A patch antenna with a monopole ring array on the periphery

Abstract

The present invention discloses a patch antenna with a monopole circular array on the periphery, belonging to the field of antenna technology; including a substrate, a metal ground, a monopole and a metal patch; the metal ground and the metal patch are respectively located on the upper surface and the lower surface of the substrate; the substrate and the metal ground are both circular, wherein the diameter of the metal ground is greater than the diameter of the substrate; the substrate covers the middle area of ​​the upper surface of the metal ground; a plurality of monopoles are arranged in the peripheral area of ​​the upper surface of the metal floor, and a plurality of monopoles are arrayed along the central circumference of the dielectric substrate; the metal patch is polygonal and is located in the central area of ​​the upper surface of the substrate; the longest straight line segment inside the metal patch is smaller than the radius of the substrate; a plurality of gaps are arranged in the peripheral area of ​​the substrate, and the plurality of gaps are rotationally symmetrical along the central axis of the substrate. The present invention greatly improves the bandwidth.

Description

Technical Field

[0001] The present invention relates to the field of antenna technology, and in particular to a patch antenna with a monopole circular array on the periphery. Background Art

[0002] Patch antennas are often used for high-performance GNSS multi-band antennas due to their planar structure, which is easy to integrate with circuit boards. Patch antennas have disadvantages such as narrow bandwidth. Since patch antennas operate based on the principle of planar resonators, they usually perform best at a specific frequency. Although several techniques have been used to increase the available bandwidth of patch antennas, it is still difficult to achieve the required bandwidth. This is especially true when the substrate material and the given physical dimensions are limited. Therefore, the patch antenna needs to be of a certain size (usually half the waveguide wavelength) to resonate at the operating frequency, and the resulting radiation pattern is usually determined using the given materials and technology. Summary of the invention

[0003] The present invention overcomes the disadvantages of the prior art and greatly improves the bandwidth by proposing a patch antenna with a peripheral parasitic monopole circular array.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is:

[0005] A patch antenna with a monopole circular array on the periphery, comprising a substrate, a metal ground, a monopole and a metal patch; the metal ground and the metal patch are respectively located on the upper surface and the lower surface of the substrate; the substrate and the metal ground are both circular, wherein the diameter of the metal ground is greater than the diameter of the substrate;

[0006] The substrate is covered on the middle area of ​​the upper surface of the metal floor; the plurality of monopoles are arranged in the peripheral area of ​​the upper surface of the metal floor, and the plurality of monopoles are arrayed along the central circumference of the dielectric substrate;

[0007] The metal patch is polygonal and located in the central area of ​​the upper surface of the substrate; the longest straight line segment inside the metal patch is smaller than the radius of the substrate; a plurality of gaps are arranged in the peripheral area of ​​the substrate, and the plurality of gaps are rotationally symmetrical along the central axis of the substrate.

[0008] The monopole is perpendicular to the metal ground.

[0009] Furthermore, it also includes one or more phase delay lines connected to corresponding one or more monopoles.

[0010] Further, one or more monopoles are vertical conductors.

[0011] Compared with the prior art, the present invention has the following advantages:

[0012] First, the antenna made according to the principles of the present invention has greatly improved bandwidth due to the coupling of multiple surrounding monopoles. Second, the patch antenna of the present invention provides reduced cross polarization due to the control of surface wave currents. In addition, the surrounding radiator in the shape of a spiral hot wheel using multiple feeds and sequential rotation excitation improves circular polarization. Third, the antenna proposed by the present invention can provide beamforming capabilities, in which the position, shape and refractive index coefficient of the surrounding radiator can be changed to change the radiation pattern. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a top view of an embodiment of the present invention (without monopole);

[0014] Figure 2 It is an axonometric diagram of an embodiment of the present invention.

[0015] In the figure: 1. Metal ground, 2. Gap, 3. Metal patch, 4. Substrate, 5. Monopole. DETAILED DESCRIPTION

[0016] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0017] The present invention provides a microstrip patch antenna with wider bandwidth, better wide angle axis ratio and controllable radiation pattern; a patch antenna with a fixed center is surrounded by surrounding reactive or resistive load monopoles as parasitic radiators excited by surface waves. The surrounding monopoles can be printed on the same substrate as the patch and can be in a spiral or pinwheel shape, thereby achieving the purpose of reducing multipath signals at the antenna end.

[0018] The antenna consists of three elements. The first element includes a patch antenna (metal patch). The patch antenna can be a single layer or a stacked layer patch antenna. The second element includes a set of reactively loaded monopoles or resistively loaded monopoles rotationally symmetrically around the patch antenna. The monopoles can terminate certain phase delay lines. The third element includes a metal ground.

