Low-profile circularly-polarized frequency-reconfigurable omnidirectional antenna

Abstract

The invention discloses a low-profile circularly-polarized frequency-reconfigurable omnidirectional antenna, which comprises a dielectric substrate, an arc-shaped spiral arm, a phase compensation line, a main radiation patch, a ground plane, a radiation via hole and a direct-current via hole, wherein the arc-shaped spiral arm, the phase compensation line and the main radiation patch are arranged on the upper surface of the dielectric substrate; the ground plane is arranged on the lower surface of the dielectric substrate; frequency reconstruction is achieved through a variable capacitance diode, and the capacitance value of the variable capacitance diode changes between 1.30 pF and 0.15 pF along with 0-18 V bias voltage applied to a direct current via hole. The inductor is used for isolating interference of radio frequency on direct current bias, and the capacitor is used for isolating direct current and providing a path for the radio frequency. The groove around the dielectric substrate is equivalent to a magnetic current source, the arc-shaped spiral arm is equivalent to a current source, the magnetic current source and the arc-shaped spiral arm generate a 90-degree phase difference through a phase compensation line, and circular polarization radiation is achieved. The overall size of the antenna is 36mm * 36mm * 1.575 mm. The antenna has the advantages of low profile, adjustable frequency and omnidirectional circular polarization, and is suitable for the fields of wireless communication, satellite navigation, Internet of Things and the like.

Description

Technical Field

[0001] This invention relates to the field of antenna technology, specifically providing a low-profile circularly polarized frequency-reconfigurable omnidirectional antenna, suitable for scenarios such as wireless communication, satellite navigation, and the Internet of Things where there are strict requirements for antenna profile height, frequency adjustability, and polarization. Background Technology

[0002] In modern wireless communication systems, antennas are key components for signal transmission and reception, and their performance directly affects the quality of the entire communication system. As electronic devices become increasingly miniaturized and integrated, there are ever-lower requirements for antenna profile height. Low-profile antennas can better integrate with the device carrier, reducing space occupation. Meanwhile, to adapt to the needs of different communication frequency bands, frequency-reconfigurable antennas have become a research hotspot. These antennas can adjust their operating frequency through external control without changing the antenna's physical structure, improving the antenna's versatility and flexibility.

[0003] Compared to linearly polarized antennas, circularly polarized antennas offer advantages such as resistance to multipath interference and the elimination of the need for precise alignment, leading to their widespread application in satellite communications and navigation. Isotropic radiation ensures effective signal transmission and reception in all directions, expanding communication coverage. However, current technologies for antennas simultaneously possessing low profile, frequency reconfigurability, and omnidirectional circular polarization radiation characteristics still have several shortcomings: some antennas, while achieving low profile and omnidirectional radiation, lack frequency reconfigurability, making them unsuitable for multi-band communication needs; others with frequency reconfigurability suffer from high profile height, poor circular polarization performance, or limited radiation directionality, failing to meet the application requirements of miniaturized, high-performance communication equipment. Therefore, developing an antenna that combines low profile, frequency reconfigurability, and omnidirectional circular polarization radiation characteristics is of significant practical importance. Summary of the Invention

[0004] To achieve the above-mentioned objectives, the technical solution adopted by the present invention is as follows:

[0005] A low-profile circularly polarized frequency-reconfigurable omnidirectional antenna includes an arc-shaped spiral arm, a phase compensation line, a main radiating patch, a varactor diode, an inductor, a capacitor, a radiating via, a DC via, a ground plane, and a dielectric substrate.

[0006] The arc-shaped spiral arm, phase compensation line, and main radiating patch are all disposed on the upper surface of the dielectric substrate, and the ground plane is disposed on the lower surface of the dielectric substrate; the radiating via penetrates the dielectric substrate and is used to connect the upper main radiating patch and the ground plane on the lower surface; the DC via also penetrates the dielectric substrate and the ground plane and is used to provide an access point for the bias circuit to apply a DC bias voltage to the varactor diode 4.

[0007] In terms of manufacturing process, the metal surfaces of the front (upper surface) and back (lower surface) of the dielectric substrate are processed and etched using printed circuit board manufacturing technology to form the required metal patterns for the arc-shaped spiral arm, phase compensation line, main radiating patch and ground plane; the antenna is fed by a standard coaxial probe in a back-feed manner.

[0008] The anode of the varactor diode 4 is soldered to the main radiating patch, and the cathode is soldered to the rectangular "island" in the center of the trench. The model of the varactor diode 4 is MA46H120 from MACOM Technology Solutions. A DC bias voltage is applied to the varactor diode 4 through the DC via. When the bias voltage changes within the range of 0V to 18V, the internal capacitance value of the varactor diode 4 changes from 1.30pF to 0.15pF, thereby realizing the reconstruction of the antenna operating frequency.

