CN117835260B - Multi-frequency multi-polarization wide-beam scanning base station system and optimal design method - Google Patents

Abstract

The invention discloses a multi-frequency multi-polarization wide-beam scanning base station system and an optimization design method, which relate to the field of mobile high-speed wireless communications, including: designing a conical horn feed antenna capable of radiating a Gaussian base mode beam based on aperture field expansion and mode coupling theory to provide a stable beam width and phase center; designing a beam separation device based on a periodic structure, comprising a bandpass frequency selective surface and a linear polarization grating; synthesizing a front-end quasi-optical link of a multi-frequency multi-polarization channel to expand the base station antenna bandwidth and communication rate; the invention combines a genetic optimization algorithm with a reflector shaping to effectively reduce the contradiction between the shielding effect of a double reflector antenna and a scanning angle, thereby realizing a multiplied beam scanning angle.

Description

A multi-frequency multi-polarization wide-beam scanning base station system and optimization design method

Technical Field

The present invention relates to the field of mobile high-speed wireless communications, and in particular to a multi-frequency multi-polarization wide-beam scanning base station system and an optimization design method.

Background Art

In the late 1980s, with the development of digital communication technology, mobile communication technology gradually became popular. At present, the fifth-generation mobile communication system (5G) has begun commercial use. The advantages of 5G technology include higher speed, lower latency, larger bandwidth, better network reliability and security, and better energy efficiency. High-speed mobile communication base station antenna technology will play a vital role in the promotion of 5G and even 6G. Quasi-optical technology is a technology that uses millimeter waves for wireless communication. It combines the characteristics of optical communication and microwave communication and is used for beam directional propagation, beamforming and spatial filtering in engineering. Quasi-optical technology is based on optical principles and uses electromagnetic waves in the microwave and millimeter wave frequency range to perform beamforming and form a beam directional system. At present, quasi-optical systems have been used in radar systems, satellite communications, wireless communication networks and other fields.

The current mobile communication base station antenna technology has the following difficulties: the transmission rate is low and a large bandwidth cannot be achieved in the millimeter wave frequency band; the loss in the millimeter wave frequency band is large; the beam scanning limit angle is very small and the ability to track moving targets is very poor.

In view of this, it is necessary to propose a multi-frequency and multi-polarization wide-beam scanning base station system and an optimization design method.

Summary of the invention

In order to solve the above technical problems, the present invention provides a multi-frequency multi-polarization wide-beam scanning base station system and an optimization design method to expand the existing base station bandwidth while reducing transmission loss and improving the beam scanning function. The present invention uses 45GHz, 100GHz and 220GHz conical corrugated horns as beam generating devices, radiating fundamental mode Gaussian beams as the feed source of the initial signal. As an improvement of the smooth inner wall conical horn, the conical corrugated horn can significantly reduce the diffraction effect of the metal edge of the horn, while optimizing the axial symmetry of the directional pattern and reducing the cross-polarization inside the horn. Under normal circumstances, the electromagnetic wave fed by the circular waveguide is the TE ₁₁ main mode, which is converted into the HE ₁₁ mode after the mode conversion section. This is an electromagnetic balance mode, and the good radiation performance of the conical corrugated horn stems from this.

Linear polarization gratings and 45GHz and 220GHz bandpass frequency selective surfaces are used as beam separation devices to provide multi-channel beam separation and synthesis. Linear polarization gratings can separate or synthesize vertically polarized beams and horizontally polarized beams, thereby achieving multi-polarization design requirements. The structure of the linear polarization grating is relatively simple, consisting of metal wires tightly arranged on a vertical plane. The frequency selective surface is a surface structure that controls electromagnetic waves, usually with a two-dimensional periodic structure, consisting of multiple periodic metal conductors or dielectric arrays. The frequency response characteristics of the frequency selective surface can be quickly and accurately calculated using the finite time-domain difference method (FDTD) algorithm using the Floquet periodic boundary theory.

