Railway 400mhz multi-band radio signal scanning device

Abstract

The application discloses a railway 400MHz multi-frequency band radio frequency signal scanning device and relates to the technical field of electrical testing and measurement, which comprises a protective shell. An opening is arranged on the side of the protective shell, and an SMA female seat is arranged at the opening. The optical true time delay beam forming architecture is adopted to replace the traditional electronic phase shift scheme, so that instantaneous wideband beam scanning can be realized in a 1GHz-4GHz wide frequency range, and the problem of beam tilting can be effectively eliminated. Through injection locking frequency stabilization and sub-picosecond level time delay calibration, high-precision beam scanning of ±35 degrees is realized in combination with numerical control phase shift. The all-optical link is resistant to electromagnetic interference and low in loss, and is suitable for complex electromagnetic environments of railways. The integrated IQ quadrature frequency conversion supports automatic calibration and high-speed sampling, and the signal quality is good and real-time performance is strong.

Description

Technical Field

[0001] This invention relates to the field of electrical testing and measurement technology, specifically a railway 400MHz multi-band radio frequency signal scanning device. Background Technology

[0002] The railway communication field widely uses multi-band radio frequency signals such as 400MHz band (400~470MHz), L band (1~2GHz), and S band (2~4GHz). The transmission environment is complex, with strong multipath interference and high electromagnetic noise, which puts forward high requirements for broadband, high precision and stable scanning of radio frequency signals. Existing railway radio frequency scanning equipment mostly adopts traditional electronic phase shifting or electronic delay schemes, which have limited operating bandwidth. During wideband scanning, problems such as beam tilt and dispersion shift are prone to occur, making it difficult to achieve instantaneous wideband scanning. At the same time, electronic phase shifters have high high-frequency loss and low time delay calibration accuracy, which is usually difficult to reach the sub-picosecond level. The poor consistency of multi-channel time delay leads to inaccurate beam pointing and limited scanning angle, making it difficult to meet the railway's requirements for large-angle and high-precision scanning. In addition, traditional electronic links are susceptible to electromagnetic interference and have high link loss, resulting in poor stability and low signal-to-noise ratio in the complex electromagnetic environment of railways. Therefore, there is an urgent need for a railway multi-band radio frequency signal scanning device that can achieve instantaneous broadband, high precision, and anti-interference capabilities to solve the technical defects of existing technologies such as beam tilt, insufficient accuracy, and weak anti-interference ability. Summary of the Invention

[0003] Therefore, in order to overcome the above-mentioned shortcomings, the present invention provides a railway 400MHz multi-band radio frequency signal scanning device.

[0004] This invention is implemented as follows: a railway 400MHz multi-band radio frequency signal scanning device is constructed, comprising a protective housing; characterized in that: an opening is provided on the side of the protective housing, and an SMA female connector is provided at the opening; the SMA female connector is fixedly installed on the bottom left side of a PCB motherboard, and the PCB motherboard is fixedly installed inside the protective housing; the PCB motherboard has a single-layer structure, and a broadband directional coupler is fixedly soldered to the top left side of the PCB motherboard, and the broadband directional coupler is connected in series between the SMA female connector and a digitally controlled phase shifter; the output end of the digitally controlled phase shifter is connected to the input end of a radio frequency driver amplifier, and the output end of the radio frequency driver amplifier is connected to the radio frequency end of a miniature optical modulator; the optical end of the miniature optical modulator is connected to a miniature fiber optic socket, and the miniature fiber optic socket is connected to the input end of a photodetector; the output end of the photodetector is connected to a radio frequency combiner; the broadband directional coupler, digitally controlled phase shifter, radio frequency driver amplifier, miniature optical modulator, miniature fiber optic socket, photodetector, radio frequency combiner, low-noise amplifier, radio frequency front-end frequency conversion module, and digital calibration integrated module are sequentially integrated on the surface of the PCB motherboard; the signal output socket is located on the top right side of the PCB motherboard.

[0005] Preferably, the miniature fiber optic socket is connected to the photodetector via a polarization-maintaining fiber optic patch cord.

[0006] Preferably, the RF front-end frequency conversion module adopts an IQ quadrature mixing architecture and integrates differential amplification and low-pass filtering units.

