JPH0797137B2 - Secondary radar response signal identification method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a secondary radar.

[Prior Art] The ground equipment of the secondary radar system currently used for air traffic control, etc. is composed of a transmitting antenna, a transmitter and an interrogator with a built-in receiver, and a decoder. An INT antenna with a sharp directivity in the horizontal plane and an SLS antenna showing a pattern close to omnidirectional covering the side lobes of the INT antenna are used.

An interrogation signal with a frequency of 1030 MHz is emitted from the INT antenna, and transponders of a plurality of aircraft existing in the main beam of the INT antenna each receive and decode the interrogation signal and transmit a corresponding response signal. ing.

The response signal from the transponder is typically received and decoded at the same antenna as the transmitting antenna. The direction and distance of the transponder that responded is specified from the direction of the transmitting antenna and the time from the transmission time of the inquiry signal to the reception of the response signal, and the response signal is decoded to identify the aircraft.

[Problems to be Solved by the Invention] With such a configuration, the response signal is transmitted from the transponders of all aircraft existing in the main beam of the transmitting antenna. Therefore, in areas such as airports where aircraft with transponders are densely packed,
Since a plurality of transponders respond at the same time, the response signals are superimposed and received, so that the received signals cannot be decoded.

Further, there is a problem in that the accuracy of the distance is reduced due to an error in the response time of the transponder.

[Means and Actions for Solving Problems] Response signals from a plurality of transponders are received by two receiving stations forming a set, and the received signals of the two receiving stations are subjected to correlation processing, Detecting the maximum value of the correlation and the time at which the maximum value is detected, time-shifting one of the received signals by the time at which the maximum value of the rebate is reached, and obtaining the scalar product with the other received signal. The particular response signal having the maximum value of the received electric field strength is emphasized from among the plurality of response signals, and the particular response signal thus emphasized is basically the response signal defined by the secondary radar system. Whether or not it is included in the basic pulse train having the property, if it is included, the response signal is decoded to identify the transponder, and even when the response signal is received in a superimposed manner, Maximum response signal The transponder with electric field strength can be identified.

In addition, the emphasized specific response signal is deleted from the reception signals of the two receiving stations, and new reception signals are created, respectively, so that the transponders are sequentially identified from the one having the highest received electric field strength. I have to.

Furthermore, at least three receiving stations are installed, and response signals from a plurality of transponders are sent to any two receiving stations.
At least two sets of receiving stations that form a set are subjected to correlation processing of received signals from any two receiving stations that form a set, and from the responder to the two receiving stations that form the set. The time that shows the maximum value of the correlation corresponding to the arrival time difference of the response signal of each is tested for each group, and the position of the transponder is specified from the intersection of these arrival time differences. In addition to enabling high-accuracy position measurement regardless of time error, one of the received signals that make up the set to which this transponder belongs is time-shifted by the time that shows the maximum value, and a set is made up. By obtaining a scalar product with the other received signal, a particular response signal having the maximum value of the received electric field strength is emphasized from among the plurality of response signals, and this emphasized particular response signal is If the emphasized specific response signal is included in the basic pulse train after checking whether or not it is included in the basic pulse train having the basic characteristics as the response signal specified by the radar system, this specific response is included. The signal is decoded to identify the transponder.

[Embodiment] An embodiment of the present invention will be described in detail with reference to Figs.

FIG. 1 is a schematic diagram of a secondary radar system according to the present invention, in which A and B are a plurality of aircraft existing in the main beam of an INT antenna (not shown) (hereinafter referred to as transponders).
In this case, transponders (not shown) are mounted respectively.

As ground equipment, three receiving stations 1, 2, and 3 are installed at mutually distant points. Of these, at least two sets of receiving stations (for example, receiving stations 1 and 2 and receiving stations 2 and 3) having two arbitrary receiving stations (for example, receiving stations 1 and 2) as one set
Are processed as a set. 1a, 2a and 3a are receiving antennas of the receiving stations 1, 2 and 3, respectively.

In this embodiment, one of the receiving stations 1, 2 and 3 (reception station 2) is used in common, but one more receiving station is newly provided, and two stations each are provided. The same is true for two sets of ground equipment.

A memory 4 stores the response signals received by the receiving stations 1, 2, and 3.

Here, the received signal uses a carrier wave in the vicinity of 1090 MHz. With the current technology, it is impossible to record this received signal as it is, so it is converted to an intermediate frequency that can be stored in the memory 4. At this time, in order to save the phase information of the received signal, The waveforms transmitted from the local oscillators are converted into intermediate frequencies by using mutually orthogonal waveforms, that is, a sine wave and a cos wave, and are stored in the memory 4.

