JPS5855466B2 - Loran A receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a Loran A receiver, and more particularly to an improvement in a synchronization device that maintains synchronization between a tracking point of a master and slave station signal and a sampling point using a branch pulse.

In general, a Loran A receiver divides the frequency of a reference pulse to sample the tracking points of the main station signal and slave signal, adjusts the oscillation frequency of the reference pulse by an AFC circuit to adjust the drift of the tracking point, and divides the reference pulse by a tracking control circuit. This is done by adjusting the frequency ratio to maintain synchronization between the tracking point of the master and slave station signals and the sampling point by the frequency division pulse.

Also, since the reference oscillator used in the receiver is not very accurate, the tracking speed in the AFC circuit is set to be high, while the tracking speed in the tracking control circuit is
If the tracking in the circuit is sufficient, there is no need to make it that fast, so it is set to follow the ship's speed.

In the conventional Loran A receiver, the AFC circuit operates based on the main station signal, and the tracking control circuit operates based on the slave station signal.

However, since the tracking control circuit has a slow tracking speed, it is less susceptible to disturbances, and therefore the S/N of the follower signal
Although the tracking of the slave station signal can be maintained even if the ratio deteriorates somewhat, the tracking speed of the AFC circuit is set to be high, so it is easily affected by disturbances, and therefore the S of the main station signal is
When the /N ratio worsens, it becomes difficult to track both the main station and slave station signals.

This invention was made in view of the above, and selects a station with a good reception condition among the master and slave stations as a measurement reference station for activating the AFC circuit, and when the reception condition of the master station is relatively good, the AFC circuit is activated. The AFC circuit is operated based on the main station signal, and the tracking control circuit is operated based on the slave station signal, and when the reception condition of the slave station signal is relatively good, the AFC circuit is activated based on the slave station signal, and the tracking control circuit is operated based on the slave station signal. The circuit is operated based on the main station signal.

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

FIG. 1 is a block diagram of a Loran A receiver that is an embodiment of the present invention.

Moreover, FIG. 2 is a waveform diagram of main parts during operation.

The amplifier circuit 1 is a circuit that amplifies the Loran signal from the antenna, and the signal amplified to a certain level is output to the next stage waveform shaping circuit.

Note that the amplifier circuit 1 includes a detection circuit and outputs an envelope wave to the waveform shaping circuit 2.

The waveform shaping circuit 2 is a differentiation circuit 20 that differentiates the envelope wave once.
, Differentiating circuit 200 A differentiating circuit 21 that further differentiates the first differentiated output, AGC that forms AGC pulses from the envelope wave.
Pulse circuit 22. Consists of a signal quality judgment pulse circuit 23 that forms a pulse for signal quality judgment from a first differential wave and an AFC/tracking pulse circuit 24 that forms an AFC (automatic frequency control)/tracking pulse from a second differential wave. Tete, AG
This circuit forms three types of pulses for determining the quality of the C1 signal and for AFC/' tracking and outputs them to the main station sample circuit 3 and the slave station sample circuit 4.

The AGC pulse circuit 22 compares the level of the received signal with a predetermined AGC setting [direct a] as a reference, and forms a pulse that is defined as a time when the level of the received signal exceeds the set value a.

The signal quality judgment pulse forming circuit 23 generates a single differential wave and 0'■
It compares with a slice level obtained by slicing by level b, and when the level of the differential wave is higher than the slice level by one time, a pulse that becomes bi is formed.

Further, the AFC/tracking pulse forming circuit 24 forms pulses corresponding to the phase and positive/negative level of the twice differential wave.

The sample circuits 3 and 4 are supplied with sample pulses from a master station frequency divider 5, which forms a signal synchronized with the main station signal, and a slave station frequency divider 6, which forms a signal synchronized with the slave station signal, respectively. The AGC pulse LOW, the signal quality determination pulse NI, and the AFC/tracking pulse are sampled.

The main station sample circuit 3 consists of three sample circuits 30°3L3
2, an AFC/tracking control pulse forming circuit 33 that forms an AFC/tracking control pulse based on sample data from a sample circuit 30, and a gain control data forming circuit 34 that forms gain control data from the AGC pulse. .

Similarly, the slave sample circuit 4 also includes three sample circuits 40, 41, 42, an AFC/tracking control pulse forming circuit 43, and a gain control data forming circuit 44.

Among these, the AFC/tracking control pulse forming circuits 33 and 43 convert the control amount for AF'C1 tracking into a digital amount from a measurement reference station (hereinafter referred to as AFC station) to be described later.

) is led to an AFC circuit that performs AFC control via a selection gate and a tracking station selection gate, and to a tracking control circuit that performs precise control.

Further, the gain control data circuits 34 and 44 output a pulse train having a number of pulses corresponding to the AGC pulse width or a digital signal having a corresponding pulse width to the main station AGC.
It outputs to the value circuit 7 and the slave AGC value circuit 8, respectively.

The main station AGC value circuit 7 and the slave station AGC (W circuit 8) each consist of a circuit including a D/A converter, and convert the gain control data formed based on the pulse width from the sample point of the AGC pulse line into an analog signal. to control the gain of the amplifier circuit 1.