[0007] Preferably, the miniature optical modulator and photodetector adopt an injection-locked frequency stabilization architecture to suppress frequency jitter and meet the multi-channel delay consistency requirements; the delay calibration algorithm formula is: ; in, For delay amount, For radio frequency signal phase, This refers to the frequency of the radio frequency signal.

[0008] Preferably, the miniature optical modulator, the miniature fiber optic socket, and the photodetector constitute an optical true time-delay beamforming network.

[0009] Preferably, the digital calibration integration module is configured to achieve multi-channel beam scanning by controlling the bias voltage of the numerically controlled phase shifter and the micro optical modulator, wherein the beam scanning angle satisfies the angle range of ±35°.

[0010] Preferably, the digital calibration integrated module is equipped with a PCIe 3.0 x8 bus interface, a maximum sampling rate ≥250MSPS, and supports automatic IQ imbalance calibration. The calibration compensation formula is as follows: ; Where A, C, and D are calibration coefficients, and DC bias is applied to the IQ channel.

[0011] Preferably, the numerically controlled phase shifter adopts a programmable amplification architecture with 0.25dB step and 4.5 to 20.25dB adjustable gain, and the phase adjustment range is 0° to 360°, supporting a single-frequency point controllable delay scan calibration mode.

[0012] Preferably, the broadband directional coupler is a microstrip line coupler with a coupling degree ≥20dB and a directivity ≥25dB; the numerically controlled phase shifter is a 6-bit digital phase shifter.

[0013] A method for using a railway 400MHz multi-band radio frequency signal scanning device includes the following steps: Step 1: The radio frequency signal is input from the SMA female connector, directionally transmitted through the broadband directional coupler, and then the phase coarse adjustment is completed by the digitally controlled phase shifter; Step 2: The RF driver amplifier amplifies the signal and sends it to the miniature optical modulator to complete the electro-optical conversion, modulating the RF signal onto the optical carrier. Step 3: The modulated optical signal is transmitted to the photodetector through the miniature fiber optic socket and polarization-maintaining fiber optic patch cord to complete photoelectric demodulation and restore the radio frequency signal; Step 4: The demodulated RF signal is combined by an RF combiner, amplified by a low-noise amplifier, and then sent to the RF front-end frequency conversion module. IQ quadrature mixing is used to complete the down-conversion and output the intermediate frequency signal. Step 5: The digital calibration integration module realizes high-speed sampling and automatic IQ imbalance calibration through the bus, and combines frequency stabilization and delay algorithms to dynamically control the digitally controlled phase shift and the bias voltage of the optical modulator. The scanning signal is finally output by the signal output socket.

[0014] The present invention has the following advantages: The present invention provides an improved 400MHz multi-band radio frequency signal scanning device for railways, which, compared with similar devices, has the following improvements: The railway 400MHz multi-band radio frequency signal scanning device described in this invention adopts an optical true time-delay beamforming architecture to replace the traditional electronic phase-shifting scheme. It can achieve instantaneous broadband beam scanning in a wide frequency range of 1GHz to 4GHz, effectively eliminating beam tilt problems. Through injection-locked frequency stabilization and sub-picosecond delay calibration, combined with digitally controlled phase shifting, it achieves ±35° high-precision beam scanning. The all-optical link is resistant to electromagnetic interference and has low loss, making it suitable for the complex electromagnetic environment of railways. It integrates IQ quadrature frequency conversion, supports automatic calibration and high-speed sampling, and has good signal quality and strong real-time performance. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the process of this invention; Figure 2 This is a schematic diagram of the protective shell structure of the present invention; Figure 3 This is a schematic diagram of the top axial structure of the PCB motherboard of the present invention; Figure 4 This is a schematic diagram of the bottom structure of the PCB motherboard of the present invention.

[0016] The components include: protective housing-1, SMA female connector-2, PCB motherboard-3, broadband directional coupler-4, digitally controlled phase shifter-5, RF driver amplifier-6, miniature optical modulator-7, miniature fiber optic socket-8, photodetector-9, RF combiner-10, low-noise amplifier-11, RF front-end frequency converter module-12, digital calibration integrated module-13, and signal output socket-14. Detailed Implementation

[0017] The following is in conjunction with the appendix Figures 1-4 The principles and features of the present invention are described below. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. The invention is described more specifically in the following paragraphs by way of example with reference to the accompanying drawings. It should be noted that the drawings are in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the invention.