A processor 5 processes various signals.

S _a and S _b are response signals of transponders A and B, E ₁ (t) and E, respectively.
₂ (t) are the received signals received by the receiving stations 1 and 2, respectively.

FIG. 2 shows a block diagram for identifying the transponders A and B. Reference numeral 6 denotes received signals E ₁ (t) and E ₂ (t ₂ received by the receiving stations 1 and 2 at arbitrary two places. ) Is a correlator, 7 is a delay device, and one of the received signals is received by the correlator 6
This is for time-shifting by the time that indicates the maximum value of the correlation obtained in. Reference numeral 8 denotes a multiplier, which outputs an absolute value without considering the phase information. 9 is a tester, 10 is a responder A, B
It is a discriminator that identifies ...

Reference numeral 11 denotes a multiplier, which stores phase information and amplitude information. Reference numeral 12 is a square root calculator for obtaining square roots of the real number axis and the imaginary number axis of the signal from the multiplier 11, 13 is a phase characteristic detector, 14 is a pulse generator, and 15 is a processor.

Next, the operation will be described.

First, when the received electric field strength of the response signal from the transponder A is the maximum among the plurality of transponders that respond by superimposing,
That is, the case where the first peak value is shown will be described with reference to FIGS.

As shown by the envelope waveforms in FIGS. 3A and 3B, the response signals S _a from the plurality of transponders A and B,
S _b is a combination of two arbitrary receiving stations (for example, receiving stations 1 and 2) installed at mutually distant points, and at least three receiving stations 1, 2, and 3 that form a set. Each is received.

First, as the envelope waveforms are respectively shown in FIGS. 3 (c) and 3 (d), the two receiving stations 1 and 2 forming the set are formed.
Received signal E, which is a time-series signal received at
_{Although 1} (t) and E ₂ (t) are stored in the memory 4, between the response signals S _a and S _b and the received signals E ₁ (t) and E ₂ (t), E (t) and E ₂ (t) are stored. ₁ (t) = A _a1 S _a (t−t _a1 ) + A _b1 S _b (t−t _b1 ) ... (1) E ₂ (t) = A _a2 S _a (t−t _a2 ) + A _b2 S _b (t−t _b2 ) ... (2) holds.

Here, A _a1 and A _a2 are response signals S _{a at the} receiving stations 1 and 2, respectively.
Amplitude, A _b1, A _b2 is the response signal S _b at the receiving station 1, 2, respectively
Amplitude, t _a1, t _a2, the time response signal S _a to reach the respective receiving station 1, the answering machine A, t _b1, t _b2 is the response signal S _b is respectively received from the responder B station 1, Is the time to reach.

Next, in the correlator 6 for the received signals E ₁ (t) and E ₂ (t) of the receiving stations 1 and 2, the correlation processing (cross correlation is performed) is performed (the envelope waveform is shown in FIG. 3E). (Shown), the maximum correlation and the time τ at which the maximum correlation is reached are obtained. Note that this time τ is equal to the arrival time difference (t _a1 −t _a2 ) or (t _b1 −t _b2 ) between the response signals S _a and S _b from the transponders A and B to the two receiving stations 1 and 2. .

Here, for the response signal S _a , the above time τ is τ ₁ . Therefore, only one received signal E by τ ₁ = t _a1 −t _{a2
When 1} (t) is shifted by the delay device 7, the equation (1) becomes E ₁ (t + τ ₁ ) = E ₁ (t + t _a1 −t _a2 ) = A _a1 S _a (t−t _a2 ) + A _b1 S _b (T−t _b2 + t _a1 −t _a2 ) ... (3)

In the multiplier 8, one of the time-shifted received signals E ₁ (t + τ ₁ ) shown in formula (3) and the other received signal E ₂ (t) shown in formula (2) Taking the scalar product (hereinafter simply referred to as the scalar product) that kills the individual products of the constituent elements of the time-series signal that can be considered (Fig. 4 (f)
Envelope waveform is shown in Fig. 2) E ₁ (t + τ ₁ ) ・ E ₂ (t) = E ₁ (t + t _a1 −t _a2 ) ・ E ₂ (t) = A _a1 A _a2 S _a ² (t−t _a2 ) + A _a1 A _b2 S _a (t−t _a2 ) × S _b (t−t _b2 ) + A _b1 A _b2 S _b (t−t _b2 ＋ t _a1 −t _a2 ) × S _a (t−t _a2 ) + A _b1 A _b2 S _b (t−t _b2 + t _a1 −t _a2 ) × S _b (t−t _d2 ) ... (4)

From this equation (4), the S _a signal of the first term is squared to become S _a ² , so only this signal is emphasized, but S _a S _{b of} the second term and the third term Since S _b S _a is different from each other, it is not emphasized, and since S _b and S _{b in} the fourth term have a time lag, they are not emphasized.

