CN105514612A - Low-profile dual-band omni-directional antenna - Google Patents

Abstract

The invention discloses a low profile dual frequency band omnidirectional antenna. Low-profile dual-band omnidirectional antennas suitable for wireless communication systems, including dielectric substrates, radiating metal patches, resonant metal patches, metal bottom plates and metal vias. The resonant metal patch is placed around the radiating metal patch and kept at a certain distance. Metal vias connect the resonant metal patch to the metal floor. The antenna of the invention can maintain the radiation performance similar to that of a monopole antenna in two operating frequency bands, and has a section height of only 0.02 wavelength. The antenna of the invention has the advantages of wide working frequency band, low cross section, simple structure, stable performance, mass production and the like.

Description

Low-profile dual-band omnidirectional antenna

technical field

The invention relates to a microstrip antenna, especially a dual-band omnidirectional antenna with low profile characteristics, which is widely used in mobile communication, satellite communication, radar and other wireless communication systems, and is especially suitable for multi-band work, 360 ° direction signal Coverage, and applications with strict requirements on the antenna profile.

Background technique

At present, antennas with omnidirectional radiation have been widely used in wireless communication systems. In the indoor distribution system of mobile communication, monopole antennas are widely used for coverage. This is because monopole antennas have the characteristics of omnidirectional radiation in the horizontal plane and tapered coverage in the vertical plane, which is very conducive to signal coverage. However, monopole antenna structures are constructed using vertical quarter-wavelength conductors mounted perpendicular to the ground or conductive plane. Therefore, when this antenna is used in the short-wave frequency band, its profile is too high and is easily exposed; even in mobile communication systems, because the mobile station requires a compact and ultra-thin design, this antenna cannot meet the design requirements.

Mobile communication has entered a period of rapid development. From the well-known mobile communication field, there are 2G (GSM, CDMA, PCS) communication systems, 3G (TD-SCDMA, WCDMA, CDMA2000) communication systems and 4G (TD-LTE) communication systems, etc. ; In terms of wireless coverage, there are wireless communication systems of different standards such as WLAN, Bluetooth, wireless charging, and WiFi. Because different communication standards are assigned different communication frequency bands, this results in a huge waste of antenna site resources. Different communication systems need to have their own antennas in order to provide customers with high-quality services and information exchange. In order to save antenna site resources, the idea of co-site was proposed and advocated by the national communication authority. As the front-end antenna for wireless communication, multi-band or broadband antennas can be used to replace the original single-band antenna to achieve the integration of network technology, thereby solving the scarcity of site resources and effectively improving the quality of the communication network. effective method.

An additional resonance unit is added on the basis of the original antenna, so that the antenna can work in multiple frequency bands and realize the integration of multiple networks. This increases the size of the original antenna to a certain extent, and complicates the overall structure of the antenna, which is not conducive to controlling the height of the overall profile of the antenna, resulting in problems such as limited application scenarios of this antenna. The low-profile directional antenna implemented in the form of microstrip generally has a narrow operating frequency, which cannot meet the needs of practical applications. Moreover, for this type of antenna, due to the reason of the back reflector, the traditional design method cannot achieve 360° uniform signal coverage, and can only achieve directional radiation.

Contents of the invention

In order to overcome the high profile of the traditional monopole antenna and achieve the purpose of working in multiple frequency bands, the present invention provides a low-profile dual-band omnidirectional antenna with simple structure and simple feeding.

The technical solution adopted by the present invention to solve the technical problem is: the low-profile dual-band omnidirectional antenna includes a dielectric substrate, a metal base plate printed on one side of the dielectric substrate, and a metal bottom plate printed on the other side of the dielectric substrate. A radiating metal patch and at least three mushroom-shaped resonant unit structures surrounding it; each mushroom-shaped unit structure is composed of a resonant metal patch and at least one metal via, wherein the mushroom-shaped is a fan-shaped ring; the The metal via connects the metal bottom plate and the resonant metal patch through the dielectric substrate; the inner core and outer wall of the coaxial cable or RF coaxial connector are respectively connected to the radiating metal patch and the metal bottom plate, as the feed-in interface of the antenna electromagnetic wave signal .

