A VDB time slot signal field strength measurement system for ground-based augmentation system

Abstract

The present invention relates to a VDB time slot signal field strength measurement system of a ground-based augmentation system, wherein a first VDB signal receiving unit receives a VDB horizontal polarization signal to obtain VDB horizontal polarization signal power data of a VDB signal transmitted by a GBAS ground station; a second VDB signal receiving unit receives a VDB vertical polarization signal to obtain VDB vertical polarization signal power data of a VDB signal transmitted by a GBAS ground station; and a VDB field strength data processing unit determines the signal field strength value of the VDB horizontal polarization signal and the signal field strength value of the VDB vertical polarization signal according to the VDB horizontal polarization signal power data and the VDB vertical polarization signal power data. The embodiment of the present invention adopts a dual-polarization antenna parallel measurement technology, calculates the azimuth of a VDB ground transmitting station, compensates for antenna gain in real time, eliminates the influence of different antennas on the measurement effect, and achieves the effect of VDB time slot signal field strength measurement in a dynamic scene.

Description

Technical Field

[0001] The invention belongs to the technical field of flight calibration, and in particular relates to a VDB time slot signal field strength measurement system of a ground-based augmentation system. Background Art

[0002] GNSS (Global Navigation Satellite System) ground-based augmentation system, also known as GBAS system (Ground-Based Augmentation Systems), is a new technology in the field of civil aviation navigation. Based on the original GPS standard positioning service, it reduces pseudo-range errors by inputting pseudo-range differential correction data into the receiver terminal, thereby achieving higher positioning accuracy. At the same time, airport runway configuration data FAS data, ground station information data and integrity data are also input into the receiver terminal. The GBAS system is set up within the airport and includes multiple GPS receivers, a data processing center, a VDB (VHF DATA BTOADCAST) transmitter (very high frequency data broadcast transmitter) and related monitoring equipment. In order to achieve better signal coverage, multiple VDB transmitters are usually set up. Multiple VDB transmitters use time division multiplexing TDMA to share the same VHF transmission frequency point. Among them, the GPS receiver is set up at a known coordinate point. The data processing center receives and processes the observation data of multiple GPS receivers, and finally forms differential correction data and integrity information, which are sent to civil aircraft in the service area through the VDB transmitter. Civil aircraft are equipped with multi-mode receivers that integrate VDB receiving function and GPS positioning processing function. Civil aircraft receive the enhanced data sent by the ground through the VDB receiving module, and finally complete the differential positioning, and output the aircraft approach guidance data in real time for the aircraft approach and landing.

[0003] GBAS system is an important part of civil aviation navigation equipment. According to ICAO requirements, GBAS system needs to be regularly inspected on the ground and its space signal needs to be checked in flight. The spatial coverage of the signal transmitted by the VDB transmitter is an important inspection object for ground inspection and flight verification of GBAS system. ICAO has made clear requirements on the VDB signal strength within the service area of ​​GBAS system. The VDB horizontal polarization signal strength is >-99dBW / m 2 , vertical polarization signal strength>-103dBW / m 2 .

[0004] In the existing flight verification system, a standard multi-mode receiver is used to receive the VDB signal transmitted by the GBAS ground station during the VDB signal flight verification process. The VDB signal coverage is indirectly measured by collecting the automatic gain control signal (AGC) output by the multi-mode receiver. The measurement method in the existing aircraft verification system can only give the power value of the VDB signal received at the antenna port of the receiver, and cannot eliminate the influence of different antenna gains, cannot directly measure the spatial field strength value of the VDB signal, and cannot distinguish between the horizontal polarization component and the vertical polarization component of the VDB signal. What is more disadvantageous is that in the case of multiple GBAS ground stations, the existing flight verification system does not have the ability to measure multiple VDB transmitting stations because it cannot identify TDMA time slots. Summary of the invention

[0005] In order to solve the technical problems that the above-mentioned existing flight verification system does not have the ability to measure multiple VDB transmitting stations and cannot directly obtain VDB signal data, the present invention proposes a VDB time slot signal field strength measurement system of a ground-based augmentation system, including a VDB horizontal polarization antenna, a first VDB signal receiving unit, a VDB vertical polarization antenna, a second VDB signal receiving unit and a VDB field strength data processing unit.

[0006] The VDB horizontal polarization antenna receives a VDB horizontal polarization signal;

[0007] The first VDB signal receiving unit receives a VDB horizontal polarization signal from the VDB horizontal polarization antenna to obtain VDB horizontal polarization signal power data of the VDB signal transmitted by the GBAS ground station;

[0008] The VDB vertical polarization antenna receives a VDB vertical polarization signal;

[0009] The second VDB signal receiving unit receives a VDB vertical polarization signal from the VDB vertical polarization antenna to obtain VDB vertical polarization signal power data of the VDB signal transmitted by the GBAS ground station;

[0010] The VDB field strength data processing unit determines a signal field strength value Sp of a VDB horizontal polarization signal and a signal field strength value Sv of a VDB vertical polarization signal according to the VDB horizontal polarization signal power data and the VDB vertical polarization signal power data.

[0011] In one embodiment, the VDB time slot signal field strength measurement system of the ground-based augmentation system further comprises a GPS receiver, which receives GPS signals through a GPS antenna, transmits PPS second pulse signals and time stamp data to the first VDB signal receiving unit and the second VDB signal receiving unit, and transmits real-time aircraft positioning data to the VDB field strength data processing unit.

