CN100397057C - Radio Frequency Temperature Sensor and Its Temperature Calibration Method - Google Patents

Abstract

The present invention relates to a radio frequency temperature sensor and a temperature calibration method thereof, which calibrates and verifies the performance of the radio frequency temperature sensor by a simple circuit of an active radio frequency temperature sensor including a ring oscillator, a memory, a frequency counter, a radio frequency transmission interface and a microcontroller. Afterwards, it is developed into a passive radio frequency temperature sensor including a rectifier (Regulator), a frequency generator (Clock Extractor), a ring oscillator, a memory, a frequency counter, a modulator (Modulator) and a state machine. The present invention calibrates and verifies the performance of the radio frequency temperature sensor by a simple circuit of an active radio frequency temperature sensor, and develops it into a passive radio frequency temperature sensor that can accurately measure temperature, thereby being more suitable for practical use.

Description

Radio Frequency Temperature Sensor and Its Temperature Calibration Method

technical field

The invention relates to a radio frequency measurement device, in particular to a radio frequency temperature sensor and a temperature correction method thereof (RADIO FREQUENCY TEMPERATURE SENSOR AND TEMPERATURECABLIBRATING METHOD THEREFOR).

Background technique

In daily applications, we often need to measure many parameters, such as temperature, humidity, pressure, etc., and there are many occasions where we are not allowed to directly measure the object to be measured with a measuring instrument (such as a racing tire pressure). Therefore, a radio frequency application circuit that can accurately measure the required value and obtain the result in a long distance is necessary. In this type of RF circuit design, we will add many measurement components to the application circuit to measure parameters such as temperature, humidity, pressure, etc., and then send the measured results using RF.

In these measurement devices of different categories, we often directly develop an RF IC, and then obtain and verify the functions we need by modifying its related application circuits. However, this method is quite time-consuming and wastes a lot of money, and it is often uncertain whether the transmission method and transmission performance used may meet the design requirements.

It can be seen that the above-mentioned existing radio frequency temperature sensor and its temperature correction method still have many defects, and further improvement is urgently needed. In order to solve the defects of the existing RF temperature sensor and its temperature calibration method, the relevant manufacturers have tried their best to find a solution, but no suitable design has been developed for a long time. This is obviously the relevant industry eager to solve The problem.

In view of the defects in the above-mentioned existing radio frequency temperature sensor and its temperature correction method, the inventor actively researches and innovates based on his rich practical experience and professional knowledge in the design and manufacture of such products, in order to create a new radio frequency sensor. The temperature sensor and its temperature correction method can improve the general existing radio frequency temperature sensor and its temperature correction method, making it more practical. Through continuous research, design, and after repeated trial samples and improvements, the present invention with practical value is finally created.

Contents of the invention

The purpose of the present invention is to overcome the defects of the existing radio frequency temperature sensor and its temperature correction method, and provide a new radio frequency temperature sensor and its temperature correction method. The technical problem to be solved is to make it available by A simple circuit of an active RF temperature sensor to calibrate and verify the performance of the RF temperature sensor, and develop a passive RF temperature sensor that can accurately measure temperature, which is more suitable for practical use and has industrial significance use value.

The purpose of the present invention and the solution to its technical problems are achieved by adopting the following technical solutions. A radio frequency temperature sensor proposed according to the present invention includes: a ring oscillator used to generate an oscillating signal whose frequency changes with a measured temperature change; a memory used to store a frequency count start The frequency counting initial value corresponds to a preset temperature; a frequency counter, coupled to the memory and the ring oscillator, is used for a preset time range according to the frequency counting initial value and the oscillation signal, A temperature deviation value corresponding to the measured temperature and the preset temperature is counted by the frequency counter; a radio frequency transmission interface is used as a transmission interface with a card reader; and a microcontroller is coupled to the frequency counter , the memory and the radio frequency transmission interface are used to load the frequency count start value into the frequency counter, control the start and end of the preset time range, and read the temperature deviation value, and through the radio frequency transmission interface to Communicate with the card reader.

