Broadband millimeter-wave four-ridged horn probe

Abstract

This invention discloses a broadband millimeter-wave four-ridged horn probe, which mainly solves the problems of narrow bandwidth and poor pattern symmetry of existing high-frequency probes. It includes a horn housing (1), four ridges (2), a waveguide back cavity (4), two coaxial probes (5), and a short-circuit plate (8). The ridges are fixed in the waveguide back cavity. The two coaxial probes pass through the air cavities of the first and second ridges respectively, extending into the corresponding third and fourth ridges, forming an orthogonal staggered arrangement of the two coaxial probes. The opening of the horn housing adopts a square structure at the break point, and the horn wall has multiple adjacent gaps with unequal spacing (6). Each of the four ridges has an exponentially modulated slot (3) on its ridge near the arc portion. The end of each ridge extends to the feed port and connects to the straight waveguide, and adopts a pyramidal structure (7) with chamfered corners. This invention has a wide bandwidth, good dual-polarization performance, low cross-polarization, and stable pattern, and can be used for antenna measurement and electromagnetic compatibility testing.

Description

Technical Field

[0001] This invention belongs to the field of antenna technology, specifically relating to a broadband millimeter-wave four-ridged horn probe, which can be used in antenna measurement, electromagnetic compatibility testing, detection systems, and communication systems. Background Technology

[0002] With the development of wireless communication technology, radio frequency (RF) devices and antennas are becoming more tightly integrated. RF components can interfere with antennas, such as in massive MIMO active antennas, necessitating integrated measurement systems for precise measurements. Near-field measurement has undergone decades of development, and its near-field scanning theory has become highly refined, leading to its widespread application in practical engineering. Near-field measurement requires the use of probes with known characteristics to acquire near-field data, and then accurately calculates the far-field radiation pattern of the antenna under test (AUT) using near-far-field transformation algorithms. The probe antenna itself has specific dimensions and directivity; the signal received by the device is superimposed on the coupled portion, and the coupled signal is easily confused with the signal from the AUT. The coupling between the test antenna and the probe significantly affects the test accuracy; reducing the mutual coupling between the probe and the test antenna is the most critical factor.

[0003] In traditional near-field measurements, the antenna under test is fixed while the test probe is rotated to measure its planar, cylindrical, and spherical radiation patterns. Dual polarization is mainly achieved in two ways: one is through the mechanical rotation of a single-polarization probe, and the other is by directly using a dual-polarization probe. Currently, the four-ridged horn antenna and the dual-polarization Vivaldi antenna are commonly used as millimeter-wave broadband dual-polarization probe antennas. While their working principles are essentially the same, the dielectric loss of the Vivaldi antenna has a greater impact on millimeter-wave devices.

[0004] Open waveguides and horn antennas offer wide radiation patterns and advantages such as easy excitation, simple structure, and high gain. However, these antennas have narrow bandwidths and operate in a single polarization mode. During testing, frequent probe changes and mechanical adjustments are required depending on the operating frequency of the antenna under test, causing significant inconvenience. By placing orthogonal ridge structures within the waveguide or horn, capacitive and inductive effects can be generated, lowering the cutoff frequency of the main transmission mode and widening the operating bandwidth. This allows for the realization of dual-polarization characteristics in horn antennas, which are commonly used as dual-polarization probes in near-field measurements.

[0005] Patent document CN 108879110 A discloses a "small broadband dual-polarized four-ridged horn antenna", such as Figure 1As shown, two pairs of orthogonally arranged exponentially modulated sinusoidal ridges 4 are inserted into the reflector cavity respectively; the SMA feed connector 11 is orthogonally fixed to the outer middle of the adjacent metal sidewall of the reflector cavity 1 with an offset vertically. The insulating medium penetrates the through holes on the metal sidewall of the reflector cavity and the exponentially modulated sinusoidal ridge and extends to the positioning hole of the exponentially modulated ridge on the other side. Although this antenna can achieve ultra-wideband characteristics of 0.8-18GHz, its impedance matching is poor and its standing wave ratio is large.

