JPH0949872A - Receiving device of interrogator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent erroneous operation applying an offset value fluctuated by a noise level on the side of a SUM or DIFF channel to an SUM or DIFF signal level to remove the adverse effect of noise. SOLUTION: An inputted SUM channel signal is converted to a indigital signal by an A/D converter 5 to be inputted to one input terminal of a comparator 11 and also inputted to an A/D converter 7 through a smoothing device 6. The output of the A/D converter 7 is inputted to an offset value forming device 8 and the offset value corresponding to the value is outputted to be inputted to one input terminal of an adder 10. An inputted DIFF channel signal is converted into a digital signal by an A/D converter 9 to be inputted to the other input terminal of the adder 10. Two inputted signals are added by the adder 10 to be inputted to the other input terminal of the comparator 11. The comparator 11 outputs a receiving video signal when the SUM channel signal is judged to be larger than the DIFF channel signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a SUM having directivity in a secondary radar in which the interrogator receives a response signal output from a transponder in response to an interrogation signal from an interrogator. Level comparison between the SUM channel signal from the antenna and the DIFF channel signal from the omnidirectional DIFF antenna,
The present invention relates to an interrogator receiving device that recognizes a response signal from the transponder, and more particularly to an interrogator receiving device that has a noise removal function and can prevent malfunction.

[0002]

2. Description of the Related Art Generally, in the field of air traffic control, as shown in FIG. 4, when an interrogator (interrogator) 1 mounted on a fixed station or a mobile unit on the ground outputs an interrogation signal, the interrogation signal is transmitted to the aircraft. A transponder (responder) 2 mounted on the same or the like receives, generates and outputs a response signal according to the content of the inquiry signal, and the interrogator 1 receives the response signal to detect the position of the aircraft or the like. Secondary radars are known. Normally, the receiving device of the interrogator 1 has two antennas for receiving the response signal, one of which is a SUM antenna having directivity,
The other is a DIF having a directional pattern zero point (pole) in a direction in which the directional pattern of the SUM antenna is maximized.
It is an F antenna. The SUM antenna and DIFF
The antenna pattern of the antenna is shown in FIG.

In the receiving device, the S
In order to determine whether or not the transponder 2 is present in the direction pattern of the UM antenna, as shown in FIG.
A SUM channel signal in which the RF signal from the UM antenna is converted into a video signal, which is attenuated by the attenuator 3, and a DIF in which the RF signal from the DIFF antenna is converted into a video signal.
The F channel signal is compared by the comparator 4. Then, the received video signal is output by the comparator 4 in accordance with the result of the comparison.

To explain the above operation in detail, the response signal from the transponder 2 arrives at the interrogator 1.
When the directivity pattern of the SUM antenna is oriented in the direction of the transponder 2, a SUM channel signal and a DIFF channel signal respectively appear as shown in FIG. 7 (a). Since the level difference of the DIFF channel signal is large, even if the signal obtained by attenuating the SUM channel signal by +12 dB in the circuit shown in FIG. 6 and the DIFF channel signal are compared, the level on the SUM channel side is large, so that the received video is It is generated and output from the comparator 4.

On the other hand, when the directivity pattern of the SUM antenna is oriented in a direction different from that of the transponder 2, as shown in FIG. 7B, the SUM channel signal, D
The IFF channel signals respectively appear. In this case, since the level difference between the SUM channel signal and the DIFF channel signal is small, the SU shown in the circuit of FIG.
DI is applied after attenuating +12 dB on the M channel signal.
Since the level on the SUM channel side is smaller than that of the FF channel, the received video is not generated and is not output.
In this way, it is determined whether or not the transponder 2 is present in the directivity pattern direction of the SUM antenna.

However, in an environment where noise such as an interfering signal exists in the radio wave propagation path and the level thereof is large, the directivity pattern of the SUM antenna is directed toward the transponder as shown in FIG. 7C. Nevertheless, DI
On the FF channel side, the noise reception level L2 is higher than that of the response signal from the transponder 2,
Comparing the level L1 of the SUM channel signal and the level L2 of the DIFF channel signal in the circuit shown in FIG. 6, the difference between the two levels is small (L1-L2 <1
2 dB), the received video is not generated by the comparator 4,
As a result, the directional pattern of the SUM antenna shown in FIG. 7B is the same as when it is oriented in a direction different from that of the transponder 2, resulting in a malfunction.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an interrogator receiving apparatus capable of preventing malfunction by having a noise removing function.

[0008]

In order to achieve the above object, the present invention provides a SUM channel signal from a SUM antenna having directivity in an interrogator of a secondary radar having an interrogator (interrogator) and a responder (transponder). And DI from omnidirectional DIFF antenna
A receiving device of an interrogator for recognizing a response signal from the transponder by comparing the levels of FF channel signals, the SUM channel side or the DIFF
Means for measuring the noise level on the channel side, offset value generating means for outputting an offset value that varies according to the measured noise level, and adverse effect of the noise by giving an offset to the signal level of the DIFF channel or the SUM channel. And a means for removing the noise level, the offset value generating means, when the noise level is larger than a preset value,
It is characterized in that the offset value is reduced and outputted.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on illustrated embodiments. FIG. 1 is a block diagram showing an embodiment of a receiving device of an interrogator (interrogator) according to the present invention. In Fig. 1, this interrogator (interrogator)
The receiving device of the first receives the first SUM channel signal.
A / D converter 5, a smoother 6 to which a SUM channel signal is input, a second A / D converter 7 connected to the smoother 6, and a second A / D converter 7 is connected to the offset value generator 8, the third A / D converter 9 to which the DIFF channel signal is input, and the offset value generator 8 and the third A / D converter 9 are connected. It has a configuration including an adder 10 and a comparator 11 connected to the first A / D converter 5 and the adder 10.

