FR2796466A1 - METHOD FOR ASSOCIATING RESULTS OF RADIOGONIMETRIC TRACKING DEVICES - Google Patents

Abstract

The signals picked up in the time-frequency range are sent to a device for segmenting associated regions in the time-frequency space, information is sent concerning the region marked as associated, the coordinates of the region examined are extended by means of l extension of data areas contiguous to this region, certain measurement cells are removed and the others are combined in the form of a fingerprint (1), then the fingerprints generated are compared (2) and processed (6, 7) and correlated (8) for establishing (11) an association with a tracking result or for a rejection (12). Application in particular to direction finding systems.

Description

The invention relates to a method for clearly associating results.

direction finding

  as part of a tracking interrogation in a dis-

  positive broadband and multichannel direction finding that signals are sent in frequency-frequency space after successful exploitation of the azimuth angle of the different values

  sampling signal received, to a seg-

  ment which segments the associated regions in time-frequency space and sends them to a downstream processing unit. An emitter of electromagnetic radiation (in the ranges of high HF frequencies, very high VHF frequencies, ultra high UHF frequencies) can be located by direction finding of at least two

  different suitable locations. For effective control

  cace of a range of frequencies, it is advisable to use

  multi-channel radio direction finding devices

  multiple. In the case of radio direction finding devices

  multi-channel metric, the real-time bandwidth is significantly greater than the signal bandwidth so that in general a large number of neighboring channels are received simultaneously at regular time intervals using a filter bank. In this way, several zones (in a number corresponding to the number of direction finding receivers) of discrete data (sampling values) in time-frequency space are obtained. During a first processing step, each of the multi-channel direction finding devices of a localization network determines, in general with formation of the average over several measurement instants, the signal level and the azimuth angle relative to each output channel. In general, the multi-channel direction finding device then combines several of these discrete pairs of data on the basis of averaging and / or filtering over time, to form a single measurement cell, which again reveals in time-frequency space, an area of discrete measurement cells. This area made up of measurement cells is subjected, during a next step, to segmentation, the role of which is to identify contiguous regions in this area from measurement cells and to mark them as being associated. The algorithmic nature of this segmentation process is designed so that even regions, which are separated due to signal interruptions or signal interference, are again

  united to form a common region in time-space

  frequencies and are marked as being associated with a single emission. During this processing process, the segmentation device simultaneously determines the average signal level (MS), the signal level inside the channel in the case where no measurable signal is present (in general the signal level of the background noise) (RS) and the azimuth angle (MA) of the measuring cells

  within a region marked as associated.

  If direction finding is performed using multi-channel direction finding devices, which perform synchronous scanning in a control area, then direction finding (segmented) data, which is synchronous and is marked as associated, is present then in real time for

  the entire control region.

  For locations, it is necessary to provide a data transmission (data link) between the radiogoniometric locations. In general, the capacity of the data link is not sufficient to perform real-time tracking calculations in connection with all the tracking results of the multi-channel direction finding devices performing the scanning. Due to insufficient data link capacity, segmented device results

  of direction-finding systems are temporarily stored -

  ment at the location locations and the direction finding values, for which a location calculation must be performed (interrogation tracking),

are then questioned.

  There is a problem that the direction finding devices are located in different locations and therefore possibly receive at the same time, and at the same frequency, signals from different transmitters. Therefore, it may happen that the regions segmented in association with a transmission in time-frequency space appear different at the level of the different multi-channel direction finding devices of the location network. In order to be able to obtain a net association of emissions, one can use in the context of the current state of the art essentially three types

of solutions indicated below.

  1.) Direct comparison (acoustic or by correlation) of the segmented signal parts, which are present at the time of the determination of the reference value. A drawback results from the fact that the interrogation is then carried out for a frequency known only at the time of interrogation. In order for the signal sections, which are necessary for comparison, to then be available, it would be necessary to digitize and temporarily store the entire frequency range at

control (for example 30 MHz).

  2.) Net association of emissions segmented according to criteria such as bandwidth, center frequency and time. These criteria are however not sufficient essentially in signal scenarios

  dense or in radio direction finding locations

sticks together.

  3.) Classification of the sections of segmented signals using characteristics determined from the tracking data, such as for example the type of modulation or the baud rate of the transmission. However, this condition requires the temporary storage of direction finding data from the entire range of frequencies to be checked (as is also the case for type of solution 1 described above) or else all signals received in the range of frequencies to be checked, at the time of reception; Similarly, in this case, it is necessary to provide, in addition to the multi-channel direction finding device, a multi-channel receiver and a high computing power to carry out the parallel classification of the

segmented signals.

