A diversity transmission system in a vehicular radio frequency communication

Abstract

The present application relates to the technical field of wireless communication, in particular to a diversity transmitting system in vehicle-mounted radio frequency communication. The present application aims to solve the problem of large transmitting power loss caused by long cable transmission in the prior art, and the problem of difficult non-interference relay amplification under frequency division duplex system. The system comprises a vehicle-mounted transceiving communication module, a radio frequency cable, a directional coupler, a transceiving integrated antenna, a power amplifier and a diversity transmitting antenna arranged at the antenna end. The directional coupler splits the input signal into two paths: the main path is transmitted by the transceiving integrated antenna through the straight-through port for normal transceiving; the auxiliary path is split by the coupling port and then enhanced by the power amplifier before being synchronously transmitted by the diversity transmitting antenna. The isolation port of the directional coupler is connected to a resistor. The present application utilizes the splitting and one-way isolation characteristics of the directional coupler to effectively compensate for the line loss and realize spatial diversity enhancement of the transmitting end without affecting the receiving sensitivity of the main path.

Description

Technical Field

[0001] This invention relates to the field of wireless communication technology, specifically to a diversity transmission system for vehicle-mounted radio frequency communication. Background Technology

[0002] In the RF link design of intelligent connected vehicles, passive antennas are typically used to simplify the transmit / receive switching design. However, due to vehicle structural limitations, there is often a considerable distance between the antenna and the communication module, requiring a long-distance cable connection. In the field of communication, signal loss increases with cable length. To ensure communication quality, effectively compensating for line loss has become an industry goal. Existing line loss compensation schemes (such as GNSS satellite communication) mostly focus on amplification at the receiver end. However, in systems involving simultaneous transmit and receive operations, especially under Frequency Division Duplex (FDD) systems, because transmit and receive actions occur simultaneously and cannot be easily switched via a switch like in Time Division Duplex systems, effective relay amplification schemes have been lacking. This results in the inability to effectively compensate for the transmitter signal strength in scenarios requiring large amounts of data uploads, such as Level 4 and above autonomous driving, easily leading to problems such as decreased upload speed and shortened communication distance.

[0003] Relevant patent documents retrieved: The document, published in China (CN107465432A) on December 12, 2017, discloses a method for connecting a diversity antenna to a main transmit / receive path. By changing the connection logic between the radio frequency front-end module (FEM) and the radio frequency switch, it optimizes the user experience of mobile terminals such as mobile phones in a specific frequency band.

[0004] The document, published in China (CN109347509A) on February 15, 2019, discloses a method, apparatus, and active antenna for gain compensation of an active antenna. It uses a temperature sensor to detect the ambient temperature and adjusts the attenuation value of the radio frequency attenuator according to a preset rule to achieve temperature compensation for the gain of the active antenna.

[0005] The prior art represented by the aforementioned documents has at least the following unresolved technical problems or defects: While the aforementioned patent document CN107465432A involves adjustments to the main and diversity paths, its primary purpose is to optimize antenna performance and reduce mobile phone power consumption in handheld mode. Essentially, it involves path switching between antennas without providing effective power enhancement methods to address energy loss caused by cable transmission. This solution cannot improve the terminal's equivalent radiated power and, in scenarios with severe long-distance cable loss, still cannot solve the problems of weak signal and low upload speed.

[0006] While the aforementioned patent document CN109347509A achieves a certain degree of gain compensation, it primarily focuses on dynamic adjustment in response to environmental factors. This solution mainly targets signal enhancement or balancing at the receiver. When handling Frequency Division Duplex (FDD) systems, the lack of design to isolate the transmission and reception paths makes it difficult to directly perform relay amplification at the transmitter without interfering with the sensitivity of the receiving link.

[0007] Therefore, there is still an urgent need in the field for a new type of vehicle-mounted radio frequency communication diversity transmission system that can combine signal distribution logic with active power enhancement, enabling real-time and dynamic enhancement of transmission power through diversity antennas without interfering with the normal transmission and reception of the main channel, thereby overcoming the problems of insufficient transmission power and reduced communication quality caused by cable loss and standard limitations in the prior art. Summary of the Invention

[0008] In order to solve at least one of the above-mentioned technical problems existing in the prior art, the present invention provides a diversity transmission system for vehicle radio frequency communication.