Next, the basic operation of the receiving apparatus having the above-mentioned structure will be described. The input SUM channel signal is converted into a digital signal by the first A / D converter 5 and then by the comparator 11. It is input to one of the input terminals.
At the same time, the input SUM channel signal is
It is input to the second A / D converter 7 via the smoother 6, and the output of the second A / D converter 7 is input to the offset value generating device 8 as described later. An offset value corresponding to the value is output and input to one input terminal of the adder 10.

On the other hand, the input DIFF channel signal is converted into a digital signal by the third A / D converter 9 and input to the other input terminal of the adder 10. Then, the two input signals are added by the adder 10 and input to the other input terminal of the comparator 11. Then, the comparator 11 outputs the received video signal when it determines that the SUM channel signal is large.

The noise removing operation of the receiving apparatus will be described. First, as shown in FIG. 2, the noise level of the SUM channel is measured before the interrogator outputs the interrogation signal. That is, as shown in FIG. 2, the SUM channel signal containing only the noise signal, which is input shortly before the interrogation signal is generated, is smoothed by the smoother 6 and the noise level thereof is averaged. It is digitized by the second A / D converter 7 and input to the offset value generation device 8. Then, the offset generation device 8 generates an offset value of +12 dB when the noise level is sufficiently low, and outputs the offset value to the adder 10. When the noise level is higher than a preset value, the offset value is set. The reduced value (for example, 6 dB) is output to the adder 10.

As a result of the above operation, as shown in FIG. 3, the reception level L2 of noise is large and the difference between the level L1 of the response signal received by the SUM antenna and the level L2 of the signal received by the DIFF antenna is 12 dB> L1-L2. In the case of> 6 dB, in the conventional case, since the difference between the SUM channel signal level L1 and the DIFF channel signal level L2 is small, the reception video is not generated by the comparator, resulting in a malfunction. Since the DIFF channel signal level L2 is reduced by the decrease of the offset value, the level difference between the two signals is secured to a large value, and it can be recognized that the response signal has arrived.
The received video is output from the comparator 11.

Although the present invention has been described with reference to the embodiment in which two offset values (12 dB, 6 dB) are switched according to the noise level, the present invention is not limited to this, and the offset according to the noise level. The value may be changed stepwise and finely.
For example, if the offset value generating device 8 is configured to output the value stored in advance in the memory as the offset value by using the output of the second A / D converter 7 as the address, A stepwise change can be realized.

In the above embodiment, the offset value is determined based on the SUM channel signal.
The offset value may be determined based on the FF channel signal. Further, in the above embodiment, a signal obtained by subtracting the signal output from the offset value generating device 8 from the signal digitized by the first A / D converter 5 and the third A / D converter You may compare with the digitized signal in 9. Further, in the above embodiment, the noise level of the SUM channel may be measured a plurality of times and an averaged signal may be used.
The time for measuring the noise level may be any time other than the reception timing.

[0016]

INDUSTRIAL APPLICABILITY As described above, according to the present invention, in an interrogator receiving apparatus, noise such as an interfering signal exists in the radio wave propagation path, and even if the noise level is large, S
Since the amount of attenuation used when comparing the level difference between the received signal from the UM antenna and the received signal from the DIFF antenna is changed from the conventional fixed amount to the variable amount, the noise removal function is achieved and malfunction occurs. It can be prevented.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a receiving device of an interrogator (interrogator) according to the present invention.

FIG. 2 is a timing chart of noise level measurement of a SUM channel in the receiving device shown in FIG.

3 is an operation timing chart when the noise level in the receiving apparatus shown in FIG. 1 is high.

FIG. 4 is a schematic explanatory diagram of a secondary radar.

5 is a schematic explanatory diagram showing antenna patterns of a SUM antenna and a DIFF antenna of the secondary radar shown in FIG.

FIG. 6 is a schematic configuration diagram of a conventional interrogator receiving device.

7 (a), (b) and (c) are operation timing charts of the receiving apparatus shown in FIG.

[Explanation of symbols]

1 ... Interrogator, 2 ... Transponder, 3 ... Attenuator,
4 ... Comparator, 5, 7, 9 ... First, second and third A /
D converter, 6 ... smoother,
8 ... Offset value generator, 10 ... Adder,
11 ... comparator,

Claims (2)

[Claims] 1. A SUM channel signal from a SUM antenna having directivity and a DI from an omnidirectional DIFF antenna in an interrogator of a secondary radar having an interrogator (interrogator) and a transponder (transponder).
A receiving device of an interrogator for recognizing a response signal from the transponder by comparing the levels of FF channel signals, the SUM channel side or the DIFF
Means for measuring the noise level on the channel side, offset value generating means for outputting an offset value that varies according to the measured noise level, and adverse effect of the noise by giving an offset to the signal level of the DIFF channel or the SUM channel. And a means for removing the interrogator. 2. The offset value generating means is the SU.
When the noise level on the M channel side is higher than a preset value, the offset value is reduced and output in order to give an offset to the signal level of the DIFF channel. Receiving device of the described interrogator.