Dual-polarization frequency reconfigurable microstrip patch filter antenna for full-duplex communication

Abstract

A dual-polarization frequency reconfigurable microstrip patch filter antenna for full-duplex communication includes a stacked bottom dielectric substrate, a metal reflective floor, an intermediate dielectric substrate, a top dielectric substrate and a microstrip patch, a transmitting end microstrip feeder is arranged on the lower surface of the bottom dielectric substrate, a variable capacitance loaded frequency tuning microstrip line that overlaps the microstrip patch non-contactly through the top substrate is arranged on the upper surface of the intermediate dielectric substrate, and a pair of λ / 4 T-type microstrip line resonators symmetrical about the center line of the frequency tuning microstrip line are arranged on the horizontal center plane of the microstrip patch. The present invention introduces a pair of λ / 4T-type microstrip line resonators at the receiving port of the microstrip patch to generate two radiation zero points to obtain good filtering performance and generate a high-frequency resonance point that can be used to expand the working bandwidth of the antenna; the overlapping area of ​​the frequency tuning microstrip line and the microstrip patch is controlled by adjusting the variable capacitance, so that the resonance mode of the transmitting end of the microstrip patch can be tuned.

Description

Technical Field

[0001] The invention relates to the technical field of wireless communications, and in particular to a dual-polarization frequency reconfigurable microstrip patch filter antenna for full-duplex communication. Background Art

[0002] The spectrum resources available at present are very limited. With the rapid development of wireless communication, these spectrum resources are becoming increasingly crowded. How to improve spectrum utilization has become a key research topic. At present, most wireless communication systems have terminals that transmit and receive signals (such as base stations, relays, and mobile terminals). Most of these communication systems are time-division or frequency-division duplex communication systems, which means that these terminals do not transmit and receive signals at the same time or frequency band. The simultaneous full-duplex communication system is different. It can ensure that the transmission and reception of signals are completed at the same time and on the same frequency, thereby doubling the transmission speed of data streams, the communication capacity of wireless communication systems, and the spectrum utilization.

[0003] The biggest challenge in implementing a full-duplex wireless communication system is to ensure that the transmitter and receiver have sufficiently high isolation. The isolation of a full-duplex communication system is contributed by the simultaneous co-frequency full-duplex antenna used in the RF front end, the analog RF self-interference elimination stage, and the digital baseband self-interference elimination stage. By increasing the isolation between the transmit and receive ports of the full-duplex antenna, the requirements for the subsequent self-interference elimination stage can be relaxed. Therefore, in order to improve the utilization of spectrum resources, it is of great scientific research value to study full-duplex antennas.

[0004] Full-duplex antennas can be realized through direct cascade duplexers, spatial diversity, near-field cancellation, and polarization diversity. Polarization diversity only requires a single antenna to achieve high isolation, and the structure is very compact. The two orthogonal polarization modes, horizontal and vertical, have uncorrelated paths, which brings natural high isolation.

[0005] However, this traditional microstrip patch antenna mostly works in single mode with a narrow working bandwidth, which is not suitable for high-speed and large-capacity applications. Therefore, it is necessary to expand the bandwidth of full-duplex antennas. Expanding the antenna bandwidth can be achieved by parasitic patches, introducing LC resonant circuits, or introducing gaps on the radiating patch, but these methods will inevitably lead to complex antenna structures and higher profiles. In recent years, the method of expanding the bandwidth and introducing filtering performance by using a special shape of feeding structure has received widespread attention. The antenna realized by this method not only expands the bandwidth of the antenna, but also has good filtering performance without the need for any additional filtering circuits, effectively avoiding the introduction of additional losses.

[0006] On the other hand, with the rapid development of wireless communication systems, frequency reconfigurable communication systems have attracted more and more attention due to their efficient use of spectrum. Such antennas can be realized by loading tunable elements, for example, using pin diodes to switch between multiple discrete states, or loading variable capacitors to continuously tune the working state. In addition, reconfigurable performance can also be achieved by using radio frequency micro-electromechanical systems (MEMS) or liquid metals. However, there is currently no full-duplex antenna that combines frequency reconfigurability with broadband filtering performance. Summary of the invention

[0007] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and propose a dual-polarization frequency reconfigurable microstrip patch filter antenna for full-duplex communication. The antenna is based on a traditional three-port microstrip radiation patch and adopts polarization diversity technology to achieve high port isolation between the transmitter and the receiver. A pair of λ / 4T-type microstrip line resonators are introduced at the receiving end of the full-duplex antenna and coupled with a rectangular microstrip patch. By effectively utilizing the T-type resonator, two radiation zero points can be generated at the receiving end to obtain good filtering performance and an additional high-frequency resonance point to expand the bandwidth. The frequency tuning microstrip line loaded with variable capacitance is embedded in the middle layer of the two stacked substrates of the microstrip patch antenna as a tuning structure, thereby realizing the tuning of the resonant mode of the microstrip patch transmitter, while the radiation zero point and the resonance point of the receiving end are not affected, thereby realizing the frequency reconfiguration of the antenna transmitter.

