JPH0315788A - Mode c code correlation processing system - Google Patents

Abstract

PURPOSE:To perform the correlation processing in an easy method by discriminating the state of correlations between a real-time reception signal and the preceding signal based on the bit change detected from these reception signals. CONSTITUTION:The transponder response signal from an airplane is inputted to a serial-parallel converter 31 through a receiver and is converted to a parallel signal and is outputted to a latch circuit 33. This output is inputted to a memory 35 which temporarily holds the signal, one input terminal of a disaccord checking exclusive OR 37, and a high-level processing circuit, and the output of the memory 35 is inputted to the other input terminal of the OR 37 after a prescribed time. Consequently, the number of changed bits between the real- time mode C code reception signal inputted to the OR 37 through the converter 31 and the circuit 33 and the past received mode C code reception signal temporarily held in the memory 35 is detected by the OR 37, and the state of mutual correlations is discriminated in a disaccord bit number checking device 39 by the detection result.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to correlation processing of received signals, and in particular to correlation processing of received signals, and in particular to correlation processing of mode C signals in which an aircraft-mounted transbonder responds to an inquiry from a secondary surveillance radar used for aircraft traffic control. Related to a method for correlation processing of response signals. (Prior art) A secondary surveillance radar system used in aircraft control equipment, etc. consists of a secondary surveillance radar installed on the ground and a radar mounted on an aircraft.
The transbonder consists of a secondary surveillance radar that interrogates the aircraft, and upon receiving the interrogation, the transbonder of the aircraft sends back a response signal at a predetermined frequency. In such a secondary monitoring radar system, there are modes such as mode A that responds with an identification code, mode C that responds with altitude information, and mode S that includes an individual address in the response signal.
Each of these is indispensable for air traffic control systems. Among these secondary monitoring radar systems, in mode C, which responds with altitude information, the response signal from the aircraft changes as the aircraft moves up and down (changes in altitude), so the response signal is not a response signal sent from the same aircraft. Correlation processing is performed to confirm that the code exists and to obtain the reliability of the received code. In other words, if the information obtained from the received signal shows a change within the aircraft's motion performance range, it is determined that the response signal is from the same aircraft, and a correlation is established, and received signals that are not correlated are considered to be bad data. By processing the data as follows, the reliability of the signal processing input data in the subsequent stage is increased and the data is configured to be error-free. FIG. 4 is a block diagram showing the configuration of conventional mode C correlation processing,
The transbonder response signal received from the receiver is converted into a parallel signal by a serial-to-parallel converter 10, and latched by a latch circuit 12 at the next stage. The latch circuit output is input to a memory 14, a binary converter 16, and an advanced processing circuit (not shown), and the binary converter 16 converts the received mode C code into a binary code, and outputs it to the next stage reduction circuit 18. do. On the other hand, after a predetermined time, the parallel signal input to the memory 14 is applied to the binary converter 20 in the same way as the above-mentioned signal, and is converted into a binary code, and the output thereof is sent to the subtraction circuit 1.
Applied to 8. That is, the subtraction circuit 18 subtracts the real-time response signal inputted via the binary converter 16 and the previously received response signal inputted via the memory 14 and the binary converter 20, and calculates the altitude of the next stage. The difference comparison circuit 22 compares the codes, and if the comparison result is within the allowable range for the aircraft's maneuverability, it is determined that there is a correlation and the received Mode C code is highly reliable. It outputs information to the subsequent advanced processing circuit. However, in the correlation processing method configured in this way, the received mode C code data must be converted into a binary code one by one, so the circuit becomes complicated and the Ifi device becomes complicated and expensive. There was a problem. (Object of the Invention) The present invention has been made in view of the problems of the conventional correlation processing method as described above, and is a mode C code correlation processing in which correlation processing is performed by a simple method using the characteristics of the mode C code. The purpose is to provide a method. <Summary of the invention> In order to achieve this object, the mode C code correlation processing method of the present invention detects changes in the bits of the signal received in real time and the previous four received signals, and detects the bits that have been eclipsed.・If the number is 1 or less, it is determined that there is a mutual correlation, or a change in bits between the signal received in real time and the signal received last time is detected, and the number of changed bits is 1 or less, and there is a change. If the changed bits are bits that don't matter if they change, then we can say that there is a mutual correlation! fJIlf! The feature is that it is designed to do the following: (Example) The present invention will be explained in detail below based on the example shown in the drawings. First, in order to facilitate understanding of the present invention, the functions of the Mode C system of the secondary surveillance radar system and the altitude information transmission code used therein will be briefly explained. The interrogation mode signal of the secondary monitoring radar has a carrier wave of 1030M.
The pulse interval is 21 μs in mode C. The transbonder of the aircraft that received the interrogation signal reads the interrogation mode M, and sends a response signal with a carrier wave of 1090MI{Z12
It is sent back as a bit pulse train. However, since the D1 pulse is not used in the mode C code, the data length is 11 bits.

