Dual-frequency circularly polarized antenna applied to maritime communication

Abstract

The invention discloses a dual-frequency circularly polarized antenna applied to maritime communication. The dual-frequency circularly polarized antenna comprises a first dielectric substrate, a radiation patch array, a second dielectric substrate, a slotted grounding plate and a transmission line, the radiation patch array is located on the upper surface of the first dielectric substrate, the slotted grounding plate is located between the first dielectric substrate and the second dielectric substrate, and the transmission line is located on the lower surface of the second dielectric substrate; the radiation patch array is composed of a plurality of truncated square patches arranged in the central area and parasitic patches arranged on the periphery. A cross-shaped vertical gap is formed in the center of each truncated square patch; a star-shaped notch is formed in the slotted grounding plate; the transmission line is an L-shaped planar transmission line formed by microstrip lines; the slotted grounding plate and the transmission line form a feed structure, and the circular polarization effect of the radiation patch array is excited through the feed structure. The antenna has the advantages of stable structure, low profile, dual-frequency circular polarization, broadband and the like, and can be applied to the fields of maritime wireless communication, wireless positioning and the like.

Description

Technical Field

[0001] The invention relates to the field of antenna design, and in particular to a dual-frequency circularly polarized antenna used for marine communications. Background Art

[0002] In recent years, with the rapid development of application fields such as marine exploration, marine environmental monitoring, marine disaster warning, marine safety, marine fisheries and marine transportation, the demand for marine wireless communication services has also increased. The rapid development of the fifth-generation network has brought many opportunities and promoted new applications in fields such as the Internet of Things, making it possible to connect daily indoor devices to each other during maritime navigation through a variety of wireless technologies.

[0003] As the terminal equipment of the communication system, the antenna design requires the antenna to focus on miniaturization, multi-band, easy integration, and not susceptible to interference from extreme weather at sea or other communication equipment. Microstrip antennas are often used in antenna design because of their small size, light weight, and easy integration on other objects. However, microstrip antennas also have problems such as narrowband and low gain. Summary of the invention

[0004] Purpose of the invention: In order to solve the problem that microstrip antennas used for maritime communications have a single working frequency band and a large size, and cannot meet the needs of maritime wireless communication services, the present invention discloses a dual-frequency circularly polarized antenna used for maritime communications, which has the advantages of very low profile, stable structure, good radiation performance, etc., and can achieve a dual-band circular polarization effect.

[0005] Technical solution: A dual-frequency circularly polarized antenna for marine communications, comprising: a first dielectric substrate, a radiation patch array, a second dielectric substrate, a slotted ground plate and a transmission line; the radiation patch array is located on the upper surface of the first dielectric substrate, the slotted ground plate is located between the first dielectric substrate and the second dielectric substrate, and the transmission line is located on the lower surface of the second dielectric substrate;

[0006] The radiating patch array is composed of a plurality of truncated square patches arranged in a central area and parasitic patches arranged on the surrounding areas; a cross vertical gap is arranged at the center of each truncated square patch; a star-shaped slot is opened on the slotted ground plate; the transmission line is an L-shaped planar transmission line composed of a microstrip line; the slotted ground plate and the transmission line constitute a feeding structure, and the circular polarization effect of the radiating patch array is excited by the feeding structure.

[0007] Furthermore, the parasitic patches arranged on the four sides include a first parasitic patch arranged above and below the truncated square patch, and a second parasitic patch arranged on the left and right sides of the truncated square patch. The length of the first parasitic patch is different from that of the second parasitic patch, but both are smaller than the length of the truncated square patch.

[0008] Furthermore, the first dielectric substrate and the second dielectric substrate are both rectangular dielectric substrates.

[0009] Furthermore, the parasitic patch is a rectangular parasitic patch.

[0010] Furthermore, the thicknesses of the radiation patch array, the slotted ground plate and the transmission line are all the same.

