A method for modeling an air-ground channel suitable for millimeter wave phased arrays

Abstract

The application provides a kind of air-ground channel modeling method suitable for millimeter wave phased array, comprising: step 1, establishing the Two-Ray channel geometric model of direct path and multiple reflection paths;Step 2, according to the geometric model, calculate the Rician factor;Step 3, according to the geometric model, determine the time delay of the reflection path;Step 4, according to the carrier frequency and the speed of motion, determine the Doppler frequency offset of the direct path;Step 5, according to the geometric model and Jacks distribution, determine the Doppler power spectrum of the reflection path;Step 6, based on the generalized stationary uncorrelated scattering model, establish the channel model. Through the application, a high-accuracy phased array air-ground channel model can be established, by considering the departure angle of the phased array transmitting antenna and the arrival angle of the receiving antenna in the air-ground channel model, the accuracy of the Rician factor calculation and the accuracy of the Doppler spread power spectrum in the fading channel can be improved.

Description

Technical Field

[0001] This invention relates to the field of air-to-ground channel modeling technology for millimeter-wave phased arrays, and more specifically, to an air-to-ground channel modeling method applicable to millimeter-wave phased arrays. Background Technology

[0002] In recent years, unmanned aerial vehicles (UAVs) have performed remarkably well in both military and civilian markets, meeting the needs of diverse application scenarios. In various UAV-related applications, UAVs require the ability to interact with ground stations or terminals. With the maturity of millimeter-wave phased array technology, UAVs equipped with millimeter-wave phased array antennas for ground-to-ground directional communication can significantly improve communication speeds, becoming a trend in UAV development. Therefore, accurately extracting the wireless propagation channel characteristics under phased array antenna scenarios to build a reliable and easy-to-use UAV A2G (Air to Ground) communication channel model is particularly crucial.

[0003] Existing research on A2G channels mainly focuses on fading channel models, including modeling Doppler power spectral density and delay power spectral density; derivation of air-to-ground channel models for different frequency bands; and study of channel characteristics of aircraft in different flight scenarios (takeoff, level flight, and landing). However, research on A2G channels in phased array antenna scenarios is still relatively lacking. Summary of the Invention

[0004] This invention aims to provide an air-to-ground channel modeling method suitable for millimeter-wave phased arrays. This method improves the accuracy of the phased array A2G channel model by considering the beam angle and attenuation relationship in the phased array pattern and establishing a two-ray model of the line-of-sight path (LoS) and multiple reflected paths.

[0005] This invention provides an air-to-ground channel modeling method suitable for millimeter-wave phased arrays, comprising the following steps:

[0006] Step 1: Establish a Two-Ray channel geometric model for the line-of-sight path and multiple reflection paths;

[0007] Step 2: Calculate the Rice factor based on the geometric model;

[0008] Step 3: Determine the time delay of the reflection path based on the geometric model;

[0009] Step 4: Determine the Doppler frequency offset of the line-of-sight path based on the carrier frequency and motion speed;

[0010] Step 5: Using the Doppler frequency offset of the direct-view path, determine the Doppler power spectrum of the reflection path based on the geometric model and Jacks distribution;

[0011] Step 6: Using the Rice factor, the time delay of the reflection path, the Doppler frequency offset of the direct-view path, and the Doppler power spectrum of the reflection path, establish a channel model based on the generalized stationary uncorrelated scattering model.

[0012] Furthermore, in step 1, a two-ray channel geometric model of the line-of-sight path and multiple reflection paths is established based on the aircraft altitude H, the ground station altitude h, and the communication line-of-sight distance Dl.

[0013] Furthermore, methods for establishing a Two-Ray channel geometry model with a direct line-of-sight path and multiple reflection paths include:

[0014] The elevation angle θ of the ground station is:

[0015] θ=sin -1 ((Hh) / Dl)

[0016] The formula for calculating the reflection path Dr1 is as follows:

[0017]

[0018] The formula for calculating the reflection path Dr2 is as follows:

[0019]

[0020] The pitch angle γ of the aircraft's launch reflection path is:

[0021] γ=sin -1 (H / Dr2)

[0022] The launch angle β of the aircraft's launch reflection path is:

[0023] β=γ-θ

[0024] in,

[0025] Preferably, the angle corresponding to a 10dB reduction is taken as the angle of arrival. The maximum value.

[0026] Furthermore, in step 2, the Rice factor K is defined as the power ratio of the direct-view path and all reflected paths, and the calculation formula is as follows:

[0027]

[0028] in:

[0029] Gt(β) is the dB value of the gain decrease when the emission phased array has a launch angle of β;

[0030] To receive phased arrays to achieve an angle of The dB value at which the gain decreases;

[0031] Γ is the reflection coefficient of the reflecting surface.

[0032] Furthermore, in step 3, the time delay τ of the reflection path max for:

[0033] τ max =(Dr1+Dr2-Dl) / c

[0034] Where c is the speed of light.

[0035] Furthermore, step 4 specifically involves calculating the maximum Doppler frequency offset based on the carrier frequency f and the relative motion speed v of the aircraft. This maximum Doppler frequency offset is the Doppler frequency offset of the line-of-sight path.

