A dual frequency antenna array module with automatic gain adjustment

Abstract

This utility model discloses an automatically gain-adjustable dual-frequency antenna array module, relating to the field of satellite navigation antenna technology. It includes an antenna array module, a dual-frequency anti-interference RF module, and a power supply module. The antenna array module is a four-element circular array that receives BeiDou BDS-B3, B1C, and B2b frequency signals. The dual-frequency anti-interference RF module integrates an automatic gain control unit with an RF1947 chip as its core. It acquires intermediate frequency signal power through an ADC, and the FPGA generates adjustment commands based on preset thresholds to achieve closed-loop automatic gain adjustment within the range of 15~25dB. Simultaneously, it compensates for amplitude and phase deviations through software configuration. The power supply module adopts a cascaded design to provide stable power supply. Each module has independent compartments and features tri-proof and heat dissipation designs. This utility model achieves multi-frequency signal compatibility reception, automatically adapts to signal strength changes, and has strong environmental adaptability and structural reliability. It can be widely used in BeiDou navigation-related equipment to improve navigation accuracy and stability.

Description

Technical Field

[0001] This utility model belongs to the field of satellite navigation antenna technology, and in particular relates to a dual-frequency antenna array module with automatic gain adjustment. Background Technology

[0002] With the widespread application of the BeiDou Navigation Satellite System, satellite navigation antennas, as the core component for signal reception, directly affect navigation accuracy and stability.

[0003] Currently, existing navigation antennas have limited frequency adaptability. Most antennas only support single-frequency or narrow-range dual-frequency reception, and cannot simultaneously support multiple frequency signals from BeiDou BDS-B3, B1C, and B2b. This results in limited signal coverage, making it difficult to meet navigation needs in complex scenarios. Furthermore, the gain adjustment flexibility of existing navigation antennas is insufficient. Traditional antennas often have fixed gains or are manually adjustable, failing to adapt to changes in satellite signal strength and easily leading to signal oversaturation or loss of weak signals. Secondly, existing navigation antennas suffer from poor multi-channel consistency. Multi-element antennas exhibit high amplitude and phase imbalances in their channels, affecting the effectiveness of space-time adaptive anti-interference processing and reducing navigation and positioning accuracy. Additionally, their environmental adaptability is insufficient. The dielectric constant of the dielectric material is prone to drift under temperature variations, leading to antenna performance degradation. Moreover, most antennas have weak tri-proof capabilities, making them difficult to adapt to harsh working environments.

[0004] To address the aforementioned technical problems, this utility model proposes a dual-frequency antenna array module with automatic gain adjustment. By optimizing the antenna structure, integrating an automatic gain adjustment unit, and enhancing environmental adaptability design, the signal reception capability, stability, and reliability of the antenna are improved. Summary of the Invention

[0005] The purpose of this invention is to provide an automatically adjustable dual-frequency antenna array module to solve the problems of limited frequency adaptability, insufficient gain adjustment flexibility, poor multi-channel consistency, and insufficient environmental adaptability of existing navigation antennas.

[0006] This utility model achieves the above objectives through the following technical solutions: it includes an antenna array module, a dual-frequency anti-interference radio frequency module, and a power supply module. The antenna array module is a four-element circular array structure, with the four antenna elements arranged in a square nested layout. It is used to receive right-hand circularly polarized satellite signals from BeiDou BDS-B3, B1C, and B2b frequencies. The beam coverage range is azimuth 0~360° and elevation 5~90°. The dual-band anti-interference RF module includes four B3 RF input interfaces, one B1 / B2b RF input interface, and one B1 / B2b / B3 combined RF output interface. The dual-band anti-interference RF module also integrates an automatic gain control unit. The automatic gain control unit uses the RF1947 anti-interference RF chip and configures the gain through the SPI interface. The gain control range is 15~25dB. Combined with intermediate frequency signal power acquisition and preset threshold, it realizes closed-loop automatic gain adjustment of dual-band signals. The antenna array module is connected to the dual-band anti-interference radio frequency module via an MCX connector.

[0007] Furthermore, the power module input is compatible with DC 18~36V voltage, and the output provides DC 5V±2.5% voltage to power each module; the preset thresholds are low threshold -85dBm and high threshold -55dBm.

[0008] Furthermore, the axial gain of each antenna element in the antenna array module is not less than 1.5dB, the gain is not less than -8.5dB when the elevation angle is 20°, the normal axial ratio is not greater than 3dB, and the standing wave ratio is not greater than 2; the element spacing of the four-element circular array is 1 / 2 of the wavelength of the B3 frequency point, and it is made of MC-15 microwave dielectric material.

