JP2003078372A - Gain abnormality detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect an input level and an output level of an amplifier and prevent an error determination according to a difference in characteristics of each level detection part when determining normality/abnormality of an amplifier gain from the difference. SOLUTION: Output values DIN, DOUT of respective detection parts 10, 11 with respect to each high frequency input level when an amplifier 100 is normal are measured, and the output values are stored in an offset table 109 together with an offset value ΔDS as the difference. When operating, the offset value equivalent to an output value DIN or DOUT of the detection part 10 or 11 is acquired from the table 109 to add this to the output value DOUT of the detection part 11 for correction. Based on whether or not a difference between this correction value and the output value DIN of the detection part 10 is a threshold or more, it is determined that the gain of the amplifier is normal/abnormal.

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a gain abnormality detecting device for detecting a gain abnormality of a common amplifying device. 2. Description of the Related Art FIG. 2 is a block diagram of a conventional gain abnormality detecting device. In the figure, a directional coupler 101, an input level detector 10, a directional coupler 102, an output level detector 1
1. The comparator 12 constitutes a gain abnormality detection device. The high-frequency signal passes through the directional coupler 101 and passes through the amplifier 100
And output via the directional coupler 102.
When the gain of the amplifier 100 becomes an abnormal value, it is detected as soon as possible and an alarm is generated by an abnormal gain detecting device. For this purpose, the input is branched by the directional coupler 101 and added to the input level detection unit 10. In the input level detector 10, the level of the input high-frequency signal is detected by the detector 103, digitized by the input A / D converter 105, and output to the comparator 12. The output high-frequency signal is branched by the directional coupler 102 and applied to the output level detector 11. In the output level detector 11, the detector 104 detects the level of the output high-frequency signal, and the output A / D converter 106
And outputs it to the comparison unit 12. Comparison section 12
Is constituted by a microprocessor 107. Here, when the amplifier 100 is operating normally, the degree of coupling of each of the directional coupler 101 and the directional coupler 102 is controlled, or although not shown, the directional coupler 102 is controlled. By providing an attenuator (attenuator) between and the detector 103 and controlling it, the input high-frequency signal level applied to the detector 103 and the output high-frequency signal level applied to the detector 104 become the same level. Keep it. Then, when the amplifier 100 is normal, the output of the input A / D converter 105 and the output of the output A / D converter 106 are at the same level. The microprocessor 107 compares the input high-frequency signal level of the digital value from the input A / D converter 105 with the output high-frequency signal level of the digital value from the output A / D converter 106, and the level difference is predetermined. If the difference is equal to or less than the threshold value, it is determined that the signal is normal.
0 is determined to be abnormal, and a gain abnormality process such as generating an alarm is performed. As described above, the technique of comparing the input level and the output level of an amplifier and determining whether the level difference exceeds a threshold value and determining whether the amplifier is normal / abnormal is based on, for example, a special switching device. -308234 and special opening and closing 11
It is also disclosed in -274874. [0005] According to the above-mentioned prior art, when the detection characteristics of the detector 103 and the detector 104 vary, an error may occur in the determination of the gain of the amplifier 100. FIG. 3 shows an example of the input / output characteristics of the detector. The horizontal axis represents the relative level L (db) obtained by standardizing the high-frequency level input to the detector with a reference level (for example, 0 dbm).
The vertical axis indicates the detector output voltage V. The input high-frequency level of both detectors 103 and 104 is -15 db
In the above description, the characteristics are almost linear and the same output value is given.
03 has a higher output voltage. FIG. 4 is an example of digital output values DIN and DOUT of the input level detection unit 10 and the output level detection unit 11 when such detectors 103 and 104 are used. In this case, as described above, it is assumed that the high-frequency input levels to the respective level detectors are adjusted to have the same value. FIG. 4 shows that the input high frequency level L is -15d.
Above b, if the amplifier 100 is operating normally, the two inputs DIN and DOUT to the comparison unit 12 will always be the same value.
Means that the gain has changed. Therefore, the comparison unit 12 determines that the amplifier 100 is abnormal when the difference ΔD between the two inputs becomes equal to or more than the threshold value “7”, for example. However, if the input high-frequency level is -15 db or less, there will be a difference between the output digital DIN and DOUT even if the input high-frequency level is the same, due to the difference in the characteristics of the two detectors. For this reason,
The following problems occur. First, assuming that the input high frequency level L is -20 db and the amplifier 100 is normal, the input A / D converter 105
, The digital output value DOUT of the output A / D converter 106 becomes “95”, and the difference ΔD between the two inputs of the comparator 12 becomes “10”. Comparison section 1
Assuming that the threshold value of the abnormality determination in Step 2 is “7”, the comparison unit 12 determines that the amplifier is abnormal even though the amplifier operates normally. Also, the input high frequency level is -25 db
, The output digital value D of the input A / D converter 105
IN is "80", but output A / D
The output digital value DOUT of the converter 106 is "6" in FIG.
