Dual frequency tag device and system

Abstract

The embodiment of the application provides a dual-frequency label device and system. The device comprises an antenna, a passive mixing unit, a frequency selection unit one and a frequency selection unit two. Port one of the passive mixing unit is electrically connected with the antenna, port two of the passive mixing unit is electrically connected with the frequency selection unit one, and port three of the passive mixing unit is electrically connected with the frequency selection unit two. The working frequencies of the frequency selection unit one and the frequency selection unit two are different. The frequency selection unit one and the frequency selection unit two can perceive target parameter changes, the signs of target parameter perception coefficients of the two are opposite, and the perception abilities of the frequency selection unit one and the frequency selection unit two to non-target parameters are the same or similar.

Description

Technical Field

[0001] This application relates to the field of communication technology, and more specifically, to a dual-frequency tag device and system. Background Technology

[0002] A tag, or electronic tag, is an electronic identifier attached to an object for automatic identification, tracking, and acquisition of information about that object. Tags can be functionally categorized into identification tags and sensing tags. They typically begin operating after receiving downlink radio frequency signals, while the resulting uplink radio frequency signals often operate at a single carrier frequency. Their performance is easily affected by the surrounding environment, such as strong background electromagnetic reflection and multipath effects. Summary of the Invention

[0003] To overcome the shortcomings of existing technologies, a dual-frequency tag device and system are provided in order to solve the technical problems existing in the prior art.

[0004] To achieve the aforementioned objectives, this application adopts the following technical solution:

[0005] In a first aspect, a dual-frequency tag device is provided, comprising: an antenna, a passive mixer unit, a first frequency selection unit, and a second frequency selection unit; a first port of the passive mixer unit is electrically connected to the antenna, a second port of the passive mixer unit is electrically connected to the first frequency selection unit, and a third port of the passive mixer unit is electrically connected to the second frequency selection unit; the first and second frequency selection units operate at different frequencies; the first and second frequency selection units are configured as follows:

[0006] Configuration 1: Both frequency selection unit 1 and frequency selection unit 2 can sense changes in target parameters, and the signs of their target parameter sensing coefficients are opposite. The sensing capabilities of frequency selection unit 1 and frequency selection unit 2 for non-target parameters are the same or similar.

[0007] Configuration 2: Frequency selection unit 1 is insensitive to changes in the target parameter, while frequency selection unit 2 can sense changes in the target parameter. The sensing capabilities of frequency selection unit 1 and frequency selection unit 2 for non-target parameters are the same or similar.

[0008] Furthermore, port one of the passive mixer unit is electrically connected to the antenna, port two of the passive mixer unit is electrically connected to frequency selection unit one, and port three of the passive mixer unit is electrically connected to frequency selection unit two. The passive mixer unit is configured to generate a broadband radio frequency signal based on the downlink radio frequency signal, passively mix the frequency selection signal one obtained by frequency selection unit one with the downlink radio frequency signal to obtain uplink radio frequency signal one, and passively mix the frequency selection signal two obtained by frequency selection unit two with the downlink radio frequency signal to obtain uplink radio frequency signal two. The frequency range of the broadband radio frequency signal covers the carrier frequency from DC to the downlink radio frequency signal. The carrier frequencies of the downlink radio frequency signal, uplink radio frequency signal one, and uplink radio frequency signal two are different from each other.

[0009] Furthermore, the passive mixer unit includes transistors.

[0010] Furthermore, the aforementioned transistor is a high electron mobility or two-dimensional electron gas field effect transistor, and one of the three ports of the aforementioned passive mixer unit is any one of the gate, drain, or source.

[0011] Furthermore, the aforementioned transistor is a bipolar transistor, and one of the three ports of the aforementioned passive mixer unit is any one of the base, collector, or emitter.

[0012] Furthermore, both frequency selection unit one and frequency selection unit two are single-port surface acoustic wave resonators.

[0013] Furthermore, frequency selection unit one includes LC resonant unit one and reference element, and frequency selection unit two includes LC resonant unit two and sensing element. The operating center frequencies of LC resonant unit one and LC resonant unit two are different. The target parameter sensing coefficients of the reference element and the sensing element have opposite signs, while the non-target parameters are the same or similar.

[0014] Furthermore, the aforementioned target parameter is one of temperature, strain, pressure, humidity, vibration, displacement, or tilt angle.