The purpose of the present invention and its technical problems can also be further realized by adopting the following technical measures.

The aforementioned radio frequency temperature sensor, wherein the ring oscillator includes: a thermistor with a first end and a second end; a capacitor with a first end and a second end, the first end coupled to the second end of the thermistor, the second end is grounded; a Schmitt inverter has an input end and an output end, the input end is coupled to the second end of the thermistor; An inverter has an input terminal and an output terminal, the input terminal is coupled to the output terminal of the Schmitt inverter; and a NAND gate has a first input terminal, a second input terminal and An output terminal, the first input terminal is used to receive an enabling signal, the output terminal is coupled to the first terminal of the thermistor, the second input terminal is coupled to the output terminal of the inverter, and is used to output The oscillating signal.

In the aforementioned radio frequency temperature sensor, the memory is a non-volatile memory.

In the aforementioned radio frequency temperature sensor, the frequency counter is a down counter.

The aforementioned radio frequency temperature sensor, wherein the radio frequency transmission interface includes: an antenna, composed of an inductor and a capacitor connected in parallel; a diode, the anode of the diode is coupled to one end of the antenna; and a zener diode, the The anode terminal of the Zener diode is coupled to the other end of the antenna, and the cathode terminal is coupled to the cathode terminal of the diode.

In the aforementioned radio frequency temperature sensor, the microcontroller converts the temperature deviation value into the measured temperature according to a temperature correspondence table.

The aforementioned radio frequency temperature sensor uses a general-purpose I/O port of the microcontroller to communicate with the card reader.

The purpose of the present invention and the solution to its technical problems are also achieved by the following technical solutions. A temperature correction method proposed according to the present invention is applicable to a radio frequency temperature sensor comprising at least a ring oscillator, a memory and a frequency counter. The method includes the following steps: using the ring oscillator to generate a standard value Measuring an oscillating signal related to temperature; measuring a frequency count value of the frequency counter in a preset time range according to the oscillating signal; and storing the frequency count value in the memory as a function of the frequency counter Frequency count start value.

The purpose of the present invention and the solution to its technical problems are also achieved by the following technical solutions. A radio frequency temperature sensor proposed according to the present invention includes: a rectifier, used to obtain the current oscillating from an antenna, and convert it into a voltage required for the operation of the radio frequency temperature sensor; The antenna obtains the clock pulse required by the radio frequency temperature sensor; a ring oscillator is used to generate an oscillation signal whose frequency changes with a measurement temperature change; a memory is used to store a frequency count initial value , the frequency counting initial value corresponds to a preset temperature; a frequency counter, coupled to the memory and the ring oscillator, is used for a preset time range according to the frequency counting initial value and the oscillation signal, A temperature deviation value corresponding to the measured temperature and the preset temperature is counted by the frequency counter; a modulator is used as a transmission interface with a card reader; and a state device is coupled to the frequency counter, The memory and the modulator are used to load the starting value of the frequency count to the frequency counter, control the start and end of the preset time range and read the temperature deviation value, and communicate with the modulator through the modulator The reader communicates.

The purpose of the present invention and its technical problems can also be further realized by adopting the following technical measures.

The aforementioned radio frequency temperature sensor, wherein the ring oscillator includes: a thermistor with a first end and a second end; a capacitor with a first end and a second end, the first end coupled to the second end of the thermistor, the second end is grounded; a Schmitt inverter has an input end and an output end, the input end is coupled to the second end of the thermistor; An inverter has an input terminal and an output terminal, the input terminal is coupled to the output terminal of the Schmitt inverter; and a NAND gate has a first input terminal, a second input terminal and An output terminal, the first input terminal is used to receive an enabling signal, the output terminal is coupled to the first terminal of the thermistor, the second input terminal is coupled to the output terminal of the inverter, and is used to output The oscillating signal.

