JPS61137085A - Loran c receiver - Google Patents

Abstract

PURPOSE:To simplify operation by automatically selecting an always optimum suboffice combination even if a receiving state changes by movement, by selecting a plurality of suboffice loran C signals usable in the calculation of a present position on the basis of the present position and the position of each suboffice. CONSTITUTION:The loran C signal received by a receiving antenna 10 is amplified by a high frequency amplifier 12 and converted to a square wave by a limiter circuit 14 to be binarized while the binarized one is latched by a latch circuit 16 to be sent to a data bus 28. The sampling pulse of the loran C signal is added in CPU20 to perform the initial collection processing of a master station and a suboffice and the third cycle of a loran pulse is subsequently detected. The S/N ratio of the third cycle is measured to select the suboffice usable in the calculation of a present position. After the combination of suboffices is automatically selected in the order well in a receiving state, the calculation of the present position is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to radio navigation receivers, and more particularly to Loran C receivers.

(Background technology) Regarding this type of device, Japanese Patent Application Laid-Open No. 54-105494.5
No. 4-153594 is known, and in this type of device, it is necessary to set in advance the combination of slave stations used for position detection.

This setting is done when the receiving status of the slave station Loran C signal changes as the user moves or when the receiver is initially started up, but in conventional devices, this setting is done manually.
For example, when moving, it is necessary to check the reception status, check the currently available slave stations from the Loran C table, etc., and set the combination of slave stations determined based on them on the receiver, which is a complicated operation. It was inconvenient.

(Object of the invention) ゛The present invention has been made in view of the above-mentioned conventional problems,
The purpose is to provide a highly operable Loran C receiver that can automatically set the optimal combination of slave stations for position detection.

(Summary of the Invention) In order to achieve the above object, the present invention selects a plurality of slave station Loran C signals that can be used to calculate the current position based on the current position and the position of each slave station, and combines these slave station Loran C signals with It is characterized by determining the current position based on the main station Loran C signal.

Therefore, in the device according to the present invention, as shown in FIG. 1, the Loran C signals of the main station and each slave station are received by the receiving means a, and can be used to calculate the current position based on the current position and the position of each slave station. A plurality of slave station Loran C signals have been selected by the signal selection means, and the current position is determined by the current position calculating means C based on the selected slave station Loran C signals and the master station Loran C signal.

(Embodiments of the invention) Preferred embodiments of the apparatus according to the present invention will be described below based on the drawings.

In FIG. 2, a Loran C signal received by a receiving antenna 10 is amplified by a high frequency amplifier 12, and the amplified signal is converted into a square wave by a limiter circuit 14 and then binarized.

The binarized data is supplied to the latch circuit 16,
A trigger signal is supplied to this latch circuit 16 from a preset counter 18 .

Further, an interrupt trigger signal is supplied from the preset counter 18 to the interlaced input of the CPL 720, and the address bus 22 is supplied with the RAM 24. ROM26
．． The preset counter 18 is connected to the data bus 28, and the RAM 24. ROM26. Preset counter 1B.

A latch circuit 16 is connected.

The count number of the preset counter 18 is determined by the CPU 20.
The preset counter 18 can divide the clock signal of the clock generation circuit 30 and generate it as a trigger signal.

Further, the latch circuit 16 can latch the binary data of the Loran C signal in synchronization with the trigger signal supplied from the preset counter 18, and can send the binary data to the data bus 28.

The RAM 24 can store this binary data, and the RO
M26 contains the repetition period (GRi) of all Loran C chains.
), programs for the CPU 20, etc. are stored.

The hardware of this embodiment has the above configuration, and its operation will be explained below according to the flowchart.

In FIG. 3, in this embodiment, a current position calculation process 200 is performed after a preprocess 100 is performed, and these processes 100 and 200 will be explained in sequence below.