[0015] Secondly, a dual-frequency tag system is provided, including: a read / write device and the aforementioned dual-frequency tag device, wherein the read / write device sends downlink messages and receives uplink messages; wherein the downlink message includes a downlink radio frequency signal, and the uplink message includes an uplink radio frequency signal one and an uplink radio frequency signal two.

[0016] Furthermore, the aforementioned read / write device obtains a nominal sensing quantity one based on the aforementioned uplink radio frequency signal one, obtains a nominal sensing quantity two based on the aforementioned uplink radio frequency signal two, and obtains a differential sensing quantity based on the nominal sensing quantity one and the nominal sensing quantity two.

[0017] It is understood that, according to the technical solution of this application, a differential signal is obtained by using the dual-frequency uplink radio frequency signal generated by the tag, thereby solving the problems of poor demodulation accuracy and limited application scenarios caused by the inability to eliminate various interferences in a single uplink radio frequency signal. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the dual-frequency tag system structure according to an embodiment of this application;

[0019] Figure 2 This is one of the structural schematic diagrams of a dual-frequency tag device according to an embodiment of this application;

[0020] Figure 3 This is the second schematic diagram of the dual-frequency tag device according to an embodiment of this application. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0022] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0023] In this article, the term "and / or" is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone.

[0024] The terms "first," "second," "object one," "object two," etc., used in the specification and drawings of this application are used to distinguish different objects or to distinguish different treatments of the same object, rather than to describe a specific order of objects.

[0025] Furthermore, the terms "comprising" and "having," and any variations thereof, used in the description of this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the steps or units listed, but may optionally include other steps or units not listed, or may optionally include other steps or units inherent to such process, method, product, or apparatus.

[0026] It should be noted that in the embodiments of this application, the words "in an example," "exemplary," or "for example" are used to indicate that they are examples, illustrations, or explanations. Any embodiment or design that is described as "in an example," "exemplary," or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design options. Specifically, the use of the words "in an example," "exemplary," or "for example" is intended to present the relevant concepts in a specific manner.

[0027] It should be noted that, to save space, a single drawing in this application does not necessarily represent only a single embodiment or implementation method. Generally, a single drawing may be used to illustrate several embodiments or implementation methods. Functional components, connection relationships between components, or process steps that are not essential for certain embodiments will be indicated by dashed lines.

[0028] To facilitate understanding, the relevant technologies and concepts involved in the embodiments of this application will be introduced first.

[0029] Read / write device: also known as a reader, reading device, reader-writer, read / write apparatus, readout device, gateway, base station, transceiver, communicator, reader, etc. It is typically used for wirelessly reading (and sometimes writing) messages from a terminal. A reader can be a mobile or fixed device.

[0030] Downlink: In the context of communication between a reader and a terminal, this refers to the direction of signal flow from the reader to the terminal.

[0031] Uplink: In the context of communication between a reader and a terminal, it refers to the direction of signal flow from the terminal to the reader.

[0032] A tag, or electronic tag, is an electronic identifier attached to an object for the purpose of automatically identifying, tracking, and obtaining information about that object.

[0033] In existing technologies, tags (especially sensor tags) typically begin operating after receiving downlink RF signals. The resulting uplink RF signals often operate at a single carrier frequency, making their performance susceptible to environmental influences such as strong background electromagnetic reflection and multipath effects. This results in poor demodulation accuracy and limited application scenarios. To address these issues, this application provides a dual-frequency tag device and system that utilizes the dual-frequency uplink RF signals generated by the tag to obtain differential signals, thereby overcoming the aforementioned problems of single-frequency tag devices or systems.

[0034] Please see Figure 1 , Figure 1 This is a schematic diagram of a dual-frequency tag system provided in an embodiment of this application. The system is applied in the field of communication technology. The dual-frequency tag system includes a dual-frequency tag device and a reader / writer device, wherein:

[0035] The read / write device is configured to send downlink messages and receive uplink messages.

[0036] Specifically, the downlink message includes a downlink radio frequency signal, and the carrier frequency of the downlink radio frequency signal is f0.

[0037] It should be understood that the read / write device in the embodiments of this application is a device equipped with a processor that can execute computer execution instructions. It can be a reader / writer device or a network device that integrates reader / writer functionality. The network device can also be an access network device or a wireless access network device, such as a base station. The base station or reader / writer device can be fixed or mobile. For example, a helicopter or drone can be configured to act as a mobile base station.