Therefore, the maximum identification number is 2048, and the altitude information transmission code is 126 from altitude -1000ft in 100ft units.
The 1st height is set according to each altitude up to 750ft. Further, the repetition of SIF interrogation is usually around 400 ppS, and even in the case of so-called 4-mode interlacing in which modes 1, 2, 3/A and C are repeated, the interrogation signal interval of mode C code is about 10 msec (2. 5msec
It is about X4). Fig. 1 is a diagram showing a part of the altitude transmission code (modified Dallay code) of 1 to Lance Bonder installed on the aircraft that responds to the interrogation signal of the secondary surveillance radar ground station, and the code corresponding to the altitude in units of 100 ft is shown in Fig. 1. You can see that it is set. Furthermore, as is clear from the figure, the number of bit changes in adjacent altitude sections is 1 bit, and as mentioned above, the interrogation signal repetition timing is at most 10 msec. In other words, taking these things into consideration, the aircraft
Because it is impossible to move up and down 100ft with the motion characteristics of the aircraft currently in use, the altitude information transmission code will only change by one bit at most compared to what was sent last time. Also, for example, if the altitude of the aircraft is 1000f
t, the altitude information transmission code sent by the aircraft is 00000110010, and if the altitude of the aircraft changes by 100ft, the altitude information transmission code at that time is 00000110011 or 00000.
110110, and considering the altitude transmission code of 1000ft as a standard, the bits that change are limited to the 1st bit or the 3rd bit. In other words, even if the number of change bits in the altitude information transmission code changes only by 1 or more bits, if the changed part is a bit other than the 1st or 3rd bit, the received altitude transmission code is inappropriate. It turns out that this information is useful. Therefore, by using the characteristics of the mode C altitude information transmission code and the motion characteristics of the aircraft, it is possible to perform correlation processing of the received signal by a simple method. The Mode C reception code correlation processing method of the present invention will be explained in detail below. FIG. 2 is a diagram showing an embodiment of the present invention, in which 31 is a serial-parallel converter, 33 is a latch circuit, 35 is a memory, 37 is an exclusive OR, and 39 is a mismatch bit. It is a number checker.

In the mode C code correlation processing device having such a configuration, the transbonder response signal from the aircraft is input to the serial-to-parallel converter 31 via a receiver (not shown),
After converting it into a parallel signal, it is output to the next stage latch circuit 33. The output of the latch circuit 33 is input to a memory 35 that temporarily holds the signal, a single end of the exclusive OR 37, and an advanced processing circuit (not shown). It is input to the input terminal. Therefore, the real-time mode C code reception signal inputted to the exclusive OR 37 via the serial-parallel converter 31 and the latch circuit 33 and the previously received mode C code reception signal temporarily held in the memory 35 are The number of bit changes is detected by inputting it to the exclusive logic flj sum 37, and the detection result is input to the next-stage mismatched bit number checker to check that the detected number is 1 or less, that is, O
Or, if it is 1, it is determined that the received signals are correlated, and a correlation output is given to an advanced processing circuit (not shown). The correlation processing method using the means described above simply generates a correlation output when the number of mismatched bits is 1 or less (O or 1), and does not specify the position of the bit that does not matter even if it is mismatched. Even if a bit error of l bits occurs at the position, it is determined that the correlation has been obtained, and a correlation processing output is generated. Therefore, in order to increase the reliability of the correlation output, the accuracy of the data can only be guaranteed after at least three consecutive correlation outputs occur.
The reliability of the correlation output can be further increased by using the method described below. FIG. 3 is a diagram showing another embodiment of the present invention, in which 31 is a serial-to-parallel converter, 33 is a serial-parallel converter, and 33 is a serial-to-parallel converter;
35 is a memory, 36 is an AND circuit, 37 is an exclusive logic homologous circuit, 39 is a mismatch bit number checker, 4
1 is a mismatch override bit selection ROM, 43 is a mismatch bit override circuit, 45 is a mismatch bit number check gate, 47 is an illegal code check circuit, and 4 are AND circuits.

In such an N4 mode C code correlation processing device, the transbonder response signal from the aircraft is input to the serial-to-parallel converter 31 via a receiver (not shown), converted to a parallel signal, and then transmitted to the next stage. It is output to the latch circuit 33. The output of the latch circuit 33 is applied via an AND circuit 36 to a memory 35 that temporarily holds the signal, an exclusive OR circuit 37, and an illegal code check circuit 47, and the memory 35 stores the input transbonder response signal. , when the next response signal is input, the exclusive OR circuit 37 and the mismatch override bit selection ROM 4
Output the data to 1. That is, the exclusive OR circuit 37 inputs the real-time hit transbonder response signal and the previously received transbonder response signal, and checks for mismatch bits. For example, the altitude information transmission code received last time is 000001.
10010, and the data is supplied from the memory 35 to the exclusive OR circuit 37 via the serial-to-parallel converter 31 and the latch circuit 33.
The altitude information transmission code of the transbonder response signal of real-time hip 1 inputted to 7 is 00000110011.
In the case of
<o: match, 1: mismatch).