From this, the value of the scalar product can be
The particular response signal having the maximum received electric field strength among the response signals S _a , S _b, ...

The pulse train of this emphasized specific response signal is defined as P _a .
In the multiplier 8, the phase information of the signal P _a does not matter.

The pulse train P _a of this emphasized specific response signal is the calibrator 9
In, it is verified whether or not it is included in the basic pulse train (a pulse train including all the pulses having the basic properties defined by the secondary radar system).

When it is included in the basic pulse train as a result of the test, the discriminator 10 decodes the response signal S _a , and the responder A
Are identified.

If the emphasized signal P _a is not included in the basic pulse train, a similar operation is performed on the next maximum value of correlation to identify the transponder, as described below.

Next, in order to determine the position of the answering machine A, the answering machine A to 2
Arrival time of the response signal S _a to the receiving stations 1 and 2 at some point τ ₁ =
A hyperbola in which _{a1 −} t _a2 is integrated is drawn.

On the other hand, the two receiving stations 3 and 2 or the receiving station 1 or the receiving station 1 (which may be provided with a new receiving station) forming the other set respectively receive the response signal S _a , and the same as above. The correlation processing is performed to test the time τ ₂ at which the maximum value of the correlation is exhibited. That is, this time τ ₂ corresponds to the arrival time difference of the response signals from the transponder A to the two receiving stations 3 and the receiving station 2 or the receiving station 1. Therefore, similarly, a hyperbola with a constant arrival time difference τ ₂ is obtained. be painted.

The position of the transponder A is specified from the intersection of the two hyperbolas indicating these two arrival time differences τ ₁ and τ ₂ .

Next, in the case where the received electric field strength of the response signal S _b from the responder B shows the second strongest second peak value of the response signal S _a from the responder A, based on FIGS. 1 to 4. Explain.

Received signals E ₁ (t) and E ₂ (t) received by the receiving stations 1 and ₂
In addition to the strong signal P _a obtained above, _a large number of weak response signals are included in the inside, but these weak response signals are covered with the strong signal P _a . So this strongest signal P _a
In order to remove the signal and detect the weak signal, the strong signal P _a must be eliminated.

Therefore, when the received signals E ₁ (t) and E ₂ (t) received by the receiving stations 1 and 2 are subjected to correlation processing by the correlator 6, similarly to the above-described calculation, the maximum correlation value and the maximum correlation value are calculated. Shown time τ ₁ =
t _a1 −t _a2 is obtained.

Therefore, one of the received signals for the above time τi = t _a1 −t _a2
After E ₁ (t) is time-shifted by the delay device 7, one of the time-shifted received signals E ₁ (t + τ ₁ ) shown by the formula (3) and the other shown by the formula (2) in the multiplier 11 If a scalar product E ₁ (t + τ ₁ ) * E ₂ (t) between the received signal E ₂ (t) and the received signal E ₂ (t) is taken, this scalar product is emphasized by the specific response signal S _a received by the receiving station 1. It is P _a .

It should be noted that * means that the multiplication is performed while the amplitude information and the phase information are stored.

Therefore, the pulse train of the first emphasized signal P _a above is
Since it corresponds to the specific response signal (the response signal S _a in the above case) having the maximum received electric field strength, the received signals E ₁ (t) and E ₂ (t) at the receiving stations 1 and 2 are If P _a1 (t) and P _a2 (t) at each reception point of the emphasized signal P _a are deleted, then the response signal S showing the maximum value is obtained.
You can find the signal corresponding to _b .

Therefore, from the received signal E ₁ (t) at the receiving station 1 to the signal P
A method of removing _a1 (t) will be described. First, P _a1 (t) = γ ₁ {α ₁ (t) + jβ ₁ (t)} (5) P _a2 (t−τ ₁ ) = τ ₂ {α ₂ (t−τ ₁ ) + jβ ₂ (t-τ ₁ )} (6), the equations (5) and (6) have different amplitudes but the same waveform.

Here, since the signal P _a pulse train is most emphasized in the signal group included in the equation (5), the following assumption is made.

