JPS6258474B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a Loran signal capture method that automatically captures Loran signals.

In recent years, Loran receivers generally capture and track Loran signals automatically, and the receiver is kept in a stable steady state during the tracking stage.

The first step, capturing the Loran signal, involves, for example, using the repetition period of the chain in use (hereinafter referred to as GRI) as the search period, and sampling the signal received within that GRI while updating the timing. The next stage of tracking the Loran signal is, for example, by referring to the moving speed of the ship and the previous speed of the tracking point, predicting an appropriate sampling timing, and then correcting the predicted timing. I have to.

The advantage of this method is that the signal capture timing (location of the tracking point) is always predicted during the tracking stage, so once the receiver is in a steady state at the tracking stage, the reception state is Even if things get worse, the positioning ability will continue to be maintained.

However, in this type of system, it is common to first capture the main station signal as a reference and then capture the slave signal, so if the current position is far from the main station, the S/S/ If the N ratio was very poor, even if the receiver was turned on in that area, it would not be able to capture the main station signal, and eventually positioning using the Laurent chain would become impossible.

This invention has been made in view of the above, and aims to provide a signal capture method that can easily capture the main station signal even in areas where the S/N ratio of the main station signal is poor. It is something.

To summarize this invention, focusing on the point that if the current position can be obtained by some means, the position line data of that position can be immediately obtained by calculation when using Laurent chaine,
Furthermore, since the main station signal has GRI periodicity, it is possible to improve the S/N ratio by integrating and averaging. The signal acquisition timing is predicted, and the signals at the predicted acquisition timing are integrated and averaged to acquire the main station signal.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram for explaining the principle of the acquisition method according to the present invention.

The received signal SIG shown in the figure is shown as a single pulse for ease of understanding, but in reality, the master and slave station signals are composed of multiple signals, and each signal is sampled using the envelope waveform. Then, as will be described later, the sample signal is A/D converted and taken into the microcomputer.

Since the period GRI represents the repetition period of the chain in use, as shown in the figure, it is equal to the repetition period of the main station signal M, and is also equal to the repetition period of the slave signals S ₁ and S ₂ .

Normally, when the receiver is powered on, it first searches for and captures the main station signal M. This search and capture of the main station signal M is performed using a strobe pulse with a sampling period of, for example, 100 μsec, using the entire period of the GRI as the search area, and identifying that the captured signal is the main station signal is , by detecting the phase code of the acquired signal.

Once the main station signal is captured as described above, the slave station signals S ₁ and S ₂ are subsequently searched and captured. It is assumed here that the chain used has two slave stations. Similar to the main station signal, the search and acquisition of slave station signals is normally performed using a strobe pulse with a GRI sampling period of 100μsec, and the signal identification is also based on the phase code, but depending on the number of slave stations. , each individually and first
Acquisition is performed in order starting from the th slave station. After capturing the slave station signal, the next step will be to sequentially move on to the tracking stage.

By the way, in normal conditions when both the main station signal and the slave station signal have a good S/N ratio, the above operation is performed relatively smoothly, but the S/N ratio of the main station signal
Even if the ratio is very poor and the master station signal cannot be captured using the above method, if the slave station signals S ₁ , S ₂
If the main station signal M can be captured and the position line data of the current position can be grasped, the stations of the signals S ₁ and S ₂ can be identified, and the acquisition timing Tm of the main station signal M can also be predicted. Therefore, at that timing Tm
By performing sampling N times for each GRI and integrating and averaging the sample signals, random noise components can be removed and a main station signal with a good S/N ratio can be captured even if the signal strength is weak.

In this invention, a current position setting means such as NNSS is used as a means for obtaining position line data of the current position, that is, as a means for knowing the times τS ₁ and τS ₂ . If the current position (latitude, longitude) information is obtained by such means, since the station position information is a fixed value, the time difference τS ₁ or τS ₂ can be calculated by calculation, and therefore, This means that the acquisition timing Tm of the main station signal can be calculated.

Next, FIG. 2 shows a block diagram of the main parts of a Loran receiver to which the above acquisition method is applied.

