Dual-Frequency Dual-Circularly Polarized Antenna Based on Traveling-Wave Series-Feed Mechanism

Abstract

The present invention discloses a dual - frequency dual - circularly polarized antenna based on a traveling - wave sequence feeding mechanism, comprising: a radiation structure and a feeding network. The feeding network includes a cross - slot and an Ω - shaped feeder. Each end of the Ω - shaped feeder is provided with a port, namely a first feeding port and a second feeding port respectively. The stacked dual - frequency metasurface is excited by the cross - slot. By exciting different feeding ports, clockwise or counter - clockwise sequence feeding is performed on the stacked dual - frequency metasurface to achieve circular polarization characteristics in two frequency bands. Compared with traditional dual - frequency dual - circularly polarized antennas, the feeding network of the present invention has a simple structure, can be flexibly designed according to the target frequency band, has the advantages of miniaturization and low cost, and can be applied to multi - frequency compatible common - aperture phased arrays.

Description

Technical Field

[0001] The present invention relates to the field of communications, and particularly to a dual - frequency dual - circularly - polarized antenna based on a traveling - wave sequence feeding mechanism. Background Art

[0002] Due to its good anti - interference ability and the arbitrariness of receiving and transmitting polarizations, circularly - polarized antennas have been widely used in satellite communications. Based on the higher requirements of wireless communication systems for antenna performance, circularly - polarized antennas also need new breakthroughs in improving channel capacity and frequency reuse. To solve these problems, antennas with dual - frequency dual - circular - polarization capabilities have received extensive attention. For the design of traditional planar dual - frequency dual - circular - polarized antennas, not only does the radiation structure need to have dual - frequency characteristics, but the feeding network also needs to provide the required phase gradient within both frequency bands, and this phase gradient is usually 90°. To achieve bidirectional circular polarization, the feeding network also needs to provide a phase gradient of ±90° within both frequency bands, which often leads to antennas having complex structures, being difficult to design, and generally having large sizes. In addition, if low - cost and lightweight antennas are to be further realized on the basis of achieving a wide beam coverage, multi - frequency common - aperture phased arrays are a solution. This requires antennas to have the advantages of miniaturization and simple structure while having strong circular - polarization capabilities. Summary of the Invention

[0003] In order to overcome the above - mentioned shortcomings and deficiencies of the prior art, the purpose of the present invention is to provide a dual - frequency dual - circularly - polarized antenna based on a traveling - wave sequence feeding mechanism.

[0004] This antenna can achieve dual - frequency operation under the condition of a single feeding network and can achieve bidirectional circular - polarization radiation within each frequency band. When the same port is excited, the circular polarizations of the two operating frequency bands have the same sense of rotation. The present invention not only has the characteristics of small size, simple structure, and flexible design, but also can be applied to wide - angle scanning phased arrays with multi - frequency common - aperture.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A dual - frequency dual - circularly - polarized antenna based on a traveling - wave sequence feeding mechanism, comprising:

[0007] A radiation structure, including a stacked dual - frequency metasurface;

[0008] A feeding network, including a cross - slot and an Ω - shaped feeder. Each end of the Ω - shaped feeder is provided with a port, which are a first feeding port and a second feeding port respectively;

[0009] The stacked dual - frequency metasurface is excited by the cross - slot. By exciting different feeding ports, clockwise or counter - clockwise sequence feeding is performed on the stacked dual - frequency metasurface to achieve circular - polarization characteristics in two frequency bands;

[0010] The cross-shaped slot is a non-uniform cross-shaped slot, which is symmetric about an axis of symmetry of the stacked dual-band metasurface, and the position of its center is aligned with the center position of the stacked dual-band metasurface. The included angle between two adjacent slot arms is 90°. The lengths and widths of the two slot arms forming an angle with the negative half-axis of the x-axis are greater than those of the two slot arms forming an angle with the positive half-axis of the x-axis.

[0011] Furthermore, by adjusting the dimensions of the cross-shaped slot arms, the coupling strength of the energy on the feeder line by each slot arm is controlled. When the phase gradient deviates from 90°, circular polarization characteristics can be achieved in both frequency bands, and high isolation between the two ports can be realized.