[0038] The dual-frequency tag device is configured to receive downlink messages and send uplink messages.

[0039] In one implementation, the uplink message is generated based on the downlink message.

[0040] Specifically, the uplink message includes two uplink radio frequency signals, which are generated based on the downlink radio frequency signals.

[0041] Please see Figure 1 The dual-frequency tag device includes an antenna, a passive mixer unit, a frequency selection unit one, and a frequency selection unit two. Port one of the passive mixer unit is electrically connected to the antenna, port two of the passive mixer unit is electrically connected to the frequency selection unit one, and port three of the passive mixer unit is electrically connected to the frequency selection unit two.

[0042] The passive mixer unit is configured to generate a wideband radio frequency signal based on the downlink radio frequency signal, passively mix the frequency-selected signal obtained by the frequency selection unit one with the downlink radio frequency signal to obtain the uplink radio frequency signal one, and passively mix the frequency-selected signal obtained by the frequency selection unit two with the downlink radio frequency signal to obtain the uplink radio frequency signal two; wherein the carrier frequencies of the downlink radio frequency signal, the uplink radio frequency signal one, and the uplink radio frequency signal two are different from each other. The frequency range of the wideband radio frequency signal covers DC to the carrier frequency of the downlink radio frequency signal.

[0043] Frequency selection unit one is configured to filter and select the frequency of the broadband radio frequency signal to obtain frequency selection signal one.

[0044] Frequency selection unit two is configured to filter and select the frequency of the broadband radio frequency signal to obtain frequency selection signal two.

[0045] Specifically, such as Figure 1 As shown, the operating frequency of frequency selection unit one is f. s1 The operating frequency of frequency selection unit two is f s2 The carrier frequency of uplink RF signal one is f1, and the carrier frequency of uplink RF signal two is f2. The relationship between f1 or f2 and f0 can be found in prior art, such as: Patent Document 1: CN202310112908.0 A passive frequency conversion structure and a passive frequency conversion method; or Patent Document 2: CN202411270397.6 Communication circuit, method, device and system.

[0046] Since the two uplink radio frequency signals have the same or similar generation environment and propagation path, one of the uplink radio frequency signals generated by the dual-frequency tag device is used as a reference. The differential signal is obtained based on the demodulated signal of the two uplink radio frequency signals. This differential signal represents the real target quantity, thereby solving the problems of poor demodulation accuracy and limited application scenarios caused by the inability to eliminate various interferences in a single uplink radio frequency signal.

[0047] The following uses a sensor tag device as an example to illustrate possible implementations of this application.

[0048] In one embodiment, the dual-frequency tag device can be used to construct an anti-interference, high-precision target parameter sensing device.

[0049] Understandably, for frequency modulation (FM) operation, the radio frequency (RF) is affected by the RF signal path (e.g., multipath effect, Doppler effect, power attenuation) and environmental factors (e.g., temperature, vibration). By demodulating the uplink RF signals of the dual-frequency signals to obtain differential signals, interference from non-target parameters can be canceled, resulting in pure target parameters. Specifically, both frequency selection unit one and frequency selection unit two can sense changes in the target parameters, and their target parameter sensing coefficients have opposite signs. The sensing capabilities of frequency selection unit one and frequency selection unit two for non-target parameters are the same or similar.

[0050] In the first example, the dual-frequency tag device is used to construct an interference-resistant, high-precision temperature sensing device. It can be understood that temperature is the target parameter, while other parameters such as strain and pressure are non-target parameters.

[0051] Please see Figure 2 In this embodiment, the passive mixer unit includes a transistor, and both frequency selection unit one and frequency selection unit two are sensing elements based on the principle of surface acoustic waves. The frequency selection unit one and frequency selection unit two are installed in close proximity, so that the external environmental influences sensed by them are the same or similar.

[0052] Preferably, the transistor is a high electron mobility transistor or a two-dimensional electron gas field-effect transistor, and one of the three ports of the passive mixer unit is any one of the gate, drain, or source. For example, port one is the drain, and port two and port three are any one of the gate or source; or, port one is the source, and port two and port three are any one of the gate or drain.

[0053] Optionally, the transistor is a bipolar transistor, and one of the three ports of the passive mixer unit is any one of the base, collector, or emitter. For example, port one is the base, and ports two and three are any one of the collector or emitter; or, port one is the emitter, and ports two and three are any one of the base or collector.