In the figure, at step 100, initial acquisition processing for the master station and slave station (step 102) is performed, and then third cycle detection processing for the Loran C signal (step 10) is performed.
4) is performed, and finally, the third cycle of tracking is started (step 106).
02>, a known technique can be used for the third cycle detection process (step 104), but the initial acquisition process for the master and slave stations (step 102) is described, for example, in Japanese Patent Application No. 58-161.
As shown in 724, each Loran pulse of the Loran C signal is sampled in units of 20 run repetition periods, and successive sampling data units are sequentially added a predetermined number of times, and the first period and the first period of the added data are 2 cycles is Loran C
It is possible to perform this by following a procedure in which the signals are added with consideration to the phase coding of the signal, and the master station and slave station are determined from this final summed data.

In this way, even if the Loran C radio wave is weak, its initial capture can be performed reliably and within a short time.

Further, the third cycle detection process (step 104) is performed at intervals of 2.5 μs over several hundred μs before and after the tracking position of the detected Loran pulse, as shown in Japanese Patent Application No. 58-101444. It is possible to perform this by following a procedure in which a pair of sampling pulses is generated every 10 Lts, the sampling data obtained thereby is added a predetermined number of times, and the third cycle of the Loran pulse is detected from the added data.

In this way, the time required for the third cycle detection operation can be significantly reduced.

This process (step 104) is
As shown in 7804, the sampling data of the Loran pulse is added a predetermined number of times, the envelope waveform of the Loran pulse is estimated from the added data, and the third cycle of the Loran pulse is detected from this envelope waveform. It is also possible to follow the procedure.

In this way, even under conditions where the S/N of received radio waves is extremely poor, it is possible to detect the third cycle accurately and in a short time.

When the third cycle detection processing for all stations is performed as described above, the tracking operation for these third cycles is started in step 106, and the process proceeds to step 200.

Next, the processing contents of step 200 will be explained.

In FIG. 3, in step 200, the current position is first calculated (step 202), then the calculated position is outputted (step 204), and these steps are repeated.

Here, in step 202, the current position is calculated according to the following procedure.

FIG. 4 shows the processing procedure of step 202,
In the first step 500, the third cycle S/N measurement process shown in FIG. 5 is started.

In this third cycle S/N measurement process, radio noise is statistically treated as following a Gaussian distribution, and this device receives carrier wave Ca containing noise NZ as shown in Figure 6(a). shall be

At this time, the aforementioned third cycle tracking has already started, and the sampling pulse SP obtained by the tracking operation is
As shown in the same figure (b), Loran C pulse SLP
This occurs at the positive peak position in the third cycle of .

If the amplitude of the Loran C pulse SLP that occurs when this sampling pulse SP is generated is represented by the value S as shown in FIG. rOJ when is greater than the value S
and when this amplitude is smaller than the value S, it becomes "1".

Corresponding sampling is performed in the first step 550 in FIG.
At step 52, it is determined whether the instantaneous value n1 of the noise NZ based on the Loran C pulse SLP is greater than the value -8.

When it is determined in this step 552 that the instantaneous value n is greater than the value -8, that is, that the carrier wave Ca is higher than the O level, the count value is incremented by 1 in step 554, and in step 556, the count value is increased. is set as the value M÷'.

Further, when it is determined in the step 552 that the instantaneous value n is not greater than the value -8, that is, that the carrier wave Ca is below the O level, the step 554.
Processing substantially similar to step 556 is performed in steps 558 and 560, and in step 560 the count value is changed to the value M-.
is set as .

Roughly speaking, in step 562, it is determined whether sampling has been performed N times or not, and when sampling has been performed N times, the process advances to step 7564.

In step 564, the value M- obtained in step 560 is subtracted from the value M+ obtained in step 556 when sampling has been performed N times.

Here, if sampling is performed N times when the instantaneous value of the noise NZ is the value n, then the probability distribution P(n
> has an average value of O and a variance of σ2 as shown in Figure 7.
(σ is the standard deviation and corresponds to the actual value of the noise, and σ2 corresponds to the noise power) is a probability density function having a Gaussian distribution.

The probability density function P(n) at this time is, Therefore, when only the noise Nz is sampled,
The probability that the binarized data becomes "1" is equal to the probability that it becomes rOJ, and therefore the values M, , M- obtained at steps 556 and 560 are equal.

Therefore, the difference between them (M, -M-> becomes O, and 'S/N at that time becomes -NB).