[0012] The VDB field strength data processing unit calculates the azimuth value Azimuth of the GBAS ground station relative to the aircraft, and obtains the VDB horizontal polarization antenna gain compensation value G according to the VDB horizontal polarization signal power data and the VDB vertical polarization signal power data. ant p and VDB vertical polarization antenna gain compensation value G ant v, determine the signal field strength value Sp of the VDB horizontal polarization signal and the signal field strength value Sv of the VDB vertical polarization signal.

[0013] In one embodiment, the VDB field strength data processing unit includes a first power-to-field strength module, a second power-to-field strength module, a first antenna gain correction calculation module, a second antenna gain correction calculation module, a horizontal polarization antenna directivity data acquisition module, a vertical polarization antenna directivity module and a station azimuth calculation module.

[0014] The station position calculation module receives the real-time aircraft positioning data output by the GPS receiver, converts the WGS-84 coordinates of the GBAS ground station into the Earth-centered Earth-fixed coordinate system ECEF coordinates, and converts the WGS-84 coordinates of the aircraft into the Earth-centered Earth-fixed coordinate system ECEF coordinates;

[0015] The first antenna gain correction amount calculation module and / or the second antenna gain correction amount calculation module calculates the station center northeast celestial ENU coordinates of the GBAS ground station relative to the aircraft according to the geocentric earth-fixed coordinate system ECEF coordinates of the GBAS ground station and the geocentric earth-fixed coordinate system ECEF coordinates of the aircraft, and calculates the azimuth angle value Azimuth of the GBAS ground station relative to the aircraft according to the station center northeast celestial ENU coordinates of the GBAS ground station relative to the aircraft;

[0016] The horizontal polarization antenna directionality data acquisition module acquires the horizontal polarization antenna directionality data headingp;

[0017] The first antenna gain correction calculation module calculates the bearing value bearingp of the GBAS ground station relative to the VDB horizontal polarization antenna pattern, and determines the VDB horizontal polarization antenna gain compensation value G ant p;

[0018] The first power-to-field strength module calculates the signal field strength value Sp of the VDB horizontal polarization signal;

[0019] The vertical polarization antenna directivity data acquisition module acquires the vertical polarization antenna directivity data headingv;

[0020] The second antenna gain correction calculation module calculates the bearing value bearingv of the GBAS ground station relative to the VDB vertical polarization antenna pattern, and determines the VDB vertical polarization antenna gain compensation value G ant v;

[0021] The second power-to-field-strength module calculates the signal field strength value Sv of the VDB vertical polarization signal.

[0022] In one embodiment, the first power-to-field strength module calculates the signal field strength value Sp of the VDB horizontal polarization signal using formula (1):

[0023]

[0024] Where: Sp is the signal field strength value of the VDB horizontal polarization signal,

[0025] P dBw p is the power value in the VDB horizontal polarization signal power data from the first VDB signal receiving unit,

[0026] G ant p is the VDB horizontal polarization antenna gain compensation value,

[0027] Loss cable p is the cable loss value between the receiving antenna and the first VDB signal receiving unit,

[0028] λ is the wavelength of the center frequency of the VDB signal;

[0029] The second power-to-field intensity module calculates the signal field intensity value Sv of the VDB vertical polarization signal using formula (2):

[0030]

[0031] Where: Sv is the signal field strength value of the VDB vertical polarization signal,

[0032] P dBw v is the power value in the VDB vertical polarization signal power data from the second VDB signal receiving unit,

[0033] G ant v is the VDB vertical polarization antenna gain compensation value,

[0034] Loss cable v is the cable loss between the receiving antenna and the second VDB signal receiving unit,

[0035] λ is the center frequency wavelength of the VDB signal.

[0036] In one embodiment, the first VDB signal receiving unit performs envelope demodulation on the VDB horizontal polarization signal transmitted by the GBAS ground station based on the VDB horizontal polarization signal, acquires the VDB horizontal polarization signal transmitted by the GBAS ground station, obtains VDB horizontal polarization signal power data of the VDB signal transmitted by the GBAS ground station, and

[0037] The second VDB signal receiving unit acquires the VDB vertical polarization signal transmitted by the GBAS ground station based on the VDB vertical polarization signal, performs envelope demodulation on the VDB vertical polarization signal transmitted by the GBAS ground station, and obtains VDB vertical polarization signal power data of the VDB signal transmitted by the GBAS ground station.

[0038] In one embodiment, the first VDB signal receiving unit and the second VDB signal receiving unit respectively include a signal preselector, a low noise amplifier, a local oscillator, a mixer, an intermediate frequency amplifier, a low pass filter, an envelope detector and a synchronous measurement module; the signal preselector obtains the VDB horizontal or vertical polarization signal transmitted by the GBAS ground station from the signal from the VDB horizontal or vertical polarization antenna; the obtained VDB horizontal or vertical polarization signal transmitted by the GBAS ground station is amplified by the low noise amplifier and then transmitted to the mixer, and the mixer mixes the signal with the signal generated by the local oscillator to generate The mixed intermediate frequency signal is transmitted to the envelope detector after passing through the intermediate frequency amplifier and the low-pass filter in sequence; the envelope detector performs amplitude detection on the transmitted signal and outputs an envelope voltage value; the synchronous measurement module samples the envelope voltage value output by the envelope detector under the triggering of the PPS second pulse signal of the GPS receiver, obtains the VDB horizontal or vertical polarization signal power data of the VDB signal transmitted by the GBAS ground station based on the time stamp data from the GPS receiver, and transmits the obtained VDB horizontal or vertical polarization signal power data to the VDB field strength data processing unit.

