An active phased array vehicle-mounted antenna system suitable for high-speed rail

Abstract

The present invention provides an active phased array vehicle-mounted antenna system suitable for high-speed railways, comprising: an active phased array vehicle-mounted antenna and a vehicle-mounted device; the vehicle-mounted device controls and adjusts the pitch angle of the active phased array vehicle-mounted antenna so that the main lobe of the vehicle-mounted antenna points in real time to the direction of a base station antenna. The active phased array vehicle-mounted antenna can increase the system transmission power, improve the receiving sensitivity, and enhance the signal strength along the line.

Description

Technical Field

[0001] The present invention relates to the field of communication technology, and in particular to an active phased array vehicle-mounted antenna system suitable for high-speed railways. Background Art

[0002] Enhanced Ultra High Throughput EUHT is a wireless high-speed communication technology developed by Nufront with completely independent intellectual property rights. In the EUHT high-speed rail communication system, base station equipment is installed on communication towers along the railway, and vehicle-mounted antennas are installed on the top of the train. The wireless signal forms a strip coverage along the railway. In order to increase the coverage distance, the EUHT high-speed rail vehicle-mounted antenna uses two high-gain directional antennas in front and behind. When the train is farthest from the base station antenna, the spatial path loss is the largest, and the main lobe direction of the passive vehicle-mounted antenna points to the base station antenna, which can meet the long-distance coverage scenario; when the train travels under the base station antenna, the spatial path loss is the smallest, but because the beam direction of the passive antenna is fixed, it is in the coverage range of the vehicle-mounted antenna and the base station antenna side lobe at this time, and the signal is weak and it is easy to have a black phenomenon under the tower.

[0003] In addition, because the on-board antenna is installed on the top of the train and the on-board equipment is installed in the cabinet inside the car, a long RF feeder is required to connect the antenna and the on-board equipment, which leads to large line loss, reduces the system transmission power, increases the system noise coefficient, and affects the coverage effect of the EUHT communication system. Summary of the invention

[0004] In view of this, the present invention provides an active phased array vehicle-mounted antenna system suitable for high-speed railways. By adjusting the beam elevation angle within the coverage range along the line, the antenna main lobe is pointed in the direction of the base station antenna in real time, which can improve the receiving sensitivity, improve the black spot phenomenon under the tower, and enhance the signal strength along the line.

[0005] An active phased array vehicle-mounted antenna system suitable for high-speed rail, comprising: an active phased array vehicle-mounted antenna, and vehicle-mounted equipment;

[0006] The vehicle-mounted device controls and adjusts the pitch angle of the active phased array vehicle-mounted antenna so that the main lobe of the vehicle-mounted antenna points in real time to the direction of the base station antenna;

[0007] The vehicle-mounted antenna includes a pair of directional antennas, which are orthogonal dual-polarization directional antennas; the two directional antennas are arranged in a back-to-back manner, wherein the main beam of the forward antenna points in the same direction as the front of the vehicle, and the main beam of the rear antenna points in the opposite direction;

[0008] In the pair of directional antennas, each pair of antennas consists of M rows and N columns, and M*N dual-polarization vibrators form an antenna array; wherein M and N are positive integers; the vehicle-mounted antenna includes 2*M*N TR units, and a radio frequency switch is used at the final stage of each TR unit to switch between the front and rear directional antennas, and each TR unit feeds the front and rear directional antennas respectively.

[0009] The M*N dual-polarization oscillators include a zero-degree phase oscillator, which is an antenna phase reference point, and the phase is always 0° at different elevation angles;

[0010] Remove the phase shifter in the zero-degree phase oscillator TR unit.

[0011] A vehicle-mounted device, which provides power, control signals, and inputs radio frequency signals to an active phased array vehicle-mounted antenna; the vehicle-mounted device comprises:

[0012] Power module, vehicle equipment controller, RF transceiver;

[0013] The power module is used to provide power to the vehicle-mounted antenna;

[0014] The vehicle-mounted device controller is used to provide a serial port for the active antenna, and the vehicle-mounted device sends a serial port signal through the serial port; the serial port signal includes: the vehicle-mounted device sends an antenna beam elevation angle command to the antenna end; obtains the power amplifier PA transmission power and antenna temperature data; obtains antenna version information and TR unit gain information;

[0015] The vehicle-mounted device controller is also used to send a front and rear antenna switching signal to the vehicle-mounted antenna; the front and rear antenna switching signal is used to control the TR unit to switch between the two directional antennas;

[0016] A radio frequency transceiver, used to provide radio frequency input signals to the TR units of the two directional antennas and receive wireless signals from the antenna TR units;

[0017] The transceiver control signal is used to control the operating timing of the transceiver switch, power amplifier, low noise amplifier and analog-to-digital converter of the TR unit of a pair of directional antennas;

[0018] The vehicle-mounted equipment controls the power detection circuit, controls the working timing of the analog-to-digital converter by sending and receiving control signals, and detects the output power of the power amplifier of the TR unit in the transmission slot;

[0019] A one-to-one correspondence between the vehicle-mounted antenna pitch angle command and the vehicle-mounted antenna pitch angle is preset; the vehicle-mounted device sends the pitch angle command to the vehicle-mounted antenna through the serial port, and after the vehicle-mounted antenna receives the pitch angle command, it adjusts the phase value of the TR unit inside each antenna according to the preset pitch angle command and the pitch angle correspondence, and controls the vehicle-mounted antenna to point to the corresponding angle.

