Circuit system for expanding working temperature range of radio frequency measuring instrument

Through the combination of reference voltage generation circuit, temperature sensor and comparison control circuit, the heating of the RF measurement instrument in a low temperature environment is solved, and the problem of the instrument not working at low temperatures is solved, reducing costs and simplifying the circuit design.

CN119200714APending Publication Date: 2024-12-27TRANSCOM INSTR
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Patent Information

Application Number
CN202411190401.8
Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
Filing Date
2024-08-28
Publication Date
2024-12-27

AI Technical Summary

Technical Problem

RF measurement instruments do not work properly in low temperature environments, existing solutions are expensive or increase development and production cycles, and require expensive power converters.

Method used

The circuit system is adopted that includes reference voltage generation circuit, temperature sensor, comparison control circuit and resistance heater heating circuit. The temperature is converted into resistance value through the temperature sensor, and the comparison control circuit controls the resistance heater heating to realize the low temperature environment of instrument components. heating.

Benefits of technology

It realizes the normal operation of the RF measurement instrument in a low temperature environment. The circuit structure is simple and reliable, and the cost is low. It supports a wide AC-DC input voltage range without the need for MCU temperature control programs and expensive power converters.

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Abstract

The invention relates to a circuit system for expanding the working temperature range of a radio frequency measuring instrument, which comprises a reference voltage generation circuit, a temperature sensor, a comparison control circuit and a resistance heater heating circuit, and is characterized in that the reference voltage generation circuit inputs alternating current and direct current voltage from the outside of the instrument to take electricity and generate base voltage VREF and direct current voltage VDC; the temperature sensor is used for converting temperature into resistance values in one-to-one correspondence, the comparison control circuit outputs a control signal for controlling the resistance heater heating circuit to be turned on or turned off through the resistance value of the temperature sensor, and the resistance heater heating circuit is used for heating parts which cannot work under a low-temperature condition in the instrument. According to the circuit system for expanding the working temperature range of the radio frequency measuring instrument, the circuit structure is simple and reliable, the cost is low, a wide alternating current and direct current input voltage range is supported, start-stop control over the heating circuit is achieved through a pure hardware circuit, and an expensive power converter capable of working at low temperature does not need to be provided for an MCU.
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Description

Technical Field

[0001] The present invention relates to the field of wireless communication technology, in particular to the field of temperature control technology, and specifically refers to a circuit system for realizing extended operating temperature range of a radio frequency measuring instrument. Background Art

[0002] Requirements: These test scenarios require that RF measuring instruments can work normally in a temperature range as low as -10℃ or even -40℃. However, RF measuring instruments are usually designed for use in laboratory environments, and the normal working temperature range is very narrow, generally working in the temperature range of 0℃ to 55℃. Under temperature conditions below this temperature range, the instrument may not be able to achieve the calibrated performance indicators, or even be unable to start up.

[0003] To solve the problem that RF measuring instruments cannot work properly at low temperatures, there are usually two existing solutions. One is to design RF measuring and testing instruments by selecting components that can work normally under low temperature conditions (such as -40°C). The second is to heat internal temperature-sensitive components (such as power modules, circuit boards, etc.) through temperature control circuits to reach a suitable operating temperature.

[0004] The disadvantage of Option 1 is that key components of RF instruments that support low-temperature operation (such as FPGA chips, high-speed ADC chips, and signal chain devices) are usually expensive and difficult to obtain, which will significantly increase the cost of the instrument.

[0005] For the second solution, the existing technical implementation solution usually controls the heating process by an MCU (microcontroller) in conjunction with an external temperature acquisition circuit. Figure 1 It is a common general temperature control solution based on MCU. This solution has disadvantages. First, it increases the product development and production cycle. Second, because the field test instrument is usually powered by 220V AC generated by a generator or 110V DC generated by a lead-acid battery, and the MCU operating voltage is generally not more than 5V, it cannot be directly powered from the outside of the instrument. Therefore, it is necessary to design a power converter for the MCU that can work in a low temperature environment. Summary of the invention

[0006] The purpose of the present invention is to overcome the above-mentioned shortcomings of the prior art and provide a circuit system that is simple, reliable, low-cost, and has a wide range of applications for extending the operating temperature range of a radio frequency measuring instrument.