In the figure, a received signal from an antenna 1 passes through a high frequency amplifier circuit 2 and a filter 3, is converted into a signal of an appropriate level, and is sent to a sampling circuit 4. When the sampling circuit 4 receives the strobe signal from the strobe signal generation circuit 5, it samples and holds the received signal at that timing, digitizes the sample signal with the A/D converter 6, and sends it to the microcomputer 7. The strobe signal generation circuit 5 receives a timing signal from a real-time counter 8 that determines the actual strobe signal generation timing, and upon receiving the timing signal, supplies a pulse with a width of 0.05 μsec to the sampling circuit 4 as a strobe signal. The real-time counter 8 receives GRI data from the microcomputer 7 and data from a master station counter TM and a slave station counter TS, which will be described later, and determines the strobe signal generation timing based on the data. Further, identification data of the chain to be used is sent to the microcomputer 7 by the chain setting switch included in the input key 9, and the microcomputer 7 sends the identification data to the display 10.
The latitude and longitude data calculated by the calculation are sent to. Further, an NNSS receiver 11 as an external device is connected to the microcomputer 7 so that current position data can be periodically supplied to the microcomputer 7. Note that when the alarm 12 is further connected as an external device and the main station signal is too weak to improve the S/N ratio by cumulative averaging,
An alarm can be notified to the operator.

The microcomputer 7 is composed of a relatively high-speed 8-bit system consisting of several ordinary chips, and includes a CPU 70 that executes calculations and control, the sampling timing of the master and slave station signals, the predicted timing for capturing the master station signal, and the sampling timing. Corresponds to the integrated data value and its average value, or the setting chain
A RAM 71 that stores GRI, etc. and includes various work registers for calculations, a ROM 72 that stores execution procedures for the CPU 70, and an I/O interface 7 that exchanges data with external devices, circuits, etc.
3, and these elements are connected to a data bus DB, an address bus AB, and a control bus CB. Further, the RAM 71 is backed up by a battery 74 so that the stored contents are retained even when the power is turned off.

As shown in the figure, the RAM 71 includes a chain table, a group of counters for the main station, a slave station, and a buffer that temporarily stores the predicted timing for capturing the main station signal.
It has at least an area of TN and averaging register D, and the chain table is fixed and does not change, whereas the contents of the counter group, buffer, and averaging register change depending on instructions and operation results. be done.

The chain table is a table that stores the GRI corresponding to the chain set by the chain setting switch, and is read out when it is necessary to send the stored data to the counters TM, TS and the real-time counter 8. The main station counter
TM and slave station counter TS are counters that are read when determining the sampling timing of the main station signal and when determining the sampling timing of the slave station signal, respectively, and their stored data is sent to the real-time counter 8. In addition, the buffer TN temporarily stores the predicted timing for capturing the main station signal, which is determined by referring to the current position data obtained from NNSS etc. and the slave station signal capturing timing for which station identification has been performed. Transferred to the counter TM when reacquiring the main station signal. Again, the averaging register D is composed of an integrating register _D0 that integrates N pieces of data sampled N times according to the predicted timing, and an averaging register _D1 that divides the integrated value of the register by N.
The presence or absence of a main station signal is determined based on the contents of the average register _D1 . In addition to the above data, the RAM 71 also contains position data (rad) for each station that makes up the chain.
Units), conversion coefficients for determining latitude and longitude data from position line data, etc. are also stored in another area. In addition, as a means of setting the current position, NNSS
is optimal, but in this embodiment, the input key 9
I made it possible to set any value from
This allows the operator to directly input location data during times when NNSS is unavailable, or when the vessel is anchored at a port where the location is clear.

Next, the main part of the operation procedure of the Loran receiver consisting of the above configuration, that is, stored in the ROM 72, will be explained.
The main part of the execution procedure on the cPu 70 will be explained based on the flowchart in FIG.

First, in step _n1 (hereinafter step _nx is simply referred to as _nx ), the GRI corresponding to the chain set by the chain setting switch of input key 9 is set.
It is read from the chain table in the RAM 71 and set in a timer (not shown) as a reference period. Next, the main station counter TM and the like are set to predetermined values with reference to the GRI, and the main station signal is searched and captured. To explain an example of this procedure, first, GRI is set in the counter TM of the RAM 71, then the data of the counter TM is sent to the real-time counter 8, and the strobe signal generation circuit 5
A strobe signal generation timing is given to the sampling circuit 4 to sample the received signal. Then, the sample signal is digitized by the A/D converter 6 and taken into the microcomputer 7. This kind of sample signal acquisition is performed as many times as necessary to detect the phase code of the main station signal, and if the received signal cannot be determined as the main station signal, the content of the counter TM is decremented by 100 μsec, and the phase code is checked again. Sample signals are captured as many times as necessary to detect the code, and the presence or absence of the main station signal is determined. Then, the above procedure is executed until TM=0 as long as the main station signal cannot be captured, that is, until the entire GRI period is sampled every 100 μsec, and the search for the main station signal is performed. If a main station signal is found at any timing during the entire GRI period, the sampling timing at that time is captured by the counter TM (that is, the timing is detected by the counter TM).
), the next step is the slave signal search procedure.

