JPS6018018B2 - distance measuring device - Google Patents

Description

[Detailed description of the invention] The present invention relates to a distance measuring rhombus.

MLS (Microwave Indin Bookys [em:
distance measuring equipment (DME), etc.
, DjstameMeasurjngEquipmen
In t), the interrogator (e.g., an aircraft) that requests distance measurement generally sends out a radio wave modulated with a pulse waveform, which is received by a transponder on the other side (e.g., a ground station), and is then delayed for a certain period of time and then reshaped as a pulse. Send again.

On the side requesting distance measurement (aircraft), a method is used in which the distance between pulses is determined by measuring the pulse delay time from transmission to reception. The pulse waveform used as an international standard in such DME is a pseudo-Gaussian waveform. A Gaussian waveform has the property that its spectrum is also a Gaussian waveform (that is, a Gaussian waveform on the time axis that is Fourier transformed is also a Gaussian waveform on the frequency axis).
It has the advantage of being able to concentrate the spectrum within a relatively narrow band, but if you try to use this to determine accurate timing (pulse position), you will encounter the following problem. A problem arises. Generally, to determine the pulse position pupil, as shown in Figure 1, if the peak voltage of this waveform is A, select A2 as the threshold voltage.
This is done by measuring the point at which the rising waveform of the received signal exceeds this threshold pressure.

As shown in Figure 2, the pulse waveform for DME currently internationally defined and used has a rise time of 2.5 French S (reference value) from 10% to 90%. Inside is a Gaussian waveform of 3.5±0.5&S.

However, this Gaussian waveform has a relatively gentle slope at the 50% value used to measure the timing, so if the threshold fly pressure changes for some reason, the above timing The shift in the time axis direction becomes large, resulting in a large distance error.

In particular, when the distance to be measured is from 0 to 20 M (nautical miles) and the reception level is set to 6, it is difficult to accurately detect the midpoint of the 1'2 swing under conditions where there is no dynamic bell fluctuation than the old one. However, it is also easily affected by noise, etc. Also,
The timing detection point in the 1'2 axis mentioned above is located at a point about 1.25 peaks S behind the rising edge of the waveform, so it is susceptible to the influence of reflected waves in the radio wave propagation path.

In other words, all reflected waves within 1.25 μS (approximately 375 mm in distance) behind the main wave overlap the timing detection point of the main wave and affect the voltage at that point. As mentioned above, in combination with the gentle slope of the waveform timing detection point, this results in a relatively large error in distance measurement. However, it is impossible to satisfy the required accuracy for future all-weather landing aid systems, which require high measurement accuracy. proposals have been made.

One of them is delay comparison (lay and Com), which has been proposed as a means to prevent deviations in pulse timing detection caused by changes in threshold voltage.
pare (hereinafter abbreviated as DAC).

This is done by dividing the detected received wave into two and passing the toe through an attenuator to attenuate it by a certain amount (A
Double A < 1) "If we delay the other by a certain amount (Dsec) through a delay circuit and then use a comparator to calculate the difference between the two (subtract the former from the latter), the output of the comparator will be As shown in the turtle diagram, there is a sharp drop to 0 at the intersection of both waveforms.
The waveform crosses the level. If the point in time when this 0 level is crossed is used as the timing point of the pulse, this timing point is only the shape of the pulse and has no relation to the magnitude of the vibration during the constant vibration. Therefore, even if the above-mentioned values of A and D are appropriately selected according to the waveform to be used, the error caused by the above-mentioned threshold voltage fluctuation can be greatly reduced by specifying the most appropriate detection point for that waveform. can be improved. However, even if you use the DAC explained above, the influence of the input sound and the reflected waves on the radio wave propagation mentioned above will be
"These effects cannot be avoided because they appear as changes in the AC input waveform itself.

Therefore, a method was proposed in which the pulse waveform used was made into a waveform more suitable for distance measurement than the Gaussian waveform described above.