[0009] The inductor is a 47nH inductor, which is soldered between the DC via and the varactor diode 4. Its function is to isolate the radio frequency signal and prevent the radio frequency signal from interfering with the DC bias circuit.

[0010] The capacitor is a 10pF capacitor, which is soldered between the DC via and the outer edge of the main radiating patch. Its function is to isolate DC signals and provide a path for the propagation of radio frequency signals between the vias and slots.

[0011] The thickness of the dielectric substrate is sufficiently small compared to the antenna operating wavelength, such that only a longitudinal electric field exists in the grooves around the dielectric substrate, which can be equivalent to a magnetic current source M; the width of the arc-shaped spiral arm is also sufficiently small compared to the antenna operating wavelength, such that the arc-shaped spiral arm can be equivalent to a current source J.

[0012] A double-sided parallel meandering microstrip line is arranged between the main radiating patch and the arc-shaped spiral arm. This parallel meandering microstrip line is the phase compensation line, which can act as a phase compensation structure between the magnetic current source M and the current source J, providing the required 90° phase difference for circularly polarized radiation. The magnetic current source M radiates the vertically polarized electric field Eθ in the far field region, and the current source J radiates the horizontally polarized electric field Eφ in the far field region. There is a 90° phase difference between the vertically polarized electric field Eθ and the horizontally polarized electric field Eφ. According to the principle of electromagnetic field superposition, omnidirectional radiation of circularly polarized waves can be realized.

[0013] The dielectric substrate is Rogers 5880, with a relative permittivity of 2.2, a loss tangent of 0.0009, and a thickness hs of 1.575 mm.

[0014] Based on the top and bottom views of the antenna, the dimensions and parameters of the antenna are as follows: slot width ws is 1mm, internal line width wi is 2.1mm, phase compensation line length lm is 4.33mm, radiating via diameter db is 0.8mm, main radiating patch width wm is 7mm, feed hole diameter df is 0.92mm, DC via diameter dv is 1mm, gap gp is 0.3mm, microstrip line width wp is 0.3mm, arc-shaped spiral arm width wa is 0.8mm, edge gap ge is 0.5mm, slot radius rs is 13.9mm, main radiating patch radius rp is 11mm, arc-shaped spiral arm radius ra is 5mm, overall antenna side length d is 36mm, slot angle αs is 60°, gap angle αg is 6°, and main radiating patch angle αp is 8°. The overall dimensions of the antenna are 36mm × 36mm × 1.575mm, achieving a low profile design.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] 1. Significant low profile characteristics: The overall size of the antenna of this invention is 36mm×36mm×1.575mm, and the thickness of the dielectric substrate is only 1.575mm, which is small enough compared to the operating wavelength. The overall profile height is extremely low, which can well meet the needs of miniaturization and integration of electronic devices and facilitates integration and installation with the equipment carrier.

[0017] 2. Flexible frequency reconfiguration: By selecting the MA46H120 varactor diode and applying a DC bias voltage of 0V-18V through a DC via, the capacitance value of the varactor diode can be varied within the range of 1.30pF-0.15pF, thereby realizing flexible reconfiguration of the antenna's operating frequency. This can adapt to the usage requirements of different communication frequency bands and improve the antenna's versatility.

[0018] 3. Excellent omnidirectional circular polarization radiation performance: By setting a phase compensation line, a 90° phase difference is provided between the magnetic current source and the current source, so that the vertical polarization electric field Eθ radiated by the magnetic current source has a 90° phase difference with the horizontal polarization electric field Eφ radiated by the current source. Combined with the superposition principle, circular polarization wave radiation is realized. At the same time, the antenna structure design ensures omnidirectional radiation characteristics, strong anti-multipath interference capability, and wide communication coverage.

[0019] 4. Excellent signal isolation: By placing a 47nH inductor between the DC via and the varactor diode, the radio frequency signal is effectively isolated, avoiding interference from the radio frequency signal to the DC bias circuit; a 10pF capacitor is placed between the DC via and the outer edge of the main radiating patch to achieve DC signal isolation and provide a path for the propagation of radio frequency signals, ensuring the stability and reliability of the antenna operation.

[0020] 5. Mature manufacturing process: The printed circuit board manufacturing process is used to process and etch the metal surfaces on both sides of the dielectric substrate. The process is mature, the cost is low, and it is easy to mass-produce and apply in practice. Attached Figure Description

[0021] Figure 1 This is a three-dimensional schematic diagram of the overall antenna structure according to an embodiment of the present invention.