[0012] Furthermore, it successively includes a first dielectric substrate, a second dielectric substrate, a third dielectric substrate, and a fourth dielectric substrate from top to bottom. An upper metal floor is arranged on the upper surface of the third dielectric substrate. A stacked dual-band metasurface is arranged on the upper surfaces of the first dielectric substrate and the second dielectric substrate. A lower metal floor is arranged on the lower surface of the fourth dielectric substrate. A cross-shaped slot is etched on the upper metal floor. An Ω-shaped feeder line is arranged on the upper surface of the fourth dielectric substrate.

[0013] Furthermore, the stacked dual-band metasurface includes:

[0014] An upper metasurface for enhancing the energy coupling between the radiation structure and the feeding network at low frequencies;

[0015] A lower metasurface for enhancing the energy coupling between the radiation structure and the feeding network at high frequencies.

[0016] Furthermore, the upper metasurface is composed of 2×2 first radiation patch units arranged in an array, and the lower metasurface is composed of 4×4 second radiation patch units arranged in an array.

[0017] Furthermore, the dimensions of the first radiation patch units of the upper metasurface and the second radiation patch units of the lower metasurface are determined according to specific target frequency bands to achieve good impedance matching within the two frequency bands and high isolation between ports, and the arrangement form is not limited.

[0018] Furthermore, the stacked dual-band metasurface is a stacked dual-band microstrip patch, a single-layer dual-band metasurface, a single-layer dual-band microstrip patch, or a single-layer or stacked combination of a single-frequency structure and a dual-frequency structure.

[0019] Furthermore, it further includes isolation metal columns. The isolation metal columns connect the upper metal floor and the lower metal floor and are arranged around the Ω-shaped feeder line for suppressing field leakage and the backward radiation of the cross-shaped slot.

[0020] Further, the center position of the circular Ω-shaped feeder is aligned with the center position of the cross slot, and the radius of the circular feeder determines the phase gradient of the sequential feeding.

[0021] A communication device includes the dual-band dual-circularly polarized antenna described above.

[0022] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0023] (1) The present invention includes a feeding network and a stacked dual-band metasurface based on a dual-port traveling-wave sequential feeding mechanism. Since the metasurface is used as the radiation structure, stable circular polarization performance can be achieved, and miniaturization of the unit is realized.

[0024] (2) The present invention realizes bidirectional circular polarization through a dual-port traveling-wave sequential feeding network, and has a simple and compact feeding network structure.

[0025] (3) By adjusting the size of each slot arm of the cross slot, the present invention adjusts the coupling strength of each slot arm to the energy of different frequency bands, and finally realizes circular polarization radiation even under the condition of a non-90° phase gradient, enabling the antenna to meet the dual-band dual-circular polarization characteristics.

[0026] (4) The present invention has a simple structure, flexible design, and the advantage of miniaturization, and can be applied to wide-angle scanning phased arrays with multi-frequency common apertures. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a three-dimensional view of the present invention;

[0028] Figure 2 is a side view of the present invention

[0029] Fig. 3(a) is a top view of the upper metasurface of the present invention;

[0030] Fig. 3(b) is a top view of the lower metasurface of the present invention;

[0031] Fig. 4(a) is a top view of the upper floor with an etched axially symmetric non-uniform cross slot of the present invention;

[0032] Fig. 4(b) is a top view of the dual-port Ω-shaped feeder of the present invention;

[0033] Figure 5 is the S-parameter curve and axial ratio curve of the present invention;

[0034] Fig. 6(a) is the axial ratio beamwidth curve of the xoz plane and yoz plane of the present invention at the low frequency of 19.6 GHz;

[0035] Fig. 6(b) is the axial ratio beamwidth curve of the xoz plane and yoz plane of the present invention at the low frequency of 28.7 GHz;

[0036] Figure 7(a) shows the gain curves of the main polarization and cross polarization at low frequencies when the first feeding port of the present invention is excited;

[0037] Figure 7(b) shows the gain curves of the main polarization and cross polarization at high frequencies when the first feeding port of the present invention is excited;