A waveform proposed for this purpose is the "cos-cos2'〇 waveform shown in FIG. This is a cosine function (cos(-9) as the waveform of the rising part.
0o) to COS(oo)), and the waveform of the falling part is a cosine square function (cos2(
oo) to cos2 (90o)). By appropriately selecting the period of the cosine waveform in the rising portion and the period of the cosine binary waveform in the falling portion, a waveform conforming to the international standard is obtained. Since this waveform is almost a straight line near its rise, the above-mentioned D
By selecting the timing detection point of the AC waveform near its rising point, it can be used as a highly accurate distance measurement pulse with less error due to the influence of the reflected wave of the crab wave propagation path. However, "This waveform has a discontinuity point in its first order slope at the first rising point (the first derivative of the waveform jumps from 0 to a finite value at the rising point of the waveform). This has the disadvantage that the degree of attenuation of the spectrum at frequencies far away from the carrier frequency is degraded, that is, the spread of the spectrum is increased.

The next thing that was proposed was the above-mentioned “cos-cos2”.
This method uses a "cos2-cos2" waveform instead of a waveform.

This converts the rising part of the “cos-cos2” waveform from the cosine (COS) function mentioned above to the cosine 2 plan function (co
s2 (-90o) to cos2 (oo)). This is also the “cos-co”
Similarly to the s-starved waveform, a pulse waveform conforming to the international standard is obtained by appropriately selecting the period of the cosine 2 function in the rising part and the period of the cosine square function in the falling part. Since this waveform has no discontinuity in the primary rear slope at the rising point, the attenuation of the spectrum at frequencies far from the carrier frequency becomes large. Since a steep point (inflection point of the rising waveform) occurs at the 50% value of the waveform, the time from the starting point to the detection point is longer, and as mentioned earlier, this is due to reflections in the radio wave propagation path. It has the disadvantage of being easily affected by waves. SUMMARY OF THE INVENTION An object of the present invention is to provide a highly accurate distance measuring device that eliminates these drawbacks of conventional distance measuring devices.

- The distance measuring device of the present invention detects from the interrogator that the front edge of the envelope shape of at least one pulse has an inflection point just before the half value of the peak value of the pulse, and has a primary mirror slope of the rising part. A pair of interrogation pulses having a continuous specific shape are transmitted, and after the transponder detects the timing calendar of the pulse having the specific shape among the interrogation pulses received by the receiving system, A pair of response pulses in which the leading edge of the envelope shape of at least one of the pulses has the specific shape are transmitted, and the interrogator detects the timing error of the pulse having the specific shape among the response pulses received by the receiving system. After that, the time from the sending of the interrogation pulse to the reception of the response pulse is measured based on the timing error, thereby establishing the basis for measuring the distance between the interrogator and the transbonder. Next, embodiments of the present invention will be described in detail with reference to the drawings.

In the present invention, as described above, the drawbacks of the "cos-cos2" pulse waveform and the "cos2-cos2'' pulse waveform are alleviated, and a new pulse waveform that combines the advantages of both is applied to the distance measurement machine. In other words, the steepest point (inflection point) of the rising slope in the front green part of the pulse waveform is repositioned temporally earlier than the half-value part of the peak value of the pulse, and the primary point of the rising slope of the pulse waveform is A waveform in which the slope is continuous (hereinafter referred to as DATE (Damped Tram)
ient edge) (referred to as Gaussian waveform). It should be noted that normally distance measurement measuring (DME) pulse pairs are used with a constant interval (12, 30 or 36 seconds), the first pulse of which is used to determine the time point of distance measurement.

Since the second pulse is used to identify whether the received pulse is a correct pulse for distance measurement, it is not necessary to use the DATE Gaussian pulse, but rather a conventional pseudo-Gaussian waveform. It is desirable to suppress the spread of subectrum as much as possible by using An embodiment of the distance measuring device according to the present invention is shown in FIG.

In the figure, 1 indicates a pulse generator which also generates the DATE-Gaussian waveform and, when a conventional pseudo-Gaussian waveform is used as the second pulse, this pseudo-Gaussian waveform, and the time point specified by the transmission timing signal from the time controller 2. The above pulse is output every time. The transmission pulse generated from the pulse generating section linearly modulates the carrier in the modulating section 3, increases the power of the carrier in the power increasing section 4, and sends it out from the antenna 6 to the other party via the diplexer 5. .