Further, when the sampling pulse SP is synchronized with the peak of the carrier wave Ca of the Loran C pulse SLP as shown in FIG.
If the instantaneous value n of Z is smaller than the value -8, the sampling value at that time will be a negative direct value, and if the instantaneous value n is larger than the value -8, the sampling value will be a positive value.

Therefore, in the former case, the binarized data will be "0",
In the case of review, it is "1".

In Figure 6, the probability distribution of the sampling value is 7th.
As shown by the broken line P (n-3) in the figure, the average value is the value S
Then, the dispersion value σ2 becomes a Woossian distribution, and the probability distribution P(n) containing only noise is translated by S in the positive direction.

The probability density function P (n-3) at this time is such that in the above probability distribution P (n-3), the area A2 of the shaded part in Fig. 7 has a negative sampling value at that time. The probability A, which is equal to the probability, and the probability that this sampling value is positive, is 1 A'2.

Therefore, when N times of Sambrizig are performed, the value M
- is M-=NXA? becomes.

Moreover, the value M+ is M, =NM- =N(1A2) becomes.

Therefore, their difference is M+ M-=N (1A2) NA2=N(1-2
person 2), and this difference is determined in step 564.

In Figure 7, the probability density function P (
Since the average value S of n-3) is equal to the value σ, P (n −
3) When =S, the S/N corresponds to 0clBk:'.

At this time, the subtraction value (v knee v-> value is N pieces - N- =
It is understood that N (12A2) ='0.6826N, and when the value of the subtraction value (M, -M-) is 0.6826N, S/NtfiodB is obtained.

When the correlation between the subtraction value (N, -M-) and the S/N is determined in this way, a curve as shown in FIG. 8 is obtained. Therefore, in this embodiment, the steps shown in FIG.

The S/N is determined from the curve by the knob 566.

The process shown in FIG. 5 is always repeated, and as a result, the S of the Loran C pulse SLP of the main station and each slave station is
/N is always required.

When the above-mentioned third cycle SN measurement process is started, step 502 in FIG. The area where you live is required.

Here, a normal Loran C chain consists of a master station and four or less slave stations, and an example of their arrangement is shown in FIG.

In the figure, slave stations W, X, and Y surround a master station M.

A master station M and a slave station W are arranged here.

Areas 81 to S8 are defined by line segments 11 to 1B connecting X, Y, and Z and arcs C1 to C4.

In step 502 of FIG. 4, the current position is approximately calculated using the Loran C signals emitted from the master station M and the arbitrarily selected combined slave station in the arrangement example of FIG.

Then, in step 504, the area to which the approximate calculated position belongs is determined from the areas vj, S, to S8.

When the area to which the current position belongs is determined in this way,
In step 506, the combination of slave stations is determined, and in step 508, the exact current position is calculated.

The calculation in step 508 is based on hyperbolic radio navigation similar to step 502, but the number of slave stations used at this time is two in this embodiment, and the combination thereof is determined as follows. .

FIG. 10 shows the processing procedure of steps 504 and 506, and in the same figure, steps 600, 602, and 60
4,606,608,610,612.614, the approximate calculated position obtained in step 502 is the area S1.4 in FIG. S2. S313! , S51 Ss, 371
It is determined which of 3B it belongs to (step 50
4).

Here, the combination of slave stations that can be used to accurately calculate the current position is approximately determined by the areas S, to S8.

For example, the slave station combination that can be used in area S1 is XY.

xw, yz, XW, XY, WZ in area S2, YZ, XY, WZ in area S3, and WZ, XW, YZ in area $4.

As the slave station combination used to calculate the current position, it is preferable to select one that has a good S/N ratio of these Loran C signals and does not cause calculation errors. .

If they belong to S2 and S3.34, the slave station combination x
Preferably, y, xw, yz, and wz are each selected.

In addition, in this embodiment, the current position is calculated by hyperbolic radio navigation, so as shown in FIG.
When the and hyperbola 702 intersect at a small angle, the calculation error increases, and when they intersect at a large angle, as marked in Fig. 12, the calculation accuracy is extremely high.
It is preferable to select a combination of slave stations whose hyperbolas intersect at a large angle as shown in FIG.