The search and acquisition of the slave station signal is performed by the same procedure as the above-mentioned search and acquisition of the main station signal, and the acquired sampling timing is stored in the counter TS. In this step, all slave station signals are captured, and the sampling timing of the first slave signal is TS ₁ , the sampling timing of the second slave signal is TS ₂ , and the sampling timing of the ηth slave signal is TS 1. are respectively stored in TSn.

When acquisition of the master and slave station signals is completed, the current position is continuously determined while tracking is performed below _η4 . That is, at η ₄ , the position line is measured (in μsec units), and at η ₅ , the data obtained as a result of this measurement is converted into latitude and longitude data (in rad units) using a conversion coefficient that is separately obtained and stored in the RAM 71. A conversion operation is performed, and the result of the operation is further displayed on the display 10 at η ₆ . Note that tracking is always performed during this time, and the contents of the counters TM and TS are corrected each time.

When the reception status of the master station and slave station signals is good, the master and slave station signals are automatically captured and tracked after the power is turned on according to the above procedure, and the latitude and longitude are displayed continuously.

By the way, the above operation is performed when both the main station signal and the slave station signal can be captured, but if the main station cannot capture the main station signal at the acquisition stage, η
₂ to η ₁₀ , and an attempt is made to reacquire the main station signal.

First, at η ₁₀ and η ₁₁ , all slave station signals are captured using the same method as described above. followed by η ₁₂
Then wait until the current position data is input from the NNSS 11 or the input key 9. Needless to say, during this time, tracking of the slave station signal is performed. When the current position data is input, the process advances to η ₁₅ to take in the current position data, and further, the position line data is obtained in η ₁₆ . η ₁₇
Now, from the obtained position line data and the station position data stored in the RAM 71, the station identification of each slave station signal is performed. Furthermore, at η ₁₈ , the timing at which the main station signal can be captured is predicted from the position line data and the station position data, and the predicted timing is set as the buffer TN.
to be memorized. At _η19 , the contents of the buffer TN are transferred to the main station counter TM to prepare for sampling. Then, at η ₂₀ and η ₂₁ , sampling is performed N times at the predicted timing, and the obtained sample data is sequentially integrated into the integration register D ₀ , and at η ₂₂ , the contents of the integration register D ₀ are divided by N to obtain the average value. and set the average value in the average register _D1 .
At this stage, the value of average register D ₁ is usually
Since the main station signal has an improved S/N ratio, η ₂₃
The main station signal is captured at , and the process returns to _η4 .
If the main station signal cannot be captured even by the above-mentioned cumulative averaging, the process proceeds to η ₂₅ and the alarm 12 is set.

Note that the number of times N to integrate sample data is η ₂₀ .
should be as large as possible, and the time required for cumulative averaging should be as large as possible so that other processing is not adversely affected.
set to an appropriate size.

As described above, even if it is difficult to capture the main station signal using normal methods, it can be captured relatively easily by the procedure of η ₁₀ or less.

As described above, according to the present invention, even if the current position is far from the main station, it is possible to easily bring the receiver into a stable tracking state, and the positioning ability of the Loran receiver can be greatly improved. I can do it.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating the principle of the acquisition method according to the present invention. Further, FIG. 2 is a block diagram of the main part of a Loran receiver to which the same acquisition method is applied, and FIG. 3 is a flowchart showing the main part of the operating procedure of the receiver. 4...Sampling circuit, 5...Strobe signal generation circuit, 6...A/D converter, 7...Microcomputer, 8...Real time counter, 9...Input key, 11...NNSS, 12...Alarm.

Claims (1)

[Claims] 1 In the Loran signal acquisition method, in which the received signal is sampled while updating the timing and the Loran signal is captured, a current position setting means is provided to obtain the current position data, and also to capture multiple slave station signals. The station of the captured slave signal is identified from the current position data, and the acquisition timing of the main station signal is predicted from the identified slave signal signal and the current position data, and the master station A Loran signal capture method characterized in that the signal is captured by sampling the signal N times at the predicted capture timing and performing cumulative averaging.