On the other party's side (transponder side), as shown in FIG.
The intermediate frequency intensifier section 18 selects only the received waves of the necessary channels, and the intermediate frequency intensifier section 18 selects only the received waves of the necessary channels.
At step 9, the received waveform is linearly detected, its envelope vertical line is extracted and zeroed, and the pulse timing of the first pulse of the received wave is determined at the DAC section 20 by the method explained in FIGS. 3 and 4. Then, using this timing as a reference, the control unit 22 sets the timing of the retransmission pulse (response pulse) that is delayed by a certain period of time (generally 50 microseconds), and has the same configuration as explained in FIG. 6. It is sent to the transmission system 21 to generate a retransmission pulse in the same manner as described above, and re-radiates it into space. On the side that requested the first distance measurement, this re-radiated signal is used in a receiving system 7 having a configuration similar to that of the receiving side explained in FIG. 7 to determine the reception timing of the first received pulse. The distance is measured by comparing this reception timing with the transmission timing in the time control section 2. Also, instead of the circuit shown in Figure 3, the input wave is divided into two parts, one of which is applied directly to one input of the comparator, and the other is applied to the delay circuit and then to the multiplier before being applied to the other input of the comparator. Even in the configuration where it is added to the input of Figures 3 and 4,
The DAC operation can be performed in exactly the same manner as explained using the figures.

In this case, considering that the intersection point will vary due to noise, it is better to select the straight line part of both waveforms as the intersection point and prevent the error from leaning in one direction when variation occurs. It should be obvious. DA mentioned above
The circuit that generates the TE-Gaussian waveform includes a circuit that directly generates an analog signal using a capacitor, coil, and resistor, and a memory that can digitally read out sample values of the desired pulse waveform calculated at each appropriate sampling point at high speed. For example, the written information is written to a read-only memory (ROM), read out at a required sampling rate, converted to an analog signal through a D/A converter, and further converted into an analog signal that is 1/1/2 of the sampling frequency. A circuit can be considered in which a desired pulse waveform is obtained by passing the pulse through a low-frequency wave generator having a band width below a.

An example of the former circuit is shown in FIG.

In Figure 8, C is a capacitor, R,, R2 are resistors, and L
, L indicates a coil, E, , E2 indicates a DC power supply, and S indicates a changeover switch. Assuming that the initial condition is that the charge on C is 0 (that is, the output voltage at point P is 0) and the switch S is connected to the contact on the L side at time t = 0, the output voltage VR (T) at point P is In general, VR (T) White E・[1-1 Tsume Temo Genzai FEXp (1-1-V Ryo-4F T) 11th word reed poison damage FEXP (-10Y1 Kotobuki 4FT)]・--[1 ).

Here, T is the time standardized by CR (i.e., T=t
/CR,) Also, F=L, /CR,2. This equation becomes an equation that includes a complex number when the value of F becomes larger than 1/4, but the resulting VR(T) is always a real number.

For reference, this can be expressed as an expression that does not include complex numbers as follows. (i) Same as formula {1} in the range 0<F<1/4.

(The formula in which the values below are limited to this range will be referred to as formula (1') hereafter to distinguish it from formula '1).) (ii] F=1
/4, VR (T) = E, [1 - (1 10 illusions) EXP (1 2 T)] ... [21 Gii) In the range of F > 1/4, 10 VR (T) = E, [1 - {c.

s (Y4 Mon [IT) Y Siou; Sin (〉4F is middle 1T
)} EXP (Skilled LT)]...'The above including three complex numbers'
1} expression can be considered to include expressions (1'), [21}, and '3}, which are expressions that do not include a post-prime number.

Now, the VR(T) given in this way generally rises from the 0 level at T=0, but the value of VR(T) is either the first peak value determined by the value of F, or - or very close to the peak value. When the value is reached, the switch S is switched from the L side to the - side.

For example, if the influence of R2 is selected to be so small that it can be ignored, the voltage at the output point P will be approximately v'F
(t') Pre (state OS original sales band). - Generates the voltage waveform given by the side (the time used here is not standardized like T above), so by appropriately selecting E2, it can be connected continuously with the rising waveform and softly Make it touch the 0 level (first point at the 0 level)
(so that the differential coefficient of the order becomes 0).