Therefore, steps 650, 652 and 654 in FIG.
At step 656, a combination of slave stations is selected based on the above considerations, and therefore, at step 508 in FIG. 4, an extremely accurate current position is calculated.

In addition, in region S5, the ground waves of the radio waves of slave stations W and Z have a large attenuation, and the received waves are only spatial waves. Therefore, the only usable slave station combination is XY, and such a selection is made in step 658. There is.

And area S6. S7. The same is true for S1],
Therefore, in step 670, the combination XW is determined, and in steps 6-72, the combination
Then, each combination WZ is selected.

Note that once the accurate current position is calculated as described above, the S/N is calculated at step 510 in FIG.

It is determined whether good position measurement is possible using the hyperbolic angle of acceptance as a determining factor. If this is possible, the process returns to step 204 in FIG. 3 to display the current position, and then returns to step 202. , repeat the process.

If it is determined in step 510 that good position measurement is not possible, the process advances to step 514, where it is determined whether or not other slave station combinations allow better measurement.

When it is determined in step 514 that another slave station combination is better, the process is changed to that slave station combination in step 516, and the process proceeds to step 512.

Further, when it is determined in step 514 that another combination is not better, the process advances to step 512.

If it is determined in step 512 that the object has not moved to another area, the process returns to step 508, and the current position is calculated based on the combination.

In this way, even after that, the slave station combinations are white in order of the reception condition based on factors such as the area to which the reception position belongs, the S/N of the received radio wave, the hyperbolic intersection angle, etc. i71 is selected and the accurate current position is calculated.

As explained above, according to this embodiment, the optimal combination of slave stations for calculating the current position is automatically determined according to the reception status, so the device determines the optimal combination of slave stations at initial startup and during movement. Therefore, the operability of the device can be greatly improved. For this reason,
When this device is installed in a vehicle, the burden on the driver is significantly reduced.

In this embodiment, the current position is approximated by hyperbolic radio navigation, and the combination of slave stations is determined from the calculated position, but this position can be used by another current position calculation device (for example, one that uses geomagnetism). It is also possible to configure the device to teach from the computer or by manual operation.

In addition, in this embodiment, areas 81 to S8 were set in a simple manner, but the settings are automatically changed by calculation according to the radio wave strength of each 0520 station, the distance between each station, etc. It is also suitable to configure the device.

For example, in the area S1, the S/N of the radio waves of the main station M is
If for some reason the transmission power decreases for some reason (usually this is unlikely to happen as the transmission power of that station is higher than that of the others), the device is designed so that position detection is performed using only a combination of slave stations such as slave stations X, Y, and W. It is also suitable to configure.

(Effects of the Invention) As explained above, according to the present invention, the optimal slave station combination is always automatically selected even when the reception status changes due to movement, and the combination is taught to the device through operation. Therefore, the convenience of the device is improved.

[Brief explanation of drawings]

FIG. 1 is a diagram corresponding to the claims of the present invention, FIG. 2 is a block diagram showing a preferred embodiment of the device according to the present invention, FIG. 3 is a flowchart explaining the general operation of the device shown in FIG. 2, and FIG.
The figure is a flowchart showing the contents of the current position calculation process, FIG. 5 is a flowchart explaining the third cycle S/N calculation process, FIG. 6 is a waveform diagram showing the relationship between the Loran pulse and the sampling pulse, and FIG. An explanatory diagram of the probability distribution of sampling values, Fig. 8 is a graph showing the correlation between calculated values and S/N, Fig. 9 is an explanatory diagram of the arrangement positions of master and slave stations, and Fig. 10 is an area determination process and a slave station combination determination process. 11 and 12 are explanatory diagrams of hyperbolic intersection angles. 10...Receiving antenna 12...High frequency amplifier 14...Limiter circuit 16...Latch circuit 18...Preset counter 20...CPU 22...Address bus 24...RAM 26... ROM 28...Data bus 30...Clock generation circuit

Claims (1)

[Claims] (1) Receiving means for receiving the Loran C signals of the main station and each slave station; Signal selection means for selecting a plurality of slave station Loran C signals that can be used to calculate the current position based on the current position and the position of each slave station; A Loran C receiver comprising: current position calculation means for determining the current position based on each selected slave station Loran C signal and the main station Loran C signal.