[0018] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0019] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "setting" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. The embodiments of this invention will now be described according to its overall structure.

[0020] Example 1:

[0021] Please see Figures 1-4The present invention provides a railway 400MHz multi-band radio frequency signal scanning device, comprising a protective housing 1; the protective housing 1 has an opening on its side, and an SMA female connector 2 is fixedly installed at the opening for the access of an external antenna or test cable; the SMA female connector 2 is fixedly soldered to the bottom left side of a PCB motherboard 3, the PCB motherboard 3 being a single-layer board, and is fixedly installed inside the protective housing 1.

[0022] On the top left side of the PCB motherboard 3, a broadband directional coupler 4 is fixedly soldered. This broadband directional coupler 4 is connected in series between the SMA female connector 2 and the digitally controlled phase shifter 5, and is used to couple forward and reverse power from the main signal path for subsequent standing wave detection and self-calibration. The output of the digitally controlled phase shifter 5 is connected to the input of the RF driver amplifier 6, and the output of the RF driver amplifier 6 is connected to the RF input of the miniature optical modulator 7. The optical output of the miniature optical modulator 7 is connected to the miniature fiber optic socket 8, and the miniature fiber optic socket 8 is connected to the input of the photodetector 9 through a polarization-maintaining fiber optic patch cord. The output of the photodetector 9 is connected to the RF combiner 10.

[0023] The output of the RF combiner 10 is fed into the RF front-end frequency converter module 12 after passing through the low-noise amplifier 11; the output of the RF front-end frequency converter module 12 is connected to the digital calibration integrated module 13; the broadband directional coupler 4, the digitally controlled phase shifter 5, the RF drive amplifier 6, the miniature optical modulator 7, the miniature fiber optic socket 8, the photodetector 9, the RF combiner 10, the low-noise amplifier 11, the RF front-end frequency converter module 12, and the digital calibration integrated module 13 are sequentially integrated on the surface of the PCB motherboard 3; the signal output socket 14 is located on the top right side of the PCB motherboard 3 and is used to output the processed RF scanning results or intermediate frequency signals.

[0024] The RF front-end frequency conversion module 12 adopts an IQ quadrature mixer architecture. The module integrates an IQ quadrature demodulator, two differential amplifiers and two low-pass filters. The local oscillator input of the IQ quadrature demodulator receives the local oscillation signal from the digital calibration integrated module 13 or an independent local oscillator source. Its RF input is connected to the output of the low-noise amplifier 11. The IQ quadrature demodulator downconverts the RF signal into analog in-phase I signal and quadrature Q signal, which are output in differential form.

[0025] Example 2:

[0026] Please see Figures 1-4This invention provides a scanning and measurement device for 400MHz multi-band radio frequency signals in railways. Compared to Embodiment 1, this embodiment further includes: a miniature optical modulator 7 generating optical sidebands under radio frequency driving signal modulation, extracting higher-order sidebands through an optical filter and injecting them into a slave laser; the slave laser outputs a frequency-stabilized optical signal with a frequency coherent with the reference light under injection locking, which is then converted into a radio frequency signal by a photodetector 9. This architecture suppresses the frequency jitter of the local oscillator to ≤1MHz.

[0027] Meanwhile, this device employs the following delay calibration algorithm to achieve multi-channel delay consistency calibration: ; in, For delay amount, For radio frequency signal phase, For the radio frequency signal frequency, during the actual calibration process, the digital calibration integrated module 13 generates a frequency sweep signal, measures the phase-frequency slope between adjacent channels, calculates the delay amount, and compensates for it by adjusting the digitally controlled phase shifter 5 or the optical link delay line.

[0028] Example 3:

[0029] Please see Figures 1-4 The present invention provides a railway 400MHz multi-band radio frequency signal scanning device. Compared with Embodiment 1, this embodiment further includes: a digital calibration integrated module 13 equipped with a PCIe 3.0 x8 bus interface, with a maximum sampling rate ≥250MSPS, and supports automatic IQ imbalance calibration using the following compensation formula: ; Where A, C, and D are calibration coefficients, and The I / Q channel is DC biased; the calibration coefficient is obtained by injecting a single-tone test signal and calculating it statistically. The specific calibration process is as follows: collect multiple sets of I / Q data, calculate the amplitude imbalance factor and phase imbalance factor, then solve for the A, C, and D parameters, and finally perform real-time compensation for each frame of data.

