Circularly polarized horn antenna

Abstract

This utility model relates to a circularly polarized horn antenna, comprising: a polarizer for mode conversion from linearly polarized to circularly polarized waves; an impedance matching device for impedance matching and transition between a rectangular waveguide and a circular waveguide; a conical horn for directional radiation of circularly polarized electromagnetic signals into free space or for receiving circularly polarized signals; and a waveguide assembly for connecting the polarizer to external RF devices, separating orthogonal polarization channels and improving isolation. The impedance matching device comprises multiple stacked rectangular-like structures, each side of which is connected by an arc transition, and the dimensions of each layer of rectangular-like structures increase sequentially, forming a gradual stacking effect. It provides wideband coverage, adapting to the wideband requirement of 96-123GHz. The four-stage stacked rectangular-like structure of the impedance matching device achieves a smooth transition from rectangular to circular waveguides, reducing reflection loss by ≥5dB and improving energy transmission efficiency by more than 30% compared to the traditional abrupt square-to-circular structure.

Description

Technical Field

[0001] This utility model belongs to the field of antenna technology, specifically relating to a circularly polarized horn antenna. Background Technology

[0002] In the 6G communication era, the exploration and application of terahertz bands and related devices have become an indispensable part of the development of contemporary high-tech industries. Given the technological background of 6G communication pursuing higher transmission rates and wider channel capacity [1,2], terahertz band antennas responsible for transmitting and receiving signals need to possess higher gain, lower loss, and wider bandwidth compared to traditional antennas to meet the needs of the communication industry. In the ka and lower frequency bands, ferrite-based custom ring couplers have always been the preferred device for achieving signal transmission and reception isolation, but their high power loss and the difficulty in extending their applicable band to the submillimeter wave band due to structural characteristics have become the main factors limiting their further development. Furthermore, patch dual-circular polarization antennas achieve dual-circular polarization by designing different structures on the substrate. The bandwidth of patch dual-circular polarization antennas is usually limited by the loss and size of the dielectric substrate. Simultaneously, the design needs to satisfy the resonance conditions of two orthogonal polarization modes, further compressing the available bandwidth and making it difficult to meet the requirements of wideband applications. Considering the practical requirements of 6G communication and the limitations of existing technology, this invention proposes a design for a dual-circularly polarized horn antenna based on a rectangular partition. This design introduces a square-to-circular impedance matching device. Compared with traditional abrupt change structures (such as abrupt square-to-circular waveguides), this structure has significant advantages in high-frequency band reflection (return loss is generally higher than -20dB), excitation of higher-order modes further aggravates energy dissipation, and reduces antenna radiation efficiency and receiving sensitivity. Utility Model Content

[0003] The purpose of this invention is to provide a circularly polarized horn antenna to solve the problems existing in the prior art.

[0004] To achieve the above-mentioned technical objectives, the technical solution adopted by this utility model is as follows: Circularly polarized horn antenna, including: A polarizer is used to achieve mode conversion from linearly polarized waves to circularly polarized waves; An impedance matching device is disposed at one end of the polarizer and is used for impedance matching and transition between the rectangular waveguide and the circular waveguide. A conical horn, located at the end of the impedance matching device furthest from the polarizer, is used to radiate circularly polarized electromagnetic signals into free space in a directional manner, or to receive circularly polarized signals in space. A waveguide assembly is disposed at the end of the polarizer away from the impedance matching device, and is used to connect the polarizer to external radio frequency devices, separate orthogonal polarization channels and improve isolation. The impedance matching device includes multiple stacked rectangular structures, each side of which is connected by a circular arc transition, and the size of each layer of rectangular structures increases sequentially to form a gradient stacking effect.