In this way, when the falling waveform falls to the 0 level, the switch S is disconnected from the ON side. Although a single peak pulse waveform can be created by the method described above, the waveform obtained in this way is defined as a DATE-Gaussian waveform.

The rising part of this waveform (front green) is the VR of the above equation (1).
It can be expressed by a function (T). FIG. 9 is a diagram showing a typical example of the DATE-Gaussian waveform defined in this way and its spectrum. FIG. 10 is a diagram showing details of the vicinity of the rising point of the waveform. This D
For the ATE-Gaussian waveform, set F in equation '1) to F=10/
It is a waveform with a pre-rise green of 112, and CR,
= (112/260)〃S, that is, T = (260/
112) If t is the axis of the machine in real time t (unit: S), then the rising leading edge becomes a function of real time t as shown below.

VR(t) = 1 first class insect
At about 15% of the peak value of the waveform, there is an inflection point where the slope becomes ergonomic.

For reference, Fig. 11 shows the cos-cos2'1 pulse waveforms with the same rising slope and their spectrum. Table 1 also shows the spectrum of these waveforms with ±0 Here is a table showing the attenuation of the spectrum measured in the 0.9 MHZ band at .
“COS” whose E-Gaussian waveform has the same rise and slope
This shows that the DATE-Gaussian waveform obtained in this way has excellent properties as shown in Table 1.

This waveform is essentially soft in its rise point.

That is, the first-order differential of the rising point of this DATE-Gaussian waveform is [d group h] T= for any F>0.
=. becomes.

Therefore, the primary slope of the rising point is continuous, and there is no discontinuity as seen in the above-mentioned "cos-cos2''. This has a favorable effect in suppressing the spread of the spectrum. Also, For this DATE-Gaussian waveform, the steepest point of the rising slope (inflection point of the rising waveform) can be freely selected at any point within approximately 50% of the waveform.In other words, the value of F mentioned above can be set to 0. As the value of F approaches , the inflection point of the waveform approaches the 0 level, and as the value of F increases, the inflection point approaches the 50% value. If we find the inflection point in the case of F = 1/4 (the case expressed by the above equation '2) at the boundary where the waveform transfers to the damped vibration transient waveform, it is approximately 26%.In other words, the inflection point is approximately 26%. % or less, the DATE-Gaussian waveform will have a non-oscillatory transient waveform with a rise expressed by the formula (〇).As mentioned above, when detecting the timing of the received waveform using the DAC method, the detection It is most preferable to select the point at a steep part of the waveform rise (an inflection point of the rise waveform), and considering the effect of reflection on radio wave transmission mentioned above, this timing detection part should be selected as close to the rise as possible. A point is desirable.The above “cos2-cos2”
In the waveform, this inflection point was fixed at the 50% value, whereas in the DATE-Gaussian waveform, the inflection point can be set to any value less than 50%, as shown above. is possible. Therefore, by setting the inflection point of the waveform near the rising point and selecting the timing detection point by the DAC near this inflection point, it is possible to greatly reduce the influence of reflected waves on the radio wave transmission path mentioned above. . As detailed above, the DATE-Gaussian waveform has many advantages as a pulse for high-precision distance measurement, but it is also suitable for distance measurement devices using Gaussian pulses, which are currently widely used. It can also be made compatible.

In other words, by adjusting the 50% value to the current standard value, it is possible to sufficiently secure the accuracy required in the past through the transmission band of the conventional hawk, and the spread of the spectrum can be adjusted to other channels. It is also possible to suppress the noise given to the device to below the standard value. Note that in conventional equipment, the channel separation of the DME system is
Since it is MHZ, a relatively narrow band receiving system is used to eliminate interference signals from adjacent channels, but in the present invention, a narrow band receiving system 30 is used as shown in FIG. In addition, when it is necessary to separately install a wideband receiving system 31 to remove interference from adjacent channels, or for long-distance measurements that cannot be detected by the wideband receiving system due to noise, the narrowband receiving system 30 is used. If high accuracy is required, such as when used as an aid device, there are few adjacent channels, and high accuracy is required, switch to the wideband receiving system 31 and use a DA with a steep rise within a distance that requires high accuracy.
It is also possible to adopt a configuration that performs high-precision distance measurement that takes full advantage of the characteristics of the TE-Gaussian waveform. As described above, by using the distance measuring device according to the present invention, it is possible to perform highly accurate distance measurement which is compatible with conventional diamond counterfeiting and has less influence of reflected waves on mother wave propagation.