[0009] Furthermore, the microwave dielectric material has a frequency temperature coefficient of 0±15ppm / ℃, and its dielectric constant deviation is no greater than 0.0143 in an environment of -45℃ to 65℃. Frequency compensation ensures stable performance across the entire temperature range.

[0010] Furthermore, the dual-band anti-interference RF module also includes a low-noise amplification unit, a filtering unit, and a down-conversion unit; the low-noise amplification unit uses two cascaded X33 low-noise amplifier chips, with matching structures between the stages and between the stages and the filtering unit; the filtering unit includes a B3 frequency surface acoustic wave (SAW) filter and a dual-band compatible LC intermediate frequency (IF) filter, with the center frequency of the B3 SAW filter being 1268.52MHz; the down-conversion unit is integrated into the RF1947 chip, down-converting the dual-band RF signal to a 46.52MHz IF signal.

[0011] Furthermore, the total gain of the low-noise amplifier unit is not less than 33dB, and the noise figure is not greater than 0.55dB; the out-of-band rejection of the B3 surface acoustic wave filter at key frequencies is not less than 40dB, the center frequency of the LC intermediate frequency filter is 46.52MHz, the 3dB bandwidth is not less than ±10.23MHz, and the out-of-band rejection is not less than 55dB@f0±23MHz.

[0012] Furthermore, the gain feedback adjustment subunit of the automatic gain control unit acquires the intermediate frequency signal power through the ADC chip, with the sampling clock frequency being twice the intermediate frequency, and transmits it to the FPGA chip after filtering.

[0013] Furthermore, the FPGA chip generates a gain adjustment command based on the power threshold, with a gain adjustment step size of 2dB. This command is written to the RF1947 chip via the SPI interface to achieve closed-loop automatic adjustment.

[0014] Furthermore, the FPGA chip acquires amplitude and phase data for each radio frequency channel.

[0015] Furthermore, after calculating the difference, a compensation value within the range of ±1dB is generated. Through software configuration, the amplitude imbalance is no greater than ±1dB and the phase imbalance is no greater than ±10°.

[0016] Furthermore, the antenna array module, dual-band anti-interference RF module, and power supply module adopt an independent cavity structure and are isolated by metal ribs; the connection end between the antenna array module and the dual-band anti-interference RF module is equipped with an aluminum alloy fixing baffle to prevent the connector from falling off under vibration; the shell of the dual-band anti-interference RF module is made of 5A06 rust-proof aluminum, and the surface is treated with conductive oxidation and fluoropolyurethane paint spraying, and the internal printed circuit board is coated with acrylic three-proof paint to meet the requirements of temperature resistance and three-proof.

[0017] Furthermore, the power module uses an ETA3451 DC-DC chip cascaded with a BL8073 LDO chip; the core chip in the dual-band anti-interference RF module is attached to the aluminum alloy cover plate through a thermal pad, and passive heat dissipation is achieved through the housing.

[0018] Furthermore, the power module has a conversion efficiency of no less than 85% under rated load; and the maximum operating temperature of the core chip in the dual-frequency anti-interference RF module does not exceed 88.4℃ when the ambient temperature is 65℃.

[0019] Beneficial effects: This utility model is reasonably designed and has the following beneficial effects: 1. In this utility model solution, it can simultaneously receive BeiDou BDS-B3, B1C and B2b frequency signals, with strong dual-frequency compatibility, wide signal reception coverage, and adaptability to the multi-frequency reception requirements in complex navigation scenarios. 2. In this utility model solution, closed-loop control through ADC acquisition, FPGA processing, and RF1947 configuration enables automated gain adjustment within the range of 15~25dB, adapting to satellite signals of different strengths, avoiding signal oversaturation or loss, and improving reception stability. 3. In this utility model solution, amplitude and phase deviation compensation is achieved through FPGA software configuration, multi-channel consistency is realized, the space-time adaptive anti-interference processing effect is significantly improved, and navigation and positioning accuracy is guaranteed; 4. In this utility model, microwave dielectric materials and temperature compensation design are adopted, and the dielectric constant deviation is small in the environment of -45℃~65℃. Combined with the three-proof coating and temperature-resistant structure design, it can adapt to harsh environments such as humid heat, salt spray, and vibration. 5. In this utility model, the independent cavity and metal partition design reduce electromagnetic interference, the aluminum alloy fixing baffle prevents the connector from falling off, and the power supply cascade design ensures stable power supply, thereby improving the overall continuous working capability of the equipment. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the present invention. Detailed Implementation

[0021] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present utility model. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Example

[0022] 1. Overall structural assembly The dual-band antenna array module with automatic gain adjustment is assembled from top to bottom as follows: antenna array module, dual-band anti-interference RF module, and power supply module. The three are fixed together with bolts, with overall dimensions of Φ130×65mm and tolerance ±1mm. Each module adopts an independent cavity structure, with metal ribs 15mm high, 2mm thick, and 30mm apart between the cavities to achieve electromagnetic isolation and reduce signal interference between modules.