[0019] Reference Figure 1 and Figure 2 The antenna is composed of a metal ground and one or more patch antenna stacks thereon. One or more feed points are operatively connected to the patch antenna. A plurality of monopoles are arranged around the patch antenna. In some designs, the monopoles may terminate in phase delay lines.

[0020] As can be seen, one or more patch antennas can be arranged in a stacked manner. The patch antenna radiates equivalently at the resonant slot ring formed between the metal patch and the metal ground. Since the dielectric substrate of the antenna usually has truncated edges, it does not support the propagation of bounded surface waves at the dielectric / metal interface. However, the fringe fields at the edge of the patch do radiate TM surface waves that propagate along the air-metal (metal ground) surface. This surface wave is also called surface plasmon in optics, and at microwave frequencies, it extends a long distance into the surrounding space with an extremely low attenuation coefficient. The H field of this wave is perpendicular to the propagation direction, where the corresponding longitudinal surface current flows on the metal conductor; while the electric field is associated with the oscillating charges distributed on the top of the metal (at the frequency of the radiated wave), forming a loop that jumps vertically in and out of the surface in the longitudinal direction. It propagates at a speed close to the free space speed of light. Therefore, it is usually described as a surface current rather than a surface wave in microwaves. In fact, they are not much different from normal alternating currents on any conductor. The surface wave propagates from the formed patch slot ring to the edge of the truncated ground plane and is then diffracted, where it reradiates into space as if the metal edge were a point source. These radiations affect the antenna in the far field, upper hemisphere, lower hemisphere, and horizontal plane in all directions. For applications, these undesirable radiations usually increase the reception of noise signals from multipath or nearby interference. Several techniques have been developed to suppress or reduce the propagation of transverse magnetic field (TM) surface currents, such as choke rings and resistive stealth ground planes. The surface impedance of the wave on a flat metal sheet can be derived as

[0021]

[0022] Where σ is the metal conductivity and δ is the skin depth. According to this equation, the surface of a conductor generally exhibits low surface impedance.

[0023]

[0024] The interaction between the surface wave excited by the patch antenna and the antenna is illustrated by an example. S Surface impedance; E Z z-direction electric field; H X x-direction magnetic field; the surface wave generated by the patch antenna propagates to the surrounding monopoles before reaching the edge of the ground, where it is scattered and reflected. This depends on the load impedance of the RLC energy storage (Z = R / L / C = R + jX, which is a combination of R, L and C, R resistance, L inductance and C capacitance). The design can control its matching to the input impedance of the port monopole. Part of the surface wave signal induced in the parasitic monopole is first guided by the phase delay line, then reflected (scattered) and radiated again.

[0025] The reflection coefficient at the monopole is

[0026]

[0027] Where Zo is the characteristic impedance of the delay line (Z L Inductive impedance, X L Inductive admittance, R L Inductive resistance). If the load is resistive (only R in the load resonant cavity, X = 0), part of the surface wave power will be attenuated: (Γ is the reflection coefficient)

[0028]

[0029] In the short-circuit case (Z=0), total reflection occurs at the monopole port and the power captured by the monopole is fully radiated again:

[0030]

[0031] If the load is lossless (R=0) and reactive, the reflection coefficient is:

[0032]

[0033] is the normalized reactance of the terminal load to Z0 ( is the normalized admittance). From this equation we know that the phase signal of the reflected light can be controlled by changing the reactance value to control the delay line length:

[0034]

[0035] The above equations reveal two things. First, the phase of the reradiated signal from each monopole can be changed by adjusting the reactive load. Second, when the load reactance is small, the phase change is more significant than when the reactance is large. If the load is lossless (R = 0) and reactive, the reflection coefficient is:

[0036]

[0037] in,

[0038]

[0039] is the normalized reactance of the terminal load to Zo. From this equation we know that the phase of the reflected signal is controllable by changing the reactance value and the length of the delay line. The above equation reveals two key points. First, the phase of the re-radiated signal of each monopole can be changed by adjusting the reactance load. Second, when the loaded reactance is small, the change in phase is more obvious than when the reactance is large. The amount of re-radiated power also depends on the structure of the monopole, for example, the height and shape of the monopole determine how much power is induced, as well as the radiation efficiency. Typically, parasitic elements are close to resonance to more efficiently re-radiate surface waves, that is, when the total length of the monopole is close to a few times one-quarter of the waveguide length, the system efficiency is highest.

[0040] Assuming the excitation current of the center patch is Io, the corresponding radiation far field is And the N outer monopoles are equidistantly distributed along the ring. According to the circular array theory, the total radiated electric field is written as the superposition of the contribution fields of all radiators.

