A CPW-fed high-isolation dual-stopband MIMO antenna

Abstract

The present invention relates to a CPW-fed high-isolation dual-stopband MIMO antenna, comprising a substrate, an antenna and a ground plane, characterized in that the antenna comprises two radiating units, each radiating unit contains a circular monopole UWB antenna, the two circular monopole UWB antennas are perpendicular to each other, and the circular monopole UWB antenna corrodes an SRR slot. Compared with the prior art, the coplanar waveguide feeding method of the present invention can reduce the dispersion effect and is simple to manufacture, with a compact structure, eliminating winding, vias and corresponding parasitic source inductance, reducing the radiation loss caused by surface waves, and increasing the antenna gain; it has high isolation and notch characteristics; it uses economical FR4 material, is small in size, and has a simple overall antenna structure and is easy to process.

Description

Technical Field

[0001] The invention relates to a wireless communication antenna, in particular to a CPW-fed high-isolation dual-stopband MIMO antenna. Background Art

[0002] In 2002, the Federal Communications Commission (FCC) of the United States approved the frequency band of 3.1 to 10.6 GHz as the working frequency band of ultra-wideband (UWB). Although it has many advantages such as rich spectrum resources, strong anti-interference performance, good transmission rate and confidentiality, there are two serious defects that limit its development. First, in order to avoid the signal interference of the ultra-wideband system with other systems that share part of the frequency band, its power is limited to a very low level; second, the ultra-wideband channel is a high-frequency selective fading channel. The channel generally includes hundreds of paths, and the maximum path delay reaches hundreds of nanoseconds. If the symbol time is too short, the inter-symbol interference will be very serious, which limits the further improvement of the data transmission rate of the ultra-wideband system. Combining ultra-wideband technology with MIMO technology, using spatial multipath, realizes the parallel transmission of multiple signals, and obtains obvious multiplexing gain and diversity gain, which effectively overcomes the shortcomings of ultra-wideband technology and is expected to achieve long-distance stable transmission.

[0003] The ultra-wideband frequency band includes other different narrowband wireless communication systems, such as Wi MAX (3.3~3.7GHz) and WLAN (5.15~5.35GHz) systems. In order to avoid interference between different systems, considering factors such as system cost and size, an effective method is to make the ultra-wideband antenna itself have the function of filtering out the corresponding interference frequency band, generating a larger reflection coefficient in the corresponding frequency band, forming the so-called "notch" function. In this regard, domestic and foreign scholars have carried out a lot of in-depth research. By loading parasitic patches of different shapes on the back of the dielectric plate, or embedding gaps of different shapes on the radiation patch or the floor, a stop band is generated for the required frequency band; in recent years, scholars have achieved the effect of generating stop bands for multiple frequency bands by embedding different gaps in the patch and the floor, or adding a combination of branches and gaps. Adding branches can effectively filter out the target frequency band, but the introduction of branches will inevitably increase the overall size of the antenna. Especially when introducing branches into MIMO antennas, it is easy to cause "secondary coupling" between antenna units, interfering with the independence of the MIMO antenna units. Embedding a certain length of gap on the floor of the MIMO antenna destroys the symmetry of the antenna structure, which can easily cause distortion of the high-frequency part of the antenna and affect its radiation performance. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a CPW-fed high-isolation two-stop-band MIMO antenna.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A CPW-fed high-isolation dual-stopband MIMO antenna comprises a substrate, an antenna and a ground plane, wherein the antenna comprises two radiating units, each radiating unit contains a circular monopole UWB antenna, the two circular monopole UWB antennas are perpendicular to each other, and an SRR groove is etched on the circular monopole UWB antenna.

[0007] The circular monopole UWB antenna comprises a circular patch and a 50Ω microstrip feeder. An SRR slot is etched on the circular patch. The SRR slot comprises an open rectangular slot and an arc-shaped slot. The openings of the rectangular slot and the arc-shaped slot are arranged back to back.

[0008] An isolation branch is arranged between the two circular monopole UWB antennas.

[0009] The antenna and the isolation branch are both axisymmetric structures, and the axis of symmetry is the axis of the isolation branch.

[0010] The isolation branch is in strip shape as a whole, and branches are arranged at both ends of the isolation branch.

[0011] The branches are V-shaped.

[0012] The grounding plate is an irregular hexagon formed by cutting off two diagonal corners of a square.

[0013] The substrate material is FR4.

[0014] The substrate has a dielectric constant of 4.4 and a thickness of 0.8 mm.

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

[0016] (1) The coplanar waveguide feeding method is different from other feeding methods such as side feeding and coaxial feeding. The coplanar waveguide feeding method can reduce the dispersion effect and is simple to manufacture. It has a compact structure and eliminates winding, vias and corresponding parasitic source inductance, reduces the radiation loss caused by surface waves, and increases the antenna gain. In addition, the size of the coplanar waveguide-fed antenna can be flexibly adjusted according to actual needs.

[0017] (2) The simulation results of the antenna isolation S21 / S12 are all lower than -22dB in the ultra-wideband range, and have high isolation characteristics. The reasons are as follows: 1. The antenna uses polarization diversity to place two linearly polarized antennas vertically, forming vertical polarization and horizontal polarization. In this way, electromagnetic waves of different polarizations are mismatched due to polarization, making the received signals more independent. 2. The CPW structure cuts off part of the coplanar ground, which has lower coupling. 3. The isolation branches can offset the induced current generated by the coupling at the excitation end on the non-excitation end. Combining the above three main reasons, the antenna achieves high isolation characteristics.