[0023] 2. Antenna Array Module 2.1 Array element design: The element spacing of the four-element circular array is set to 11.8cm, which corresponds to half the wavelength of the BDS-B3 frequency point 1268.52MHz. Each antenna element is a λ / 4 monopole structure with an element length of 5.9cm and a diameter of 3mm. The feed point is 1.5cm from the top of the element, and the nesting depth is 5mm to ensure minimal coupling interference between elements. 2.2 Material Selection: MC-15 microwave dielectric material is used to fabricate the antenna array. The frequency temperature coefficient of this material is 0±15ppm / ℃, the dielectric constant deviation is 0.0143 at -45℃ and 0.0101 at 65℃. 2.3 Temperature Compensation: Frequency compensation parameters are configured through the 0x08 register of the FPGA chip to correct frequency drift caused by temperature changes in real time, ensuring stable antenna performance across the entire temperature range.

[0024] 3. Dual-band anti-interference radio frequency module 3.1 Interface Configuration: The four B3 RF input interfaces, one B1 / B2b RF input interface, and one B1 / B2b / B3 combined RF output interface all use MCX connectors with a insertion and extraction force of ≥5N to ensure connection reliability. 3.2 Low-noise amplifier unit: Two stages of X33 low-noise amplifier chips are cascaded, with a 100pF matching capacitor and a 2nH matching inductor connected in series between the stages. A 50Ω matching resistor is connected in series between the LNA and the filter unit. The measured total gain is 33.5dB and the noise figure is 0.52dB. 3.3 Filtering Unit: The B3 frequency SAW filter uses a device with a center frequency of 1268.52MHz. The measured out-of-band rejection at 1227.52MHz is 42dB, and the out-of-band rejection at 1309.52MHz is 58dB. The LC intermediate frequency filter adopts a π-type topology structure, consisting of 3 filter network sections with an inductance of 10μH and a capacitance of 1.1nF. The measured 3dB bandwidth is ±10.5MHz, and the out-of-band rejection at f0±23MHz is 57dB. 3.4 Downconversion Unit: The RF1947 anti-interference RF chip is configured with the local oscillator frequency through the SPI interface, and downconverts the BDS-B3, B1C and B2b RF signals to 46.52MHz intermediate frequency signals respectively, with channel isolation ≥60dB; 3.5 Automatic Gain Control Unit: The ADC chip selected is MXT2401, with a sampling clock frequency of 93.2MHz, which is twice the intermediate frequency of 46.52MHz. The sampling accuracy is 16 bits, and a moving average filtering algorithm with a window size of 16 is used to process the power data to reduce noise interference. The FPGA chip used is BQ7K325T, with a preset low power threshold of -85dBm and a high power threshold of -55dBm. When the power of the acquired intermediate frequency signal is lower than -85dBm, a gain increase command is generated; when it is higher than -55dBm, a gain decrease command is generated, with a gain adjustment step of 2dB. The SPI communication uses an 8-bit data bit, 1-bit stop bit, and no parity bit format. The 8-bit binary gain value is written to the RF1947 chip through register address 0x03 to achieve closed-loop automatic adjustment with an adjustment response time ≤100μs. 3.6 Amplitude and Phase Calibration: The FPGA chip acquires amplitude and phase data of four RF channels through the TP1-TP4 test points at the intermediate frequency output terminal. Taking channel 1 as the reference, it calculates the amplitude and phase differences between the other channels and the reference channel, generates compensation values ​​within the range of ±1dB, and writes 16-bit binary compensation data through registers 0x10 and 0x11. The measured amplitude imbalance is ≤±0.8dB and the phase imbalance is ≤±8°.

[0025] 4. Power Module The power module uses an ETA3451 DC-DC chip and a BL8073 LDO chip cascaded together. The ETA3451 chip is equipped with a 1μH power inductor, a 10μF input capacitor and a 22μF output capacitor, which converts the DC18~36V input voltage to DC3.6V. The BL8073 chip converts the DC3.6V to a DC5V±2.5% output voltage with an output ripple ≤50mV. The measured conversion efficiency under a 1A rated load is 86.2%, which meets the power supply requirements of each module.

