A dual-GNSS active antenna with anti-blocking characteristics

Abstract

The present invention discloses a dual GNSS active antenna with anti-blocking characteristics, belonging to the field of wireless communications. The antenna includes two groups of GNSS active antennas with identical structures. One group of GNSS active antennas includes a receiving antenna unit and a receiving channel for receiving circularly polarized signals. The receiving channel includes an FBAR filter, a first low-noise amplifier, a second filter, a fixed attenuator, and a second low-noise amplifier connected in sequence, for amplifying and filtering the circularly polarized signals before sending them to subsequent devices. The present invention places an FBAR filter before the low-noise amplifier at the front end of the receiving channel. Its low insertion loss characteristic minimizes its impact on the noise figure, its high power capacity prevents the high power of the transmitted signal from affecting the receiving channel, and its excellent out-of-band suppression characteristic prevents the transmitted signal from interfering with the received positioning signal, thereby making the antenna more accurate in positioning.

Description

Technical Field

[0001] The invention belongs to the field of wireless communications and relates to a dual GNSS active antenna with anti-blocking characteristics. Background Art

[0002] The Global Navigation Satellite System (GNSS), primarily including the US GPS, Russia's GLONASS, the EU's GALILEO, and China's BeiDou Navigation System (BDS), is a space-based radio navigation and positioning system that provides users with all-weather three-dimensional coordinates, velocity, and time information anywhere on Earth's surface or in near-Earth space. GNSS primarily consists of space satellites, a ground-based monitoring system, and user receivers. Space satellites broadcast their positions and timestamps via high-frequency carrier signals at a constant frequency, day and night. Upon receiving the satellite's high-frequency carrier signal, the user receiver calculates the distance to the satellite by multiplying the speed of light by the carrier's propagation time.

[0003] GNSS positioning antennas are critical components in satellite communication terminals, directly impacting overall system performance. To increase positioning accuracy, dual GNSS antennas are typically used. A dual-antenna GNSS receiver uses two antennas, each spaced a fixed distance apart, to receive satellite signals. The receiver's hardware and software fuse the satellite information received from both antennas to provide accurate position, velocity, heading, and other information.

[0004] The miniaturization and integration of satellite communication terminals has necessitated the miniaturization of GNSS antennas. Common GNSS antenna types include quadrifilar helical antennas and microstrip antennas. Quadrifilar helical antennas offer the advantages of high gain and wide bandwidth, generating a hemispherical radiation pattern with a wide beam and good low-elevation gain. However, their disadvantage is their large size. Microstrip antennas, on the other hand, are compact, simple to manufacture, offer good consistency, and are easily integrated with other devices. However, their significant disadvantage is their narrow bandwidth.

[0005] The stability of the GNSS positioning antenna's phase center is also a factor that significantly affects positioning accuracy. The antenna's phase center serves as the benchmark for observation data from satellite navigation terminal receivers. Generally speaking, the apparent center of the antenna's main lobe varies across different sections of the pattern. This is because the antenna aperture varies across different sections. This means the stability of the antenna's phase center is related to the antenna's form and feeding method. The more symmetrical the antenna's structure, the greater the number of feeds, and the more uniform and symmetrical the feed points, the better the phase center stability. However, the multi-feed method complicates the feeding network and increases the number of optimization parameters. Compared to the single-feed method, the multi-feed method is less conducive to miniaturization. If the GNSS positioning antenna's phase center stability is poor—that is, the phase center's ability to fluctuate poorly with factors such as elevation angle, azimuth angle, and operating frequency—the antenna will introduce additional phase differences when receiving satellite signals from different directions, increasing the error in the measurement results.

[0006] For the design of GNSS antenna receiving channel, such as Figure 3 As shown, in order to achieve low noise performance, existing receivers usually place the low noise amplifier in the first stage when designing the receiving chain, and place the filter with large loss in the second stage to achieve a lower noise figure. However, this will increase the power of the transmitted signal and cause interference to the positioning signal. Summary of the Invention

[0007] In response to the shortcomings of existing GNSS antennas, the present invention provides a dual-GNSS active antenna with anti-blocking characteristics to solve the problems in the existing technology of GNSS antennas such as large size, unstable phase center, easy frequency deviation after processing, and transmitted signal blocking the positioning signal.