[0006] Patent document CN 111610378 A discloses a "millimeter-wave dual-polarized near-field measurement probe", such as Figure 2 As shown, it includes a gradually increasing circular waveguide 1 with a diameter that gradually increases along the opening direction, a straight circular waveguide 2 extending in the opposite direction of the opening direction from the starting end of the gradually increasing circular waveguide, a short-circuit plate 3 located at the end of the straight circular waveguide, and four ridges 4 arranged in a cross shape within the two circular waveguide sections. This antenna reduces diffraction effects at the opening by removing part of the horn wall, but the antenna's radiation pattern produces lobes in the high-frequency band, resulting in reduced gain and deteriorated directivity.

[0007] While the aforementioned broadband dual-polarization probe shortens the testing time and significantly reduces the complexity and cost of the antenna measurement system, it cannot simultaneously guarantee wide bandwidth characteristics and a good antenna pattern, nor can it precisely measure the various indicators of millimeter-wave antennas. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of existing technologies by proposing a broadband millimeter-wave four-ridged horn probe to avoid antenna pattern splits, improve antenna impedance matching, broaden the operating bandwidth, thereby improving the accuracy of millimeter-wave antenna measurements and saving testing time.

[0009] To achieve the above objectives, the broadband millimeter-wave four-ridge horn probe of the present invention comprises: a horn housing, four ridges, a waveguide back cavity, two coaxial probes, and a short-circuit plate. The ridges are fixed in the waveguide back cavity by connecting them to the short-circuit plate via a straight waveguide section. The two coaxial probes pass through the air cavities of the first and second ridges, respectively, and extend into the third and fourth ridges at opposite positions, forming an orthogonal staggered arrangement of the two coaxial probes. The ridge curve of each ridge is composed of an exponential curve and a circular arc curve. Its characteristic is that:

[0010] The horn housing has a square structure at the opening and break point, and the horn wall has multiple gaps with varying adjacent spacing, which make it change in a linear stepped manner.

[0011] The four ridges each have exponentially modulated slots on the ridges near the arc portion. The end of each ridge extends to the feed port and connects to the straight waveguide. The ridges are also designed with a pyramidal structure with chamfered corners to avoid contact between them.

[0012] Furthermore, the horn shell is a square pyramid horn structure made of two pairs of metal walls of the same thickness spliced ​​together. The width of each gap is the same, and the distance between the gaps increases linearly to form a stepped structure.

[0013] Furthermore, the four ridges have different structures at the bottom, middle, and top. The bottom ridge has a triangular pyramid structure that extends to the feed point along an exponential curve and is integrated with a straight waveguide section and fixed inside the square waveguide. The middle ridge has an exponential curve profile, and the top ridge has an arc-shaped profile. An exponential groove is opened at the top of the ridge near the arc part, forming four ridges with concave gaps to reduce the low-frequency cutoff frequency and achieve antenna miniaturization.

[0014] Furthermore, the two coaxial probes are connected to a K-type millimeter-wave connector for power supply. The K-type millimeter-wave connector is fixed to the waveguide wall on one side of the first and second ridges, forming a circuit structure with positive and negative poles to achieve horizontal / vertical polarization excitation of the probe.

[0015] Furthermore, the waveguide back cavity is a square waveguide structure and is integrated with the end of the horn section.

[0016] Furthermore, a compensation structure with a height of h is provided between the shorting plate and the two coaxial probes, that is, the difference between the second ridge and the fourth ridge and the cuboid with a height of h is calculated respectively, so as to achieve the effect that the distance from the two coaxial probes to the shorting plate is the same.

[0017] Furthermore, the square aperture of the horn has a side length of 50mm-55mm, and its diameter is related to the beamwidth of the radiation pattern. Generally, a smaller aperture corresponds to a larger beamwidth.

[0018] Furthermore, the width of each gap on the speaker wall is equal, ranging from 4mm to 5mm. The distance between the first and second gaps is 5mm, and the spacing between each gap increases linearly from 1mm to 1.5mm.

[0019] Furthermore, the index groove adopts the same index curve as the ridge slice, with a length of 16mm-20mm and a width of 0.4mm-0.8mm.

