JPS6229038B2 - - 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 and provides a highly accurate distance in real time.

Distance Measuring
A ground station of a navigation aid device such as DME equipment (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 a combination of alphabetic characters (e.g.
Morse code (ABC)
This Morse code is sent once every 30 seconds. The Morse code is
Frequency 1350 that can be detected as audible sound for DME
A pulse train with a constant period corresponding to Hz 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. That is, a pulse train with a constant cycle of 1350 Hz is output only when the keyer generates Morse code, for example, ABC, and at other times, response pulses corresponding to the interrogation signal from the onboard interrogator are output.

Distance measurement using a DME device requires that an interrogator, that is, an interrogation pulse code transmitter, be mounted on the aircraft and continuously transmit and receive interrogation pulses and response pulses between it and a transponder for transmitting response pulse codes installed at a ground fixed station. This provides a position or range 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 is
Only the response signal to the interrogation pulse is identified, and the distance between the two is measured by measuring the time from when the interrogation pulse is sent to when the response pulse is received.

On the other hand, Morse code, which is transmitted from a ground transponder at intervals of once every 30 seconds, has a dot of about 0.1 seconds and a dash of about 0.3 seconds.
The space is defined by a length of 0.3 seconds, and the first
The figure shows the case of station code ABC as an example.
Referring to this figure, the actually transmitted station code identification pulse train is output with priority over the response pulse only when the transmitted code is a dot or dash, and therefore, during that time, the response signal is prohibited and not output. The onboard interrogator selects only the 1350 Hz frequency component from the pulse train transmitted from the ground transponder using a bandpass filter installed in the interrogator, and this 1350 Hz tone audible station code is transmitted to the aircraft pilot's receiver. Sent. Therefore, the pilot can
By listening to the Morse code that is sent every 30 seconds, you can check whether the ground station is the one you need and whether the ground station is normal.

This will be explained with reference to FIG. 2, which shows a block diagram of a conventional keying circuit that switches between a general response pulse and a station identification code pulse, and FIG. 3, which shows an output example of a response pulse and a station identification code pulse in keying. do. In FIG. 2, 11 and 12 are AND circuits, 13 is an inverter, and 14 is an OR circuit. Keying signal C corresponding to Morse code
is input to the inverter 13 and the AND circuit 12.
Another input to the AND circuit 12 is a response pulse 13, the output of which is input to an OR circuit 14. The station identification code pulse a and the output of the inverter 13 are input to the AND circuit 11, and the output is input to the OR circuit 14.
Use other inputs. Therefore, it can be seen that the station identification code a is output 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 while the station code pulse is being transmitted, the response pulse is completely prohibited, and the onboard interrogator does not transmit the response pulse during that time. There are disadvantages that cannot be obtained. For example, in the configuration of the Morse code ABC described above, the time during which the Morse code inhibits response pulses is a total of 1.8 seconds, referring to FIG. On the other hand, the total time from start to finish of Morse code ABC is 3.1 seconds. Therefore, the time during which a response pulse is blocked per second is 1.8/3.1=0.58 seconds. In other words, while transmitting the station code, on average
This means that the response pulse can be sent for only 0.42 seconds. Generally, the three-letter combination assigned to each land station averages the above value. Therefore, even if we assume that the interrogation signal from the onboard interrogator is 100% decoded by the receiver of the ground transbonder, on average the interrogation signal will be decoded by approximately
This means that only a 40% response rate can be expected. In reality, the response rate of terrestrial transponders is
70% or more is specified, and if this response rate is taken into consideration, the actual response rate when transmitting the station code is approximately 30% (0.4×0.7=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,
The distance measurement value up to that point is stored, tracking is stopped, and the search state is continued until a predetermined number of responses or more is received. When the search continues for a certain period of time, the distance measurement data is cleared and a flag signal is sent to the display device to indicate unlocking. Therefore, when the station code is output from the terrestrial transponder as ABC, for example, no distance measurement output is obtained while the station code is being transmitted, and the measured value immediately before the station code starts transmitting is approximately the station code transmission time. It is output for 3 seconds, and then new distance measurement data is output with a slight delay. For this reason, it has been difficult to accurately and in real time obtain constantly changing distance information such as final landing approach.

The present invention is applicable to a distance measuring device such as a landing aid facility where highly accurate distance information is required, when a ground station transmits a pre-given Morse code station identification code at a predetermined time interval. When the interrogation pulse from the on-board interrogator is higher than a predetermined level, priority is given to the response to this interrogation pulse, and by replacing the station identification code pulse with a response pulse corresponding to the above interrogation pulse, the interrogator can respond even when transmitting the station identification code. The object of the present invention is to provide a distance measuring device that can respond to an extremely high response rate and provide highly accurate distance information in real time.

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 consisting of a pair of pulses from an onboard interrogator is captured by an antenna 21, inputted to a receiver 23 via a duplexer 22, amplified to the level necessary to detect the interrogation signal, and then detected as a video signal. It is sent to the decoder 24 as a.
The decoder 24 detects only paired pulses from the input video signal and the priority gate 27
send to Further, a pulse corresponding to a 1350 Hz audible sound for identifying a ground station is applied to the priority gate 27 from a 1350 Hz pulse generator 25. Normally, the priority gate 27 is equipped with a keying circuit as shown in FIG. 2, and allows the decoding pulse from the decoder 24 to pass through. However, the keying signal, that is, the keying signal output from the keyer 26 every 30 seconds, is a keying circuit as shown in FIG. Priority is given to passing the 1350Hz pulse when there is a long point or a short point in the configured mall code.

