Unmanned aerial vehicle high-precision positioning module based on printed four-arm helical antenna

Abstract

The utility model discloses an unmanned aerial vehicle high-precision positioning module based on a printed quadrifilar helix antenna, relates to the technical field of satellite navigation and unmanned aerial vehicle positioning, and aims to provide an unmanned aerial vehicle positioning module with high positioning precision. According to the module, the multi-frequency four-arm helical antenna, the multi-stage radio frequency signal processing circuit and the redundant power supply system are integrated, so that the positioning precision and the anti-interference capability are remarkably improved. The antenna specifically comprises a double-frequency four-arm helical antenna adopting a gold-plated copper radiator, and a broadband impedance matching network constructed by combining a hybrid coupler; the low-noise signal processing link consists of an amplifier, a two-stage filter and a post-stage amplifier; the method is based on a high-precision satellite positioning calculation unit. The module realizes rapid integration through a multi-pin plug-in, has centimeter-level positioning precision, multipath interference resistance and power-off emergency cruising ability, and is suitable for accurate navigation and position return of an unmanned aerial vehicle in a complex electromagnetic environment.

Description

TECHNICAL FIELD

[0001] The utility model relates to satellite navigation and unmanned aerial vehicle positioning technical field, more specifically, it relates to a kind of high-precision positioning module of unmanned aerial vehicle based on printed four-arm helical antenna. BACKGROUND

[0002] With the rapid development of unmanned aerial vehicle technology, high-precision positioning has become a key technology demand of unmanned aerial vehicle in surveying, agriculture, logistics and emergency rescue fields. At present, unmanned aerial vehicle positioning mainly relies on global navigation satellite system (GNSS), but due to the influence of urban canyon, complex electromagnetic environment and multipath effect and other factors, the precision and reliability of traditional single-frequency GNSS positioning module are difficult to meet the needs of high-precision application scenarios. In the prior art, the following technical problems exist in the unmanned aerial vehicle positioning module:

[0003] 1. Insufficient antenna performance: traditional single-frequency microstrip antenna or ceramic antenna performs poorly in multi-band compatibility, anti-multipath interference and low-elevation signal reception capability, resulting in limited positioning accuracy. For example, the gain of single-frequency antenna fluctuates greatly in L1 frequency band, and has almost no response to L2 frequency band signal, which makes it difficult to meet the needs of double-frequency high-precision positioning.

[0004] 2. Complex RF front-end design: existing double-frequency positioning modules usually use discrete filter and amplifier design, resulting in large circuit size, high power consumption, and difficulty in achieving good impedance matching. For example, some modules use multi-stage LC filter and independent amplifier combination, which not only increases the circuit complexity, but also introduces additional noise, reducing the signal-to-noise ratio (SNR).

[0005] 3. Poor power stability: unmanned aerial vehicles may face power fluctuations or temporary power outages during flight, and the power design of traditional positioning modules lacks backup power support, resulting in positioning interruption or data loss. For example, some modules rely only on linear voltage regulator for power supply, which is easy to trigger under-voltage protection when the input voltage fluctuates, affecting the continuity of positioning.

[0006] 4. Low interface integration: the power and data interfaces of existing modules usually use discrete design, resulting in complex installation and insufficient reliability. For example, some modules use multiple independent connectors for power supply and data transmission, increasing the difficulty and failure rate of system integration.

[0007] 5. Weak anti-interference capability: in complex electromagnetic environment, the RF circuit of traditional modules is easily disturbed by external interference, resulting in decreased positioning accuracy. For example, some modules do not use effective filtering and shielding design, and may experience positioning drift or loss of lock under strong electromagnetic interference. INVENTION CONTENTS

[0008] The unmanned aerial vehicle high-precision positioning module based on the printed four-arm helical antenna aims at solving the technical problems mentioned in the background art.

[0009] To achieve the above object, the utility model provides the following technical scheme: an unmanned aerial vehicle high-precision positioning module based on a printed four-arm helical antenna,

[0010] Overall structure

[0011] The positioning module adopts a layered structure design and comprises a four-arm helical antenna unit, a radio frequency combining circuit, a signal processing link, a GNSS processing module, a power supply system and a modular interface assembly. Each unit is efficiently integrated through a signal link and a power supply link, and the overall size is 67.7mm*68mm*16mm, which is suitable for compact space installation of an unmanned aerial vehicle.