[0011] Furthermore, the star-shaped notch is obtained by etching two squares of different sizes in the center of the notched ground plate, and the two squares are etched in an offset manner so that the star-shaped notch has 8 right angles.

[0012] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0013] (1) The present invention adopts an L-shaped planar transmission line structure feeding structure, which is easy to integrate into a circuit or device, and the feeding structure of the present invention eliminates winding, vias and corresponding parasitic source inductance, reduces the radiation loss caused by surface waves, and increases the antenna gain and bandwidth; and the application of the L-shaped planar transmission line feeding structure of the present invention can effectively stimulate the circular polarization effect of the surface radiation patch, and at the same time, combined with the cross-slot structure on the center patch of the array, the cross-section height of the antenna can be greatly reduced;

[0014] (2) The present invention adopts the method of adding parasitic patches to design the antenna. The introduction of parasitic patches has obvious advantages in improving the directivity of the antenna, enhancing its circular polarization performance and expanding the working bandwidth of the antenna.

[0015] (3) The present invention uses truncated square patch units to form an array. The truncated square patch and the cross-shaped gap in the middle change the direction of the surface current flow, so that the current achieves a 90° equal amplitude phase difference, producing a circular polarization effect;

[0016] (4) The present invention performs star-shaped slots on the ground plane between the two dielectric substrates. By analyzing the surface current, it is found that the addition of the star-shaped slots directly changes the trajectory of the current. The current flows along the edge and forms a 90° phase difference, thereby enhancing the bandwidth of circular polarization and the impedance matching of the antenna.

[0017] (5) The antenna of the present invention has the advantages of stable structure, low profile, dual-frequency circular polarization and broadband, and can be applied to fields such as marine wireless communication and wireless positioning. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic diagram of the overall structure of a dual-frequency circularly polarized antenna for maritime communications proposed in an embodiment, including a top view, a bottom view, a side view, and a star-shaped ground plate between an F4BM220 dielectric substrate and an FR-4 dielectric substrate;

[0019] Figure 2 The figure is the result of antenna simulation and test return loss (S11), where the horizontal axis represents the frequency (GHz) and the vertical axis represents the return loss intensity (dB);

[0020] Figure 3 This is the result diagram of antenna simulation and test axial ratio;

[0021] Figure 4 Left-hand circular polarization and right-hand circular polarization E-plane radiation patterns for antenna simulation and testing;

[0022] Figure 5 Left-hand circularly polarized and right-hand circularly polarized H-plane radiation patterns for antenna simulation and testing. DETAILED DESCRIPTION

[0023] Circularly polarized antennas have attracted widespread attention in wireless communication systems because of their strong anti-interference and arbitrary transmission and reception polarization. Circularly polarized electromagnetic waves, as a field rotating with equal amplitude, can be decomposed into two linearly polarized electromagnetic waves with the same amplitude and a phase difference of 90°. If an antenna radiates left-handed circularly polarized waves, it can only receive left-handed circularly polarized waves and cannot receive right-handed circularly polarized waves. When circularly polarized electromagnetic waves encounter obstacles, the polarization will be reversed, and the rotation direction of the reflected wave will be inconsistent with that of the incident wave. Therefore, the use of circularly polarized antennas can reduce interference in harsh environments and resist multipath reflections. At the same time, the circularly polarized waves sent by circularly polarized antennas can be received by linearly polarized antennas in any direction, and circularly polarized receiving antennas can receive incoming linearly polarized waves in any direction. Therefore, they are widely used in satellite communications and reconnaissance interference.

[0024] The technical solution of this embodiment is now further described in conjunction with the accompanying drawings and embodiments.

[0025] like Figure 1 As shown, this embodiment discloses a dual-frequency circularly polarized antenna for marine communications, such as Figure 1 As shown, it includes: a F4BM220 dielectric substrate 1, a radiation patch array 2 located on the upper surface of the F4BM220 dielectric substrate 1, a FR-4 dielectric substrate 7, a slotted ground plate 8 located between the F4BM220 dielectric substrate and the FR-4 dielectric substrate 7, and an L-shaped planar transmission line 9 located at the bottom of the FR-4 dielectric substrate 7.