The ellipsoid mirror surfaces with different long and short axes are used as beam focusing devices. The beam focusing function of the ellipsoid is used to fold and converge each beam channel, thereby controlling the overall link volume. According to the incident beam parameters and the ABCD beam transfer matrix of the ellipsoid, various parameters of the outgoing beam can be quickly calculated. At the same time, the ellipsoid surface is essentially a metal surface, which supports the large bandwidth characteristics of the system. The physical optics algorithm (PO) can be used to quickly simulate the radiation field before and after the beam transformation.

The reflector antenna with a large aperture is used as a beam scanning device and provides high gain. The reflector antenna is the last quasi-optical device of the entire link, which gathers all beam channels and provides them with highly directional radiation into free space. Through the optimization of the reflector shaping and the small defocus movement of the equivalent feed source, large-angle beam scanning is achieved, alleviating the contradiction between the shielding effect of the sub-reflector and the beam scanning angle.

In order to achieve the above object, the present invention adopts the following technical scheme:

A multi-frequency multi-polarization wide beam scanning base station system, comprising a beam generating device, a beam converging device, a beam separating device and a beam scanning device;

The beam generating device is used to radiate an approximate Gaussian beam with a broadband conical horn feed source;

The beam focusing device utilizes the beam focusing characteristics of the ellipsoidal mirror to fold and converge the multi-beam channels;

The beam separation device separates the multi-channel beams through the beam separation characteristics of the frequency selective surface and the linear polarization grid;

The beam scanning device realizes wide-angle beam scanning through a large-aperture reflector antenna after shape optimization.

Furthermore, the beam generating device includes: 45GHz, 100GHz and 220GHz conical corrugated horns, the groove depth of the mode conversion section gradually changes from λ/2 to λ/4, wherein λ is the central wavelength of the feed source; and the beam waist of the radiated Gaussian beam is ω ₀ , the radius of the horn mouth is a, and when ω ₀ /a=0.644, the coupling degree between the near-field energy distribution and the Gaussian base mode reaches 98%, which can provide a stable phase center and beam width for subsequent quasi-optical link design and provide high-speed communication.

Furthermore, the beam focusing device includes: an ellipsoidal reflector with a high-precision surface, using the ABCD beam transfer matrix of the ellipsoidal mirror and the beam matching condition R ₁ =R _in , where R ₁ is the distance from the incident focus to the reflection point, and R _in is the incident beam curvature radius, to converge and fold the beams of each channel while maintaining a small distortion amount, thereby achieving controllability of the system volume.

Furthermore, the beam separation device includes: 45GHz, 220GHz bandpass frequency selective surfaces and linear polarization gratings; the separation and synthesis of multi-frequency beams are realized by the bandpass frequency selective periodic surface based on Floquet's theorem, and the separation and synthesis of dual-polarization beams are realized by the linear polarization grating, so that the beam channel is doubled.

Furthermore, the beam scanning device includes: a large-aperture reflector antenna based on a Cassegrain antenna structure, which utilizes an equivalent feed source with a focus shift of less than 4 cm combined with a physical optical simulation method to achieve a beam scanning angle greater than or equal to 20 degrees.

The present invention also provides an optimization design method for a multi-frequency multi-polarization wide-beam scanning base station system, comprising the following steps:

S1, measure the beam waist width and equivalent beam waist position of the output beam of the front-end quasi-optical link as the equivalent Gaussian feed source of the reflector antenna;

S2, using Fourier series to expand the main reflection surface busbar into finite terms, and in the present invention, the first 11 expansion coefficients are sufficient to meet the simulation accuracy;

S3. Use programming language to implement modeling and simulation in electromagnetic simulation software, greatly improving the simulation optimization efficiency of the system;

S4. Setting a fitness function according to the target scanning angle, equivalent feed position and equivalent beam waist width. The fitness function mainly depends on the energy proportion of the target scanning angle interval of the E-plane pattern obtained by simulation analysis.