[0012] Four-arm helical antenna unit

[0013] 1. An L1 / L2 dual-frequency four-arm helical antenna design is adopted, the radiator is made of gold-plated copper material, the radiator comprises a plurality of helical arms printed on an FPC board, the helical arm spacing is 2mm, and the antenna height is 10mm.

[0014] 2. The FPC board is wrapped around the support ring, the support ring is welded on the FR4 substrate, the FR4 material specifically refers to an epoxy glass fiber plate with a flame resistance grade of FR4, which is made of epoxy resin as an adhesive and electronic grade glass fiber cloth as a reinforcing material.

[0015] 3. The surface of the antenna support ring is covered with a polytetrafluoroethylene (PTFE) protective layer, the dielectric constant is 2.2, and the thickness is 2mm, which is used to reduce the influence of environmental humidity on the performance of the antenna.

[0016] 4. L1 / L2 dual-band resonance is realized through a four-feed-point quadrature feed structure, the L1 band (1575.42MHz) gain is greater than or equal to 5dBi, the L2 band (1227.60MHz) gain is greater than or equal to 4dBi, and the half-power beam width is greater than or equal to 80°.

[0017] Radio frequency combining circuit

[0018] 1. Two hybrid couplers one and one hybrid coupler two are contained for realizing impedance matching and combining transmission of dual-frequency signals, wherein the hybrid coupler one selects an LTCC 3dB hybrid coupler, and the hybrid coupler two selects an HC14F03 3dB hybrid coupler.

[0019] 2. Two LTCC 3dB couplers are respectively connected with the quadrature feed ports of the four-arm helical antenna, the output end is combined into a single radio frequency signal through the HC14F03 3dB coupler, the port standing wave ratio is less than or equal to 1.5, and the insertion loss is less than or equal to 0.5dB.

[0020] Signal processing link

[0021] 1. The signal processing link comprises a first-stage low-noise amplifier (CKRF3509MM34), a first-stage filter (TA1621A), a second-stage filter (SF9030), and a second-stage amplifier (SGL0622Z) in sequence.

[0022] 2. The first-stage low-noise amplifier has a gain of 20 dB and a noise figure of ≤0.8 dB; the first-stage filter is a TA1621A band-pass filter with a center frequency of 1575.42 MHz and a bandwidth of 20 MHz; the second-stage filter is a SF9030 band-pass filter with a center frequency of 1227.60 MHz and a bandwidth of 24 MHz; and the second-stage amplifier has a gain of 28 dB and a noise figure of ≤1.2 dB.

[0023] 3. Impedance matching is achieved between the two-stage filters through a microstrip line, and the output end is connected to the input port of the GNSS module through a π-type attenuator.

[0024] GNSS processing module

[0025] 1. The GNSS processing module is based on the Huada Beidou TAU1312A chip and supports BDS B1 / B2, GPS L1 / L2, GLONASS G1 / G2, or Galileo multi-system dual-frequency signal resolution.

[0026] 2. The positioning data output interface is a UART protocol, the baud rate can be configured to 9600-115200 bps, the positioning accuracy is ≤1 cm (in RTK mode), and the cold start time is ≤30 seconds.

[0027] Power supply system

[0028] 1. The main power supply circuit stabilizes the external input voltage (4.5-5.5V) to 3.3V through a MIC5203 linear voltage regulator, with a maximum output current of 500 mA and a voltage drop of ≤0.3V.

[0029] 2. The backup power supply circuit is composed of a 33000 μF farad capacitor, which is connected in parallel with the main power supply through a diode switching circuit and can maintain a 3.3V output for at least 15 minutes when the main power supply is disconnected. The capacitor charging loop is connected in series with a 10Ω current limiting resistor.

[0030] Modular interface assembly

[0031] 1. The modular interface assembly includes a 12-pin multi-pin plug-in one and a 10-pin multi-pin plug-in two, which are integrated on both sides of the module.

[0032] 2.12-pin plug-in pin definition includes: 5V power input (1 pin), GNSS data output (TX / RX each 5, 6 pin), 1PPS pulse signal (3 pin), power ground (11, 12 pin), the remaining pin is a reserved configuration interface.