[0041]

[0042] where k is the free space wave number, k is the surface wave number (ks = k), d is the distance from the central patch to the surrounding monopole ring (radius of the ring), T is the reflection coefficient at the parasitic monopole n, and E Dipole Represents the radiation field of a single monopole element [1]. By changing the distance and reflection coefficient (amplitude and phase) between the patch antenna and the surrounding monopoles, a specific type of radiation pattern can be synthesized. Based on this principle, a single-fed reactive beam steering or nulling antenna can be realized. This concept can be explained by analogy with a reflectarray, where a group of reactive antenna elements are placed at the reflector position facing the source exciter to achieve a high-gain or beam-steerable antenna array. In this patent, the source is the surface wave generated by the antenna, and the reflector array is located in the same plane as the source. In other words, this monopole structure can also be interpreted as a high-impedance surface (impedance is much higher than the surface wave impedance), which scatters the surface wave into space.

[0043] Due to this process, the surrounding parasitic monopoles act as a load for the patch antenna, which reduces the quality factor (Q) of the patch resonator. This results in a substantial increase in the bandwidth of the antenna. In addition, this process causes changes in the near field and far field of the antenna, so the radiation pattern of the antenna can change. An example of such a change is that the roll-off may decrease or increase. This is sometimes desirable for an application. In addition, the axial ratio at low elevation angles can be improved because the intentionally added parasitic radiator manipulates the unwanted diffraction from the edge of the ground.

[0044] Figure 2is a patch antenna surrounded by a vertical line monopole. In alternative embodiments, the monopole may be connected to a phase delay line. Various monopole arrangements may be used according to alternative embodiments of the present invention. Therefore, the present invention should not be considered limited to the specific examples described herein.

[0045] Depending on the required radiation performance, the surrounding monopoles can take the shape of vertical lines, inverted L (or inverted F), and printed inverted L spirals. In addition, one, two, or more surrounding monopole arrays of different lengths can be combined to provide greater flexibility to form beams according to the total radiation given by the equation: more arrays can provide more operating frequencies; different clockwise directions of the spiral can control different polarizations; and the interaction between adjacent arrays can show more exotic electromagnetic bandgap effects, which helps multipath suppression.

[0046] The present invention utilizes a patch antenna system with increased bandwidth, improved radiation pattern, and reduced roll-off. By varying the loading circuit, the radiation pattern can be controlled to produce the optimum pattern for the application. The antenna only needs to be fed with multiple orthogonal feeds on the center patch antenna element. The design has many advantages including increased bandwidth, reduced cross polarization, changed radiation pattern, and reduced cost.

[0047] It should be noted that the use of a single row pinwheel spiral parasitic peripheral monopole antenna should be taken as an exemplary embodiment only. Using a resistive load or adding some specially designed monopole patterns, the front-to-back ratio is significantly increased. From the comparison, it can be concluded that the horizontal (0-90') right-hand circular polarization gain is improved by 2.2dB at the L1 (1575.4MHz) frequency and 2.6dB at the L2 (1227.6MHz) frequency.

[0048] It should be noted that the radiation pattern can be worked on by specific design depending on the system requirements, especially by using multiple arrays of parasitic elements and / or using different load circuits. The parasitic antenna element can be printed as a simple trace on the same layer as one or more patches. It is easily integrated with passive or active load circuits with tuning or switching capabilities.

[0049] The present invention is not limited to the above embodiments, but may include more other equivalent embodiments without departing from the concept of the present invention. The scope of the present invention is determined by the scope of the appended claims.

Claims

1. A patch antenna having a monopole ring array on the periphery, comprising a substrate, characterized in that: It also includes a metal ground, a monopole and a metal patch; the metal ground and the metal patch are respectively located on the upper surface and the lower surface of the substrate; the substrate and the metal ground are both circular, wherein the diameter of the metal ground is greater than the diameter of the substrate; The substrate is covered on the middle area of ​​the upper surface of the metal floor; the plurality of monopoles are arranged in the peripheral area of ​​the upper surface of the metal floor, and the plurality of monopoles are arrayed along the central circumference of the dielectric substrate; The metal patch is polygonal and located in the central area of ​​the upper surface of the substrate; the longest straight line segment inside the metal patch is smaller than the radius of the substrate; a plurality of gaps are arranged in the peripheral area of ​​the substrate, and the plurality of gaps are rotationally symmetrical along the central axis of the substrate.

2. A patch antenna having a monopole circular array on the periphery according to claim 1, characterized in that: The monopole is perpendicular to the metal ground.

3. A patch antenna with a monopole circular array on the periphery according to claim 1, characterized in that: It also includes one or more phase delay lines connected to corresponding one or more monopoles.

4. The patch antenna having a monopole circular array on the periphery according to claim 1, characterized in that: One or more monopoles are vertical conductors.

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