S5. Use genetic algorithm and electromagnetic simulation analysis to continuously adjust Fourier expansion coefficients. Genetic algorithm is a heuristic algorithm that solves optimization problems by simulating the biological evolution process. It is based on the basic principles of natural selection and genetics. By simulating the evolutionary process of nature, excellent genes in the population are gradually screened out to achieve the purpose of optimization.

S6. When the fitness function reaches the minimum value, the optimization stops and the optimized expansion coefficient is retained. At this time, the shaping optimization ends and all the steps of the optimization design are completed.

The advantages and beneficial effects of the present invention are as follows:

In the present invention, the broadband covers all available frequency bands for mobile communications in the range of 24.25 GHz to 226 GHz, greatly expanding the bandwidth of existing base stations; the loss is low, the front-end feeding system adopts a quasi-optical solution, and electromagnetic waves propagate between metal reflective surfaces in free space; the beam scanning angle is large, and the contradiction between the shielding effect of the sub-reflective surface and the beam scanning angle is alleviated by optimizing the shape of the reflective surface using a genetic algorithm, and a beam scanning angle greater than or equal to 20 degrees is achieved through a small defocus movement.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of a multi-frequency multi-polarization wide-beam scanning base station system of the present invention;

Fig. 2 is a cross-sectional view of a conical corrugated horn;

FIG3 is a schematic diagram of a periodic unit of a frequency selective surface;

FIG4 is a schematic diagram of a linear polarization grid;

Fig. 5 is a flow chart of the steps of ellipsoidal surface design;

FIG6 is a flow chart of the optimization of the reflection surface shaping;

Figure 7 is a schematic diagram of the results before and after shape optimization.

The meanings of the reference numerals in the figure are: 1 is an H-polarized 100 GHz feed source, 2 is an H-polarized 220 GHz feed source, 3 is an H-polarized 45 GHz feed source, 4 is a V-polarized 220 GHz feed source, 5 is a V-polarized 100 GHz feed source, 6 is a V-polarized 45 GHz feed source, 7 is an H-polarized 100 GHz feed source converging reflector group, 8 is an H-polarized 220 GHz feed source converging reflector group, 9 is an H-polarized 45 GHz feed source converging reflector group, 10 is a V-polarized 100 GHz feed source converging reflector group Mirror group, 11 is a V-polarization 220 GHz feed focusing reflector group, 12 is a V-polarization 45 GHz feed focusing reflector group, 13 is an H-polarization 220 GHz bandpass frequency selective surface, 14 is an H-polarization 45 GHz bandpass frequency selective surface, 15 is a V-polarization 220 GHz bandpass frequency selective surface, 16 is a V-polarization 45 GHz bandpass frequency selective surface, 17 is a V-polarization multi-beam focusing mirror, 18 is an H-polarization multi-beam focusing mirror, 19 is a linear polarization grating, and 20 is a terminal reflector antenna.

DETAILED DESCRIPTION

In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

The following further illustrates how the system is designed in conjunction with the accompanying drawings and specific implementation methods.

