CN112067873A - Self-balancing bridge circuit for millimeter wave power meter - Google Patents
Self-balancing bridge circuit for millimeter wave power meter Download PDFInfo
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- CN112067873A CN112067873A CN202010745009.0A CN202010745009A CN112067873A CN 112067873 A CN112067873 A CN 112067873A CN 202010745009 A CN202010745009 A CN 202010745009A CN 112067873 A CN112067873 A CN 112067873A
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- operational amplifier
- thermistor
- triode
- millimeter wave
- power meter
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- 239000003990 capacitor Substances 0.000 claims description 9
- 238000001514 detection method Methods 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 238000013459 approach Methods 0.000 description 2
- 239000011358 absorbing material Substances 0.000 description 1
- 230000003321 amplification Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 238000003199 nucleic acid amplification method Methods 0.000 description 1
- 230000010355 oscillation Effects 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R17/00—Measuring arrangements involving comparison with a reference value, e.g. bridge
- G01R17/10—AC or DC measuring bridges
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R21/00—Arrangements for measuring electric power or power factor
- G01R21/02—Arrangements for measuring electric power or power factor by thermal methods, e.g. calorimetric
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- General Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Measuring Temperature Or Quantity Of Heat (AREA)
Abstract
The invention discloses a self-balancing bridge circuit for a millimeter wave power meter, which comprises a reference resistor, a thermistor and a comparison module, wherein the reference resistor and the thermistor are respectively connected with the comparison module, the thermistor is arranged on a millimeter wave power meter chip and used for detecting the working temperature of the chip, and the comparison module comprises a first operational amplifier, a first diode, a first triode, a second operational amplifier, a second diode and a second triode.
Description
Technical Field
The invention belongs to the technical field of bridge circuits, and relates to a self-balancing bridge circuit for a millimeter wave power meter.
Background
With the wide application of millimeter wave technology, the need for accurate measurement of millimeter wave power is becoming more urgent. The millimeter wave power measurement technology can be mainly divided into diode detection and calorimetric measurement. The wave detection type power meter can quickly measure millimeter wave power, but is limited by the working principle of the wave detection type power meter, and cannot accurately calibrate the millimeter wave power through calorimetric reference.
The thermistor in the sensor matched with the heat measuring type millimeter wave power meter does not directly absorb millimeter wave power, the temperature of the chip rises as the wave absorbing material on the chip absorbs millimeter waves, and the resistance value of the thermistor on the circuit layer changes correspondingly, so that the sensor is also called as an indirectly heated thermistor power sensor. If the thermistor is biased to a specific resistance value by the direct current power in advance before the millimeter wave power is not added and is kept unchanged in a closed-loop control mode, the direct current power is automatically reduced by the closed-loop circuit to maintain the circuit balance after the millimeter wave power is added.
At present, the closed-loop control circuit actually adopted by the power meter is very complex, firstly, a Wheatstone bridge is used for measuring a deviation signal, and after amplification, parameter setting is carried out through a regulator, and the main defects are as follows: when the wheatstone bridge is used for measuring deviation, all resistors are not connected into the bridge in a four-wire mode, so that the direct-current power of resistor loss in balance cannot be accurately calculated according to the voltages at two ends of the bridge, and therefore a self-balancing bridge circuit for the millimeter wave power meter, which can solve the problems, is needed.
Disclosure of Invention
The invention aims to provide a self-balancing bridge circuit for a millimeter wave power meter, which aims to solve the problem of closed-loop control of a power meter connected with an indirectly heated thermistor power sensor.
The invention comprises a reference resistor and a thermistor, and comprises a comparison module, wherein the reference resistor and the thermistor are respectively connected with the comparison module, the thermistor is arranged on a millimeter wave power meter chip and used for detecting the working temperature of the chip, the comparison module comprises a first operational amplifier, a first diode, a first triode, a second operational amplifier, a second diode and a second triode, the first end and the second end of the reference resistor are respectively connected with the negative input end of the first operational amplifier and the positive input end of the second amplifier, the first end and the second end of the thermistor are respectively connected with the negative input end of the second operational amplifier and the positive input end of the first operational amplifier, the output end of the first operational amplifier is connected with the negative end of the first diode, the positive end of the first diode is connected with the base electrode of the first triode, the emitting electrode of the first triode is connected with the first end of the reference resistor, the collecting electrode of the first triode is connected with the first end of the thermistor, the output end of the second operational amplifier is connected with the negative end of the second diode, the positive end of the second diode is connected with the base electrode of the second triode, the emitting electrode of the second triode is connected with the second end of the thermistor, and the collecting electrode of the second triode is connected with the second end of the reference resistor.
