A sub-gigahertz based airborne wireless sensor network node system and matching network computing system

Abstract

The application discloses a kind of Sub-GHz-based airborne wireless sensor network node system and matching network calculation method, including sensor sensitive unit module, single-chip microcomputer control module, wireless communication module and power supply module;With the compatibility between the original equipment of Sub-GHz-based wireless communication module design ensures airborne, optimize impedance matching circuit makes transmission power reach 20dBM, center frequency 915MHz, bandwidth 530MHz, at the suppression of secondary harmonic frequency and third harmonic frequency reaches-40dB below, wireless module maximum transmission rate can reach 2Mbps, and through electromagnetic compatibility test ensures the anti-interference of wireless communication module.The application has strong anti-interference ability, signal attenuation is slow, and low power consumption is suitable for solving cabin complex environment.

Description

Technical Field

[0001] This invention belongs to the field of wireless sensor network design, specifically relating to a Sub-GHz-based airborne wireless sensor network node system and a matching network computing system. Background Technology

[0002] With the rapid development of aircraft technology and the increasing sophistication of avionics system functions, airborne wireless sensor networks can acquire physical information from a large number of miniature sensors deployed in the cabin. This information is then aggregated to processing nodes via a wireless network for preliminary data fusion and processing. This solves the problems of wiring difficulties, poor flexibility, poor fault tolerance, and difficulty in isolating faults caused by wired sensor connections, enabling precise management and control of aircraft.

[0003] Airborne wireless sensor network nodes are typically deployed in the cabin or wings to monitor aircraft operation. The application scenarios are complex, with limited space and many metal obstacles. The presence of numerous high-frequency electronic devices and other wireless communication devices leads to a complex electromagnetic environment. In terms of communication frequency selection, Sub-GHz has stronger anti-interference capabilities, lower node power consumption, and slower signal attenuation compared to 2.4GHz, making it more suitable for the special environment inside the cabin. At the same time, the narrow bandwidth limitation of Sub-GHz results in a relatively low communication rate, while impedance matching networks can achieve maximum power output, reduce circuit losses, and maximize the communication rate.

[0004] Liu Rong and Chen Jingang developed a target detection system based on WSN technology (Liu Rong, Chen Jingang. Design and Implementation of Low-Power Target Detection System Based on Wireless Sensor Network [J]. Spacecraft Environmental Engineering, 2021, 38(02):218-223.), which realizes signal acquisition and high-speed data transmission from various types of sensors, and optimizes the system's low-power design to meet the requirements of long-term use of wireless sensors. However, its wireless communication module has low power and a low maximum transmission rate of only 150 kbit / s, making it difficult to transmit a large amount of measurement data from various types of sensors simultaneously.

[0005] Yan Linbo developed a wireless communication device based on ZigBee technology (Yan Linbo. Research on wireless communication module based on ZigBee technology [J]. Science and Technology Innovation, 2020(29):88-89.), realizing low-power, low-cost wireless communication in a small area. Low power consumption, low cost, large capacity, and short latency meet the requirements for long-term use of wireless sensors. However, ZigBee technology is based on the IEEE 802.15.4 protocol and operates at 2.4GHz. In airborne environments, it is prone to interfering with other airborne equipment, and its diffraction capability is poor, which is not conducive to the overall reliability of wireless sensor networks. Summary of the Invention

[0006] The purpose of this invention is to provide a Sub-GHz-based airborne wireless sensor network node system and matching network computing system to meet the practical application requirements of strong anti-interference capability, fast transmission rate, and adaptability to harsh environments.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A Sub-GHz-based airborne wireless sensor network node system includes a sensor sensing unit module, a microcontroller control module, a wireless communication module, and a power supply module.

[0009] The sensor sensing unit module is used to measure environmental parameters inside the cabin, convert the measured values ​​into analog voltage signals for output, and perform filtering and amplification processing.

[0010] The microcontroller control module is connected to the sensitive unit module. It quantizes and encodes the conditioned analog voltage signal, converts it into a digital signal, and sends the data to the wireless communication chip via the SPI bus. It also controls the working state of the wireless communication chip through a specific SPI command set.

[0011] The wireless communication module uses an A7128 chip as its main body. It is connected to the microcontroller control module via the SPI bus, receives the processed data, organizes the data into wireless data packets according to the wireless communication protocol, and transmits them through the antenna using a 50Ω impedance matching network connected to the transmitting antenna.