The basic principle structure of the present invention is shown in Figure 1. The feed source adopts 45GHz, 100GHz and 220GHz conical corrugated horns to provide an initial Gaussian beam. The feed source includes H-polarized 100GHz feed 1, H-polarized 220GHz feed 2, H-polarized 45GHz feed 3, V-polarized 220GHz feed 4, V-polarized 100GHz feed 5, and V-polarized 45GHz feed 6. The waist sizes and positions of the Gaussian beams of the three 45GHz, 100GHz and 220GHz conical corrugated horns will be given below. Only by clarifying the waist size and position of the feed source Gaussian beam can the Gaussian beam parameters such as the beam radius, curvature radius, etc. at each position of the quasi-optical link system be accurately calculated. After the H-polarized 100GHz feed 1, the H-polarized 220GHz feed 2, the H-polarized 45GHz feed 3, the V-polarized 220GHz feed 4, the V-polarized 100GHz feed 5, and the V-polarized 45GHz feed 6 emit Gaussian beams, they all enter a set of reflector systems, which include an H-polarized 100GHz feed convergence reflector group 7, an H-polarized 220GHz feed convergence reflector group 8, an H-polarized 45GHz feed convergence reflector group 9, a V-polarized 100GHz feed convergence reflector group 10, a V-polarized 220GHz feed convergence reflector group 11, and a V-polarized 45GHz feed convergence reflector group 12. The reflector system folds, converges, and transforms the incident Gaussian beam so that the parameters of the outgoing Gaussian beam meet the subsequent design indicators. The design method and steps of the reflector will be given below. The 100GHz and 220GHz beams pass through the H-polarized 100GHz feed convergence reflector group 7, the H-polarized 220GHz feed convergence reflector group 8, the V-polarized 100GHz feed convergence reflector group 10, and the V-polarized 220GHz feed convergence reflector group 11, and then enter the 220GHz bandpass frequency selection surface, and the two transmission paths are synthesized through the 220GHz bandpass frequency selection surface. Subsequently, the path beam and the 45GHz beam passing through the H-polarized 45GHz feed convergence reflector group 9 and the V-polarized 45GHz feed convergence reflector group 12 enter the 45GHz bandpass frequency selection surface, and the beam transmission paths of the three frequencies are synthesized through the 45GHz bandpass frequency selection surface. After that, it enters the linear polarization grid to synthesize the beam paths of H polarization and V polarization, and doubles the number of channels. Finally, the beams of all frequency channels and all polarization channels are synthesized at the same position and in the same direction and uniformly fed into the reflector antenna. Finally, the reflector antenna realizes the high-gain beam scanning function.

The transmission process of the 6-channel signal is described in detail below: The H-polarized 100 GHz signal is transmitted through the H-polarized 100 GHz feed source 1, and then enters the H-polarized 100 GHz feed source focusing reflector group 7, and then passes through the H-polarized 220 GHz bandpass frequency selective surface 13 and the H-polarized 45 GHz bandpass frequency selective surface 14 in sequence, and then passes through the H-polarized multi-beam focusing mirror 18, and finally passes through the linear polarization grid 19 to feed the terminal reflector antenna 20. The H-polarized 220 GHz signal is transmitted through the H-polarized 220 GHz feed source 2, and then enters the H-polarized 220 GHz feed source focusing reflector group 8, and then passes through the H-polarized 220 GHz bandpass frequency selective surface 13 and the H-polarized 45 GHz bandpass frequency selective surface 14 in sequence, and then passes through the H-polarized multi-beam focusing mirror 18, and finally passes through the linear polarization grid 19 to feed the terminal reflector antenna 20. The H-polarized 45 GHz signal is transmitted through the H-polarized 45 GHz feed 3, and then enters the H-polarized 45 GHz feed focusing reflector group 9, and then passes through the H-polarized 45 GHz bandpass frequency selective surface 14, and then passes through the H-polarized multi-beam focusing mirror 18, and finally passes through the linear polarization grid 19 to feed the terminal reflector antenna 20. The V-polarized 100 GHz signal is transmitted through the V-polarized 100 GHz feed 5, and then enters the V-polarized 100 GHz feed focusing reflector group 10, and then passes through the V-polarized 220 GHz bandpass frequency selective surface 15 and the V-polarized 45 GHz bandpass frequency selective surface 16 in sequence, and then passes through the V-polarized multi-beam focusing mirror 17, and finally passes through the linear polarization grid 19 to feed the terminal reflector antenna 20. The V-polarized 220GHz signal is transmitted through the V-polarized 220GHz feed source 4, and then enters the V-polarized 220GHz feed source focusing reflector group 11, and then passes through the V-polarized 220GHz bandpass frequency selective surface 15 and the V-polarized 45GHz bandpass frequency selective surface 16 in sequence, and then passes through the V-polarized multi-beam focusing mirror 17, and finally passes through the linear polarization grating 19 to feed the terminal reflector antenna 20. The V-polarized 45GHz signal is transmitted through the V-polarized 45GHz feed source 6, and then enters the V-polarized 45GHz feed source focusing reflector group 12, and then passes through the V-polarized 45GHz bandpass frequency selective surface 16, and then passes through the V-polarized multi-beam focusing mirror 17, and finally passes through the linear polarization grating 19 to feed the terminal reflector antenna 20. The overall size of the front-end quasi-optical link panel is 30cm*40cm.

