JPS6266179A - Cycle selecting device for loran c receiver - Google Patents

Abstract

PURPOSE:To decide exactly a cycle even in a receiving spot having waveform distortion by comparing a cycle which has been received in advance and a cycle waveform of the next reception, in a receiving point. CONSTITUTION:A signal identification circuit 4 identifies only a signal of a station which has been set by a channel selecting circuit 5, from in a loran signal from a receiving part 1, and outputs its identification signal to a storage circuit 3. The storage circuit 3 stores in advance ideal waveforms of a main station and each substation, identifies and picks up each signal by an identification signal of an output of the circuit 4 from in plural three-cycle detecting signals from a detecting circuit 2 and compares it with a stored cycle waveform. In this case, a receiving waveform having distortion is also stored in advance, and by comparing it with the next receiving waveform, a cycle can be decided exactly.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a device for selecting a particular cycle (usually the third cycle) of a Loran C signal in a Loran C receiver.

(Prior Art) In a Loran C receiver, it is necessary to select a specific cycle (usually the third cycle under the conditions that there is no influence of spatial waves and the amplitude is large) in order to determine the measurement point of the received signal. This type of conventional method compares the cycle waveform detected by the 3rd cycle detection circuit with the ideal cycle waveform, and if the comparison value is within a certain tolerance range, it is determined that it is the 3rd cycle. However, this has the disadvantage that if the received waveform is distorted due to long-distance propagation, characteristics on the propagation path, topography of the receiving point, etc., cycle determination becomes impossible or incorrect cycle determination occurs.

(Problems to be Solved by the Invention) The present invention aims to solve the above-mentioned drawbacks of the prior art, and is a Loran C receiver selection device capable of accurate cycle determination even when waveform distortion is large. It provides:

(Means to Solve the Problems) The present invention is characterized in that a received cycle waveform is stored in advance at a receiving point, and a cycle determination is performed by comparing this with the next received cycle waveform. shall be. Therefore, reliable cycle judgment is possible even at reception points with waveform distortion, and since the stored waveform is rewritten with the latest received waveform, it is possible to detect differences in the received waveform due to changes in circuit characteristics due to aging or changes in propagation path characteristics due to the seasons. It is also possible to eliminate the effects.

(Example) An embodiment of the present invention shown in the drawings will be explained in detail below.

FIG. 1 is a block circuit diagram showing one embodiment of the present invention.
1 is a receiving section, 2 is a 3 cycle detection circuit, 3 is a cycle determination storage circuit, 4 is a signal identification circuit, and 5 is a channel selection circuit.

The receiving unit 1 receives and amplifies the Loran signal induced by the antenna.

The 3rd cycle detection circuit 2 receives the output of the receiver 1 and detects the second
A phase shift point S is generated in the third cycle from the rise of the Loran signal as shown in Figure (A), and a waveform as shown in Figure (B) is created. This waveform is shaped into a rectangular wave, and C)
Outputs a 3-cycle detection signal with the waveform shown in . The means for detecting a desired cycle, that is, for generating a phase deviation point at the third cycle, is well known and will not be described here.

The channel selection circuit 5 is a circuit for setting a main station (7 members of Loran C Che) and a plurality of slave stations, and sends the output of the station setting to the signal identification circuit 4. The signal identification circuit 4 receives the respective outputs of the receiving section 1 and the channel selection circuit 5, identifies only the signal of the station set by the channel selection circuit 5 from among the received Loran signals, and stores the identification signal for cycle judgment. Output to circuit 3. The cycle determination storage circuit 3 receives the respective outputs of the 3-cycle detection circuit 2 and the signal discrimination circuit 4. The cycle judgment storage circuit 3 has a memory therein for storing the waveforms of each of the main station and a plurality of slave stations, and stores ideal waveforms as shown in FIG. Store it in the memory (.Next, 3 cycle detection circuit 2
Among the plurality of 3-cycle detection signals sent, each signal is identified and picked up using the identification signal output from the signal identification circuit 4, and compared with the stored cycle waveform corresponding to each signal. conduct. For example, the 3-cycle detection signal of the main station is extracted based on the identification signal of the main station, and compared with the stored cycle waveform of the main station.