[0012] The power supply module is used to supply power to the sensor sensing unit module, the microcontroller control module, and the wireless communication module.

[0013] Furthermore, the sensor sensing unit module includes a high-frequency vibration sensor, a low-frequency vibration sensor, and a signal conditioning circuit; the signal conditioning circuit includes a filtering circuit and an amplification circuit, the filtering circuit being used to remove high-frequency noise from the analog voltage signal; the amplification circuit is primarily a low-power precision instrumentation amplifier, used to amplify the amplitude of the analog voltage signal, suppress signal noise, and improve signal driving capability.

[0014] Furthermore, the power supply module uses a standard voltage 3.7V lithium battery as input, and its output includes an intermittent power supply circuit connected to the sensitive unit module and a constant power supply circuit connected to the microcontroller control module and the wireless communication module.

[0015] Furthermore, the 50Ω impedance matching network includes an RF input matching circuit and an RF output matching circuit;

[0016] The radio frequency input matching circuit includes a Chebyshev low-pass filter and a T-type impedance matching circuit connected in series therewith, which filters out the high-order harmonics brought by the input intermediate frequency signal, so that the antenna and the chip input end achieve conjugate impedance matching.

[0017] The radio frequency output matching circuit includes a broadband matching network, a harmonic control network, and a choke inductor.

[0018] The broadband matching network consists of a first-stage low-pass L-type matching circuit and a first-stage high-pass L-type matching circuit connected in series.

[0019] The harmonic control network is connected at one end to a choke inductor and at the other end to a broadband matching network, including a second harmonic control circuit, a third harmonic control circuit, and an inductor. ;

[0020] The choke inductor Used to prevent DC power supply ripple from modulating the radio frequency signal and to prevent the radio frequency signal from leaking into the DC power supply, thus reducing the output signal.

[0021] Furthermore, the second harmonic control circuit is composed of , , The circuit consists of a second harmonic control circuit that short-circuits the second harmonic current to ground at the second harmonic frequency, thereby achieving short-circuit control of the second harmonic.

[0022] The third harmonic control circuit includes , , , The first branch and , , The second branch is formed, and the first branch is at the fundamental frequency. The first and second branches are connected in parallel to achieve resonance at the third harmonic frequency, thus realizing open-circuit control of the third harmonic.

[0023] Furthermore, at the fundamental frequency, the second harmonic control circuit and the third harmonic control circuit are equivalent to capacitors, forming two L-shaped low-pass matching circuits connected in series; by appropriately increasing the bandwidth, the higher harmonics are filtered and attenuated.

[0024] Furthermore, one end of the choke inductor is connected to the chip's RF output pin, and the other end is connected to the DC power supply terminal.

[0025] Furthermore, the calculation steps for the 50Ω impedance matching network circuit parameters of the wireless communication module are as follows:

[0026] Step 1: Determine the source impedance , Ω and load impedance That is, 50Ω, the operating frequency of the impedance matching network. and the optimal impedance of the chip power amplifier tube That is, 10.6Ω; calculate the intermediate impedance between the harmonic control network and the broadband matching network. To ensure a stable gain for the entire matching network within the operating frequency band, we can obtain:

[0027]

[0028] Step 2: Calculate the quality factor of the broadband matched network based on the intermediate impedance.

[0029]

[0030] The broadband matching network consists of a first-stage low-pass L-type matching circuit and a first-stage high-pass L-type matching circuit connected in series, based on the aforementioned quality factor. and intermediate impedance Calculate the operating angular frequency And the parameters of each component:

[0031] , ,

[0032] ,

[0033] Step 3: Measure the parasitic capacitance of the chip's RF output pins. Choke inductor , The size is usually the optimal impedance. 11 times; at the fundamental frequency , The circuit resonates in parallel with the second harmonic control circuit, at which point the circuit matching factor... for:

[0034]

[0035] The circuit parameters are as follows:

[0036] , ,

[0037] Under second harmonic conditions, the second harmonic control circuit exhibits series resonance, and this resonant circuit functions as an equivalent capacitor at the fundamental frequency. :

[0038]

[0039] In the third harmonic control circuit, during the third harmonic, the first and second branches resonate in parallel. The second harmonic control circuit is equivalent to an inductor. At this time, the input impedance of the entire circuit is infinite, and the circuit parameters are as follows:

[0040] , ,in , According to The relationship can be flexibly valued.