[0007] In order to achieve the above object, the circuit system of the present invention for realizing the expansion of the operating temperature range of the radio frequency measuring instrument is as follows:

[0008] The circuit system for expanding the working temperature range of a radio frequency measuring instrument has the following main features: the system includes a reference voltage generating circuit, a temperature sensor, a comparison control circuit and a resistance heater heating circuit; the output end of the reference voltage generating circuit is connected to the comparison control circuit, the output end of the temperature sensor is connected to the comparison control circuit, and the output end of the comparison control circuit is connected to the resistance heater heating circuit; the reference voltage generating circuit takes power from an AC / DC voltage input from the outside of the instrument to generate a base voltage VREF and a DC voltage VDC, and transmits them to the comparison control circuit and the resistance heater heating circuit; the temperature sensor is used to convert the temperature into a one-to-one corresponding resistance value, and uses the resistance value as an input signal of the comparison control circuit; the comparison control circuit outputs a control signal for controlling the resistance heater heating circuit to be turned on or off through the resistance value of the temperature sensor; and the resistance heater heating circuit is used to heat components inside the instrument that cannot work under low temperature conditions.

[0009] Preferably, the reference voltage generating circuit comprises a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, a first capacitor C1, a second capacitor C2, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5 and a reference chip U1, the cathode of the first diode D1 and the anode of the third diode D3 are connected to VIN+, the cathode of the second diode D2 and the anode of the fourth diode D4 are connected to VIN-, the anodes of the first diode D1 and the second diode D2 are connected to the reference ground, and the cathodes of the third diode D3 and the fourth diode D4 are connected to VD C, the first capacitor C1 is connected between VDC and the reference ground, one end of the first resistor R1 is connected to VDC, and the other end is connected to node A, one end of the second resistor R2 is connected to the reference ground, and the other end is connected to node A, one end of the third resistor R3 is connected to VREF, and the other end is connected to node A, one end of the fourth resistor R4 is connected to VREF, and the other end is connected to node B, one end of the fifth resistor R5 is connected to the reference ground, and the other end is connected to node B, one pin of the reference chip U1 is connected to VREF, another pin is connected to node B, and the last pin is connected to the reference ground, and the second capacitor C2 is connected between VREF and the reference ground.

[0010] Preferably, the temperature sensor comprises a thermistor R8, one end of which is connected to a reference ground, and the other end of which is connected to a node IN.

[0011] Preferably, the comparison control circuit includes a sixth resistor R6, a seventh resistor R7, a first field effect transistor Q1, a third capacitor C3, a comparator chip U2, a ninth resistor R9, a second field effect transistor Q2 and a tenth resistor R10, one end of the sixth resistor R6 is connected to VREF, and the other end is connected to node IN, one end of the seventh resistor R7 is connected to node IN, and the other end is connected to the drain of the first field effect transistor Q1, one end of the third capacitor C3 is connected to node IN, and the other end is connected to the reference ground, the base of the first field effect transistor Q1 is connected to node OUT, the drain is connected to the seventh resistor R7, and the source is connected to the reference ground, one end of the ninth resistor R9 is connected to VREF, and the other end is connected to node C, the drain of the second field effect transistor Q2 is connected to node OUT, the base is connected to node C, and the source is connected to the reference ground, one end of the tenth resistor R10 is connected to VREF, and the other end is connected to node OUT, one pin of the comparator chip U2 is connected to node IN, another pin is connected to the reference ground, and the last pin is connected to node C.

[0012] Preferably, the resistance heater heating circuit includes a field effect transistor Q3, a solid-state relay U3, an eleventh resistor R11, a fuse FU1 and a twelfth resistor R12, the base of the field effect transistor Q3 is connected to the node OUT, the source is connected to the reference ground, and the drain is connected to the second pin of the solid-state relay U3, the first pin of the solid-state relay U3 is connected to the resistor R11, the second pin is connected to the drain of the field effect transistor Q3, the third pin is connected to the heating resistor R12, and the fourth pin is connected to the fuse FU1, one end of the eleventh resistor R11 is connected to the first pin of the solid-state relay U3, and the other end is connected to VREF, one end of the fuse FU1 is connected to VIN+, and the other end is connected to the fourth pin of the solid-state relay U3, one end of the twelfth resistor R12 is connected to VIN-, and the other end is connected to the third pin of the solid-state relay U3.

