# Method of monitoring

(57) Abstract:

The invention relates to electrical engineering and can be used in solving the problem of hidden determine the characteristics (frequency, azimuth, elevation, range and type of target) set short-term operating transmitters at the same time fall within the current band reception. The method is based on coherent reception and simultaneous registration of multiple frequencies for all databases, educated and support all members of the grid antennas in the reception band of many times greater than the width of the spectrum of the single signal transmitter. Using the Fourier transform, restore complex temporal spectra of the signals from each antenna and the power spectrum signal of the reference antenna, which comparison with a threshold to choose the frequency at which calculates the complex amplitude of the detected signals by convolution of complex-conjugate of the reference spectra and the remaining antennas. On the basis of the complex amplitude of each detected signal using the combined spatial Fourier transforms, different phase shift in elevation, restore complex two-dimensional angular range, the module of which is determined by the azimuthal and stuffy and define an inclined distance D to the transmitter aerial targets by the formula D = H/sin, where H is a known altitude targets. A special case of the method based on the fact that, using the signal auxiliary antenna as the frequency-time marker (marker), two-dimensional angular range selectively restore time and frequency. The technical result consists in increasing the efficiency and speed control. 1 Il. The invention relates to electrical engineering and can be used for passive monitoring in solving the problem secretive determine the characteristics (frequency, azimuth, elevation, range and type of target) set short-term operating transmitters at the same time fall within the current band reception.With the advent and improvement of communication systems, location, identification, and other using signals with a low probability of intercept, i.e. with high temporal stealth (short packet, the stepwise change of frequency) have problems of their control.The known method of monitoring using radio frequency holography /1/. This method is based on digital recording of a radio frequency hologram radio signals received antenna array and recovery Pomodoro spectrum determines the direction of arrival of the main and paratragedy rays. This method does not provide a direction finding of radio signals from several transmitters simultaneously falling within the band of the reception.There is a method of monitoring and /2/, providing the definition of the azimuthal bearing and frequency of signals from several transmitters simultaneously falling within the band, and adopted for the prototype.According to this method:1. Coherently accept and register synchronously multi-frequency time signals x

_{n}(t), where n is the number of antenna element for all databases, reference educated n= 0 and all members of the grid antennas n = 1...N, in the band of reception, many times longer than the width of the spectrum of the single signal transmitter;

2. Synchronously convert the signals x

_{n}(t) into digital signals x

_{n}(i) where i is the number of the time reference signal;

3. Restore complex temporal spectra of the signals from each antenna where F

_{t}{...} - operator Fourier transform in time and f - number of the frequency reference, that is, the input signals are divided into frequency sub-bands;

4. Compute the power spectrum signal of the reference antenna

5. Compare the power spectrum with a threshold, and selects the frequency f at which the detected signals of the transmitters;

6. Porn at selected frequencies

7. Using the complex amplitude of the discrete Fourier transform compute the azimuthal angular range of the signal at frequency f;

8. Determine the azimuth bearings

_{m}transmitters on the square of the module of the complex angular spectrum.From the above description it follows that the prototype method, providing the selection and direction finding of radio signals in the azimuth plane, has no selectivity in elevation and, therefore, does not retrieve all available in the received signal information.At the same time, knowledge of the elevation angle of the radiation source allows to increase the sensitivity of the radio signal due to a consistent angle signal and provides separation of targets on the ground and air.Moreover, in many cases air target moving at known altitudes, which allows using the measurement of the elevation angle transmitter goals, to obtain an estimate of its removal from the station direction finding. Estimation of slant range together with azimuth bearing clearly describe the location of the target in space and significantly increase the efficiency of the control.In addition, the method prototype the following inherent contradiction. On one side is obnarujenia and direction finding of signals with a low probability of interception. At the same time described earlier, the most time-consuming steps 6 - 8 processing signals, the method of the prototype is performed for each detected in the reception band of the signal. This means that for a fixed performance devices processing the more in-band signals, the longer the total loop direction finding, i.e. below the speed control. Given a constant trend of increasing the number of radiating money and improve instant download of the frequency range, it becomes clear the need to address this contradiction.Thus, the prototype method does not provide:

