Radio frequency voltage measuring device, measuring method and calibrating method based on thin film thermal variable resistor

Abstract

The invention provides a radio frequency voltage measuring device, a measuring method and a calibrating method based on a thin film thermal variable resistor. The device comprises an upper electrode, a first mica sheet, a middle electrode, a second mica sheet and a lower electrode which are stacked in sequence, the middle electrode comprises two pieces of metal, and a gap is formed between the two pieces of metal; a coaxial connector, a central conductor and a lead electrode shaft nail are fixed on the upper electrode; the coaxial connector and the central conductor are used for feeding a radio frequency signal into the middle electrode; one surface, facing the lower electrode, of the middle electrode is provided with two thermal variable resistors which are electrically connected with the two pieces of metal respectively; two lead electrode shaft nails penetrate through the upper electrode and are inserted into the two pieces of metal of the middle electrode, so that the thin film thermistor on the middle electrode is connected with an external direct current self-balancing bridge; the lead electrode shaft nail is isolated from the upper electrode through an insulating sleeve; and the lower electrode is connected with to-be-tested equipment. The two mica sheets are clamped among the upper electrode, the middle electrode and the lower electrode, so that a 5nF-50nF structural capacitor is provided for a radio frequency voltage measuring device. The structure capacitor not only provides a radio frequency loop for the radio frequency voltage standard device, so that the radio frequency signal and the direct current bias signal do not interfere with each other, and the measurement accuracy is further improved.

Description

Technical Field

[0001] This invention relates to the field of radio frequency voltage measurement technology, specifically to a radio frequency voltage measurement device, measurement method, and calibration method based on thin-film thermistor. Background Technology

[0002] Radio frequency (RF) voltage measurement plays a crucial role in various high-frequency applications such as communications, radar, and metrology. Compared to DC and low-frequency voltages, RF voltage measurement presents greater challenges. Firstly, RF voltages typically operate in the 3GHz or higher frequency range, necessitating the use of coaxial connectors in RF voltmeters to ensure wideband measurement. In this context, impedance matching between the RF voltage standard and the RF voltmeter becomes critical; mismatch will result in significant errors. Secondly, due to the high frequency of RF voltages, transmission line effects exist, meaning the voltage at different points on the transmission line is not uniform. Therefore, it is only meaningful if the RF voltage standard and the RF voltmeter measure voltages on the same plane.

[0003] Currently, radio frequency voltage measurement mainly relies on the following technical principles:

[0004] 1. Thermocouple method

[0005] Principle: The heat generated by the radio frequency current flowing through the heating wire causes the connected thermocouple to generate a thermoelectric potential (voltage). This DC voltage is proportional to the square of the effective value (RMS) of the radio frequency current, thus indirectly obtaining the radio frequency voltage value.

[0006] Implementation: Typically, a miniature thermocouple element is placed in a coaxial transmission line or probe to ensure good impedance matching (usually 50Ω).

[0007] Disadvantages: (1) It is easily overloaded and burns out, and is very fragile. (2) It has a slow response speed and cannot track rapidly changing signals. (3) It requires a certain amount of warm-up time to reach stability.

[0008] 2. Diode Detection Method

[0009] Principle: Utilizing the nonlinear current-voltage characteristic of a diode to detect radio frequency signals. Depending on the magnitude of the input signal, it operates in two modes:

[0010] Square-law detection (small signal): When the input voltage is very small (<-20dBm), the diode operates in the curved part of its characteristic curve, and the output DC voltage is proportional to the square of the input RF voltage (i.e., power). This is also a true RMS response.

[0011] Linear detection (large signal): When the input voltage is large, the diode performs envelope detection on the signal, and the output DC voltage is proportional to the peak value of the input RF voltage. This is not a true RMS response, and its reading will introduce errors for non-sinusoidal waves.

[0012] Implementation: Peak detection circuits (such as series diodes and parallel capacitors) are typically used to capture the peak value of the signal. Modern instruments use precisely calibrated diode detectors and compensate for their nonlinearity through digital processing.