[0039] In one embodiment, the signal preselector is a 6th order Butterworth analog filter; or,

[0040] The local oscillator has an independent constant temperature crystal oscillator; or,

[0041] The envelope detector performs closed-loop control on the gain values ​​of the low noise amplifier and the intermediate frequency amplifier; or,

[0042] The synchronous measurement module uses formula (3) to convert the sampled envelope voltage value into the VDB horizontal or vertical polarization signal power value of the VDB signal transmitted by the GBAS ground station.

[0043]

[0044] Among them, P dBW is the signal power value; A is the envelope voltage value; and R is the matching impedance value at the input end of the synchronous measurement module.

[0045] In one embodiment, the real-time aircraft positioning data of the GPS receiver is synchronized with the VDB time slot signal transmitted by the GBAS ground station.

[0046] In one embodiment, the VDB time slot signal field strength measurement system of the ground-based enhancement system further includes a bus interface unit, which quantizes and encodes the signal field strength value Sp of the VDB horizontal polarization signal and the signal field strength value Sv of the VDB vertical polarization signal received from the VDB field strength processing unit.

[0047] In one embodiment, the VDB horizontally polarized antenna includes two VDB horizontally polarized sub-antennas. When in use, the two VDB horizontally polarized sub-antennas are symmetrically arranged about the vertical tail of the aircraft, and are horizontally installed on the left and right sides of the vertical tail of the aircraft respectively;

[0048] The VDB vertical polarization antenna includes two VDB vertical polarization sub-antennas. When in use, the two VDB vertical polarization sub-antennas are symmetrically and vertically installed on both sides of the belly of the aircraft.

[0049] Beneficial effects of the present invention:

[0050] The VDB time slot signal field strength measurement system of the ground-based augmentation system proposed in the embodiment of the present invention distinguishes different polarization signals through the dual-antenna dual-polarization parallel reception measurement method, realizes the parallel measurement of horizontal polarization and vertical polarization signals, compensates for the attenuation of the entire RF link, calculates the azimuth of the VDB ground transmitting station, compensates for the antenna gain in real time, eliminates the influence of different antennas on the measurement effect, achieves the effect of VDB time slot signal field strength measurement in dynamic scenes, and has the technical advantages of high field strength measurement accuracy, high time synchronization accuracy and dynamic real-time testing. There is no need to use a standard airborne multi-mode receiver MMR in the measurement system, which further reduces the system cost.

[0051] In addition, through remote time synchronization measurement, the VDB signal field strength can be measured in time slots, meeting the measurement requirements of multiple VDB transmitting stations; by real-time calculation of the azimuth of the GBAS ground station relative to the airborne measurement antenna, the antenna gain compensation value is obtained, eliminating the influence of antenna gain on signal reception, and the VDB signal spatial field strength value is obtained, which can be compared with the standard requirement value. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 A principle block diagram of a VDB time slot signal field strength measurement system of a ground-based enhancement system is provided for an embodiment of the present invention;

[0053] Figure 2 A circuit diagram of a signal preselector of a VDB time slot signal field strength measurement system of a ground-based enhancement system is provided for an embodiment of the present invention;

[0054] Figure 3 A working flow chart of a VDB time slot signal field strength measurement system of a ground-based enhancement system is provided for an embodiment of the present invention. DETAILED DESCRIPTION

[0055] To make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. However, those skilled in the art will appreciate that the present invention is not limited to the accompanying drawings and the following embodiments.

[0056] The embodiment of the present invention provides a VDB time slot signal field strength measurement system for a ground-based augmentation system. Figure 1 As shown, the VDB time slot signal field strength measurement system of the ground-based augmentation system is arranged on a calibration aircraft, and includes a VDB horizontal polarization antenna, a first VDB signal receiving unit A, a VDB vertical polarization antenna, a second VDB signal receiving unit B, a GPS antenna, a GPS receiver, a VDB field strength data processing unit and a bus interface unit.

[0057] The GPS receiver 3 receives GPS signals through a GPS antenna, transmits PPS second pulse signals and time stamp data to the first VDB signal receiving unit A and the second VDB signal receiving unit B, and transmits real-time aircraft positioning data to the VDB field strength data processing unit.

[0058] The VDB horizontal polarization antenna is used to receive VDB horizontal polarization signals. The VDB horizontal polarization antenna includes an antenna combiner and two VDB horizontal polarization sub-antennas, which are symmetrically arranged about the vertical tail of the aircraft and are horizontally installed on the left and right sides of the vertical tail of the aircraft, respectively, so that during the flight of the verification aircraft, the VDB horizontal polarization sub-antennas installed on the left and right sides of the vertical tail of the aircraft can receive the signal of the VDB ground station without being blocked by the vertical tail.

[0059] The antenna combiner is used to synthesize the receiving signals of the two VDB horizontal polarization sub-antennas. The output ends of the two VDB horizontal polarization sub-antennas are respectively connected to the input end of the antenna combiner through radio frequency cables, wherein the radio frequency cables connecting the input end of the antenna combiner and the two VDB horizontal polarization sub-antennas are of the same length, so that the transmission delay of the receiving signals from the two VDB horizontal polarization sub-antennas remains consistent, avoiding phase difference and ensuring the best synthesized signal strength and phase parameters. The output end of the antenna combiner is connected to the VDB signal receiving unit A, for example, through a radio frequency cable.