retrieve all available in the received signal information, including measurement of the elevation angle transmitter, the division targets on land and air, assessment of the distance to aerial targets;

high speed inspection in conditions of high load range of frequencies.The problem solved by the invention is the increased efficiency and speed control.The problem is solved in that in the method of monitoring, including coherent reception and simultaneous registration of multiple frequencies for all databases, educated and support all members of the grid antennas, in-band reception,obrazovanie Fourier complex temporal spectra of the signals from each antenna and power spectrum signal of the reference antenna, the comparison with the threshold selects the frequency at which calculates the complex amplitude of the detected signals by convolution of complex-conjugate of the reference spectra and other antennas, according to the invention on the basis of the complex amplitude of each detected signal using the combined spatial Fourier transforms, different phase shift in elevation, restore complex two-dimensional angular range, the module of which is determined by the azimuth and elevation bearings, and after comparing elevation bearings with a threshold share the transmitters on the ground and air and determine the inclined distance D to the transmitter aerial targets by the formula D = H/sin, where H is a known altitude targets.Possible special case of the method in which it is advisable to signal an auxiliary antenna is used as the frequency-time marker (the marker) and selectively in time and frequency restored the two-dimensional angular range.The drawing shows a structural diagram of a device that implements the proposed method.According to the proposed method:

1. Coherently accept and synchronously to the region to which the reference data n=0 and all members of the grid antennas n = 1...N, in the band taking many times longer than the width of the spectrum of the single signal transmitter.2. Synchronously convert the signals x

_{n}(t) into digital signals x

_{n}(i) where i is the number of the time reference signal.3. Restore complex temporal spectra of the signals from each antenna where F

_{t}{...} operator Fourier transform in time and f - number of the frequency reference, that is, the input signals are divided into frequency sub-bands.4. Compute the power spectrum signal of the reference antenna

5. Compare the power spectrum with a threshold and select f - e frequency at which the detected signals of the transmitters, that is, the mark frequency range.6. Compare f-e frequency at which the detected signals of the transmitters, with time-frequency mask is forbidden to accept or not of interest for the control of frequency and time intervals and select signals for subsequent processing.The need of time-frequency masking signals caused by the existence of both frequency and temporal methods of separation channels in modern communication systems, navigation and others.At this stage of the processing at the expense of selectivity input the I in the subsequent steps, characterized by high complexity of processing.7. Calculate the complex amplitude

(1)

each selected signal by a convolution of the complex-conjugate of the reference spectra and the rest of the antenna at the selected frequency f.8. For each frequency f for each value of phase shift in elevation, depending on the index h, where h = 0...Y -1 is the current number of mesh guidance lattice in elevation, a Y - number of nodes in elevation, in which the restored cut of the azimuthal angular spectrum at the frequency f, the complex amplitude of the selected signal is multiplied by the directivity pattern of the n-th antenna element, where m= 0,..., M-1 the current number of mesh angle , and M is the number of mesh points in the corner , and environment function depending on the configuration of the antenna array and for a ring lattice with the following:

< / BR>

where, R is the radius of the grating, the wavelength at the frequency.This stage of processing is a key to retrieve all available in the received signal information. This is ensured through full coordination, as in azimuth and elevation directions phasing with the direction of arrival of the signals.9. Define complex two-dimensional angular spectrum is/BR> 11. Determine the azimuthal

_{m}and elevation

_{h}the bearings on the selected transmitters on the square of the module of the complex angular spectrum

12. Compare the elevation bearings

_{h}threshold and when the threshold is exceeded detect air targets.13. Using bearings in elevation

_{h}determine the slant range D to the selected transmitter aerial targets with known altitude H by the formula D = H/sin

_{h}.