Therefore, the three mismatch bit number check circuits determine whether the number of mismatch bits is O or 1, and if the input data is ooooooooooo1 as described above, the mismatch bit 1. is 1 bit 1-. , the mismatch bit check 2839 is judged to be normal, and 1” (normal)
Outputs the signal to four AND circuits. On the other hand, the mismatched override pit selection ROM 41 supplies information on the bit 11, which may change depending on the input data, to the mismatched bit 1 override circuit at the next stage. That is, the mismatch override bit selection ROM 41 outputs 11-bit data using the input data as an address, and for example, if the data output from the memory 35 is 0.
In the case of 0000110010, the corresponding altitude is 1000
ft, but the altitude that can be moved within 10 msec from the altitude is 900 ft or 1100 ft, so the altitude data is 00000110011 or 00000110110, and therefore 1000 ft.
Compared to the altitude data of , only 1 and 3 bits change. Therefore, 1000f from memory 35
When the altitude data of t is output, the bits that are allowed to change corresponding to the altitude are 1 bit and 3 bits, so the data becomes 00000000101 (1: variable allowed, 0: variable not allowed). It is output to the mismatch bit override circuit 43 at the next stage. The output from the exclusive logical sum circuit 37 is applied to the mismatch bit override circuit 43, and as described above, when the data 00000000001 is output, the data is compared with the variable allowable data, and the exclusive logical sum circuit 37 is applied. The 1st and 3rd bits of the data output from the logical OR circuit 39 are data that are allowed to be changed, so they are forced to change.
It is rewritten to 0゛ (match). In other words, the mismatch bit override circuit writes 00ooo
The data oooooo is checked for the number of mismatched bits in the next stage.
The signal is output to the gamma gate 45. The inconsistent bit number check gate 45 determines whether all bits of the input data are "0°", and if all bits are "O", the output is "1", otherwise the output is "0". Furthermore, the output of the latch circuit 33 is applied to the illegal code check circuit 47, and when an illegal code is input, "0" is output to AND4 836 and 49, indicating that a normal code is input. In this case, it is configured to output "1".

Therefore, the AND circuit 36 outputs the received code to the memory only when a normal code is input, while the AND circuit 49 receives normal altitude information, and the real-time received code and the previously received code are 1 bit. If the change is within the range of 0 and the changed bit is a bit that is allowed to vary, all input signals become 1, and the correlation output is output because the game 1 is augerized. For example, if the altitude data received last time is 00000110010, which is 1000ft altitude information, and the altitude data received in real time is 00000111010, which is 1500ft altitude information, the exclusive OR circuit 39 outputs ooooooooiooo, which is a mismatch. Since the number of mismatched bits in the three pit check circuits is 1, the data indicating normality is outputted to the next AND circuit *49, but if the altitude data received last time was 1000ft, real-time Since the variable allowable bit of the altitude data received is the 1st or 3rd bit,
The mismatch bit override circuit 43 does not rewrite the fourth bit of mismatch data among the input data, and the mismatch bit number check gate at the next stage outputs "0" to the AND gate 49 because there is a mismatch bit, and the correlation is No output is printed.

In other words, even if the number of bit changes between the input altitude data and the previously received altitude data is 0 or 1, if there is a change in a bit that is not allowed to change, the received data will be considered incorrect. mfi. has been done.

In this way, the correlation processing method of the present invention has the property that the mode C reception code does not change by 1 bit per 100 ft, and the motion characteristics of current aircraft mean that the mode C reception code changes by 10 msec
Since the correlation processing is performed based on the characteristic that it is impossible for the altitude to change by 100 ft at 1.c, compared to the conventional method, it is possible to perform the correlation processing based on the characteristic that it is impossible for the altitude to change by 100 ft at 1.c. You can get the functions of il-bu. (Effects of the Invention) Since the present invention is horizontal and functional as described above, when performing correlation processing on mode C code received signals, it can be performed without converting each received signal into a binary signal. This is extremely effective in making the circuit simple and inexpensive.

[Brief explanation of the drawing]

Figure 1 shows the mode C code and f2 code.1)
2l2l is the country in which the present invention is implemented. The third garden is a diagram showing another embodiment of the tree invention, and FIG. 4 is a diagram showing a conventional correlation processing circuit. 10, 31... Serial-parallel converter, 12.3
3... Latch circuit, 14, 35... Memory, 16, 20... Binary converter, 18... Subtractor, 22... Altitude difference comparison circuit, 36,
4 ・And times! ! Each, 37...exclusive logic circuit,

Claims (2)

[Claims] (1) In the Mode C code correlation processing method, which is a Mode C system used in air traffic control, aircraft collision prevention systems, etc., which performs correlation processing of response signals from aircraft, signals received in real time and previous A mode C code correlation processing method characterized in that a change in bits of a received signal is detected, and when the number of changed bits is 1 or less, it is determined that mutual correlation has been established. (2) In the Mode C code correlation processing method of the Mode C system used in aircraft collision prevention systems, which performs correlation processing of response signals from aircraft, there is a difference between signals received in real time and previously received signals. Mode C code correlation characterized in that a change in bits is detected, and if the number of changed bits is 1 or less and the changed bit is in a bit position where variation is allowed, it is determined that mutual correlation has been established. Processing method.