[0022] Figure 2 This is a top view of the antenna according to an embodiment of the present invention.

[0023] Figure 3 This is a bottom view of the antenna according to an embodiment of the present invention.

[0024] Figure 4 This is a partially enlarged schematic diagram of the phase compensation line structure in an embodiment of the present invention.

[0025] Figure 5 This is a simulation / test result diagram of the reflection coefficient (S11) under different bias voltages in an embodiment of the present invention.

[0026] Figure 6 This is a diagram showing the shaft ratio simulation / test results of an embodiment of the present invention under typical operating conditions.

[0027] Figure 7 This is a radiation pattern of an embodiment of the present invention under typical operating conditions.

[0028] 1. Arc-shaped spiral arm; 2. Phase compensation line; 3. Main radiating patch; 4. Varactor diode; 5. Inductor; 6. Capacitor; 7. Radial via; 8. DC via; 9. Ground plane; and 10. Dielectric substrate. Detailed Implementation

[0029] The present invention will now be further described with reference to the accompanying drawings.

[0030] I. Antenna Structure Fabrication

[0031] Dielectric substrate selection: A Rogers 5880 dielectric substrate 10 was selected, with a relative permittivity of 2.2, a loss tangent of 0.0009, and a thickness hs of 1.575 mm. The dielectric substrate 10 was cut into a 36 mm × 36 mm square structure to serve as the basic carrier of the antenna.

[0032] Metal Pattern Etching: Using printed circuit board manufacturing processes, a metal pattern consisting of an arc-shaped spiral arm 1, a phase compensation line 2, and a main radiating patch 3 is etched on the upper surface metal layer of the dielectric substrate 10, and a metal pattern of the ground plane 9 is etched on the lower surface metal layer. The arc-shaped spiral arm 1 has a width wa controlled to 0.8 mm, a radius ra of 5 mm, and an angle that matches the overall structural design. The main radiating patch 3 has a width wm of 7 mm, a radius rp of 11 mm, and an angle αp of 8°. The phase compensation line 2 adopts a double-sided parallel meandering microstrip line structure, with a length lm machined to 4.33 mm to ensure a 90° phase difference. The slot width ws is 1 mm, the radius rs is 13.9 mm, the angle αs is 60°, the internal line width wi is 2.1 mm, the gap gp is 0.3 mm, the edge gap ge is 0.5 mm, and the microstrip line width wp is 0.3 mm. Etching is performed strictly according to the above dimensional parameters to ensure the accuracy of the metal pattern.

[0033] Via fabrication: Radial vias 7 and DC vias 8 are fabricated at corresponding positions on the dielectric substrate 10. The diameter db of the radial via 7 is 0.8 mm. After penetrating the dielectric substrate 10, it is reliably connected to the upper main radiating patch 3 and the lower ground plane 9 through metallization. The diameter dv of the DC via 8 is 0.92 mm. It also penetrates the dielectric substrate 10 and the ground plane 9 and serves as the access point for the bias circuit.

[0034] Component soldering: Solder the MA46H120 varactor diode 4 from MACOM Technology Solutions in the designated position, with its anode soldered to the main radiating patch 3 and its cathode soldered to the rectangular "island" in the center of the slot; solder the 47nH inductor 5 between the DC via 8 and the varactor diode 4; solder the 10pF capacitor 6 between the DC via 8 and the outer edge of the main radiating patch 3. During the soldering process, ensure that the solder joints are firm and free of cold solder joints to guarantee the normal operation of the components.

[0035] Feed structure setup: A standard coaxial probe is used to feed the antenna in a back-feed manner. The inner conductor of the coaxial probe is connected to the main radiating patch 3, and the outer conductor is connected to the ground plane 9 to ensure stable transmission of the feed signal.

[0036] Antenna performance testing and adjustment

[0037] Frequency reconfigurability performance test: DC bias voltages ranging from 0V to 18V were applied to varactor diode 4 through DC via 8. The S-parameters of the antenna under different bias voltages were measured using a vector network analyzer, and the changes in the antenna's operating frequency were recorded. Test results show that when the bias voltage increases from 0V to 18V, the capacitance of varactor diode 4 decreases from 1.30pF to 0.15pF, and the antenna's operating frequency is correspondingly reconfigured, meeting the requirements of multi-band communication.