[0033] 3.10-pin plug-in is used for expanding peripheral connection, supporting I2C, SPI and other communication protocols.

[0034] 4. The plug-in adopts gold-plated contacts, plug-in life ≥5000 times, contact resistance ≤20mΩ, the shell and the PCB ground plane are connected by multi-point welding to realize electromagnetic shielding.

[0035] Mechanical structure

[0036] PCB design: four-layer PCB structure (thickness 1mm), the layered layout is as follows:

[0037] Top layer: RF combining circuit and antenna unit;

[0038] First intermediate layer: power supply layer;

[0039] Second intermediate layer: ground layer;

[0040] Bottom layer: GNSS module and signal processing link.

[0041] Shielding design: the RF combining circuit area is covered with an aluminum alloy shield (thickness 0.5mm), which is connected to the PCB ground plane through multi-point grounding, and the shielding effectiveness is ≥40dB.

[0042] Compared with the prior art, the unmanned aerial vehicle high-precision positioning module based on the printed four-arm spiral antenna has the following beneficial effects:

[0043] 1. Through the cooperative design of the dual-frequency four-arm spiral antenna and the multi-stage RF circuit, the signal receiving sensitivity and the anti-multipath interference ability are significantly improved.

[0044] 2. The LTCC hybrid coupler and the high-efficiency filter amplification circuit are adopted, which reduces the circuit complexity and power consumption, and at the same time improves the signal SNR.

[0045] 3. Through the seamless switching design of the main and backup power supply, the continuous working ability of the module under the condition of power fluctuation or temporary power failure is ensured.

[0046] 4. The modular interface design simplifies system integration, improves installation efficiency and reliability.

[0047] 5. The overall structure is compact, suitable for space-limited application scenarios such as unmanned aerial vehicles, and has good environmental adaptability and anti-interference ability. BRIEF DESCRIPTION OF DRAWINGS

[0048] Figure 1 Antenna feed network (show four feed points and microstrip line matching structure);

[0049] Figure 2 Structure diagram of four-arm spiral antenna unit;

[0050] Figure 3 Top view structure diagram of positioning module;

[0051] Figure 4 Side view structure diagram of positioning module;

[0052] Figure 5 Bottom view structure diagram of positioning module;

[0053] Figure 6 Dynamic positioning test data chart (carrier signal-to-noise ratio).

[0054] In the figure: 1, radiator; 101, spiral arm; 2, support ring; 3, FR4 substrate; 301, positioning hole; 4, feed point; 5, grounding point; 6, multi-pin plug one; 7, multi-pin plug two. DETAILED DESCRIPTION

[0055] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0056] It should be noted that, unless otherwise specified, all technical and scientific terms used in the present application have the same meaning as generally understood by those skilled in the art to which the present application belongs.

[0057] I. Substrate processing and spiral arm manufacturing

[0058] An FR4 epoxy resin substrate (dielectric constant 4.4, thickness 1 mm) is selected, the surface is covered with copper with a thickness of 35 μm, a four-arm spiral structure is manufactured on the substrate through a photoetching process, the spiral arm width is 2 mm, the pitch is 2 mm, a chemical gold plating process is used to perform surface treatment on the spiral arm, the gold plating layer thickness is ≥0.2 μm, conductor loss is reduced; the support ring material is polytetrafluoroethylene (PTFE), the antenna is wrapped around the surface thereof (thickness 2 mm, dielectric constant 2.2); antenna performance testing, in a microwave darkroom, the antenna gain is tested as follows: L1 frequency band (1575.42 MHz) gain ≥4.5 dBi, L2 frequency band (1227.60 MHz) gain ≥3.8 dBi; axial ratio test results: axial ratio ≤3 dB at an elevation angle of 30°, half-power beam width ≥85°.