α ₂ (t−τ ₁ ) = α ₁ (t) β ₂ (t−τ ₁ ) = β ₁ (t) Then, in the multiplier 11, P _a1 (t) and P _a2 (t−)
Taking the scalar product * with τ ₁ ), P _a1 (t) * P _a2 (t−τ ₁ ) ≡γ ₁ γ ₂ {S _α α ₁ ² (t) + jS _β β ₁ ² (t)} (7)

However, the code of S _α : α ₁ (t) and the code of S _β : β ₁ (t) are shown.

As is clear from the above equation (7), the phase information and the amplitude information are stored in the multiplier 11.

Therefore, the square root calculator 12 finds the value of the square root of the real and imaginary axes of the vector scalar product P _a1 (t) * P _a2 (t−τ ₁ ) of the signal P _a . FIG. 4 (a) shows an envelope waveform showing the square root of the real number axis. The envelope waveform showing the square root of the imaginary axis is also the same as that of the real axis.

From the value of this square root, the phase characteristic φ _a (t) of the pulse train signal P _a emphasized in the phase characteristic detector 13 is estimated.

However, t: shows the value when the pulse train P ▲ _^'a ▼ exists.

Since equation (8) approximately represents the phase characteristic of P _a of the pulse train, the reference pulse train having this phase characteristic and the received signal E ₁
Correlate with (t) and estimate the amplitude A _a of the particular emphasized P _a from the maximum value of the correlation.

In this way, it has an estimated respectively the amplitude A _a phase characteristic phi _a and _(t), the pulse train signal P _a same new pulse train signal P ▲ _^'a ▼ is created by the pulse generator 14.

The processor 15 subtracts the pulse train signal P ^{′ ′} _a from the received signal E ₁ (t) to create a new received signal E ^{′ ′} ₁ ▼ (t) in which the emphasized pulse train signal P _a is erased.
(The envelope waveform is shown in FIG. 4 (b)) The received signal E ₂ (t) at the other receiving station 2 is also
Similarly, the emphasized pulse train signal P _a is erased to create a new received signal E ▲ ^' ₂ ▼ (t).

These new received signals E ▲ ^′ ₁ ▼ (t) and E ▲ ^′ ₂ ▼
As shown in the envelope waveform in FIG. 4C, (t) is subjected to correlation processing by the correlator 6 and indicates the maximum value of the correlation and the maximum value of the correlation in the same manner as above. The time τ ₃ is obtained.

This time τ ₃ is equal to the arrival time difference (t _b1 −t _b2 ) of the response signal S _b from the responder B to the two receiving stations 1 and 2.

Therefore, in the same procedure as when the responder A is identified, the delay device 7
, One of the new received signals is time-shifted by time τ ₃ , and then the multiplier 8 calculates the scalar product with the other new received signals (Fig. 4 (d)), the tester 9, and the discrimination. The responder B is identified via the instrument 10.

It should be noted that FIG. 4 (e) shows a new received signal E ′ (t) from which the second peak value of the received electric field strength has been removed. FIG. 4 (f) shows the waveform of FIG. 4 (a). It is the one obtained by subtracting the waveform of FIG. 4 (e), and it is determined from the pulse shape that it is not the response signal from the transponders A and B.

Next, in order to determine the position of the transponder B, a hyperbola having the same arrival time difference τ ₃ is drawn as in the case of the transponder A.

Next, the received signals at the two receiving stations 3 and the receiving station or the receiving station 1 forming another set are subjected to correlation processing, and the time τ ₄ showing the maximum value of the correlation is tested, and this time τ ₄ is constant. A simple hyperbola is drawn, and the position of the transponder B is determined from the intersection of the arrival time differences τ ₃ and τ ₄ .

In this way, the transponders are sequentially identified in descending order of the received electric field strength of the response signal.

EFFECTS OF THE INVENTION The present invention receives response signals from a plurality of transponders at two receiving stations forming a set, performs correlation processing on the received signals at the two receiving stations, and maximizes the correlation. Value and the time when the maximum value is shown, and either one of the received signals is time-shifted by the time showing the maximum value of the correlation, and the scalar product of the vector component is obtained with the other received signal. The particular response signal having the maximum value of the received electric field strength is emphasized from among the plurality of response signals, and the emphasized particular response signal is a basic response signal defined by the secondary radar system. Whether or not it is included in the basic pulse train having the following properties, and if it is included,
Since the response signal is decoded and the response device is identified, even when response signals from multiple response devices are received in a superimposed manner,
It is possible to identify the transponder whose response signal has the maximum received electric field strength.

