Anti-interference antenna supporting high-precision differential Beidou satellite navigation

Abstract

The invention belongs to the technical field of satellite navigation, and particularly relates to an anti-interference antenna supporting high-precision differential Beidou satellite navigation. Comprising three Beidou B1 / B3 double-frequency high-precision navigation antenna array elements which are arranged in a straight line and four Beidou single B3 frequency band navigation antenna array elements which are arranged in a rectangular shape; wherein the two Beidou B1 / B3 double-frequency high-precision navigation antenna array elements located at the two ends and the four Beidou mono-B3-frequency-band navigation antenna array elements located at the two ends are arranged in an equilateral hexagon shape. The Beidou B1 / B3 double-frequency high-precision navigation antenna array element located in the middle is located at the center of the equilateral hexagon.

Description

Technical Field

[0001] The present invention belongs to the field of satellite navigation technology, and in particular relates to an anti-interference antenna supporting high-precision differential Beidou satellite navigation. Background Art

[0002] The altitude of the navigation satellite orbit from the earth's surface is about 20,000 kilometers, and the satellite payload is limited, so the satellite signal transmission power cannot be too large. These factors result in the satellite signal power received on the ground being quite weak. The landing power of my country's Beidou satellite navigation signal is about -125dBm to -133dBm, which is even at least 20dB lower than the environmental thermal noise. In the process of signal reception, it will be subject to various interferences, which greatly reduces the positioning accuracy and even causes the back-end receiver to lose lock and lose the positioning position.

[0003] Therefore, studying the layout of Beidou satellite navigation anti-interference antenna array to enhance the anti-interference capability of the entire satellite navigation receiving system is an inevitable requirement for navigation and positioning functions under extremely harsh frequency environment conditions. Summary of the invention

[0004] The purpose of the present invention is to propose an anti-interference antenna that supports high-precision differential Beidou satellite navigation, which is composed of 7-element anti-interference antenna arrays composed of 4 B3 array elements and 3 B3 / B1 dual-frequency differential array elements arranged in an equidistant hexagon, so as to realize Beidou B3 frequency band anti-interference signal reception and B3 / B1 dual-frequency high-precision navigation signal reception.

[0005] The technical solution of the present invention:

[0006] An anti-interference antenna supporting high-precision differential Beidou satellite navigation, comprising: three Beidou B1 / B3 dual-frequency high-precision navigation antenna array elements arranged in a straight line and four Beidou single B3 frequency band navigation antenna array elements arranged in a rectangular shape;

[0007] The two Beidou B1 / B3 dual-frequency high-precision navigation antenna array elements and four Beidou single B3 frequency band navigation antenna array elements at both ends are arranged in an equilateral hexagon.

[0008] Furthermore, the Beidou B1 / B3 dual-frequency high-precision navigation antenna array element in the middle is located at the center of the equilateral hexagon. When the main power supply 28V of the antenna is powered off, the anti-interference function is lost. At this time, the receiver can power the array element through the RF input port 5V to achieve high-precision positioning. The array element is located at the symmetrical center of the array, with small pattern distortion, high phase center stability, and high positioning accuracy.

[0009] Furthermore, the six sides of the equilateral hexagon are divided into three groups, each group is parallel to each other;

[0010] The interior angles of an equilateral hexagon are 70°, 145°, 145°, 70°, 145°, and 145°.

[0011] Furthermore, the Beidou B1 / B3 dual-frequency high-precision navigation antenna array element includes: two concentric diamond antenna units, which serve as B1 and B3 receiving antennas respectively, and the two frequency band radiation patches share the same aperture, achieving size reduction while ensuring the radiation characteristics.

[0012] The Beidou single B3-band navigation antenna array element includes a diamond-shaped antenna unit.

[0013] Furthermore, the rhombus antenna units are all electric wall cavity microstrip antennas;

[0014] The electric wall cavity microstrip antenna includes a radiation patch and a metal floor connected by an SMA connector, wherein the cross-section of the metal floor is a flat U-shape. The electric wall cavity formed by the floor reduces the size of the array element, reduces the back radiation, reduces the mutual coupling between the array elements after the array is arranged, and improves the radiation efficiency.

[0015] Furthermore, the B3 single-frequency antenna adopts the working mode of equal-amplitude 90° phase difference double-probe feeding circular polarization;

[0016] The central rhombus antenna unit in the Beidou B1 / B3 dual-frequency high-precision navigation antenna array element is the B1 frequency point, and the outer ring-shaped rhombus antenna unit is the B3 frequency point. The rhombus antenna unit working at the B3 frequency point also serves as the electrical wall of the rhombus antenna unit working at the B1 frequency point. Each rhombus antenna unit is fed by a dual probe with equal amplitude and 90° phase difference. On the basis of realizing circular polarization, the bandwidth is expanded and the array element size is reduced to a certain extent.