[0020] Furthermore, the front and rear antenna switching signal, serial port signal, and transceiver control signal are differential signals.

[0021] The power control implementation methods of active phased array vehicle-mounted antenna systems include open-loop power control and closed-loop power control.

[0022] Beneficial effects of the technical solution of the present invention:

[0023] 1. The vehicle-mounted equipment controls the vehicle-mounted antenna to adjust the antenna beam, so that the main lobe of the vehicle-mounted antenna points to the direction of the base station antenna in real time, thereby increasing the system transmission power and reducing the system noise coefficient;

[0024] 2. Using RF switches at the end of the TR unit to switch to different antennas helps reduce the number of TR units used, power consumption and system cost;

[0025] 3. Removing the phase shifter in the zero-degree phase oscillator TR unit and reducing the number of phase shifters will help reduce costs;

[0026] 4. The vehicle-mounted equipment controls each TR unit to adjust to the specified phase and controls the antenna to point to the corresponding angle through a set of serial port commands corresponding to the beam elevation angle. This method helps to reduce the complexity of antenna use;

[0027] 5. The control signal between the vehicle-mounted equipment and the active antenna adopts differential signal transmission to enhance the anti-interference ability and driving ability.

[0028] For the above and related purposes, one or more embodiments include features that will be described in detail below and particularly pointed out in the claims. The following description and the accompanying drawings describe certain exemplary aspects in detail, and are indicative of only some of the various ways in which the principles of the various embodiments may be employed. Other benefits and novel features will become apparent as the following detailed description is considered in conjunction with the accompanying drawings, and the disclosed embodiments are intended to include all such aspects and their equivalents. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a principle diagram of the phased array antenna provided by the present invention;

[0030] Figure 2 This is an array diagram of a 3-row and 2-column active phased array antenna provided in Embodiment 1 of the present invention;

[0031] Figure 3 This is a radio frequency block diagram of a +45° polarized TR unit provided in Embodiment 1 of the present invention;

[0032] Figure 4 This is a schematic diagram of the installation of a vehicle-mounted antenna provided in Embodiment 2 of the present invention;

[0033] Figure 5is a block diagram of the hardware connection between the vehicle-mounted device and the active antenna provided in the second embodiment of the present invention;

[0034] Figure 6 is a schematic diagram of power and temperature detection provided by Embodiment 2 of the present invention;

[0035] Figure 7 It is a schematic diagram of beam adjustment of an active phased array antenna system provided by an application embodiment of the present invention;

[0036] Figure 8 It is a vertical directional diagram corresponding to different antenna beam pitch-up commands provided by an application embodiment of the present invention;

[0037] Fig. 9 It is a signal strength distribution diagram along the line after adjusting the antenna elevation angle in real time provided by an application embodiment of the present invention; DETAILED DESCRIPTION

[0038] The following description and the accompanying drawings fully illustrate specific embodiments of the present invention so that those skilled in the art can practice them. Other embodiments may include structural, logical, electrical, process and other changes. The examples represent possible changes only. Unless explicitly required, separate components and functions are optional, and the order of operation may vary. Parts and features of some embodiments may be included in or replace parts and features of other embodiments. The scope of the embodiments of the present invention includes the entire scope of the claims, and all available equivalents of the claims. In this article, these embodiments of the present invention may be represented individually or collectively by the term "invention", which is only for convenience, and if more than one invention is actually disclosed, it is not intended to automatically limit the scope of the application to any single invention or inventive concept.

[0039] According to the array antenna theory, the antenna elements form an antenna array according to the spacing d, such as Figure 1 As shown in the principle of phased array antenna, the feeding amplitude and phase of each oscillator are distributed according to a certain rule. After the oscillator radiation signals are spatially coherently superimposed, a beam with a specific direction is formed. By changing the amplitude and phase of the feeding signal according to a certain rule, the beam direction of the array antenna can be changed, thus realizing a phased array antenna.

[0040] Phased array antennas are divided into two categories: active phased array antennas and passive phased array antennas. The antenna unit of an active phased array antenna includes a transceiver unit TR (Transmit Receive). In the TR unit, the power amplifier PA (Power Amplifier) ​​and the low noise amplifier LNA (Low Noise Amplifier) ​​are located at the final stage, and the phase shifter and attenuator and other devices are located at the front stage of the TR unit. Their loss does not affect the maximum transmission power and noise factor of the active phased array antenna. There are multiple TR units in the active phased array antenna, each of which contains the final stage PA. The wireless signals transmitted by multiple PAs are coherently superimposed in space to produce a spatial power synthesis effect, which increases the maximum transmission power of the system. In addition, each TR unit contains an LNA, which reduces the noise factor of the system. The phase shifter, power divider and other devices of the passive phased array antenna are located between the antenna vibrator and the transceiver. The loss of the phase shifter and power divider affects the maximum transmission power and noise factor of the system. Therefore, compared with passive antennas, active antennas have stronger transmission signals and lower noise factors.