[0054] In this embodiment, both frequency selection unit one and frequency selection unit two can sense temperature changes, and their temperature coefficients have opposite signs (i.e., one is a positive temperature coefficient and the other is a negative temperature coefficient). Other parameters of the two units (e.g., strain, air pressure, humidity, etc.) are the same or similar. Both frequency selection unit one and frequency selection unit two are single-port surface acoustic wave resonators. Frequency selection unit one includes a piezoelectric material and an interdigital transducer one and a reflective grating one fabricated on the piezoelectric material. Frequency selection unit two includes a piezoelectric material and an interdigital transducer two and a reflective grating two fabricated on the piezoelectric material. The piezoelectric material of both frequency selection units is ST-cut quartz.

[0055] Typically, reflective gratings consist of a periodically arranged array of metal gratings. Surface acoustic waves (SAWs) undergo mechanical reflection at the grating due to discontinuities in acoustic impedance. Commonly used grating types include interdigitated gratings, short-circuit gratings, open-circuit gratings, and positive-negative gratings. Figure 2 In the example, both the first reflector and the second reflector are interdigitated reflectors.

[0056] It is understandable that the reflective grating can be designed to reflect only surface acoustic waves of a specific frequency by adjusting its characteristic parameters (such as grating width, spacing between grating electrodes, grating type, and grating electrode material). For example, the center frequencies of frequency selection unit one and frequency selection unit two are 20.2MHz and 20.8MHz, respectively. Furthermore, if the carrier frequency of the downlink RF signal is 430MHz, and the first-order, low-frequency side mixing result is selected as the carrier frequency of the uplink RF signal, then the carrier frequency of uplink RF signal one is 409.8MHz, and the carrier frequency of uplink RF signal two is 409.2MHz.

[0057] In the second example, the dual-frequency tag device is used to construct an anti-interference, high-precision temperature sensing device. It can be understood that temperature is the target parameter, while other parameters such as strain and pressure are non-target parameters.

[0058] Please see Figure 3 In this embodiment, the passive mixer unit includes a transistor. Frequency selection unit one and frequency selection unit two are mounted adjacent to each other, so that they experience the same or similar external environmental influences. Frequency selection unit one includes an LC resonant unit one and a reference element, while frequency selection unit two includes an LC resonant unit two and a sensing element. LC resonant unit one includes a capacitor C1 and an inductor L1 connected in parallel, and LC resonant unit two includes a capacitor C2 and an inductor L2 connected in parallel. The operating center frequency of LC resonant unit one is f. s1 The operating center frequency of the second LC resonant unit is f. s2 The temperature coefficients of the reference element and the sensing element have opposite signs, while other parameters are the same or similar.

[0059] For example, the temperature coefficient of the reference element is positive, and the temperature coefficient of the sensing element is negative; or vice versa.

[0060] Preferably, the transistor is a high electron mobility or two-dimensional electron gas field-effect transistor, and one of the three ports of the passive mixer unit can be any one of the gate, drain or source.

[0061] Optionally, the transistor is a bipolar transistor, and one of the three ports of the passive mixer unit can be any one of the base, collector, or emitter.

[0062] It is understandable that, in the two examples mentioned above, for the uplink radio frequency signal 1 (whose carrier frequency is f1), the read / write device can demodulate the nominal sensing quantity 1C according to the preset relationship between frequency and sensing quantity. total1 =C temp1 +C else1 , where C temp1 C is the temperature sensing quantity sensed by the frequency selection unit. else1 Interference caused by other factors, including but not limited to multipath interference, Doppler effect, vibration, and pressure. For the uplink RF signal 2 (with carrier frequency f2), the read / write device can demodulate the nominal sensing quantity 2C according to the preset relationship between frequency and sensing quantity. total2 =C temp2 +C else2 , where C temp2 C is the temperature sensing quantity sensed by the frequency selection unit two. else2 The interference amount is caused by other factors, including but not limited to multipath interference, Doppler effect, vibration, and pressure. Since the generation and propagation environments of uplink RF signal one and uplink RF signal two are the same or similar, the interference amounts calculated from the two RF signals can be considered approximately equal, i.e., C. else1 =C else2 Furthermore, the read / write device can obtain the differential sensing quantity C by differentiating the two nominal sensing quantities. dif This eliminates common-mode interference. Wherein, C dif =C total1 -C total2 =C temp1 -C temp2 .