[0017] Furthermore, the anti-interference antenna further includes: a radio frequency front-end module;

[0018] The RF front-end module and the antenna array element are connected through the MCX RF connector, which improves the integration, reduces the transmission loss between the array element and the RF module, and reduces the system noise coefficient. The RF front-end module is used to filter, amplify and down-convert the signal received by the antenna array element and then transmit it to the back-end anti-interference digital processing module.

[0019] Furthermore, in the anti-interference working mode, the B3 receiving paths of the four Beidou B3 single-frequency arrays and the B3 receiving paths of the three Beidou B3 / B1 dual-frequency arrays constitute a 7-element anti-interference receiving channel, and the received real satellite signals and interference signals in the B3 frequency band are sent to the RF front end for down-conversion to the intermediate frequency. The anti-interference digital processing module at the back end performs a secondary frequency conversion on the intermediate frequency signal to the baseband, and then calculates the antenna array factor weights, and adjusts the antenna array radiation pattern so that its zero point position is aligned with the interference direction, thereby suppressing the interference signal. Finally, the baseband signal after anti-interference processing is secondary-converted back to the B3 frequency band, and after being combined with the B1 path signal of the B3 / B1-2 high-precision antenna in the middle, the power is divided into 5 outputs for use by each navigation terminal.

[0020] Furthermore, in the high-precision differential navigation working mode, the dual-frequency B1 / B3 dual-frequency high-precision navigation antenna array elements located at the left and right ends are used to receive B3 and B1 frequency band navigation signals. The RF channels of the two arrays are independently designed with separate cavities and serve as redundant backup for each other, which improves the reliability of the receiving system. The signals received by each are processed by the RF front-end low-noise amplifier and filtering unit and then combined and output to the back-end receiver for differential positioning solution.

[0021] Furthermore, the RF front-end module uses the CA-RF1947X four-channel RF chip for down-conversion. It has extremely high linearity and low noise characteristics, and achieves high channel isolation, improves integration, and reduces overall power consumption.

[0022] Beneficial effects of the present invention:

[0023] The present invention is designed with comprehensive consideration of multiple aspects such as antenna array pattern optimization, radio frequency channel index optimization, and redundancy backup of the whole machine functional interface. The antenna pattern achieves spatial coverage of 10° to 90° in pitch and omnidirectional in the horizontal direction, with gain ≮-8dBi, axial ratio ≯6dB, front-to-back ratio ≮15dB, and phase center consistency of the high-precision array reaching centimeter-level indicators. The entire radio frequency circuit is divided into different units and physically divided into cavities. Each circuit is independent of each other and does not affect each other. High isolation is achieved between channels, and the 7B3 anti-interference channel has good channel consistency. In conjunction with the anti-interference digital processing unit, it can achieve good single-interference and multi-interference resistance capabilities in actual tests. In addition, the external radio frequency interface is a redundancy backup, which can provide multiple navigation signal receiving terminals with B3 pure signals that have undergone anti-interference processing and high-precision B3 / B1 signals that support differential positioning. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Anti-interference antenna array layout diagram;

[0025] Figure 2 RF front-end module appearance diagram;

[0026] Figure 3 Schematic diagram of the front circuit layout of the RF front-end module;

[0027] Figure 4 Schematic diagram of the circuit layout on the back of the RF front-end module;

[0028] Figure 5 Schematic diagram of the electric wall cavity structure antenna;

[0029] Figure 6 B3 array gain pattern;

[0030] Figure 7 It is the B3 / B1 array-B3 gain pattern;

[0031] Figure 8 This is the B3 / B1 array-B1 gain pattern;

[0032] Fig. 9 It is the three-dimensional phase pattern of B3 / B1 array-B3;

[0033] Fig.10 It is the three-dimensional phase pattern of B3 / B1 array-B1;

[0034] Fig.11 Schematic diagram of anti-interference antenna array and RF front-end processing;

[0035] Fig.12 Design schematics for the RF front-end module link;

[0036] Fig.13 Design a schematic diagram for the B3 channel link;

[0037] Fig.14 Schematic diagram of B3 / B1 high-precision channel link design. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] The present invention discloses an anti-interference antenna array and RF front-end processing method supporting high-precision differential Beidou satellite navigation function, which is composed of 4 B3 array elements and 3 B3 / B1 dual-frequency differential array elements arranged in an equidistant hexagon to form a 7-element anti-interference antenna array, realizing Beidou B3 frequency band anti-interference signal reception and B3 / B1 dual-frequency high-precision navigation signal reception. Figure 1 shown.

