duration of a rectangular video pulse. This signal in the form of codes is fed to the second serial-parallel multi-bit register 8, and then to the third multiplexer 7, the operation of which is controlled by the feedback control unit 4 and the second control unit 9. The same signal in the form of codes is fed to the second group of inputs of the first multiplexer 2 The operation of this multiplexer is controlled by the third control unit 3. Using this control unit, the signal modes from the ADC output and from the outputs of the third multiplexer 7 are switched. Second step. In the second operation, the convolution of the input signal and the pulse response of the digital matched filter at the outputs of the parallel register 13 will generate a signal that matches the convolution of a triangular video pulse of duration 2T and the pulse response of a matched filter of duration T. The signal duration at the outputs of the parallel register 13 will be 3T. Third step. In the execution mode of the third operation, the convolution of the input signal and the pulse response of the digital matched filter at the outputs of the parallel register 13, a signal will be generated in the form matching the convolution of the pulse response of a matched filter of duration 3T and the pulse response of a matched filter of duration 2T. The signal duration at the outputs of the parallel register 13 will be 4T. Fourth step. In the mode of performing the fourth operation of convolution of the input signal and the pulse response of the digital matched filter at the outputs of the parallel register 13, a signal will be generated in the form matching the convolution of the pulse response of a matched filter of 4T duration and the pulse response of a matched filter of 3T duration. The signal duration at the outputs of the parallel register 13 will be 5T. Then the signal goes to the q inputs of the DAC 14, the output of which is formed by a continuous voltage, and then to the low-pass filter 15, which is the output of the device. The operation of the DAC is controlled by the synchronization unit 12.

Thus, the digital device can operate without the use of programmable storage device and storage device available in the prototype. This will increase the speed in connection with the exception of the write / read operation by the storage device and increase the degree of information protection from unauthorized reception due to the dynamic change in the type of signals during transmission, which is achieved by introducing a tunable feedback circuit

Claims (1)

A digital device for generating spectrally effective signals, including an analog-to-digital converter, the input of which is connected to the output of the synchronization unit, a first multiplexer, a parallel register, an adder and a first control unit, characterized in that the device further comprises a digital-to-analog converter, two multiplexers, two in series parallel multi-bit register, second and third control units, feedback control unit, low-pass filter, and multi-bit signal the outputs of the first multiplexer are connected to the signal inputs of the first series-parallel multi-bit register, which has groups of multi-bit outputs connected to the signal inputs of the second multiplexer, whose control inputs are connected to the outputs of the first control unit, and its outputs are connected to the first group of inputs of the adder, the outputs of which are connected to the inputs of the parallel register, the synchronization unit is connected to an analog-to-digital converter, the first series-parallel multi-bit by an register, the first control unit, the parallel register, the digital-to-analog converter and the input of the feedback control unit, the first output of the feedback control unit is connected to the control input of the parallel register, its second output is with the control input of the second series-parallel multi-bit register, the third and fourth outputs are connected respectively with the inputs of the second and third control units, the outputs of the third control unit are connected to the control inputs of the first multiplexer, which the first signal inputs are connected to the outputs of the analog-to-digital converter, and the second signal inputs are connected to the outputs of the third multiplexer, in which the groups of multi-bit signal inputs are connected to the multi-bit outputs of the second series-parallel multi-bit register, the inputs of which, in turn, are connected simultaneously with the outputs parallel register, the second group of inputs of the adder, the inputs of the digital-to-analog converter, and its output is connected to the input of the low-pass filter, the output of which th is the output of the digital forming apparatus spectrally efficient signal.