[0060] In this embodiment, the two VDB horizontally polarized sub-antennas are symmetrically installed horizontally on both sides of the aircraft vertical tail, which can eliminate the signal reception blind area caused by the body shielding. Because if the antenna is installed only on one side of the aircraft vertical tail, the other side of the aircraft vertical tail will be shielded by the body, and the antenna cannot normally receive the spatial signal in the shielded area.

[0061] The first VDB signal receiving unit A receives a VDB horizontal polarization signal from the VDB horizontal polarization antenna, obtains the VDB horizontal polarization signal transmitted by the GBAS ground station, performs envelope demodulation on the VDB horizontal polarization signal transmitted by the GBAS ground station, and obtains VDB horizontal polarization signal power data of the VDB signal transmitted by the GBAS ground station.

[0062] The first VDB signal receiving unit A includes a signal preselector 101 , a low noise amplifier 102 , a local oscillator 103 , a mixer 104 , an intermediate frequency amplifier 105 , a low pass filter 106 , an envelope detector 107 and a synchronous measurement module 108 . The signal preselector 101 obtains the VDB horizontal polarization signal transmitted by the GBAS ground station from the signal from the VDB horizontal polarization antenna; the obtained VDB horizontal polarization signal transmitted by the GBAS ground station is amplified by the low noise amplifier 102 and transmitted to the mixer 104, and the mixer 104 mixes the VDB horizontal polarization signal with the signal generated by the local oscillator 103 to generate an intermediate frequency signal; the mixed intermediate frequency signal passes through the intermediate frequency amplifier 105 and the low pass filter 106 in sequence and is transmitted to the envelope detector 107; the envelope detector 107 performs amplitude detection on the transmitted signal and outputs an envelope voltage value; the synchronous measurement module 108 samples the envelope voltage value output by the envelope detector 107 under the triggering of the PPS second pulse signal of the GPS receiver, obtains the VDB horizontal polarization signal power data of the VDB signal transmitted by the GBAS ground station based on the time stamp data from the GPS receiver, and transmits the obtained VDB horizontal polarization signal power data to the VDB field strength data processing unit. Since the synchronous measurement module 108 receives the PPS pulse per second signal to trigger control, the synchronous measurement module 108 is synchronized with the GPS system time.

[0063] Among them, the first VDB signal receiving unit A of the embodiment of the present invention particularly includes a signal preselector 101, because the GBAS ground station is deployed within the airport, and the civil aviation VHF frequency band is shared by a variety of civil aviation radio equipment, such as VHFCOM transceivers, VOR navigation ground stations, LOC navigation ground stations, etc., and at least two VHF COM transceivers are also installed on the verification aircraft. When the airborne VHF COM transceiver transmits a signal, it may cause the RF circuit of the first VDB signal receiving unit A to saturate. In order to avoid the above saturation, it is necessary to pre-select and filter the antenna input signal to obtain the VDB horizontal polarization signal transmitted by the GBAS ground station.

[0064] The signal preselector 101 of the embodiment of the present invention is a 6th order Butterworth analog filter to ensure the signal field strength measurement accuracy. The ripple in the passband of the signal preselector 101 is as flat as possible. The circuit diagram of the signal preselector 101 is as shown in FIG. Figure 2 shown. Figure 2 In the figure, the left side of resistor R0 is the input end, and the right side of inductor L10 is the output end.

[0065] The local oscillator 103 has an independent constant temperature crystal oscillator, which can reduce the temperature drift coefficient of the local oscillator to improve the measurement accuracy of the VDB frequency.

[0066] The envelope detector 107 performs closed-loop control on the gain values ​​of the low noise amplifier 102 and the intermediate frequency amplifier 105 to make the output of the envelope detector 107 as stable as possible.

[0067] The synchronous measurement module 108 samples the envelope voltage value output by the envelope detector 107, triggered by the PPS pulse-per-second signal output by the GPS receiver 3 and synchronized with the VDB signal time slot transmitted by the GBAS ground station. The GPS receiver 3 receives the GPS signal through the GPS antenna, and the PPS pulse-per-second signal output to the synchronous measurement module 108 is strictly synchronized with the GPS time; and the GBAS ground station also implements TDMA time division multiplexing under GPS time synchronization, so the first VDB signal receiving unit A can realize remote synchronous data acquisition. Since the VDB signal transmitted by the GBAS ground station is divided into time slots in units of 62.5 milliseconds, the corresponding time slot frequency is 16Hz, so the output frequency of the PPS pulse-per-second signal output by the GPS receiver 3 is also 16Hz.

[0068] The synchronous measurement module 108 can repeatedly collect / oversample the envelope voltage value output by the envelope detector 107 by synchronous triggering of the PPS second pulse signal to improve the sampling accuracy. Its trigger collection time window is related to the frame structure content of the VDB signal, and the sampled time window coincides with the duration of the frame header training sequence of each time slot of the VDB signal, thereby achieving the effect of stable voltage collection.

[0069] The synchronous measurement module 108 converts the sampled envelope voltage value into the VDB horizontal polarization signal power value of the VDB signal transmitted by the GBAS ground station, and the calculation formula is as follows:

[0070]

[0071] Among them, P dBW is the signal power value; A is the envelope voltage value; and R is the matching impedance value at the input end of the synchronous measurement module 108 .

[0072] The synchronous measurement module 108 obtains the VDB horizontal polarization signal power value of the VDB signal transmitted by the GBAS ground station associated with the sampled envelope voltage value based on the time stamp data from the GPS receiver, and obtains the VDB horizontal polarization signal power data of the VDB signal transmitted by the GBAS ground station.