[0005] Optionally, the impedance matching circuit includes a four-layer rectangular structure; The four-layer rectangular structure has sides A1, A2, A3, and A4 in ascending order of size; The radii of the arcs in the four-layer rectangular structure, in ascending order, are B1, B2, B3, and B4, respectively. Wherein, A1=1.2mm, A2=0.8mm, A3=0.6mm, A4=0.6mm, B1=0.6mm, B2=1mm, B3=1.3mm, B4=1.5mm; The thickness of each rectangular-like structure is 0.3 mm.

[0006] Optionally, the polarizer includes: aisle; A stepped diaphragm is disposed at the center of the channel along the length of the channel, such that one end of the channel forms port one and port two of the same size, and the end of the channel away from port one and port two forms port three; The impedance matching device is connected to port three, and the waveguide assembly is connected to port one and port two.

[0007] Optionally, the stepped diaphragm is arranged in five steps at one end near the third port; The heights of the steps in the stepped diaphragm from port one to port three are H0, H1, H2, H3, and H4, respectively. The widths of the steps in the stepped diaphragm from port 101 to port 304 are W0, W1, W2, W3 and W4, respectively. Wherein, H0=2mm, H1=1.12mm, H2=0.74mm, H3=0.47mm, H4=0.34mm, W0=8.21mm, W1=0.4mm, W2=0.7mm, W3=0.7mm, W4=0.91mm, and the thickness of the stepped diaphragm is 0.3mm.

[0008] Optionally, the waveguide assembly is provided with two connection ports, and two symmetrical 90° rectangular bend waveguides are provided between the two connection ports and the first port and the second port, respectively.

[0009] Optionally, the connection port is a standard waveguide port WR-08.

[0010] Optionally, a smooth transition structure is provided at the connection point between the two 90° rectangular bend waveguides and the connection port.

[0011] Optionally, the operating center frequency is 110 GHz, the operating bandwidth is between 96 GHz and 123 GHz, the return loss is less than -20 dB, the isolation is less than -25 dB, and the axis ratio is less than 3 dB.

[0012] The beneficial effects of this utility model are: 1. Wide bandwidth coverage, adapting to wide bandwidth requirements of 96-123GHz, meeting the frequency band requirements of 6G communication and the wide bandwidth requirements of radar wide beam scanning.

[0013] 2. Return loss ≤ -20dB (reflection power ≤ 1%), isolation ≤ -25dB (crosstalk power ≤ 0.3%), axial ratio ≤ 3dB (circular polarization purity ≥ 90%), achieving stable high performance across the entire bandwidth, solving the problem of traditional antennas where "center frequency meets standards, but edge frequency bands deteriorate".

[0014] 3. The symmetrical 90° bend waveguide and smooth transition structure of the waveguide assembly physically separates the orthogonal polarization channels to different planes. Combined with the stepped diaphragm of the polarizer, the isolation is improved by ≥5dB compared with the traditional coplanar design, effectively suppressing self-interference. It is suitable for radar anti-clutter and communication anti-multipath scenarios.

[0015] 4. The four-stage stacked rectangular structure of the impedance matching circuit (with a gradual arc transition) achieves a smooth transition from rectangular waveguide to circular waveguide, reducing reflection loss by ≥5dB and improving energy transmission efficiency by more than 30% compared to the traditional abrupt square-to-circular structure. Attached Figure Description

[0016] This utility model can be further illustrated by the non-limiting embodiments given in the accompanying drawings.

[0017] Figure 1 This is a schematic diagram of the structure of the circularly polarized horn antenna of this utility model; Figure 2 This is a schematic diagram of the polarizer structure of the circularly polarized horn antenna of this utility model; Figure 3 This is a schematic cross-sectional view of the waveguide assembly of the circularly polarized horn antenna of this utility model. Figure 4 This is a schematic diagram of the stepped diaphragm structure of the circularly polarized horn antenna of this utility model; Figure 5 This is a schematic diagram of the impedance matching device for the circularly polarized horn antenna of this utility model. Figure 6 The S-curve diagram of the circularly polarized horn antenna of this utility model is shown. Figure 7This is a gain diagram of the circularly polarized horn antenna of this utility model; Figure 8 This is a diagram showing the axial ratio of the circularly polarized horn antenna of this invention.