[0063] Since the temperature coefficients of frequency selection unit one and frequency selection unit two have opposite signs, the value of the differential sensing quantity is |C dif |=|C temp1 |+|C temp2 |, where the symbol "| * |" represents taking the absolute value of the variable "*". When the absolute values ​​of two temperature coefficients are the same or similar, the differential sensing quantity |C dif |=2|C temp1 |=2|C temp2 Therefore, compared to a single-frequency tag device (assuming the nominal sensing quantity obtained by the single-frequency tag device is C), it is clear that... total3 =C temp3 +C else3 Dual-frequency tag devices can not only eliminate environmental common-mode interference to obtain pure target sensing data, but also improve the sensitivity to target sensing data.

[0064] In this embodiment, temperature is the target parameter. It is understood that the target parameter can also be other physical quantities, such as strain, vibration, pressure, humidity, displacement, tilt angle, etc.

[0065] In the third example, strain is the target parameter. A dual-frequency tag device can be used to construct an interference-resistant, high-precision strain sensing device. Based on the first example of the aforementioned temperature sensing device, please refer to... Figure 2 Both frequency selection unit one and frequency selection unit two are sensing elements based on the surface acoustic wave principle. They are installed close to each other, ensuring that they sense similar or identical external environmental influences. Both units can sense strain changes, and their strain coefficients have opposite signs (one is a positive strain coefficient, and the other a negative strain coefficient). Other parameters of the two units (such as temperature, air pressure, and humidity) are the same or similar. Therefore, this dual-frequency tag device not only eliminates common-mode interference from the environment to obtain pure target sensing data but also improves the sensitivity to target sensing data.

[0066] Optionally, in other embodiments, frequency selection unit one is insensitive to changes in the target parameter, while frequency selection unit two can sense changes in the target parameter. The non-target parameters of frequency selection units one and two are the same or similar. With this configuration, an interference-resistant, high-precision target parameter sensing device can still be constructed.

[0067] For example, based on the first example, frequency selection unit one is not sensitive to temperature, while frequency selection unit two can sense temperature changes. Other parameters of the two units (e.g., strain, air pressure, humidity, etc.) are the same or similar. In this case, for uplink radio frequency signal one (whose carrier frequency is f1), the read / write device can demodulate the nominal sensed quantity one C according to the preset relationship between frequency and sensed quantity. total1 =C else1 For the uplink radio frequency signal 2 (whose carrier frequency is f2), the read / write device can demodulate the nominal sensing quantity 2C according to the preset relationship between frequency and sensing quantity. total2 =C temp2 +C else2 Since the generation and propagation environments of uplink RF signal one and uplink RF signal two are the same or similar, the interference quantities calculated from the two RF signals can be considered approximately equal, i.e., C. else1 =C else2 Furthermore, the read / write device can obtain the differential sensing quantity C by differentiating the two nominal sensing quantities. dif This eliminates common-mode interference. Where, |C dif |=|C temp2 Therefore, compared to a single-frequency tag device (assuming the nominal sensing quantity obtained by the single-frequency tag device is C), it is clear that... total3 =C temp3 +Celse3 Dual-frequency tag devices can eliminate environmental common-mode interference to obtain pure target sensing data, thereby improving sensing accuracy.

[0068] In one embodiment, the dual-frequency tag device can be used to construct an anti-interference, non-target parameter compensation sensing device.

[0069] In the fourth example, the dual-frequency tag device is used to construct an anti-interference, temperature-compensated strain sensing device. It can be understood that temperature is a non-target parameter, while strain is the target parameter. Based on the aforementioned first example of a temperature sensing device, please refer to... Figure 2 Both frequency selection unit one and frequency selection unit two are sensing elements based on the surface acoustic wave principle. They are installed close to each other, ensuring that they sense similar or identical external environmental influences. Both units can sense strain changes, and their strain coefficients have opposite signs (one is a positive strain coefficient, and the other is a negative strain coefficient). Their temperature coefficients are the same or similar. Therefore, this dual-frequency tag device not only eliminates temperature-induced interference to obtain pure target sensing data but also improves the sensitivity to target sensing data.

