DE19637843A1 - Aeroplane identification method using secondary surveillance radar - Google Patents

Abstract

The method involves forming a correlation constant kx for a undisturbed reference pulse (Px) of a radar response telegram. The telegram responses to a radar request pulse and includes an identification assigned to an aeroplane. A correlation criterion Kn is formed to all further pulses (Pn) of the response telegram, whereby n is the number of the pulse within the response telegram and 1 <= n <= m where m is the greatest number. Each correlation criterion is checked if the equation Kn=0 is satisfied. If the equation is satisfied the further pulse (Pn) belongs to a response telegram marked by a reference pulse. If the equation is not satisfied the further pulse belongs to a response telegram which is not marked by a reference pulse.

Description

The invention is based on a method for identification tion of a road user according to the generic term of Pa claim 1 and an arrangement for performing the Method according to the preamble of patent claim 8.

The invention is particularly applicable for identification aircraft using a secondary radar (SSR, "Secondary Surveillance Radar") and to monitor the Flight path. For example, in general fixed (monopulse) radar system at least one (Ra dar-) query pulse, in the form of a sum signal, out sends. This is from a (radar) transponder Airplane a (radar) response telegram, at least one contains the identifier identifying the aircraft.  

The response telegram is from the radar system using the Monopulse antenna received and evaluated. This creates a sum and a difference signal. Out of these, at for example the polar coordinates (direction, distance) of the Aircraft are determined. From the sum and the diffe renzsignal can also be present in the video area Response telegram can be determined. Such a reply tele gram contains so-called (start and end) frame pulses, between them a data telegram, in digitized form, is arranged. This contains at least one digital Ken tion assigned to the road user (airplane) is. At least the identifier in one is sent to the radar system connected evaluation unit (processor) determined, so for example, flight path and identifier are symbolized Form on a (radar data) display screen (monitor) adjustable. The method described is known at for example from Stevens, Michael C., Secondary Surveillance Radar, Artech House, Boston and London Internationale Standard book number ISBN 0-89006-292-7, pages 119 to 163.

It can be seen that in the evaluation unit (processor) a reliable evaluation of the available in the video area the response telegram can only take place if an un there is a faulty response telegram. Such disorders can occur, for example, when a query in the pulse several response telegrams from different traffic participants (especially with different identifiers) received and demodulated. A (total) Ant Word telegram arise, which consists of several interlocking there are nested (individual) response telegrams. A sol The process is also used in English-language literature called "garbling" (nesting).  

The invention has for its object a generic ßes procedure indicating a reliable Auswer enables a (total) response telegram, which with is generated by a monopulse receiving arrangement. The he The invention is also based on the task of an arrangement to specify to carry out the procedure.

This problem is solved by the in the characterizing Parts of claims 1 and 8 specified features. Advantageous refinements and or developments are the other claims.

A first advantage of the invention is that in egg ner so-called "garbling" situation, that is, when a (Total) response telegram from several (single) answers legrammen is composed, this (individual) answer tele can be regenerated in such a reliable manner know that their reliable evaluation is possible.

A second advantage is that the process is wide is independent of the type of (standardized) Response telegrams, for example of the so-called fashion, which is currently common for transponders in aviation is.

A third advantage is that analog signals from currently common monopulse receivers can be used NEN, so that existing evaluation facilities in ko most inexpensively retrofittable according to the invention are, because it is preferably only a sum signal as well as the phase signals needed. Such signals arise hen with a variety of currently common monopulse emp catch.  

A fourth advantage is that to perform the Process a so-called vector processor, which in the Sig nal processing is known per se, can be used where by preferably a particularly fast signal processing tion becomes possible.

Further advantages result from the following Be spelling.

The invention is described below with reference to exemplary embodiments play explained in more detail with reference to schematically illustrated figures. Show it

Fig. 1 is a block diagram for generating the required analog signals.

Fig. 2 is a schematic pulse diagram for explaining the invention.