[0041] In comparison, active phased array antennas have more advantages in performance, so the vehicle-mounted antenna in the present invention selects active phased array antennas.

[0042] The present invention provides an active phased array vehicle-mounted antenna system suitable for high-speed railways, comprising:

[0043] Vehicle-mounted antenna;

[0044] The vehicle-mounted antenna includes a pair of directional antennas, which are orthogonal dual-polarization directional antennas; the two directional antennas are arranged in a back-to-back manner, wherein the main beam of the forward antenna points in the same direction as the front of the vehicle, and the main beam of the rear antenna points in the opposite direction;

[0045] Furthermore, in the pair of directional antennas, each pair of antennas consists of M rows and N columns, and M*N dual-polarization elements form an antenna array; wherein M and N are positive integers;

[0046] The horizontal and vertical beam widths of the array antenna with M rows and N columns satisfy the following formulas:

[0047]

[0048] Where BW H and BW V is the horizontal and vertical 3dB wave width, d H and d V are the horizontal and vertical oscillator spacings respectively, λ is the wavelength of the electromagnetic wave in the antenna working frequency band, and k is a fixed coefficient.

[0049] The vehicle-mounted antenna includes 2*M*N TR units. The final stage of each TR unit uses a radio frequency switch to switch between the front and rear directional antennas. Each TR unit feeds the front and rear directional antennas respectively.

[0050] The M*N dual-polarization oscillators include a zero-degree phase oscillator, which is an antenna phase reference point, and the phase is always 0° at different elevation angles;

[0051] Removing the phase shifter in the zero-degree phase oscillator TR unit; In the antenna array, removing the phase shifter in the zero-degree phase oscillator TR unit can avoid the scenario where the RF signal is completely disconnected at the moment of beam angle adjustment, and reducing the number of phase shifters is conducive to reducing costs.

[0052] On-board equipment, which provides power, control signals, and input RF signals to the active phased array on-board antenna;

[0053] The vehicle-mounted device controls and adjusts the pitch angle of the active phased array vehicle-mounted antenna so that the main lobe of the vehicle-mounted antenna points in real time to the direction of the base station antenna; specifically,

[0054] A one-to-one correspondence between the vehicle-mounted antenna pitch angle command and the vehicle-mounted antenna pitch angle is preset;

[0055] The vehicle-mounted device sends a pitch angle command to the vehicle-mounted antenna through the serial port. After receiving the pitch angle command, the vehicle-mounted antenna adjusts the phase value of the TR unit inside each antenna according to the preset pitch angle command and the corresponding relationship between the pitch angle, and controls the vehicle-mounted antenna to point to the corresponding angle.

[0056] The vehicle-mounted equipment includes:

[0057] Power module, vehicle equipment controller, RF transceiver;

[0058] The power module is used to provide power to the vehicle-mounted antenna;

[0059] The vehicle-mounted device controller is used to provide a serial port for the active antenna, and the vehicle-mounted device sends a serial port signal through the serial port; the serial port signal includes: the vehicle-mounted device sends an antenna beam elevation angle command to the antenna end; obtains the power amplifier PA transmission power and antenna temperature data; obtains antenna version information and TR unit gain information;

[0060] The vehicle-mounted device controller is also used to send a front and rear antenna switching signal to the vehicle-mounted antenna; the front and rear antenna switching signal is used to control the TR unit to switch between the front and rear antennas;

[0061] The RF transceiver is used to provide RF input signals to the TR unit in the vehicle-mounted antenna and receive wireless signals from the vehicle-mounted antenna; the transceiver control signal is used to control the working sequence of the transceiver switch, power amplifier, low noise amplifier and analog-to-digital converter of the two-way TR unit of a pair of directional antennas, which is synchronized with the working sequence of the RF transceiver;

[0062] The vehicle-mounted equipment controls the power detection circuit, controls the working timing of the analog-to-digital converter by sending and receiving control signals, and detects the output power of the power amplifier of the TR unit in the transmission slot.

[0063] Among them, the front and rear antenna switching signal, serial port signal, and transceiver control signal are differential signals.

[0064] Embodiment 1

[0065] In the embodiment, the vehicle-mounted antenna takes 2×2 MIMO, and the front and rear directional antennas are ±45° dual-polarized antennas as an example to illustrate the implementation method of the vehicle-mounted antenna;

[0066] The vehicle-mounted antenna includes a pair of ±45° dual-polarized directional antennas; the two polarization directions of +45 degrees and -45 degrees are orthogonal to each other, and the beam directions basically coincide. The +45-degree polarized antenna exhibits a certain beam width, and the -45-degree antenna also exhibits a certain beam width; the two directional antennas are arranged back-to-back, with the forward antenna main beam containing a +45-degree polarized beam and a -45-degree polarized beam, pointing in the same direction as the front of the vehicle, and the rear antenna main beam also containing a +45-degree polarized beam and a -45-degree polarized beam, pointing in the opposite direction.