[0018] The symbols for the main components are explained below: Polarizer 100, Channel 11, Port 101, Port 2 102, Port 3 104, Impedance Matching Device 105, Conical Horn 106, Waveguide Assembly 107, Stepped Diaphragm 103, Connection Port 108, 90° Rectangular Bend Waveguide 200, Smooth Transition Structure 201. Detailed Implementation

[0019] To enable those skilled in the art to better understand this utility model, the technical solution of this utility model will be further described below in conjunction with the accompanying drawings and embodiments.

[0020] like Figure 1-5 As shown, the circularly polarized horn antenna includes: Polarizer 100 is used to realize mode conversion from linearly polarized wave to circularly polarized wave and phase modulation of orthogonal polarization components.

[0021] Specifically, the polarizer 100 includes a channel 11. A stepped diaphragm 103 is disposed at the center of the channel 11 along its length, such that one end of the channel 11 forms two ports of the same size, namely port 101 and port 102, and the end of the channel 11 away from ports 101 and 102 forms port 3 104. An impedance matching device 105 is connected to port 3 104, and a waveguide assembly 107 is connected to ports 101 and 102.

[0022] Channel 11 is a hollow waveguide channel inside polarizer 100, running through polarizer 100 along its length. Serving as a transmission path for electromagnetic waves, it connects port 101, port 102, and port 104, enabling the conversion of signals from linearly polarized waves to circularly polarized waves. It also provides space for the stepped diaphragm 103 (which is integrally manufactured), allowing the stepped diaphragm 103 to modulate the electromagnetic field distribution within channel 11.

[0023] Connection port 101 and port 102 are located at the end of channel 11 near waveguide assembly 107. They are the same size and are separated into two independent channels by stepped diaphragm 103 to transmit linearly polarized wave signals. Port 3 104 is located at the end of channel 11 near impedance matching device 105. It is the converging end of channel 11, without stepped diaphragm separation, forming a single waveguide channel. It is directly connected to impedance matching device 105 and transmits the synthesized circularly polarized signal to conical horn 106 for radiation.

[0024] The stepped diaphragm 103 is the core component for phase modulation and mode conversion. It is fixed at the center of the channel 11 along the length direction of the channel 11 (i.e. the electromagnetic wave transmission direction), symmetrically dividing the channel 11 into two parts, forming port one 101 and port two 102 (with the same size to ensure the symmetry of the orthogonal polarization signal).

[0025] Furthermore, the stepped diaphragm 103 is arranged in five steps near the third port 104; the heights of the steps of the stepped diaphragm 103 from the first port 101 to the third port 104 are H0, H1, H2, H3, and H4, respectively; the widths of the steps of the stepped diaphragm 103 from the first port 101 to the third port 104 are W0, W1, W2, W3, and W4, respectively. Wherein, H0=2mm, H1=1.12mm, H2=0.74mm, H3=0.47mm, H4=0.34mm, W0=8.21mm, W1=0.4mm, W2=0.7mm, W3=0.7mm, W4=0.91mm, and the thickness of the stepped diaphragm 103 is 0.3mm. The height of H0 is also the height of the channel 11.

[0026] A phase delay difference is applied to the linearly polarized wave passing through port 101 and port 102 by means of a stepped gradient structure: When the linearly polarized wave (fundamental mode TE) 10 As the polarization component (TEM) propagates along channel 11, the stepped diaphragm 103 introduces an additional phase delay to the polarization component perpendicular to the diaphragm direction, converting it to TE. 01 Modulus. Finally, at port 3 (104), TE 10 Model and TE 01 A 90° phase difference between the memes synthesizes a circularly polarized wave (left-handed or right-handed, depending on the excitation port).

[0027] Unlike traditional simple metal partitions, the five-layer stepped structure achieves phase delay control over a wide frequency band through precise size gradients (such as the decrease from H0 to H4), solving the problem of mode conversion efficiency fluctuating with frequency in high-frequency bands (such as 110GHz).

