JPS6014313B2 - distance measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a distance measuring device, and more particularly to a distance measuring device that improves the response rate from a transponder.

Distance measuring devices (DistaMe Measmln)
A ground station of a navigation aid device such as gS$tem (hereinafter referred to as a DME device) transmits a station identification code given to an existing ground station at certain predetermined time intervals.

The station identification code is composed of a Morse code (e in MorseC) consisting of a combination of English letters (for example, ABC), and this Morse code is transmitted once every three calls. The Morse code is a pulse train of a constant period corresponding to a frequency of 1350 Hz that can be detected as an audible sound in the case of DME, and is switched and outputted by a signal from a Morse code generator generally called a keyer. While the Morse code is not being transmitted, the response signal to the interrogation signal for distance measurement is being transmitted. In other words, it is 1350H only when the Morse code, for example ABC, is generated by a keyer.
A pulse train of a constant period is output to Z, and other than that, response pulses corresponding to the interrogation signal from the onboard interrogator are output. Distance measurement with a DME-equipped hawk is carried out by an interrogator, that is, an interrogation pulse code transmitter mounted on the aircraft, which continuously transmits and receives interrogation pulses and response pulses in the dark with a transbonder for transmitting response pulse codes installed at a ground fixed station. This provides a position or distance measurement of the aircraft relative to the ground station.

To describe these in more detail, first, the interrogator transmitter transmits an interrogation pulse code to the ground fixed station. The transponder at the ground station transmits a response pulse toward the aircraft depending on the sign of the received interrogation pulse. The interrogator receiver identifies only the response signal to the interrogation pulse, and measures the distance between the two by measuring the time from when the interrogation pulse is sent to when the response pulse is received. On the other hand, in Morse code, which is transmitted from a ground transponder at an interval of 3 minutes, the dots are approximately 0.1 seconds long.
The highest point (dash) is 0.9 sand, and the space is 0. It is defined by the length of the mirror. Figure 1 shows an example of the station code A.
The case of BC is shown. Referring to this figure, the station code identification pulse train that is actually transmitted is output with priority over the response pulse only when the transmitted code is a dot or dash, and therefore the response signal is prohibited and not output during that time. The onboard interrogator selects only the 1350 Hz frequency component from the pulse train transmitted from the ground transponder from outside the bandpass film prepared for interrogation, and this 1350-day, two-tone station code audible tone is Sent to the pilot's receiver. Therefore, by listening to the Morse code sent from the ground station once every three minutes, Parrot can confirm whether the ground station is the one it needs and whether the ground station is normal. The second section shows a block diagram of a keying circuit that switches between a conventional general response pulse and a station identification code pulse.
This will be explained with reference to FIG. 3 and FIG. 3, which shows an example of output of response pulses and station identification codes in keying. In Figure 2, 11
, 12 is an AND circuit, 13 is an inverter, and 14 is an OR circuit. A keying signal C corresponding to the Morse code is input to the inverter 13 and the AND circuit 12. The input of the AND circuit 12 is the response pulse b, and its output is input to the OR circuit 14. The station identification code pulse a and the output of the inverter 13 are input to a logic circuit 11, and its output is used as another input to the OR circuit 14. Therefore, it can be seen that the station identification code a is outputted as a waveform d instead of the response pulse b. That is, when the keying signal is at a low level (logical 0), only the station identification code pulse is output and no response pulse is output. As mentioned above, in conventional distance measuring devices, the station code pulse is transmitted with priority over the response pulse, so the response pulse is completely prohibited while the station code pulse is being transmitted, and the onboard interrogator receives the response pulse during that time. There is a drawback that it cannot be done.

For example, in the configuration of the Morse code ABC described above, the time during which the Morse code prohibits response pulses is a total of 1. It is currently @. On the other hand, the total time from start to finish of Morse code ABC is 3.1 seconds. Therefore, the time per second during which a response pulse is blocked is 1.8/3.1=0. It becomes $ seconds. This means that during the transmission of the station code, response pulses can be transmitted for an average of 0.42 seconds per second. Generally, the three-letter combination assigned to each land station averages the above value. Therefore, even if it is assumed that the interrogation signal from the onboard interrogator is 100% decoded by the receiver of the ground transponder, the average decoding rate is about 40% when transmitting the station code as mentioned above.
This means that only a response rate of . In reality, the response rate of terrestrial transbonders is stipulated to be 70% or more in the case of DME, and if this response rate is taken into account, the actual response rate when transmitting station codes is approximately 30% (0.4 x 0 .7=0.
28). On the other hand, the onboard interrogator continues to detect response signals corresponding to its own interrogation signal even when receiving the station code from the ground transponder, and if it cannot count a certain number of responses, it will The distance measurement value is memorized, tracking is stopped, and the search state is continued until a predetermined number of responses or more are received.

And if the search continues for more than a certain period of time, the neck will appear. Clear the deer data and send a flag signal to the display device to indicate unlock. Therefore, the station code from the terrestrial transponder is, for example, AB.
If it is output as C, no distance measurement output will be obtained while the station code is being transmitted, and the distance measurement output will not be obtained while the station code is being transmitted.
The midpoint value is output for about 3 seconds during the station code transmission time, and then new side distance data is output with a slight delay, making it impossible to measure distance with high accuracy. The present invention provides a method for measuring distances at landing aid facilities, etc., where highly accurate distance information is required, when a ground station transmits a pre-given Morse code station identification code at a certain time interval. Inta.