[0070] In the fifth example, the dual-frequency tag device is used to construct an anti-interference, temperature-compensated strain sensing device. It can be understood that temperature is a non-target parameter, while strain is the target parameter. Based on the aforementioned second example of a temperature sensing device, please refer to... Figure 3 Both the reference element and the sensing element can sense strain changes, and their strain coefficients have opposite signs (i.e., one is a positive strain coefficient and the other is a negative strain coefficient). Furthermore, the temperature coefficients of the reference element and the sensing element are the same or similar. Therefore, this dual-frequency tag device not only eliminates temperature-induced interference to obtain pure target sensing data but also improves the sensitivity to target sensing data.

[0071] Although this application has been described herein with reference to illustrative embodiments, it should be understood that many other modifications and implementations can be devised by those skilled in the art, which will fall within the scope and spirit of the principles disclosed herein. More specifically, within the scope of this application, various variations and improvements can be made to the components and / or layout of the subject matter combination layout. Besides variations and improvements to the components and / or layout, other uses will be apparent to those skilled in the art.

Claims

1. A dual-frequency tag device, characterized in that, include: Antenna, passive mixer unit, frequency selection unit one and frequency selection unit two; Port 1 of the passive mixer unit is electrically connected to the antenna, port 2 of the passive mixer unit is electrically connected to frequency selection unit 1, and port 3 of the passive mixer unit is electrically connected to frequency selection unit 2; the operating frequencies of frequency selection unit 1 and frequency selection unit 2 are different. Frequency selection unit one and frequency selection unit two adopt one of the following configurations: Configuration 1: Both frequency selection unit 1 and frequency selection unit 2 can sense changes in target parameters, and the signs of their target parameter sensing coefficients are opposite. The sensing capabilities of frequency selection unit 1 and frequency selection unit 2 for non-target parameters are the same or similar. Configuration 2: Frequency selection unit 1 is insensitive to changes in the target parameter, while frequency selection unit 2 can sense changes in the target parameter. The sensing capabilities of frequency selection unit 1 and frequency selection unit 2 for non-target parameters are the same or similar.

2. The apparatus according to claim 1, characterized in that, The passive mixer unit is configured to generate a broadband radio frequency signal based on the downlink radio frequency signal transmitted by the antenna, passively mix the frequency-selected signal obtained by the frequency selection unit one with the downlink radio frequency signal to obtain the uplink radio frequency signal one, and passively mix the frequency-selected signal obtained by the frequency selection unit two with the downlink radio frequency signal to obtain the uplink radio frequency signal two; wherein, the frequency range of the broadband radio frequency signal covers DC to the carrier frequency of the downlink radio frequency signal; the carrier frequencies of the downlink radio frequency signal, the uplink radio frequency signal one, and the uplink radio frequency signal two are different from each other.

3. The apparatus according to claim 1 or 2, characterized in that, The passive mixer unit includes transistors.

4. The apparatus according to claim 3, characterized in that, The transistor is a high electron mobility transistor or a two-dimensional electron gas field effect transistor, and one of the three ports of the passive mixer unit is any one of the gate, drain or source.

5. The apparatus according to claim 3, characterized in that, The transistor is a bipolar transistor, and one of the three ports of the passive mixer unit is any one of the base, collector, or emitter.

6. The apparatus according to claim 1 or 2, characterized in that, Both frequency selection unit one and frequency selection unit two are single-port surface acoustic wave resonators.

7. The apparatus according to claim 1 or 2, characterized in that, Frequency selection unit one includes LC resonant unit one and reference element, and frequency selection unit two includes LC resonant unit two and sensing element. The operating center frequencies of LC resonant unit one and LC resonant unit two are different. The target parameter sensing coefficients of the reference element and the sensing element are opposite, while the non-target parameters are the same or similar.

8. The apparatus according to claim 1 or 2, characterized in that, The target parameter is one of temperature, strain, pressure, humidity, vibration, displacement, or tilt angle.

9. A dual-frequency tag system, characterized in that, The device includes a read / write device and a dual-frequency tag device as described in any one of claims 1-8, wherein the read / write device sends downlink messages and receives uplink messages; wherein the downlink message includes a downlink radio frequency signal and the uplink message includes an uplink radio frequency signal one and an uplink radio frequency signal two.

10. The system according to claim 9, characterized in that, The read / write device obtains a nominal sensing quantity one based on the uplink radio frequency signal one, obtains a nominal sensing quantity two based on the uplink radio frequency signal two, and obtains a differential sensing quantity based on the nominal sensing quantity one and the nominal sensing quantity two.

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