[0013] Disadvantages: (1) Non-true RMS response (in the linear region of large signals), resulting in large measurement errors for non-sinusoidal waves.

[0014] (2) The sensitivity is low for small signals and there is a square law conversion error.

[0015] (3) It is sensitive to temperature and requires a temperature compensation circuit.

[0016] (4) The measurement accuracy is usually lower than that of thermoelectric and thermistor methods.

[0017] 3. Sampling method

[0018] Principle: The waveform of the radio frequency signal is directly sampled through ultra-high-speed sampling technology, then converted into a digital signal by an ADC (analog-to-digital converter), and finally calculated in the digital domain to obtain various parameters such as the peak value, average value, and RMS value of the voltage.

[0019] Equivalent-time sampling: For repetitive signals, a sampling clock much lower than the signal frequency is used to "reconstruct" a complete signal cycle through multiple samples. This was the core principle of early digital oscilloscopes and sampling oscilloscopes.

[0020] Real-time sampling: Using an ultra-high-speed ADC to directly capture the instantaneous value of a signal, effective for both single and non-repeating signals. This is the core technology of modern high-performance real-time oscilloscopes.

[0021] Implementation: Requires extremely complex and precise high-speed integrated circuit (IC) design.

[0022] Disadvantages: (1) Bandwidth and sampling rate limitations: The bandwidth and sampling rate of a real-time oscilloscope determine its maximum measurement frequency, and it is extremely expensive.

[0023] (2) Relatively low accuracy: The vertical resolution (e.g., 8-bit) and noise of the ADC limit the absolute accuracy of voltage measurement and are usually not used as a metrology standard.

[0024] (3) Input impedance: The input impedance of a high-bandwidth active probe changes drastically with frequency, which can affect the circuit under test.

[0025] 4. Thermistor / Power Meter Method

[0026] Principle: This is essentially a radio frequency power measurement, which is then calculated using a formula. (where R is the characteristic impedance, usually 50Ω) to calculate the voltage.

[0027] The resistance of components such as thermistors or thermopiles changes with the heat generated by the absorbed radio frequency power. By constructing a bridge circuit and measuring the change in resistance, the radio frequency power can be accurately measured.

[0028] Features: This is currently the most accurate method for measuring radio frequency power (from which voltage can be derived), and it is often used as a standard for metrology and calibration.

[0029] Disadvantages: (1) The response is very slow, and it can only measure average power / voltage, and cannot reflect instantaneous changes.

[0030] (2) Manual zeroing and calibration are required, which is cumbersome.

[0031] (3) The system is relatively complex and costly.

[0032] In summary, traditional voltage measurement devices are significantly affected by temperature, and measurements at room temperature are prone to large drift errors. Traditional radio frequency voltage measurement devices also have long measurement times, typically exceeding 30 seconds, making the results more susceptible to temperature drift and resulting in poor measurement repeatability. Summary of the Invention

[0033] The technical problem to be solved by this invention is how to improve the detection accuracy of radio frequency voltage measurement devices.

[0034] The present invention solves the above-mentioned technical problems through the following technical means:

[0035] A radio frequency voltage measurement device based on thin-film thermistors includes an upper electrode, a middle electrode, and a lower electrode stacked sequentially. The middle electrode comprises two metal lobes with a gap between them. The upper electrode is fixed with a coaxial connector, a center conductor, and lead electrode pins. The coaxial connector and the center conductor are used to feed radio frequency signals into the middle electrode. Two thermistors are provided on the side of the middle electrode facing the lower electrode, and the two thermistors are electrically connected to the two metal lobes respectively. The two lead electrode pins pass through the upper electrode and are inserted into the two metal lobes of the middle electrode, connecting the thin-film thermistors on the middle electrode to an external DC self-balancing bridge. The lead electrode pins are isolated from the upper electrode by an insulating sleeve. The lower electrode is connected to the device under test. A first mica sheet and a second mica sheet are inserted between the upper electrode, the middle electrode, and the lower electrode, respectively.