When a response pulse corresponding to the interrogation pulse from the gator appears within a certain range of one pulse in the station identification code pulse train, the station code pulse is suppressed and the nearby response pulse is used to identify the station. The present invention provides a distance measuring device that can respond to an interrogator even when a storm code is transmitted by replacing the identification code pulse.
Next, an embodiment of the present invention will be described with reference to the drawings.

DME ground equipment generally has a basic configuration as shown in the block diagram of FIG. First, an interrogation signal composed of bare pulses from an onboard interrogator is captured by an antenna 21, inputted to a receiver 23 via a duplexer 22, and after being increased to a level that is not necessary to detect the interrogation signal, it is detected and converted into a video signal. The signal is sent to the decoder 24.
The decoder 24 detects only bare pulses from the input video signal and sends them to the priority gate 27. or,
A pulse corresponding to 1350 days 2 audible tone is applied to the priority gate 27 from a 1350 days Z pulse generator 25 for identifying the ground station. Normally, the priority gate 24 is equipped with a keying circuit as shown in FIG. 2, and allows the decoding pulse from the decoder 24 to pass through. The 1350Hz pulse is given priority to the long dots and short dots of the Morse code consisting of characters. Now, as mentioned above, in the conventional priority gate 27, the response pulse is suppressed while the station code pulse sent from the keyer 26 is being transmitted, so the number of response pulses that the interrogator receives is limited. Therefore, the present invention takes the following measures.

That is, when a response pulse corresponding to the interrogation pulse from the interrogator appears close to one pulse in the station identification code pulse train within a predetermined time, the station identification code pulse is suppressed and the station identification code pulse is suppressed. By replacing the identification code pulse with the response pulse, it is possible to respond to the interrogator even when transmitting the station identification code.

Even with this method, the station identification code detection circuit in the on-board interrogator uses a bandpass filter with a certain bandwidth, so at least about 10% (approximately 740 seconds) Even if the period changes within a maximum value of 100 peaks), it can be detected without any problem, so it will not cause any trouble to the old DM system. In other words, the present invention shifts the pulse position of each pulse of the local code pulse train to the input line of the local code pulse train within a certain range in synchronization with the response pulse.As an example of the priority gate 27 in FIG. There is a circuit shown in the figure.

The operation will be explained below. The constant repetition input station identification code 1350Hz pulse train a is generated by the first gate pulse generator 31
added to. The first gate pulse 31 is a pulse d having a predetermined width (a time width that does not interfere with the detection of the station identification code pulse by the above-mentioned interrogator), which is the rising edge of the input pulse.
is generated and applied to the pulse generator 33 and AND circuit 32. Here, the pulse generator 33 generates waveform e at the falling edge of waveform d. In addition, the response pulse train b is applied to the other input of the first AND circuit 32, and if the first
When a response signal appears between the pulse gates generated by the pulse gate generator 31, a coincidence output waveform f is output. The output waveform f is applied to a second pulse gate generator 34 and an OR circuit 36, respectively. Second pulse gate generator 3
4 generates a second pulse gate g at the rising edge of the waveform f, and is applied to one side of the second AND circuit 35. The waveform e from the pulse generator 33 is applied to the other side of the AND circuit 35, and if the gate pulse from the second pulse gate generator 34 is present, the waveform e is necessarily applied like waveform h. It is suppressed. That is, since the waveform f is the response pulse itself, the response pulse f is replaced with one station code pulse. The output waveform h of the second ND circuit 35 and the waveform f are passed through the OR circuit 36, and when the station code is transmitted, a part of the station identification code pulse train is synchronized with the response pulse to obtain a shifted waveform i. can. Waveform i is keyed by keying circuit 37 shown in FIG. Returning to FIG. 4, the output of the keying circuit 37,
That is, the output pulse of the priority gate 27 is re-encoded into bare pulses in the coder 28, and the encoded bare pulses are sent to the RF via the transmitter and duplexer 22.
It is emitted from the antenna 21 as a pulse.

Therefore, the airborne interrogator can receive signals from ground equipment, detect response signals synchronized with its own interrogation, and measure the distance to the ground station.
You can check the station identification code emitted for each piece of sand. As explained above, the present invention replaces some of the pulses of the station code pulse train with response pulses so that the cycle of the station code pulse train is within an allowable range that can be detected by the on-board interrogator. This has the effect of transmitting a response pulse corresponding to the

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an example of the station identification code Morse code, Fig. 2 is a general keying circuit diagram, Fig. 3 is a time chart of signals of each part in Fig. 2, and Fig. 4 is the basic configuration of the present invention. FIG. 5 is a detailed block diagram of the priority gate in FIG. 4, and FIG. 6 is a time chart of signals of each part in FIG. 21... Antenna, 22... Duplexer, 23... Receiver, 24... Decoder, 25... 1350Hz pulse generator, 26...
... Keyer, 27 ... Priority gate, 28 ... Coder, 29 ... Transmitter, 31, 33,
34... Pulse generator, 32, 35...
・AND circuit, 36...OR circuit, 37...
...Keying circuit. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] 1 After receiving the interrogation pulse sent from the interrogator, the transponder switches and sends out a response pulse corresponding to the interrogation pulse and a station identification code pulse train for identifying the transponder at predetermined time intervals, and the interrogator transmits the interrogation pulse. In a distance measuring device that measures the distance between two by measuring the time from pulse sending to response pulse reception, it is determined whether or not a response pulse exists within a predetermined time range near each pulse of the station identification code pulse train. Judgment circuits 31 and 32 make a judgment, and when the judgment circuit judges that a certain response pulse exists within a predetermined time range in the vicinity of a certain pulse of the station identification code pulse train, the certain pulse is Circuit 33 replaced by response pulse,
34, 35, and 36.