Fig. 1 shows a block diagram of a radar receiver for receiving radar signals by means of a monopulse receiving antenna (ANTENNA). In the block diagram, all essential assemblies are labeled with technical terms in English, which are familiar to a specialist. From the receiving antenna (ANTENNA) a sum signal Σ and a diffe rence signal Δ are generated, which are common in a monopulse radar, for example at the frequency 1090 MHz. These signals are mixed down into a predeterminable intermediate frequency range by means of a local oscillator LO and ultimately fed to two phase detectors PHD1, PHD2. The phase angles γ1, γ2 arise at their outputs in analog form. These are also fed to an adder ADS, at the output of which an analog output signal f (Δ / Σ) is produced. Furthermore, an analog output sum signal Σ is produced on a logarithmic video deo amplifier LV in the intermediate frequency range. Since only these analog output signals are required for the present invention, a further description of FIG. 1 is omitted for the sake of clarity. These output signals can also be generated with equivalent arrangements for receiving and evaluating monopulse signals, which is familiar to a person skilled in the art.

Fig. 2 shows a schematic pulse diagram to explain a so-called "garbling" situation. It is assumed that the transponders of three different road users (aircraft) respond to a (radar) query pulse. The temporal positions of the original pulse responses th Σ ', Σ'',Σ''' are shown in Figs. 2a to 2c Darge, with the time t (abscissa) is shown in clock units. The pulse responses all have the same pulse height and each have a pulse width of one cycle. For reasons of clarity, only the standardized (frame) pulses (F1 = start of a response telegram, F2 = end of a response telegram) and arbitrarily selected standardized pulses C2, C4 are selected. Actually existing further pulses, for example a total of 13 pieces, which lie between the (frame) pulses F1, F2 and which are indicated in FIGS . 2a to 2c by a horizontal dashed line (___), are not required to explain the method , since only a coded information, for example an identifier, is present in these pulses.

Fig. 2d shows a resulting therefrom (total) sum signal corresponding to the sum channel Σ (SUM CHANNEL) and / or the Videover more LV (Fig. 1) is removable. In the (total) sum signal there are clearly identifiable pulses F1 ', C2'',F1''' and F2 ''', all of which have the same (standard) pulse height. In contrast, the pulses marked Fx and Fy have a different pulse height, since these pulses were created by the "garbling" process mentioned at the beginning. Pulse Fx is, for example, from the pulses F2 'and F1'', pulse Fy from the pulses F2''andC4'''. In the (total) sum signal, the pulses Fx, Fy are therefore uncertain and cannot be assigned to a specific pulse response.

Fig. 2e shows the (total) sum signal corresponding to the (total) difference signal is removed the difference channel Σ (DIFFE Řenče CHANNEL) (Fig. 1). Also in this (total) difference signal are pulses marked with Fx, Fy, the pulse height of which does not correspond to the (standard) pulse height.

With the procedure described below it is now in surprisingly possible, even with a "garbling" - Situation a reliable separation of the different To make pulse responses belonging to road users.

The method is based on the knowledge that a (Radar) monopulse receiver in the intermediate frequency range (IF-Be rich) between the (total) sum signal and the (Total) difference signal a phase difference arises. Among other things, this depends on the direction of reception, related to the (radar) receiving antenna in which the road user (transponder) is located. Especially with airplanes there is a very low probability present that two at the time of an interrogation pulse Road users (aircraft) in the same direction of reception must be assigned and this state via a predetermined bar is maintained for a longer period. Furthermore differ from different road users received (transponders) pulse responses in general by their amplitudes. All pulses of a pulse response  of a road user are therefore the amplitude and characterizing the road user Marked phase value. Each pulse can therefore have a vek gate, which is ge by an amplitude and a phase value marks is assigned. Therefore, the Method a vectorial signal processing is carried out, which is explained in more detail below.

In the process, first of all, by means of a so-called frame decoder, which is currently over Lich, the so-called frame pulse pairs (F1, F2) telt. The frame pulse pair spacing is essentially constant and is currently preferably 20.3 microseconds the. In the monopulse evaluation method used up to now with MSSR (Monopuls SSR) they are in a response at for example Σ ', detected information pulses only validated by the fact that for each informat on pulse an associated monopulse value (arctan Δ / Σ) is determined becomes. Then it becomes one with the monopulse value of the two frame pulses F1 or F2 compared. Have the checked (thirteen) information pulses as well as the framework pulse all the same monopulse value, then this pulse se assigned the same answer, here Σ ′.