[0040] The antenna array element of the present invention adopts Figure 5 The electric wall technology shown in the figure folds up a part of the edge of the ordinary microstrip antenna floor to form an electric wall cavity microstrip antenna. As the floor size is reduced, the overall size of the antenna is also greatly reduced, and the antenna array element is embedded in the antenna array plane. It can improve the mutual coupling between the elements of the anti-interference array, achieve better anti-interference ability, and maintain good radiation performance.

[0041] The B3 single-frequency array element adopts the working mode of equal-amplitude 90° phase difference double-probe feeding circular polarization, which has a wider axial ratio bandwidth than the single-probe feeding mode. Its simulated gain pattern is shown in Figure 6 shown.

[0042] The B3 / B1 dual-frequency array element is a diamond-shaped single-layer coplanar dual-frequency dual-circularly polarized microstrip antenna. The B1 and B3 frequency band radiation patches adopt a compact coplanar structure design, which effectively realizes the integration and simplified structure design of the dual-frequency antenna unit. The central diamond radiation patch is the B1 frequency point, and the outer ring diamond patch is the B3 frequency point. The B3 radiation patch also serves as the electric wall of B1. The dual patches also use equal-amplitude 90° phase difference dual probe feeding. The simulated gain pattern is shown as follows: Figure 7-Figure 8 As shown in the figure, the phase center of the dual-frequency antenna is simulated and analyzed at the same time. The phase pattern of B3 and B1 is shown in Fig. 9 and Fig.10 As shown in the microwave darkroom radiation pattern measurement, the B3 / B1 patch maintains a high degree of consistency in the phase center. Both the simulation and measurement of the phase center consistency are centimeter-level indicators, meeting the requirements of high-precision dual-frequency differential positioning.

[0043] In the anti-interference working mode, the B3 receiving paths of the four Beidou B3 single-frequency arrays and the B3 receiving paths of the three Beidou B3 / B1 dual-frequency arrays constitute a 7-element anti-interference receiving channel, and the received real satellite signals and interference signals in the B3 frequency band are sent to the RF front end for down-conversion to the intermediate frequency. The anti-interference digital processing module at the back end performs a secondary frequency conversion on the intermediate frequency signal to the baseband, calculates the antenna array factor weights, and adjusts the antenna array radiation pattern so that its zero point position is aligned with the interference direction, thereby suppressing the interference signal. Finally, the baseband signal after anti-interference processing is secondary-converted back to the B3 frequency band, and is combined with the B1 path signal of the B3 / B1-2 high-precision antenna in the middle and then output after power division.

[0044] In the high-precision differential navigation working mode, the dual-frequency B3 / B1-1 and B3 / B1-3 antenna arrays located at the left and right ends are used to receive B3 and B1 frequency band navigation signals. The RF channels of the two arrays are independently designed with separate cavities and serve as redundant backup for each other. After being processed by the RF front-end low-noise amplifier and filtering unit, they are combined and output to the back-end receiver for differential positioning solution.

[0045] The RF front-end module is used to pre-process satellite signals. It filters, amplifies, and down-converts the satellite signals received by the antenna array to obtain an intermediate frequency signal with good amplitude and phase consistency, and sends it to the back-end anti-interference processing unit to filter out interference signals. The RF front-end uses the CA-RF1947X down-conversion chip produced by Hebei Jinghe Electronics. The chip has a high degree of integration, and the gain can be adjusted in steps of 1dB within the range of 0dB to 30dB. It has extremely high linearity and low noise characteristics. In addition, the 7-way B3 anti-interference channel structure is independently divided into cavities, with good electromagnetic shielding effect and high isolation characteristics between channels.

[0046] The RF front-end module disclosed in the present invention includes circuit units such as low noise amplifier, down-conversion, filtering and power combining, and is connected to the antenna element through a RF MCX connector, with a highly integrated design. Figure 2 As shown. The RF front-end module amplifies, filters, and down-converts the B3-band satellite navigation signal received by the 7-element anti-interference antenna array through a low-noise amplifier, generates an intermediate frequency analog signal (46.52MHz), and sends it to the anti-interference digital processing unit. The anti-interference digital processing unit digitally down-converts the input 7-channel intermediate frequency signal to the baseband, performs space-time joint adaptive processing, and controls the synthesized antenna pattern by adjusting the weights of each channel, so that the synthesized antenna pattern simultaneously produces nulls in each interference direction, thereby effectively suppressing the B3-band interference signal. The anti-interference digital processing unit converts the pure signal after the interference is filtered out from the baseband back to the intermediate frequency (46.52MHz), and then sends it to the RF front end for further up-conversion to the B3 frequency and outputs it to the navigation terminal for use.

