Radio altimetry system capable of being loaded on aircraft
The radio altimeter system, which combines FMCW and UWB radar technologies, solves the problem of susceptibility to interference in existing technologies and achieves accurate measurement at low altitudes and aircraft safety assurance.
Patent Information
- Application Number
- CN202510293655.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2024-03-19
- Filing Date
- 2025-03-13
- Publication Date
- 2025-09-19
AI Technical Summary
Existing radio altimeter systems are susceptible to interference in the C-band and are unable to resist low-power interference in a wide bandwidth and high-power interference at specific frequencies, resulting in inaccurate measurements, especially at low altitudes.
It uses a combination of FMCW radar technology and UWB radar technology. By merging electronic circuit systems, it takes advantage of the high operating power of the FMCW subsystem and the frequency bandwidth of the UWB subsystem, combined with a barometric altimeter and an inertial measurement unit, to provide complementary altitude values to resist interference and improve measurement accuracy.
While resisting various interferences, it improves the measurement accuracy and reliability at low altitudes, ensuring flight safety, especially the stability of operations in low visibility conditions.
Smart Images
Figure CN120669238A_ABST
Abstract
Description
Technical Field
[0001] The field of the invention is that of altimeters.
[0002] More precisely, the invention relates to a radio altimeter system capable of being mounted on an aircraft and capable of providing the altitude of said aircraft above ground level.
[0003] The height above ground level is also called the altitude AGL. This height is usually measured in feet (one foot equals 0.3048 meters, and its symbol is "ft"). Background Art
[0004] Radio altimeter systems, also called "radio altimeters" or "radar altimeters", are used in civil and military aviation.
[0005] These radio altimeter systems are used in particular for automatic flight phases or critical flight phases, such as approach, landing (especially with flare and rollout maneuvers) and take-off. In particular, the flare maneuver is completely dependent on the radio altimeter.
[0006] The altitude above ground level (altitude AGL) measurements provided by the radio altimeter can be used for various functions performed in the aircraft:
[0007] - Controlling the aircraft, in particular for (automatic or manual) landing and take-off maneuvers;
[0008] - No loss of control impact protection (or for controlled flight into terrain CFIT);
[0009] - Improved pilot awareness through cockpit screens;
[0010] - Activate wind shear monitoring systems, for example, below 2300 ft (i.e., 701.04 m);
[0011] - inhibit dangerous maneuvers close to the ground;
[0012] -Generates alerts and warnings in the cockpit;
[0013] -etc.
[0014] The prior art discloses various types of radio altimeters, the general principle of which is to measure altitude by measuring the propagation time of a transmitted and received radio signal after reflection from the ground.
[0015] In particular, most civilian aircraft use radio altimeters based on frequency modulated continuous wave radar technology (known as FMCW radar technology). In the remainder of this specification, this type of radio altimeter will be referred to as an "FMCW radio altimeter." To ensure safety and correct operation, two or three FMCW radio altimeters are typically installed on an aircraft.
[0016] FMCW radio altimeters use the [4.2 GHz; 4.4 GHz] frequency bands, which are contained within the C-band. The C-band is of great importance for telecommunications, but is also highly congested and susceptible to interference. As a result, frequency bands adjacent to those used by FMCW radio altimeters are increasingly susceptible to interference. As a result, FMCW radio altimeters can be subject to external common-mode faults caused by interference, leading to operational limitations (e.g., for low-visibility operations) and making single pilot (SPO) flight techniques difficult to achieve.
[0017] The advantage of FMCW radio altimeter is that it operates at relatively high power, thus having good immunity to interference (especially low-power interference generated over a wide frequency band). However, it operates on a single frequency band and is therefore sensitive to high-power interference located on specific frequencies.
[0018] Therefore, it is desirable to provide a solution (radio altimetry system) to resist various interferences (that is, both low-power interferences generated over a wide frequency band and high-power interferences located at specific frequencies).