[0020] Furthermore, the height z of the ridge slices ranges from -L1 to L, L ranges from 59mm to 69mm, the longitudinal distance L1 from the ridge tip to the origin is 6mm to 6.5mm, the interridge spacing d is 0.5mm to 0.7mm, and the lateral distance y of the arc curve from the origin in the y-direction ranges from... The side length w of the square opening of the horn is 50mm-56mm, the lateral distance w1 between the end of the exponential curve and the inner wall of the horn is 8mm-12mm, the modulation constant C1 is 0.001-0.02, the lateral coordinate y0 of the center of the circle is 21mm-24mm, and the longitudinal coordinate z0 of the center of the circle is 58mm-62mm.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1. Because the present invention has multiple adjacent gaps with unequal spacing in the horn wall, which make it change in a linear step shape, it can better reduce higher-order modes while achieving the required gain, thereby improving the radiation performance of the antenna and reducing the weight of the antenna.

[0023] 2. Compared with the traditional stepped structure, the present invention uses a pyramidal chamfer at the end of each ridge and extends exponentially to the feed port. This makes the excitation end smoother, reduces the generation of higher-order modes, improves impedance matching at high frequencies, and enhances the stability of the antenna pattern.

[0024] 3. This invention increases the current path by creating symmetrical concave gaps on the four ridges and using a structure that combines exponential curves and circular arc curves on the ridges. This ensures a smooth transition from low impedance at the feed point to high impedance at the horn opening, reduces the diffraction effect at the horn opening wall, and thus broadens the bandwidth, enabling the miniaturization of the probe and making it highly practical.

[0025] Simulation experiments show that, compared with the prior art, the present invention has better matching characteristics and a stable radiation pattern while possessing broadband and dual polarization characteristics, which can improve the accuracy and testing efficiency of millimeter-wave antenna measurements. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the overall structure of existing small broadband dual-polarization four-ridged speaker technology;

[0027] Figure 2 This is a schematic diagram of the overall structure of an existing millimeter-wave dual-polarization near-field measurement probe;

[0028] Figure 3 This is a schematic diagram of the overall structure of the present invention;

[0029] Figure 4 This is a schematic diagram of the longitudinal section of the ridge plate in this invention;

[0030] Figure 5 This is the simulation curve of the voltage standing wave ratio (VSWR) parameter of the present invention;

[0031] Figure 6 This is the simulation curve of the two-port isolation of the present invention;

[0032] Figure 7 This is the simulation curve of the cross-polarization isolation of the present invention;

[0033] Figure 8 This is the gain simulation curve of the present invention;

[0034] Figure 9 This invention presents the simulation patterns of the main polarization and cross-polarization of the E-plane and H-plane at different frequencies. Detailed Implementation

[0035] The specific embodiments and effects of the present invention will be described in further detail below with reference to the accompanying drawings.

[0036] Example 1:

[0037] Reference Figure 3 and Figure 4 This example includes: 1. a horn housing; 2. a ridge plate; 3. an exponential slot; 4. a waveguide back cavity; 5. two coaxial probes; 6. a horn wall slot; 7. a triangular pyramid structure; and 8. a shorting plate.

[0038] The horn housing 1 is constructed by splicing together two pairs of slit metal walls of equal thickness, with the side length of the opening inversely proportional to the beamwidth. Each slit 6 on the horn wall has an equal width of 5mm, and the distance between the first and second slits is 5mm. The spacing between each slit and its successor increases linearly by 1mm, forming a stepped structure for the horn wall. Under the premise of achieving the required gain, compared to a horn wall with uniformly spaced slits, higher-order modes can be better attenuated, thereby improving the antenna's radiation performance and reducing its weight.

[0039] The ridge 2 consists of four ridges: the first ridge 21, the second ridge 22, the third ridge 23, and the fourth ridge 24. Each ridge has a different structure at its bottom, middle, and top. The bottom ridge is a triangular pyramid structure 7 formed by Boolean subtraction of the four ridges and four triangular pyramids, which extends to the feed point according to an exponential curve and is integrated with a section of straight waveguide and fixed in a square waveguide, thereby making the excitation end smoother and reducing the generation of higher-order modes. The middle part has an exponential curve profile, and the top part has an arc-shaped profile. An exponential groove 3 is opened at the top of the ridge near the arc part. It adopts the same exponential curve as the ridge, with a length of 17 mm and a width of 0.4 mm, forming a four-ridge with concave gaps to reduce the low-frequency cutoff frequency and achieve antenna miniaturization.