[0036] Furthermore, a groove is formed on the side of the lower electrode facing the middle electrode, and a surface-mount capacitor is fixed in the groove.

[0037] Furthermore, the two thermocouples are a pair of thermistors with identical performance deposited on a thin film, forming a thin-film thermocouple.

[0038] Furthermore, the lower electrode and the second mica sheet have a central hole, the planar dimensions of which are equal to or slightly larger than the planar dimensions of the thin-film thermocouple.

[0039] Furthermore, the center hole of the lower electrode has an internal thread, and a flat-to-coaxial N-type connector is threaded into the center hole.

[0040] Furthermore, a pressure plate is pressed into the central hole, and the pressure plate is squeezed by the flat end of the flat connector to the coaxial N-type connector, thereby fixing the thin film thermocouple.

[0041] Furthermore, the upper electrode, the first mica sheet, the middle electrode, the second mica sheet, and the lower electrode are fixed by bolts, and the bolts are fitted with insulating sleeves.

[0042] The present invention also provides a measurement method for an RF voltage measurement device based on a thin-film thermistor, comprising the following steps:

[0043] Step 1. Connect the two lead pins of the upper plate to the DC self-balancing bridge with connecting wires, and connect the thin-film thermistor to the DC self-balancing bridge; turn on the DC self-balancing bridge. The thin-film thermistor is connected in series with respect to the DC signal. The thin-film thermistor is a positive temperature coefficient thermistor. After the DC signal is applied, the resistor heats up and the resistance increases until the series resistance is balanced at 200Ω by the DC self-balancing bridge. At this time, the DC bias voltage of the DC self-balancing bridge is V1.

[0044] Step 2. Connect the RF signal source to the coaxial connector of the upper electrode via a coaxial cable. When an RF signal is applied, the two thermistors are connected in parallel relative to the RF signal. The upper electrode, middle electrode, and mica sheet together form a 5nF~50nF structural capacitor C2, and the middle electrode, lower electrode, and mica sheet together form a 5nF~50nF structural capacitor C3, forming an RF circuit. Since the thermistors absorb RF power, their resistance increases. In order to maintain the series resistance of the thermistors at 200Ω, the DC bias voltage of the DC self-balancing bridge will automatically decrease to maintain bridge balance. At this time, the DC bias voltage is V2.

[0045] Step 3. According to the law of conservation of energy, the power of the added radio frequency signal is equivalent to the power of the reduced DC signal:

[0046]

[0047] In the formula, P rf It is the added radio frequency power, P sub It is the DC power substitution, that is, the DC power reduced after the bridge is rebalanced; Rdc It is the series resistance of thermistors R1 and R2;

[0048] The measured radio frequency voltage can be expressed as:

[0049]

[0050] In the formula, V rf R is the measured radio frequency voltage. rf It is the parallel resistance of thermistors R1 and R2;

[0051] The radio frequency voltage on the measuring end face can be determined using the above method.

[0052] This invention also provides a method for calibrating the radio frequency voltmeter under test in a radio frequency voltage measuring device based on a thin-film thermistor. A flat-top to coaxial N-type connector is connected to the lower electrode, with the flat-top end in close contact with the thin-film thermistor and the coaxial N-type end connected to the radio frequency voltmeter under test. At this time, the radio frequency voltmeter under test and the thin-film thermistor of the radio frequency voltage measuring device measure the radio frequency voltage of the same end face; thus, the radio frequency voltage measuring device is used to calibrate the radio frequency voltmeter under test.

[0053] The advantages of this invention are:

[0054] This invention provides a 5nF to 50nF structural capacitor for the RF voltage measurement device by sandwiching two mica sheets between the upper, middle, and lower electrodes. This structural capacitor provides an RF circuit for the RF voltage standard device, preventing interference between the RF signal and the DC bias signal, thus further improving measurement accuracy. The invention employs a symmetrical dual-thermistor design, where two thermistors with similar resistance and sensitivity are respectively attached to the two halves of the middle electrode. The thermistors are connected to a DC self-balancing bridge via electrode pins to achieve DC substitution. The advantage of this design is that when the thermistors are balanced at 200Ω by the DC self-balancing bridge, their parallel resistance relative to the RF signal is 50Ω, thus providing good impedance matching, suitable for measuring coaxial RF voltmeters, and reducing mismatch errors when measuring RF voltage. The two electrode pins, multiple fixing bolts, and insulating sleeves facilitate the connection of the thin-film thermocouple on the middle electrode to the DC self-balancing bridge, while simultaneously fixing the relative positions of the electrodes, making the structure more stable and preventing short circuits between the electrodes.