In the aforementioned radio frequency temperature sensor, the memory is a non-volatile memory.

In the aforementioned radio frequency temperature sensor, the frequency counter is a down counter.

Compared with the prior art, the present invention has obvious advantages and beneficial effects. As can be seen from the above technical solutions, in order to achieve the aforementioned object of the invention, the main technical contents of the present invention are as follows:

The invention provides a radio frequency temperature sensor. The radio frequency temperature sensor includes: a ring oscillator, a memory, a frequency counter, a radio frequency transmission interface and a microcontroller. Wherein, the ring oscillator is used to generate an oscillating signal whose frequency changes with the change of the measured temperature. The memory is used to store the initial value of the frequency count used by the frequency counter. The frequency counter is coupled to the memory and the ring oscillator, and is used to count in a preset time range corresponding to the measured temperature according to the initial value of the frequency count and the oscillation signal. temperature deviation value. The radio frequency transmission interface is used as the transmission interface with the card reader, and the microcontroller is coupled to the frequency counter, memory and radio frequency transmission interface to load the frequency counter with the initial value of the frequency count and control the start of the preset time range. Start and end and read the temperature deviation value, and communicate with the card reader through the radio frequency transmission interface.

In one embodiment, the ring oscillator of the radio frequency temperature sensor includes: a thermistor, a capacitor, a Schmitt inverter, an inverter, and a NAND gate. Wherein, the thermistor and the capacitor each have a first end and a second end, the first end of the capacitor is coupled to the second end of the thermistor, and the second end of the capacitor is grounded. The Schmitt inverter has an input terminal and an output terminal, and the input terminal is coupled to the second terminal of the thermistor. The inverter has an input end and an output end, and the input end is coupled to the output end of the Schmitt inverter. The NAND gate has a first input terminal, a second input terminal and an output terminal, the first input terminal is used to receive an enable signal, the output terminal is coupled to the first terminal of the thermistor, and the second input terminal is coupled to the inverter The output terminal is used to output the above-mentioned oscillating signal.

In one embodiment, the memory of the radio frequency temperature sensor is a non-volatile memory.

In one embodiment, the frequency counter of the radio frequency temperature sensor is a down counter.

In one embodiment, the radio frequency transmission interface of the radio frequency temperature sensor includes: an antenna composed of an inductor and a capacitor connected in parallel, a diode whose anode end is coupled to one end of the antenna, and an anode end of which is coupled to the other end of the antenna, The cathode terminal of the Zener diode is coupled to the cathode terminal of the diode.

In one embodiment, the microcontroller of the radio frequency temperature sensor converts the temperature deviation value measured by the frequency counter into the measured temperature according to a temperature correspondence table.

In one embodiment, the RF temperature sensor uses a general-purpose I/O port of the microcontroller to communicate with the card reader.

The invention also provides a temperature correction method, which is applicable to a radio frequency temperature sensor including at least a ring oscillator, a memory and a frequency counter. The temperature correction method includes the following steps: using a ring oscillator to generate an oscillating signal related to a standard measurement temperature such as 40° C.; measuring the frequency count value of the frequency counter in a preset time range according to the oscillating signal; and The frequency counting value is stored in the memory as the starting value of the frequency counting of the frequency counter.

The present invention also provides a radio frequency temperature sensor, the radio frequency temperature sensor includes: a rectifier (Regulator), a frequency generator (ClockExtractor), a ring oscillator, a memory, a frequency counter, a modulator (Modulator) and a state device (State machine). Among them, the rectifier is used to obtain the current oscillating by the antenna, and convert it into the voltage required for the operation of the radio frequency temperature sensor. The frequency generator is used to obtain the clock pulse required for the operation of the RF temperature sensor from the antenna, the ring oscillator is used to generate an oscillating signal whose frequency changes with the change of the measured temperature, and the memory is used to store the frequency counting start used by the frequency counter The frequency counter is coupled to the memory and the ring oscillator, and is used to count a temperature deviation value corresponding to the measured temperature in a preset time range according to the initial value of the frequency count and the oscillation signal. The modulator is used as the transmission interface with the card reader, and the state device is coupled to the frequency counter, memory and modulator to load the frequency counter with the initial value of the frequency count and control the start and end of the preset time range. Finish and read the temperature deviation value, and communicate with the card reader through the modulator.