[0067] For example, in this embodiment, an antenna array with 3 rows and 2 columns is used to realize a directional antenna with a horizontal beam width of 30° and a vertical beam width of 20°. Figure 2 As shown, the front and rear antennas are back-to-back to form a high-speed rail vehicle antenna, and the beam directions are respectively pointing forward and backward;

[0068] The vehicle-mounted antenna contains two antennas, front and rear. Each antenna is composed of 3 rows and 2 columns, with a total of 6 dual-polarization oscillators. Each dual-polarization oscillator requires 2 TR units, so each antenna requires 12 TR units. Theoretically, a vehicle-mounted antenna requires a total of 24 TR units for the front and rear antennas.

[0069] In this embodiment, the vehicle-mounted antenna includes 12 TR units, and a radio frequency switch is used at the end of each TR unit to switch between the front and rear directional antennas, and each TR unit feeds the front and rear directional antennas respectively;

[0070] Specifically, an RF switch is used at the final stage of the TR unit, and the front and rear antennas share 12 TR units. Each TR unit feeds the front and rear antennas respectively. This method can reduce the number of TR units used by half, which is beneficial to reducing costs and power consumption.

[0071] Optionally, the RF transceiver switch may be a circulator or a duplexer; the RF transceiver switch or circulator architecture is applicable to a TDD communication system, while the duplexer is applicable to an FDD communication system.

[0072] +45° polarized TR unit RF block diagram Figure 3 As shown, the -45° polarized array TR unit uses the same circuit. The RF input signal provided by the vehicle-mounted equipment is fed to each TR unit after 6 power divisions. The RF signal is input to the power amplifier PA after passing through the attenuator, phase shifter, and RF transceiver switch in each TR unit. After being amplified by the PA, it passes through the transceiver switch and finally passes through the forward and backward switching switch to feed the forward or backward antenna element.

[0073] It should be noted that the order of the attenuators, phase shifters, and RF transceiver switches in each TR unit can be reversed, and this is not limited here;

[0074] On the contrary, after the wireless signal is received by the antenna vibrator, it goes along the reverse path, is amplified by the LNA, and the 6-way signal is synthesized and transmitted to the vehicle-mounted equipment.

[0075] When the lateral distance between the base station antenna and the railway track is small, the horizontal angle of the vehicle-mounted antenna does not need to be adjusted, and only the elevation angle of the antenna beam needs to be adjusted to meet the coverage requirements. In this embodiment, the antenna is arranged in 3 rows and 2 columns to realize a phased array antenna with adjustable elevation angle and non-adjustable horizontal azimuth angle.

[0076] Specifically, the 3-row 2-column antenna array includes 6 dual-polarization oscillators, wherein the oscillators in the middle row are used as antenna phase reference points, which are zero-degree phase oscillators, and the phase of the zero-degree phase oscillators is always 0° at different elevation angles;

[0077] Removing the phase shifter in the zero-phase oscillator TR unit can save a pair of phase shifters, which is beneficial to reducing costs and network complexity. At the same time, at the moment of phase shifter adjustment, there is a signal disconnection of several hundred nanoseconds. After the phase shifter is omitted from the TR unit of the middle zero-phase oscillator, the zero-phase oscillator TR unit always remains connected at the moment of adjustment of other phase shifters, which can avoid the phenomenon of complete disconnection of the 6-way TR unit signal. In the actual test process, there is no signal interruption at the moment of beam adjustment.

[0078] Furthermore, due to the differences in gain and loss of each RF device, an attenuator is needed in the circuit to adjust the link gain so that the gains of the six TR units are consistent, ensuring that the output power of each PA is consistent and the signal amplitude of each oscillator is consistent, which is beneficial to improving the antenna directivity and signal strength.

[0079] In the embodiment of the present invention, the active antenna includes 6 TR units, each TR unit contains a PA. After the RF signal is amplified by the PA, it is radiated through the antenna element, and power synthesis is achieved after spatial coherent superposition. The synthetic gain G=10×log(N), N is the number of PAs, and 6 PAs can obtain approximately 7.8dB of gain.

[0080] According to the RF system receiving sensitivity formula:

[0081]

[0082] The lower the noise coefficient of the first-stage LNA and the smaller the loss of the connecting cable between the antenna vibrator, the smaller the system noise coefficient. When the system uses an active antenna, the first-stage LNA is located in the active antenna TR unit, and the distance between the LNA and the antenna unit is the shortest; when the system uses a passive antenna, the first-stage LNA is located in the vehicle-mounted device, and the antenna and the vehicle-mounted device are far apart, the RF cable is long, and the loss is large, so the active antenna system noise coefficient selected in the present invention is better than the passive antenna system, which can increase the system transmission power and reduce the system noise coefficient.

[0083] Embodiment 2

[0084] The present invention provides a vehicle-mounted device, which is used for controlling and adjusting the pitch angle of the active phased array vehicle-mounted antenna, so that the main lobe of the vehicle-mounted antenna points in real time to the direction of the base station antenna;

[0085] A one-to-one correspondence between the vehicle-mounted antenna pitch angle command and the vehicle-mounted antenna pitch angle is preset; the vehicle-mounted device sends the pitch angle command to the vehicle-mounted antenna through the serial port, and after the vehicle-mounted antenna receives the pitch angle command, it adjusts the phase value of the TR unit inside each antenna according to the preset pitch angle command and the pitch angle correspondence, and controls the vehicle-mounted antenna to point to the corresponding angle.