Since the first answer (Σ ') is undisturbed in this example, a clearly identifiable (identifiable) reference pulse P _x can be selected from it, preferably a (initial) frame pulse, for example F1' from the first answer Σ '( Fig. 2).

It can be checked with the arrangement described with reference to FIG. 1 whether there is a disturbed pulse. Because in this (disturbed) case the condition γ1 ≠ γ2 applies to the phase angles γ1, γ2. If, on the other hand, γ1 = γ2, there is an undisturbed pulse, for example an undisturbed (frame) pulse F1 '. The arctan value (Δ / Σ) is also called the monopulse value. If there is an undisturbed pulse (γ1 = γ2), then γ1 or γ2 is taken as the monopulse value and used as a basis for further evaluation if necessary.

To the reference pulse P _x is now determined by means of a vectorial signal processing (vector processor), which is known per se in data processing, a correlation constant k ' _x according to the formula

so that applies

in which
k ′ _x a constant belonging to the reference pulse (P _x ),
a (sum) vector of the sum signal belonging to the reference pulse (P _x ),
Σ _x an amount corresponding to the (sum) vector,
a (difference) vector of the difference signal belonging to the reference pulse (P _x ),
Δ _x an amount corresponding to the vector and
|| an absolute value of the vector shown between the vertical lines (||)
mean.

The value Σ _x / Δ _x results from the formula Σ _x / Δ _x = cotγ1 = cotγ2. The sign mentioned in the formula (1) depends on the sign of the values Σ _x and / or Δ _x .

This correlation constant k ' _x is now used in a disturbed (overall) response ( Fig. 2d) to validate the next answer, here Σ''. Because in the example shown according to Fig. 2d, the temporal positions of the frame pulses F1 '' and F2 '' of the second response Σ '' can be detected by means of the frame end coder mentioned above, but the two frame pulses F1 '' and F2 '' belonging monopulse values cannot be determined because these frame pulses F1 '', F2 '' occur as disturbed pulses F _x , F _y ( Fig. 2d). With such disturbed (frame) pulses F _x , F _y , no validation per se, which is based on undisturbed frame pulses F1 ′ ′ and F2 ′ ′, of the information pulses lying within these, which belong to the second answer Σ ′ ′, is possible .

In the method, for each pulse P _n , where n is an integer, 1 nm and m means the number of all pulses of the response telegram which occurs after the first response Σ ', that is, according to the (end) frame menpuls F1 ′ (= F _x ), a correlation criterion K _n determined according to the formula

where formula (1 ') corresponds to formula (1) and wherein
a (sum) vector of the sum signal belonging to the pulse (P _n ),
a (difference) vector of the difference signal belonging to the pulse (P _n ),
|| an absolute value of the vector shown between the vertical lines (||)
mean.

According to the formulas (3), (1 ') is now for the (undisturbed) information pulses between F1 ′, F2 ′ (first answer Σ ′), a first correlation criterion K₁ determined according to the formula

and stored as a (reference) correlation criterion K. Formula ( 4 ) corresponds to formula ( 3 ) for the value (index) n = 1.

For each of the first response Σ 'subsequent pulse P _{n of} the response telegram ( Fig. 2d) is now (formula (3)) determined correlation criterion K _n compared to the stored (reference) correlation criterion K₁. Such a comparison is possible, for example, by forming a difference. A predeterminable tolerance range is expediently determined for the comparison result. If the comparison result for a given pulse P _n that can be given is within the tolerance range, it is determined that this pulse P _n belongs to the response telegram identified by the frame pulse, here F1 '', here Σ '' ( Fig. 2b). All of this frame pulse F1 '' belonging (response) pulses P _n are now stored so that a complete response telegram, here corresponding to Σ '', ent. This is limited by start and end pulses, for example F1, F2 pulses. From such a reply message, at least the identifier, and thus the associated road user, is then determined using a known method (decoder). This can then be displayed in a manner known per se on a (data) screen (monitor), so that, for example, a flight path is shown.