For the low-profile dual-band omnidirectional antenna, the outer contour shape of the radiating metal patch can be circular or square, or any shape.

In the low-profile dual-band omnidirectional antenna, the mushroom-shaped unit structure includes a resonant metal patch and metal vias; and there is a gap between the mushroom-shaped unit structure and the radiating metal patch.

In the low-profile dual-band omnidirectional antenna, there are gaps between the mushroom-shaped unit structures to separate them.

The position of the metal vias in the mushroom-shaped unit structure can be adjusted according to the required resonance frequency, and at the same time, multiple metal vias can also be used to achieve this. As an optimized solution of the present invention, the metal via hole is located at the center of the resonant metal patch.

As another optimization solution of the present invention, the shape of the radiating metal patch is circular, and its feeding point is located at the center of the circle.

Changing the dielectric constant and substrate thickness of the dielectric substrate, the shape and size of the radiating metal patch, the size of the resonant metal patch and the position of the metal via can control the resonant frequency generated by the subwavelength resonance and form the work in TM02 mode Electromagnetic waves, so as to adjust the two working frequency bands.

The radiation metal patch of the present invention adopts a circular patch to excite the TM02 mode, and the field does not change in the φ direction. The combination of the circular patch antenna and the mushroom-shaped unit structure can produce zero-order resonance characteristics. The single-sector model and equivalent circuit are analyzed, and the interface between the two sectors is equivalent to an ideal magnetic wall. Therefore, the inductance in series and the capacitance in parallel are mainly determined by the right-hand component of the patch; the capacitance in series and the inductance in parallel are respectively introduced by the gap between the patches and the short-circuit via hole. It can be known from the theory of composite left and right-handed transmission lines that this equivalent circuit can support a wave with a zero propagation constant at a certain frequency, that is, the zero-order resonance of the model.

The low-profile dual-band omnidirectional antenna described in the present invention has three resonance points. The first resonance point is the zero-order resonance of the antenna after introducing the mushroom structure, which forms the first working frequency band. In the zero-order resonant mode, the electric field is uniform perpendicular to the patch, which is equivalent to a magnetic current loop along a circular boundary. So it can produce an omnidirectional radiation pattern in the horizontal plane. The resonance modes of the second and third resonance points are both TM02 modes, which are generated by the circular patch and the ring formed by the mushroom structure respectively. The two are coupled with each other to form a second working frequency band.

The beneficial effect of the present invention is that the overall section height of the antenna is 0.02λ, which is far lower than the conventional 0.25λ. At the same time, the antenna can work in two frequency bands, and both have a radiation pattern similar to a monopole antenna, that is, the vertical pattern has a deep null, while the horizontal pattern maintains the characteristics of omnidirectional radiation.

Description of drawings

Fig. 1 is a schematic diagram of the overall structure of the low-profile dual-band omnidirectional antenna of the present invention.

Fig. 2 is a schematic diagram of the patch layer structure of the low-profile dual-band omnidirectional antenna of the present invention.

Fig. 3 is a side view of the low-profile dual-band omnidirectional antenna of the present invention.

FIG. 4 is a schematic structural diagram of a single sector in FIG. 1 .

FIG. 5 is an equivalent circuit diagram of the structure in FIG. 4 .

Fig. 6 is a diagram of scattering parameters of the low-profile dual-band omnidirectional antenna of the present invention.

Fig. 7 is the E-plane radiation pattern of the low-profile dual-band omnidirectional antenna of the present invention.

Fig. 8 is the H-plane radiation pattern of the low-profile dual-band omnidirectional antenna of the present invention.

Fig. 9 is a gain diagram of the low-profile dual-band omnidirectional antenna of the present invention.

detailed description

In order to make the object, technical solution and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with the examples. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

The low-profile dual-band omnidirectional antenna of the present invention is composed of a dielectric substrate (1), a metal base plate (2), a radiation metal patch (3), a resonant metal patch (5) and a metal via hole (6) .

