JP5414575B2 - Distance measuring apparatus and squitter generation method - Google Patents

Description

  The present invention relates to a distance measuring apparatus and a squitter generation method for transmitting and receiving a squitter to and from an aircraft in order to grasp the position of the aircraft.

  An aircraft flies while specifying its position by various methods, and there is a method of using a distance measuring equipment (DME: Distance Measuring Equipment) for specifying a flight position. When a distance measuring device (DME) is installed on the ground and receives an interrogation pulse transmitted from an aircraft, it transmits a response pulse to the aircraft in response to the received interrogation pulse. In an aircraft, a flight position is specified using transmission and reception of pulses with a distance measuring device.

  The aircraft transmits an interrogation pulse P1, as in the example shown in FIG. The distance measuring device that has received the interrogation pulse P1 transmitted from the aircraft transmits a response pulse P2 that responds to the interrogation pulse P1 to the aircraft after a predetermined time (Td) has elapsed since the interrogation pulse P1 was received. To do. When the aircraft receives the response pulse P2 transmitted from the distance measuring device, the aircraft obtains the response time T obtained from the transmission time t1 of the interrogation pulse P1 and the reception time t2 of the response pulse P2, and the transmission speed of the radio wave (signal). Based on this, the distance from the distance measuring device to the aircraft is measured.

  The inquiry pulse P1 and the response pulse P2 transmitted / received here are twin pulses, and internationally, for example, a pulse interval and a delay interval for each operation mode are defined (see Non-Patent Document 1, for example). For example, in the DME / N mode, the interrogation pulse P1 and the response pulse P2 have a pulse width of 3.5 μs and a pulse interval of 12 μs.

  In addition to transmitting the response pulse P2, the distance measuring device is obliged to transmit a squitter pulse at random instead of the response pulse P2 when the transmission rate of the response pulse P2 is low (for example, Patent Document 1). reference). At this time, the distance measuring device 1 needs to transmit the squitter pulse at random timing so that the sitter pulse is not determined to be the response pulse P2 by the aircraft (side).

  In order to randomize the transmission of the squitter pulse, the conventional distance measuring apparatus generates squitter using thermal noise generated in an analog circuit. However, when thermal noise generated in an analog circuit is used, there is a problem that it is easily affected by external noise and the squitter pulse transmission timing pattern is not reproducible. For example, when there is no reproducibility in the transmission pattern of the squitter pulse, it becomes difficult to use for the test of the distance measuring apparatus.

  On the other hand, in the technique described in Patent Document 1, the transmission timing of the squitter pulse is determined using a shift register that is a digital circuit. When the transmission pattern of a squitter pulse is determined using a digital circuit as described in Patent Document 1, it becomes difficult to receive external noise and the transmission pattern of the squitter pulse can be made reproducible. .

  However, when distance measuring devices that use the same shift register are close to each other, there is a possibility of interference as harmonics (harmonics) because they are squitter pulses of the same transmission pattern.

JP 2008-298596 A

“Aeronautical Telecommunications, ANNEX10, VOLUMEI”, July 1996, pages 27-40, ICAO

  As described above, the method of generating the squitter pulse using the thermal noise generated in the analog circuit is easily affected by the external noise and difficult to evaluate the test. The squitter pulse using the shift register which is a digital circuit is difficult. In the method of generating, there is a risk of interference during actual operation, and there may be a problem during testing before installation or during operation after installation.

  Accordingly, the present invention provides a distance measuring apparatus and a squitter generation method that generate an appropriate squitter pulse during a test before installation and during operation after installation with a simple apparatus configuration.

  When the distance measuring device according to the present invention receives an interrogation pulse transmitted from an aircraft, the distance measuring apparatus transmits a response pulse that responds to the interrogation pulse, and at the timing of not transmitting the response pulse for a predetermined period, A distance measuring device for transmitting a squitter pulse, wherein a transmission timing for transmitting a squitter pulse of a predetermined transmission pattern is generated at a timing at which a response pulse is not transmitted for the predetermined period, and a squitter pulse is transmitted at a timing at which a query pulse is received A squitter generator for updating a pattern, and a pulse generator for generating a pulse to be transmitted at a timing at which an interrogation pulse is received or a transmission timing generated by the squitter generator.

  According to the present invention, it is possible to generate an appropriate squitter pulse at the time of test evaluation and operation with a simple apparatus configuration.

It is a figure explaining the distance measuring device which concerns on best embodiment of this invention. It is a figure explaining the squitter generator of the distance measuring apparatus of FIG. It is a figure explaining the pulse transmitted / received by an aircraft and a distance measuring device.