The basic structure of the conical corrugated horn is shown in Figure 2. The conical corrugated horn antenna can provide an axisymmetric aperture field distribution, which is the basis for coupling with the Gaussian transmission mode. In quasi-optical systems, conical corrugated horns are often used as feed sources, which can radiate approximate Gaussian beams. The depth of the mode conversion section wave groove gradually changes from λ/2 to λ/4, and then maintains λ/4 unchanged, where λ is the central wavelength of the feed source. In Figure 2, _L1 is the length of the mode conversion section, _L2 is the length of the mode maintenance section, _L3 is the length of the Gaussian contour section, L is the length of the conical corrugated horn, r is the radius of the feed circular waveguide, d is the corrugated groove depth, w is the wave groove width, t is the wave tooth width, a is the horn aperture radius, and α is the aperture angle. The solution of the paraxial wave equation consists of a series of Gaussian modes, which are orthogonal to each other, so they can be used as an orthogonal basis for the aperture field expansion. Therefore, the electric field of the paraxial beam perpendicular to the optical axis can always be expanded to the superposition of these modes. Usually, the original electric field can be well expanded with fewer Gaussian modes. In some cases, only the Gaussian modes can provide a high coupling coefficient. In the conical corrugated horn, when ω ₀ /a＝0.644, the coupling degree between the near-field energy distribution and the Gaussian modes is as high as 98%, which can provide a stable phase center and beam width, where the waist of the radiated Gaussian beam is ω ₀ and the radius of the horn mouth is a. The parameters of the horns at various frequencies are detailed in Table 1. In Table 1, f is the center frequency of the conical corrugated horn.

Table 1

The far-field E-plane and H-plane far-field patterns of 45GHz, 100GHz and 220GHz conical corrugated horns are roughly the same, and the energy is highly concentrated in the main lobe. The E-plane beam is wider and the side lobes are low; the H-plane beam is narrower and the side lobes are high. The maximum gain of the E-plane far-field pattern of the 45GHz conical corrugated horn is 20.2dBi, and the 3dB beamwidth is 19.7deg; the maximum gain of the H-plane far-field pattern is 20.2dBi, and the 3dB beamwidth is 18.2deg. The maximum gain of the E-plane far-field pattern of the 100GHz conical corrugated horn is 20.2dBi, and the 3dB beamwidth is 19.7deg; the maximum gain of the H-plane far-field pattern is 20.2dBi, and the 3dB beamwidth is 18.2deg. The maximum gain of the far-field pattern of the 220GHz conical corrugated horn on the E plane is 20.2dBi, and the 3dB beam width is 19.7deg; the maximum gain of the far-field pattern of the H plane is 20.2dBi, and the 3dB beam width is 18.4deg. The horn phase center and beam waist width are shown in Table 2.

Table 2

Table 2 lists the phase center and beam waist width of the 45GHz, 100GHz and 200GHz feed horns. It can be seen that the phase center and the horn mouth are basically coincident. The Gaussian feed horn designed in this way greatly facilitates the system-level design of quasi-optical links. The reason why the phase center and the horn mouth are not completely coincident is that the energy coupling coefficient between the Gaussian base mode and the conical corrugated horn is not 100%.