The radiation metal patch (3) and the resonant metal patch (5) are located on the same side of the dielectric substrate (1), and they and the metal base (2) are printed on both sides of the dielectric substrate (1) respectively.

As an optimized solution of the embodiment of the present invention, the feeding position of the antenna is located at the center of the radiation metal patch, and the inner core (7) of the coaxial cable (8) or the joint passes through the via hole (4) and the radiation metal patch ( 3) are connected, and the coaxial cable (8) or the outer wall of the joint is connected with the metal base plate (2). The signal can then be fed externally to the radiating metal patch (3) of the antenna.

Fig. 2 is a schematic diagram of the patch layer structure of the embodiment of the present invention. In this embodiment, the radiating metal patch (3) is circular. In other different occasions, its outline can be triangular, quadrangular or polygonal. Meanwhile, the inside of the radiating metal patch (3) can be slotted.

The shape of the resonant metal patch (5) can be changed accordingly with the shape of the radiating metal patch (3). The resonant metal patch (5) is arranged around the radiating metal patch (3), and keeps a certain distance from the radiating metal patch (3), without direct contact. There are certain gaps between the resonant metal patches (5).

The metal via hole (6) passes through the dielectric substrate (1), and the two ends are respectively connected to the metal base plate (2) and the resonant metal patch (5). As a further optimization solution of the embodiment of the present invention, the metal via (6) is located at the center of the resonant metal patch (5).

FIG. 4 is a schematic structural diagram of a single sector in FIG. 1 . In the case of zero-order resonance, the radiating metal patch (31) can be equivalent to a series inductor and a parallel capacitor. The gap between the radiating metal patch (31) and the resonant metal patch (51) can be equivalent to a series capacitor, and the metal via (61) can be equivalent to a parallel inductor. The single-sector metal bottom plate (21) is an electric wall, and the medium boundary one (71) and medium boundary two (72) of the single sector can be equivalent to an ideal magnetic wall, and the electromagnetic wave in the sector is fed by the feed port (41) enter. Figure 5 shows the equivalent circuit diagram of a single-sector structure, where _LR and _CR are respectively equivalent to the case of zero-order resonance, and the radiation metal patch (31) is equivalent to a series inductor and a parallel capacitor; C _L is equivalent to a gap between the radiating metal patch (31) and the resonant metal patch (51), which is equivalent to a series capacitor, and _RL is equivalent to a metal via (61) equivalent to a parallel inductance.

For the low-profile dual-band omnidirectional antenna of the present invention, the dielectric substrate can adopt various insulating media, and can also be an air dielectric. The thickness of the dielectric substrate can be adjusted as required, generally between 0.3 mm and 5 mm.

As an optimized solution of the present invention, the characteristic impedance of 50Ω is used for feeding at the feeding port.

As a specific embodiment of the present invention, the size of the dielectric substrate (1) is Φ84mm×1.5mm, and the size of the radiation metal patch is Φ41mm. The distance between the resonant metal patch and the radiating metal patch is generally in the range of 0.1 mm to 3 mm; and the distance between adjacent resonant metal patches is generally in the range of 0.1 mm to 4 mm.

Fig. 6 is a diagram of scattering parameters of a specific embodiment of the present invention. The abscissa is the frequency (GHz), and the ordinate is the decibel value (dB). The antenna can have S11<-10dB in the 3.995-4.025GHz and 4.94-6.06GHz frequency bands, so that the antenna can work in dual frequency bands.

Fig. 7 is the E-plane radiation pattern at three resonance frequency points of 4.01 GHz, 5.24 GHz and 5.94 GHz according to a specific embodiment of the present invention. The E-plane radiation pattern at each frequency point has a conical shape with a >20dB null at the broadside.

Fig. 8 is an H-plane radiation pattern at three resonance frequency points of 4.01 GHz, 5.24 GHz and 5.94 GHz according to a specific embodiment of the present invention. The H-surface radiation pattern at each frequency point is circular, that is, omnidirectional radiation on the horizontal plane.