[0013] Preferably, the twelfth resistor R12 of the resistance heater heating circuit and the thermistor R8 of the temperature sensor are installed closely on the housing of the temperature-sensitive component.

[0014] The circuit system of the present invention is used to realize the expansion of the working temperature range of the radio frequency measuring instrument. The circuit structure is simple and reliable, the cost is low, and a wide AC and DC input voltage range is supported. There is no need to write an MCU temperature control program. The pure hardware circuit realizes the start and stop control of the heating circuit, and there is no need to provide the MCU with an expensive power converter that can work at low temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a general temperature control solution based on MCU in the prior art.

[0016] Figure 2 The present invention is a schematic diagram of the structure of a circuit system for expanding the operating temperature range of a radio frequency measuring instrument.

[0017] Figure 3 The present invention is a schematic diagram of the installation positions of a heating resistor heater and a thermistor of a circuit system for implementing a circuit system for extending the operating temperature range of a radio frequency measuring instrument.

[0018] Figure 4 This is a relationship diagram between the working state of the heating circuit and the temperature in an embodiment of the circuit system for realizing the expansion of the working temperature range of the radio frequency measuring instrument of the present invention. DETAILED DESCRIPTION

[0019] In order to more clearly describe the technical content of the present invention, further description is given below in conjunction with specific embodiments.

[0020] The circuit system for realizing the expansion of the working temperature range of the radio frequency measuring instrument of the present invention comprises a reference voltage generating circuit, a temperature sensor, a comparison control circuit and a resistance heater heating circuit, wherein the output end of the reference voltage generating circuit is connected to the comparison control circuit, the output end of the temperature sensor is connected to the comparison control circuit, and the output end of the comparison control circuit is connected to the resistance heater heating circuit; the reference voltage generating circuit takes power from the AC and DC voltages input from the outside of the instrument, generates a base voltage VREF and a DC voltage VDC, and transmits them to the comparison control circuit and the resistance heater heating circuit, the temperature sensor is used to convert the temperature into a one-to-one corresponding resistance value, and uses the resistance value as the input signal of the comparison control circuit, the comparison control circuit outputs a control signal for controlling the resistance heater heating circuit to be turned on or off through the resistance value of the temperature sensor, and the resistance heater heating circuit is used to heat the components inside the instrument that cannot work under low temperature conditions.

[0021] As a preferred embodiment of the present invention, the reference voltage generating circuit includes a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, a first capacitor C1, a second capacitor C2, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5 and a reference chip U1, the cathode of the first diode D1 and the anode of the third diode D3 are connected to VIN+, the cathode of the second diode D2 and the anode of the fourth diode D4 are connected to VIN-, the anodes of the first diode D1 and the second diode D2 are connected to the reference ground, and the cathodes of the third diode D3 and the fourth diode D4 are connected to the reference ground. connected to VDC, the first capacitor C1 is connected between VDC and the reference ground, one end of the first resistor R1 is connected to VDC, and the other end is connected to node A, one end of the second resistor R2 is connected to the reference ground, and the other end is connected to node A, one end of the third resistor R3 is connected to VREF, and the other end is connected to node A, one end of the fourth resistor R4 is connected to VREF, and the other end is connected to node B, one end of the fifth resistor R5 is connected to the reference ground, and the other end is connected to node B, one pin of the reference chip U1 is connected to VREF, another pin is connected to node B, and the last pin is connected to the reference ground, and the second capacitor C2 is connected between VREF and the reference ground.

[0022] As a preferred embodiment of the present invention, the temperature sensor comprises a thermistor R8, one end of which is connected to a reference ground and the other end of which is connected to a node IN.