[0086] Specifically, the vehicle-mounted equipment includes:

[0087] A power module 21, an on-vehicle device controller 22, a first radio frequency transceiver 23, and a second radio frequency transceiver 24;

[0088] The power module 21 is used to provide power to the vehicle-mounted antenna; it provides power for the normal operation of the active antenna, and the voltage range is between 12-60V;

[0089] The vehicle-mounted device controller 22 is used to provide a serial port for the active antenna, and the vehicle-mounted device sends serial port signals through the serial port; the active antenna can work normally and realize the corresponding function only after the vehicle-mounted device sends the corresponding command through the serial port;

[0090] Furthermore, the serial port signal includes: the vehicle-mounted device sends an antenna beam elevation angle command to the antenna end; obtains the power amplifier PA transmission power and antenna temperature data; obtains antenna version information and TR unit gain information;

[0091] The vehicle-mounted device controller 22 is also used to send a front and rear antenna switching signal to the vehicle-mounted antenna; the front and rear antenna switching signal is used to control the TR unit to switch between the front and rear antennas;

[0092] A first radio frequency transceiver 23, used for providing a radio frequency input signal to the +45° polarized antenna TR unit and receiving a wireless signal from the +45° polarized antenna TR unit;

[0093] The first RF transceiver 23 is also used to send a transceiver control signal to the +45° polarized antenna TR unit, and the transceiver control signal is used to control the working timing of the transceiver switch, power amplifier, low noise amplifier and analog-to-digital converter of the TR unit of the +45° polarized directional antenna, which is synchronized with the working timing of the RF transceiver 23;

[0094] The second RF transceiver 24 is used to provide a RF input signal to the -45° polarized antenna TR unit and receive a wireless signal from the -45° polarized antenna TR unit;

[0095] The second RF transceiver 24 is also used to send a transceiver control signal to the -45° polarized antenna TR unit. The transceiver control signal is used to control the working timing of the transceiver switch, power amplifier, low noise amplifier and analog-to-digital converter of the TR unit of the -45° polarized directional antenna, and is synchronized with the working timing of the RF transceiver 24.

[0096] It should be noted that the connection order between the first RF transceiver 23 and the second RF transceiver 24 and the two polarized antenna TR units is not limited, that is, the RF transceiver 23 can provide RF input signals to the -45° polarized antenna TR unit and receive wireless signals from the -45° polarized antenna TR unit.

[0097] 1. Active phased array antenna hardware interface definition

[0098] Unlike traditional passive antennas, in addition to the RF signal connection, the active phased array antenna and the vehicle-mounted equipment also need to add power supply and control signals. In order to reduce the number of cables between the vehicle-mounted equipment and the active antenna, the power supply and control signals use a multi-core cable, such as Figure 4 As shown, a schematic diagram of the vehicle-mounted antenna installation, in this embodiment, three cables are included between the active antenna and the vehicle-mounted device;

[0099] The radio frequency cable is used to transmit radio frequency feed signals of two orthogonally polarized antennas;

[0100] Specifically comprising: a first radio frequency cable, used for transmitting a radio frequency feed signal of a +45° polarized antenna, or a radio frequency feed signal of a -45° polarized antenna;

[0101] The second RF cable is used to transmit a -45° polarized antenna RF feed signal or a +45° polarized antenna RF feed signal;

[0102] Multi-core cable, used to power the vehicle antenna, transmit and receive control signals, front and rear antenna switching signals, and serial port signals. The cable functions and definitions are shown in Table 1:

[0103]

[0104] Table 1

[0105] Figure 5 As shown, the hardware connection diagram of the vehicle-mounted equipment and the active antenna is as follows:

[0106] Among them, the front and rear antenna switching signals, serial port signals, and transceiver control signals are differential signals. Because the electromagnetic environment of high-speed trains is relatively harsh and the multi-core cable routing is long, in order to improve anti-interference ability and signal driving ability, the "transceiver control signal", "front and rear antenna switching signal" and "serial port signal" are all transmitted using differential lines.

[0107] 2. Active phased array antenna software interface definition

[0108] After the active phased array antenna is connected to the vehicle-mounted device hardware interface according to the cable function and definition, the vehicle-mounted device can send control commands through the serial port to realize the corresponding functions of the active antenna. The functions realized by the serial port include:

[0109] 1) Read the antenna version information, including basic text information such as software and hardware version information and program burning date. This function can be used to obtain antenna text information.

[0110] 2) Read the TR unit transceiver gain. When the vehicle-mounted equipment is in open-loop power control, the system needs to know the antenna TR unit transceiver gain.

[0111] 3) Control the antenna beam pitch angle by sending a beam pitch command to control the antenna beam pitch angle and return the execution result.

[0112] 4) Read the antenna PA output power and TR unit temperature information at different operating frequency bands.

[0113] For example, the serial port command definition is shown in Table 2:

[0114]

[0115]

[0116] Table 2

[0117] The active antenna can work normally only after the vehicle-mounted device sends control commands via the serial port, so the vehicle-mounted device using the active antenna needs to design the serial port commands as described in Table 2.