Simple explanation of the drawings Figure 1 is an explanatory diagram of timing measurement using pseudo-Gaussian pulses, Figure 2 is the pulse waveform for DME (Distance Measuring Diamond), which is currently internationally defined and used. 3 is a diagram showing the configuration of a delay comparison circuit (DAC),
FIG. 4 is a diagram explaining the output of the comparison circuit when determining the waveform timing using a DAC, and FIG.
-cos2'' waveform, FIG. 6 is a block diagram showing an embodiment of the distance measurement requesting side of the distance measurement device of the present invention, and FIG. 7 is a transponder of the distance measurement device of the present invention. A block diagram showing one embodiment of the side, FIG. 8 is a DAT
FIG. 9 is a diagram showing a circuit for generating an E-Gaussian waveform, and FIG. 9 is a diagram showing an example of calculation of a DATE-Gaussian waveform.
FIG. 10 is a diagram showing the details of the vicinity of the rising point of the DATE-Gaussian waveform, and FIG. 11 is "cos-cos2".
A diagram showing an example of waveform calculation and FIG. 12 are block diagrams showing an embodiment of the distance measuring bag counterfeit receiving section of the present invention.

In Fig. 6, Fig. 7 and Fig. 12, 1...D
ATE-Gaussian waveform generation section, 2... Time control section, 3... Modulation section, 4... Power increase section, 5
... Dibrexa, 6 ... Aerial line, 7
...Receiving system, 15...Transponder side diplexer, 16...Transponder side antenna, 17...
...Transponder side preselector, 18...Transponder side intermediate frequency intensifier, 19...Transponder side detection section, 20...Transponder side DAC
Part, 21... Transponder side transmission system, 22...
. . . Transponder side control unit, 30 to . . . Narrowband reception system, 31 . . . Wideband reception system.

Many 3 figures That/meat Many 2 drawings Many 4. figure group, group umbrella. 6 Figure fin 7 is l Diamond 8 Hiiragiku map ticket//figure *'2 style More diagrams

Claims (1)

[Claims] 1. From the interrogator, the leading edge of the envelope shape of at least one of the pulses has an inflection point before the half-value position of the peak value of the pulse, and the primary slope of the rising part is continuous. A pair of interrogation pulses having a specific shape are transmitted, and after the transponder detects the timing position of the pulse having the specific shape among the interrogation pulses received by the receiving system, at least one of the pulses is transmitted after a predetermined time delay from this timing position. After transmitting a pair of response pulses in which the front edge of the envelope shape has the specific shape, and the interrogator detects the timing position of the pulse having the specific shape among the response pulses received by the receiving system, A distance measuring device characterized in that the distance between the interrogator and the transponder is measured by measuring the time from the time of pulse transmission to the reception of the response pulse from the timing position. 2. In claim 1, the specific shape of the interrogation pulse and the response pulse is such that E and F are positive numbers, and T
If time is E[1-(1+√(1-4F))/(
2√(1-4F))EXP(-(1-√(1-4F))
/(2F)T)+(1-√(1-4F))/(2√(1
-4F))EXP(-(1+√(1-4F))/(2F
)T)] A distance measuring device characterized by having a shape approximated by 3. A distance measuring device according to claim 1, wherein the interrogator and transponder receiving systems are comprised of a wideband receiving system and a narrowband receiving system that can be selectively switched and used. 4. In claim 1, the means for detecting the timing position of the pulse in the interrogator and the transponder divides the received pulse into two, delays one by a predetermined amount of time, and attenuates the other by a predetermined amount, and then A distance measuring device comprising means for subtracting one of an output and a damped output from the other, and setting a position near an inflection point of the specific shape portion of the subtracted output as a timing position.