[0023] As a preferred embodiment of the present invention, the comparison control circuit includes a sixth resistor R6, a seventh resistor R7, a first field effect transistor Q1, a third capacitor C3, a comparator chip U2, a ninth resistor R9, a second field effect transistor Q2 and a tenth resistor R10, one end of the sixth resistor R6 is connected to VREF, and the other end is connected to node IN, one end of the seventh resistor R7 is connected to node IN, and the other end is connected to the drain of the first field effect transistor Q1, one end of the third capacitor C3 is connected to node IN, and the other end is connected to the reference ground, the base of the first field effect transistor Q1 is connected to node OUT, the drain is connected to the seventh resistor R7, and the source is connected to the reference ground, one end of the ninth resistor R9 is connected to VREF, and the other end is connected to node C, the drain of the second field effect transistor Q2 is connected to node OUT, the base is connected to node C, and the source is connected to the reference ground, one end of the tenth resistor R10 is connected to VREF, and the other end is connected to node OUT, one pin of the comparator chip U2 is connected to node IN, another pin is connected to the reference ground, and the last pin is connected to node C.

[0024] As a preferred embodiment of the present invention, the resistance heater heating circuit includes a field effect transistor Q3, a solid-state relay U3, an eleventh resistor R11, a fuse FU1 and a twelfth resistor R12, the base of the field effect transistor Q3 is connected to the node OUT, the source is connected to the reference ground, and the drain is connected to the second pin of the solid-state relay U3, the first pin of the solid-state relay U3 is connected to the resistor R11, the second pin is connected to the drain of the field effect transistor Q3, the third pin is connected to the heating resistor R12, and the fourth pin is connected to the fuse FU1, one end of the eleventh resistor R11 is connected to the first pin of the solid-state relay U3, and the other end is connected to VREF, one end of the fuse FU1 is connected to VIN+, and the other end is connected to the fourth pin of the solid-state relay U3, one end of the twelfth resistor R12 is connected to VIN-, and the other end is connected to the third pin of the solid-state relay U3.

[0025] As a preferred embodiment of the present invention, the twelfth resistor R12 of the resistance heater heating circuit and the thermistor R8 of the temperature sensor are installed closely on the housing of the temperature-sensitive component.

[0026] In a specific implementation of the present invention, the operating temperature range of the radio frequency measuring instrument is expanded in a low-cost manner to ensure that the radio frequency measuring instrument can work normally in a low temperature (eg, -40°C) environment.

[0027] The present invention discloses a circuit for extending the operating temperature range of a radio frequency measuring instrument. Figure 2 As shown, it includes a reference voltage generating circuit, a thermistor (temperature sensor), a comparison control circuit and a resistance heater heating circuit.

[0028] The reference voltage generation circuit takes power from the AC and DC voltages input from the outside of the instrument to generate a reference voltage VREF for the subsequent comparison control circuit, a DC voltage VDC, and a DC voltage VDC for the resistance heater heating circuit.

[0029] The thermistor is used to convert temperature into a one-to-one corresponding resistance value, which serves as an input signal for a comparison control circuit.

[0030] The comparison control circuit uses the resistance value (i.e., temperature) of the thermistor to output a control signal for turning on or off the heating circuit of the resistance heater.

[0031] The resistance heater heating circuit is used to heat the internal parts of the instrument that cannot work under low temperature conditions.

[0032] In the present invention, in the reference voltage generating circuit, the cathode of the first diode D1 and the anode of the third diode D3 are connected to VIN+, the cathode of the second diode D2 and the anode of the fourth diode D4 are connected to VIN-; the anodes of the first diodes D1 and D2 are connected to the reference ground, and the cathodes of the third diodes D3 and D4 are connected to VDC; the capacitor C1 is connected across VDC and the reference ground; one end of the first resistor R1 is connected to VDC, and the other end is connected to node A; one end of the second resistor R2 is connected to the reference ground, and the other end is connected to node A; one end of the resistor R3 is connected to VREF, and the other end is connected to node A; one end of the resistor R4 is connected to VREF, and the other end is connected to node B; one end of the resistor R5 is connected to the reference ground, and the other end is connected to node B; pin 1 of the reference chip U1 is connected to VREF, pin 2 is connected to node B, and pin 3 is connected to the reference ground; the capacitor C2 is connected across VREF and the reference ground.