[0073] The VDB vertical polarization antenna is used to receive VDB vertical polarization signals. The VDB vertical polarization antenna includes an antenna combiner and two VDB vertical polarization sub-antennas, which are installed on the belly of the aircraft and avoid being blocked by other parts of the aircraft.

[0074] The antenna combiner is used to synthesize the receiving signals of the two VDB vertical polarization sub-antennas. The output ends of the two VDB vertical polarization sub-antennas are respectively connected to the input end of the antenna combiner through radio frequency cables, wherein the input end of the antenna combiner and the radio frequency cables connected to the two VDB vertical polarization sub-antennas have the same length, so that the transmission delay of the receiving signals from the two VDB vertical polarization sub-antennas remains consistent, avoiding phase difference and ensuring the best synthesized signal strength and phase parameters; the output end of the antenna combiner is connected to the second VDB signal receiving unit B, for example, through a radio frequency cable.

[0075] In this embodiment, the two VDB vertically polarized sub-antennas are symmetrically and vertically installed on both sides of the belly of the aircraft, which can eliminate the signal reception blind area caused by the shielding of the aircraft body.

[0076] The second VDB signal receiving unit B receives the VDB vertical polarization signal from the VDB vertical polarization antenna, obtains the VDB vertical polarization signal transmitted by the GBAS ground station, performs envelope demodulation on the VDB vertical polarization signal transmitted by the GBAS ground station, and obtains the VDB vertical polarization signal power data of the VDB signal transmitted by the GBAS ground station.

[0077] Similar to the first VDB signal receiving unit A, the second VDB signal receiving unit B also includes a signal preselector 101, a low noise amplifier 102, a local oscillator 103, a mixer 104, an intermediate frequency amplifier 105, a low pass filter 106, an envelope detector 107 and a synchronous measurement module 108. The signal preselector 101 obtains the VDB vertical polarization signal transmitted by the GBAS ground station from the VDB vertical polarization signal from the VDB vertical polarization antenna; the obtained VDB vertical polarization signal transmitted by the GBAS ground station is amplified by the low noise amplifier 102 and transmitted to the mixer 104, and the mixer 104 mixes the signal with the signal generated by the local oscillator 103 to generate an intermediate frequency signal; the mixed intermediate frequency signal is successively transmitted to the envelope after passing through the intermediate frequency amplifier 105 and the low pass filter 106. The envelope detector 107 performs amplitude detection on the transmitted signal and outputs an envelope voltage value; the synchronous measurement module 108 samples the envelope voltage value output by the envelope detector 107 under the triggering of the PPS second pulse signal of the GPS receiver, obtains the VDB vertical polarization signal power data of the VDB signal transmitted by the GBAS ground station based on the time stamp data from the GPS receiver, and transmits the obtained VDB vertical polarization signal power data to the VDB field strength data processing unit.

[0078] The components of the second VDB signal receiving unit B are the same as those of the first VDB signal receiving unit A, and are not described in detail herein.

[0079] The VDB field strength data processing unit includes a first power-to-field strength module 404, a second power-to-field strength module 407, a first antenna gain correction calculation module 402, a second antenna gain correction calculation module 405, a horizontal polarization antenna directivity data acquisition module 403, a vertical polarization antenna directivity module 406 and a station azimuth calculation module 401.

[0080] The VDB field intensity data processing unit receives the VDB horizontal polarization signal power data from the first VDB signal receiving unit A and the VDB vertical polarization signal power data from the second VDB signal receiving unit B through two serial RS232 buses. As mentioned above, the VDB horizontal polarization signal power data and the VDB vertical polarization signal power data are combined with time stamp data, have time tags, and the measurement frequency is 16Hz, which is synchronized with the VDB time slot signal transmitted by the GBAS ground station. However, the VDB horizontal polarization signal power data from the first VDB signal receiving unit A and the VDB vertical polarization signal power data from the second VDB signal receiving unit B have not been compensated for link loss, and the RF cable compensation value from the polarized antenna to the signal receiving unit needs to be considered; at the same time, due to the influence of the amplitude-frequency characteristics of the first VDB signal receiving unit A and the second VDB signal receiving unit B, the receiving unit losses corresponding to different VDB signal center frequencies are also different, and the amplitude-frequency characteristic values ​​of the first VDB signal receiving unit A and the second VDB signal receiving unit B need to be compensated according to the center frequency value of the VDB signal.

[0081] The station position calculation module 401 receives the real-time aircraft positioning data output by the GPS receiver 3 through the serial RS232 bus. The output frequency of the real-time aircraft positioning data is also 16 Hz, with a time tag, and is synchronized with the VDB time slot signal transmitted by the GBAS ground station.

[0082] The station position calculation module 401 converts the WGS-84 coordinates of the GBAS ground station into the Earth-Centered Earth-Fixed (ECEF) coordinates, and the conversion formula is:

[0083]

[0084]

[0085] Where: alt is the WGS-84 coordinate altitude value of the GBAS ground station;

[0086] lat is the WGS-84 coordinate latitude value of the GBAS ground station;

[0087] lon is the WGS-84 coordinate longitude value of the GBAS ground station;

[0088] N is the radius of curvature of the WGS-84 reference ellipsoid;

[0089] f is the extreme oblateness of the WGS-84 ellipsoid;

[0090] a is the major radius of the reference ellipsoid;

[0091] x, y, z are the coordinate values ​​of the Earth-centered Earth-fixed coordinate system ECEF of the GBAS ground station.

