JPS5942833B2 - Loran A receiver - Google Patents

Description

Detailed Description of the Invention The present invention provides an automatic tracking type Loran A receiver.
The present invention relates to a device that converts and amplifies the waveform of a signal to generate and extract a tracking target point.

Conventionally, this type of device has an automatic amplitude controller (AG) in the receiving amplifier.
C), it is necessary to change the AGC control force method depending on whether the device is in signal tracking operation state or signal tracking operation state, and there are different 4 required for position measurement.
Not only does the device become complicated and expensive, as separate AGC is required for each of the four run signals of the station, but it also has drawbacks such as the time required for the device to reach its initial state or a predetermined equilibrium state after power is turned on. there were.

In order to eliminate these drawbacks, the present invention eliminates the need for the AGC circuit, which has been indispensable in the past, by detecting and processing the phase information of the Loran A signal reception wave.

In other words, it was not possible to use carrier wave phase information in Loran A, but by introducing the three-cycle detection method used in Loran C, it is now possible to set a specific position tracking target point in the envelope. This is the standard for time measurement.

Is the drawing below? I will explain this in more detail.

FIG. 1 shows an embodiment of the present invention, and FIG. 2 is a waveform diagram for explaining the operation.

In the figure, 1 is a Loran A signal input terminal 2 is a receiving amplifier, 3 is a waveform converter, 4 is a first Norming amplifier, 5 is a transducer, 6 is a polarity switch, γ is a second limiter amplifier,
8 is a low-pass filter, 9 is a third limiter amplifier, 1
0 is a time difference measuring device, and 11 is a time difference display device.

Next, the operation shown in FIG. 1 will be explained using FIG. 2.

In FIG. 1, a Loran A signal, as shown in FIG. 2a, induced in a receiving antenna (not shown) is applied to input terminal 1.

The Loran A signal is amplified by a receiving amplifier 2.

The receive amplifier 2 is not necessarily required or may be of generally used power in the sense of reducing the overall noise figure of the receiver.

A part of the output of the receiving amplifier 2 is guided to a waveform converter 3 and transformed into a waveform as shown in FIG.

FIG. 3 is a block diagram showing an example of the waveform converter 3 of FIG. 1, in which 32 is an attenuator, 33 is an adder, and 34 is a delay circuit.

A part of the signal marked υ at the input terminal 31 is guided through the attenuator 32 to one input terminal of the adder 33.

The other part of the signal applied to the input terminal 31 is delayed by an odd multiple of the wavelength of the carrier wave of the Loran A signal (usually 5 μs).
adder 3 through a delay circuit 34 having a
3 leads to the input terminal of other force.

The output terminal 35 of the adder 33 is the output terminal of the waveform converter 3.

Figure 2 (i) Point P is the tracking target point of the Loran A signal, and is set at the design stage at a point where there is no mixing of spatial waves and where the amplitude is as large as possible, that is, slightly ahead of the peak of the Loran A signal. .

The waveform in Figure 2 is its envelope, or the horizontal axis (zero) at point P.
, and the phase of the carrier wave is in phase with waveform a in the portion before point P, and in phase with waveform a in the portion after point P.

The output of the first limiter amplifier which leads the output of the waveform converter 3 to the first limiter amplifier 4 is as shown in FIG. 2C.

The carrier wave phase relationship of the waveform of FIG. 2C is the same as that of FIG.

A part of the output of the receiving amplifier 2 is applied to the polarity switch 6.

The polarity switch 6 is composed of, for example, a phase inversion amplifier and a switch that alternately switches its input and output signals, and the time difference measuring device 10
The timing signal 'c generated by 'c is used as input for the other 5, and outputs are output by alternately switching between in-phase and anti-phase signals with the output of the receiving amplifier 2 every integer multiple (usually 1 to 5 times) of the repetition period of the Loran A signal. .

Correspondingly, the phase of the output of the third limiter amplifier 9 is inverted.

The polarity switch 6 cooperates with the time difference measuring device 10 to eliminate the offset of the transducer 5 and the third limiter amplifier 9.

The following explanation will be given only when the output of the pole switch 6 is in phase with the input.

The second limiter amplifier 1 receives the output of the polarity switch 6 as an input, and its output has the same @ and phase as the Loran A signal shown in FIG. 2a.

The transducer transducer 5 has two inputs, the output of the first limiter amplifier 4 and the output of the second limiter amplifier 7, and outputs the product thereof, which can be applied to the low-pass filter 8.

The low-pass filter 8 has the role of removing the carrier wave of the Loran A signal, and its output is dl in FIG.
If the S/N of the signal is good, d2 is the S/N of the Loran A signal.
An example of a case where N or worse is shown.

Even when the S/N is poor at d2, the polarity change point P is preserved, so it is possible to detect up to an S/N of about -20 dB.

The output of the low-pass filter 8 crosses the horizontal axis (zero) at the tracking target point P of the Loran A signal, and the portion before the point P is positive, and the portion after the point is negative.

The output of the low-pass filter 8 is guided to a third limiter amplifier 9.

The output of the third limiter amplifier 9 is as shown in FIG. 2e.

The output of the limiter amplifier 9 is captured and tracked by a time difference measuring device 10 using a known technique, the time difference between the main and slave signals is measured, and the time difference is displayed on a time difference display 11.

As explained above, according to the present invention, since AGC is not required, there is no need to provide a control loop for each of the Loran signals of the four stations necessary for position measurement, and there is no need to include a circuit with a time constant. It has advantages such as stability, low cost, and high response speed.

[Brief explanation of drawings]

FIG. 1 is an embodiment of the present invention, FIG. 2 is a waveform diagram for explaining the operation of FIG. 1, and FIG. 3 is a detailed explanatory diagram showing an example of the waveform converter 3 of FIG. 1. Meter... Waveform converter, 4, 7,
9... Limiter amplifier, 5... Transducer, 6...
Polarity switch, 8...Low pass filter, 9...Time difference measuring device.

Claims (1)

[Claims] 1. A receiving amplifier that receives and amplifies the Loran A signal, and converts the output waveform of the receiving amplifier so that it becomes zero at a point slightly ahead of the peak of the envelope of the output waveform, and the phase of the carrier wave is reversed before and after that, and the time difference is A waveform converter that serves as a reference point for measurement and a tracking target point, and a limiter amplifying the output of the waveform converter.A first limiter amplifier and a first limiter amplifier that converts the output of the receiving amplifier into the same phase, opposite phase, or with an appropriate period. a second limiter amplifier that outputs a signal having the same width and the same phase or opposite phase as the Loran A signal; and the output of the second limiter amplifier and the first limiter. A transducer that takes the product of the output of the amplifier, a low-pass filter that filters the output of the transducer to extract the envelope component, and amplifies the output of the low-pass filter and determines the output polarity at the tracking target point. between a third limiter amplifier that generates a rectangular wave with an inverted state, and respective tracking target points corresponding to received signals from two four-run transmitting stations that receive the output of the third limiter amplifier and are included therein. 1. A Loran A receiver, comprising: a time difference measuring device that measures the time difference between and uses the Loran A time difference measurement value as a Loran A time difference measurement value.