RU2796219C1 - Device for determining direction finding parameters of narrow-band radio signals - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: invention can be used, in particular, for processing radio signals and determining the direction-finding parameters of narrow-band radio signals. The device for determining the direction-finding parameters of narrow-band radio signals for their transmission to users additionally comprises a phase-locked loop of reference frequencies. The narrow-band signal reception unit is multichannel. Each channel of the narrow-band signal reception unit consists of a series-connected analogue-to-digital converter (ADC), a useful narrow-band complex signal detection module, a spectral analysis data accumulation module, a dynamic threshold determination module, a data stream storage module, a digital quadrature generator, a module for determining phase differences between by the received narrow-band signal and quadrature channels of the digital generator and the module for determining the parameters of narrow-band complex signals.

EFFECT: increased accuracy of determining the direction-finding parameters of signals in the conditions of receiving a narrow-band useful signal in the presence of interference with significant negative values of the signal/noise level, in particular when determining the carrier frequency with an accuracy of units of kilohertz, determining the values of phase shifts between signals in N receiving channels to determine the angular coordinates.

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Description

The invention relates to radio engineering and can be used, in particular, for processing radio signals and determining the direction-finding parameters of narrow-band radio signals.

Known patent RU2562796C1 "Radio receiver with continuous automatic adjustment of susceptibility", published 09/10/2015. The device can be used to create radio facilities with a programmable architecture with digital signal processing under the influence of blocking signals with a dynamically changing level and a priori parameter uncertainty to ensure stable radio communication in a complex interference environment. Disadvantages of the known device:

- the device determines the frequency parameters in the Fast Fourier Transform (FFT) block, but is unable to determine the type and amount of frequency deviation for narrowband frequency modulated and frequency shifted signals, the number of hops and the type of narrowband phase code keyed signals;

- the device does not allow to determine the values of phase shifts between the signals to determine the angular coordinates of radiation sources.

Known patent RU2715057C1 "Correlation-phase direction finder", published on February 25, 2020, adopted as a prototype. The direction finder contains two antennas, two high-frequency RF units, two demodulators, two spectrum analyzers, a spectrum comparison unit, two memory devices, a control panel, a code generation unit, two matched filters that provide at their outputs the formation of cross-correlation functions between the input phase-shift keyed signal and the code contained in them, and the measure of the delay between the maxima of the cross-correlation functions.

Prototype Disadvantages:

- using a known direction finder, it is possible to determine only the angular coordinates of radio signals with known coding laws, i.e. it is impossible to determine signal parameters and process signals with a priori unknown coding laws;

- the known direction finder contains only two receiving channels, which does not allow for the implementation of a multi-base phase direction finder to eliminate the ambiguity in determining the angular coordinates in a wide band of operating frequencies;

- the well-known direction finder is designed to process signals only from sources of phase-shift keyed signals, i.e. it does not assume processing of frequency-modulated and frequency-shift keyed signals.

The technical result of the claimed invention is to increase the accuracy of determining the direction-finding parameters of signals in the conditions of receiving a narrow-band useful signal in the presence of interference with significant negative signal-to-noise levels, in particular when determining the carrier frequency with an accuracy of units of kilohertz, determining the values of phase shifts between signals in N receiving channels to determine the angular coordinates.

To achieve a technical result, in a device for determining the direction finding parameters of received narrow-band radio signals for transmitting them to users, containing a block for receiving narrow-band signals, a module for determining the parameters of narrow-band complex signals, a module for transmitting direction-finding parameters, an additional phase-locked loop of reference frequencies is introduced, and the block for receiving narrow-band signals is made multichannel , each channel of which consists of a serially connected analog-to-digital converter (ADC), a module for detecting a useful narrow-band complex signal, made in the form of a fast Fourier transform (FFT) block, a spectral analysis data accumulation module, a dynamic threshold determination module, a data stream storage module, a digital quadrature generator, a module for determining the phase differences between the received narrow-band signal and the quadrature channels of the digital generator, and a module for determining the parameters of narrow-band complex signals, the outputs of which are connected to the information transmission module, and in each channel of the receiving unit, the sampling input of the ADC is connected to the corresponding output of the phase-locked loop of the reference frequencies, the output of the ADC is connected to the information inputs of the module for determining the phase differences, the output of the FFT block is connected to the input of the module for determining the parameters of complex signals, and the output of the module for determining the phase differences between the channels is connected to the information transmission module.

In addition, the device is made on a very large integrated circuit (VLSI).

In addition, in the device, the module for determining the phase differences between the channels is made in the form of two multipliers, the outputs of which are connected through the corresponding low-pass filters to an arithmetic logic unit (ALU) configured to determine the value of the phase difference between the received signal in the i-th channel and reference frequency of the digital quadrature oscillator.

The invention is illustrated in the drawing.

The figure shows a diagram of a device for determining the direction-finding parameters of narrow-band radio signals and the following designations are introduced:

1. Block phase locked reference frequency (PLL) (sampling frequency).

2. Analog-to-digital converter (ADC).

3. A module for detecting a useful narrow-band complex signal that implements a fast Fourier transform (FFT).

4. Module for data accumulation of spectral analysis.

5. Module for determining the dynamic threshold.

6. Data flow storage module.

7. Digital quadrature generator.

8. Module for determining the phase differences between the channels and the reference signal of the generator.

9. Module for determining the direction-finding parameters of complex signals.

10. Information transfer module.

Processing of narrow-band signals from sources on the Earth is carried out in an information processing unit using VLSI, which implements a detection module, a module for accumulating spectral analysis data to increase the signal/noise level, as well as a module for determining the frequency and phase parameters of complex signals.