[0008] The technical solution adopted in the present invention is as follows:

[0009] A dual GNSS active antenna with anti-blocking characteristics is characterized by comprising two groups of GNSS active antennas with identical structures; the GNSS active antennas include a receiving antenna unit and a receiving channel.

[0010] The receiving antenna unit is used to receive circularly polarized signals and transmit the received circularly polarized signals to a receiving channel;

[0011] The receiving channel is used to amplify and filter the circularly polarized signal and then send it to the subsequent device; specifically, the receiving channel includes a first filter, a first low-noise amplifier, a second filter, a fixed attenuator, and a second low-noise amplifier connected in sequence; wherein the first filter is an FBAR filter.

[0012] Preferably, the receiving antenna unit comprises an antenna radiating body and a feeding network;

[0013] The feeding network adopts a four-feed-point coaxial feeding method to feed the antenna radiation body, so that the receiving antenna unit receives circularly polarized signals;

[0014] The antenna radiating body is mirror-symmetrical left and right and top and bottom, and includes a dielectric substrate, a metal floor arranged on the back of the dielectric substrate, a metal patch layer arranged on the front of the dielectric substrate, and four feeding points; the metal patch layer includes a square metal patch and four T-shaped tuning branches loaded on its four sides; the four feeding points are respectively located on the two center lines of the square metal patch, and the coaxial inner conductors of the four feeding ends of the feeding network pass through the dielectric substrate to connect the four feeding points.

[0015] Preferably, the feeding network includes a first-level 3dB bridge, a second-level 3dB bridge, a first-level 3dB bridge, and a second-level 3dB bridge;

[0016] The input end of the first-stage 3dB bridge is used to feed the input signal, the isolation end is connected in series with a 50-ohm resistor and then grounded, the first output end is connected to the input end of the first three-stage 3dB bridge, and the second output end is connected to the input end of the second-stage 3dB bridge;

[0017] The isolation end of the first three-stage 3dB bridge is connected in series with a 50-ohm resistor and then grounded, and the first output end and the second output end serve as the first feeding end and the second feeding end of the feeding network;

[0018] The isolation terminal and the second output terminal of the secondary 3dB bridge are respectively connected in series with a 50-ohm resistor and then grounded, and the first output terminal is connected to the input terminal of the second and third-stage 3dB bridge;

[0019] The isolation end of the second-third-stage 3dB bridge is connected in series with a 50-ohm resistor and then grounded, and the first output end and the second output end serve as the third feeding end and the fourth feeding end of the feeding network;

[0020] The four feeding ends form four signals with phases of 0°, 90°, 180°, and 270° and equal amplitudes, enabling the receiving antenna unit to achieve excellent circular polarization performance.

[0021] Preferably, the side length of the square metal patch is λ / 2.

[0022] Preferably, in the T-shaped tuning branch, the length of the branch parallel to its loading edge ranges from λ / 4 to λ / 2.

[0023] The principles and beneficial effects of the present invention are as follows:

[0024] The present invention provides a dual GNSS active antenna with anti-blocking characteristics. Firstly, two groups of GNSS antennas are used for positioning, thereby increasing positioning accuracy.

[0025] Secondly, in the design of the receiving channel, since the GNSS antenna is used for a ground communication terminal, the existing receiving channel design has the defect that the transmitted signal power is large and interferes with the positioning signal; therefore, in order to prevent the transmitted communication signal from blocking the positioning signal, the present invention places a first-stage FBAR filter in front of the low-noise amplifier at the front end of the receiving channel. The FBAR filter has a small size, high quality factor, low insertion loss, high power capacity and excellent out-of-band suppression characteristics. The low insertion loss characteristic can make it have less impact on the noise coefficient, the high power capacity characteristic can avoid the high power of the transmitted signal from affecting the receiving channel, and the excellent out-of-band suppression characteristic can avoid the transmitted signal from interfering with the received positioning signal, thereby making positioning more accurate.