The vectors mentioned in the formulas (3), (4), which, also in the following, are identified by an overline (⁻), and constants (scalars) can be determined from signals which can be found in the arrangement according to FIG. 1 , preferably by means of a vectorial data processing system (vector processor). For this, at least the output signals Σ (output of the log. Video amplifier LV) mentioned in FIG. 1 and the phase signals γ1, γ2 (from outputs of the phase detectors PHD1, PHD2) are converted into digital signals by means of analog / digital converters. Furthermore, it is possible, if necessary, to remove the signals represented in mathematical form between the function blocks from the arrangement and to convert them into a digital form.

Formula (3) can be represented in scalar notation speaking the formula

where Σ _n and Δ _n denote the amounts of the vectors and and β _n denotes the angle between the vectors and.

The quantities Δ _n and sinβ _n can be determined according to the formulas

where γ1, γ2 the output signals (phase angles) of the Pha Transmit detectors correspond to PHD1, PHD2.  

As an alternative to the determination according to formula (6), (7), it is possible to summarize and store all occurring variables β _n , Δ _n , γ1, γ2 in tabular form as a so-called "look-up table". The variables β _n and Δ _n are then indirect, depending on the measured phase angles γ1, γ2.

Are now as in this example corresponding to Fig. 2d the pulses of the second answer Σ '' by pulses of a third answer Σ '''disturbed, it being assumed that the third answer Σ''' at least partially (for example, in its last time end ) is not disturbed, a correlation constant k _y '''is determined for the (end) frame pulse F2''' the third response Σ '''according to the formula k _y ''' = ± Σ _y / Δ _y , which speaks the formula (1) ent and where Σ _y , Δ _y mean the sum or difference values belonging to the (final) frame pulse F2 '''.

With this correlation constant k _y ''', which can be derived from the associated cotangent, for all (disturbed and undisturbed) pulses of the second answer Σ''accordingly Fig. 2d, a correlation criterion K _{n is} formed according to the formulas

One can now, as described on the basis of the evaluation of the first answer Σ ', determine the mono pulse value for the (end) frame pulse F2'''. This results in (final) frame pulse F2 ''', which is, for example, at the (telegram) position n = 15 of the third answer Σ''', for the correlation criterion K _n , with n = 15, a value K₁₅ according to of the formula

K₁₅ = | Σ₁₅ - k _y ′ ′ ′ Δ₁₅ | (10).

This value K₁₅ is saved.

For all pulses of the second answer Σ '' are accordingly formula (8), with 1 n 14, the correlation criteria K _n , with 1 n 14, determined and compared with the stored value K₁₅, for example, by the mentioned difference formation. The monopulse value belonging to the second answer Σ '' is derived from an undisturbed pulse of the two th answer Σ '', for example C2 ''.

Correspondingly, the third answer Σ ′ ′ ′ ( FIG. 2d) is validated with the correlation criterion K _n , with 1 n 14, according to the formula

With
k _z ′ ′ = the correlation constant belonging to the second answer Σ ′ ′. As described, an associated monopulse value can be derived from this.

With the method described can be advantageous Way, several response telegrams that go to different ver turn participants belong, separately and then individually be evaluated, which each response telegram is through identified an associated (reference) correlation constant draws. For example, it is possible to combine all of them first pulses belonging to the first reference pulse as the first Ant determine word telegram and save if necessary and this first response telegram then by means of a dif renzbildung from the preferably also stored  Remove (total) response telegram. Remain in that the (residual) response telegram can then be described after the a second response telegram can be determined and so on.

By expanding MSSR with the so-called Mode-S-Ver drive (coding according to the standardized Mode-S Co dierung), the method described is advantageous Way applicable to debugging ("degarbling") of one SSR signal that is disturbed by a mode S signal or vice versa. Furthermore, meh are also advantageous overlap mode S responses after the described process can be evaluated.

The method is advantageously applicable to disturbed (overall) responses ( FIG. 2d), whereby there may be a random disturbance, for example due to interference (multipath propagation), or an intended disturbance, for example due to an interference signal in the so-called main beam.

The invention is not based on the embodiment described examples limited, but analogously to other applications bar, for example on all road users, for example also wise people who use a transponder with indi visual identifier are marked.