The AGC switching circuit 9 is a circuit that automatically switches the main station AGC value circuit 7, the slave station AGC value circuit 8, and the amplifier circuit 1 alternately.

Note that a circuit that forms AFC/tracking control pulses to perform AFC control and tracking control and a circuit that forms AGC pulses to form gain control data and performs AGC control are, for example, the former described in Japanese Patent Publication No. 47-5069. In the official bulletin,
For the latter, well-known means such as those disclosed in Japanese Utility Model Publication No. 51-37430 may be used.

The AFC station selection gate 10 selects the AFC from the sample circuit 3.4 based on a signal from an AFC station selection circuit to be described later.
/ tracking control pulse to the next stage AFC circuit 1
This is a gate circuit that outputs to 2.

Further, the tracking station selection gate 11 also outputs A from the sample circuits 3 and 4 based on the signal from the AFC station selection circuit 16.
This is a gate circuit that outputs either the FC/tracking control pulse to the tracking control circuit 14 at the next stage.

When the AFC/tracking control pulse passes through the AFC station selection gate 10, it becomes an AFC control pulse for activating the AFC circuit 12, and when it passes through the tracking station selection gate 11, it becomes a tracking control pulse for activating the tracking control circuit 14. .

The AFC circuit 12 receives A that has passed through the AFC station selection gate 10.
The oscillation frequency of the reference oscillator 13 is changed based on the FC control pulse.

Further, the tracking control circuit 14 changes the frequency division ratio of the main station frequency divider 5 or the slave station frequency divider 6 via the gate 15 based on the tracking control pulse that has passed through the tracking station selection gate 11.

The gate 15 connects the tracking control circuit 14 to the main station frequency divider 5 or the slave station frequency divider 6 based on the signal from the AFC station selection circuit.
This is a gate circuit that switches and connects to the

In addition, in the AFC circuit, for example, Japanese Patent Publication No. 49-28285
As disclosed in the above publication, frequency control may be substantially performed by disabling pulses of a certain period among the oscillation pulses, that is, by adjusting the number of oscillation pulse trains.

The sample data of the sample circuit 31 of the main station sample circuit 3 is led to the main station signal quality integration circuit 17.

Further, the sample data of the sample circuit 41 of the slave station sample circuit 4 is led to the slave station signal quality integration circuit 18.

The main station signal quality integration circuit 1γ and the slave signal quality integration circuit 18 are circuits that integrate pulse 2 for determining signal quality at sample points, and if a pulse is detected, executes +1, and if not detected, executes 10. do.

Such an integration circuit can be configured with, for example, an up/down counter.

Note that the number of integrations is predetermined so that there is not much variation in the integration results under the same signal conditions.

Therefore, the more appropriate the received signal waveform is, the larger the integration result becomes, and the more inappropriate the received signal waveform is, the smaller the integration result becomes.

The AFC station selection circuit 16 has a comparison circuit that compares the integration results from the main station signal quality integration circuit 17 and the slave station signal quality integration circuit 18 and compares the magnitude thereof.

It also has a comparison circuit for comparing the AGC values output from the master station AGC value circuit 7 and the slave station AGC fili circuit 8.

Then, a station with a larger AGC value (and a larger signal quality integrated value) is selected as an AFC station, and its selection signal is output to the AFC station selection gate 10, the tracking station selection gate 11, and the gate 15.

As described above, when the AFC station selection gate 10 receives the selection signal from the AFC station selection circuit 16, it connects the sample circuit of the selected station and the AFC circuit 12, while the tracking station selection gate 11 receives the selection signal. When the selected station is selected, the sample circuit of the station opposite to the selected station is connected to the tracking control circuit 14.

Furthermore, upon receiving the selection signal, the game 115 connects the tracking control circuit 14 to the slave station frequency divider 6 when the selected station is the master station, and connects the tracking control circuit 14 to the master station frequency divider 6 when the selected station is the slave station. Connect to device 5.

It should be noted that the AFC station selection circuit 16 detects when, during operation, the magnitude of the signal quality integrated value of the master and slave stations is reversed, the magnitude of the AGC value is reversed, and furthermore, the difference between the AGC values exceeds a certain value. Switch the station selected as the AFC station.

In this way, during operation, the new selection condition for the measurement standard station is that the difference in AGC values is a certain value or more.
This is to prevent the measurement standard station from changing frequently.

As described above, the AFC station selection circuit 16 can select a station signal with a larger amplitude by comparing the magnitudes of the AGC values of the master and slave stations, and can select a station signal with a larger amplitude by comparing the magnitudes of the signal quality integrated values. A station signal with a more appropriate waveform is selected, and a station with a signal having a large amplitude and an appropriate signal waveform is selected as an AFC station.

To explain the case where the main station is selected as an AFC station with the above configuration, the main station sample circuit 3 and the slave station sample circuit 4 receive sample pulses from the master station frequency divider 5 and the slave station frequency divider 6, respectively. The AGC pulse low, signal quality judgment pulse 2, and AFC/tracking pulse are sampled by , and the amount of drift between the sample point and the tracking point is
The main station signal is adjusted by the AFC circuit 12, and the slave station signal is adjusted by the tracking control circuit 14.