[0118] For example, after the vehicle-mounted device sends the hexadecimal "0xEE" command, the active antenna returns fixed text information such as the antenna's software and hardware version number, so that you can check whether the antenna version is correct;

[0119] After the vehicle-mounted device sends the hexadecimal "0xEA" command, the antenna returns the TR unit's send and receive gain values ​​to prepare for system power control;

[0120] After the vehicle-mounted device sends the hexadecimal "0xEC" or "0xED" command, the antenna returns the PA output power of each TR unit and the antenna TR unit temperature value;

[0121] After the vehicle-mounted device and active antenna are started and configured normally, the vehicle-mounted device sends any command from hexadecimal "0xF1" to "0xFF" as needed, and the antenna pitch angle is adjusted to the specified angle and the execution result is returned.

[0122] 3. Power detection and temperature detection

[0123] EUHT is a TDD communication system, in which transmission and reception are performed in time-sharing. It is necessary to detect the output power of the PA in the TR unit only in the transmission time slot, and no detection is required in the reception time slot. In order to realize the power detection function of the TDD system, the vehicle-mounted equipment in the present invention controls the power detection circuit, controls the working timing of the analog-to-digital converter by sending and receiving control signals, uses the sending and receiving control signals to synchronously enable the ADC mode, and synchronously samples the power detection signal of the transmission time slot.

[0124] The active antenna only detects the output power of the PA in the transmission time slot, so the power detection unit needs to be synchronized with the transmission signal. The power detection circuit of the present invention adopts the ADC mode of enabling the receiving and transmitting control signal to ensure that the ADC only samples the PD pin voltage in the transmission time slot;

[0125] like Figure 6As shown in the figure, taking one TR unit as an example, the "transceiver control signal" sent by the on-board equipment controls the working timing of the transceiver switch, PA, LNA and ADC. Generally, the RF signal is a modulated signal with large signal amplitude variation. In order to increase the stability of power detection, the PD signal is averaged after RC filtering and multiple sampling by the ADC. The output power of each TR unit is calculated based on the relationship between the detection voltage and the output power, and the result is written into the power storage unit. After the serial port receives the power detection command, the output power data of each PA is sent out through the RS422 serial port. If there is no power detection command, the storage unit is refreshed after each power detection, so that the storage unit data is always the power data of the most recent detection.

[0126] In order to obtain the best communication effect, the wireless communication system needs to perform power control. The active phased array vehicle-mounted antenna system provided by the present invention has power control divided into open-loop power control and closed-loop power control according to different scenarios. The two power control methods are specifically described in Example 3 and Example 4 below.

[0127] Embodiment 3

[0128] This embodiment illustrates an open-loop power control method for an active phased array vehicle-mounted antenna system;

[0129] Open-loop power control is implemented based on the reciprocity principle of uplink and downlink channels. From the perspective of vehicle-mounted equipment, the uplink and downlink channel reciprocity of active antennas and passive antennas is different. The receiving and transmitting gains of passive antennas are the same, which meets the uplink and downlink channel reciprocity conditions; however, the receiving and transmitting gains of active antenna TR units are different. From the perspective of vehicle-mounted equipment, the uplink and downlink channels are no longer reciprocal, so the open-loop power control algorithm of active antennas is different from that of passive antennas. According to the proof, the open-loop power control of active antennas can be modified and implemented based on the open-loop power control algorithm of passive antennas.

[0130] The present invention calculates the transmit and receive power of the active antenna under open-loop power control, including:

[0131] 1. Based on the passive antenna open-loop power control algorithm, calculate the transmission power required by the vehicle-mounted equipment;

[0132] 2. Obtain the transmit gain and receive gain of the active antenna TR unit, and calculate the difference between the transmit and receive gain of the active antenna TR unit;

[0133] 3. Subtract the difference between the transmit and receive gain of the active antenna TR unit from the calculated transmit power required by the vehicle-mounted device to obtain the transmit power of the vehicle-mounted device when the active antenna is connected.

[0134] Because the transmit and receive gains of the active antenna TR unit are different, according to the passive antenna open-loop power control algorithm, the required transmit power is calculated and then the difference between the transmit gain and the receive gain of the active antenna TR unit is subtracted to obtain the transmit power required by the active antenna, thereby realizing the open-loop power control of the active antenna.

[0135] Specifically, after the vehicle-mounted device is connected to the active antenna, the passive antenna open-loop power control algorithm is used to obtain the required transmission power P of the vehicle-mounted device. N , because the transmitting gain of the active antenna TR unit is greater than the receiving gain by ΔG, the vehicle-mounted equipment still transmits P when there is an active antenna N , the signal received by the base station will be higher than ΔG, so the transmission power of the vehicle-mounted equipment connected to the active antenna needs to be changed to P N -ΔG can ensure that the signal strength received by the base station is the required target strength. ΔG can be calculated by reading the TR unit transceiver gain through the serial port.