[0092] The station position calculation module 401 converts the WGS-84 coordinates of the aircraft into the ECEF coordinates of the Earth-centered Earth-fixed coordinate system, and the conversion formula is:

[0093]

[0094]

[0095] Where: alt0 is the WGS-84 coordinate altitude of the aircraft;

[0096] Lat0 is the WGS-84 coordinate latitude of the aircraft;

[0097] Lon0 is the WGS-84 coordinate longitude value of the aircraft;

[0098] N is the radius of curvature of the WGS-84 reference ellipsoid;

[0099] f is the extreme oblateness of the WGS-84 ellipsoid;

[0100] a is the major radius of the reference ellipsoid;

[0101] x0, y0, z0 are the coordinate values ​​of the aircraft in the Earth-centered Earth-fixed coordinate system ECEF.

[0102] The first antenna gain correction calculation module 402 calculates the northeast celestial ENU coordinates of the GBAS ground station relative to the aircraft based on the ECEF coordinates of the earth-centered earth-fixed coordinate system of the GBAS ground station and the ECEF coordinates of the earth-centered earth-fixed coordinate system of the aircraft:

[0103]

[0104]

[0105] According to the northeastern ENU coordinates of the GBAS ground station relative to the aircraft, calculate the azimuth angle value Azimuth of the GBAS ground station relative to the aircraft:

[0106]

[0107] The horizontal polarization antenna directivity data acquisition module 403 is used to acquire the horizontal polarization antenna directivity data headingp from the airborne inertial navigation device, wherein the horizontal polarization antenna directivity data headingp is the real-time heading data of the aircraft.

[0108] The first antenna gain correction calculation module 402 calculates the bearing value bearingp of the GBAS ground station relative to the VDB horizontal polarization antenna pattern:

[0109] bearingp=Azimuth-headingp (9).

[0110] The first antenna gain correction calculation module 402 queries the antenna directivity table according to the bearing value bearingp of the GBAS ground station relative to the VDB horizontal polarization antenna pattern to determine the VDB horizontal polarization antenna gain compensation value G ant p:

[0111] bearingp→G ant p (10),

[0112] The antenna orientation table is the azimuth value bearingp of the VDB horizontal polarization antenna and the gain value G of the VDB horizontal polarization antenna. ant The corresponding relationship table of p.

[0113] The first power-to-field strength module 404 calculates the signal field strength value Sp of the VDB horizontal polarization signal:

[0114]

[0115] Where: Sp is the signal field strength value of the VDB horizontal polarization signal;

[0116] P dBw p is the power value in the VDB horizontal polarization signal power data from the first VDB signal receiving unit A;

[0117] G ant p is the VDB horizontal polarization antenna gain compensation value;

[0118] Loss cable p is the cable loss value between the receiving antenna and the first VDB signal receiving unit A;

[0119] λ is the center frequency wavelength of the VDB signal.

[0120] As mentioned above, the first antenna gain correction calculation module 402 calculates the northeast celestial body ENU coordinates of the GBAS ground station relative to the aircraft based on the ECEF coordinate values ​​of the GBAS ground station's geocentric Earth-fixed coordinate system and the ECEF coordinate values ​​of the aircraft's geocentric Earth-fixed coordinate system. Of course, the above calculation can also be performed by the second antenna gain correction calculation module 405.

[0121] The vertical polarization antenna directivity data acquisition module 406 is used to acquire the vertical polarization antenna directivity data headingv from the airborne inertial navigation device, wherein the vertical polarization antenna directivity data headingv is the real-time heading data of the aircraft.

[0122] The second antenna gain correction calculation module 405 calculates the bearing value bearingv of the GBAS ground station relative to the VDB vertical polarization antenna pattern:

[0123] bearingv=Azimuth-headingv (9).

[0124] The second antenna gain correction calculation module 405 queries the antenna directivity table according to the bearing value bearingv of the GBAS ground station relative to the VDB vertical polarization antenna pattern to determine the VDB vertical polarization antenna gain compensation value G ant v:

[0125] bearingv→G ant v (10),

[0126] The antenna orientation table is the azimuth value bearingv of the VDB vertical polarization antenna and the gain value G of the VDB vertical polarization antenna. ant v's correspondence table.

[0127] The second power-to-field strength module 407 calculates the signal field strength value Sv of the VDB vertical polarization signal:

[0128]

[0129] Where: Sv is the signal field strength value of the VDB vertical polarization signal;

[0130] P dBw v is the power value in the VDB vertical polarization signal power data from the second VDB signal receiving unit B;

[0131] G ant v is the VDB vertical polarization antenna gain compensation value;

[0132] Loss cable v is the cable loss value between the receiving antenna and the second VDB signal receiving unit B;

[0133] λ is the center frequency wavelength of the VDB signal.

[0134] The bus interface unit is an ARINC429 bus interface unit. After receiving the VDB horizontal polarization signal field strength value and the VDB vertical polarization signal field strength value from the VDB field strength processing unit, the received data is quantized and encoded, and the standard ARINC429 Label data is formed by framing, which can be adapted to other external avionics equipment. Since the ARINC429 Label word is 32 bits, it includes the Label number, SDI address bit, SSM status bit and parity check, etc. The quantization bit number used here is 18-bit quantization.