It is assumed that it is "81" instead of "0". This DOUT = 8
1 means that the high-frequency level input to the detector 104 was −22 db when interpolated by linear approximation from the table of FIG. That is, since the gain should be -25 db when the amplifier is normal, it indicates that the gain of the amplifier is 3 db larger than that when the amplifier is normal. If the detector 104 has the same characteristics as the detector 103, the digital output value at the time of the input level of −22 db should be “4” if it is obtained by interpolation.
5 ". In this case, the difference Δ = 95−80 = 15 between the two inputs to the comparison unit 12 is determined to be abnormal. However, if the above characteristics differ, Δ = 81−80 = 1, and the amplifier is determined to be normal. SUMMARY OF THE INVENTION An object of the present invention is to provide a gain abnormality detecting device which determines whether a gain characteristic is normal or abnormal based on a difference between input and output levels of an amplifier. An object of the present invention is to provide a gain abnormality detecting device capable of making a determination. In order to achieve the above object, the present invention provides an input level detector for detecting an input level to an amplifier, and an output level detector for detecting an output level of the amplifier. A gain abnormality detection device comprising: a comparator and a comparator for comparing the output of the input level detector with the output of the output level detector to determine whether the gain of the amplifier is normal. During the normal operation of the amplifier, the input level detection unit output value measured for each amplifier input level and the output level detection unit output value and an offset table that stores in advance the difference between these measured values as an offset value, An offset value corresponding to the output of the input level detector or the output level detector is obtained from the offset table, A correction means for adding a value to the output level detection section output to calculate a correction value of the output level detection section output; and a difference between the correction value obtained by this means and the input level detection section output being predetermined. And a determination unit that determines that the gain of the amplifier is normal when the difference is smaller than the threshold value and determines that the gain is abnormal when the difference is larger than the threshold value. Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a configuration example of a gain abnormality detection device according to the present invention. The directional coupler 101, an input level detector 10, a directional coupler 102, and an output level detector 1 are shown.
1. Comparing section 13. This configuration corresponds to the comparison unit 1
3 differs from the conventional configuration of FIG. 2 only in that the other components are the same, and the same circuits are denoted by the same reference numerals. The comparison unit 13 includes a microprocessor 110 and a memory 108, and the memory 108 is provided with an offset table 109 which is a feature of the present invention. In the configuration of FIG. 1, the directional coupler 101
By controlling the degree of coupling of each of the directional coupler 102 and the directional coupler 102, or by providing an attenuator (not shown) between the directional coupler 102 and the detector 104 and adjusting it, the amplifier 100 The input high-frequency signal level LIN applied to the detector 103 during normal operation and the output high-frequency signal level LOUT applied to the detector 104 are the same. After this adjustment, the output digital values DIN and DOUT of the input level detection unit 10 and the output level detection unit 11 are measured while the input high-frequency level is changed while the amplifier 100 is in a normal state. Calculated as ΔDS, and these are stored in the offset table 109. FIG. 5 shows an example of the offset table in which the two detectors 103 and 104 have the characteristics shown in FIG. The measurement points of the input high frequency level (relative value) L are the same as those in FIG.
At the six points of 5, -10, -15, -20, and -25 (db), the characteristics of the two detectors are the same as in FIG. 4, so that the outputs DIN and DOUT of the detectors are the same as in FIG. 15db
Differences in characteristics are seen below. Therefore, the offset value ΔDS takes a non-zero value in this different region. The offset value ΔD obtained from the table 109
S represents a characteristic difference between the two detectors. Therefore, the sum of the output value DOUT of the output level detector 11 and the offset value ΔDS measured during operation is a value obtained by detecting the output level of the amplifier 100 using a detector having the same characteristics as the detector 103 on the input side and digitizing the same. Is corrected to
If the added value is regarded as the output of the detection unit 11 and compared with the output of the detection unit 10, the gain fluctuation of the amplifier can be detected in a state where there is no characteristic difference between the two detectors. Next, the operation of the gain abnormality detecting device of FIG.
This will be described using the operation flow shown in FIG. This process is executed by the microprocessor 110. First, the output value of the input level detection unit 10 and the output value of the output level detection unit 11 are periodically obtained (STEP 20).
1). The offset table 109 is accessed and the output value DIN of the input level detector 10 or the output level detector 1
An offset value ΔDS corresponding to the output value DOUT of 1 is obtained (STEP 202). For example, if the output value DIN of the input level detector 10 is "160", the offset value .DELTA.DS
Is “0”, and if DIN is “105”, the offset value ΔD
S becomes "10". Next, the obtained offset value Δ
DS is added to the output value DOUT of the output level detecting unit 11 (STEP 203), and the added value and the input level detecting unit 1 are added.
A difference Δ from the output value DIN of 0 is obtained, and it is checked whether or not the difference Δ is equal to or larger than a predetermined threshold (step 20).
4). If the difference Δ is smaller than the threshold value (N in STEP 204
O) The amplifier 100 is determined to be normal and does nothing. If the difference Δ is equal to or larger than the threshold (YES in STEP 204), it is determined that the gain of the amplifier 100 is abnormal, and a gain abnormality process such as alarming is performed (STEP 205). For example, it is assumed in STEP 201 that the output value DIN of the input level detector 10 is "105" and the output value DOUT of the output level detector 11 is "95".