[0019] Furthermore, since the flare operation is triggered and performed below 100 ft AGL (ie, 30.48 m above ground level), it is also expected that the provided solution (radio altimeter system) can enhance measurements at low altitudes (eg, below 100 ft AGL). Summary of the Invention
[0020] This article proposes a radio altimeter system, which can be loaded on an aircraft and can provide the height of the aircraft above the ground level. The radio altimeter system includes:
[0021] a first subsystem based on frequency modulated continuous wave radar technology, known as FMCW radar technology, which provides a first altitude value of the aircraft above ground level;
[0022] a second subsystem based on ultra-wideband radar technology, known as UWB radar technology, which provides a second altitude value of the aircraft above ground level; and
[0023] - an electronic circuit system, referred to as a merged electronic circuit system, configured to:
[0024] comparing the second altitude value to a predetermined altitude threshold from ground level;
[0025] • if the second altitude value is less than or equal to a predetermined altitude threshold above ground level, determining a combined altitude value for the aircraft above ground level based on the first altitude value and the second altitude value; and
[0026] If the second altitude value is greater than a predetermined altitude threshold above ground level, determining a combined altitude value for the aircraft above ground level based on the first altitude value without taking the second altitude value into account.
[0027] Therefore, the proposed radio altimeter system includes two subsystems based on radar technology (the two subsystems differ in their robustness against interference but are complementary), namely, a first subsystem based on FMCW radar technology (hereinafter referred to as the “FMCW subsystem”) and a second subsystem based on UWB (Ultra-Wideband) radar technology (hereinafter referred to as the “UWB subsystem”). The proposed radio altimeter system also includes a merging electronic circuit system that can provide a merged altitude value above the ground level based on the first altitude value and the second altitude value above the ground level provided by the FMCW subsystem and the UWB subsystem, respectively.
[0028] In this way, the proposed radio altimeter system is resistant to both low-power interference generated over a wide frequency band and high-power interference located at specific frequencies. Indeed, as mentioned above, the FMCW subsystem has the advantage of operating at relatively high power and a limited frequency band, thus offering good resistance to low-power interference generated over an ultra-wideband band. In a complementary manner, the UWB subsystem has the advantage of operating over an ultra-wideband band and at relatively low power, thus offering good resistance to high-power interference located at specific frequencies.
[0029] Furthermore, the UWB subsystem uses UWB pulses that introduce dissimilarity. These pulses are very short (e.g., 2 ns) and have a large bandwidth (e.g., 500 MHz), allowing them to provide similar accuracy levels as the FMCW subsystem and thus be compatible with flattening operations.
[0030] The UWB frequency band used by the UWB subsystem is less than 10 GHz, which means it is insensitive to attenuation caused by heavy rain and fog. This is very important for critical operations in low visibility conditions (heavy rain, fog).
[0031] Furthermore, the incorporated electronic circuitry ensures that the second altitude value provided by the UWB subsystem is only considered if it is less than or equal to a predetermined altitude threshold above ground level. Thus, the proposed radio altimetry system can enhance measurements at low altitudes (i.e., below a predetermined altitude threshold above ground level).
[0032] It should be noted that the UWB subsystem is very low power (e.g., limited to a maximum of -41.3 dBm / MHz), which means that the range is limited to a few tens of meters. However, this is sufficient for flare operations starting between approximately 35 ft and 80 ft (average 50 ft), and is also sufficient for rollout operations and takeoff operations.
[0033] According to a particular embodiment, the first subsystem is configured to use a first frequency band and the second subsystem is configured to use at least one second frequency band different from the first frequency band.
[0034] According to a specific embodiment, the first frequency band is the [4.2 GHz; 4.4 GHz] band, and the second frequency band is contained within the [3.1 GHz; 10.6 GHz] band.
[0035] According to a particular embodiment, the second subsystem is configured to perform frequency hopping between at least two frequency bands different from the first frequency band.
[0036] According to a particular embodiment, the second subsystem is configured to use at least one pulse pattern that is different from the waveform used by the first subsystem.
[0037] According to a particular embodiment, the first subsystem and the second subsystem share at least one element belonging to the group consisting of an antenna and a coaxial cable.
[0038] According to a specific embodiment, the merged electronic circuit system is also configured to select one of the first height value and the second height value based on at least one selection parameter to form a merged value when the deviation between the first height value and the second height value is greater than a predetermined height deviation threshold.
[0039] According to a particular embodiment, the at least one selection parameter belongs to the group consisting of:
[0040] - barometric altitude provided by a barometric altimeter;
[0041] - Inertial altitude provided by the inertial measurement unit; and
[0042] - The stored height resulting from the storage of the previously merged value.
[0043] According to a specific embodiment, selecting one of the first height value and the second height value based on the at least one selection parameter comprises:
[0044] - determining a reference altitude based on the at least one selected parameter; and
[0045] - Selecting a height value closest to the reference height from the first height value and the second height value.
[0046] According to a particular embodiment, the predetermined height threshold from ground level is between 25 meters and 35 meters, and in a particular implementation, the predetermined height threshold is equal to 100 ft (ie 30.48 m).