[0036] Furthermore, the formula for calculating the Doppler frequency offset of the direct-view path is as follows:

[0037]

[0038] in, denoted as Doppler frequency offset for the direct-view path, and c as the speed of light.

[0039] Furthermore, in step 5, the method for determining the Doppler power spectrum of the reflection path based on the geometric model and Jacks distribution includes:

[0040] The formula for the Jacks distribution is as follows:

[0041]

[0042] in:

[0043]

[0044] When there are N reflection paths, f Dn (n=1,…,N) are randomly distributed within the above interval, and their power is ρ fDn Then the normalized power of each reflection path is:

[0045]

[0046] The normalized power of each reflection path is obtained to get the Doppler power spectrum of the reflection path.

[0047] Furthermore, in step 6, the method for establishing a channel model based on a generalized stationary uncorrelated scattering model includes:

[0048] The input signal is x. After passing through the line-of-sight path channel, the output signal of input signal x at time k is y_los, and the sampling time is T. sample The formula is as follows:

[0049]

[0050] Where, x k It is the value of the input signal x at time k;

[0051] The number of reflection paths N is determined, and the reflection paths use a channel model based on a generalized stationary uncorrelated scattering model, with the output signal being y. k_r The formula is:

[0052]

[0053] Among them, y k_r It is the output signal of the input signal x at time k after passing through the reflection path channel, where L is the filter length; the formula for calculating I is as follows:

[0054] I = round(τ) max / T sample )

[0055] Finally, the total channel output sequence y is obtained, as shown in the following formula:

[0056] y k =y k_los +y k_r

[0057] Among them, y k It is the output of the input signal at time k after passing through the entire channel.

[0058] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0059] This invention enables the establishment of a highly accurate phased array air-to-ground channel model. By incorporating the launch angle of the phased array transmitting antenna and the arrival angle of the receiving antenna into the air-to-ground channel model, the accuracy of Rice factor estimation under fading channels and the accuracy of Doppler spread power spectrum can be improved. Attached Figure Description

[0060] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0061] Figure 1This is a flowchart of an air-to-ground channel modeling method applicable to millimeter-wave phased arrays in an embodiment of the present invention.

[0062] Figure 2 This is a schematic diagram of the Two-Ray channel geometric model of the direct-view path and multiple reflection paths established in an embodiment of the present invention.

[0063] Figure 3 This is a schematic diagram of the Doppler power spectral density based on the Jacks distribution in an embodiment of the present invention. Detailed Implementation

[0064] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0065] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0066] Example

[0067] like Figure 1 As shown in the figure, this embodiment proposes an air-to-ground channel modeling method suitable for millimeter-wave phased arrays, including the following steps:

[0068] Step 1: Based on the aircraft altitude H, ground station altitude h, and line-of-sight communication distance Dl, establish a Two-Ray channel geometric model for the line-of-sight path and multiple reflection paths, as follows: Figure 2 As shown.

[0069] Figure 2 In the middle, the elevation angle θ of the ground station is:

[0070] θ=sin -1 ((Hh) / Dl)

[0071] The angle of arrival (the angle relative to the normal) of the reflected path received by the ground station is: Considering the radiation pattern of a phased array, when the angle of arrival... The larger the angle, the greater the reduction in antenna receiving gain relative to normal gain. Generally, the angle of arrival is considered to be the angle corresponding to a 10dB reduction. The maximum value.

[0072] The formula for calculating the reflection path Dr1 is as follows:

[0073]

[0074] The formula for calculating the reflection path Dr2 is as follows:

[0075]

[0076] The pitch angle γ of the aircraft's launch reflection path is:

[0077] γ=sin -1 (H / Dr2)

[0078] The launch angle (angle relative to the normal) β of the aircraft's launch reflection path is:

[0079] β=γ-θ

[0080] Step 2: Calculate the Rice factor based on the geometric model; the Rice factor K is defined as the power ratio of the direct-view path and all reflected paths, and the calculation formula is as follows:

[0081]

[0082] in:

[0083] Gt(β) is the dB value of the gain decrease when the emission phased array has a launch angle of β;

[0084] To receive phased arrays to achieve an angle of The dB value at which the gain decreases;

[0085] Γ is the reflection coefficient of the reflecting surface.

[0086] Step 3: Determine the time delay of the reflection path based on the geometric model;

[0087] The time delay τ of the reflection path max for:

[0088] τ max =(Dr1+Dr2-Dl) / c

[0089] Where c is the speed of light.

[0090] Step 4: Determine the Doppler frequency offset of the line-of-sight path based on the carrier frequency and motion speed;

[0091] The maximum Doppler frequency offset is calculated based on the carrier frequency f and the relative velocity v of the aircraft. This maximum Doppler frequency offset is the Doppler frequency offset of the line-of-sight path. The calculation formula is as follows:

[0092]

[0093] in, denoted as Doppler frequency offset for the direct-view path, and c as the speed of light.