[0030] The working principle of a railway 400MHz multi-band radio frequency signal scanning device based on the above is as follows: The radio frequency (RF) signal is input from the SMA female connector 2, directionally transmitted through the broadband directional coupler 4, and then coarsely phase-adjusted by the digitally controlled phase shifter 5. The RF driver amplifier 6 amplifies the signal to optical modulation and sends it to the miniature optical modulator 7 to complete electro-optical conversion, modulating the RF signal onto the optical carrier. The modulated optical signal is transmitted to the photodetector 9 through the polarization-maintaining fiber jumper of the miniature fiber optic socket 8 to complete photoelectric demodulation and recover the RF signal. The miniature optical modulator 7, the fiber optic transmission socket 8, and the photodetector 9 constitute an optical true time-delay beamforming network, which achieves time delay control through optical path difference, suppresses frequency jitter, ensures multi-channel time delay consistency, and avoids broadband beam tilt. The demodulated RF signal is combined and amplified by the RF combiner 10 and the low-noise amplifier 11, and then sent to the RF front-end frequency conversion module 12. The down-conversion is completed by the IQ quadrature mixing architecture, and the intermediate frequency signal is output. The digital calibration integration module 13 realizes high-speed sampling and automatic IQ imbalance calibration based on the bus. At the same time, it combines injection lock frequency stabilization and delay calibration algorithms to dynamically control the phase of the digitally controlled phase shifter 5 and the bias voltage of the micro optical modulator 7 to achieve ±35° instantaneous broadband beam scanning. Finally, the scanning signal is output by the signal output jack 14, which is suitable for railway L / S band RF monitoring scenarios.

[0031] This invention provides an improved 400MHz multi-band radio frequency signal scanning device for railways. It adopts an optical true time-delay beamforming architecture to replace the traditional electronic phase-shifting scheme, enabling instantaneous broadband beam scanning in a wide frequency range of 1GHz to 4GHz, effectively eliminating beam tilt problems. Through injection-locked frequency stabilization and sub-picosecond delay calibration, combined with digitally controlled phase shifting, it achieves ±35° high-precision beam scanning. The all-optical link is resistant to electromagnetic interference and has low loss, making it suitable for the complex electromagnetic environment of railways. It integrates IQ quadrature frequency conversion, supports automatic calibration and high-speed sampling, and has good signal quality and strong real-time performance.

[0032] The above description shows and illustrates the basic principles, main features, and advantages of the present invention. Standard parts used in the present invention can be purchased from the market, and irregular parts can be customized according to the description and drawings. The specific connection methods of each part adopt conventional methods such as bolts, rivets, and welding that are mature in the prior art. The machinery, parts, and equipment adopt conventional models in the prior art, and the circuit connection adopts conventional connection methods in the prior art, which will not be described in detail here.

[0033] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A railway 400MHz multi-band radio frequency signal scanning device, comprising a protective housing (1); characterized in that: The protective housing (1) has an opening on its side, and an SMA female connector (2) is provided at the opening. The SMA female connector (2) is fixedly installed on the bottom left side of the PCB motherboard (3), and the PCB motherboard (3) is fixedly installed inside the protective housing (1). The PCB motherboard (3) is a single-layer structure. A broadband directional coupler (4) is fixedly welded to the top left side of the PCB motherboard (3), and the broadband directional coupler (4) is connected in series between the SMA female connector (2) and the numerically controlled phase shifter (5). The output end of the numerically controlled phase shifter (5) is connected to the input end of the radio frequency drive amplifier (6), and the output end of the radio frequency drive amplifier (6) is connected to the radio frequency end of the miniature optical modulator (7). The optical end of the miniature optical modulator (7) is connected to the miniature optical fiber socket (8), and the miniature optical fiber socket (8) is connected to the input end of the photodetector (9). The output end of the photodetector (9) is connected to the radio frequency combiner (10). The broadband directional coupler (4), digitally controlled phase shifter (5), radio frequency driver amplifier (6), miniature optical modulator (7), miniature fiber optic socket (8), photodetector (9), radio frequency combiner (10), low noise amplifier (11), radio frequency front-end frequency converter (12), and digital calibration integration module (13) are sequentially integrated on the surface of the PCB motherboard (3); the signal output socket (14) is located on the top right side of the PCB motherboard (3).