[0026] 5. Structural and protective implementation details 5.1 Fixing Structure: The connection end between the antenna array module and the dual-band anti-interference RF module is equipped with an aluminum alloy fixing baffle. The baffle is 5mm away from the MCX connector and is fixed with M3 screws to prevent the connector from falling off under vibration. 5.2 Housing treatment: The housing of the dual-band anti-interference RF module is made of 5A06 rust-proof aluminum. After the surface is treated with rainbow conductive oxidation, it is sprayed with fluoropolyurethane paint, which has good corrosion resistance. 5.3 Conformal coating: Except for connectors, all internal printed circuit boards are coated with acrylic conformal coating with a thickness of 30-50μm. The coating is uniform and free of missed spots or runs. It has been verified by damp heat, salt spray and mold tests to meet the requirements for use in harsh environments. 5.4 Heat Dissipation Design: Thermal pads (thermal conductivity 5W / m・K, thickness 0.5mm) are attached to the surfaces of the FPGA chip and RF1947 chip. The thermal pads are tightly attached to the aluminum alloy cover plate (heat dissipation area 10cm², thickness 3mm). Passive heat dissipation is achieved through the heat dissipation path of chip, thermal pad, cover plate, and shell. At an ambient temperature of 65℃, the measured temperature of the FPGA chip is 85.3℃ and the temperature of the RF1947 chip is 83.7℃, both not exceeding 88.4℃.

[0027] It will be apparent to those skilled in the art that this invention is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or essential characteristics of this invention. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of this invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within this invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0028] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A dual-band antenna array module with automatic gain adjustment, comprising an antenna array module, a dual-band anti-interference radio frequency module, and a power supply module, characterized in that: The antenna array module is a four-element circular array structure. The four antenna elements are arranged in a square nested layout. It is used to receive right-hand circularly polarized satellite signals from BeiDou BDS-B3, B1C and B2b frequencies. The beam coverage range is azimuth 0~360° and elevation 5~90°. The dual-band anti-interference RF module includes four B3 RF input interfaces, one B1 / B2b RF input interface, and one B1 / B2b / B3 combined RF output interface. The dual-band anti-interference RF module also integrates an automatic gain control unit. The automatic gain control unit uses the RF1947 anti-interference RF chip and configures the gain through the SPI interface. The gain control range is 15~25dB. Combined with intermediate frequency signal power acquisition and preset threshold, it realizes closed-loop automatic gain adjustment of dual-band signals. The antenna array module is connected to the dual-band anti-interference radio frequency module via an MCX connector.

2. The dual-band antenna array module with automatic gain adjustment according to claim 1, characterized in that: The axial gain of each antenna element in the antenna array module is not less than 1.5dB, the gain is not less than -8.5dB when the elevation angle is 20°, the normal axial ratio is not greater than 3dB, and the standing wave ratio is not greater than 2. The element spacing of the four-element circular array is 1 / 2 of the wavelength of the B3 frequency point, and it is made of MC-15 microwave dielectric material.

3. The dual-band antenna array module with automatic gain adjustment according to claim 1, characterized in that: The dual-band anti-interference RF module also includes a low-noise amplification unit, a filtering unit, and a down-conversion unit. The low-noise amplification unit uses two cascaded X33 low-noise amplifier chips, with matching structures between the stages and between the stages and the filtering unit. The filtering unit includes a B3 frequency surface acoustic wave (SAW) filter and a dual-band compatible LC intermediate frequency (IF) filter, with the center frequency of the B3 SAW filter being 1268.52MHz. The down-conversion unit is integrated into the RF1947 chip, which down-converts the dual-band RF signal to a 46.52MHz IF signal.

4. The dual-band antenna array module with automatic gain adjustment according to claim 1, characterized in that: The gain feedback adjustment subunit of the automatic gain control unit collects intermediate frequency signal power through an ADC chip. The sampling clock frequency is twice the intermediate frequency, and the signal is transmitted to the FPGA chip after filtering.

5. The dual-band antenna array module with automatic gain adjustment according to claim 4, characterized in that: The FPGA chip collects amplitude and phase data for each radio frequency channel.

6. The dual-band antenna array module with automatic gain adjustment according to claim 1, characterized in that: The antenna array module, dual-band anti-interference RF module, and power module adopt an independent cavity structure and are isolated by metal ribs. The connection end between the antenna array module and the dual-band anti-interference RF module is equipped with an aluminum alloy fixing baffle to prevent the connector from falling off under vibration. The shell of the dual-band anti-interference RF module is made of 5A06 rust-proof aluminum, and the surface is treated with conductive oxidation and fluoropolyurethane paint spraying. The internal printed circuit board is coated with acrylic three-proof paint to meet the requirements of temperature resistance and three-proof.

7. The dual-band antenna array module with automatic gain adjustment according to claim 1, characterized in that: The power module uses an ETA3451 DC-DC chip and a BL8073 LDO chip cascaded together; the core chip in the dual-band anti-interference RF module is attached to the aluminum alloy cover plate through a thermal pad, and passive heat dissipation is achieved through the shell.

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