[0094] Step 5: Using the Doppler frequency offset of the direct-view path, determine the Doppler power spectrum of the reflection path based on the geometric model and Jacks distribution;

[0095] Doppler power spectral density based on the Jacks distribution, such as Figure 3 As shown. The formula for the Jacks distribution is as follows:

[0096]

[0097] in:

[0098]

[0099] When there are N reflection paths, f Dn (n=1,…,N) are randomly distributed within the above interval, and their power is ρ fDn Then the normalized power of each reflection path is:

[0100]

[0101] Step 6: Using Rice factor, reflection path delay, line-of-sight Doppler frequency offset, and reflection path Doppler power spectrum, establish a channel model based on the generalized stationary uncorrelated scattering model.

[0102] The input signal is x, and the output signal y at time k after the input signal x passes through the line-of-sight path channel is y. k_los The sampling time is T sample The formula is as follows:

[0103]

[0104] Where, x k It is the value of the input signal x at time k;

[0105] The number of reflection paths N is determined, and the reflection paths use a channel model based on a generalized stationary uncorrelated scattering model, with the output signal being y. k_r The formula is:

[0106]

[0107] Among them, y k_r It is the output signal of the input signal x at time k after passing through the reflection path channel, where L is the filter length, usually taken as L = 20; the formula for calculating I is as follows:

[0108] I = round(τ) max / T sample )

[0109] Finally, the total channel output sequence y is obtained. k The formula is as follows:

[0110] y k =y k_los +y k_r

[0111] Among them, y k It is the output of the input signal at time k after passing through the entire channel.

[0112] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for modeling air-to-ground channels suitable for millimeter-wave phased arrays, characterized in that, Includes the following steps: Step 1: Establish a Two-Ray channel geometric model for the line-of-sight path and multiple reflection paths; Step 2: Calculate the Rice factor based on the geometric model; Step 3: Determine the time delay of the reflection path based on the geometric model; Step 4: Determine the Doppler frequency offset of the line-of-sight path based on the carrier frequency and motion speed; Step 5: Using the Doppler frequency offset of the direct-view path, determine the Doppler power spectrum of the reflection path based on the geometric model and Jacks distribution; Step 6: Using Rice factor, reflection path delay, line-of-sight Doppler frequency offset, and reflection path Doppler power spectrum, establish a channel model based on the generalized stationary uncorrelated scattering model. In step 1, based on the aircraft altitude H ground station height h and line-of-sight communication distance Dl A two-ray channel geometric model is established for the line-of-sight path and multiple reflection paths, including: The elevation angle θ of the ground station is: Reflection path Dr The calculation formula is as follows: Reflection path Dr 2. The calculation formula is as follows: Pitch angle of the aircraft's launch reflection path γ for: Launch angle of the aircraft's launch reflection path β for: in, φ > θ The angle corresponding to a 10dB reduction will be used as the angle of arrival. φ The maximum value; In step 2, Rice factor K Defined as the power ratio of the direct-view path and all reflected paths, the calculation formula is as follows: in: The launch angle for the phased array is β The dB value at which the gain decreases; To receive phased arrays to achieve an angle of φ The dB value at which the gain decreases; is the reflection coefficient of the reflecting surface.

2. The air-to-ground channel modeling method for millimeter-wave phased arrays according to claim 1, characterized in that, In step 3, the time delay of the reflection path for: in, c It is the speed of light.

3. The air-to-ground channel modeling method for millimeter-wave phased arrays according to claim 2, characterized in that, Step 4 specifically involves, based on the carrier frequency... f relative speed of the aircraft v Calculate the maximum Doppler frequency offset, which is the Doppler frequency offset of the line-of-sight path.

4. The air-to-ground channel modeling method for millimeter-wave phased arrays according to claim 3, characterized in that, The formula for calculating the Doppler frequency offset of the direct-view path is: in, For the Doppler frequency shift of the direct-view path, c It is the speed of light.

5. The air-to-ground channel modeling method for millimeter-wave phased arrays according to claim 4, characterized in that, In step 5, the method for determining the Doppler power spectrum of the reflection path based on the geometric model and Jacks distribution includes: The formula for the Jacks distribution is as follows: in: When the reflection path has N When, If it is randomly distributed within the above interval, its power is... Then the normalized power of each reflection path is: The normalized power of each reflection path is obtained to get the Doppler power spectrum of the reflection path.

6. The air-to-ground channel modeling method for millimeter-wave phased arrays according to claim 5, characterized in that, In step 6, the method for establishing the channel model based on the generalized stationary uncorrelated scattering model includes: The input signal is x The input signal x After passing through the line-of-sight channel k The signal output at time is Sampling time is The formula is as follows: in, It is the input signal x exist k Time value; Determine the number of reflection paths N The reflection path uses a channel model based on a generalized stationary uncorrelated scattering model, and its output signal is... The formula is: in, It is the input signal x After passing through the reflection path channel k The signal output at all times, L This is the filter length; I The calculation formula is as follows: Finally, the total channel output sequence is obtained. The formula is as follows: in, It is the input signal after passing through the entire channel. k Output at any given moment.

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