[0038] Figure 8(a) shows the gain curves of the main polarization and cross polarization of the xoz plane and yoz plane at a low frequency of 19.6 GHz when the first feeding port of the present invention is excited;

[0039] Figure 8(b) shows the gain curves of the main polarization and cross polarization of the xoz plane and yoz plane at a low frequency of 20 GHz when the first feeding port of the present invention is excited;

[0040] Figure 9(a) shows the gain curves of the main polarization and cross polarization of the xoz plane and yoz plane at a high frequency of 28.7 GHz when the first feeding port of the present invention is excited;

[0041] Figure 9(b) shows the gain curves of the main polarization and cross polarization of the xoz plane and yoz plane at a high frequency of 29 GHz when the first feeding of the present invention is excited; Detailed implementation manner

[0042] The present invention will be further described in detail below in conjunction with embodiments, but the implementation manners of the present invention are not limited thereto.

[0043] As Figure 1 and Figure 2 shown, a dual - frequency dual - circularly polarized antenna based on a traveling - wave sequence feeding mechanism includes: from top to bottom, a first dielectric substrate 7, a second dielectric substrate 8, a third dielectric substrate 10, and a fourth dielectric substrate 11.

[0044] Radiating structures are provided on the upper surfaces of the first dielectric substrate 7 and the second dielectric substrate 8. The radiating structures include a stacked dual - frequency metasurface 1, and the stacked dual - frequency metasurface can be a stacked dual - frequency microstrip patch, a single - layer dual - frequency metasurface, a single - layer dual - frequency microstrip patch, or a single - layer or stacked combination of a single - frequency structure and a dual - frequency structure.

[0045] In this embodiment, it is preferably as follows: as shown in FIGS. 3(a) and 3(b), the stacked dual-band metasurface includes an upper metasurface and a lower metasurface. The upper metasurface is disposed on the upper surface of the first dielectric substrate 7, and the lower metasurface is disposed on the upper surface of the second dielectric substrate 8. The upper metasurface is composed of 2×2 first radiation patch units arranged in an array, and the lower metasurface is composed of 4×4 second radiation patch units arranged in an array. The first radiation patch unit and the second radiation patch unit have the same shape, and the size is determined according to the specific target frequency band to achieve good impedance matching within two frequency bands and high isolation between ports. The arrangement form is not limited.

[0046] The upper metasurface mainly enhances the energy coupling between the radiation structure and the cross slot at low frequencies. The second radiation patch units of the lower metasurface have smaller sizes and are used to enhance the energy coupling between the radiation structure and the cross slot at high frequencies, ultimately realizing the dual-band resonance characteristics of the antenna and ensuring high isolation between the first feeding port and the second feeding port within each frequency band.

[0047] The size s1 of the upper metasurface is [0.1λ, 0.15λ], and the periodic distance g1 is [0.008λ, 0.01λ]; the size s2 of the lower metasurface unit is [0.05λ, 0.07λ], and the periodic distance g2 is [0.008λ, 0.011λ]. In this embodiment, the overall sizes of the upper metasurface unit and the lower metasurface unit are the same, specifically [0.22λ, 0.32λ]. Wherein, λ is the free space wavelength corresponding to the center frequency.

[0048] An upper metal floor 9 is disposed on the upper surface of the third dielectric substrate 10, a lower metal floor 12 is disposed on the lower surface of the fourth dielectric substrate 11, a cross slot 2 is etched on the upper metal floor 9, an Ω-shaped feeder 4 is disposed on the upper surface of the fourth dielectric substrate 11, and each end of the Ω-shaped feeder 4 is provided with a port, which are a first feeding port 5 and a second feeding port 6 respectively.

[0049] The stacked dual-band metasurface is excited by the cross slot. By exciting different feeding ports, sequential feeding in a clockwise or counterclockwise direction is performed on the stacked dual-band metasurface, and a corresponding phase gradient is formed. For the two target frequency bands, the lengths of the feeders at the feeding points on the adjacent slot arms are not 1 / 4 wavelength, which means that the phase gradient is not 90° for both frequency bands. However, by adjusting the size of the slot arms, the coupling strength of the energy on the feeder by each slot arm can be controlled. In the case of deviating from the 90° gradient, circular polarization characteristics can be achieved for both frequency bands, and high isolation between the first feeding port 5 and the second feeding port 6 can be realized.