Further, the thermistor is connected with a first capacitor in parallel.
Further, the first operational amplifier and the second operational amplifier are both provided with adjustable resistors.
Furthermore, two adjustable resistors are connected in series with a grounded capacitor.
Compared with the prior art, the invention has the following beneficial effects:
the resistor is connected by four wires, wherein two wires are used for providing loop current, and the other two wires are used for measuring voltage at two ends of the resistor, so that the influence caused by lead resistance is reduced to be ignored. The parameter adjustment is convenient, only needs to change the balanced speed through changing the electric capacity size, need not to adjust other electric capacity inductances.
Drawings
FIG. 1 is a schematic diagram of a self-balancing bridge circuit for a millimeter wave power meter;
Detailed Description
The technical solutions of the embodiments of the present invention are clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As shown in fig. 1, the present invention includes a reference resistor Rt900 and a thermistor 102, and includes a comparison module, the reference resistor Rt900 and the thermistor 102 are respectively connected to the comparison module, the thermistor 102 is disposed on the millimeter wave power meter chip for detecting the operating temperature of the chip, the comparison module includes a first operational amplifier U101, a first diode D101, a first triode Q101, a second operational amplifier U102, a second diode D102 and a second triode Q102, a first end and a second end of the reference resistor Rt900 are respectively connected to a negative input end of the first operational amplifier U101 and a positive input end of the second operational amplifier U102, a first end and a second end of the thermistor 102 are respectively connected to a negative input end of the second operational amplifier U102 and a positive input end of the first operational amplifier U101, an output end of the first operational amplifier U101 is connected to a negative end of the first diode D101, the positive pole end of the first diode U101 is connected with the base of the first triode Q101, the emitting pole of the first triode Q101 is connected with the first end of the reference resistor, the collecting pole of the first triode Q101 is connected with the first end of the thermistor, the output end of the second operational amplifier U102 is connected with the negative pole end of the second diode D102, the positive pole end of the second diode D102 is connected with the base of the second triode Q102, the emitting pole of the second triode Q102 is connected with the second end of the thermistor 102, and the collecting pole of the second triode Q102 is connected with the second end of the reference resistor Rt 900.
The thermistor 102 is connected in parallel with a first capacitor C1.
The first operational amplifier U101 and the second operational amplifier U102 are both provided with adjustable resistors.
And two adjustable resistors are connected with a grounding capacitor (C102 and C104) in series.
U101 and U102 are operational amplifiers, and the same potential difference between two ends of two resistors is realized by utilizing the characteristic that the potentials of differential input ends are the same. When the loop is balanced, the current automatically adjusts the thermistor value to make the resistance value equal to the reference resistance value. At this time, the potential difference at the differential input end of the first operational amplifier U101 approaches zero, the potential difference at the differential input end of the second operational amplifier U102 approaches zero, and the potential differences at the two ends of the two resistors are equal. Because the two resistors have the same current on the same current loop, the resistance value of the thermistor is stabilized on the fixed resistance value of the reference resistor.
The base electrode of the triode is connected with the output of the operational amplifier, and the base electrode current of the triode is controlled through the output of the first operational amplifier U101 and the second operational amplifier U102 to realize the adjustment of the loop current.
Rt-900 is a reference resistor, and the resistance of the thermistor is fixed to the resistance of Rt-900 when the bridge circuit is balanced.
The thermistor is designed on a chip in the power sensor and is connected to the power meter through a cable when the millimeter wave power is measured, the resistance value of the thermistor is stabilized on the resistance value of the reference resistor under the control of the circuit, the direct current balance power of the thermistor is changed due to the absorbed millimeter wave power, and the substitute power measured by the power meter can be used for representing the millimeter wave power absorbed by the sensor.
The invention avoids the complexity of a servo circuit, simplifies the PID parameter setting process, and the reference resistor and the thermistor are connected in a four-wire mode and are not limited by the length of a lead.
The standard resistance of the power meter is directly related to the accuracy of the direct current alternative power, and the precise resistance with high precision and high temperature stability is selected in the embodiment to play a key role in the precision of the power meter. During design, a high-precision high-stability resistor is adopted, the precision of the resistor is 0.01%, and the temperature coefficient is less than 5ppm omega/DEG C.