Furthermore, the emphasized specific response signals are deleted from the reception signals of the two receiving stations, and new reception signals are created respectively, so that the response devices with higher received electric field strength of the response signals are sequentially arranged. Since the identification is performed, the transponder can be identified even from the received signal whose received electric field strength is weak.

Furthermore, at least three receiving stations are installed, and response signals from a plurality of transponders are sent to any two receiving stations.
At least two sets of receiving stations that form a set are subjected to correlation processing of received signals from any two receiving stations that form a set, and from the responder to the two receiving stations that form the set. The time that shows the maximum value of the correlation corresponding to the arrival time difference of the response signal is tested for each set, the position of the responder is specified from the intersection of these arrival time differences, and the set to which this responder belongs is configured. One of the received signals is time-shifted by the time that shows the maximum value, and the scalar product is calculated between the received signal and the other received signal that makes up the set. A specific response signal having a value is emphasized, and whether or not the emphasized specific response signal is included in a basic pulse train having a basic property as a response signal specified by the secondary radar system is determined. After the determination, if the emphasized specific response signal is included in the basic pulse train, the specific response signal is decoded and the transponder is identified. Therefore, regardless of the time error due to the response delay of the transponder, Highly accurate position measurement is possible.

[Brief description of drawings]

The drawings show an embodiment of the present invention. FIG. 1 is a schematic diagram, FIG. 2 is a block diagram, and FIGS. 3 and 4 are envelope waveform diagrams. A, B ... responder 1, 2 ... receiving station 5, 15 ... processor 6 ... correlator 7 ... delay device 8, 11 ... multiplier 9 ... verifier 10 ... discriminator 12 ... Square root calculator 13 …… Phase characteristic detector 14 …… Pulse generator

Claims (4)

[Claims] 1. A response signal from a plurality of transponders is received by two receiving stations forming a set, and the received signals of the two receiving stations are subjected to a correlation process to obtain a maximum correlation value and its correlation value. And a time indicating a maximum value is detected, and one of the received signals is time-shifted by a time indicating the maximum value, and a scalar product is calculated between the received signal and the other received signal, thereby obtaining a plurality of the plurality of received signals. A specific response signal having the maximum value of the received electric field strength is emphasized from the response signals, and the emphasized specific response signal has a basic property as a response signal specified by the secondary radar system. If the emphasized specific response signal is included in the basic pulse train after testing whether it is included in the basic pulse train, the specific response signal is decoded to identify the transponder. And the secondary How to identify the response signal of the radar. 2. The emphasized specific response signal is divided into two, respectively.
The secondary radar according to claim 1, wherein the transponders are sequentially identified from the one having a higher received electric field strength by deleting the received signals from the receiving stations at the locations and creating new received signals respectively. Response signal identification method. 3. A phase characteristic of the specific response signal is estimated from the respective square root values of the real number axis and the imaginary number axis of the emphasized specific response signal, and a reference pulse train having this phase characteristic and reception of either one of them. The received signal of the station is subjected to correlation processing, the amplitude of the emphasized specific response signal is estimated from the maximum value of the correlation, and a new pulse train signal having the estimated amplitude and the estimated phase characteristic is created. , A new received signal in which the specified response signal having the maximum value of the correlation is deleted by subtracting the new pulse train signal from the emphasized specific response signal,
The method for identifying a response signal of a secondary radar according to claim 2, wherein the reception signals of two receiving stations are created respectively. 4. Receiving stations are installed at at least three locations, and response signals from a plurality of transponders are received by at least two groups of receiving stations, one of which is any two locations of the receiving stations. , Correlating the received signals of the arbitrary two receiving stations forming each set, and reaching the maximum value of this correlation and the receiving signal from the responder to the two receiving stations forming the set The time showing the maximum value of the correlation corresponding to the time difference is tested for each set, and the position of the responder is specified from the intersection of these arrival time differences, and either one of the groups forming the responder belongs. The received signal is time-shifted by the time indicating the maximum value, and the scalar product is obtained between the received signal and the other received signal forming the set, thereby obtaining the received electric field strength of the plurality of response signals. Maximum value After emphasizing the specific response signal to be tested, and verifying whether this emphasized specific response signal is included in the basic pulse train having the basic properties as the response signal specified by the secondary radar system. A method of identifying a response signal of a secondary radar, wherein when the emphasized specific response signal is included in the basic pulse train, the specific response signal is decoded to identify the transponder.