[0009] To achieve the above objectives, the technical solution of the present invention is as follows: This invention provides a diversity transmission system for vehicle-mounted radio frequency communication, comprising: a vehicle-mounted transceiver communication module, installed inside the vehicle, for generating raw radio frequency signals and processing externally received signals; An RF cable is connected to the vehicle-mounted transceiver module for transmitting the raw RF signal; A directional coupler is disposed near one end of the antenna and connected to the radio frequency cable. The directional coupler includes an input port, a through port, a coupling port, and an isolation port. A transceiver antenna is connected to the through port; A power amplifier, the input of which is connected to the coupling port; A diversity transmit antenna is connected to the output of the power amplifier; And a resistor, connected to the isolation port and grounded; The input port is connected to the radio frequency cable to receive the original radio frequency signal. The through port and the input port form the main transmission path, and the coupling port, the power amplifier, and the diversity transmit antenna form the auxiliary enhancement path.

[0010] Furthermore, the directional coupler is configured to split the original radio frequency signal entering the input port into two paths using an electromagnetic coupling structure; The first signal is configured to be transmitted to the transceiver antenna via a through-port. The second signal is configured to be shunt to the power amplifier via the coupling port.

[0011] Furthermore, the coupling degree of the directional coupler is configured to be -5dB to -30dB, so as to provide an excitation level that can be effectively amplified for the second signal while ensuring the strength of the first signal.

[0012] Furthermore, the power amplifier is configured to amplify the second signal to compensate for the transmission loss of the original radio frequency signal in the radio frequency cable, and transmit it through the diversity transmit antenna and the transceiver antenna.

[0013] Furthermore, the spatial distance between the diversity transmitting antenna and the transceiver antenna is maintained at more than 70mm to prevent mutual interference between the two antennas.

[0014] Furthermore, the system supports Frequency Division Duplex (FDD) standard, with the input port and through port configured as bidirectional transceiver ports, and the coupling port configured as a unidirectional transmit port.

[0015] Furthermore, when the transceiver antenna receives an external radio frequency signal, the external radio frequency signal is transmitted to the input port via the through port; The directional coupler is configured to use the directional characteristics of the directional coupler and the resistor connected to the isolation port to prevent external radio frequency signals from entering the coupling port and power amplifier, so as to maintain the receiving sensitivity.

[0016] Furthermore, the resistor is used to absorb reflected waves generated inside the directional coupler due to impedance mismatch, thereby improving the isolation between the through port and the coupling port.

[0017] Furthermore, the system is configured to convert one RF cable transmission channel into an architecture of two spatial diversity transmissions and one main path reception.

[0018] Compared with the prior art, the present invention has the following beneficial effects: This invention utilizes a four-port directional coupler at the antenna end to split the radio frequency signal transmitted over long-distance cables. The main path remains passively direct to ensure reliable transmission and reception, while the auxiliary path is amplified twice by a power amplifier before being transmitted through a diversity antenna. This design effectively compensates for power loss caused by long-distance transmission without altering the vehicle's original communication modules and cable layout, significantly improving the equivalent radiated power and signal coverage of the uplink.

[0019] This invention addresses the simultaneous transmission and reception characteristics of frequency division duplex (FDM) systems by utilizing the directional coupling principle of a directional coupler and impedance matching design of the isolation port to achieve isolation between the transmit enhancement path and the receive path. When the main antenna receives a weak downlink signal, the high isolation effectively prevents the received signal from leaking into the power amplifier branch, thus avoiding any impact on the receiver sensitivity.

[0020] This invention achieves transmit diversity gain by distributing the main antenna and diversity transmit antennas. Simultaneous transmission from both antennas effectively addresses the fading effect caused by high-speed vehicle movement, reduces the dropout rate in communication blind spots, and provides stable and reliable assurance for Level 4 autonomous vehicles. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the diversity transmission system in vehicle-mounted radio frequency communication provided by the present invention. Detailed Implementation

[0022] The technical solution of the present invention will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are not all embodiments of the present invention. All other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0023] It should be noted that, unless otherwise specifically stated, the relative arrangement and numerical expressions of the components and steps described in these embodiments should not be construed as limiting the scope of the invention.