[0055] Meanwhile, a slot is designed on the lower electrode to insert a chip capacitor (100nF to 1uF), thereby further expanding the structural capacitance of the RF voltage measurement device. Increasing the structural capacitance can also further extend the lower frequency limit of voltage measurement. The lower frequency limit of the RF voltage measurement device can reach 10MHz or lower, and the upper frequency limit can reach 6GHz or higher. Attached Figure Description

[0056] Figure 1 This is a schematic diagram of the structure of the radio frequency voltage standard device in an embodiment of the present invention;

[0057] Figure 2 , Figure 3 These are exploded views of the radio frequency voltage standard device from different perspectives in embodiments of the present invention;

[0058] Figure 4 This is a schematic diagram illustrating the working principle of the radio frequency voltage standard device in an embodiment of the present invention. Detailed Implementation

[0059] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0060] like Figure 1 , Figure 2 , Figure 3 As shown, the radio frequency voltage standard device in this embodiment adopts a three-layer structure design, consisting of an upper electrode 1, a middle electrode 2, and a lower electrode 3. A first mica sheet 4 and a second mica sheet 5 are respectively sandwiched between the upper, middle, and lower electrodes 3. The five-layer structure is fixed by bolts 6 passing through it in sequence. The bolts 6 are fitted with insulating sleeves 10 to prevent short circuits between the upper electrode 1 and the middle electrode 2, thus forming the main body of the device.

[0061] The upper electrode 1 is a flat cylindrical brass metal. The main components of the upper electrode 1 include a coaxial connector 7, a center conductor 8, an electrode pin 9, and an insulating sleeve 10. The coaxial connector 7 and the center conductor 8 are connected to the center of the upper electrode 1 and electrically connected to the middle electrode 2, and are used to feed radio frequency signals into the middle electrode 2.

[0062] The middle electrode 2 is the measurement end face of the radio frequency voltage. The middle electrode 2 consists of two semi-circular metal halves with a gap between them to prevent short circuits between the two electrodes. A thin-film thermistor (not shown in the figure) is placed at the center of the lower surface of the middle electrode 2 facing the lower electrode. The thin-film thermistor is at least one pair of thermistors with the same resistance and sensitivity, deposited on a thin film. The two thermistors are in contact with the two semi-circles of the middle electrode 2, respectively. A pair of lead electrode pins 9 pass through the upper electrode 1 and the first mica sheet 4, respectively, and are inserted into the two halves of the middle electrode 2, connecting the thin-film thermistors on the middle electrode 2 to an external DC self-balancing bridge. Insulating sleeves 10 are fitted onto the lead electrode pins 9 and the fixing bolts 6 to prevent short circuits between the middle electrode 2 and the upper electrode 1. The upper electrode 1, middle electrode 2, and mica sheet together form a structural capacitor of 5nF ​​to 50nF.

[0063] The lower electrode 3 is a flat cylindrical brass electrode with a certain thickness and a central hole. The second mica sheet 5 also has a central hole. These central holes facilitate the installation and removal of the thin-film thermocouple on the middle electrode 2. Therefore, the planar dimensions of the central hole are generally slightly larger than the thin-film thermocouple, and a circular shape is optimal for both the central hole and the thin-film thermocouple. After the thin-film thermocouple is installed, it is pressed tightly with a pressure plate 12, and a connector is threaded into the central hole. Devices under test, such as power sensors and voltmeters, can be connected to the RF voltage measurement device for calibration via the connector on the lower electrode 3. The middle electrode 2, lower electrode 3, and second mica sheet 5 together constitute a structural capacitor of 5nF ​​to 50nF. In this embodiment, two small grooves can be cut into the side of the lower electrode 3 facing the middle electrode 2. 100nF to 1uF surface-mount capacitors 11 can be placed in these grooves, with each capacitor 11 contacting the middle electrode. This further increases the structural capacitance of the RF voltage measurement device and extends its measurement frequency. To ensure stable contact between the surface mount capacitor 11 and the center electrode, a spring or spring sheet can be added inside the slot to keep the surface mount capacitor 11 pressed against the center electrode at all times.