[0050] As shown in Fig. 4(a), the cross slot is a non-uniform cross slot, which is symmetric about an axis of symmetry of the stacked dual-frequency metasurface. The center of the cross slot is aligned with the center of the stacked dual-frequency metasurface. The angle between adjacent two slot arms is 90°. The lengths and widths of the two slot arms forming an angle with the negative x-axis are greater than those of the two slot arms forming an angle with the positive x-axis.

[0051] As shown in Fig. 4(b), further, the center of the circular ring-shaped feeder part of the Ω-shaped feeder 4 is aligned with the center of the cross slot, and the radius of the circular ring-shaped feeder part determines the phase gradient of the sequential feeding.

[0052] The width of the Ω-shaped feeder 4 is [0.018λ, 0.027λ], the radius rf of the circular ring-shaped feeder part is [0.046λ, 0.067λ], the length lf1 of the vertical feeder along the x-axis is [0.036λ, 0.052λ], and the length lf0 of the horizontal feeder along the y-axis is [0.159λ, 0.232λ]. The diameter rp of the isolation metal column 3 is [0.01λ, 0.015λ], and the center distance dp between adjacent isolation metal columns is [0.02λ, 0.03λ]. The distance df between the isolation metal column and the horizontal feeder along the y-axis is [0.035λ, 0.051λ], and the distance dr between two rows of vertical metal columns arranged along the x-axis is [0.28λ, 0.41λ]. Here, λ is the free space wavelength corresponding to the center frequency.

[0053] The isolation metal column connects the upper metal floor and the lower metal floor and surrounds the Ω-shaped feeder to prevent field leakage and suppress the back radiation of the slot.

[0054] In this embodiment, the dielectric constants of the first dielectric substrate, the second dielectric substrate, the third dielectric substrate and the fourth dielectric substrate are 3.48, and the thicknesses are [0.02λ, 0.03λ], [0.03λ, 0.05λ], [0.006λ, 0.01λ] and [0.022λ, 0.032λ] respectively. The thicknesses of the upper metal floor 9 and the lower metal floor 12 are [0.0012λ, 0.0017λ]. Here, λ is the free space wavelength corresponding to the center frequency.

[0055] The overall size wg of the dual-frequency dual-circular polarization antenna based on the dual-port traveling wave sequential feeding mechanism is [0.36λ, 0.524λ]. Here, λ is the free space wavelength corresponding to the center frequency.

[0056] In this embodiment, the specific dimensions of the dual-frequency dual-circular polarization antenna based on the dual-port traveling wave sequential feeding mechanism are as follows:

[0057] The size s1 of the 2×2 upper metasurface is 1.6 mm, and the period distance g1 is 0.12 mm; the size s2 of the 4×4 lower metasurface is 0.74 mm, and the period distance g2 is 0.12 mm. The overall size of the upper metasurface and the lower metasurface is the same, which is 3.32 mm.

[0058] For the cross slot 2, the sizes ls1 and ws1 of the two slot arms near the positive half-axis of the x-axis are 1.65 mm and 0.1 mm respectively. The sizes ls2 and ws2 of the two slot arms near the negative half-axis of the x-axis are 1.95 mm and 0.3 mm respectively.

[0059] The width of the Ω-shaped feeder 4 is 0.28 mm, the radius rf of the circular-ring feeder part is 0.7 mm, the length lf1 of the vertical feeder along the x-axis direction is 0.55 mm, and the length lf0 of the horizontal feeder along the y-direction is 2.43 mm. The diameter rp of the metal isolation post 3 is 0.16 mm, and the center distance dp of adjacent metal posts is 0.32 mm. The distance df between the metal isolation post and the horizontal feeder along the y-direction is 0.54 mm, and the distance dr between the two rows of vertical metal posts arranged along the x-direction is 4.32 mm.