[0033] In the present invention, one end of the thermistor R8 is connected to the reference ground, and the other end is connected to the node IN.

[0034] In the present invention, in the comparison control circuit, one end of the resistor R6 is connected to VREF, and the other end is connected to the node IN;

[0035] One end of the seventh resistor R7 is connected to the node IN, and the other end is connected to the drain of the field effect transistor Q1; one end of the capacitor C3 is connected to the node IN, and the other end is connected to the reference ground; the base of the field effect transistor Q1 is connected to the node OUT, the drain is connected to the seventh resistor R7, and the source is connected to the reference ground;

[0036] Pin 3 of the comparator chip U2 is connected to the node IN, pin 2 is connected to the node C, and pin 1 is connected to the reference ground; one end of the resistor R9 is connected to VREF, and the other end is connected to the node C; the drain of the field effect transistor Q2 is connected to the node OUT, the base is connected to the node C, and the source is connected to the reference ground; one end of the resistor R10 is connected to VREF, and the other end is connected to the node OUT;

[0037] In the present invention, in the heating circuit of the resistance heater, the base of the field effect tube Q3 is connected to the node OUT, the source is connected to the reference ground, and the drain is connected to the pin 2 of the solid-state relay U3; the pin 1 of the solid-state relay U3 is connected to the resistor R11, the pin 2 is connected to the base of the field effect tube Q3, the pin 3 is connected to the heating resistor R12, and the pin 4 is connected to the fuse FU1; one end of the resistor R11 is connected to the pin 1 of the solid-state relay U3, and the other end is connected to VREF; one end of the fuse FU1 is connected to VIN+, and the other end is connected to the pin 4 of the solid-state relay U3; one end of the resistor R12 is connected to VIN-, and the other end is connected to the pin 3 of the solid-state relay U3;

[0038] In particular, the main components inside the radio frequency measuring instrument, such as the radio frequency circuit and the high-speed ADC / DAC circuit, usually have a closed aluminum alloy shielding cover, the baseband circuit usually also has an aluminum alloy heat sink, and the power module has an aluminum alloy shell. In the present invention, the resistance heater R12 and the thermistor R8 are installed closely to the shells of these temperature-sensitive components, as shown in the attached Figure 3 shown.

[0039] In this embodiment, the wide-voltage AC or DC power input from the external power supply is converted into a DC voltage by the rectifier bridge circuit composed of four diodes D1, D2, D3, and D4, and a relatively stable DC voltage VDC is obtained after filtering by C2; then the voltage-dividing resistor network composed of R1 and R2 divides VDC appropriately and provides it to the reference voltage VREF conversion circuit composed of R3, R4, R5, and U1. In particular, the value of the reference voltage VREF depends on the output voltage of the U1 chip pin 2 and the ratio of the resistors R4 and R5. The specific VREF voltage value can be calculated by the following formula:

[0040]

[0041] Where V is the output voltage of pin 2 of voltage reference chip U1.

[0042] In this embodiment, the voltage reference chip U1 adopts TL431 of TI Company, and R4=R5, then VREF=4.950V;

[0043] In this embodiment, the comparator chip U2 is XC61CN2502MR-G produced by TOREX. When the voltage of the circuit node IN is greater than 2.5V, the chip outputs a high level, otherwise it outputs a low level.

[0044] When the temperature is low, the resistor R8 is small, and the voltage of the circuit node IN is lower than 2.5V. The circuit node C is driven to a low level by U2, the field effect tube Q2 is in the cut-off state, the circuit node OUT is at a high level, the field effect tube Q1 is turned on, the solid-state relay U3 is closed, the resistor R12 starts to be energized and heated, and the field effect tube Q1 is turned on, further lowering the voltage of the node IN, maintaining the heating working state of the resistor R12;

[0045] When the temperature is high, the resistance of resistor R8 increases with the increase of temperature, the voltage of circuit node IN exceeds 2.5V, circuit node C is high level, field effect tube Q2 is turned on, circuit node OUT is low level, field effect tube Q3 is turned off, the solid-state relay is disconnected, and resistor R12 stops heating after power is cut off. At the same time, field effect tube Q1 is turned off, further pushing up the voltage of node IN and maintaining the resistor R12 in the stopped heating working state.