[0064] The working principle of the radio frequency voltage measurement device in this embodiment is DC substitution, and its schematic diagram is as follows. Figure 4 As shown.

[0065] The radio frequency voltage measurement method is as follows:

[0066] Step 1: Install the thin-film thermistor on the middle electrode 2 of the RF voltage measuring device. The cold resistance of the pair of resistors R1 and R2 of the thin-film thermistor is typically 90Ω to 97Ω, and the series resistance is typically 180Ω to 195Ω. Connect the DC self-balancing bridge to the two lead pins 9 on the upper plate of the RF voltage measuring device using connecting wires. The two lead pins 9 are respectively connected to the two halves of the middle electrode 2, and the two thermistors on the thin-film thermistor are respectively attached to the two halves of the middle electrode 2. In this way, the thin-film thermistor is connected to the DC self-balancing bridge. Turn on the DC self-balancing bridge. The thin-film thermistor is in series with respect to the DC signal. The thin-film thermistor is a positive temperature coefficient thermistor. When a DC signal is applied, the resistor heats up, and the resistance increases until the series resistance is balanced at 200Ω by the DC self-balancing bridge. At this time, the DC bias voltage of the DC self-balancing bridge is V1.

[0067] Step 2: Connect the RF signal source to the coaxial connector 7 of electrode 1 on the RF voltage measuring device via a coaxial cable. When an RF signal is applied, the two thermistors are connected in parallel with respect to the RF signal and form an RF circuit through structural capacitors C2 and C3. Because the thermistors with a positive temperature coefficient absorb RF power, their resistance increases. In order to maintain the series resistance of the thermistors at 200Ω, the DC bias voltage of the DC self-balancing bridge will automatically decrease to maintain bridge balance. At this time, the DC bias voltage is V2.

[0068] Step 3: According to the law of conservation of energy, the power of the added radio frequency signal can be equivalent to the power of the reduced DC signal:

[0069]

[0070] In the formula, P rf It is the added radio frequency power, P sub This refers to the DC substitution power, which is the reduction in DC power after the bridge is rebalanced. V1 refers to the DC bias voltage of the bridge when no RF signal is initially applied, and V2 refers to the DC bias voltage of the bridge when it is rebalanced after an RF signal is applied. R dc It is the series resistance of thermistors R1 and R2, with a resistance of 200Ω.

[0071] The measured radio frequency voltage can be expressed as:

[0072]

[0073] In the formula, V rf It is the measured radio frequency voltage, R rf It is the parallel resistance of thermistors R1 and R2, with a resistance of 50Ω.

[0074] The radio frequency voltage on the measuring end face can be determined using the above method.

[0075] Table 1 shows the results of six radio frequency voltage measurements performed using the device described in this embodiment.

[0076] Table 1. Repeatability of six RF voltage measurements

[0077]

[0078] The calibration method for the radio frequency voltmeter under test is as follows:

[0079] A flat-to-coaxial N-type connector is connected to the lower electrode 3 of the RF voltage measuring device. The flat-type connector is placed in close contact with the thin-film thermistor, and the coaxial N-type connector is connected to the RF voltmeter being measured. At this time, the RF voltmeter being measured and the thin-film thermistor of the RF voltage measuring device are measuring the RF voltage on the same terminal face. The RF voltage measuring device can then be used to calibrate the RF voltmeter being measured.