Azimuthal bearing

_{m}and distance D describe the location of a transmitter aerial targets in space.Improving the efficiency and speed control is achieved by:

additional phasing of the received signals in azimuth and recovery of two-dimensional (azimuth and elevation) integrated angular spectrum instead of one-dimensional (azimuth), additional definitions and comparison with a threshold bearings in the elevation plane and use the resulting elevation bearings for evaluation by the calculation formula slant range to the air source is moving at a known height;

the polling frequency and recovery time of two-dimensional angular spectrum signals, purposefully using the result.Thus, for typical values of H = 10 km and

_{h}= 4

^{o}...45

^{o}we find that the measuring range can be solved with acceptable in practice, the distances D= (14...143) km. Availability of assessment a range of up to air object greatly increases the information content and, consequently, the efficiency of radio control.As already noted for its modern and promising direction finders tend expansion band simultaneous reception. The wider the band simultaneous reception, the more signals that you want to restore the angular range and to determine the bearings. On the other hand, the wider the band simultaneous reception, the higher the probability that this band signals that are not of interest for monitoring (for example, TV broadcast transmitters, beacons, tools, connections, and so on). Thus, excluding these signals from the input stream, it is possible to concentrate the resources of the direction finder on the securities signals and thus improve the accuracy of direction finding or maintaining precision to reduce the cycle time of the processing, that is, to increase the speed. Based on experience, it can be considered that the complexity of the exception signals from the input stream, you can equate the complexity of the issue in increments of 0.35

^{o}in the azimuthal sector 360

^{o}and with increments of 1

^{o}elevation sector 90

^{o}requires approximately two 1024-point complex FFT. If we assume that 10 transmitters, both located in the reception band of excluded three, the speed of finding the remaining control transmitters is increased by 25%. In the limiting case, when valuable for control are only emerging radiation, speed, direction finding increased by 90% due to the exclusion from the input stream of signals representing no value for the control.In addition to these advantages simulations using mathematical system MathCAD 7 Professional on the example of the circular antenna array confirmed the possibility of measuring two-dimensional positions in the case where the wavelength of the received radiation, and d is the distance between the elements of the lattice, with the phasing of the signals in elevation. This is equivalent to 10 times the extension of the operating frequency range for a fixed number of antennas in the lattice or a proportional reduction in the number of antennas at a fixed frequency range compared to the prototype.The device (see drawing), which is implemented ¾ elements, connected to the inputs of the switch 4. To the outputs of the antenna system 1 are connected in series: two-channel coherent receiver device 5, dual channel synchronous ADC 6, the first spectrum analyzer based on the fast Fourier transform (FFT) 7, the comparison circuit 8, the transmitter bundle 9, the processor of the discrete Fourier transform 10, the classifier goals and the transmitter range 11. The second input circuit 8 connected storage device is prohibited frequencies and time slots 12, the first input connected directly to the second output of the first spectrum analyzer 7, and the second input device 12 is connected to the third output of the first spectrum analyzer 7 via the inverse FFT device 13. The first signal input of the transmitter bundle 9 is connected to the third output of the first spectrum analyzer 7. The second signal input of the transmitter bundle 9 through the second spectrum analyzer FFT-based 14 is connected to the second output of the ADC 6. With the second input of the processor 10 is connected a storage device weight and environment functions 14.The device operates as follows.Multi-frequency time signals x

_{n}(t) from the reference antenna element (n = 0) of the antenna system input device 5 through the switch 4. The signals x

_{n}(t) coherently transferred to the lower frequency in the receiving device 5 and synchronously converted by the ADC Converter 3 into digital signals x

_{n}(i) where n is the number of antenna element, a i is the number of the time reference signal.In the spectrum analyzer 7 is determined by the complex spectrum of the temporal frequency of the output signal of the reference antenna and the spectrum analyzer 14 - with the outputs of all of the antennas included in the lattice where F