[0024] The following description of exemplary embodiments is merely illustrative and is not intended to limit the invention or its application or use in any way. Techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail herein, but where applicable, such techniques, methods, and apparatus should be considered part of this specification.

[0025] Example 1 like Figure 1 As shown, this embodiment provides a diversity transmission system for vehicle-mounted radio frequency communication. The system mainly consists of the following parts: The signal source end is the vehicle-mounted transceiver module. Installed inside the vehicle, this module is responsible for processing communication protocols and generating the raw radio frequency signal to be transmitted, as well as processing received external signals.

[0026] The signal transmission medium is the radio frequency cable that connects the vehicle's transceiver communication module to the external antenna. Due to vehicle size limitations (such as L4 level logistics vehicles), this cable is usually several meters or even more than ten meters long, resulting in physical signal loss during the process.

[0027] The core control unit is the directional coupler located near the antenna end. This directional coupler has four ports: an input port, a through port, a coupling port, and an isolation port. The specific connection relationships of the four ports are as follows: Input port: Connects to the RF cable and is used to receive signals output by the vehicle transceiver module and transmitted via the cable.

[0028] Straight-through port: Connects to the transceiver antenna.

[0029] Coupled port: Connected to the input of the power amplifier.

[0030] Isolation port: Connected to a 50-ohm resistor, the other end of which is grounded.

[0031] Finally, there is the signal enhancement and transmission end, which includes a power amplifier connected after the directional coupler and a diversity transmit antenna connected to the output of the power amplifier.

[0032] When the system is in transmit mode, the signal output by the vehicle-mounted transceiver module is transmitted via cable to the input port of the directional coupler at the antenna end. At this time, the directional coupler uses its internal electromagnetic coupling structure to split the total signal entering the input port: Main transmit path (straight path): Most signals are output from the straight-through port and directly fed into the transceiver antenna. The transceiver antenna performs conventional wireless signal transmission tasks.

[0033] Auxiliary Enhancement Path (Coupled Path): A small portion of the signal is shunted from the coupling port through coupling. In this embodiment, the coupling degree of the directional coupler is preferably designed to be between -10dB and -15dB. However, depending on the actual usage scenario, such as vehicle size, cable material, and actual loss value of the wiring harness, the applicable range of coupling degree can be extended to -5dB to -30dB. The selection of this parameter range is based on the following: if the coupling is too small, the insertion loss of the main path will be too large, affecting the communication distance of the main antenna; if the coupling is too large, the shunted signal will be too weak and difficult to be effectively processed by subsequent circuits. Therefore, the preferred range of -10dB to -15dB achieves a balance between low loss in the direct path and effective excitation in the coupled path, while the wide range of -5dB to -30dB covers the adaptation requirements under different vehicle models and cable lengths.

[0034] The shunted signal enters the power amplifier. The power amplifier amplifies this shunted signal with targeted gain, the gain of which depends on the cable length and losses; in this embodiment, it is preferably configured in the range of 20dB to 25dB. Similarly, depending on the actual usage scenario and the actual losses of the cable, the amplification range can be extended to 5dB to 35dB. Although the shunted signal has low energy, it carries a complete signal envelope and phase information. After processing by the amplifier, its output power can reach a preset high power level, thereby offsetting the losses previously generated in the cable.

[0035] The amplified high-power signal is transmitted through the diversity transmit antenna. The distance between the tiered antenna and the main transceiver antenna must be maintained at more than 70mm to prevent the two antennas from intertwining, which would affect the system's transmission and reception performance. At this point, the system forms two synchronously transmitted signals in space, achieving spatial diversity at the transmitter.

[0036] This solution offers unique advantages in processing received signals, especially under FDD standards: when the RF signal emitted by an external base station or terminal is captured by the transceiver antenna, the signal enters the through port of the directional coupler. At this point, the directional characteristics of the directional coupler play a crucial role: the signal is guided from the through port to the input port. Because the isolation port is connected to a 50-ohm resistor, this resistor effectively absorbs reflected waves that may arise due to impedance mismatch, thereby improving the isolation between the through port and the coupling port.