[0080] The apparatus of this embodiment can solve the following problems:

[0081] 1. Solved the impedance matching problem when measuring radio frequency (RF) voltages. Since RF voltage frequencies typically reach 3 GHz or higher, RF voltmeters usually use a coaxial interface (50Ω impedance). Therefore, the RF voltage measuring device also needs to have a 50Ω impedance to ensure impedance matching. The RF voltage standard device employs a symmetrical dual-thermistor design, where two thermistors with similar resistance and sensitivity are respectively attached to the two halves of the middle electrode. The thermistors are connected to a DC self-balancing bridge via lead pins to achieve DC substitution. The advantage of this design is that when the thermistors are balanced to 200Ω by the DC self-balancing bridge, their parallel resistance relative to the RF signal is 50Ω, thus providing good impedance matching. This is suitable for measuring coaxial RF voltmeters and reduces mismatch errors when measuring RF voltages.

[0082] 2. Expanded Frequency Range for RF Voltage Measurement. The frequency range of RF voltage measurement is a key indicator of RF voltage measurement devices. Currently, the main RF voltage measurement devices on the market have a frequency range of 10MHz to 3GHz. This invention provides a structural capacitance of 5nF ​​to 50nF for the RF voltage measurement device by sandwiching two mica sheets between the upper, middle, and lower electrodes. Simultaneously, a slot is designed on the lower electrode to insert a surface-mount capacitor (100nF to 1uF), further expanding the structural capacitance of the RF voltage measurement device. This structural capacitance not only provides an RF circuit for the RF voltage standard device, preventing interference between the RF signal and the DC bias signal and further improving measurement accuracy, but also expands the lower frequency limit of voltage measurement. The lower frequency limit of the RF voltage measurement device can reach 10MHz or lower, and the upper frequency limit can reach 6GHz or higher.

[0083] 3. The thermistor method (DC substitution method) used is currently the most accurate radio frequency voltage measurement method, with a relative standard deviation of less than 0.09% for multiple measurements, demonstrating excellent measurement repeatability.

[0084] 4. The RF voltage measuring device made of brass has both good conductivity and high thermal resistance, allowing it to operate at room temperature and resist the influence of ambient temperature drift on the measurement results to a certain extent.

[0085] 5. The design of two lead electrode shaft pins, multiple fixing bolts and insulating sleeves can easily lead the thin film thermocouple on the middle electrode to the DC self-balancing bridge, while fixing the relative position between the electrodes, making the structure more stable and avoiding short circuits between the electrodes.

[0086] In summary, the device of this embodiment has the following advantages:

[0087] 1. It has good impedance matching and is suitable for coaxial N-type connectors.

[0088] 2. The measurement frequency range has been expanded, enabling the measurement of radio frequency voltages from 10MHz to 6GHz.

[0089] 3. The measurement repeatability is good, with the relative standard deviation of multiple repeated measurements being less than 0.09%.

[0090] 4. It has good temperature stability and can be measured at room temperature.

[0091] 5. It is simple to operate, has good robustness, and avoids problems such as short circuits.

[0092] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A radio frequency voltage measurement device based on thin-film thermistor, characterized in that, The device includes an upper electrode (1), a middle electrode (2), and a lower electrode (3) stacked sequentially. The middle electrode (2) consists of two metal halves with a gap between them. The upper electrode (1) is fixed with a coaxial connector (7), a center conductor (8), and lead electrode pins (9). The coaxial connector (7) and the center conductor (8) are used to feed radio frequency signals into the middle electrode (2). The side of the middle electrode (2) facing the lower electrode (3) is provided with two thermocouples, which are electrically connected to the two metal halves respectively. The two lead electrode pins (9) pass through the upper electrode (1) and are inserted into the two metal halves of the middle electrode (2), connecting the thin-film thermistor on the middle electrode (2) to an external DC self-balancing bridge. The lead electrode pins (9) are isolated from the upper electrode (1) by an insulating sleeve (10). The lower electrode (3) is connected to the device under test. A first mica sheet (4) and a second mica sheet (5) are inserted between the upper electrode (1), the middle electrode (2), and the lower electrode (3) respectively.