  A distance measuring device (DME) 1 according to the best embodiment of the present invention will be described with reference to FIG. The distance measuring device 1 is installed in a ground station, detects a query pulse P1 of a predetermined pulse pair transmitted from a transponder provided in an aircraft, and transmits a response pulse P2 in response to the query pulse P1. Here, the response pulse P2 transmitted by the distance measuring device 1 is also a signal having the same pulse waveform (pulse pair) as the interrogation pulse P1. When the aircraft that has transmitted the interrogation pulse P1 receives the pulse pair signal, it determines whether or not it is a response pulse P2 for the aircraft, based on the interval and correlation from the transmission of the interrogation pulse P1 to reception of the pulse pair.

  Specifically, as shown in FIG. 1, the distance measuring apparatus 1 includes an antenna 10, a circulator 11, and an RF amplifier 12 that receives and amplifies a signal (RF signal) received by the antenna 10 via the circulator 11. A mixer 13 that mixes an RF signal of a predetermined frequency output from the oscillator 14 and the received signal to generate an IF signal of an intermediate frequency, and a detector 15 that detects a signal level from the received signal mixed by the mixer 13. A detector 16 that detects the pulse pair that is the interrogation pulse P1 from the signal level detected by the detector 15, a response generator 19 that generates a signal at the timing of transmitting the response pulse P2, and an output from the response generator 19 A pulse generator 20 for generating a pulse pair according to the received signal, and a pulse pair signal output from the pulse generator 20 and a transmitter A mixer 21 that mixes the RF signal of a predetermined frequency output from 2 and converts it to an RF signal, and an RF amplifier 23 that amplifies the signal mixed by the mixer 21 and transmits the amplified signal via the circulator 11 and the antenna 10. I have.

  In addition, when the transmission rate of the response pulse P2 is equal to or lower than the predetermined value, the distance measuring device 1 has the same random transmission pattern as the response pulse P2 so as to satisfy a predetermined transmission rate (for example, 1000 pps) separately from the response pulse P2. Sends a squitter pulse with a pulse waveform. Therefore, the distance measuring device 1 includes a squitter generator 17 and an OR circuit 18.

  The squitter generator 17 inputs an RX trigger (RXTr) at the timing when the interrogation pulse P1 is detected from the detector 16. Further, the squitter generator 17 outputs a squitter trigger (STr) by obtaining the timing for transmitting the squitter pulse when the response pulse P2 is not transmitted at a predetermined rate, that is, when the interrogation pulse P1 is not received for a predetermined period.

  The OR circuit 18 inputs and outputs the timing for transmitting the response pulse P2 or the squitter pulse. Specifically, the OR circuit 18 inputs an RX trigger from the detector 16 at the timing of receiving the interrogation pulse P1, that is, the timing of transmitting the response pulse P2, and inputs the squitter trigger at the timing of transmitting the squitter pulse. Therefore, the OR circuit 18 outputs a TX trigger (TXTr) that specifies the pulse transmission timing when either the RX trigger or the squitter trigger is input. Thereby, the response generator 19 can transmit the response pulse P2 or the squitter pulse.

  As shown in FIG. 2, the squitter generator 17 includes an OR circuit 171, a timer 172, a random number generator 173, and a frequency divider 174. The timer 172 is cleared by a TX trigger input from the OR circuit 18 and outputs a signal after a predetermined time determined based on the transmission rate of the response pulse P2. The OR circuit 171 outputs the operation result of the RX trigger input from the detector 16 and the signal input from the timer 172 to the random number generator 173 and the frequency divider 174.

  The random number generator 173 is a shift register such as an LFSR (linear feedback shift register). When a signal from the RX trigger or the timer 172 is input, the clock is advanced to obtain a random number, and this random number is squitter-pulsed. Output as the transmission timing (pulse distribution). For example, when the inquiry pulse P1 is not received, a signal is output from the timer 172 every predetermined time, the clock of the random number generator 173 is advanced, and the transmission timing of the squitter pulse is specified.

  Therefore, while the distance measuring apparatus 1 does not receive the interrogation pulse P1, the transmission timing of the squitter pulse output from the random number generator 173 is a repetition of a known pattern unique to the LFSR. On the other hand, when the distance measuring apparatus 1 receives the interrogation pulse P1, the RX trigger is input and the clock of the random number generator 173 changes, so that the transmission timing of the squitter pulse also changes. It will be different. At this time, the shift register used for the random number generator 173 uses an LFSR whose sequence has been verified and has a sufficiently long period (for example, one having a longest period of 16 bits or more).