[0041] , .

[0042] The beneficial effects of this invention are as follows:

[0043] 1. The adoption of a Sub-GHz-based wireless communication module design ensures compatibility with existing airborne equipment, strong anti-interference capability, slow signal attenuation, and low power consumption, making it suitable for solving complex cabin environments.

[0044] 2. The impedance matching circuit was optimized to achieve a transmission power of 20dBm, a center frequency of 915MHz, a bandwidth of 530MHz, and a suppression of less than -40dB at the second and third harmonic frequencies. The maximum transmission rate of the wireless module can reach 2Mbps, and the anti-interference capability of the wireless communication module has been guaranteed through electromagnetic compatibility testing. Attached Figure Description

[0045] Figure 1 This is a block diagram of the overall structure of the airborne wireless sensor network node system of the present invention;

[0046] Figure 2 This is the radio frequency input matching circuit of the present invention;

[0047] Figure 3 This is the radio frequency output matching circuit of the present invention. Detailed Implementation

[0048] The present invention will now be further described with reference to the accompanying drawings.

[0049] like Figure 1 The diagram shown is an overall structural block diagram of the airborne wireless sensor network node system of the present invention.

[0050] In this invention, the airborne wireless sensor network node system includes the following modules:

[0051] The sensor sensing unit module includes a high-frequency vibration sensor, a low-frequency vibration sensor, and a signal conditioning circuit, which is used to measure the vibration intensity at various locations inside the cabin, convert the measured values ​​into analog voltage signals for output, and perform filtering and amplification processing.

[0052] The microcontroller control module is connected to the sensor sensing unit module. It quantizes and encodes the conditioned analog voltage signal, converts it into a digital signal, and sends the data to the wireless communication chip via the SPI bus. It also controls the working state of the wireless communication module through the unique SPI command set of the A7128.

[0053] The wireless communication module is connected to the microcontroller control module via the SPI bus. It receives the processed data, organizes the data into wireless data packets according to the wireless communication protocol, and transmits them through the antenna. A 50Ω impedance matching network is connected between the antenna and the RF chip to achieve maximum signal power transmission, reduce power loss during transmission, and reduce output harmonic distortion.

[0054] The power supply module is used to supply power to the aforementioned sensor sensing unit module, microcontroller control module, and wireless communication module.

[0055] The aforementioned sensor sensing unit module consists of a vibration sensor section and a signal conditioning section. The signal conditioning section includes filtering and signal amplification circuits. The filtering circuit removes high-frequency noise from the analog voltage signal output by the sensor.

[0056] The aforementioned microcontroller control module uses STMicroelectronics' STM32L072KB microcontroller. The supporting circuits include LED indicator circuits, battery voltage monitoring circuits, clock circuits, power-on reset circuits, power supply filtering circuits, etc., and also control the working status of the A7128 wireless communication chip.

[0057] The aforementioned wireless communication module uses the Shengke A7128 wireless communication chip. The operating status of the communication chip is controlled by the microcontroller module through the A7128's unique SPI command set. The A7128 supports shutdown mode (no register reservation), sleep mode (register reservation), idle mode, and standby mode.

[0058] The aforementioned power supply module uses a single lithium battery, model LP14500-900, and uses a TPS62740 chip to convert the battery voltage to a fixed 2.1V for continuous power supply to the microcontroller control module and wireless communication module. It uses an LT6656 power chip to provide intermittent power to the sensor sensing unit module.

[0059] The 50Ω impedance matching network includes an RF input matching circuit and an RF output matching circuit.

[0060] RF input matching circuit such as Figure 2 As shown, it includes a Chebyshev low-pass filter 30 and a T-type impedance matching circuit (40) connected in series with it to filter out high-order harmonics brought by the input intermediate frequency signal, so that the antenna and the chip input end achieve conjugate impedance matching.

[0061] RF output matching circuit such as Figure 3 As shown, it includes a broadband matching network 10, a harmonic control network 20, and a choke inductor;

[0062] The broadband matching network consists of a single-stage low-pass L-type matching circuit ( , ) and a first-stage Qualcomm L-type matching circuit ( , ) in series;

[0063] The choke inductor One end is connected to the DC power supply terminal, and the other end is connected to the chip's RF output pin.