[0028] Impedance matching device 105 is disposed at one end of polarizer 100 and is used for impedance matching and transition between rectangular waveguide and circular waveguide; wherein, impedance matching device 105 includes multiple stacked rectangular structures, each side of each layer of rectangular structures is connected by a circular arc transition, and the size of each layer of rectangular structures increases sequentially to form a gradient stacking effect.

[0029] Port 3 104 at the end of polarizer 100 is a rectangular waveguide, while the conical horn 106 typically uses a circular waveguide. The difference in cross-sectional shape and size between the two leads to impedance mismatch; direct connection would cause strong electromagnetic reflection and mode mismatch, resulting in increased return loss and inefficient energy transmission. Impedance matching device 105 uses a gradient structure to gradually adjust the waveguide cross-sectional dimensions, matching the characteristic impedance of the rectangular waveguide (e.g., port 3 104) with the characteristic impedance of the circular waveguide (the entrance of the conical horn 106), reducing reflection loss. This ensures a smooth transition of the circularly polarized wave formed after passing through the stepped diaphragm 103 from the rectangular waveguide to the circular waveguide, avoiding energy dissipation caused by higher-order mode excitation.

[0030] Furthermore, the impedance matching circuit 105 comprises a four-layer rectangular structure. The sides of the four layers, arranged in ascending order of size, are A1, A2, A3, and A4; the radii of the arcs in the four layers, arranged in ascending order, are B1, B2, B3, and B4. Specifically, A1 = 1.2 mm, A2 = 0.8 mm, A3 = 0.6 mm, A4 = 0.6 mm, B1 = 0.6 mm, B2 = 1 mm, B3 = 1.3 mm, and B4 = 1.5 mm; the thickness of each layer is 0.3 mm.

[0031] By gradually changing the dimensions (decreasing side length + increasing arc radius), the waveguide cross-section transitions from the rectangular port 104 to the circular conical horn inlet 106, forming a continuous impedance transformation path. The arc transition design eliminates electromagnetic scattering from traditional right-angled edges and reduces energy loss during the conversion process, such as Joule loss caused by sudden changes in surface current.

[0032] The decreasing design of A1 > A2 > A3 simulates the tendency of rectangular waveguides to shrink at the center, creating conditions for the smooth conversion of signals to circular waveguides. A3 = A4 = 0.6mm, which can maintain a small side length in the last two layers, and with the increased arc radius (B3-B4), the cross-section is close to a circle (the side length and arc radius together determine the equivalent circle diameter).

[0033] The increasing radius of the arc sequence (B1-B4) gradually smooths the corners of the rectangular shape. The arc radius of the fourth layer (B4=1.5mm) is close to 2.5 times the side length (A4=0.6mm), making the cross-section approximately circular, which facilitates direct docking with the circular waveguide of the conical horn 106. Uniform thickness ensures consistent mechanical strength across all layers, avoiding mode distortion caused by thickness differences.

[0034] Through a four-layer gradient structure, an impedance matching bandwidth of ≥27GHz is achieved within the 96-123GHz frequency band, covering the main application scenarios of the millimeter-wave high-frequency band. The measured return loss is ≤-20dB, a significant improvement over the traditional abrupt square-to-circular structure (return loss is often >-15dB), resulting in an energy transmission efficiency increase of ≥30%. Compared to traditional multi-section stepped matching devices (which only match through abrupt size changes), this design reduces signal reflection points through continuous curvature changes, further reducing losses.

[0035] A conical horn 106 is positioned at the end of the impedance matching circuit 105 furthest from the polarizer 100, and is used to radiate circularly polarized electromagnetic signals into free space or to receive circularly polarized signals in space.

[0036] The conical structure, through its gradually widening aperture, achieves high-gain, low-sidelobe radiation characteristics. In conjunction with the impedance matching circuit 105, it ensures efficient conversion of the circularly polarized signal from waveguide mode to spatial radiation mode, improving the overall antenna efficiency.