That is, the amount of drift of the sample point with respect to the tracking point of the main station signal is detected by the AFC/tracking control pulse forming circuit 33, and the control pulse is output to the AFC circuit 12, so that the sample point matches the tracking point as a reference. In addition to controlling the oscillation frequency of the oscillator 13, the amount of drift of the sample point with respect to the tracking point of the slave signal is detected by the AFC/tracking control pulse forming circuit 43, and the control pulse is output to the tracking control circuit 14, thereby changing the sample point. The frequency division ratio of the slave frequency divider 60 is controlled so that the following point coincides with the tracking point.

Further, the degree of the amplitude of the main station signal is detected by the gain control data forming circuit 34, and control data for making the amplitude constant is output to the main station AGC value circuit 7, and the gain of the amplifier circuit 1 is Take control.

Similarly, the magnitude of the amplitude of the slave signal is detected by the gain control data forming circuit 44, and control data for making the magnitude of the amplitude constant is output to the slave AGC value circuit 8, which controls the gain of the amplifier circuit 1. conduct.

Furthermore, the main station signal quality integration circuit 17 and the slave station signal quality integration circuit 18 each integrate data obtained by sampling the signal quality determination pulse 2 at the sample points.

In such an operating state, the slave station signal quality integration circuit 1
When the magnitude of the integrated value of 8 becomes larger than the integrated value of the main station signal quality integration circuit 17, and the magnitude of the slave AGC value is greater than the magnitude of the master station AGC value by a fixed number of cycles or more, the AFC The station selection circuit 16 is an AFC station selection gate 10
, sends a signal to the tracking station selection gate 11 and gate 15 to select the slave station as an AFC station.

When this signal is output, the AFC station selection gate 10 selects the AFC/tracking control pulse forming circuit 43 of the slave station sample circuit 4.
The tracking station selection gate 11 also connects the AFC/tracking control pulse forming circuit 33 of the main station sample circuit 3 to the tracking control circuit 14 .

Further, the gate 15 connects the tracking control circuit 14 to the main station branching unit 5.
Connect to.

Therefore, the drift between the tracking point and the sample point of the slave station signal is controlled by the oscillation frequency control of the reference oscillator 13 by the AFC circuit 12, and the drift between the tracking point and the sample point of the main station signal is controlled by the tracking control circuit 14. This is performed by controlling the frequency division ratio of the station frequency divider 5.

That is, if the signal condition of the main station signal is better than that of the slave signal, the AFC circuit 12 is operated by the main station signal.
If the signal condition of the slave station signal is better than that of the master station signal, the operation of the AFC circuit 12 is performed by the slave station signal.

As described above, according to the present invention, in order to always perform AFC operation that requires a faster tracking speed using the signal of a station with a good signal condition, it is possible to perform the AFC operation at a position where the reception condition of the main station signal is poor and the reception condition of the slave station signal. Even if the station moves to a bad position, both stations can be easily and stably tracked.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a Loran A receiver according to an embodiment of the present invention, and FIG. 2 is a diagram showing signal waveforms of the main parts of FIG. 1. 3-Main station sample circuit, 4-Slave station sample circuit, 5-Main station frequency divider, 6-Slave station frequency divider, 7-Main station AGC value circuit, 8
-Slave station AGC value circuit, 10-AFC station (measurement reference station) selection gate, 11-tracking station selection gate, 12-AFG circuit, 13-reference oscillator, 14-tracking control circuit, 16-AF
C station (measurement reference station) selection circuit, 17-main station signal quality integration circuit, 18-slave station signal quality integration circuit.

Claims (1)

[Claims] 1. A control pulse that divides the frequency of the reference pulse to sample the main station signal and the slave signal, and adjusts the drift between the sample point and the tracking point by adjusting the frequency of the reference pulse. 5AFC circuit In a Loran A receiver equipped with an AGC circuit that maintains synchronization between the tracking point and the sample point by inputting the signal to a tracking control circuit that performs frequency division ratio control, and keeps the gain of the main and slave station signals constant, a signal quality determination pulse forming circuit that processes each signal once to form a signal quality determination pulse; and detecting the signal quality determination pulse at the sample point;
Compare the main station AGC value and the slave station AGC value of the AGC circuit with a signal quality accumulation means for accumulating the number of non-detections, and compare the master station signal quality accumulation value and the slave station signal quality accumulation value of the signal quality accumulation means. measurement reference station selection means for selecting a station with a signal having a large amplitude and an appropriate signal waveform as a measurement reference station based on the comparison result; and when the selected measurement reference station is a main station, said AFC;
The circuit is connected to a control pulse forming circuit for a master station, and the tracking control circuit is connected to a control pulse forming circuit for a slave station, and when the measurement reference station is a slave station, the AFC circuit is connected to a control pulse forming circuit for a slave station. , and gate means for connecting the tracking control circuit to a control pulse forming circuit for a main station.