[0040] The equation for the exponential curve is as follows:

[0041]

[0042] Where Y(z) represents the lateral distance of the exponential curve from the origin in the y direction, z represents the longitudinal distance of the exponential curve from the origin in the z direction, d represents the distance between relative ridges, L represents the maximum height of the exponential curve, L1 represents the longitudinal distance from the end of the ridge to the origin, w represents the side length of the square opening of the horn, w1 represents the lateral distance between the end of the exponential curve and the inner wall of the horn, and C1 is the modulation constant.

[0043] The equation of the arc is as follows:

[0044]

[0045] Where y' represents the horizontal distance of the arc curve from the origin in the y direction, z' represents the vertical distance of the arc curve from the origin in the z direction, y0 represents the horizontal coordinate of the center of the circle, z0 represents the vertical coordinate of the center of the circle, and r0 represents the radius of the circle.

[0046] The height z of the four ridges ranges from -L1 to L, where L is 64 mm. The interridge spacing d is 0.6 mm. The longitudinal distance L1 from the ridge end to the origin is 6.4 mm. The lateral distance y of the arc curve from the origin in the y-direction ranges from... The side length w of the square opening of the horn is 54mm, the lateral distance w1 between the end of the exponential curve and the inner wall of the horn is 10mm, the modulation constant C1 is 0.001, the lateral coordinate y0 of the center of the circle is 22mm, and the longitudinal coordinate z0 of the center of the circle is 59.4mm.

[0047] The waveguide back cavity 4 adopts a square waveguide structure, which is seamlessly connected to the beginning of the horn section to reduce the large number of high-order modes caused by the discontinuity of the two structures.

[0048] The two coaxial probes 5 are connected to an external K-type millimeter-wave connector for power supply. The two coaxial probes pass through the air cavities of the first ridge 21 and the second ridge 22 respectively, and extend into the third ridge 23 and the fourth ridge 24 at opposite positions, forming an orthogonal staggered placement of the probes. The K-type millimeter-wave connector is fixed to the waveguide wall on one side of the first ridge 21 and the second ridge 22, forming a circuit structure with positive and negative poles to realize the horizontal / vertical polarization excitation of the probe.

[0049] The short-circuit plate 8 has a square cross-section. A compensation structure 9 with a height of h is provided between the square and the two coaxial probes. The compensation structure 9 is obtained by subtracting the ends of the second ridge plate 22 and the fourth ridge plate 24 from the cuboid with a height of h, so as to achieve the effect that the two coaxial probes are at the same distance from the short-circuit plate.

[0050] Example 2:

[0051] The structure of this example is the same as that of Example 1, and its parameter settings are as follows:

[0052] The width of each slit on the speaker wall is equal, set to 6mm, and the distance between the first and second slits is 5mm. The spacing between each slit and the slits following it increases linearly by 1mm. The length of the index groove is 18mm, and the width is 0.5mm. The height z of the four ridges ranges from -L1 to L, where L is 69mm. The longitudinal distance L1 from the ridge end to the origin is 6.4mm, and the spacing d between ridges is 0.55mm. The lateral distance y of the arc curve from the origin in the y-direction ranges from... The side length w of the square opening of the horn is 52mm, the lateral distance w1 between the end of the exponential curve and the inner wall of the horn is 10mm, the modulation constant C1 is 0.005, the lateral coordinate y0 of the center of the circle is 21mm, and the longitudinal coordinate z0 of the center of the circle is 59mm.

[0053] Example 3:

[0054] The structure of this example is the same as that of Example 1, and its parameter settings are as follows:

[0055] The width of each slit on the speaker wall is equal, set to 4mm, and the distance between the first and second slits is 5mm. The spacing between each slit and the slits following it increases linearly by 1.5mm. The length of the index groove is 19mm, and the width is 0.6mm. The height z of the four ridges ranges from -L1 to L, where L is 61.5mm. The longitudinal distance L1 from the ridge end to the origin is 6.4mm, and the spacing d between ridges is 0.6mm. The lateral distance y of the arc curve from the origin in the y-direction ranges from... The side length w of the square opening of the horn is 56mm, the lateral distance w1 between the end of the exponential curve and the inner wall of the horn is 10mm, the modulation constant C1 is 0.01, the lateral coordinate y0 of the center of the circle is 23mm, and the longitudinal coordinate z0 of the center of the circle is 60mm.