[0047] This document also proposes an aircraft comprising the radio altimeter system presented in any of the above embodiments. BRIEF DESCRIPTION OF THE DRAWINGS
[0048] The above and other features of the present invention will become more apparent upon reading the following description of at least one exemplary embodiment, which description is given with reference to the accompanying drawings, in which:
[0049] Figure 1 Schematically shows a side view of an aircraft equipped with a radio altimeter system;
[0050] Figure 2 Schematically illustrates a radio altimeter system in one embodiment;
[0051] Figure 3 schematically illustrates an example of a hardware architecture for a combined electronic circuit system included within a radio altimetering system in one embodiment; and
[0052] Figure 4 An example of a merging algorithm performed by the merging electronic circuitry in one embodiment is schematically illustrated. DETAILED DESCRIPTION
[0053] Figure 1 A side view of an aircraft 100 equipped with a radio altimeter system 101 is schematically shown.
[0054] The radio altimeter system 101 is an onboard electronic device. For example, the radio altimeter system forms part of the electronic circuit system of the avionics equipment of the aircraft 100. The location of the radio altimeter system in the aircraft may vary depending on the aircraft model.
[0055] Figure 2 The radio altimetry system 101 in one embodiment is schematically illustrated, in which the radio altimetry system comprises a first radio altimetry subsystem 201 , a second radio altimetry subsystem 202 and a merged electronic circuit system 203 .
[0056] The first subsystem 201 (hereinafter also referred to as the "FMCW subsystem") (and Figure 2 The FMCW subsystem 201 (denoted as "RAFMCW") is based on frequency modulated continuous wave radar technology (also known as FMCW radar technology). A first subsystem provides a first altitude value V1 of aircraft 100 above ground level. FMCW subsystem 201 is configured to utilize a first frequency band providing a first communication channel. In one embodiment, this is the [4.2 GHz; 4.4 GHz] frequency band.
[0057] The second subsystem 202 (hereinafter also referred to as "UWB subsystem") (and Figure 2 The second subsystem 202 (denoted as "RA UWB") is based on ultra-wideband radar technology (referred to as UWB radar technology). The second subsystem provides a second altitude value V2 of the aircraft 100 above the ground. The UWB subsystem 202 is configured to use at least one second frequency band different from the first frequency band. In one embodiment, the UWB subsystem 202 is configured to perform frequency hopping between at least two frequency bands different from the first frequency band (each frequency band providing a different communication channel). In one embodiment, the frequency bands between which frequency hopping is performed are included in the [3.1 GHz; 10.6 GHz] frequency band, and the width of each frequency band is equal to 500 MHz. For example, the UWB subsystem 202 monitors the interference received in these frequency bands and selects the frequency band with the least interference. In another example, the UWB subsystem 202 itself determines a suitable (in terms of interference) 500 MHz frequency band within the allowed frequency range (e.g., [3.1 GHz; 10.6 GHz]).
[0058] Therefore, FMCW subsystem 201 and UWB subsystem 202 utilize different frequency bands and, therefore, complementary communication channels, thereby achieving an appropriate level of robustness against all RF (radio frequency) threats. This complementarity improves the availability and integrity of the data (altitude values) provided by the radio altimeter system. Indeed, as described in detail below, if one of the first altitude value V1 and the second altitude value V2 is lost, the other can still be used, thereby improving availability. If the two values disagree, an alarm can be triggered, thereby improving integrity.
[0059] In one embodiment, UWB subsystem 202 is configured to use at least one pulse pattern that is different from the waveform used by FMCW subsystem 201. The introduced dissimilarities (e.g., frequency hopping and / or code and / or timing) make radio altimeter system 101 more resilient to data security threats and multipath.
[0060] In one embodiment, the FMCW subsystem 201 and the UWB subsystem 202 share an antenna (eg, a passive C-band microstrip patch antenna) and / or a coaxial cable, which can reduce the implementation cost of the radio altimeter system 101 .
[0061] The merged electronic circuit system 203 receives the first height value V1 and the second height value V2 and selects a value based on these values and one or more selection parameters P1, P2 and P3 (see below for Figure 4 Description) generates a combined height value VC from the ground level.
[0062] Figure 4 An example of a merging algorithm executed by the merging electronic circuit system 203 in one embodiment of the present invention is schematically illustrated.
[0063] In step 401 , the merged electronic circuit system 203 obtains a first height value V1 and a second height value V2 generated by the FMCW subsystem 201 and the UWB subsystem 202 , respectively.