[0060] The specific sizes of the dielectric substrates are as follows: the first dielectric substrate, the second dielectric substrate, the third dielectric substrate, and the fourth dielectric substrate all adopt Rogers 4350b, with a dielectric constant of 3.48, and the thicknesses are 0.3 mm, 0.5 mm, 0.1 mm, and 0.338 mm respectively. The thicknesses of the upper metal floor 9 and the lower metal floor 12 are 0.018 mm.

[0061] The overall size wg of the dual-band dual-circularly polarized antenna based on the dual-port traveling-wave sequential feeding mechanism is 5.5 mm.

[0062] When the first feeding port 5 is excited and the second feeding port 6 is connected to a 50-ohm matching load, a counterclockwise sequential feeding and phase gradient are generated, and left-handed circular polarization is generated for both the low frequency and the high frequency. On the contrary, when the second feeding port 6 is excited and the first feeding port 5 is connected to a 50-ohm matching load, a clockwise sequential feeding and phase gradient are generated, and right-handed circular polarization is generated for both the low frequency and the high frequency.

[0063] As Figure 5 shown, the dual-band dual-circularly polarized antenna based on the dual-port traveling-wave sequential feeding mechanism has a working bandwidth of 18.8 - 20.4 GHz for the low frequency and 28.1 GHz - 29.1 GHz for the high frequency. Within the working frequency band, the port reflection coefficient is lower than -10 dB, the port polarization isolation is better than 10 dB, and the axial ratio is less than 3 dB. Due to the symmetry of the antenna structure, the reflection coefficients of the second feeding port 6 and the first feeding port 5 are almost exactly the same, indicating that the antenna can achieve exactly the same dual-circularly polarized radiation.

[0064] As shown in FIGS. 6(a) and 6(b), for the dual-frequency dual-circularly polarized antenna based on the dual-port traveling-wave sequence feeding mechanism, when the first feeding port 5 is excited and the second feeding port 6 is connected to a 50-ohm matching load, the 3-dB axial ratio beamwidth at the low frequency of 19.6 GHz is greater than 174°, at the high frequency of 28.7 GHz, the 3-dB axial ratio beamwidth in the xoz plane is greater than 123°, and the 3-dB axial ratio beamwidth in the yoz plane is greater than 177°.

[0065] As shown in FIGS. 7(a) and 7(b), for the dual-frequency dual-circularly polarized antenna based on the dual-port traveling-wave sequence feeding mechanism, when the first feeding port 5 is excited and the second feeding port 6 is connected to a 50-ohm matching load, the low-frequency main polarization, i.e., the left-handed circular polarization gain, is greater than 4.8 dBi, and the cross polarization, i.e., the right-handed circular polarization gain, is below -20 dBi; the high-frequency main polarization, i.e., the left-handed circular polarization gain, is greater than 5.8 dBi, and the cross polarization, i.e., the right-handed circular polarization gain, is less than -9 dBi.

[0066] As shown in FIGS. 8(a) and 8(b), for the dual-frequency dual-circularly polarized antenna based on the dual-port traveling-wave sequence feeding mechanism, when the first feeding port 5 is excited and the second feeding port 6 is connected to a 50-ohm matching load, at different low frequencies, the radiation patterns of the antenna are basically symmetric in the xoz and yoz planes, and the cross polarization is suppressed to below -20 dB.

[0067] As shown in FIGS. 9(a) and 9(b), for the dual-frequency dual-circularly polarized antenna based on the dual-port traveling-wave sequence feeding mechanism, when the first feeding port 5 is excited and the second feeding port 6 is connected to a 50-ohm matching load, at different high frequencies, the radiation patterns of the antenna are basically symmetric in the xoz and yoz planes, and the cross polarization is suppressed to below -15 dB.

[0068] An embodiment of the present invention further provides a communication device, including the dual-frequency dual-circularly polarized antenna described above.