[0064] The harmonic control network is connected at one end to a choke inductor and at the other end to a broadband matching network. It includes a second harmonic control circuit 21, a third harmonic control circuit 22, and an inductor. .

[0065] Second harmonic control circuit 21 consists of , The circuit consists of a second harmonic control circuit that short-circuits the second harmonic current to ground at the second harmonic frequency, thereby achieving short-circuit control of the second harmonic.

[0066] The third harmonic control circuit 22 includes , , , The first branch and , , The second branch is formed, and the first branch is at the fundamental frequency. The first and second branches are connected in parallel to achieve resonance at the third harmonic frequency, thus realizing open-circuit control of the third harmonic.

[0067] At the fundamental frequency, the second harmonic control circuit and the third harmonic control circuit are equivalent to capacitors, forming two L-shaped low-pass matching circuits connected in series. This can appropriately increase the bandwidth and also serve as a filter and attenuator for higher harmonics.

[0068] The calculation steps for the RF output matching circuit parameters of the above 50Ω impedance matching network are as follows:

[0069] Step 1: Determine the source impedance , Ω and load impedance (Typically 50Ω), the operating frequency of the impedance matching network. and the optimal impedance of the chip power amplifier tube. (10.6Ω). Calculate the intermediate impedance between the harmonic control network and the broadband matching network. To ensure a stable gain for the entire matching network within the operating frequency band, we can obtain:

[0070] (1)

[0071] Step 2: Calculate the quality factor of the broadband matched network based on the intermediate impedance.

[0072] (2)

[0073] The broadband matching network consists of a first-stage low-pass L-type matching circuit and a first-stage high-pass L-type matching circuit connected in series, based on the aforementioned quality factor. and intermediate impedance Calculate the operating angular frequency And the parameters of each component:

[0074] , , (3)

[0075] , (4)

[0076] Step 3: Measure the parasitic capacitance of the chip's RF output pins. Confirm the choke inductor , The size is usually the optimal impedance. Approximately 11 times that at the fundamental frequency. , The circuit resonates in parallel with the second harmonic control circuit, at which point the circuit matching factor... for:

[0077] (5)

[0078] The circuit parameters are as follows:

[0079] , , (6)

[0080] Under second harmonic conditions, the second harmonic control circuit exhibits series resonance, and this resonant circuit can be equivalent to a capacitor at the fundamental frequency. ,

[0081] (7)

[0082] In the third harmonic control circuit, during the third harmonic, the first and second branches resonate in parallel. The second harmonic control circuit is equivalent to an inductor. At this time, the input impedance of the entire circuit is infinite, and the circuit parameters are as follows:

[0083] , ( , According to (8) The relationship can be flexibly determined.

[0084] , (9)

[0085] By optimizing the impedance matching network, the transmission power reaches 20dBm, the center frequency is 915MHz, the bandwidth is 530MHz, the suppression at the second and third harmonic frequencies is below -40dB, the maximum transmission rate of the wireless module can reach 2Mbps, and the anti-interference capability of the wireless communication module is guaranteed by passing electromagnetic compatibility tests.