[0059] II. Hybrid coupler welding and debugging

[0060] Two LTCC 3dB hybrid couplers (model DLTC16-3DB) are soldered to the top layer of the PCB, and the input ends are connected to the four feed points of the antenna respectively; HC14F03 3dB hybrid couplers are used to combine two orthogonal signals, and the output ends are connected to the first amplifier through 50Ω microstrip lines; the port standing wave ratio of the combining circuit is tested by a vector network analyzer (VNA), and the length of the microstrip line is adjusted to make the standing wave ratio ≤1.5. The filter amplifier link is built, and the LTCC coupler output end is soldered with a first-stage amplifier CKRF3509MM34, the supply voltage is 3.3V, and the gain is 20dB; the input end of the first-stage TA1621A band-pass filter (center frequency 1575.42MHz, bandwidth 20MHz) is connected in series with a π-type matching network; the output end of the second-stage SF9030 band-pass filter (center frequency 1227.60MHz, bandwidth 24MHz) is connected to the second-stage amplifier SGL0622Z through a π-type attenuator (attenuation 3dB); the link gain is verified using a spectrum analyzer: the total gain of the L1 frequency band is ≥45dB, the total gain of the L2 frequency band is ≥42dB, and the out-of-band rejection is ≥40dB@100MHz offset.

[0061] Three, four-layer PCB design and shielding structure installation

[0062] PCB layer design, four-layer board structure (total thickness 1mm), top layer: RF signal layer (copper thickness 35μm), antenna and RF circuit layout; second layer: power layer (3.3V plane); third layer: ground layer (complete ground plane); bottom layer: digital signal layer, GNSS module and interface circuit layout. The RF trace uses a coplanar waveguide design, with a line width of 0.3mm and a ground plane spacing of 0.2mm.

[0063] Shielding cover installation, aluminum alloy shielding cover (thickness 0.5mm) covers the RF circuit area (size 21mm×21mm); the shielding cover is connected to the PCB ground plane through SMT pads on the four sides, with a ground spacing of ≤5mm; test shielding effectiveness: within the 1-2GHz frequency band, the signal attenuation before and after shielding is ≥40dB.

[0064] Four, power supply system and interface integration

[0065] Main and backup power supply circuits are soldered, the MIC5203 linear voltage regulator input end is connected to the 5V pin of the 10-pin plug, and the output end is connected in parallel with a 33000μF farad capacitor; the SS34 Schottky diode (forward voltage drop 0.3V) is used in the diode switching circuit, which automatically switches to the backup power supply when the main power supply is disconnected; test power supply switching response time: ≤10μs, backup power supply endurance time ≥10 minutes (GNS).

[0066] The modular interface assembly 12-pin connector (model HR12-10R) is welded to the bottom layer of the PCB, and the pin definitions are as follows: Pin1: 5V power input; Pin4: 1PPS pulse signal; Pin5-6: GNSS_TX / GNSS_RX; pin2-3, Pin7-10: reserved configuration interface; Pin10-12: power ground.

[0067] The 10-pin connector (model HR10-8R) expands the peripheral interface, supports 5V / 2A power supply and I2C communication.

[0068] Five, whole machine assembly and environmental test

[0069] The mechanical structure assembly embeds the four-layer PCB and the shielding cover into the aluminum alloy shell (size 67.7mmx68mmx16mm), uses M2 screws to fix the PCB and the shell, the screw torque is 0.6N·m, and the structural rigidity is ensured. The environmental adaptability verification high temperature test: the positioning accuracy deviation is less than or equal to 2cm under the condition of 85℃ environment for 8 hours; the low temperature test: the cold start time is less than or equal to 45 seconds at-40℃, and the positioning data output has no packet loss; the humidity test: the antenna gain decreases by less than or equal to 0.5dBi under the condition of 95%RH.

[0070] The anti-interference performance test applies a-30dBm interference signal (frequency range 1-1.6GHz) in an electromagnetic compatibility (EMC) darkroom; the test result: the positioning error is less than or equal to 5cm, and the GNSS signal loss rate is less than or equal to 1%. The positioning accuracy verification static test: using the RTK reference station in an open field, the module static positioning accuracy is less than or equal to 1cm (1sigma); the dynamic test: the unmanned aerial vehicle flies at a speed of 10m / s, and the dynamic positioning accuracy is less than or equal to 2cm (3sigma); the multipath suppression test: the positioning error is reduced by 60% compared with the traditional module near the reflecting wall (distance 2m).

[0071] In all the schemes mentioned above, although the embodiments of the utility model have been shown and described, it can be understood by those skilled in the art that various changes, modifications, replacements and variations can be made to these embodiments without departing from the principles and spirits of the utility model, and the scope of the utility model is defined by the appended claims and their equivalents.