In one embodiment, the ring oscillator of the radio frequency temperature sensor includes: a thermistor, a capacitor, a Schmitt inverter, an inverter, and a NAND gate. Wherein, the thermistor and the capacitor each have a first end and a second end, the first end of the capacitor is coupled to the second end of the thermistor, and the second end of the capacitor is grounded. The Schmitt inverter has an input terminal and an output terminal, and the input terminal is coupled to the second terminal of the thermistor. The inverter has an input end and an output end, and the input end is coupled to the output end of the Schmitt inverter. The NAND gate has a first input terminal, a second input terminal and an output terminal, the first input terminal is used to receive an enable signal, the output terminal is coupled to the first terminal of the thermistor, and the second input terminal is coupled to the inverter The output terminal is used to output the above-mentioned oscillating signal.

In one embodiment, the memory of the radio frequency temperature sensor is a non-volatile memory.

In one embodiment, the frequency counter of the radio frequency temperature sensor is a down counter.

It can be seen from the above that the present invention is a radio frequency temperature sensor and its temperature correction method, which is a simple method of an active radio frequency temperature sensor including a ring oscillator, a memory, a frequency counter, a radio frequency transmission interface and a microcontroller. Circuits to calibrate and verify the performance of RF temperature sensors. After that, it was developed into a passive RF temperature sensor including a rectifier (Regulator), a frequency generator (ClockExtractor), a ring oscillator, a memory, a frequency counter, a modulator (Modulator) and a state device.

By means of the above technical solution, the present invention can calibrate and verify the performance of the RF temperature sensor through a simple circuit of an active RF temperature sensor, and develop a passive RF temperature sensor capable of accurately measuring temperature. Therefore, it is more suitable for practical use and has industrial utilization value.

In summary, the special radio frequency temperature sensor and its temperature correction method of the present invention have the above-mentioned many advantages and practical value, and there is no similar structural design and method publicly published or used in similar products and methods, and it is indeed a Innovation, which has a great improvement in product structure, method or function, and has made great progress in technology, and has produced easy-to-use and practical effects, and is better than the existing RF temperature sensor and its temperature sensor. The correction method has multiple enhanced effects, so it is more suitable for practical use, and has wide application value in the industry. It is a novel, progressive and practical new design.

The above description is only an overview of the technical solutions of the present invention. In order to understand the technical means of the present invention more clearly and implement them according to the contents of the description, the preferred embodiments of the present invention and accompanying drawings are described in detail below.

Description of drawings

FIG. 1 is a schematic block diagram of an active radio frequency temperature sensor according to a preferred embodiment of the present invention.

Fig. 2 is a circuit diagram of a ring oscillator according to a preferred embodiment of the present invention.

FIG. 3 is an operation waveform diagram of the radio frequency transmission interface when the card reader reads data according to a preferred embodiment of the present invention.

FIG. 4 is an operation waveform diagram of the radio frequency transmission interface when the card reader writes data according to a preferred embodiment of the present invention.

FIG. 5 is a schematic block diagram of a passive radio frequency temperature sensor according to a preferred embodiment of the present invention.

100, 500: RF temperature sensor 110, 510: Ring oscillator

120, 520: memory (memory) 130, 530: frequency counter

140: RF transmission interface (interface) 141: Inductance

142, 220 capacitors 143: Diode

144: Zener Diode 150: Microcontroller

200: card reader 210: thermistor

230: Schmidt Inverter 240: Inverter

250: NAND gate (NAND gate) 540: Modulator

550: state device 560: rectifier

570: Frequency Generator 580: Antenna

Detailed ways

The specific structure, method, steps, features and effects of the radio frequency temperature sensor and its temperature correction method according to the present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments.