[0136] Embodiment 4

[0137] This embodiment illustrates a closed-loop power control method for an active phased array vehicle-mounted antenna system;

[0138] The vehicle-mounted equipment increases or decreases the transmission power in specific steps according to the power control command issued by the base station to realize the closed-loop power control of the wireless system. The closed-loop power control can ensure that the signal strength received by the base station is always in the best state, and requires that the transmission power of the vehicle-mounted equipment in the closed-loop power control cannot exceed the maximum transmission power of the system;

[0139] The vehicle-mounted equipment needs to obtain the maximum transmission power P of the system max , and the power step value P step The vehicle-mounted equipment obtains the maximum transmission power P during the production calibration phase. STAmax and power step P step Two parameters, when using a passive antenna, the maximum transmission power P of the vehicle-mounted equipment STAmax That is the maximum transmission power P of the system max , the transmission power of the vehicle-mounted equipment does not exceed P during closed-loop power control of the passive antenna system STAmax Under the premise, according to the power control command, step Increase or decrease transmit power.

[0140] When using an active antenna, the final PA is inside the active antenna, and the system maximum transmit power P max Determined by the TR unit of the active antenna, the vehicle equipment calibration link can only obtain the power step P step When using an active antenna, use the active antenna power detection function to calculate the output power P' of the vehicle-mounted equipment when the TR unit transmits the maximum power. STAmax , P′ STAmax is the maximum transmission power allowed by the vehicle-mounted device when the active antenna is connected, combined with the P obtained by the vehicle-mounted device calibration step , closed-loop power control of active antennas can be achieved.

[0141] The vehicle-mounted equipment has obtained the maximum transmission power P during the production calibration phase. STAmax and P step , the maximum transmission power of the active antenna TR unit is P max After the vehicle-mounted device and the active antenna are installed, the vehicle-mounted device first sends a specific power P0 as the active antenna input signal to ensure that the PA of the antenna TR unit is in the linear range and P0≤P STAmax , read the active antenna TR unit output power P1 through the serial port, then when the active antenna transmits the maximum power P max When the output power of the vehicle equipment is:

[0142] P′ STAmax =P max +P0-P1

[0143] Among them, P′ STAmax The maximum transmission power allowed by the vehicle-mounted equipment when the active antenna is connected. When the active antenna is in closed-loop power control, the transmission power of the vehicle-mounted equipment shall not exceed P' STAmax Under this premise, combined with the P obtained during calibration step According to the power control command issued by the base station, according to P step Increase or decrease the transmit power to achieve closed-loop power control of active antennas.

[0144] Application Examples

[0145] The elevation angle formed by the line connecting the vehicle antenna and the base station antenna gradually changes as the train travels on the railway. The vehicle system adjusts the elevation angle of the vehicle antenna in real time according to the location of the vehicle antenna. Figure 7 Shown is a schematic diagram of active phased array antenna beam adjustment;

[0146] like Figure 8 The vertical radiation pattern corresponding to different antenna beam tilt commands at 5150MHz frequency is shown;

[0147] According to the active phased array vehicle-mounted antenna system provided in the above embodiment, the vehicle-mounted equipment adjusts the main lobe of the vehicle-mounted antenna to point in the direction of the base station antenna in real time, thereby improving the signal strength along the system; when the train is traveling along the line, the active antenna switches between three different elevation angles, and when the vehicle-mounted antenna is close to the base station antenna, angle 3 is used; when the train continues to move forward, the antenna elevation angle is switched to angle 2 and angle 1 in turn, and the vehicle-mounted antenna switches to different antenna elevation angles in three positions in turn, so that the main lobe of the vehicle-mounted antenna is always pointed to the base station antenna when the train is traveling along the rails.

[0148] When the three beams of the active antenna are used alone, the test results are as follows: Fig. 9 As shown in Figure 2, the signal strength distribution along the line is as follows: Fig. 9Each of the three curves has a section with low signal, so when the three beams are used alone, they cannot guarantee the best signal along the line. When the train is at different positions, the active antenna pitch angle is adjusted in real time between the three beams, and each position selects the beam with the strongest signal to point to the base station antenna. Fig. 9 The middle ※ curve shows the envelope formed by three signal curves after the real-time adjustment between beams.

[0149] It can be seen that the active phased array vehicle-mounted antenna system provided by the present invention can significantly enhance the system signal strength, thereby increasing the wireless coverage distance.

[0150] It will be appreciated by those skilled in the art that the various exemplary method steps and device units described herein in conjunction with the disclosed embodiments can all be implemented in electronic hardware, software, or a combination of the two. In order to clearly illustrate the interchangeability between hardware and software, the various exemplary steps and units are generally described in the form of their functionality. Whether this functionality is implemented in hardware or software depends on the design constraints implemented by the specific application and the entire system. Those skilled in the art can implement the described functionality in a variety of ways for each specific application, but the results of this implementation should not be interpreted as departing from the scope of the present invention.

[0151] The steps of the method described in conjunction with the above disclosed embodiments may be directly embodied as hardware, a software module executed by a processor, or a combination of the two. The software module may exist in a RAM memory, a flash memory, a ROM memory, an EPROM memory, an EEPROM memory, a register, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. A typical storage medium is coupled to a processor so that the processor can read information from the storage medium and write information to the storage medium. In an alternative embodiment, the storage medium is an integral part of the processor. The processor and the storage medium may exist in an ASIC. The ASIC may exist in a user station. In an alternative embodiment, the processor and the storage medium may exist as discrete components in a user station.