[0056] The effects of this invention can be further illustrated by the following simulation experiments:

[0057] I. Simulation conditions:

[0058] The simulated frequency band range is 8GHz-40GHz.

[0059] The simulation software used is HFSS, a full-wave 3D electromagnetic simulation software developed by Ansoft.

[0060] II. Simulation Content and Results:

[0061] Simulation 1: Under the above conditions, the voltage standing wave ratio (VSWR) parameters of the probe in Example 1 of this invention were simulated, and the results are as follows: Figure 6 .from Figure 6It can be seen that within the 8GHz-40GHz frequency band, the voltage standing wave ratio (VSWR) is less than 2 and the consistency is good, indicating that the probe of this invention has good impedance matching characteristics.

[0062] Simulation 2: Under the above conditions, the isolation between the two ports of the probe in Example 1 of this invention was simulated, and the results are as follows. Figure 7 .from Figure 7 It can be seen that within the 8GHz-40GHz frequency band, the isolation between the two ports is greater than 30dB, indicating that the mutual influence between the two ports is small, which meets the conditions for dual polarization.

[0063] Simulation 3: Under the above conditions, the cross-polarization isolation of the probe in Example 1 of this invention was simulated, and the results are as follows. Figure 8 .from Figure 8 It can be seen that within the 8GHz-40GHz frequency band, the ratio of main polarization to cross polarization is greater than 30dB, indicating that the probe has good dual polarization performance.

[0064] Simulation 4: Under the above conditions, the gain of the probe in Example 1 of this invention was simulated, and the results are as follows. Figure 9 .from Figure 9 It can be seen that within the 8GHz-40GHz frequency band, the probe gain increases gradually, indicating that the probe has a good radiation effect in the main direction and low gain loss.

[0065] Simulation 5: Under the above conditions, the main polarization and cross-polarization patterns of the probe in Example 1 of this invention were simulated, and the results are as follows: Figure 9 ,in:

[0066] 9(a) shows the main polarization and cross-polarization patterns of the E-plane and H-plane of the present invention at a frequency of 10 GHz;

[0067] 9(b) shows the main polarization and cross-polarization patterns of the E-plane and H-plane at 20 GHz;

[0068] 9(c) shows the main polarization and cross-polarization patterns of the E-plane and H-plane at 30 GHz;

[0069] 9(d) shows the main polarization and cross-polarization patterns of the E-plane and H-plane at 40 GHz;

[0070] The first circle of each diagram, E_Co-pol, represents the principal polarization pattern of the E-plane; the second circle, H_Co-pol, represents the principal polarization pattern of the H-plane; the third circle, H_X-pol, represents the cross-polarization pattern of the H-plane; and the fourth circle, E_X-pol, represents the cross-polarization pattern of the E-plane.

[0071] from Figure 9It can be seen that at frequencies of 10GHz, 20GHz, 30GHz and 40GHz, the main lobe of the probe's radiation pattern has no dip and good directivity, meeting the requirements for millimeter-wave near-field measurement.

[0072] The simulation results above show that the broadband millimeter-wave four-ridged horn probe provided by the present invention has good antenna electrical characteristics such as wide bandwidth, high polarization purity, and stable radiation pattern, and has good application prospects and promotion value in the field of near-field antenna measurement.

[0073] The above descriptions are merely three specific examples of the present invention and do not constitute any limitation on the present invention. Obviously, those skilled in the art, after understanding the content and principles of the present invention, may make various modifications and changes in form and detail without departing from the principles and structure of the present invention. However, these modifications and changes based on the ideas of the present invention are still within the scope of protection of the claims of the invention.