Please refer to FIG. 1 , which is a schematic block diagram of an active radio frequency temperature sensor according to a preferred embodiment of the present invention. The radio frequency temperature sensor 100 of the preferred embodiment of the present invention is a ring oscillator 110, such as a non-volatile memory memory 120 and a frequency counter 130 to complete the temperature measurement function, and its measurement principle will now be described as follows.

Firstly, the ring oscillator 110 is used to generate an oscillating signal Clock_In whose frequency changes with the change of the measured temperature, as the counting clock of the frequency counter 130 . The ring oscillator 110 may be an oscillator including a thermistor 210 , a capacitor 220 , a Schmitt inverter 230 , an inverter 240 and a NAND gate 250 as shown in FIG. 2 .

Please refer to FIG. 2 , the thermistor 210 and the capacitor 220 each have a first end and a second end, the first end of the capacitor 220 is coupled to the second end of the thermistor 210 , and the second end of the capacitor 220 is grounded. The Schmitt inverter 230 has an input terminal and an output terminal, and the input terminal is coupled to the second terminal of the thermistor 210 . The inverter 240 has an input terminal and an output terminal, and the input terminal is coupled to the output terminal of the Schmitt inverter 230 . The NAND gate 250 has a first input end, a second input end and an output end, the first input end of which is used to receive an enable signal En, and the output end is coupled to the first end of the thermistor 250 to form a circular loop , the second input end of which is coupled to the output end of the inverter 240 and used to output the oscillation signal Clock_In whose frequency changes with the change of the measured temperature. Wherein, the frequency of the oscillating signal Clock_In changes because the resistance of the thermistor 250 changes with temperature, resulting in different RC delay times of the circuit.

Please refer to FIG. 1 again. The commercially available thermistor used in the ring oscillator 110 can generally guarantee that the error range of its temperature change constant B (B-constant) is within 1%, but its absolute value error But there will be about 5%. In addition, commercially available capacitors used in the ring oscillator 110 generally have a 5% error range. Therefore, a 5% thermistor error plus a 5% capacitance error in the ring oscillator 110 will result in a 10% error. If no proper temperature correction method is used, the error of the measured temperature value will be too large . Therefore, the memory 120 in the figure is used to store the initial frequency counting value used by the frequency counter 130 to correct errors of the thermistor and capacitor in the ring oscillator 110 .

When calibrating, the ring oscillator 110 is firstly used to generate an oscillating signal Clock_In related to a standard measurement temperature such as 40°C, and then according to the oscillating signal Clock_In, the frequency count value of the frequency counter 130 in a preset time range is measured , for example 2800. Finally, the frequency count value of 2800 is stored in the memory 120 as the initial frequency count value of the frequency counter 130 . Therefore, in this embodiment, the preset temperature corresponding to the above frequency count initial value is 40° C. .

Therefore, when the temperature is actually measured, the frequency count value stored in the memory 120 can be loaded into the frequency counter 130, and the frequency counter 130, such as a countdown counter, can be used for example to start from 2800 within the aforementioned preset time range. The counting value is decremented from the starting value of the frequency counting, and the temperature deviation value centered on 40°C is obtained. That is to say, when the measured temperature is 40°C, the count value of the frequency counter 130 will be 0; The count value of 130 will be lower than the temperature deviation value of 0; and when the measured temperature is higher than 40°C, because the frequency of the oscillation signal Clock_In of the ring oscillator 110 is low, the count value of the frequency counter 130 will be higher than 0 temperature deviation value. The temperature deviation value can be converted into a measured temperature according to a temperature correspondence table stored in the memory 120 or the card reader 200 . Of course, if the temperature range to be measured is large, in order to make the measurement result more accurate, you can also sample several more frequency counting start values. For example, if the range you want to measure is 0-70°C, you can Measure one value at ℃, measure one value at 35°C, and measure another value at 70°C, for reference when measuring temperature deviation.