If the offset value is not added as in the conventional method, the difference between the output “105” of the input level detection unit 10 and the output “95” of the output level detection unit 11 is “1”.
0 ". When the threshold value is set to “7”, the amplifier 10
Although 0 is operating normally, an erroneous judgment is made as abnormal. On the other hand, in the case of the present invention, the offset value extracted from the offset table 109 is “10”.
5 ", the added value becomes" 105 "(STEP 2).
03), the difference Δ from the output of the input level detection unit 10 in STEP 204 is “0”. Therefore, it is determined that the amplification of the amplifier 100 is performed normally (STEP 204).
NO). Thus, according to the present invention, it is possible to avoid erroneously determining a normal state as abnormal. In step 201, the output value DIN of the input level detector 10 is "80", and the output level detector 1
In the case where the output value DOUT of 1 is "81", the amplifier 100 is determined to be normal because the conventional method simply determines based on the difference "1" between the two output values. On the other hand, in the present invention, the offset value extracted from the offset table 109 is “20” (STEP 202). When this value is added to the output value “81” of the output level detection unit 11, the added value becomes “101” (STEP 203), and STEP 204
Is "21" from the output of the input level detection unit 10 at the time. For this reason, if the threshold for judging the abnormality is “7”, it is judged that the gain of the amplifier 100 is abnormal (STEP 2).
04, YES), abnormal gain processing such as alarm transmission (STE
P205). Thus, according to the present invention, it is possible to prevent an abnormal state from being erroneously determined to be normal. The offset table 109 stores the input level of the input level detector 10 for some input high-frequency levels.
The output value of the output level detector 11 is measured and tabulated. If the actually measured input level or output of the output level detector is not on this table, the data in the offset table 109 is used to perform interpolation processing. Find the offset value. The simplest interpolation method is linear interpolation, which is as follows. Now, when calculating the offset value from the output value DIN detected by the input level detection unit 10, the following equation is obtained for the detected value DIN = a. Table 1 shows two adjacent output values x1 and x2 satisfying
09 and the offset values corresponding to x1 and x2 are y1 and y2, respectively. Then the detected value a
The offset value ΔDS = b for is obtained by the following equation: For example, when the offset table 109 is as shown in FIG.
Is “90”, x1 = 80, x2 = 105, y1
= 20 and y2 = 10 It becomes. In the description of the offset table 109 shown in FIG.
To control the degree of coupling of the directional coupler 102 so that the input level to the output level detector 11 and the input level to the output level detector 11 become the same value, or to provide an attenuator between the directional coupler 102 and the output level detector 11 And However, the present invention does not necessarily require such adjustment. If there is a difference between the outputs of the two level detectors 10 and 11 when the amplifier is normal,
The value may be added to the offset value ΔDS of the offset table 109 as it is. According to the present invention, the input level detection unit 10
Even when a detector having different input / output characteristics is used for the output level detector 11 and the output level detector 11, it is possible to compensate for variations in the characteristics of the detector. It is no longer determined to be normal despite being abnormal, and a gain abnormality detection device free from malfunction can be realized. Further, since it is not necessary to use detectors having the same characteristics for the input level detecting section 10 and the output level detecting section 11, an economical abnormality detecting apparatus can be constructed. Further, when the amplifier 100 is normal, it is not necessary to finely adjust the input of the input level detection unit 10 and the input of the output level detection unit 11 so that the output value becomes the same value. Installation and adjustment are extremely easy.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a configuration example of a gain abnormality detection device according to the present invention. FIG. 2 is a block diagram of a conventional gain abnormality detection device. FIG. 3 is an example of input / output characteristics of a detector. FIG. 4 is an example of input / output characteristics of an input / output level detection unit. FIG. 5 is an example of an offset table. FIG. 6 is a flowchart of an abnormality detection process in a comparison unit. [Description of Signs] 10 Input level detection unit 11 Output level detection unit 12 Comparison unit 101, 102 Directional coupler 103, 104 Detector 105 Input A / D converter 106 Output A / D converter 107 Microprocessor 108 Memory 109 Offset table

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Claims (1)

1. An input level detector for detecting an input level to an amplifier, an output level detector for detecting an output level of the amplifier, an output of the input level detector, and the output level. A gain abnormality detection device comprising: a comparison unit that determines whether or not the gain of the amplifier is normal by comparing the output of the detection unit. An offset table in which a difference between the measured input level detector output value and the output level detector output value and the measured value is stored in advance as an offset value,
During operation, an offset value corresponding to the output of the input level detection unit or the output level detection unit is obtained from the offset table, and this offset value is added to the output of the output level detection unit to correct the output level detection unit output. When the difference between the correction value calculated by this means and the output of the input level detection unit is smaller than a predetermined threshold, the gain of the amplifier is determined to be normal, and the difference is larger than the threshold. A determining means for determining that the gain is abnormal when the gain is large;