[0037] Waveguide assembly 107 is located at the end of polarizer 100 away from impedance matching device 105, and is used to connect polarizer to external radio frequency devices, separate orthogonal polarization channels and improve isolation.

[0038] Waveguide assembly 107 is the interface unit between the internal polarizer of the antenna and the external radio frequency system (such as a signal source or receiver). In use, port 101 (orthogonal polarization channel 1) and port 102 (orthogonal polarization channel 2) of polarizer 100 can be connected to the external input and receiving ports, respectively. For example... Figure 3 As shown, the orthogonal polarization channels are separated through structural design to avoid signal crosstalk and improve polarization isolation.

[0039] Furthermore, the waveguide assembly 107 is provided with two connection ports 108, and two symmetrical 90° rectangular bend waveguides 200 are provided between the two connection ports 108 and port one 101 and port two 102 respectively.

[0040] By bending the waveguide at 90° to direct the transmission paths of port 101 and port 102 to different planes (e.g., from the longitudinal plane of the polarizer to the transverse plane), the two orthogonal polarization channels are physically separated, reducing the coupling coefficient. Furthermore, the rectangular bent waveguide only changes the direction of electromagnetic wave transmission, without altering its polarization mode (which remains TE). 10 The physical separation ensures mode consistency of the signal from the polarizer to the external port. This separation results in electromagnetic coupling between orthogonal polarization channels being ≤-25dB, a significant improvement over traditional coplanar transmission schemes. Furthermore, connection port 108 is a standard waveguide port WR-08. It can be directly connected to commercially available WR-08 band devices (such as low-noise amplifiers and waveguide-coaxial converters) without the need for custom interfaces, thus reducing system integration costs.

[0041] Furthermore, a smooth transition structure 201 is provided at the connection point between the two 90° rectangular bend waveguides 200 and the connection port 108. The smooth transition structure 201, located at the connection point between the bend waveguide and the connection port 108, is an arc transition with a gradually changing radius of curvature or an exponentially gradually changing cross-section, eliminating geometric abrupt changes at the right-angle bend, thereby reducing reflection loss. Traditional right-angle bend waveguides generate edge diffraction at the corner, leading to increased return loss. The smooth transition can reduce return loss and suppress high-order mode excitation. The gradually changing structure avoids abrupt changes in field distribution and prevents TE. 20 The generation of higher-order modules ensures the generation of the primary module (TE). 10 The purity of the model improves energy transmission efficiency.

[0042] Furthermore, the operating center frequency is 110GHz, the operating bandwidth is between 96GHz and 123GHz, the return loss is less than -20dB, the isolation is less than -25dB, and the axial ratio is less than 3dB.

[0043] The five-step gradient in height (H0=2mm→H4=0.34mm) and width (W0=0.821mm→W4=0.91mm) ensures a precise 90° phase delay at the center frequency. A thickness of 0.3mm ≈ λ / 9 (λ is the wavelength of a 110GHz electromagnetic wave in vacuum) avoids excessive compression of the waveguide's effective size due to an overly thick diaphragm while ensuring mechanical strength.

[0044] Side length A1 = 1.2 mm ≈ 0.44λ, lower than that of the rectangular waveguide TE. 10 The cutoff wavelength of the mode (λc=2a=2.4mm) ensures that the 110GHz signal can be transmitted normally. The last two layers A3=A4=0.6mm≈0.22λ, combined with the arc radii B3=1.3mm and B4=1.5mm, are close to the optimal size of the conical horn radiating aperture in this design.

[0045] B1 = 0.6 mm ≈ 0.22λ, corresponding to the corner curvature of the first layer's rectangular structure, suppressing edge diffraction of the 110 GHz signal. B4 = 1.5 mm ≈ 0.55λ, making the fourth layer nearly circular (increasing the radius of curvature reduces mode abrupt changes).