[0086] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A Sub-GHz-based airborne wireless sensor network node system, characterized in that: It includes a sensor sensing unit module, a microcontroller control module, a wireless communication module, and a power supply module; The sensor sensing unit module is used to measure environmental parameters inside the cabin, convert the measured values ​​into analog voltage signals for output, and perform filtering and amplification processing. The microcontroller control module is connected to the sensitive unit module. It quantizes and encodes the conditioned analog voltage signal, converts it into a digital signal, and sends the data to the wireless communication chip via the SPI bus. It also controls the working state of the wireless communication chip through a specific SPI command set. The wireless communication module uses an A7128 chip as its main body. It is connected to the microcontroller control module via the SPI bus, receives the processed data, organizes the data into wireless data packets according to the wireless communication protocol, and transmits them through the antenna using a 50Ω impedance matching network connected to the transmitting antenna. The 50Ω impedance matching network includes an RF input matching circuit and an RF output matching circuit. The calculation steps for the 50Ω impedance matching network circuit parameters are as follows: Step 1: Determine the source impedance , Ω and load impedance That is, 50Ω, the operating frequency of the impedance matching network. and the optimal impedance of the chip power amplifier tube. That is, 10.6Ω; calculate the intermediate impedance between the harmonic control network (20) and the broadband matching network (10). To ensure stable gain across the entire matching network within the operating frequency band, Step 2: Calculate the quality factor of the broadband matching network (10) based on the intermediate impedance. , The broadband matching network (10) includes a first-stage low-pass L-type matching circuit and a first-stage high-pass L-type matching circuit connected in series, based on the aforementioned quality factor. and intermediate impedance Calculate the operating angular frequency And the parameters of each component: ， , ， Step 3: Measure the parasitic capacitance of the chip's RF output pins. Choke inductor , The size is usually the optimal impedance. 11 times; at the fundamental frequency , The second harmonic control circuit (21) resonates in parallel, at which point the circuit matching factor... for: The circuit parameters are as follows: ， ， Under the second harmonic, the second harmonic control circuit (21) undergoes series resonance, and the resonant circuit is equivalent to a capacitor at the fundamental frequency. : In the third harmonic control circuit (22), during the third harmonic, the first branch and the second branch resonate in parallel. The second harmonic control circuit (21) is equivalent to an inductor. At this time, the input impedance of the entire circuit is infinite, and the circuit parameters are as follows: ， ， in , According to The relationship can be flexibly valued. ， ； The radio frequency input matching circuit includes a Chebyshev low-pass filter (30) and a T-type impedance matching circuit (40) connected in series therewith, which filters out the high-order harmonics brought by the input intermediate frequency signal, so that the antenna and the chip input end achieve conjugate impedance matching. The RF output matching circuit includes a broadband matching network (10), a harmonic control network (20), and a choke inductor; The broadband matching network (10) consists of a first-stage low-pass L-type matching circuit and a first-stage high-pass L-type matching circuit connected in series; The harmonic control network (20) is connected at one end to a choke inductor and at the other end to a broadband matching network (10), and includes a second harmonic control circuit (21), a third harmonic control circuit (22), and an inductor. ; The choke inductor Used to prevent DC power supply ripple from modulating the radio frequency signal and to prevent the radio frequency signal from leaking into the DC power supply, thus reducing the output signal. The power supply module is used to supply power to the sensor sensing unit module, the microcontroller control module, and the wireless communication module.

2. The airborne wireless sensor network node system based on Sub-GHz according to claim 1, characterized in that: The sensor sensing unit module includes a high-frequency vibration sensor, a low-frequency vibration sensor, and a signal conditioning circuit; the signal conditioning circuit includes a filtering circuit and an amplification circuit, the filtering circuit is used to remove high-frequency noise from the analog voltage signal; the main body of the amplification circuit is a low-power precision instrumentation amplifier, used to amplify the amplitude of the analog voltage signal, suppress signal noise, and improve signal driving capability.

3. The airborne wireless sensor network node system based on Sub-GHz according to claim 1, characterized in that: The power supply module uses a standard voltage 3.7V lithium battery as input, and its output includes an intermittent power supply circuit connected to the sensitive unit module and a constant power supply circuit connected to the microcontroller control module and the wireless communication module.

4. The airborne wireless sensor network node system based on Sub-GHz according to claim 1, characterized in that: The second harmonic control circuit (21) is composed of , , Composition, at the second harmonic frequency, the second harmonic current is short-circuited to ground by the second harmonic control circuit (21) to realize the short-circuit control of the second harmonic; The third harmonic control circuit (22) includes , , , The first branch and , , The second branch is formed, and the first branch is at the fundamental frequency. The first and second branches are connected in parallel to achieve resonance at the third harmonic frequency, thus realizing open-circuit control of the third harmonic.

5. The airborne wireless sensor network node system based on Sub-GHz according to claim 1, characterized in that: At the fundamental frequency, the second harmonic control circuit (21) and the third harmonic control circuit (22) are equivalent to capacitors, forming two L-shaped low-pass matching circuits connected in series; by appropriately increasing the bandwidth, the higher harmonics are filtered and attenuated.

6. The airborne wireless sensor network node system based on Sub-GHz according to claim 1, characterized in that: One end of the choke inductor is connected to the chip's RF output pin, and the other end is connected to the DC power supply.

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