2. The radio frequency voltage measurement device based on thin-film thermistor according to claim 1, characterized in that, A groove is opened on the side of the lower electrode (3) facing the middle electrode (2), and a chip capacitor (11) is fixed in the groove.

3. The radio frequency voltage measurement device based on thin-film thermistor according to claim 1 or 2, characterized in that, The two thermocouples are a pair of identical thermistors deposited on a thin film, forming a thin-film thermocouple.

4. The radio frequency voltage measurement device based on thin-film thermistor according to claim 3, characterized in that, The lower electrode (3) and the second mica sheet (5) have a central hole, the planar size of which is equal to or slightly larger than the planar size of the thin-film thermocouple.

5. The radio frequency voltage measurement device based on thin-film thermocoupler according to claim 4, characterized in that, The center hole of the lower electrode (3) has an internal thread, and the flat connector to coaxial N-type connector is threaded to the center hole.

6. The radio frequency voltage measurement device based on thin-film thermistor according to claim 5, characterized in that, A pressure plate (12) is pressed into the center hole, and the pressure plate (12) is squeezed by the flat end of the flat connector to the coaxial N-type connector, thereby fixing the thin film thermocouple.

7. The radio frequency voltage measurement device based on thin-film thermocoupler according to claim 1 or 2, characterized in that, The upper electrode (1), the first mica sheet (4), the middle electrode (2), the second mica sheet (5), and the lower electrode (3) are fixed by bolts (6), and the bolts (6) are fitted with insulating sleeves (10).

8. A measurement method for a radio frequency voltage measurement device based on a thin-film thermistor, characterized in that, Includes the following steps: Step 1. Connect the two lead electrode pins (9) of the DC self-balancing bridge and the upper plate with connecting wires, and the thin film thermocouple is connected to the DC self-balancing bridge; When the DC self-balancing bridge is turned on, the thin-film thermistor is connected in series with respect to the DC signal. The thin-film thermistor is a positive temperature coefficient thermistor. When a DC signal is applied, the resistor heats up and the resistance increases until the series resistance is balanced at 200Ω by the DC self-balancing bridge. At this time, the DC bias voltage of the DC self-balancing bridge is V1. Step 2. Connect the radio frequency signal source to the coaxial connector (7) of the upper electrode (1) through a coaxial cable. When the radio frequency signal is applied, the two thermistors are connected in parallel relative to the radio frequency signal. The upper electrode (1), the middle electrode (2) and the mica sheet together form a 5nF~50nF structural capacitor C2 / the middle electrode (2), the lower electrode (3) and the mica sheet together form a 5nF~50nF structural capacitor C3 to form a radio frequency circuit. Since the thermistor absorbs the radio frequency power, the resistance increases. In order to maintain the series resistance of the thermistor at 200Ω, the DC bias voltage of the DC self-balancing bridge will automatically decrease to maintain the bridge balance. At this time, the DC bias voltage is V2. Step 3. According to the law of conservation of energy, the power of the added radio frequency signal is equivalent to the power of the reduced DC signal: In the formula, It is the added radio frequency power. It is the DC power substitution, that is, the DC power reduced after the bridge is rebalanced; It is the series resistance of thermistors R1 and R2; The measured radio frequency voltage can be expressed as: In the formula, The measured radio frequency voltage, It is the parallel resistance of thermistors R1 and R2; The radio frequency voltage on the measuring end face can be determined using the above method.

9. A calibration method for a radio frequency voltmeter under test in a radio frequency voltage measuring device based on a thin-film thermistor, characterized in that, Connect a flat-top to a coaxial N-type connector to the lower electrode (3). The flat-top end is in close contact with the thin-film thermocouple, and the coaxial N-type connector end is connected to the radio frequency voltage meter to be measured. At this time, the radio frequency voltage meter to be measured and the thin-film thermocouple of the radio frequency voltage measuring device measure the radio frequency voltage on the same end face; complete the calibration of the radio frequency voltage measuring device for the radio frequency voltage meter to be measured.

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