[0037] This makes it extremely difficult for the received signal to enter the coupling port. This also means that the diversity transmit tributary and power amplifier are transparent to the receive link. This ensures that the received signal does not experience additional power attenuation due to the addition of a diversity transmit tributary during transmission to the vehicle transceiver module, thus maintaining the system's original receiving sensitivity.

[0038] For FDD (Frequency Division Duplex) communication, since the transmission and reception frequencies are conducted simultaneously at different frequency points, traditional amplifiers cannot be directly connected in series on the main path shared by the transmitter and receiver, otherwise it will interfere with the received signal.

[0039] This embodiment utilizes a unique arrangement of directional couplers, defining the input port and through port as bidirectional transmit / receive ports, while defining the coupled port as a unidirectional transmit port. This design leverages the unidirectional coupling characteristic of the directional coupler to separate the transmit enhancement path from the receive protection path. This allows the system to maintain basic communication through the integrated transmit / receive antenna while simultaneously providing enhanced transmit power through the diversity transmit antenna in FDD mode where transmission and reception occur simultaneously, thus addressing the industry's pain point of line loss compensation.

[0040] The above specific embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A diversity transmission system for vehicle-mounted radio frequency communication, characterized in that, include: The vehicle-mounted transceiver module is installed inside the vehicle and is used to generate raw radio frequency signals and process externally received signals. An RF cable is connected to the vehicle-mounted transceiver module for transmitting the raw RF signal; A directional coupler is disposed near one end of the antenna and connected to the radio frequency cable. The directional coupler includes an input port, a through port, a coupling port, and an isolation port. A transceiver antenna is connected to the through port; A power amplifier, the input of which is connected to the coupling port; A diversity transmit antenna is connected to the output of the power amplifier; And a resistor, connected to the isolation port and grounded; The input port is connected to the radio frequency cable to receive the original radio frequency signal. The through port and the input port form the main transmission path, and the coupling port, the power amplifier, and the diversity transmit antenna form the auxiliary enhancement path.

2. The diversity transmission system in vehicle-mounted radio frequency communication according to claim 1, characterized in that: The directional coupler is configured to split the original radio frequency signal entering the input port into two paths using an electromagnetic coupling structure; The first signal is configured to be transmitted to the transceiver antenna via a through-port. The second signal is configured to be shunt to the power amplifier via the coupling port.

3. The diversity transmission system in vehicle-mounted radio frequency communication according to claim 2, characterized in that: The coupling of the directional coupler is configured to be between -5dB and -30dB, so as to provide an excitation level that can be effectively amplified for the second signal while ensuring the strength of the first signal.

4. The diversity transmission system in vehicle-mounted radio frequency communication according to claim 1, characterized in that: The power amplifier is configured to amplify the second signal so that the amplified output power compensates for the transmission loss of the original radio frequency signal in the radio frequency cable, and transmits it through the diversity transmit antenna and the transceiver antenna.

5. A diversity transmission system for vehicle-mounted radio frequency communication according to claim 1, characterized in that: The spatial distance between the diversity transmitting antenna and the transceiver antenna is maintained at more than 70mm to prevent mutual interference between the two antennas.

6. The diversity transmission system in vehicle-mounted radio frequency communication according to claim 1, characterized in that: The system supports Frequency Division Duplex (FDD) standard. The input port and through port are configured as bidirectional transceiver ports, and the coupling port is configured as a unidirectional transmit port.

7. A diversity transmission system for vehicle-mounted radio frequency communication according to claim 6, characterized in that: When the transceiver antenna receives an external radio frequency signal, the external radio frequency signal is transmitted to the input port via the through port; The directional coupler is configured to use the directional characteristics of the directional coupler and the resistor connected to the isolation port to prevent external radio frequency signals from entering the coupling port and power amplifier, so as to maintain the receiving sensitivity.

8. A diversity transmission system for vehicle-mounted radio frequency communication according to claim 1, characterized in that: The resistor is used to absorb reflected waves generated inside the directional coupler due to impedance mismatch, thereby improving the isolation between the through port and the coupling port.

9. A diversity transmission system for vehicle-mounted radio frequency communication according to claim 1, characterized in that: The system is configured to convert one RF cable transmission channel into an architecture with two spatial diversity transmissions and one main path reception.

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