[0135] In the embodiment of the present invention, the signal receiving frequency band of the VDB horizontal polarization antenna and the VDB vertical polarization antenna is 108MHz-118MHz. The first VDB signal receiving unit A and the second VDB signal receiving unit B are implemented by broadband RF front end + FPGA, wherein the FPGA adopts Xilinx chip with an internal integrated ARM CPU processor hard core.

[0136] The VDB time slot signal field strength measurement system of the ground-based augmentation system of the embodiment of the present invention distinguishes different polarization signals through dual-antenna dual-polarization parallel reception measurement, thereby achieving the advantages of parallel measurement of horizontal polarization and vertical polarization signals. The working process is as follows: Figure 3 shown.

[0137] The VDB horizontal polarization antenna receives the VDB horizontal polarization signal; the first VDB signal receiving unit A receives the VDB horizontal polarization signal from the VDB horizontal polarization antenna, performs envelope demodulation on the VDB horizontal polarization signal transmitted by the GBAS ground station, obtains the VDB horizontal polarization signal transmitted by the GBAS ground station, and obtains the VDB horizontal polarization signal power data of the VDB signal transmitted by the GBAS ground station. At the same time, the VDB vertical polarization antenna receives the VDB vertical polarization signal; the second VDB signal receiving unit B receives the VDB vertical polarization signal from the VDB vertical polarization antenna, obtains the VDB vertical polarization signal transmitted by the GBAS ground station, performs envelope demodulation on the VDB vertical polarization signal transmitted by the GBAS ground station, and obtains the VDB vertical polarization signal power data of the VDB signal transmitted by the GBAS ground station.

[0138] The VDB field strength data processing unit receives the VDB horizontal polarization signal power data from the first VDB signal receiving unit A and the VDB vertical polarization signal power data from the second VDB signal receiving unit B, calculates the azimuth value Azimuth of the GBAS ground station relative to the aircraft, and obtains the VDB horizontal polarization antenna gain compensation value G ant p and VDB vertical polarization antenna gain compensation value G ant v, determine the signal field strength value Sp of the VDB horizontal polarization signal and the signal field strength value Sv of the VDB vertical polarization signal.

[0139] The bus interface unit quantizes and encodes the signal field strength value Sp of the VDB horizontal polarization signal and the signal field strength value Sv of the VDB vertical polarization signal received from the VDB field strength processing unit, and transmits them.

[0140] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or a combination thereof: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0141] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0142] The above is an explanation of the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A VDB time slot signal field strength measurement system for a ground-based augmentation system, characterized in that: It includes a VDB horizontal polarization antenna, a first VDB signal receiving unit, a VDB vertical polarization antenna, a second VDB signal receiving unit, a VDB field strength data processing unit and a GPS receiver. The VDB horizontal polarization antenna receives a VDB horizontal polarization signal; The first VDB signal receiving unit receives a VDB horizontal polarization signal from the VDB horizontal polarization antenna to obtain VDB horizontal polarization signal power data of the VDB signal transmitted by the GBAS ground station; The VDB vertical polarization antenna receives a VDB vertical polarization signal; The second VDB signal receiving unit receives a VDB vertical polarization signal from the VDB vertical polarization antenna to obtain VDB vertical polarization signal power data of the VDB signal transmitted by the GBAS ground station; The GPS receiver receives GPS signals through the GPS antenna, transmits the PPS pulse-per-second signal and time-scale data to the first VDB signal receiving unit and the second VDB signal receiving unit, and transmits the real-time aircraft positioning data to the VDB field strength data processing unit; The VDB field strength data processing unit calculates the azimuth value Azimuth of the GBAS ground station relative to the aircraft, and obtains the VDB horizontal polarization antenna gain compensation value G according to the VDB horizontal polarization signal power data and the VDB vertical polarization signal power data. ant p and VDB vertical polarization antenna gain compensation value G ant v, determine the signal field strength value Sp of the VDB horizontal polarization signal and the signal field strength value Sv of the VDB vertical polarization signal.

2. The VDB time slot signal field strength measurement system of the ground-based augmentation system according to claim 1, characterized in that: The VDB field strength data processing unit includes a first power-to-field strength module, a second power-to-field strength module, a first antenna gain correction calculation module, a second antenna gain correction calculation module, a horizontal polarization antenna directivity data acquisition module, a vertical polarization antenna directivity module and a station azimuth calculation module. The station position calculation module receives the real-time aircraft positioning data output by the GPS receiver, converts the WGS-84 coordinates of the GBAS ground station into the Earth-centered Earth-fixed coordinate system ECEF coordinates, and converts the WGS-84 coordinates of the aircraft into the Earth-centered Earth-fixed coordinate system ECEF coordinates; The first antenna gain correction amount calculation module and / or the second antenna gain correction amount calculation module calculates the station center northeast celestial ENU coordinates of the GBAS ground station relative to the aircraft according to the geocentric earth-fixed coordinate system ECEF coordinates of the GBAS ground station and the geocentric earth-fixed coordinate system ECEF coordinates of the aircraft, and calculates the azimuth angle value Azimuth of the GBAS ground station relative to the aircraft according to the station center northeast celestial ENU coordinates of the GBAS ground station relative to the aircraft; The horizontal polarization antenna directionality data acquisition module acquires the horizontal polarization antenna directionality data headingp; The first antenna gain correction calculation module calculates the bearing value bearingp of the GBAS ground station relative to the VDB horizontal polarization antenna pattern, and determines the VDB horizontal polarization antenna gain compensation value G ant p; The first power-to-field strength module calculates the signal field strength value Sp of the VDB horizontal polarization signal; The vertical polarization antenna directivity data acquisition module acquires the vertical polarization antenna directivity data headingv; The second antenna gain correction calculation module calculates the bearing value bearingv of the GBAS ground station relative to the VDB vertical polarization antenna pattern, and determines the VDB vertical polarization antenna gain compensation value G ant v; The second power-to-field-strength module calculates the signal field strength value Sv of the VDB vertical polarization signal.