Because the operational amplifier plays a role in maintaining the potential difference between the two ends of the standard resistor and the resistor to be tested to be equal in the circuit, the open-loop gain of the operational amplifier must be very large, and meanwhile, the current of a loop is determined by the differential voltage of the operational amplifier, so that the operational amplifier must have a very high common-mode rejection ratio, and the influence of the common-mode voltage can be reduced. In addition, the op-amp should have a very small offset voltage. The cost and the performance are comprehensively considered, and the OP-07 operational amplifier with high gain and low offset voltage is adopted.
In the circuit, two ends of a thermistor are connected with a large-capacitance electrolytic capacitor in parallel, and the function of the large-capacitance electrolytic capacitor is to eliminate the oscillation of a circuit loop. Because the measuring object of the power meter has certain heat capacity, when the change of the current in the loop cannot cause the change of the resistance value in real time, certain inertia delay always exists, and therefore, the two ends of the resistance are connected with a large capacitor in parallel to reduce the instantaneous change value of the current. According to a number of experimental verifications, the final capacitance was chosen to be 1000 μ F.
It will be appreciated by those of ordinary skill in the art that the embodiments described herein are intended to assist the reader in understanding the principles of the invention and are to be construed as being without limitation to such specifically recited embodiments and examples. Those skilled in the art can make various other specific changes and combinations based on the teachings of the present invention without departing from the spirit of the invention, and these changes and combinations are within the scope of the invention.
Claims (4)
1. A self-balancing bridge circuit for a millimeter wave power meter is characterized by comprising a reference resistor and a thermistor and a comparison module, wherein the reference resistor and the thermistor are respectively connected with the comparison module, the thermistor is arranged on a millimeter wave power meter chip and used for detecting the working temperature of the chip, the comparison module comprises a first operational amplifier, a first diode, a first triode, a second operational amplifier, a second diode and a second triode, a first end and a second end of the reference resistor are respectively connected with a negative input end of the first operational amplifier and a positive input end of the second operational amplifier, a first end and a second end of the thermistor are respectively connected with a negative input end of the second operational amplifier and a positive input end of the first operational amplifier, an output end of the first operational amplifier is connected with a negative end of the first diode, the positive pole end of the first diode is connected with the base of the first triode, the emitting electrode of the first triode is connected with the first end of the reference resistor, the collecting electrode of the first triode is connected with the first end of the thermistor, the output end of the second operational amplifier is connected with the negative pole end of the second diode, the positive pole end of the second diode is connected with the base of the second triode, the emitting electrode of the second triode is connected with the second end of the thermistor, and the collecting electrode of the second triode is connected with the second end of the reference resistor.
2. A self-balancing bridge circuit for a millimeter wave power meter in accordance with claim 1, wherein: the thermistor is connected with a first capacitor in parallel.
3. A self-balancing bridge circuit for a millimeter wave power meter in accordance with claim 1, wherein: the first operational amplifier and the second operational amplifier are both provided with adjustable resistors.
4. A self-balancing bridge circuit for a millimeter wave power meter in accordance with claim 3, wherein: and the two adjustable resistors are connected with a grounding capacitor in series.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010745009.0A CN112067873A (en) | 2020-07-29 | 2020-07-29 | Self-balancing bridge circuit for millimeter wave power meter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010745009.0A CN112067873A (en) | 2020-07-29 | 2020-07-29 | Self-balancing bridge circuit for millimeter wave power meter |
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| Publication Number | Publication Date |
|---|---|
| CN112067873A true CN112067873A (en) | 2020-12-11 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN202010745009.0A Withdrawn CN112067873A (en) | 2020-07-29 | 2020-07-29 | Self-balancing bridge circuit for millimeter wave power meter |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114785288A (en) * | 2022-06-20 | 2022-07-22 | 中国空气动力研究与发展中心低速空气动力研究所 | Amplifier power supply circuit of balance bridge and bridge amplifying circuit |
-
2020
- 2020-07-29 CN CN202010745009.0A patent/CN112067873A/en not_active Withdrawn
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114785288A (en) * | 2022-06-20 | 2022-07-22 | 中国空气动力研究与发展中心低速空气动力研究所 | Amplifier power supply circuit of balance bridge and bridge amplifying circuit |
| CN114785288B (en) * | 2022-06-20 | 2022-09-30 | 中国空气动力研究与发展中心低速空气动力研究所 | Amplifier power supply circuit of balance bridge and bridge amplifying circuit |
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Application publication date: 20201211 |