Claims

1. A high-precision positioning module for unmanned aerial vehicles based on printed four-arm helical antennas, characterized by, The application relates to a GNSS (Global Navigation Satellite System) module, which comprises the following parts: a four-arm helical antenna unit for receiving satellite navigation signals of L1 and L2 frequency bands; a radio frequency combining circuit connected with the four-arm helical antenna unit, which comprises two hybrid couplers I and one hybrid coupler II, and is used for realizing impedance matching and combined transmission of double-frequency signals; a signal processing link which comprises a first-stage low-noise amplifier, a first-stage filter, a second-stage filter and a second-stage amplifier in sequence, and is used for realizing low-noise amplification and frequency band separation filtering of the combined signals; a GNSS processing module connected with the output end of the signal processing link, and used for analyzing the double-frequency signals and outputting high-precision positioning data; a power supply system which comprises a main power supply circuit and a backup power supply circuit, wherein the main power supply circuit is used for stabilizing an external input voltage to a required voltage through a linear voltage stabilizer, and the backup power supply circuit is composed of a capacitor and is connected in parallel with the main power supply circuit through a diode switching circuit; a modular interface assembly which comprises a multi-pin plug-in unit I used for power supply and data communication and a multi-pin plug-in unit II used for extending peripheral connection, and is integrated on two sides of a module respectively.

2. The high-precision positioning module based on printed four-arm spiral antenna for unmanned aerial vehicle according to claim 1, characterized in that, The radiator of the four-arm helical antenna unit is made of gold-plated copper, spiral arms are printed on a FPC board (flexible circuit board), surround the supporting ring, and the supporting ring is welded on an FR4 substrate, spiral arms are kept at a certain interval, and the antenna realizes multi-frequency band resonance through a four-feed-point feeding structure.

3. The high-precision positioning module for unmanned aerial vehicles based on printed four-arm spiral antennas according to claim 1, characterized in that, In the radio frequency combining circuit, the two hybrid couplers I are connected with the quadrature feeding ports of the four-arm helical antenna respectively, and the output ends of the four-arm helical antenna are combined into a single radio frequency signal through the hybrid coupler II.

4. The high-precision positioning module for unmanned aerial vehicles based on printed four-arm spiral antennas according to claim 1, characterized in that, The first-stage filter and the second-stage filter of the signal processing link are both band-pass filters, and impedance matching is realized between the two filters through a microstrip line.

5. The high-precision positioning module for unmanned aerial vehicles based on printed four-arm spiral antennas according to claim 1, characterized in that, The GNSS processing module is used for solving double-frequency signals of BDS B1 / B2, GPS L1 / L2, GLONASS G1 / G2 or Galileo satellite systems, and a positioning data output interface is a digital interface with a configurable baud rate.

6. The high-precision positioning module for unmanned aerial vehicles based on printed four-arm spiral antennas according to claim 1, characterized in that, The pins of the multi-pin plug-in unit I include power input pins, GNSS data output pins, pulse signal pins and power ground pins, and the rest pins are reserved configuration interfaces.

7. The high-precision positioning module for unmanned aerial vehicles based on printed four-arm spiral antennas according to claim 1, characterized in that, The module comprises a multi-layer PCB board, which comprises a top-layer PCB board, a first intermediate layer, a second intermediate layer and a bottom-layer PCB board from top to bottom, wherein, the radio frequency combining circuit and the antenna unit are installed on the top-layer PCB board, the power supply system is installed on the first intermediate layer, the GNSS module and the signal processing link are installed on the bottom-layer PCB board, and the second intermediate layer is a grounding layer.

8. The high-precision positioning module for unmanned aerial vehicles based on printed four-arm spiral antennas according to claim 1, characterized in that, The output end of the second-stage amplifier of the signal processing link is connected with the input port of the GNSS module through a type attenuation circuit or an attenuation component.

9. The high-precision positioning module for unmanned aerial vehicles based on printed four-arm spiral antennas according to claim 2, characterized in that, The radiator of the four-arm helical antenna unit is supported by a supporting ring, which is used for reducing the influence of environmental humidity on the antenna performance and keeping a certain structural strength.

10. The high-precision positioning module for unmanned aerial vehicles based on printed four-arm spiral antennas according to claim 1, characterized in that, The multi-pin plug-in unit of the modular interface assembly adopts gold-plated contacts.

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