[0047] At the same time, the RF front end receives the Beidou navigation B3 band and B1 band signals from the B3 / B1-1 and B3 / B1-3 dual-frequency high-precision antenna arrays at the two sharp ends of the array, and after low-noise amplification and filter processing, they are independently output to the user receiver. The RF channels of the two arrays are independent of each other and serve as redundant backups for each other. The schematic diagram of the overall anti-interference antenna array and RF front-end processing system is shown in the figure below. Fig.11 For detailed link design, see Figure 12 to Figure 14 .

[0048] The RF front-end structure can be divided into three parts: cavity, cover and circuit. Figure 3 and Figure 4 . The cavity and cover are made of magnesium alloy AZ31B, which has the advantages of light weight, low density, good electrical and thermal conductivity, and are CNC machined as a whole. They are subjected to corresponding heat treatment and conductive oxidation treatment to ensure sufficient strength and corrosion resistance. The cover is connected to the cavity by screws to form a closed cavity space, filling the gaps caused by the structural accuracy, and ensuring good shielding performance of the overall circuit. The circuit board is fixed in the structural cavity by screws, and each group of circuit boards with different functions is shielded and isolated by partition walls to enhance signal isolation. The circuit board fits tightly with the bottom of the structural cavity, so that the heat of the circuit can be quickly transferred to the outside of the structural cavity.

[0049] The RF front end has the capabilities of up / down conversion, anti-burning, output power adjustment, and out-of-band signal suppression. It is used to realize satellite signal preprocessing. The Beidou B3 band satellite signal received by the antenna array is filtered, amplified, and down-converted and then transmitted to the back-end anti-interference digital processing module. The interference-filtered intermediate frequency signal output by the anti-interference digital processing module is then up-converted to the B3 frequency and combined with the B1 signal that has only been filtered and amplified for power splitting output.

[0050] Figure 3 and Figure 4 The layout of each functional circuit unit is intuitively shown in the figure.

[0051] In the circuit layout, 1 represents 4-channel B3 anti-interference low-noise amplifier units and 3-channel differential navigation signal channel B3 low-noise amplifier units, 2 represents the anti-interference and high-precision switching unit, 3 represents the 3-channel differential navigation signal channel B1 low-noise amplifier unit, 4 represents the B3 down-conversion unit, 5 represents the combining power division unit, 6 represents the power supply and self-test unit, 7 represents the power division unit, 8 represents the combining unit, 9 represents the B3 up-conversion unit, and 10 represents the B3 filtering unit.

[0052] When the RF front-end processing module is powered by an external 5V power supply, it supports the combined output of Beidou B3 anti-interference signal and B1 signal, and the combined output of Beidou differential high-precision B3 / B1 dual-frequency signal; when the external power supply fails, the high-precision RF channel can be fed with coaxial 5V DC through the navigation receiver terminal. In this working mode, the RF channel does not perform anti-interference processing.

[0053] The RF front-end processing module B3 down-conversion processing uses two CA-RF1947X four-channel RF chips to replace the down-conversion circuit composed of discrete devices. It integrates low noise amplifier (LNA), mixer (Mixer), intermediate frequency amplifier (IF AMP), voltage-controlled oscillator (VCO), phase-locked loop (PLL), sampling clock circuit and low voltage drop linear regulator (LDO) and other circuits. It can operate at 1.1GHz~1.7GHz and 2.3GHz~2.7GHz frequency, covering all current navigation frequency bands. The chip supports built-in local oscillator and external local oscillator mode, which is convenient for the expansion and application of multiple chips. After the two chips are expanded, 7-channel anti-interference processing function can be realized. The 7-way B3 RF signal processing channel has extremely high linearity and low noise characteristics, and achieves high channel isolation.

[0054] The four RF input channels of the CA-RF1947X RF chip of the RF front-end processing module are all differential inputs, connected to the low noise amplifier unit through a balun, and the four IF outputs are also differential, using a balun output, connected to an LC IF filter and then output. The internal parameter configuration of the CA-RF1947X RF chip is controlled by a single-chip microcomputer, and the chip uses a TCXO crystal oscillator as a reference signal. The local oscillator signal output by the chip is divided into two channels through a power divider, one for the chip itself and the other as a local oscillator for up-conversion.