The periodicity of the frequency selective surface is shown in Figure 3. The frequency response characteristics of the frequency selective surface can be quickly and accurately calculated by the finite time domain difference method (FDTD) algorithm using the Floquet periodic boundary theory. The Floquet theorem in electromagnetics can be generalized as follows: in a stable transmission mode, the field of a certain section differs from the field of another section separated by a certain spatial period by only a complex constant. Table 3 lists the detailed parameters of the frequency selective surface (FSS). Ts is the side length of the periodic unit, _H1 is the length of the short side, _H2 is the length of the long side, R is the radius of the central disk, and Hs is the distance between the frequency selective surface layers.

Table 3

In quasi-optical link systems, considering the optical path layout and the placement of components, the general beam is not normally incident on the frequency selective surface. The TE wave is set as the excitation signal to be incident on the 45GHz and 220GHz frequency selective surfaces, and the incident angles of 0deg, 15deg, 30deg and 45deg are set in the simulation program in turn to calculate the reflection coefficient and transmission coefficient. The double-layer frequency selective surface structure provides two resonance points with close distances, which effectively increases the bandwidth. The -10dB bandwidth of the 45GHz frequency selective surface is about 5GHz, and the -10dB bandwidth of the 220GHz frequency selective surface is about 30GHz. As the incident angle increases, the reflection coefficient at the center of the passband increases slightly, but is still below -10dB, showing good large incident angle performance.

The principle diagram of the linear polarization grating is shown in Figure 4. The linear polarization grating can separate or synthesize vertical polarization beams and horizontal polarization beams, thereby realizing the design requirements of multi-polarization. Generally, the incident beam is a vertically polarized beam and a horizontally polarized beam, the transmitted beam is a vertically polarized beam, and the reflected beam is a horizontally polarized beam. In general, a substrate-free linear polarization grating metal wire with g＜λ/4 and c＜λ/10 can meet the quasi-optical link indicators. Where c is the metal wire width and g is the metal wire spacing.

The design steps of the ellipsoidal metal reflector are shown in Figure 5. First, the outgoing beam parameters are determined according to the incident beam parameters. When designing a reflector in a quasi-optical link system, the angle _θi between the incident beam and the outgoing beam is usually determined to be a constant. At the same time, the operating wavelength λ of the incident beam (i.e., the center wavelength of the feed source), the confocal distance _zc , the beam waist _ω0in , and the distance _din from the beam waist to the ellipsoidal mirror are all known. If the outgoing beam waist to be determined is _ω0out , then according to the formula:

The equivalent focal length _fe of the ellipsoidal mirror can be calculated, and then according to the following formula:

Find the distance d _out from the waist of the outgoing beam to the ellipsoidal mirror.

Secondly, the specific parameters of the ellipsoidal surface are determined according to the incident beam and the outgoing beam. When the incident beam and the outgoing beam match the ellipsoidal mirror, R1 = R _in , where R ₁ is the distance from the incident focus to the reflection point, and R _in is the radius of curvature of the incident beam. Finally, the ellipsoidal mirror is intercepted according to the 2ω criterion to complete the design of the reflective surface. Where ω is the beam radius at the reflective surface. When the intercepted mirror radius is greater than twice the beam radius, 99.99% of the beam energy can be included.

After passing through the quasi-optical link system, the three-channel beams did not diverge, and the beam waists were converged to the same position, with the phase maintained well, which greatly facilitated the subsequent reflector antenna design.

The following further illustrates how the system is optimized in conjunction with the accompanying drawings and specific implementation methods.

S1. Measure the beam waist width and equivalent beam waist position of the output beam of the front-end quasi-optical link, see Table 4 (output beam parameter table).

Table 4

S2. Expand the main reflection surface generatrix by finite terms using Fourier series, where _a0 to _a10 are Fourier expansion coefficients, see Table 5 (Fourier expansion coefficient table).