[0026] In addition, in the design of the receiving antenna unit, the present invention adopts a low-profile microstrip antenna, which is easy to integrate into the terminal and realize the miniaturization of the terminal equipment; wherein, the receiving antenna unit is fed by a four-feed point coaxial feeding method, and the radiator adopts a square metal patch. The radiator and the feeding point have rotational symmetry, which ensures the stability of the phase center and the circular polarization characteristics, and at the same time can increase the axial ratio bandwidth and impedance bandwidth feeding point of the antenna; and the four sides of the square metal patch are loaded with T-shaped tuning branches, which can be debugged after processing to avoid frequency deviation caused by processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the structure of the antenna radiation body in the embodiment.

[0028] Figure 2 Schematic diagram of the feeding network in the embodiment.

[0029] Figure 3 This is a dual GNSS active antenna with anti-blocking characteristics in an embodiment.

[0030] Figure 4 : This is the standing wave simulation result of the GNSS active antenna in the embodiment.

[0031] Figure 5 : is the directional pattern simulation result of the GNSS active antenna in the embodiment.

[0032] Figure 6 ] is the axial ratio simulation result of the GNSS active antenna in the embodiment.

[0033] Explanation of the accompanying figures: 1. dielectric substrate, 2. square metal patch, 3. T-shaped tuning branch, 4. feeding point. DETAILED DESCRIPTION

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present application more clear, the technical solutions of the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. The present invention will be further described below in conjunction with the accompanying drawings.

[0035] This embodiment provides a dual GNSS active antenna with anti-blocking characteristics, the operating frequency band is 1555-1620MHz, and meets the GPS L1 band, BD B1 band, GLONASS L1 band, and GALLILEO E1 band. Figure 3 As shown, the antenna includes two groups of GNSS active antennas with the same structure; the GNSS active antennas include a receiving antenna unit and a receiving channel.

[0036] The receiving antenna unit is used to receive circularly polarized signals and transmit the received circularly polarized signals to a receiving channel.

[0037] Specifically, the receiving antenna unit includes an antenna radiation body and a feeding network.

[0038] The feeding network adopts a four-feed coaxial feeding method to feed the antenna radiation body, so that the receiving antenna unit receives circularly polarized signals with a stable phase center; the feeding network is as follows Figure 2 As shown, it includes a first-level 3dB bridge, a second-level 3dB bridge, a first-level 3dB bridge, and a second-level 3dB bridge.

[0039] Among them, the input end of the first-level 3dB bridge is used to feed the input signal, the isolation end is connected in series with a 50-ohm resistor and then grounded, the first output end is connected to the input end of the first three-level 3dB bridge, and the second output end is connected to the input end of the second-level 3dB bridge.

[0040] The isolation end of the first three-stage 3dB bridge is connected in series with a 50-ohm resistor and then grounded, and the first output end and the second output end serve as the first feeding end and the second feeding end of the feeding network.

[0041] The isolation end and the second output end of the secondary 3dB bridge are respectively connected in series with a 50-ohm resistor and then grounded, and the first output end is connected to the input end of the second tertiary 3dB bridge.

[0042] The isolation end of the second-third-stage 3dB bridge is connected in series with a 50-ohm resistor and then grounded, and the first output end and the second output end serve as the third feeding end and the fourth feeding end of the feeding network.

[0043] The four feeding ends form four signals with phases of 0°, 90°, 180°, and 270° and equal amplitudes, enabling the receiving antenna unit to achieve excellent circular polarization performance.

[0044] The antenna radiation body is as follows Figure 1 As shown, it is mirror-symmetrical left and right and up and down, including a dielectric substrate, a metal floor arranged on the back of the dielectric substrate, a metal patch layer arranged on the front of the dielectric substrate, and four feeding points; wherein the dielectric substrate adopts TP-2, has a dielectric constant of 8 and a side length of 40mm; the metal patch layer includes a square metal patch with a side length of 28mm and four T-shaped tuning branches loaded on its four sides, and the horizontal branch length of the T-shaped tuning branch is 16mm and the width is 0.2mm, and the longitudinal branch length is 0.2mm and the width is 0.16mm; the four feeding points are respectively located on the two midlines of the square metal patch and are 8mm away from the center point. The coaxial inner conductors of the four feeding ends of the feeding network pass through the dielectric substrate to connect the four feeding points.