[0026] Among them, the radiation patch array 2 used in this embodiment is composed of 2×2 truncated square patches 3, a first rectangular parasitic patch 4 located at the upper and lower ends, and a second rectangular parasitic patch 5 located at the left and right sides. A cross vertical slit 6 is arranged at the center of each truncated square patch 3. The purpose of opening the cross vertical slit 6 is to change the direction of current flow. Through surface current analysis, the increase of the cross vertical slit directly changes the current trajectory, and the current flows around the cross vertical slit from the upper and lower ends. The cross vertical slit increases the effective mode, and the multi-mode resonance produces a broadband effect. Under the joint action of multiple modes, the circular polarization requirements are met between every two modes, and the circular polarization effect of the antenna is optimized.

[0027] In this embodiment, the lengths of the first rectangular parasitic patch 4 and the second rectangular parasitic patch 5 are slightly smaller than the length of the truncated square patch, and the sizes of the first rectangular parasitic patch 4 and the second rectangular parasitic patch 5 are different. The resonance frequency of the rectangular parasitic patch used is higher than the resonance frequency of the truncated square patch. By adding parasitic patches of appropriate size, the working frequency band is shifted to the low-frequency part, the bandwidth of the antenna is widened, and a new circular polarization effect is generated in the low-frequency part. In this embodiment, by adding rectangular parasitic patches around the truncated square patch 3, the introduction of the rectangular parasitic patches effectively induces high-order mode resonance, thereby expanding the working bandwidth of the antenna.

[0028] like Figure 1 As shown, the slotted ground plate 8 and the L-shaped planar transmission line 9 constitute a coplanar waveguide feeding structure. The slot of the slotted ground plate 8 is a star-shaped structure, which increases the trajectory of the current, helps the antenna to strengthen the impedance matching and optimizes the circular polarization effect of the antenna. The star-shaped structure is obtained by etching two squares with sizes of 32mm×32mm and 28mm×28mm in the center of the slotted ground plate 8, and the two squares are staggered and etched so that the star-shaped slot has 8 right angles. . The L-shaped planar transmission line 9 consists of a short microstrip line and two long microstrip lines, wherein the two long microstrip lines constitute an L-shaped structure. Specifically, the size of the short microstrip line used in this embodiment is 8mm×1.5mm, and the size of the long microstrip line is 30mm×6mm and 16mm×8mm, respectively. The L-shaped planar transmission line 9 used in this embodiment is easy to integrate into a circuit or device. The coplanar waveguide feeding structure adopted in this embodiment is simple to manufacture and has a compact structure. It eliminates windings, vias and corresponding parasitic source inductance, reduces radiation losses caused by surface waves, and increases antenna gain. The application of the coplanar waveguide feeding structure can more effectively stimulate the circular polarization effect of the antenna radiation patch. At the same time, combined with the slot structure, the cross-sectional height of the antenna is greatly reduced.

[0029] In this embodiment, the size of each truncated square patch in the truncated square patch 3 is 10mm×10mm, the truncated corner size is 3mm, the long side of the cross vertical gap 6 is 12mm×1mm, and the short side is 4mm×1mm. The size of the first rectangular parasitic patch 4 is 7mm×5.5mm, and the size of the second rectangular parasitic patch 5 is 14mm×4.75mm. In this embodiment, the relative dielectric constant of the F4BM220 dielectric substrate 1 is 2.2, the shape is rectangular, the size is 53mm×53mm, and the thickness is 3mm. The relative dielectric constant of the FR-4 dielectric substrate 7 is 4.4, the shape is rectangular, the size is 53mm×53mm, and the thickness is 0.813mm. The thickness of the radiation patch array 2, the slotted ground plate 8 and the L-shaped planar transmission line 9 proposed in this embodiment is 0.018mm.