Table 5

S3. Use programming languages to implement electromagnetic modeling in electromagnetic simulation software;

S4, setting a fitness function according to the target scanning angle, equivalent feed position and equivalent beam waist width;

S5. Continuously adjust the Fourier expansion coefficients using genetic algorithms and electromagnetic simulation analysis, as shown in FIG6 , including: using a dedicated program to control electromagnetic simulation software to calculate the far-field pattern; calculating the fitness function value based on the far-field pattern; bringing the fitness function value back into the genetic algorithm; adjusting the expansion coefficients based on the genetic algorithm; and calculating the far-field pattern again based on the expansion coefficients using a dedicated program, and continuously optimizing in a cycle.

S6. When the fitness function reaches the minimum value, the optimization stops and the optimized expansion coefficient is retained. The optimized expansion coefficient is simulated again to verify that the beam scanning angle is effectively doubled, as shown in FIG7.

Claims (5)

1. A multi-frequency multi-polarization wide beam scanning base station system, characterized in that it includes a beam generating device, a beam converging device, a beam separating device and a beam scanning device; The beam generating device is used to radiate an approximate Gaussian beam with a broadband conical horn feed including a mode sustaining segment; The beam focusing device utilizes the beam focusing characteristics of the ellipsoidal mirror to fold and converge the multi-beam channels; The beam separation device separates the multi-channel beams through the beam separation characteristics of the frequency selective surface and the linear polarization grid; The beam scanning device realizes wide-angle beam scanning through a large-aperture reflector antenna after shape optimization; The beam scanning device includes a large-aperture reflector antenna based on a Cassegrain antenna structure, which uses an equivalent feed source with a focus movement of less than 4 cm combined with a physical optical reflector shaping simulation method to double the beam scanning angle and achieve a beam scanning angle greater than or equal to 20 degrees. 2. A multi-frequency multi-polarization wide beam scanning base station system according to claim 1, characterized in that the beam generating device comprises: 45GHz, 100GHz and 220GHz conical corrugated horns, the depth of the mode conversion section groove is Gradually transform to ,in is the center wavelength of the feed source; and the waist of the radiated Gaussian beam is The radius of the bell mouth is , When the near-field energy distribution is coupled with the Gaussian base mode, the coupling degree reaches 98%, which can provide a stable phase center and beam width for subsequent quasi-optical link design and provide high-speed communication. 3. A multi-frequency multi-polarization wide beam scanning base station system according to claim 1, characterized in that the beam focusing device comprises an ellipsoidal reflector with a high-precision surface, using the ABCD beam transfer matrix and beam matching condition of the ellipsoidal reflector ,in is the distance from the incident focus to the reflection point, The incident beam curvature radius is used to converge and fold the beams of each channel while keeping a small distortion to achieve controllable system volume. 4. According to claim 1, a multi-frequency, multi-polarization, wide-beam scanning base station system is characterized in that the beam separation device includes 45GHz, 220GHz bandpass frequency selection surfaces and linear polarization gratings; the separation and synthesis of multi-frequency beams are achieved by using a bandpass frequency selection periodic surface based on Floquet's theorem, and the separation and synthesis of dual-polarization beams are achieved by using a linear polarization grating, thereby doubling the beam channel. 5. The optimization design method of a multi-frequency multi-polarization wide-beam scanning base station system according to any one of claims 1 to 4, characterized in that it comprises the following steps: S1. Measure the beam waist width and equivalent beam waist position of the output beam of the front-end quasi-optical link; S2. Expand the main reflection surface generatrix by finite terms using Fourier series; S3. Use programming language to implement modeling and simulation in electromagnetic simulation software; S4, setting a fitness function according to the target scanning angle, equivalent feed position and equivalent beam waist width; S5. Continuously adjust the Fourier expansion coefficients using genetic algorithms and electromagnetic simulation analysis; S6. When the fitness function reaches the minimum value, the optimization stops and the optimized Fourier expansion coefficients are retained.