The device includes: a module for setting the reference frequency (sampling frequency) PLL (1), implemented on VLSI, an ADC module (2), a module for detecting a useful narrow-band signal that implements the FFT (3), a module for accumulating spectral analysis data to increase the signal / noise in a given band (4), a module for determining the dynamic threshold (5), a data stream storage module (6), a digital quadrature generator with the ability to set the frequency of the generated signal (7), a module for determining the phase differences between the channels and the reference signal of the generator (8) , a module for determining the parameters of complex signals (9), an information transmission module (10).

The device works as follows.

When the power is turned on, the device boots up and starts up. The clock frequency generator sends a signal to the PLL implemented on VLSI in order to adjust the ADC clock frequency to the values specified in the configuration.

From the external synchronization device, a command is issued to start monitoring and parameters are transmitted to configure the internal modules from the device.

At the reference frequency (with the sampling rate obtained from the reference signal from the PLL), the analog-to-digital conversion of the input signal is performed, the results of which are streamed at the sampling rate of the ADC to the detection module, which implements the FFT of a given size in a pipelined mode.

The FFT results are fed to the input of the data accumulation module (4), in which the signal spectrum data is accumulated for a specified number of cycles. In the data accumulation module (4), the accumulated spectrum values are summed for each frequency, which makes it possible to increase the signal/noise level by amplifying the useful signal and suppressing the noise spectrum values.

From the output of the data accumulation module (4), the resulting spectrum is fed to the input of the dynamic threshold determination module (5), in which the threshold value of the spectrum is determined, the excess of which means the presence of a useful signal. The threshold value is defined as the sum of two-thirds of the maximum signal value in the spectrum and the average value of the spectrum in a given frequency band.

When a useful signal is detected in the module for determining the dynamic threshold (5), the signal is sent to the data stream storage module. The data stream storage module can accumulate information (detection time and signal frequency with an accuracy of units of kilohertz) about the detected signals. If information about the detected signal has appeared in the data stream storage module, then the frequency value is sent to the digital quadrature generator (7) and the command to send a signal from the generator outputs (7) to the multiplier in the module (8) for determining the phase differences between the channels and the generator reference signal .

The device has 2N channels of multiplication to implement convolution of signals from N input channels. The multiplication results are fed to a low-pass filter implemented with the help of adders, in which the signal is accumulated at the time specified when configuring the internal modules.

The accumulated values are fed to the input of the arithmetic logic unit (ALU), in which the value of the phase difference between the signal in the i-th channel and the reference signal common to all receiving channels is determined. The ALU implements the arctg function with a complement of up to 2π, based on an iterative method of reducing direct calculations of complex functions to performing simple addition and shift operations to optimize the expended VLSI resources.

From the output of the module for determining the phase differences, the values of the phase shift in N channels are sent to the information transmission module for further processing in the block for determining the angular coordinates of the radio emission source. Also, the information transmission module receives the accumulation start time corresponding to the signal detection time, and the signal frequency.

Simultaneously with the accumulation of the signal in the module for determining the phase differences (8), the results of convolution in the streaming mode are sent to the module for determining the parameters of complex signals (9), in which a statistical analysis of the nature of the signal convolution in a given channel is carried out. Together with the analysis of the signal convolution results, the data on the signal spectrum obtained earlier in the detection module are processed.

Data on the detected type of modulation, the number and magnitude of changes in the signal parameters, as well as the time of their change are received from the output of the module for determining the parameters of complex signals to the information transmission module.

The use of VLSI with the indicated modules as part of the proposed device provides, in comparison with the prototype of the proposed device, the detection of a useful narrow-band signal at significant negative signal-to-noise levels, the determination of the carrier frequency with an accuracy of units of kilohertz, the determination of the values of phase shifts between signals in N receiving channels to determine angular coordinates of radiation sources in a wide band of operating frequencies of the system in real time, regardless of the type of input signal.

The claimed device also makes it possible to determine the type and magnitude of the frequency deviation for narrowband frequency modulated and frequency shift keyed signals, the number of hops and the type of narrowband phase code keyed signals.

Claims (3)

1. A device for determining the direction-finding parameters of narrow-band radio signals for transmitting them to users, containing a block for receiving narrow-band signals, a module for determining the parameters of narrow-band complex signals, a module for transmitting parameters, characterized in that a phase-locked loop of reference frequencies is additionally introduced, and the block for receiving narrow-band signals is made multi-channel, each channel of which consists of a serially connected analog-to-digital converter (ADC), a module for detecting a useful narrow-band complex signal, made in the form of a fast Fourier transform (FFT) block, a spectral analysis data accumulation module, a dynamic threshold determination module, a data stream storage module, a digital a quadrature generator, a module for determining the phase differences between the received narrow-band signal and the quadrature channels of the digital generator, and a module for determining the parameters of narrow-band complex signals, the outputs of which are connected to the information transmission module, and in each channel of the receiving unit, the sampling input of the ADC is connected to the corresponding output of the phase-locked loop of the reference frequencies , the output of the ADC is connected to the information inputs of the module for determining the phase differences, the output of the FFT block is connected to the input of the module for determining the parameters of complex signals, and the output of the module for determining the phase differences between the channels is connected to the information transmission module. 2. The device according to claim. 1, characterized in that it is made on a very large integrated circuit (VLSI). 3. The device according to claim 1, characterized in that the module for determining the phase differences between the channels is made in the form of two multipliers, the outputs of which are connected through the corresponding low-pass filters to an arithmetic logic unit (ALU) configured to determine the value of the phase difference between the received signal in the i-th channel and the reference frequency of the digital quadrature generator.

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