[0055] The dual-path differential high-precision channels of the RF front-end processing module are independent of each other and serve as backup for each other, thereby improving the reliability of the entire receiving system.

[0056] The above is only a specific embodiment of the present invention, and the present invention is described in detail. The unexplained part is a conventional technology. However, the protection scope of the present invention is not limited to this. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. The protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. An anti-interference antenna supporting high-precision differential Beidou satellite navigation, characterized in that: The antenna comprises: three Beidou B1 / B3 dual-frequency high-precision navigation antenna array elements arranged in a straight line and four Beidou single B3 frequency band navigation antenna array elements arranged in a rectangular shape; The two Beidou B1 / B3 dual-frequency high-precision navigation antenna array elements and four Beidou single B3 frequency band navigation antenna array elements at both ends are arranged in an equilateral hexagon.

2. The anti-interference antenna according to claim 1, characterized in that: The Beidou B1 / B3 dual-frequency high-precision navigation antenna array element located in the middle is located in the center of the equilateral hexagon.

3. The anti-interference antenna according to claim 2, characterized in that: The six sides of an equilateral hexagon are divided into three groups, each group is parallel to each other; The interior angles of an equilateral hexagon are 70°, 145°, 145°, 70°, 145°, and 145°.

4. The anti-interference antenna according to claim 3, characterized in that: The Beidou B1 / B3 dual-frequency high-precision navigation antenna array element includes: two concentric diamond-shaped antenna units, which serve as B1 and B3 receiving antennas; The Beidou single B3-band navigation antenna array element includes a diamond-shaped antenna unit.

5. The anti-interference antenna according to claim 4, characterized in that: The rhombus antenna elements are all electric wall cavity microstrip antennas; The electric wall cavity microstrip antenna comprises a radiation patch and a metal floor connected by an SMA connector, wherein the cross-section of the metal floor is a flat U-shape.

6. The anti-interference antenna according to claim 5, characterized in that: The B3 single-frequency antenna adopts the working mode of equal amplitude 90° phase difference double probe feeding circular polarization; The central diamond antenna unit in the Beidou B1 / B3 dual-frequency high-precision navigation antenna array element is the B1 frequency point, and the outer ring-shaped diamond antenna unit is the B3 frequency point. The diamond antenna unit working at the B3 frequency point also serves as the electrical wall of the diamond antenna unit working at the B1 frequency point. Each diamond antenna unit is fed by equal-amplitude 90° phase difference dual probes.

7. The anti-interference antenna according to claim 6, characterized in that: The anti-interference antenna also includes: a radio frequency front-end module; The RF front-end module and the antenna array element are connected through the MCX RF connector, which is used to filter, amplify and down-convert the signals received by the antenna array element and then transmit them to the back-end anti-interference digital processing module.

8. The anti-interference antenna according to claim 7, characterized in that: In the anti-interference working mode, the B3 receiving paths of the four Beidou B3 single-frequency arrays and the B3 receiving paths of the three Beidou B3 / B1 dual-frequency arrays constitute a 7-element anti-interference receiving channel, and the received real satellite signals and interference signals in the B3 frequency band are sent to the RF front end for down-conversion to the intermediate frequency. The anti-interference digital processing module at the back end performs interference identification after secondary conversion of the intermediate frequency signal to the baseband, and performs weighted processing on the received signal through the antenna array factor weight solution to adjust the zero point of the directional diagram to align the interference direction, thereby suppressing the interference signal. Finally, the baseband signal after anti-interference processing is secondary converted back to the B3 frequency band, and after being combined with the B1 path signal of the B3 / B1-2 high-precision antenna in the middle, the power is divided into five output paths for use by each navigation terminal.

9. The anti-interference antenna according to claim 8, characterized in that: In the high-precision differential navigation working mode, the dual-frequency B1 / B3 dual-frequency high-precision navigation antenna array elements located at the left and right ends are used to receive B3 and B1 frequency band navigation signals. The RF channels of the two arrays are independently designed with separate cavities to provide mutual redundancy backup. The signals received by each are processed by the RF front-end low-noise amplifier and filtering unit, and then combined and divided into four output paths to the back-end receivers for differential positioning solution.

10. The anti-interference antenna according to claim 7, characterized in that: The RF front-end module uses the CA-RF1947X four-channel RF chip for down-conversion.

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