[0030] Figure 2 The simulation and test return loss (S11) result diagrams of the dual-frequency circularly polarized antenna proposed in this embodiment are given. The simulation results show that the -10dB impedance bandwidth is 55.64% (2.23GHz-3.25GHz), and the test results show that the -10dB impedance bandwidth is 58.29% (3.48GHz-5.80GHz).

[0031] Figure 3 The simulation and test gain result diagram and axial ratio result diagram of the dual-frequency circularly polarized antenna proposed in this embodiment are given. At low frequency, the maximum gain is 4.53dBic; at high frequency, the maximum gain is 5.89dBic. At low frequency, the 3dB axial ratio bandwidth is 18.9% (2.32-2.77GHz), and at high frequency, the 3dB axial ratio bandwidth is 9.2% (4.65-5.20GHz).

[0032] Figure 4 The left-hand circularly polarized and right-hand circularly polarized E-plane and H-plane radiation patterns of the single-layer dual-frequency circularly polarized metasurface antenna proposed in this embodiment are simulated and tested in the low-frequency part.

[0033] Figure 5 The left-hand circularly polarized and right-hand circularly polarized E-plane and H-plane radiation patterns of the single-layer dual-frequency circularly polarized metasurface antenna proposed in this embodiment are simulated and tested in the high-frequency part.

[0034] Compared with conventional circularly polarized antennas, the dual-frequency circularly polarized antenna proposed in this embodiment innovatively cuts a cross vertical gap in the middle of the truncated square patch, and then adds a rectangular parasitic patch around the surface radiation patch. The introduction of the parasitic patch effectively induces high-order mode resonance and expands the working bandwidth of the antenna. Star-shaped slots are implemented on the ground plane to increase the current trajectory, helping the antenna to strengthen impedance matching while optimizing the circular polarization effect of the antenna.

Claims

1. A dual-frequency circularly polarized antenna for marine communications, characterized in that: include: a first dielectric substrate, a radiation patch array, a second dielectric substrate, a slotted ground plate, and a transmission line; The radiation patch array is located on the upper surface of the first dielectric substrate, the slotted ground plate is located between the first dielectric substrate and the second dielectric substrate, and the transmission line is located on the lower surface of the second dielectric substrate; The radiating patch array is composed of a plurality of truncated square patches arranged in a central area and parasitic patches arranged on the surrounding areas; a cross vertical gap is arranged at the center of each truncated square patch; a star-shaped slot is opened on the slotted ground plate; the transmission line is an L-shaped planar transmission line composed of a microstrip line; the slotted ground plate and the transmission line constitute a feeding structure, and the circular polarization effect of the radiating patch array is excited by the feeding structure.

2. The dual-frequency circularly polarized antenna for marine communications according to claim 1, characterized in that: The parasitic patches arranged on the four sides include a first parasitic patch arranged above and below the truncated square patch, and a second parasitic patch arranged on the left and right sides of the truncated square patch. The length of the first parasitic patch is different from that of the second parasitic patch, but both are smaller than the length of the truncated square patch.

3. The dual-frequency circularly polarized antenna for marine communication according to claim 1, characterized in that: The first dielectric substrate and the second dielectric substrate are both rectangular dielectric substrates.

4. The dual-frequency circularly polarized antenna for marine communications according to claim 1, characterized in that: The parasitic patch is a rectangular parasitic patch.

5. The dual-frequency circularly polarized antenna for marine communication according to claim 1, characterized in that: The thicknesses of the radiation patch array, the slotted ground plate and the transmission line are all the same.

6. The dual-frequency circularly polarized antenna for marine communications according to claim 1, characterized in that: The star-shaped notch is obtained by etching two squares of different sizes in the center of the notched ground plate. The two squares are etched in an offset manner so that the star-shaped notch has eight right angles.

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