  The object of the invention is to obtain an association

  net of results of radio direction finding devices

  metric without the need to provide a multi-channel receiver, and in the case of as low an expense as possible for the storage of data on site for the transmission of data between the different tracking stations in a location network in a large band. The problem is solved in accordance with the invention by the fact that, during the further processing of the regions marked by the segmentation device, reference is made to the measurement cells generated in the multi-channel direction finding devices. The information, which is determined by the segmentation device and relates to the regions associated with a

  emission, are exploited in time-frequency space.

  The information necessary for the process, which is delivered by the segmentation device, includes: a) the coordinates, in time-frequency space, of the regions determined to be associated, b) their average signal level (MS), c ) their mean azimuth angle (MA), d) the level, present at the time of measurement, of the background noise (RS),

  e) as well as the coordinates, in time-fre-

  quences, for the segmented regions, which adjoin the

region to examine.

  The coordinates of the region to be examined are

  enlarged, inside the radio tracking device

  multi-channel niometric, by adding the data areas adjoining this region. Using these newly obtained extended region coordinates, measurement cells are then selected from the data field originally produced in the multi-channel direction finding device. Then from the measurement cells thus selected are extracted from the measurement cells, the signal level of which is lower than a threshold value which is set to a value which can be freely chosen, generally above the channel background noise. medium / medium background noise (RS). Preferably this threshold value is adjusted to a signal level which is 3 dB higher than the RS background noise. According to the desired use or the present scenario, this threshold value can however be a different value, and one can even imagine, for example for signals with spread spectrum, to fix the value of

  threshold below RS background noise.

  The other measurement cells are brought together for further processing to form what is called an imprint. For each elementary measurement cell of this footprint, the deviation (Dazimuth) of the associated azimuth value from the mean azimuth value (MA) of

  the segmented region is calculated and stored.

  More specifically, the invention relates to a method for clearly associating results of

  radio direction finding in the context of an

  tracking station in a radio tracking device

  wideband and multi-channel niometric, according to which the signals are sent, in time-frequency space, after successful exploitation of the azimuth angle of the different sampling values of the received signal, to a signaling device segmentation which segments the associated regions in time-frequency space and sends them to a downstream processing unit, characterized in that - with the sending of the segmented regions by the segmentation device, also information concerning the region marked as being associated are sent, these

  information including coordinates in space time-

  frequencies of the regions determined to be associated, their average signal level, their average azimuth angle, the level, present at the measurement instant, of the background noise as well as the time-frequency space coordinates for segmented regions, which adjoin the region to be examined, - that the coordinates of the region to be examined are enlarged by means of an increase in the data areas adjoining this region examined, - that measurement cells are selected using these extended region coordinates, newly obtained from the data area initially produced in the multi-channel direction finding device, - a sort is made among the measurement cells thus selected to extract those whose signal level is below a threshold value which is set at a freely selectable value, usually greater than the average channel noise / average background noise , - that the other measurement cells are brought together for the following processing, so as to form what is called an imprint, - that for each elementary measurement cell of this imprint, the deviation of the associated azimuthal value with respect to the average azimuthal value of the segmented region is calculated, - that the fingerprints generated are then compared, in a central processing unit, using methods of comparison with a model and of a regulation unit based

on a screenplay.

  In a particular embodiment of the method according to the invention, one can also imagine, at this stage of the procedure, to remove from the imprint, regions present in the imprint and whose coordinates are occupied, after the information delivered by the segmentation device, by other broadcasts. For the continuation of the treatment, it is however here necessary to send jointly the information concerning the coordinates of the withdrawn region, with the information of the imprint given that the zone, which appears under the effect of the withdrawal, of the contour outside the imprint cannot be used for comparisons (the outline in this area of the imprint obviously no longer corresponds to the actual outline of the initial issue). The fingerprints thus generated, which can be

  associated with the various radio tracking devices

  multi-channel niometric, are then compared,

  in a central operating unit, using procedures

  comparison dice to a model and a regulatory unit based on a scenario. In accordance with the mechanism of the types of modulation known by the acronyms FSK, PSK, AM, FM and voice signals, fingerprints have typical patterns. In the ideal reception case (no interference and no signal interruption (fading)), the fingerprints which depend on the direction-finding receivers have approximately the same model. However you have to hold on

  account of the fact that the structure of the footprint depends for-

  frequency resolution and behavior

  during the scanning process performed by the different

  radio direction finding receptors. It is also possible to be able to shift the boundaries of the fingerprints on the basis of low signal levels and a signal may be interrupted by propagation according to

multiple paths (fading).