[0069] As can be seen from the above, the dual-frequency dual-circularly polarized antenna of the present invention based on the dual-port traveling-wave sequence feeding mechanism achieves stable circular polarization performance in two frequency bands. And due to the symmetry of the antenna structure, the circular polarization performances with different rotation directions in the two frequency bands are consistent, simplifying the complex design of the traditional planar dual-frequency dual-circularly polarized antenna and being applicable to the wide-angle scanning phased array with multi-frequency common aperture.

[0070] The above embodiments are the preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A dual - frequency and dual - circularly polarized antenna based on a traveling - wave sequence feeding mechanism, characterized in that, Comprising: A radiation structure including a stacked dual - frequency metasurface; A feeding network including a cross - slot and a Ω - shaped feeder. Each end of the Ω - shaped feeder is provided with a port, namely a first feeding port and a second feeding port respectively; The stacked dual - frequency metasurface is excited by the cross - slot. By exciting different feeding ports, sequential feeding of the stacked dual - frequency metasurface in a clockwise or counter - clockwise direction is performed to achieve circular polarization characteristics in two frequency bands; The cross-shaped slot is a non-uniform cross-shaped slot, symmetric about an axis of symmetry of the stacked dual-band metasurface, and the position of its center is aligned with the center position of the stacked dual-band metasurface. The included angle between two adjacent slot arms is 90°. The lengths and widths of the two slot arms forming an angle with the negative half-axis of the x axis are greater than those of the two slot arms forming an angle with the positive half-axis of the x axis; By adjusting the size of the cross - shaped slot arms, the coupling strength of the energy on the feeder by each slot arm is controlled. When the phase gradient deviates from 90°, circular polarization characteristics can be achieved in both frequency bands, and high isolation between the two ports can be realized; It sequentially includes a first dielectric substrate, a second dielectric substrate, a third dielectric substrate, and a fourth dielectric substrate from top to bottom. An upper metal floor is provided on the upper surface of the third dielectric substrate. A stacked dual - frequency metasurface is provided on the upper surfaces of the first dielectric substrate and the second dielectric substrate. A lower metal floor is provided on the lower surface of the fourth dielectric substrate. The cross - slot is etched on the upper metal floor, and the Ω - shaped feeder is provided on the upper surface of the fourth dielectric substrate.

2. The dual - frequency and dual - circularly polarized antenna according to claim 1, characterized in that, The stacked dual - frequency metasurface includes: An upper - layer metasurface for enhancing the energy coupling between the radiation structure and the feeding network at low frequencies; A lower - layer metasurface for enhancing the energy coupling between the radiation structure and the feeding network at high frequencies.

3. The dual - frequency and dual - circularly polarized antenna according to claim 2, characterized in that, The upper - layer metasurface is composed of 2×2 first radiation patch units arranged in an array, and the lower - layer metasurface is composed of 4×4 second radiation patch units arranged in an array.

4. The dual - frequency and dual - circularly polarized antenna according to claim 2, characterized in that, The sizes of the first radiation patch units of the upper - layer metasurface and the second radiation patch units of the lower - layer metasurface are determined according to specific target frequency bands to achieve good impedance matching within two frequency bands and high isolation between ports, and the arrangement form is not limited.

5. The dual - frequency and dual - circularly polarized antenna according to claim 2, characterized in that, The stacked dual - frequency metasurface is a stacked dual - frequency microstrip patch, a single - layer dual - frequency metasurface, a single - layer dual - frequency microstrip patch, or a single - layer or stacked combination of a single - frequency structure and a dual - frequency structure.

6. The dual - frequency and dual - circularly polarized antenna according to claim 1, characterized in that, It further includes isolation metal posts. The isolation metal posts connect the upper metal floor and the lower metal floor and are arranged around the Ω - shaped feeder to suppress field leakage and the backward radiation of the cross - slot.

7. The dual - frequency and dual - circularly polarized antenna according to claim 1, characterized in that, The center position of the circular - shaped feeder of the Ω - shaped feeder is aligned with the center position of the cross - slot, and the radius of the circular ring of the circular - shaped feeder determines the phase gradient of the sequential feeding.

8. A communication device, characterized in that, Including the dual - frequency dual - circular - polarization antenna according to any one of claims 1 - 7.

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