Fig. 9 is a gain graph of a specific embodiment of the present invention. The gain of the antenna in the first working frequency band is about 5.1dBi, and the gain of the antenna in the second working frequency band varies from 5.8dBi to 8dBi.

As a specific embodiment of the present invention, the antenna can work in the zero-order resonance mode and TM02 mode. Their relative operating bandwidths are 0.75% and 20%, respectively.

As a specific embodiment of the present invention, the antenna can generate an equivalent circular magnetic current, thereby greatly reducing the overall section height of the antenna. The overall profile height of this antenna is 0.02λ, much lower than the conventional 0.25λ.

The low-profile dual-band omnidirectional antenna of the present invention can be used in the transmission of multi-wireless communication system signals, can be applied to indoor coverage of mobile communication systems, can also be integrated with other equipment, and can also be applied to other similar occasions. The antenna of the invention has a simple structure, is easy to process, has stable performance, and is beneficial to mass production.

The above-mentioned low-profile dual-band omnidirectional antenna is only given as a preferred example, and is not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, All should be included within the protection scope of the present invention.

Claims (10)

1. Low-profile dual-band omnidirectional antenna, characterized in that it includes a dielectric substrate, a metal base plate printed on one side of the dielectric substrate, a radiating metal patch printed on the other side of the dielectric substrate and at least around the radiating metal patch Three mushroom-shaped resonant unit structures; each mushroom-shaped unit structure is mainly composed of a resonant metal patch and at least one metal via; the metal via connects the metal base plate and the resonant metal patch through the dielectric substrate; The radiating metal patch is connected to the feeder core wire, and the metal bottom plate is connected to the outer wall of the feeder. 2. The low-profile dual-band omnidirectional antenna according to claim 1, characterized in that: the outer contour of the radiating metal patch can be circular, triangular, quadrangular or polygonal. 3. The low-profile dual-band omnidirectional antenna according to claim 2, characterized in that: the shape of the radiating metal patch is circular, and its feeding point is located at the center of the circle. 4. The low-profile dual-band omnidirectional antenna as claimed in claim 1, characterized in that: the resonant metal patch is placed around the radiating metal patch, and keeps a certain distance from the radiating metal patch; Keep a certain distance between adjacent resonant metal patches. 5. The low-profile dual-band omnidirectional antenna according to claim 1, characterized in that: said dielectric substrate is a conventional insulating medium or a medium such as air. 6. The low-profile dual-band omnidirectional antenna according to claim 1, characterized in that: said feed core wire is a metal coaxial cable or a coaxial connector. 7. The low-profile dual-band omnidirectional antenna according to claim 6, wherein the characteristic impedance of the feed cable or the coaxial connector is 50Ω. 8. The low-profile dual-band omnidirectional antenna according to claim 1, characterized in that: the overall profile height of the antenna is 0.02λ. 9. low-profile dual-band omnidirectional antenna as claimed in claim 3, is characterized in that: the radiating metal patch adopts the circular patch to excite the TM02 mode, and the field does not change in the φ direction; the circular patch The combination of the antenna and the mushroom-shaped resonant unit structure produces zero-order resonant characteristics. 10. The low-profile dual-band omnidirectional antenna as claimed in claim 7, characterized in that: the low-profile dual-band omnidirectional antenna has three resonance points, two operating frequency bands: The first resonance point is the zero-order resonance of the antenna after introducing the mushroom-shaped resonant unit structure, forming the first working frequency band. Because in the zero-order resonance mode, the electric field is uniformly perpendicular to the patch, which is equivalent to that along the circular boundary. Magnetic current ring, so an omnidirectional radiation pattern is generated on the horizontal plane; The resonant modes of the second and third resonant points are both TM02 modes, which are respectively composed of radiating metal patches and mushroom-shaped resonant unit structures. The two are coupled to each other to form the second working frequency band; Deep nulling, while the horizontal plane pattern maintains the omnidirectional radiation characteristics.