  The comparison of fingerprints is essentially based on

  tially on an exploitation of the structure of the footprint, the intensity of the signal level and the deviations of the azimuthal values (Dazimut) inside the footprint. When assessing the quality of a

  comparison of two fingerprints, we examine two hypo-

  theses: 1. Do the two fingerprints come from the same program? In other words: are they identical in terms of their outline and structure?

  2. Or do the two fingerprints come from

  are we different? If one of these two hypotheses can be confirmed with high probability, the indications

  provided by the comparison are then of good quality.

  In the event that the uncertainty of evaluation concerning these assumptions increases, the quality of the comparison also decreases. To evaluate these hypotheses, we examine, in the context of the identification of the model, during the comparison of the imprint, on the one hand the contours of the imprints as well as, their interior structure varying over time. This identification of the model, which is based on algorithms generally known and used during image processing, is combined with a regulation unit based on a scenario and which contains information concerning the forms of appearance of the

  different types of modulation in the time range-

  frequencies. To explain in more detail the cooperation of the algorithm for identifying a model with the regulatory unit based on the scenario, three examples are given below: 1.) We can obtain a hypothesis test with a large information capacity when the contours of two

  footprints completely coincide.

  2.) During transmissions, which last longer than the time interval examined, the contours cannot

  be defined correctly at the beginning and at the end of the transmission

  if we. This is why only a hypothesis test is possible on the basis of the lateral edges (contours) of the impressions, which can only lead to quality indications.

  lower for example in the case of PSK signals.

  3.) If an imprint has, in determined zones of its limits, high azimuth deviations D_azimut, during a comparison with another imprint within the framework of a test of hypotheses concerning the coincidence of the two zones, these zones do not absolutely coincide. However the indication which results from the hypothesis test, can present only a low quality. To obtain a high quality indication, it would be necessary, in this case, to compare other areas (with a low

  value D_azimut) of the contours of the two imprints.

  The parties, which coincide with good qua-

  Then, compared fingerprints can then be identified.

  tified as net radiogonio-

  metric and be associated with that result.

  In a particularly advantageous manner, the

  process according to the invention is also suitable for the combination

  net ciation of direction finding results from a disturbed emission. The method takes advantage of the fact that disturbances generally arrive in a direction other than that of the signal to be located properly speaking. Since the fingerprints are however formed, as described above, by means of the azimuth information inside the direction finding values, in the case where disturbances

  the footprints of the different arrangements appear

  multi-channel direction finding devices

  have different structures and different contours

  famous. From the results of the identification in relation to a model and the knowledge drawn from the unit

  of scenario-based regulation for the non-per-

  turbid, one can determine the degree of reduction, by interference, of the strength of the information capacity provided by a comparison. We can indicate this by way of example with reference to the following 3 cases: 1. If in the case of one of the two fingerprints to be compared of a PSK transmission, the zone on the left of the contour and the other zone on the right of the contour cannot be identified due to interference, the strength of indication of a comparison based purely on the identification of a model, would be greatly limited. However, the additional evaluation of characteristics in accordance with rules based on a scenario allows a combination of direction finding results with high quality when, in the case indicated above, with the

  two fingerprints, the initial and final instants coincide.

  2. If in the case of the two fingerprints, which are associated with an amplitude modulated voice signal, respectively the left edge of the contour cannot be identified due to interference, but the right edges of the contour match, can perform a combination of results

  of direction finding with high quality.

  The above scenarios or the combination of model identification procedures with scenario-based control units are only an example

  of choice from an imaginable multiplicity of possibilities.

  An advantageous mode of implementation of the invention

  tion results from the possibility of performing a correlation of the short-term spectra of the original data which can be associated with a fingerprint. This functionality extends

  due is advantageous especially in cases where no association

  Clear ciation of fingerprints to direction finding results is not possible or in which the result of a hypothesis test presents only a

  poor quality (description of the criteria of the two tests

  hypotheses: see above). Thus an example is that where a transmission lasts longer than the time range occupied by the imprint. In this case, the segmented program has no net start or net end. This leads, as has been described, especially in the case of PSK signals, only to indications of reduced quality. (This is contrary to vocal signals, with which the contours of the lateral edges already lead to high quality indications, insofar as these

  contours are clearly distinguished in the received signal).