[0018] (3) The circular SRR slot and the rectangular SRR slot are used to generate notches covering different frequency bands. When the antenna is working, it is not affected by interference from Wi MAX (3.3~3.7GHz) and WLAN (5.15~5.3GHz) systems. That is, the S11 of the antenna is greater than -10dB in the range of 3.3~3.7GHz and 5.15~5.3GHz, and it cannot effectively receive and transmit signals. Except for the above frequency bands, the antenna has good ability to receive and transmit signals in the UWB range.

[0019] (4) The radiating unit of the antenna is designed based on the more common circular monopole UWB antenna. The antenna unit is placed vertically, and the branch structure and SRR slot structure are loaded. Finally, the target antenna is designed. The material used is economical FR4 material, which is small in size, and the overall antenna structure is simple and easy to process. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a schematic diagram of the structure of the antenna of this embodiment;

[0021] Figure 2 is the return loss (S) of the antenna in this embodiment. 11 ) Parameter simulation results;

[0022] Figure 3 is the antenna isolation of this embodiment (S 21 )Parameter simulation results.

[0023] Reference numerals:

[0024] 1 is a circular radiation patch; 2 is a 50Ω microstrip feed line; 3 is a coplanar floor; 4 is an isolation branch. DETAILED DESCRIPTION

[0025] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0026] Example

[0027] like Figure 1 As shown, a CPW-fed high-isolation dual-stopband MIMO antenna includes a substrate, an antenna and a coplanar floor 3. The antenna includes two radiating units, each radiating unit contains a circular monopole UWB antenna, the two circular monopole UWB antennas are perpendicular to each other, and SRR grooves are etched on the circular monopole UWB antennas.

[0028] The circular monopole UWB antenna includes a circular radiation patch 1 and a 50Ω microstrip feed line 2. An SRR slot is etched on the circular radiation patch. The SRR slot includes an open rectangular slot and an arc-shaped slot. The openings of the rectangular slot and the arc-shaped slot are arranged back to back, and the opening of the rectangular slot is located on the longer side. The 50Ω microstrip feed line 2 is trapezoidal.

[0029] An isolation branch is provided between the two circular monopole UWB antennas.

[0030] The antenna and the isolation branch are both axisymmetric structures, and the axis of symmetry is the axis of the isolation branch.

[0031] The isolation branch is strip-shaped as a whole, and V-shaped branches are provided at both ends of the isolation branch.

[0032] The ground plate is an irregular hexagon formed by cutting off two diagonal corners of a square.

[0033] This embodiment uses FR4 with a dielectric constant of 4.4 and a thickness of 0.8mm as the dielectric substrate, and places the circular monopole UWB antenna vertically on the dielectric substrate. Polarization diversity and isolation of branches are used to achieve high isolation. At the same time, SRR slots are etched on the radiation patch and the coplanar ground. The currents of the corresponding frequencies are concentrated around these SRR slots. The currents on both sides of the slots are equal in magnitude and opposite in direction, so that the electric fields generated by the corresponding currents in the far field are opposite in direction. The result of vector superposition is zero, and the stopband characteristics are obtained. Finally, a high-isolation two-stopband MIMO antenna fed by an asymmetric coplanar waveguide (CPW) is designed.

[0034] The present invention embeds an SRR slot on the radiation patch. On the one hand, the introduced slot can increase the length of the current flow path on the patch, which can be beneficial to widening the working range of the antenna; on the other hand, the SRR slot is equivalent to a "filter" and can filter out the target frequency band through adjustment.

[0035] like Figure 2 As shown, the overall operating range of the antenna is 2.58-12GHz (S 11 <-10dB), two of which are S 11>-10dB is the frequency band in which the antenna does not work, that is, the frequency band that needs to be "filtered out": 3.27-3.8GHz, 4.9-5.56GHz. These frequency bands correspond to Wi MAX (3.3~3.7GHz) and WLAN (5.15~5.35GHz) systems respectively, that is, the antenna can be free from interference from the above systems.

[0036] Figure 3 The isolation S of the antenna is shown as 21 , general design requirements only require S 21 <-15dB, and this antenna achieves S in the 2-12GHz range 21 <-20dB, with high isolation.

Claims

1. A CPW-fed high-isolation two-stopband MIMO antenna, characterized in that: It includes a substrate, an antenna and a ground plate, wherein the antenna includes two radiating units, each radiating unit contains a circular monopole UWB antenna, the two circular monopole UWB antennas are perpendicular to each other, and the circular monopole UWB antenna corrodes an SRR slot; The circular monopole UWB antenna comprises a circular radiation patch and a 50Ω microstrip feed line, an SRR slot is etched on the circular radiation patch, the SRR slot comprises an open rectangular slot and an arc-shaped slot, and the openings of the rectangular slot and the arc-shaped slot are arranged back to back; An isolation branch is provided between the two circular monopole UWB antennas; the isolation branch is in a strip shape as a whole, and branches are provided at both ends of the isolation branch, and the branches are in a V shape; The grounding plate is an irregular hexagon formed by cutting off two diagonal corners of a square.

2. A CPW-fed high-isolation dual-stopband MIMO antenna according to claim 1, characterized in that: The antenna and the isolation branch are both axisymmetric structures, and the axis of symmetry is the axis of the isolation branch.

3. A CPW-fed high-isolation dual-stopband MIMO antenna according to claim 1, characterized in that: The substrate material is FR4.

4. A CPW-fed high-isolation dual-stopband MIMO antenna according to claim 3, characterized in that: The substrate has a dielectric constant of 4.4 and a thickness of 0.8 mm.

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