  The frequency divider 174 divides the timing input from the random number generator 173 by a frequency division ratio determined according to the transmission rate of the predetermined response pulse P2, and outputs the result as a squitter trigger. The frequency divider 174 also advances the clock when a signal from the RX trigger or timer 172 is input. That is, while the distance measuring apparatus 1 does not receive the interrogation pulse P1, the LRSR changes every predetermined period timed out by the timer 119. However, when the interrogation pulse P1 is received, the LRSR is input by inputting the RX trigger. Change.

  Since the output of the random number generator 173 is 1 (or 0) with a probability of 1/2, when the target rate is 1000 pps, for example, the timer is set to 250 μs (1/4000 seconds) and the division ratio is set to 2. Can do. That is, 250 μs × (2 + 2) = 1000 μs = 1/1000, which is 1000 pps.

  Further, when the frequency is halved by a frequency divider, the total becomes four times. Therefore, the timer can be set to 125 μs (1/8000 seconds) and the frequency division ratio can be set to 4. That is, 125 μs × (4 × 2) = 1000 μs = 1/1000, which is almost 1000 pps.

  As described above, in the distance measuring apparatus 1 according to the present invention, the transmission pattern determined by the shift register of the pure random number generator 173 when the interrogation pulse is not received by the squitter generator 17 (when no RX trigger is input). Can generate a squitter pulse, and the pulse distribution and appearance probability (transmission pattern) of the squitter pulse can be known. Therefore, by suppressing the RX trigger in a test environment or the like before the distance measuring device 1 is installed on the ground station, it is possible to reliably test and monitor the generation state of the squitter pulse and the operation of the distance measuring device 1. .

  Further, when the distance measuring apparatus 1 is operated after being installed on the ground station, the RX trigger is input by the reception of the inquiry pulse P1 and the clock of the random number generator 173 is advanced, so that the transmission pattern of the generated bit string, that is, the squitter pulse changes Therefore, even when the same type of distance measuring device exists in the vicinity, the possibility of interference is extremely low.

  Therefore, the above-described distance measuring apparatus 1 can transmit an appropriate squitter pulse even in the test environment before being installed in the ground station or during operation after being installed in the ground station.

DESCRIPTION OF SYMBOLS 1 ... Distance measuring device 10 ... Antenna 11 ... Circulator 12 ... RF amplifier 13 ... Mixer 14 ... Oscillator 15 ... Detector 16 ... Detector 17 ... Sitter generator 171 ... OR circuit 172 ... Timer 173 ... Random number generator 174 ... Frequency division 18 ... OR circuit 19 ... Response generator 20 ... Pulse generator 21 ... Mixer 22 ... Transmitter 23 ... RF amplifier

Claims (4)

When the interrogation pulse transmitted by the aircraft is received, a response pulse that responds to the interrogation pulse is transmitted, and a squitter pulse of the same format as the interrogation pulse is transmitted at a timing when the response pulse is not transmitted for a predetermined period. And
Generating a transmission timing for transmitting a squitter pulse of a predetermined transmission pattern at a timing at which a response pulse is not transmitted for the predetermined period, and a squitter generator for updating a transmission pattern of the squitter pulse at a timing of receiving a query pulse;
A pulse generator for generating a pulse to be transmitted at a timing at which an interrogation pulse is received or a transmission timing generated by the squitter generator;
A distance measuring device comprising: The squitter generator is
A timer for determining whether or not a predetermined period has elapsed after transmitting a response pulse or a squitter pulse;
Random number generating means for generating a random number for specifying a transmission pattern of a squitter pulse at a timing at which a query pulse is received or at a timing at which a predetermined period has elapsed after transmitting a response pulse or squitter by the timer;
The distance measuring device according to claim 1, comprising: 3. The distance measuring apparatus according to claim 2, wherein the squitter generator includes a frequency divider that divides a random number specified by the random number generation unit to obtain a transmission timing of a squitter pulse. When an interrogation pulse transmitted by an aircraft is received, a response pulse that responds to the interrogation pulse is transmitted, and a distance measurement device that transmits a squitter pulse in the same format as the interrogation pulse at a timing when the response pulse is not transmitted for a predetermined period. A pulse generation method, comprising:
Generating a transmission timing for transmitting a squitter pulse of a predetermined transmission pattern at a timing at which a response pulse is not transmitted for the predetermined period;
Updating the transmission pattern of the squitter pulse at the timing of receiving the interrogation pulse;
Generating a pulse to be transmitted at the timing of receiving the interrogation pulse or the transmission timing of the squitter pulse;
A squitter generation method comprising:

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