  However, thanks to the correlation of the short-term spectra of the original data that can be associated with these "cut" emissions, in particular it is however possible to still obtain a clear association of results of

direction finding.

  Advantageously, fuzzy logic is used as a basis when establishing the scenario on the basis of a setting unit which is used when comparing the fingerprints which depend on the receivers of

location.

  For the implementation of the process according to the invention

  On the one hand, it is possible to establish in one location

  particular cement within the location network, a central processing unit to which all multi-channel direction finding devices send their data. However, we can also imagine integrating this unit

  operating center directly in one of the

  multi-channel direction finding, which reduces the necessary data transfer. In connection with data transfer, we can also imagine the transmission of data in two different profiles: 1.) Once the segmentation device has determined the contours for the area to be examined and these contour coordinates have been extended around contiguous areas, the corresponding data area is divided from the existing area constituted by measurement cells, inside the multi-channel direction finding device and are transmitted in common with

  information delivered by the segmentation device.

  2.) On the other hand, it is also conceivable to reduce the necessary transmission bandwidth, to produce the fingerprints already inside the multi-channel direction finding device and to transmit only these fingerprints to the central processing unit d 'exploitation.

  In all cases, however, there is the possibility

  ability for the central processing unit to be able to access, for the calculation of short-term spectra, the original data, which are not filtered and whose average is not formed, of the tracking devices

  multi-channel direction finding or power request

der this data.

  According to another characteristic of the invention, before comparing the footprints with each other, the regions which are present in the footprint and whose coordinates are occupied after the information delivered by the segmentation device, by other transmissions, must be removed from the fingerprint and the contact information for the area removed must be

  be transmitted with the information relating to the imprint.

  According to another characteristic of the invention, in the cases where the comparison of the footprints does not lead to a clear association with the results of the radio direction finding device, the regions, which are occupied by several footprints in common in space time frequencies, are corrected with respect to each other using brief spectra of their data

associated origin.

  According to another characteristic of the invention, the regulation unit based on a scenario is based on

fuzzy logic.

  According to another characteristic of the invention,

  the comparison of fingerprints is performed in a dispo-

  central operating location, to which all of the different

  Many multi-channel direction finding devices in a location network transmit their data. According to another characteristic of the invention, the central operating device used to compare the fingerprints is integrated into one of the multi-channel direction finding devices of a location network and that the other channel direction finding devices multiples transmit their

  data to this operating device.

  According to another characteristic of the invention, the data from the direction-finding devices

  multichannel are transmitted directly, joint-

  ment with the information delivered by the

  segmentation, in the form of measurement cells available

  operating sitive and the footprints to be associated

  to the different radio direction finding devices

  multi-channel stick are produced in the device

central operating.

  According to another characteristic of the invention, as regards the data transmitted to the central operating device, these are the fingerprints to be associated with the various multi-channel direction finding devices and additional information necessary for their further processing, such as the contour coordinates of the regions removed from the imprint. Other features and advantages of the

  present invention will emerge from the description given

  hereinafter taken with reference to the attached drawings, on the-

  which: - Figure 1 shows possible forms

  appearance of fingerprints associated with different situations

  reception, in the intensity-frequency space and in the time-frequency space; and FIG. 2 illustrates the progress of the method according to the invention during the comparison of the different fingerprints, which can be associated with the different multi-channel direction finding devices, inside the central processing unit.

  The fingerprints produced by the meeting of the

  besides the information concerning the measurement instant, the measurement cells contain the frequency and the deviation from the average azimuth value (D_azimuth) of each of the individual measurement cells, and also a

  information regarding the signal level of these cells.

  This is shown in Figure 1 for four different reception cases. In part a) of the figure, we have

  represented, based on an intensity representation-

  frequencies and a time-frequency representation, a footprint, which corresponds to an undisturbed emission with a frequency spectrum constant over time. Part b) of the figure represents the same signal, but with a signal interruption (called "fading") extends in the time range and in the frequency range. The spurious signal represented by dotted lines in the intensity-frequency representation in part c) of the figure leads to an extension, limited in time, of the bandwidth of the imprint in the time-frequency representation. The imprint area, which must be associated with the spurious signal, is represented by cross-hatching in the time-frequency representation. The temporal expansion of the imprint of the useful signal has also been correspondingly represented under the effect of a spurious emission as in part d) of the image, as can be imagined (area comprising cross hatching). The method according to the invention detects and removes the interference shown in parts b) - d) of the figure and clearly associates the other surfaces with the emissions proper (with oblique hatching). The method is due to the fact that signal interferences generally act in different ways at the different locations of the different multi-channel direction finding devices. Using a comparison with a model in combination with a scenario-based control unit, we can then identify coincident zones among the zones which depend on the tracking receivers, and associate them with a

tracking result.