As mentioned above, in order to calibrate and verify the performance of the RF temperature sensor through a simple active RF temperature sensor circuit, the present embodiment uses the RF transmission interface 140 and the microcontroller 150 in the figure to use Complete the functions of loading the initial frequency counting value into the frequency counter 130 , controlling the start and end of the preset time range, reading the temperature deviation value, and communicating 200 with the card reader through the radio frequency transmission interface 140 . Certainly, since the circuit of the radio frequency temperature sensor 100 in the figure is used for verification function, its working power is provided by an external power source (not shown) such as a battery. In addition, the microcontroller 150 is generally a microcontroller with a GPIO port, so as to communicate with the card reader 200 through the GPIO port of the microcontroller 150 . Now its communication principle is explained as follows.

In FIG. 1 , its radio frequency transmission interface 140 includes: an antenna composed of an inductor 141 and a capacitor 142 in parallel, a diode 143 whose anode end is coupled to one end of the antenna, and its anode end is coupled to the other end of the antenna, and the cathode end is coupled to the other end of the antenna. Zener diode 144 is coupled to the cathode terminal of diode 143 at its extreme end.

Wherein, the values of the inductor 141 and the capacitor 142 should be set so that the resonance frequency (Resonance frequency) is the same as the carrier frequency (Carrier frequency). When resonance occurs, the other end of the antenna will generate a sinusoid AC signal. Because the sine wave is sometimes a positive voltage and sometimes a negative voltage, if this end of the antenna is directly connected to the general-purpose output port GPIO of the microcontroller 150, then when the antenna end is a negative voltage, it will be output from the general-purpose output port of the microcontroller 150. The incoming GPIO draws the current, causing a latch-up effect in the circuit. Therefore, the diode 143 must be used to filter out the negative voltage before being connected to the GPIO of the microcontroller 150 .

In addition, when the distance between the antenna and the card reader 200 is closer, the voltage induced by the antenna will be larger. At this time, if the induced voltage is not limited, when the antenna is close to a certain distance, the induced voltage will easily exceed the breakdown voltage (Breakdown voltage) of the internal transistor components of the microcontroller 150, resulting in damage or failure of the components. unusual. Therefore, Zener diodes must be used to clamp the maximum voltage to prevent damage to components.

Please refer to FIG. 3 , which is an operation waveform diagram of the radio frequency transmission interface when the card reader reads data according to a preferred embodiment of the present invention. Generally speaking, by changing the register value of the microcontroller 150, the general-purpose input and output port GPIO of the microcontroller 150 can be easily set to floating (floating), input mode pull-down resistor (pull low resistor) and There are 3 kinds of state changes such as the output low potential (outputlow) of the output mode. Among these three state changes, the equivalent resistance value seen by the radio frequency transmission interface 140 is the highest, followed by the pull-down resistance in the input mode, and then the output low potential in the output mode. Therefore, the change of different resistance values can be used to change the amplitude of the carrier wave sent by the card reader 200 to achieve the purpose of transmitting data to the card reader 200 .

In Fig. 1, when the card reader 200 sends out the carrier wave and the RF temperature sensor 100 is close to the card reader 200, the antenna of the RF transmission interface 140 starts to sense energy and resonates. See sine waves. Assuming that the signal to be transmitted by the RF temperature sensor 100 is 101001, the microcontroller 150 can sequentially set the GPIO as floating connection, pull-down resistor, floating connection, pull-down resistor, pull-down resistor, floating connection, etc. Therefore, the waveforms of the antenna end of the radio frequency transmission interface 140, the GPIO end of the microcontroller 150 and its logic level will be shown in (a), (b), and (c) in FIG. 3 respectively. Therefore, The data can be successfully transmitted to the card reader 200 . Of course, although the above-mentioned operations are performed with floating connection and pull-down resistor, as known to those skilled in the art, it is feasible to choose any of the three states of floating connection, pull-down resistor and output low potential.