[0064] In step 402, the combined electronic circuit system 203 compares the second altitude value V2 to a first predetermined altitude threshold S1 above ground level. For example, step 402 may include performing the following test: "V2 ≤ S1?" In one embodiment, the first predetermined threshold S1 is between 25 meters and 35 meters. In one specific embodiment, the first predetermined threshold is equal to 100 ft (i.e., 30.48 m).
[0065] If the second altitude value V2 is greater than the first predetermined threshold value S1 (the answer to the test in step 402 is "no"), the merged electronic circuit system 203 performs step 404, in which the merged electronic circuit system determines a merged altitude value VC based on the first altitude value V1 and without taking into account the second altitude value V2 (VC=f(V1)). In a specific embodiment of step 404, the merged altitude value VC is equal to the first altitude value V1. In other words, when the value of the second altitude value V2 is greater than the first threshold value S1 (for example, 100 ft), the second altitude value is screened. In fact, it is believed that UWB technology only involves low-energy signal pulses, which cannot measure altitudes above this first threshold. However, if the UWB subsystem 202 provides a second altitude value V2 that is greater than the first threshold value S1, it is considered that this value V2 may be unreliable.
[0066] If the second height value V2 is less than or equal to the first predetermined threshold S1 (the answer to the test in step 402 is "yes"), the merged electronic circuit system 203 performs step 403, in which the merged electronic circuit system determines a merged height value VC (VC=f(V1, V2)) based on the first height value V1 and the second height value V2.
[0067] At the end of step 403 or 404, the merging electronic circuit system 203 executes step 405, in which the merging electronic circuit system stores the merged height value VC so that it can be used in subsequent iterations of the merging algorithm just described (returning to step 401; for example, the merging electronic circuit system 203 obtains the first height value V1 and the second height value V2 every 50 ms).
[0068] exist Figure 4 In one particular embodiment shown, step 403 itself includes steps 403a to 403f.
[0069] In step 403a, the merged electronic circuit system 203 compares the deviation between the first height value V1 and the second height value V2 with a second predetermined height deviation threshold S2. For example, step 403a includes performing the following test: "|V1-V2|≤S2?".
[0070] If the deviation between the first height value V1 and the second height value V2 is less than or equal to the second predetermined threshold value S2 (the answer to the test in step 403a is "yes", meaning that there is no significant difference between V1 and V2), the merging electronic circuit system 203 performs step 403b, in which the merging electronic circuit system determines a merged height value VC as the combination of the first height value V1 and the second height value V2. For example, VC is the average of V1 and V2. In one variation, VC is equal to V1. In another variation, VC is equal to V2.
[0071] If the deviation between the first height value V1 and the second height value V2 is greater than a second predetermined threshold value S2 (the answer to the test in step 403a is "no", meaning that there is a significant difference between V1 and V2), the merged electronic circuit system 203 performs step 403c, in which the merged electronic circuit system obtains a reference height Aref based on one or more selected parameters, such as:
[0072] - barometric altitude provided by the barometric altimeter ( Figure 2 Parameter P1 in
[0073] - Inertial altitude provided by the inertial measurement unit ( Figure 2 Parameter P2 in ); and
[0074] - the storage height resulting from the storage of the previous merged value VC ( Figure 2 Parameter P3 in ).
[0075] In one embodiment, the stored altitude (P3) is used only to activate the inertial altitude (P2) and the pressure altitude (P1), which are relative altitudes and must therefore be referenced to the real altitude (relative to the ground). This real altitude corresponds, for example, to the altitude at which there was no significant difference between the two altitude values V1 and V2 for the last time, i.e., to the stored altitude (P3).
[0076] At the end of step 403c, the merging electronic circuit system 203 performs step 403d and one of steps 403e and 403f, thereby selecting the altitude value closest to the reference altitude Aref from among the first altitude value V1 and the second altitude value V2 (to form the merged value VC). In this way, using one or more of the parameters P1, P2, and P3 can help identify and thus improve the continuity of the radio altimeter system 101.
[0077] More specifically, in step 403 d , the merged electronic circuit system 203 performs the following test: “|V1−Aref|≤|V2−Aref|?”.
[0078] If the first height value V1 is closest to the reference height Aref (the answer to the test in step 403d is “yes”), the merged electronic circuit system 203 selects the first height value V1 as the merged value VC (VC=V1) in step 403e.
[0079] If the second height value V2 is closest to the reference height Aref (the answer to the test in step 403d is “No”), the merged electronic circuit system 203 selects the second height value V2 as the merged value VC (VC=V2) in step 403f.