[0038] Circular polarization radiation performance test: In a microwave anechoic chamber, the far-field radiation performance of the antenna was tested, measuring the amplitude and phase relationship of the vertical polarization electric field Eθ and the horizontal polarization electric field Eφ in the far-field region. The test results show that the amplitudes of the vertical polarization electric field Eθ and the horizontal polarization electric field Eφ are similar, and the phase difference remains stable at around 90°, which meets the requirements of circular polarization radiation, and the circular polarization axial ratio is excellent.

[0039] Omnidirectional radiation performance test: By rotating the antenna or test probe, the radiation gain of the antenna at different azimuth angles was measured. The results showed that the radiation gain of the antenna changed little within the 360° azimuth angle range, and it has good omnidirectional radiation characteristics, which can effectively transmit and receive signals in all directions.

[0040] Low profile characteristic verification: The overall height of the antenna, i.e. the thickness of the dielectric substrate 10, is 1.575mm. Combined with the antenna's planar dimensions of 36mm×36mm, the low profile characteristic of the antenna is confirmed, which can meet the installation requirements of miniaturized devices.

[0041] Signal isolation performance test: During antenna operation, the RF signal interference in the DC bias circuit and the DC signal isolation of the RF signal propagation path were monitored. The results showed that inductor 5 and capacitor 6 played a good role in signal isolation. The DC bias circuit was not affected by RF signal interference, and the RF signal could propagate stably between the holes and slots. The antenna had high operational stability.

[0042] Example Effects

[0043] The low-profile circularly polarized frequency-reconfigurable omnidirectional antenna prepared in this embodiment has an overall size of 36mm×36mm×1.575mm and a low profile height. It can achieve flexible reconfiguration of the operating frequency through 0V-18V bias voltage control. It has excellent circular polarization axial ratio, good omnidirectional radiation characteristics, good signal isolation effect, and stable and reliable operation, which can meet the application requirements of wireless communication, satellite navigation, Internet of Things and other fields.

Claims

1. A low-profile, circularly polarized, frequency-reconfigurable omnidirectional antenna, characterized in that, The antenna includes an arc-shaped spiral arm (1), a phase compensation line (2), a main radiating patch (3), a varactor diode (4), an inductor (5), a capacitor (6), a radiating via (7), a DC via (8), a ground plane (9), and a dielectric substrate (10). The arc-shaped spiral arm (1), the phase compensation line (2), and the main radiating patch (3) are all disposed on the upper surface of the dielectric substrate (10), and the ground plane (9) is disposed on the lower surface of the dielectric substrate (10). The radiating via (7) penetrates the dielectric substrate (10) and connects the main radiating patch (3) and the ground plane (9). The DC via (8) penetrates the dielectric substrate (10) and the ground plane (9) and serves as a bias circuit access point. A metal pattern is etched using a printed circuit board manufacturing process, and the antenna is fed using a standard coaxial probe back-feed method.

2. The low-profile circularly polarized frequency-reconfigurable omnidirectional antenna according to claim 1, characterized in that, The varactor diode (4) is a MA46H120 from MACOM Technology Solutions. The anode is welded to the main radiating patch (3), and the cathode is welded to the rectangular "island" in the center of the trench. A DC bias voltage of 0V-18V is applied to the varactor diode (4) through a DC via (8), and its capacitance value varies from 1.30pF to 0.15pF.

3. The low-profile circularly polarized frequency-reconfigurable omnidirectional antenna according to claim 1, characterized in that, The inductor (5) has an inductance of 47nH and is soldered between the DC via (8) and the varactor diode (4) to isolate radio frequency signals; the capacitor (6) has a capacitance of 10pF and is soldered between the DC via (8) and the outer edge of the main radiating patch (3) to isolate DC signals and provide a path for radio frequency signals.

4. A low-profile circularly polarized frequency-reconfigurable omnidirectional antenna according to claim 1, characterized in that, The dielectric substrate (10) is of model Rogers 5880, with a relative permittivity of 2.2, a loss tangent of 0.0009, and a thickness hs of 1.575 mm. The longitudinal electric field in the groove around the dielectric substrate (10) is equivalent to a magnetic current source M, and the arc-shaped spiral arm (1) is equivalent to a current source J.

5. A low-profile circularly polarized frequency-reconfigurable omnidirectional antenna according to claim 1, characterized in that, The phase compensation line (2) is a double-sided parallel meandering microstrip line, which is set between the main radiating patch (3) and the arc-shaped spiral arm (1) to provide the 90° phase difference required for circular polarization radiation; the magnetic current source M radiates the vertically polarized electric field Eθ, and the current source J radiates the horizontally polarized electric field Eφ. The two have a 90° phase difference to realize circular polarization wave radiation.

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