3. The VDB time slot signal field strength measurement system of the ground-based augmentation system according to claim 2, characterized in that: The first power-to-field strength module uses formula (1) to calculate the signal field strength value Sp of the VDB horizontal polarization signal: Where: Sp is the signal field strength value of the VDB horizontal polarization signal, P dBw p is the power value in the VDB horizontal polarization signal power data from the first VDB signal receiving unit, G ant p is the VDB horizontal polarization antenna gain compensation value, Loss cable p is the cable loss value between the receiving antenna and the first VDB signal receiving unit, λ is the wavelength of the center frequency of the VDB signal; The second power-to-field intensity module calculates the signal field intensity value Sv of the VDB vertical polarization signal using formula (2): Where: Sv is the signal field strength value of the VDB vertical polarization signal, P dBw v is the power value in the VDB vertical polarization signal power data from the second VDB signal receiving unit, G ant v is the VDB vertical polarization antenna gain compensation value, Loss cable v is the cable loss between the receiving antenna and the second VDB signal receiving unit, λ is the center frequency wavelength of the VDB signal.

4. The VDB time slot signal field strength measurement system of the ground-based augmentation system according to claim 1, characterized in that: The first VDB signal receiving unit performs envelope demodulation on the VDB horizontal polarization signal transmitted by the GBAS ground station based on the VDB horizontal polarization signal, acquires the VDB horizontal polarization signal transmitted by the GBAS ground station, and obtains VDB horizontal polarization signal power data of the VDB signal transmitted by the GBAS ground station; and The second VDB signal receiving unit acquires the VDB vertical polarization signal transmitted by the GBAS ground station based on the VDB vertical polarization signal, performs envelope demodulation on the VDB vertical polarization signal transmitted by the GBAS ground station, and obtains VDB vertical polarization signal power data of the VDB signal transmitted by the GBAS ground station.

5. The VDB time slot signal field strength measurement system of the ground-based augmentation system according to claim 4, characterized in that: The first VDB signal receiving unit and the second VDB signal receiving unit respectively include a signal preselector, a low noise amplifier, a local oscillator, a mixer, an intermediate frequency amplifier, a low pass filter, an envelope detector and a synchronous measurement module; the signal preselector obtains the VDB horizontal or vertical polarization signal transmitted by the GBAS ground station from the signal from the VDB horizontal or vertical polarization antenna; the obtained VDB horizontal or vertical polarization signal transmitted by the GBAS ground station is amplified by the low noise amplifier and then transmitted to the mixer, and the mixer mixes the signal with the signal generated by the local oscillator to generate an intermediate frequency signal; the mixed intermediate frequency signal is sequentially transmitted to the envelope detector after passing through the intermediate frequency amplifier and the low pass filter; the envelope detector performs amplitude detection on the transmitted signal and outputs an envelope voltage value; The synchronous measurement module samples the envelope voltage value output by the envelope detector under the triggering of the PPS second pulse signal of the GPS receiver, obtains the VDB horizontal or vertical polarization signal power data of the VDB signal transmitted by the GBAS ground station based on the time stamp data from the GPS receiver, and transmits the obtained VDB horizontal or vertical polarization signal power data to the VDB field strength data processing unit.

6. The VDB time slot signal field strength measurement system of the ground-based augmentation system according to claim 5, characterized in that: The signal preselector is a 6th order Butterworth analog filter; or, The local oscillator has an independent constant temperature crystal oscillator; or, The envelope detector performs closed-loop control on the gain values ​​of the low noise amplifier and the intermediate frequency amplifier; or, The synchronous measurement module uses formula (3) to convert the sampled envelope voltage value into the VDB horizontal or vertical polarization signal power value of the VDB signal transmitted by the GBAS ground station. Among them, P dBW is the signal power value; A is the envelope voltage value; and R is the matching impedance value at the input end of the synchronous measurement module.

7. The VDB time slot signal field strength measurement system of the ground-based augmentation system according to claim 1, characterized in that: The real-time aircraft positioning data of the GPS receiver is synchronized with the VDB time slot signal transmitted by the GBAS ground station.

8. The VDB time slot signal field strength measurement system of the ground-based augmentation system according to claim 1, characterized in that: The VDB time slot signal field strength measurement system of the ground-based enhancement system also includes a bus interface unit, which quantizes and encodes the signal field strength value Sp of the VDB horizontal polarization signal and the signal field strength value Sv of the VDB vertical polarization signal received from the VDB field strength data processing unit.

9. The VDB time slot signal field strength measurement system of the ground-based augmentation system according to claim 1, characterized in that: The VDB horizontal polarization antenna includes two VDB horizontal polarization sub-antennas. When in use, the two VDB horizontal polarization sub-antennas are symmetrically arranged about the vertical tail of the aircraft, and are horizontally installed on the left and right sides of the vertical tail of the aircraft respectively; The VDB vertical polarization antenna includes two VDB vertical polarization sub-antennas. When in use, the two VDB vertical polarization sub-antennas are symmetrically and vertically installed on both sides of the belly of the aircraft.

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