2. The railway 400MHz multi-band radio frequency signal scanning device according to claim 1, characterized in that: The miniature fiber optic socket (8) and the photodetector (9) are connected by a polarization-maintaining fiber optic patch cord.

3. The railway 400MHz multi-band radio frequency signal scanning device according to claim 2, characterized in that: The radio frequency front-end frequency conversion module (12) adopts an IQ quadrature mixing architecture and integrates differential amplification and low-pass filtering units.

4. The railway 400MHz multi-band radio frequency signal scanning device according to claim 3, characterized in that: The micro optical modulator (7) and photodetector (9) adopt an injection-locked frequency stabilization architecture, suppressing frequency jitter and meeting the multi-channel delay consistency requirements; the delay calibration algorithm formula is: ； in, For delay amount, For radio frequency signal phase, This refers to the frequency of the radio frequency signal.

5. The railway 400MHz multi-band radio frequency signal scanning device according to claim 4, characterized in that: The micro optical modulator (7), micro optical fiber socket (8), and photodetector (9) constitute an optical true time delay beamforming network.

6. The railway 400MHz multi-band radio frequency signal scanning device according to claim 5, characterized in that: The digital calibration integration module (13) is configured to achieve multi-channel beam scanning by controlling the bias voltage of the numerically controlled phase shifter (5) and the micro optical modulator (7), with the beam scanning angle satisfying an angle range of ±35°.

7. The railway 400MHz multi-band radio frequency signal scanning device according to claim 6, characterized in that: The digital calibration integrated module (13) is equipped with a PCIe 3.0 X8 bus interface, with a maximum sampling rate ≥250MSPS, and supports automatic IQ imbalance calibration. The calibration compensation formula is: ； Where A, C, and D are calibration coefficients, and DC bias is applied to the IQ channel.

8. The railway 400MHz multi-band radio frequency signal scanning device according to claim 7, characterized in that: The numerically controlled phase shifter (5) adopts a programmable amplification architecture with 0.25dB step and 4.5 to 20.25dB adjustable gain. The phase adjustment range is 0° to 360°, and it supports single-frequency point controllable delay scanning calibration mode.

9. The railway 400MHz multi-band radio frequency signal scanning device according to claim 8, characterized in that: The broadband directional coupler (4) is a microstrip line coupler with a coupling degree ≥20dB and a directivity ≥25dB; the numerically controlled phase shifter (5) is a 6-bit digital phase shifter.

10. A method of using a railway 400MHz multi-band radio frequency signal scanning device, for implementing the railway 400MHz multi-band radio frequency signal scanning device as described in claim 9, characterized in that: Includes the following steps: Step 1: The radio frequency signal is input from the SMA female connector (2), directionally transmitted through the broadband directional coupler (4), and then the phase coarse adjustment is completed by the digitally controlled phase shifter (5); Step 2: The radio frequency driver amplifier (6) amplifies the signal and sends it to the miniature optical modulator (7) to complete the electro-optical conversion and modulate the radio frequency signal onto the optical carrier. Step 3: The modulated optical signal is transmitted to the photodetector (9) through the miniature optical fiber socket (8) and polarization-maintaining optical fiber jumper to complete photoelectric demodulation and restore the radio frequency signal; Step 4: The demodulated RF signal is combined by the RF combiner (10), amplified by the low noise amplifier (11), and then sent to the RF front-end frequency conversion module (12). The down-conversion is completed by IQ quadrature mixing, and the intermediate frequency signal is output. Step 5: The digital calibration integration module (13) realizes high-speed sampling and automatic IQ imbalance calibration through the bus, and combines frequency stabilization and delay algorithms to dynamically control the digital phase shift phase and the optical modulator bias voltage. The scanning signal is finally output by the signal output socket (14).

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