Claims

1. A broadband millimeter-wave four-ridged horn probe, comprising: The speaker housing (1), four ridges (2), a waveguide back cavity (4), two coaxial probes (5), and a short-circuit plate (8) are used. The ridges are fixed in the waveguide back cavity by connecting to the short-circuit plate via a straight waveguide. The two coaxial probes pass through the air cavities of the first ridge (21) and the second ridge (22) respectively, and extend into the third ridge (23) and the fourth ridge (24) in opposite positions, forming an orthogonal staggered arrangement of the two coaxial probes. The ridge curve of each ridge is composed of an exponential curve and a circular arc curve. The feature is that: The horn shell (1) has a square structure at the opening of the broken surface, and the horn wall has multiple gaps (6) with different adjacent spacing, so that it has a linear stepped change. The four ridges (2) each have an exponentially modulated slot (3) on the ridges near the arc portion. The end of each ridge extends to the feed port and connects to the straight waveguide. The ridges are also truncated with a pyramidal structure (7) to avoid contact between them.

2. The broadband millimeter-wave four-ridged horn probe according to claim 1, characterized in that: The horn shell is a square pyramid horn structure made of two pairs of slit metal walls of the same thickness spliced ​​together. The width of each slit is the same, and the distance between the slits increases linearly, forming a stepped structure.

3. The broadband millimeter-wave four-ridged horn probe according to claim 1, characterized in that: The four ridges (2) have different structures at the bottom, middle and top. The bottom is a triangular pyramid structure and extends to the feed point according to an exponential curve, connecting with a straight waveguide and fixed in a square waveguide. The middle part is an exponential curve profile. The top part is an arc-shaped profile, and an exponential groove (3) is opened at the top of the ridge near the arc part, forming four ridges with concave gaps to reduce the low-frequency cutoff frequency and realize the miniaturization of the antenna.

4. The broadband millimeter-wave four-ridged horn probe according to claim 1, characterized in that: Two coaxial probes are connected to a K-type millimeter-wave connector for power supply. The K-type millimeter-wave connector is fixed to the waveguide wall on one side of the first ridge (21) and the second ridge (22) to form a circuit structure with positive and negative poles to achieve horizontal / vertical polarization excitation of the probe.

5. The broadband millimeter-wave four-ridged horn probe according to claim 1, characterized in that: The waveguide back cavity (4) is a square waveguide structure and is integrated with the beginning of the horn section.

6. The broadband millimeter-wave four-ridged horn probe according to claim 1, characterized in that: A compensation structure (9) with a height of h is provided between the short circuit board (8) and the two coaxial probes, that is, the difference between the second ridge (22) and the fourth ridge (24) and the cuboid with a height of h is calculated respectively, so as to achieve the effect that the distance between the two coaxial probes and the short circuit board is the same.

7. The broadband millimeter-wave four-ridged horn probe according to claim 1, characterized in that: The side length of the square aperture of the horn is inversely proportional to the beam width.

8. The broadband millimeter-wave four-ridged horn probe according to claim 1, characterized in that: The width of each slit on the speaker wall is equal, ranging from 4mm to 6mm, and the distance between the first slit and the second slit is 4mm to 5mm. The distance between each slit and the slits following it increases linearly from 1mm to 1.5mm.

9. The broadband millimeter-wave four-ridged horn probe according to claim 1, characterized in that: The index groove (3) adopts the same index curve as the spine, with a length of 16mm-20mm and a width of 0.4mm-0.8mm.

10. The broadband millimeter-wave four-ridged horn probe according to claim 1, characterized in that: The height z of the ridge slices is in the range of -L1 to L, the value of L is in the range of 59mm to 69mm, the longitudinal distance L1 from the end of the ridge to the origin is 6mm to 6.5mm, and the inter-ridge spacing d is 0.5mm to 0.7mm. The arc curve has a lateral distance y from the origin in the y-direction ranging from the following values: Where w is the side length of the square opening of the horn, and its value ranges from 50mm to 56mm; The exponential curve has a lateral distance w1 between its end and the inner wall of the speaker of 8mm-12mm, a modulation constant C1 of 0.001-0.02, a lateral coordinate y0 of the center of the circle of 21mm-24mm, and a longitudinal coordinate z0 of the center of the circle of 58mm-62mm.

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