[0152] According to the disclosed embodiments, it is possible for those skilled in the art to implement or use the present invention. It is obvious to those skilled in the art that various modifications of these embodiments are possible, and the general principles defined herein can also be applied to other embodiments without departing from the scope and gist of the present invention. The embodiments described above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An active phased array vehicle-mounted antenna system suitable for high-speed rail, characterized in that: include: Active phased array vehicle-mounted antennas, vehicle-mounted equipment; The vehicle-mounted device controls and adjusts the pitch angle of the active phased array vehicle-mounted antenna so that the main lobe of the vehicle-mounted antenna points in real time to the direction of the base station antenna; The vehicle-mounted antenna comprises a pair of directional antennas, and the pair of directional antennas are orthogonal dual-polarization directional antennas; The two directional antennas are arranged back-to-back, with the main beam of the forward antenna pointing in the same direction as the front of the vehicle, and the main beam of the rear antenna pointing in the opposite direction. In the pair of directional antennas, each pair of antennas consists of M rows and N columns, and M*N dual-polarization elements form an antenna array; M and N are positive integers; the vehicle-mounted antenna includes 2*M*N TR units, and a radio frequency switch is used at the end of each TR unit to switch between the front and rear directional antennas, and each TR unit feeds the front and rear directional antennas respectively; The M*N dual-polarization oscillators include a zero-degree phase oscillator, which is an antenna phase reference point and has a phase of 0° at different elevation angles; the phase shifter in the TR unit of the zero-degree phase oscillator is removed.

2. The active phased array vehicle-mounted antenna system according to claim 1, characterized in that: include: A one-to-one correspondence between the vehicle-mounted antenna pitch angle command and the vehicle-mounted antenna pitch angle is preset.

3. The active phased array vehicle-mounted antenna system according to claim 1 or 2, characterized in that: The vehicle-mounted device sends a pitch angle command to the vehicle-mounted antenna through the serial port. After receiving the pitch angle command, the vehicle-mounted antenna adjusts the phase value of the TR unit inside each antenna according to the preset pitch angle command and the corresponding relationship between the pitch angle, and controls the vehicle-mounted antenna to point to the corresponding angle.

4. The active phased array vehicle-mounted antenna system according to claim 1, characterized in that: The input RF signal is divided into M*N signals after the power divider to feed M*N TR units; The input signal passes through the attenuator, phase shifter, RF transceiver switch, power amplifier, and low noise amplifier in each TR unit, and then feeds the forward or backward antenna element.

5. The active phased array vehicle-mounted antenna system according to claim 1, characterized in that: The power control implementation methods of active phased array vehicle-mounted antenna systems include open-loop power control and closed-loop power control.

6. The active phased array vehicle-mounted antenna system according to claim 5, characterized in that: The open-loop power control algorithm comprises: Based on the passive antenna open-loop power control algorithm, calculate the transmission power required by the vehicle-mounted equipment; Obtain the transmission gain and receiving gain of the active antenna TR unit, and calculate the difference between the transmitting and receiving gains of the active antenna TR unit; The calculated transmission power required by the vehicle-mounted device is subtracted from the difference in the transmit and receive gain of the active antenna TR unit to obtain the transmission power of the vehicle-mounted device when the active antenna is connected.

7. The active phased array vehicle-mounted antenna system according to claim 1, characterized in that: The connection between the vehicle-mounted device and the vehicle-mounted antenna includes: A radio frequency cable, used for transmitting radio frequency feed signals of two orthogonally polarized antennas; Multi-core cable, used to power the vehicle antenna, transmit and receive control signals, front and rear antenna switching signals, and serial port signals.

8. A vehicle-mounted device, characterized in that: The vehicle-mounted equipment provides power, control signals, and inputs RF signals to the active phased array vehicle-mounted antenna; The vehicle-mounted equipment includes: Power module, vehicle equipment controller, RF transceiver; The power module is used to provide power to the vehicle-mounted antenna; The vehicle-mounted device controller is used to provide a serial port for the active antenna, and the vehicle-mounted device sends a serial port signal through the serial port; the serial port signal includes: the vehicle-mounted device sends an antenna beam elevation angle command to the antenna end; obtains the power amplifier PA transmission power and antenna temperature data; obtains antenna version information and TR unit gain information; The vehicle-mounted device controller is also used to send a front and rear antenna switching signal to the vehicle-mounted antenna; the front and rear antenna switching signal is used to control the TR unit to switch between the two directional antennas; The RF transceiver is used to provide RF input signals to the TR unit in the vehicle-mounted antenna and receive wireless signals from the vehicle-mounted antenna; The vehicle-mounted equipment controls the power detection circuit, controls the working timing of the analog-to-digital converter by sending and receiving control signals, and detects the output power of the power amplifier of the TR unit in the transmission slot; The transceiver control signal is used to control the operating timing of the transceiver switch, power amplifier, low noise amplifier and analog-to-digital converter of the two TR units of a pair of directional antennas, and is synchronized with the operating timing of the RF transceiver.

9. The vehicle-mounted device according to claim 8, characterized in that: The front and rear antenna switching signals, serial port signals, and transceiver control signals are differential signals.

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