Please refer to FIG. 4 , which is an operation waveform diagram of the radio frequency transmission interface when the card reader writes data according to a preferred embodiment of the present invention. When the card reader 200 writes, it is necessary to first set the GPIO of the microcontroller 150 as a pull-down resistor in the input mode, and then the card reader 200 sends out a waveform as shown in FIG. 4( a ). That is to say, sometimes there is a sine wave amplitude, and sometimes there is no sine wave amplitude to represent the transmitted logic levels 1 and 0 respectively. At this time, the antenna of the RF temperature sensor 100 senses the transmitted waveform, and is filtered by the diode 143 to generate a waveform as shown in FIG. 4( b ). Assuming that the parasitic capacitance of the GPIO port of the microcontroller 150 is large enough, the waveform of the GPIO port of the microcontroller 150 will be as shown in FIG. When the parasitic capacitance of the GPIO port is not large enough, a capacitor can also be added to the GPIO port of the microcontroller 150, so that the waveform of the GPIO port of the microcontroller 150 can be as shown in FIG. 4(c). Therefore, as long as the microcontroller 150 regularly samples the voltage of the GPIO terminal of its general-purpose input and output port, it can restore the logic signal transmitted by the card reader 200 as shown in Figure 4(d), so the data can be successfully written into the radio frequency. The purpose of the temperature sensor 100 .

The above description is the design of an active RF temperature sensor used to verify the function. The reason why it is called active is because it is powered by an external power source such as a battery. After the functional verification is completed, the circuit must be converted into a passive RF IC, that is, an RF IC without external power supply, and its circuit will be shown in Figure 5.

5, the radio frequency temperature sensor 500 includes: a rectifier (Regulator) 560, a frequency generator (Clock Extractor) 570, a ring oscillator 510, a memory 520, a frequency counter 530, and a modulator (Modulator) 540 And a state machine (State machine) 550. Wherein, since there is no external power supply, the rectifier 560 must be used to obtain the oscillating current of the antenna 580 and convert it into the voltage required for the RF temperature sensor 500 to work. In addition, the frequency generator 570 must be used to obtain the clock pulse required for the operation of the radio frequency temperature sensor 500 from the antenna 580, the modulator 540 is used as the transmission interface with the card reader 200, and the state device 550 is used to store in The initial value of the frequency count in the memory 520 is loaded into the frequency counter 530, the start and end of the preset time range for control counting and the temperature deviation value are read, and the modulator 540 communicates with the card reader 200 to replace Functions of microcontroller 150 in FIG. 1 . Of course, the functions of the ring oscillator 510 , the memory 520 and the frequency counter 530 in the figure are the same as those in FIG. 1 , so the details will not be repeated here.

The above description is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. Anyone familiar with this field Those skilled in the art, without departing from the scope of the technical solution of the present invention, may use the method and technical content disclosed above to make some changes or modifications to equivalent embodiments with equivalent changes, but if they do not depart from the technical solution of the present invention, Any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention still fall within the scope of the technical solutions of the present invention.

Claims (12)