_{t}{...} - operator Fourier transform in time and f - number of the frequency reference, that is, the input signals are divided into frequency sub-bands. In the spectrum analyzer 7 optionally recovering the power spectrum of the reference signals antenna which is compared with a threshold and select f-e frequency at which the detected signals of the transmitters, that is, the mark frequency range. These frequencies are received in the storage device 12. At the same time integrated signals at these frequencies with the third output of the analyzer 7 are received in the inverse FFT device 13. In the device 13 detected signals are converted into the time domain, detected by the amplitude detector and after comparison with a threshold determined by the moments of reception of signals at selected frequencies. Moments popovitsa statistical information about the frequency-time parameters of all signals the observed and the observed in-band reception. In addition, the device 12 can be entered additional information from the operator. Using this information, the device 12 is generated and stored frequency-time mask is prohibited for subsequent signal processing.In the comparison circuit 8 compares the values of the f-th frequency at which the detected signals of the transmitters, and time of reception of signals at these frequencies with time-frequency mask, stored in the storage device 12. In the case of coincidence of the frequencies and the presence of the mask ban time in the transmitter bundle 9 signal prohibiting the processing of data on the frequency and time interval.As previously noted, at this stage of processing input signals substantially shrinks and turns into a stream of valuable for monitoring signals, which is the main condition for improving the speed of direction finding in the subsequent steps.In computer bundle 9 get the complex amplitude of each signal by a convolution of the complex-conjugate of the reference spectra and the remaining antennas selected in the comparison circuit 8 frequencies f.In the processor of the discrete Fourier transform on 10 kaut on stored in the storage device 14 weight function (the pattern of the n-th antenna element) and environment function, depending on the configuration of the antenna array and for a ring lattice has the form (2).After that, the CPU 10 at the selected frequencies and time intervals (that is selective in frequency and time) to restore the complex angular range using two-dimensional Fourier transform by the formula (3).Determine the azimuthal

_{m}and elevation

_{h}the bearings selected transmitters on the unit square complex two-dimensional angular spectrum

In the classifier goals and the transmitter range 11 compare the elevation bearings

_{h}threshold and when it is exceeded, identify air targets, as well as define the inclined distance D to the selected transmitter aerial targets with known altitude H by the formula D = H/sin

_{h}.

Azimuthal bearing

_{m}and distance D describe the location of a transmitter aerial targets in space.Thus, the inventive method of monitoring due to:

evaluation of the slant range to the transmitter aerial targets, moving at a known height;

the polling frequency and recovery time of two-dimensional angular spectrum signals, purposefully selected from the input stream

tent, 3887923, CL G 01 S 5/02, 19752. RU, patent, 2096797, CL G 01 S 3/14, 1996 The method of monitoring, including coherent reception and simultaneous registration of multiple frequencies for all databases, educated and support all members of the grid antennas in the reception band of many times greater than the width of the spectrum of the single signal transmitter, the recovery by using the Fourier transform of the complex temporal spectra of the signals of each of the n-th antenna and the power spectrum signal of the reference antenna are compared with the threshold chosen f-tide frequencies at which the detected signals of the transmitters, characterized in that what you are comparing f-tide frequency and intervals of the existence of the detected signals with time-frequency mask is forbidden to accept or not of interest to control frequency and select signals, which calculates the complex amplitude for each node with the current number h grid guidance lattice in elevation multiply the amplitude of the directional diagram of the n-th antenna

< / BR>

where M is the number of grid nodes in azimuth;

m = O, ... M-1 to the current node number grid azimuth,

and environment function depending on the configuration of the antenna array, and determine dominionist

_{h}the bearings, but after comparing elevation bearings

_{h}threshold share the transmitters on the ground and air and determine the inclined distance D to the transmitter aerial targets by the formula D = H/sin

_{h}where H is a known altitude targets.

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