Now, as mentioned above, in the conventional priority gate 27, the response pulse is suppressed while the station code pulse sent out from the keyer 26 is being transmitted, so the number of response pulses that the interrogator receives is limited. Since it is difficult to obtain distance information with high precision and in real time during final landing approach, etc., the present invention takes the following measures.

That is, when the interrogation pulse from the interrogator (aircraft) is above a predetermined level, it is assumed that the interrogation pulse is from the interrogator that has approached the transponder (ground station), and a response pulse corresponding to this interrogation pulse is sent out preferentially. The station identification code pulse train (1350
Hz) pulses are suppressed. Even in this case, the number of suppressed pulses is small compared to the total, so there is no problem in station identification.

Now, on the other hand, the interrogation signal from the receiver 23 is compared with a predetermined level by a comparator 28, and when the interrogation signal level is higher than the above level, an interrogation signal level detection gate pulse e is sent to the priority gate 27.

As an example of the priority gate 27, the fifth
There is a circuit shown in the figure. Its operation will be explained below with reference to FIG. 1350 for station identification code with constant repetition
The Hz pulse train a is transmitted through the delay circuit 31 and the AND circuit 34.
are added to one side respectively. The 1350Hz pulse train a is delayed by a time slightly longer than its own pulse width in the delay circuit 31, and outputs a waveform f, which is generally known as R-
It is applied to the R (reset) terminal of SF/F (flip-flop) 33.

On the other hand, the interrogation signal level detection gate pulse e and the response pulse b are respectively applied to the AND circuit 32. The waveform e is synchronized with the interrogation signal when the level of the interrogation signal from the onboard interrogator exceeds a predetermined level, and is synchronized with the pulse sent as a response pulse after the interrogation signal is decoded by the ground receiver. It is. Normally, the predetermined level is assumed to be the case when the aircraft approaches the final landing approach area, and in the case of this embodiment, the ground station is set when the aircraft approaches the landing point within 5 to 10 nautical miles. It is set to the level of the interrogation signal from the aircraft interrogator to be received, and level detection can be easily performed by using a generally well-known logarithmic amplifier or the like.

In this way, the pulse g outputted from the AND circuit 32 is only a response pulse corresponding to the interrogation signal from an aircraft preparing for final landing approach, even if the ground station receives an inquiry from an unspecified number of aircraft over a wide area. be. Pulse g is applied to the S (set) terminal of R-S flip-flop 33, and the output is set to logic 0 at the rising edge of pulse g. Therefore, the output waveform h of the R-S flip-flop 33 is set at the rising edge of the response pulse (waveform g) selected by the AND circuit 32, and is set at the rising edge of the response pulse (waveform g) selected by the AND circuit 32, and is set by the pulse of the 1350 Hz pulse train (waveform f) that has passed through the delay circuit 31.
It will be reset. The output of the R-S flip-flop 33 lags behind the response pulse g.
In order to suppress the pulses of the 1350Hz pulse train, it is applied to the AND circuit 34 and outputs the suppressed pulse train i. The response pulse (waveform g) and the pulse train (waveform i) resulting from suppression of the 1350Hz pulse train by the response pulse pass through the OR circuit 35, and when transmitting the station identification code, part of the station identification code pulse train becomes the response pulse. It is possible to obtain a waveform j replaced by . The output of the OR circuit 35 is input to a keying circuit 36 shown in FIG. 2, and a transmission pulse output k is obtained.

The output of the keying circuit 36, that is, the output pulse of the priority gate 27, is re-encoded into paired pulses in the coder 29 as shown in FIG.
The encoded pair of pulses passes through a transmitter 30 and a duplexer 22, and is emitted from the hollow wire 21 as an RF pulse. Therefore, the onboard interrogator can receive signals from the ground equipment, detect response signals synchronized with its own interrogation, and measure the distance to the ground station.

As explained above, according to the present invention, an aircraft preparing for a final landing approach can receive accurate and real-time distance information even when the ground station transmits the station identification code at predetermined time intervals. It can be obtained without being affected in any way, and has the effect that the station identification code can be sufficiently confirmed.

[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 in each part of 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 at various parts in FIG. 21...Aerial line, 22...Duplexer, 2
3...Receiver, 24...Decoder, 25...1350
Hz pulse generator, 26...Keyer, 27...Priority gate, 28...Comparator, 29...Coder, 30...Transmitter, 31...Delay circuit, 3
2, 34...AND circuit, 33...R-S flip-flop circuit, 30...keying circuit.

Claims (1)

[Claims] 1 After receiving the interrogation pulse sent from the interrogator, the transponder sends out a response pulse corresponding to the interrogation pulse and a station identification code pulse train consisting of a Morse code for identifying the transponder, and the interrogator receives the interrogation pulse. In a distance measuring device that measures the distance between two by measuring the time from transmission to reception of a response pulse, when the received interrogation pulse is above a predetermined level, priority is given to the response pulse corresponding to this interrogation pulse. A distance measuring device characterized by transmitting a signal.