[0080] Figure 3 An example of a hardware architecture of the combined electronic circuit system 203 included in the radio altimeter system 101 is schematically shown. In this example, the combined electronic circuit system 203 comprises the following items connected via a communication bus 310: a processor or CPU (Central Processing Unit) 301; a random access memory RAM 302; a read-only memory ROM 303, such as a flash memory; a data storage device such as a hard disk drive (HDD) or a storage medium reader such as a secure digital (SD) card reader 304; and at least one communication interface 305, which allows the combined electronic circuit system 203 to interact with the avionics equipment of the aircraft 100.
[0081] The processor 301 is capable of executing instructions loaded into the RAM 302 from the ROM 303, from an external memory (not shown), from a storage medium (such as an SD card), or from a communication network (not shown). When the combined electronic circuit system 203 is powered on, the processor 301 is capable of reading the instructions from the RAM 302 and executing them. These instructions form a computer program that causes the processor 301 to implement the actions, steps, and algorithms described herein.
[0082] Therefore, all or part of the actions, steps, and algorithms described herein can be implemented in software form by executing an instruction set using a programmable machine (such as a digital signal processor (DSP) or a microcontroller), or in hardware form by a machine or a dedicated component (chip) or a dedicated component group (chip group) (such as a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC). In general, the combined electronic circuit system 203 is designed and configured to implement the actions, steps, and algorithms described herein.
Claims
1. A radio altimeter system (101), capable of being mounted on an aircraft (100) and capable of providing the height of the aircraft above ground level, the radio altimeter system comprising: - a first subsystem (201) based on frequency modulated continuous wave radar technology, known as FMCW radar technology, providing a first altitude value (V1) of the aircraft above ground level; - a second subsystem (202) based on ultra-wideband radar technology, also known as UWB radar technology, providing a second altitude value (V2) of the aircraft above ground level; and - an electronic circuit system (203), referred to as a merged electronic circuit system, configured to perform the following operations: comparing said second altitude value to a predetermined altitude threshold from ground level; determining a combined altitude value (VC) of the aircraft above ground level based on the first altitude value and the second altitude value if the second altitude value is less than or equal to the predetermined altitude threshold above ground level; as well as • If the second altitude value is greater than the predetermined altitude threshold above ground level, determining a combined altitude value (VC) of the aircraft above ground level based on the first altitude value without taking into account the second altitude value.
2. The radio altimeter system according to claim 1, wherein: The first subsystem (201) is configured to use a first frequency band, and wherein the second subsystem (202) is configured to use at least one second frequency band different from the first frequency band.
3. The radio altimeter system according to claim 2, wherein: The first frequency band is a [4.2 GHz; 4.4 GHz] frequency band, and wherein the second frequency band is included in a [3.1 GHz; 10.6 GHz] frequency band.
4. The radio altimeter system according to any one of claims 2 and 3, wherein: The second subsystem (202) is configured to perform frequency hopping between at least two frequency bands different from the first frequency band.
5. The radio altimeter system (101) according to any one of claims 1 to 4, wherein: The second subsystem (202) is configured to use at least one pulse pattern that is different from the waveform used by the first subsystem (201).
6. The radio altimeter system (101) according to any one of claims 1 to 5, wherein: The first radio subsystem and the second radio subsystem (201, 202) share at least one element belonging to the group consisting of an antenna and a coaxial cable.
7. The radio altimeter system (101) according to any one of claims 1 to 6, wherein: The merged electronic circuit system (203) is further configured to select one of the first height value and the second height value based on at least one selection parameter to form the merged value when a deviation between the first height value and the second height value is greater than a predetermined height deviation threshold.
8. The radio altimeter system (101) according to claim 7, wherein: The at least one selection parameter belongs to the group consisting of: - barometric altitude provided by a barometric altimeter; - Inertial altitude provided by the inertial measurement unit; and - The stored height resulting from the storage of the previously merged value.
9. The radio altimeter system (101) according to any one of claims 7 and 8, wherein: Selecting one of the first altitude value and the second altitude value based on the at least one selection parameter includes: - determining a reference altitude based on the at least one selected parameter; and - selecting a height value closest to the reference height from among the first height value and the second height value.
10. The radio altimeter system (101) according to any one of claims 1 to 9, wherein: The predetermined height threshold from the ground level is between 25 meters and 35 meters.
11. An aircraft (100) comprising the radio altimeter system (101) according to any one of claims 1 to 10.