Claims (10)

1. A method for identifying a road user using a secondary radar, wherein

• a (radar) interrogation pulse is emitted by a transmitting / receiving station,
• the road user has a (radar) transponder to receive the query pulse and to send a (radar) response telegram which at least contains an identifier assigned to the road user,
• - The response telegram in the transmitting / receiving station is evaluated by means of a (radar) monopulse receiver, so that at least one sum signal and one difference signal arise and
• the response telegram and at least the identifier are determined from the sum and difference signals, characterized in that
• - That a correlation constant k _x ge forms a predefinable undisturbed reference pulse (P _x ) of the response telegram according to the formula in which
  a (sum) vector of the sum signal belonging to the reference pulse (P _x ),
  a (difference) vector of the difference signal belonging to the reference pulse (P _x ) and
  || an absolute value of the vector shown between the vertical lines (||)
  mean,
• - That for all other pulses (P _n ) of the response telegram, where n is the number of the pulse (P _n ) within the response telegram, with 1 nm and m is the largest number, a correlation criterion K _{n is} formed according to the formula in which
  a (sum) vector of the sum signal belonging to the pulse (P _n ),
  a (difference) vector of the difference signal belonging to the pulse (P _n ),
  || an absolute value of the vector shown between the vertical lines (||)
  mean,
• that for each correlation criterion K _{n it is} checked whether the condition K _n = 0 is present,
• - That if the condition K _n equals zero (K _n = 0) it is decided that the further pulse (P _n ) belongs to a response telegram identified by the (reference) pulse (P _x ) and
• - That if the condition K _{n is} not equal to zero (K _n ≠ 0) it is decided that the further pulse (P _n ) belongs to another response telegram not identified by the (reference) pulse (P _x ).

2. A method for identifying a road user according to claim 1, characterized in that

• - That in a total response, which consists of several nested ("garbeld") response telegrams (Σ 'to Σ'''), a correlation constant k _{y is} formed for each response telegram according to the formula in which
  Σ _y the value of the sum signal belonging to an undisturbed (reference) pulse (P _y ) of a predefinable response telegram and
  Δ _y the value of the difference signal belonging to the undisturbed (reference) pulse (P _y ) of a given response telegram
  mean,
• - That for each pulse of the overall response, a correlation criterion K _{n is} formed according to the formula and
• - That it is decided in the presence of different correlation criteria that the associated pulses belong to different response telegrams.

3. A method for identifying a road user according to claim 1 or claim 2, characterized in that

• - That the correlation criterion K _{n is} formed according to the formula in which
  the angle β _{n is} determined from the formula
• - The difference Δ _{x is} determined from the formula
• - γ1 _n , γ2 _{n are} the phase angles belonging to the pulsing.

4. A method for identifying a road user according to claim 3, characterized in that the values Δ _n and β _n as a function of the measured values γ1 _x , γ2 _x , γ1 _n and γ2 _n are stored in tabular form in a table and read out as required. 5. A method for identifying a road user according to one of the preceding claims, characterized in that a frame pulse (F1) contained in the reply telegram is selected as the reference pulse (P _x ). 6. Procedure for identifying a road user according to one of the preceding claims, characterized ge indicates that the frame pulses (F1, F2) in pairs be determined using a frame decoder. 7. A method for identifying a road user according to one of the preceding claims, characterized in that in a (total) response telegram, which is composed of several response telegrams, the response telegrams belonging to predefinable reference pulses (P _x ) are first determined and stored, and that from each response telegram the associated road user is determined by decoding the response telegram. 8. Arrangement for performing the method for identifi cation of a road user according to one of the preceding claims, characterized in that

• - That a receiving arrangement for receiving monopulse Ra darsignalen is available,
• - That in the receiving arrangement from the received mono pulse radar signals at least one sum signal (Σ) is ent and
• - That in the receiving arrangement at least two Phasende tectors (PHD1, PHD2) are available to determine the phase position between the received sum and diffe rence signals.

9. Arrangement to carry out the identification process adornment of a road user according to claim 8, there characterized in that in the receiving arrangement min  at least an analog / digital converter is available for Analog / digital conversion of the sum signal (Σ) and / or that generated by the phase detectors (PHD1, PHD2) Phase signals (γ1, γ2). 10. Order to carry out the identification process adornment of a road user according to claim 8 or Claim 9, characterized in that a vector pro processor is present at least to determine a Response telegram by a vectorial signal processing processing.