At the first reception, what is stored is the ideal waveform,
If the received waveform has an extremely good S/N ratio and no waveform distortion as shown in Figure 2, that is, if the envelope a in Figure 2 (A) is the same as the ideal waveform, then the phase deviation in Figure 2 H Front and back width of point C
and d are the same, and the width is exactly 5 μs (this is true because the carrier wave of Loran C is 100 KHz and 1 cycle is IO μS), but if this is the case, the ideal waveform and the received waveform clearly match, and immediately Can judge 3 cycles. There are various determination methods, that is, waveform comparison methods.9 For example, by reading out the stored waveform data at the same period as the received waveform and at the same frequency as the carrier wave, a waveform pulse similar to that shown in Figure 2-1 can be reproduced. This can be superimposed with the received waveform, and the reproduced waveform is repeated 10 times until they match.
Shift every μs.

Phase deviation point of the reproduced waveform where they match (Figure 2 (c)
(b) is output as the 3 cycle point and used as the reference point for time difference measurement of Loran C. Since it is rare for a perfect match to occur, it goes without saying that a certain tolerance value should be set for matching determination.

The above description is based on the first reception and the case where the received waveform is ideal, but in reality the waveform distortion and S/N may be low.

As a solution to low S, it can be improved by statistical processing such as averaging processing in waveform comparison, but if 'e-shaped distortion exceeds the allowable value of similarity in waveform comparison, it may not be possible to judge or it may cause misjudgment. . Therefore, by storing a distorted received waveform in advance and comparing it with the next received waveform, reliable cycle determination can be made.

During the first reception, cycle judgment is performed by comparing the stored ideal waveform and the distorted received waveform. The received waveform (value averaged by the SA value) is automatically rewritten as the ideal waveform and stored. be done. If the first reception is so distorted that it is impossible to determine the cycle or it is incorrectly determined, if the position of the receiving point is known, the correct cycle can be determined, so use 9 manual operations to rewrite the waveform of this correct cycle as the ideal waveform. By storing one or more values, it becomes possible to automatically and reliably determine the cycle in the next measurement.

Although the main station has been described above, each slave station is also caused to perform similar operations. The waveform storage memory is complete if all cycles of all chains are stored, but if only the necessary number of stations of the chain are stored and a station that is not stored is selected, the waveform memory will be complete. The stored waveform may be rewritten to an ideal waveform, and then the received waveform may be stored again.

If the cycle cannot be determined, it is also possible to determine the correct cycle from the 9-position data and automatically store the received waveform.

(Effects of the invention) As explained above, reliable cycle determination is possible even when waveform distortion is large, so Loran C can now be used in places where it could not be used before, and 9 manual corrections can be made. There are advantages such as eliminating the need for

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram showing one embodiment of the present invention, and FIG. 2 is a waveform diagram for explaining the operation of the embodiment. 1... Receiving section, 2... 3 cycle detection circuit, 3...
・Cycle judgment storage circuit, 4... Signal identification circuit, 5.
...Tuning selection circuit. Patent applicant: Japan Radio Co., Ltd. M2 Diagram Award

Claims (1)

[Claims] A cycle selection device that selects a specific cycle of a Loran C signal in a Loran C receiver includes a receiving section that receives and amplifies the Loran C signal, a cycle detection circuit that detects a desired cycle of the Loran C signal, and a detected cycle. and a pre-stored cycle waveform corresponding to that signal, and if the comparison value is within a predetermined range, the detected cycle is determined to be the desired cycle, and the detected cycle is determined to be the desired cycle. A cycle selection device for a Loran C receiver, comprising a cycle determination storage circuit that rewrites and stores a cycle waveform with a newly detected cycle waveform.