[0046] This device uses 110 GHz as the reference frequency and, through a forward design chain of "frequency-wavelength-size," transforms abstract electromagnetic theory into specific, manufacturable parameters (such as the H / W sequence of the stepped diaphragm, the A / B dimensions of the impedance matching circuit, and the WR-08 interface of the waveguide assembly). The dimensions of each component are not only geometric parameters but also carriers of electromagnetic performance—by precisely controlling the dimensions and relative positions of each structure, the device ultimately achieves synergistic optimization of indicators such as return loss, isolation, and axial ratio within a wide bandwidth of 96-123 GHz.

[0047] The above embodiments are merely illustrative of the principles and effects of this utility model and are not intended to limit the scope of this utility model. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this utility model. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this utility model should still be covered by the claims of this utility model.

Claims

1. A circularly polarized horn antenna, characterized by, include: A polarizer is used to achieve mode conversion from linearly polarized waves to circularly polarized waves; An impedance matching device is disposed at one end of the polarizer and is used for impedance matching and transition between the rectangular waveguide and the circular waveguide. A conical horn, located at the end of the impedance matching device furthest from the polarizer, is used to radiate circularly polarized electromagnetic signals into free space in a directional manner, or to receive circularly polarized signals in space. A waveguide assembly is disposed at the end of the polarizer away from the impedance matching device, and is used to connect the polarizer to external radio frequency devices, separate orthogonal polarization channels and improve isolation. The impedance matching device includes multiple stacked rectangular structures, each side of which is connected by a circular arc transition, and the size of each layer of rectangular structures increases sequentially to form a gradient stacking effect.

2. The circularly polarized horn antenna of claim 1, wherein, The impedance matching circuit comprises a four-layer rectangular structure; The four-layer rectangular structure has sides A1, A2, A3, and A4 in ascending order of size; The radii of the arcs in the four-layer rectangular structure, in ascending order, are B1, B2, B3, and B4, respectively. Wherein, A1=1.2mm, A2=0.8mm, A3=0.6mm, A4=0.6mm, B1=0.6mm, B2=1mm, B3=1.3mm, B4=1.5mm; The thickness of each rectangular-like structure is 0.3 mm.

3. The circularly polarized horn antenna of claim 1, wherein, The polarizer includes: aisle; A stepped diaphragm is disposed at the center of the channel along the length of the channel, such that one end of the channel forms port one and port two of the same size, and the end of the channel away from port one and port two forms port three; The impedance matching device is connected to port three, and the waveguide assembly is connected to port one and port two.

4. The circularly polarized horn antenna of claim 3, wherein: The stepped diaphragm is arranged in five steps at one end near port three; The heights of the steps in the stepped diaphragm from port one to port three are H0, H1, H2, H3, and H4, respectively. The widths of the steps in the stepped diaphragm are W0, W1, W2, W3, and W4 in the directions from port one to port three, respectively. Wherein, H0=2mm, H1=1.12mm, H2=0.74mm, H3=0.47mm, H4=0.34mm, W0=8.21mm, W1=0.4mm, W2=0.7mm, W3=0.7mm, W4=0.91mm, and the thickness of the stepped diaphragm is 0.3mm.

5. The circularly polarized horn antenna of claim 3, wherein, The waveguide assembly has two connection ports, and two symmetrical 90° rectangular bend waveguides are respectively provided between the two connection ports and port one and port two.

6. The circularly polarized horn antenna according to claim 5, characterized in that, The connection port is a standard waveguide port WR-08.

7. The circularly polarized horn antenna of claim 5, wherein, The two 90° rectangular bend waveguides are provided with a smooth transition structure at the connection port.

8. The circularly polarized horn antenna according to any one of claims 1-7, characterized in that, The operating center frequency is 110GHz, the operating bandwidth is between 96GHz and 123GHz, the return loss is less than -20dB, the isolation is less than -25dB, and the axis ratio is less than 3dB.

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