  FIG. 2 shows the course of the procedure inside the central processing unit, which ultimately leads for each

  fingerprint (part of a broadcast detected) to an association

  tion (in 11) to a tracking result or to a rejection (in 12) of the corresponding reception data. The fingerprints 1, which can be associated with the different locating receivers, are compared during the first processing step 2, by means of standardized methods for identifying models and regulating units based on scenarios. If an indication concerning the agreement with a high quality can be obtained (in 3), the emission corresponding to the imprint is associated with an imprint. If it is established that there is no agreement (in 4), this zone is rejected with regard to its possibility of association with a tracking result. In the case where an indication concerning a possible concordance can only be obtained with a low quality (in 5), the zones occupied jointly by several fingerprints are segmented from the fingerprints (in 6) and the short-term spectra are produced (in 7) for these zones. Then the short-term spectra thus obtained are correlated with each other, and areas with a strong correlation (in 9) are associated with a tracking result and areas with a weak correlation (in) related to the possibility of association with a

  tracking results (in 11) are rejected (in 12).

Claims (8)

  1. A method for clearly associating direction finding results as part of a tracking interrogation in a broadband, multi-channel direction finding apparatus, according to which signals are sent, in   time-frequency space, after successful operation   below the azimuth angle of the different sample values   signaling received signal, to a segmentation device   which segments the associated regions in time space-   frequencies and sends them to a downstream processing unit, characterized in that - with the sending of the segmented regions by the segmentation device, also information concerning the region marked as being associated is sent, these   information including coordinates in space time-   frequencies of the regions determined to be associated, their mean signal level (MS), their mean azimuth angle (MA), the level, present at the time of measurement, of the   background (RS) as well as the coordinates in time space-   frequencies for segmented regions, which adjoin the region to be examined, - that the coordinates of the region to be examined are widened by means of an increase in the data areas adjoining this region examined, - that measurement cells are selected using these newly obtained extended region coordinates from the data area initially produced in the multi-channel direction finding device, - a sort is made among the measurement cells thus selected to extract those whose signal level is lower than a threshold value which is fixed at a freely selectable value, in general higher than the average channel noise / average background noise (RS), - that the other measurement cells are brought together for the following processing, so to form what is called an imprint, - that for each elementary measurement cell of this   footprint, the deviation (D_azimuth) from the associated azimuth value   ciée compared to the average azimuthal value (MA) of the segmented region is calculated, - that the fingerprints generated are then compared, in a central processing unit, using methods of comparison to a model and a regulation unit based on a screenplay.   2. Method according to claim 1, characterized in that before the comparison (in 2) of the imprints (1) between them, the regions, which are present in the imprint and whose coordinates are occupied after the information delivered by the segmentation device, by other emissions, must be removed from the footprint and that information concerning the coordinates of the withdrawn region must be transmitted   with information relating to the imprint.   3. Method according to claim 2, characterized in that in the cases where the comparison (in 2) of the fingerprints does not lead to a clear association with the results of the direction-finding device, the regions which are occupied by several fingerprints in common in time-frequency space, are corrected (in 8) with respect to each other using spectra of   brief duration of their associated original data.   4. Method according to any one of the claims   1 to 3, characterized in that the control unit   based on a scenario is based on fuzzy logic.   5. Method according to any one of the claims   1 to 4, characterized in that the comparison (in 2) of the imprints (1) is carried out in a central device   operating system, to which all of the various   multi-channel direction finder tifs of a   location network transmit their data.   6. Method according to any one of the claims   1 to 5, characterized in that the central device   operating system for comparing fingerprints is integrated   in one of the radio direction finding devices   multi-channel locator network and that the other multi-channel direction finding devices transmit their data to this operating device.   7. Method according to either of the claims   5 and 6, characterized in that the available data   multi-channel direction finding devices   are transmitted directly, jointly with the information   Mations delivered by the segmentation device, in the form of measuring cells to the operating device and the fingerprints to be associated with the various multi-channel direction finding devices are produced in the central operating device.   8. Method according to any one of the claims   1 to 7, characterized in that as regards the data transmitted to the central processing device, these are the fingerprints to be associated with the various multi-channel direction finding devices and the additional information necessary for their processing as the coordinates of   outline of regions removed from the imprint.