[0046] Attached Figure 4This is the relationship between the ambient temperature and the working state of the heating resistor R12 in this embodiment. By selecting appropriate resistance values ​​of R6 and R7, the temperature threshold for starting and stopping heating can be set.

[0047] The main technical principle of the technical solution of the present invention is to convert the temperature into voltage through thermistor R8, and then output the voltage to the comparison circuit composed of R6, R7, Q1, C3, U2, R9, R10, and Q2; when the temperature is low, the resistor R8 is small, the circuit node C is driven by U2 to a low level, the field effect tube Q2 is in a cut-off state, the circuit node OUT is high, the field effect tube Q1 is turned on, the solid-state relay U3 is closed, the resistor R12 starts to be powered on for heating, and the field effect tube Q1 is turned on, further pulling down the voltage of the node IN, and maintaining the heating working state of the resistor R12; when the temperature is high, the resistance of the resistor R8 increases with the increase of the temperature, the circuit node C is high, the field effect tube Q2 is turned on, the circuit node OUT is low, the field effect tube Q3 is turned off, the solid-state relay is disconnected, the resistor R12 stops heating after power failure, and the field effect tube Q1 is turned off, further pushing up the node IN voltage, and maintaining the resistor R12 to stop heating working state. It can be seen that through the feedback of the OUT node, the comparison circuit has a bistable characteristic. This feature allows the case to set two temperature thresholds Tmin and Tmax through a comparison control circuit and a temperature sensor. When the temperature is low, heating starts until the temperature exceeds Tmax, then heating stops; when the temperature is high, heating stops until the temperature drops below Tmin, then heating starts.

[0048] The bistable comparison control circuit in the technical solution of the present invention has strong resistance to external interference and natural stability, and will not cause oscillation of the heating circuit control signal and the heating circuit to start and stop back and forth.

[0049] The specific implementation scheme of this embodiment can refer to the relevant description in the above embodiment, which will not be repeated here.

[0050] It can be understood that the same or similar parts of the above embodiments can be referenced to each other, and the contents not described in detail in some embodiments can refer to the same or similar contents in other embodiments.

[0051] It should be noted that, in the description of the present invention, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. In addition, in the description of the present invention, unless otherwise specified, the meaning of "plurality" refers to at least two.

[0052] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0053] The circuit system of the present invention is used to realize the expansion of the working temperature range of the radio frequency measuring instrument. The circuit structure is simple and reliable, the cost is low, and a wide AC and DC input voltage range is supported. There is no need to write an MCU temperature control program. The pure hardware circuit realizes the start and stop control of the heating circuit, and there is no need to provide the MCU with an expensive power converter that can work at low temperatures.

[0054] In this specification, the present invention has been described with reference to specific embodiments thereof. However, it is apparent that various modifications and variations may be made without departing from the spirit and scope of the present invention. Therefore, the specification and drawings should be regarded as illustrative rather than restrictive.

Claims

1. A circuit system for extending the operating temperature range of a radio frequency measuring instrument, characterized in that: The system includes a reference voltage generating circuit, a temperature sensor, a comparison control circuit and a resistance heater heating circuit. The output end of the reference voltage generating circuit is connected to the comparison control circuit, the output end of the temperature sensor is connected to the comparison control circuit, and the output end of the comparison control circuit is connected to the resistance heater heating circuit. The reference voltage generating circuit takes power from the AC and DC voltages input from the outside of the instrument to generate a base voltage VREF and a DC voltage VDC, and transmits them to the comparison control circuit and the resistance heater heating circuit. The temperature sensor is used to convert the temperature into a one-to-one corresponding resistance value, and use the resistance value as the input signal of the comparison control circuit. The comparison control circuit outputs a control signal to control the resistance heater heating circuit to turn on or off through the resistance value of the temperature sensor. The resistance heater heating circuit is used to heat the components inside the instrument that cannot work under low temperature conditions.