[0045] The receiving channel is used to amplify and filter circularly polarized signals before transmitting them to subsequent devices. Specifically, the receiving channel includes a first filter, a first low-noise amplifier, a second filter, a fixed attenuator, and a second low-noise amplifier, connected in sequence. The first filter is an FBAR filter, model RSFK1575A032B2, with a typical in-band insertion loss of 1.2dB, characterized by low insertion loss, good out-of-band rejection, and compact size. The first and second low-noise amplifiers are model FW1112, with a noise figure of 0.4dB. The second filter is a SAW filter, model MS11U1G57-G3, with a typical in-band insertion loss of 1.8dB, characterized by low insertion loss, good out-of-band rejection, and compact size.

[0046] Figure 4 : This is the standing wave simulation result of the GNSS active antenna in the embodiment. It can be seen that the in-band standing wave is less than 2, and the antenna is well matched.

[0047] Figure 5 The simulation results of the directional pattern of the GNSS active antenna in the embodiment show that the maximum radiation direction of the antenna is the normal direction, the normal gain is greater than 4dB, and the directional patterns at azimuth angles of 0° and 45° are consistent, showing good radiation directivity.

[0048] Figure 6 ] is the axial ratio simulation result of the GNSS active antenna in the embodiment. It can be seen that the axial ratio is less than 3 in the range of pitch angle from -90° to 90°, and has good circularly polarized radiation characteristics.

Claims

1. A dual GNSS active antenna with anti-blocking characteristics, characterized in that: It includes two sets of GNSS active antennas with the same structure; the GNSS active antennas include a receiving antenna unit and a receiving channel; The receiving antenna unit is used to receive circularly polarized signals and transmit the received circularly polarized signals to a receiving channel; The receiving channel is used to amplify and filter the circularly polarized signal and then send it to the subsequent device; specifically, the receiving channel includes a first filter, a first low-noise amplifier, a second filter, a fixed attenuator, and a second low-noise amplifier connected in sequence; wherein the first filter is an FBAR filter; The receiving antenna unit includes an antenna radiation body and a feeding network; The feeding network adopts a four-feed-point coaxial feeding method to feed the antenna radiation body, so that the receiving antenna unit receives circularly polarized signals; The antenna radiating body is mirror-symmetrical left and right and top and bottom, and includes a dielectric substrate, a metal floor arranged on the back of the dielectric substrate, a metal patch layer arranged on the front of the dielectric substrate, and four feeding points; the metal patch layer includes a square metal patch and four T-shaped tuning branches loaded on its four sides; the four feeding points are respectively located on the two center lines of the square metal patch, and the coaxial inner conductors of the four feeding ends of the feeding network pass through the dielectric substrate to connect the four feeding points.

2. The dual GNSS active antenna with anti-blocking characteristics according to claim 1, characterized in that: The feeding network includes a primary 3dB bridge, a secondary 3dB bridge, a first tertiary 3dB bridge, and a second tertiary 3dB bridge; The input end of the first-stage 3dB bridge is used to feed the input signal, the isolation end is connected in series with a 50-ohm resistor and then grounded, the first output end is connected to the input end of the first three-stage 3dB bridge, and the second output end is connected to the input end of the second-stage 3dB bridge; The isolation end of the first three-stage 3dB bridge is connected in series with a 50-ohm resistor and then grounded, and the first output end and the second output end serve as the first feeding end and the second feeding end of the feeding network; The isolation terminal and the second output terminal of the secondary 3dB bridge are respectively connected in series with a 50-ohm resistor and then grounded, and the first output terminal is connected to the input terminal of the second and third-stage 3dB bridge; The isolation end of the second-third-stage 3dB bridge is connected in series with a 50-ohm resistor and then grounded, and the first output end and the second output end serve as the third feeding end and the fourth feeding end of the feeding network; The four feeding ends form four signals with phases of 0°, 90°, 180°, and 270° and equal amplitudes, enabling the receiving antenna unit to achieve excellent circular polarization performance.

3. The dual GNSS active antenna with anti-blocking characteristics according to claim 2, characterized in that: The side length of the square metal patch is λ / 2.

4. The dual GNSS active antenna with anti-blocking characteristics according to claim 3, characterized in that: In the T-shaped tuning branch, the length of the branch parallel to its loading edge ranges from λ / 4 to λ / 2.

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