1. A radio frequency temperature sensor, characterized in that it comprises: a ring oscillator for generating an oscillating signal whose frequency varies with a measured temperature change; a memory for storing a frequency count initial value corresponding to a preset temperature; A frequency counter, coupled to the memory and the ring oscillator, is used to count the initial value of the frequency and the oscillation signal, within a preset time range, the frequency counter counts corresponding to the measured temperature and the preset A temperature deviation value of the set temperature; a radio frequency transmission interface used as a transmission interface with a card reader; and A microcontroller, coupled to the frequency counter, the memory, and the radio frequency transmission interface, is used to load the frequency count initial value into the frequency counter, control the start and end of the preset time range, and read the temperature deviation value, and communicate with the card reader through the radio frequency transmission interface. 2. The radio frequency temperature sensor according to claim 1, wherein said ring oscillator comprises: A thermistor has a first terminal and a second terminal; A capacitor has a first end and a second end, the first end is coupled to the second end of the thermistor, and the second end is grounded; a Schmitt inverter, having an input terminal and an output terminal, the input terminal is coupled to the second terminal of the thermistor; An inverter has an input terminal and an output terminal, the input terminal is coupled to the output terminal of the Schmitt inverter; and A NAND gate has a first input terminal, a second input terminal and an output terminal, the first input terminal is used to receive an enabling signal, the output terminal is coupled to the first terminal of the thermistor, the The second input terminal is coupled to the output terminal of the inverter and used for outputting the oscillating signal. 3. The radio frequency temperature sensor according to claim 1, wherein the memory is a non-volatile memory. 4. The radio frequency temperature sensor according to claim 1, wherein said frequency counter is a down counter. 5. The radio frequency temperature sensor according to claim 1, wherein said radio frequency transmission interface comprises: An antenna composed of an inductor and a capacitor connected in parallel; a diode, the anode of which is coupled to one end of the antenna; and A Zener diode, the anode of the Zener diode is coupled to the other end of the antenna, and the cathode is coupled to the cathode of the diode. 6. The radio frequency temperature sensor according to claim 1, wherein said microcontroller converts the temperature deviation value into the measured temperature according to a temperature correspondence table. 7. The radio frequency temperature sensor according to claim 1, wherein a general-purpose I/O port of the microcontroller is used to communicate with the card reader. 8. A temperature calibration method, applicable to a radio frequency temperature sensor comprising at least a ring oscillator, a memory and a frequency counter, characterized in that the method comprises the following steps: using the ring oscillator to generate an oscillating signal related to a standard measurement temperature; measuring a frequency count value of the frequency counter within a preset time range according to the oscillating signal; and The frequency count value is stored in the memory as a frequency count initial value of the frequency counter. 9. A radio frequency temperature sensor, characterized in that it comprises: A rectifier is used to obtain the current oscillating from an antenna and convert it to the voltage required for the operation of the radio frequency temperature sensor; a frequency generator, used to obtain the clock pulse required for the operation of the radio frequency temperature sensor from the antenna; a ring oscillator for generating an oscillating signal whose frequency varies with a measured temperature change; a memory for storing a frequency count initial value corresponding to a preset temperature; A frequency counter, coupled to the memory and the ring oscillator, is used to count the initial value of the frequency and the oscillation signal, within a preset time range, the frequency counter counts corresponding to the measured temperature and the preset A temperature deviation value of the set temperature; a modulator used as a transmission interface with a card reader; and A state device, coupled to the frequency counter, the memory and the modulator, is used to load the frequency count initial value into the frequency counter, control the start and end of the preset time range and read the temperature deviation value, and communicate with the card reader via the modulator. 10. The radio frequency temperature sensor according to claim 9, wherein said ring oscillator comprises: A thermistor has a first terminal and a second terminal; A capacitor has a first end and a second end, the first end is coupled to the second end of the thermistor, and the second end is grounded; a Schmitt inverter, having an input terminal and an output terminal, the input terminal is coupled to the second terminal of the thermistor; An inverter has an input terminal and an output terminal, the input terminal is coupled to the output terminal of the Schmitt inverter; and A NAND gate has a first input terminal, a second input terminal and an output terminal, the first input terminal is used to receive an enabling signal, the output terminal is coupled to the first terminal of the thermistor, the The second input terminal is coupled to the output terminal of the inverter and used for outputting the oscillating signal. 11. The radio frequency temperature sensor according to claim 9, wherein said memory is a non-volatile memory. 12. The radio frequency temperature sensor according to claim 9, wherein said frequency counter is a down counter.

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