2. The circuit system for realizing the expansion of the operating temperature range of the radio frequency measuring instrument according to claim 1, characterized in that: The reference voltage generating circuit includes a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, a first capacitor C1, a second capacitor C2, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5 and a reference chip U1, the cathode of the first diode D1 and the anode of the third diode D3 are connected to VIN+, the cathode of the second diode D2 and the anode of the fourth diode D4 are connected to VIN-, the anodes of the first diode D1 and the second diode D2 are connected to the reference ground, and the cathodes of the third diode D3 and the fourth diode D4 are connected to VDC, The first capacitor C1 is connected between VDC and the reference ground, one end of the first resistor R1 is connected to VDC, and the other end is connected to node A, one end of the second resistor R2 is connected to the reference ground, and the other end is connected to node A, one end of the third resistor R3 is connected to VREF, and the other end is connected to node A, one end of the fourth resistor R4 is connected to VREF, and the other end is connected to node B, one end of the fifth resistor R5 is connected to the reference ground, and the other end is connected to node B, one pin of the reference chip U1 is connected to VREF, another pin is connected to node B, and the last pin is connected to the reference ground, and the second capacitor C2 is connected between VREF and the reference ground.

3. The circuit system for realizing the expansion of the operating temperature range of the radio frequency measuring instrument according to claim 1, characterized in that: The temperature sensor includes a thermistor R8, one end of which is connected to a reference ground, and the other end of which is connected to a node IN.

4. The circuit system for realizing the expansion of the operating temperature range of the radio frequency measuring instrument according to claim 1, characterized in that: The comparison control circuit includes a sixth resistor R6, a seventh resistor R7, a first field effect transistor Q1, a third capacitor C3, a comparator chip U2, a ninth resistor R9, a second field effect transistor Q2 and a tenth resistor R10. One end of the sixth resistor R6 is connected to VREF, and the other end is connected to node IN. One end of the seventh resistor R7 is connected to node IN, and the other end is connected to the drain of the first field effect transistor Q1. One end of the third capacitor C3 is connected to node IN, and the other end is connected to the reference ground. The base of the first field effect transistor Q1 is connected to node OUT, the drain is connected to the seventh resistor R7, and the source is connected to the reference ground. One end of the ninth resistor R9 is connected to VREF, and the other end is connected to node C. The drain of the second field effect transistor Q2 is connected to node OUT, the base is connected to node C, and the source is connected to the reference ground. One end of the tenth resistor R10 is connected to VREF, and the other end is connected to node OUT. One pin of the comparator chip U2 is connected to node IN, another pin is connected to the reference ground, and the last pin is connected to node C.

5. The circuit system for realizing the expansion of the operating temperature range of the radio frequency measuring instrument according to claim 1, characterized in that: The resistance heater heating circuit includes a field effect tube Q3, a solid-state relay U3, an eleventh resistor R11, a fuse FU1 and a twelfth resistor R12. The base of the field effect tube Q3 is connected to the node OUT, the source is connected to the reference ground, and the drain is connected to the second pin of the solid-state relay U3. The first pin of the solid-state relay U3 is connected to the resistor R11, the second pin is connected to the drain of the field effect tube Q3, the third pin is connected to the heating resistor R12, and the fourth pin is connected to the fuse FU1. One end of the eleventh resistor R11 is connected to the first pin of the solid-state relay U3, and the other end is connected to VREF. One end of the fuse FU1 is connected to VIN+, and the other end is connected to the fourth pin of the solid-state relay U3. One end of the twelfth resistor R12 is connected to VIN-, and the other end is connected to the third pin of the solid-state relay U3.

6. The circuit system for realizing the extension of the operating temperature range of the radio frequency measuring instrument according to claim 1, characterized in that: The twelfth resistor R12 of the resistance heater heating circuit and the thermistor R8 of the temperature sensor are installed closely on the housing of the temperature-sensitive component.