[0008] To achieve the purpose of the present invention, the present invention proposes a dual-polarization frequency reconfigurable microstrip patch filter antenna for full-duplex communication, comprising a bottom dielectric substrate, a metal reflection floor, an intermediate dielectric substrate, a top dielectric substrate and a microstrip patch stacked in sequence from bottom to top, wherein a transmitting end microstrip feed line for coupling feeding is arranged on the lower surface of the bottom dielectric substrate, and a coupling gap corresponding to the transmitting end microstrip feed line is opened on the metal reflection floor, and the characteristic is that: a variable capacitance loaded frequency tuning microstrip line is arranged on the upper surface of the intermediate dielectric substrate and is located directly above the transmitting end microstrip feed line and overlapped with the microstrip patch in a non-contact manner via the top substrate, and a pair of λ / 4T-type microstrip line resonators symmetrical about the center line of the frequency tuning microstrip line are arranged on the horizontal mid-plane of the microstrip patch.

[0009] The present invention introduces a pair of λ / 4T-type microstrip line resonators at the receiving port of the microstrip patch to generate two radiation zero points to obtain good filtering performance and generate additional high-frequency resonance points that can be used to expand the antenna working bandwidth. In order to realize the frequency reconfiguration function of the transmitting end, a non-contact variable capacitor loaded frequency tuning microstrip line is placed along the x-axis direction as a tuning structure. The microstrip line is embedded in the middle layer and partially overlaps with the microstrip patch. The through hole passing through the top substrate is used to connect the varactor placed on the upper surface of the top substrate. By adjusting the variable capacitor to control the overlapping area of ​​the frequency tuning microstrip line and the microstrip patch, the resonance mode of the transmitting end of the microstrip patch can be tuned, and the frequency of the transmitting end of the antenna can be reconfigured. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The present invention will be further described below in conjunction with the accompanying drawings.

[0011] Figure 1 It is a stereoscopic diagram of the reconfigurable microstrip patch full-duplex filtering antenna of the present invention.

[0012] Figure 2 It is a schematic diagram of the structure of the reconfigurable microstrip patch full-duplex filtering antenna of the present invention.

[0013] Figure 3 It is the simulated return loss of the transmitting end and the receiving end of the reconfigurable microstrip patch full-duplex filtering antenna of the present invention.

[0014] Figure 4 It is the simulated return loss and gain of the receiving end of the reconfigurable microstrip patch full-duplex filtering antenna of the present invention.

[0015] Figure 5 The invention relates to port isolation of a transmitting end and a receiving end of a reconfigurable microstrip patch full-duplex filtering antenna.

[0016] Figure 6 This is the simulated radiation pattern of the transmitting end of the reconfigurable microstrip patch full-duplex filtering antenna of the present invention at 2.52 GHz when the adjustable capacitance is 0.3 pF.

[0017] Figure 7 It is the simulated radiation pattern of the transmitting end of the reconfigurable microstrip patch full-duplex filtering antenna of the present invention at 2.46 GHz when the adjustable capacitance is 0.7 pF.

[0018] Figure 8 It is a simulated radiation pattern of the receiving end of the reconfigurable microstrip patch full-duplex filtering antenna of the present invention at 2.45 GHz.

[0019] Fig. 9 It is a simulated radiation pattern of the receiving end of the reconfigurable microstrip patch full-duplex filtering antenna of the present invention at 2.53 GHz.

[0020] The numbers in the figure are as follows:

[0021] 1-microstrip patch, 2-receiving end microstrip feed line, 3-third metallized through hole, 4-variable capacitor, 5-first metallized through hole, 6-second metallized through hole, 7-top dielectric substrate, 8-microstrip line for frequency tuning, 9-middle dielectric substrate, 10-metal ground, 11-coupling slot, 12-bottom dielectric substrate, 13-transmitting end microstrip feed line. DETAILED DESCRIPTION

[0022] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0023] like Figure 1 , Figure 2 As shown, the dual-polarization frequency reconfigurable microstrip patch filter antenna for full-duplex communication in this embodiment is symmetrical along the xoz axis plane. The antenna includes a bottom dielectric substrate 12, a metal reflection floor 10, an intermediate dielectric substrate 9, a top substrate 7 and a microstrip patch 1 which are stacked in sequence from bottom to top. A transmitting end microstrip feed line 13 for coupling feeding is provided on the lower surface of the bottom dielectric substrate 12, and a coupling slot 11 corresponding to the transmitting end microstrip feed line 13 is provided on the metal reflection floor 10. The microstrip patch 1 is a rectangular microstrip patch. A frequency tuning microstrip line 8 is provided on the upper surface of the intermediate dielectric substrate 9, which is located directly above the transmitting end microstrip feed line 13. The frequency tuning microstrip line 8 overlaps the microstrip patch 1 non-contactly across the top substrate 7, and the frequency tuning microstrip line 8 is loaded with a variable capacitor 4. A pair of λ / 4T-type microstrip line resonators 2 are arranged on the horizontal midplane of the microstrip patch 1. The T-type microstrip line resonators 2 are symmetrical about the center line of the frequency tuning microstrip line 8. The T-type microstrip line resonators 2 are grounded through a pair of metallized through holes 3.

[0024] The frequency tuning microstrip line 8 is arranged on the vertical mid-plane between the top-layer substrate 7 and the middle-layer substrate 9. The variable capacitor 4 is a varactor diode, and the frequency tuning microstrip line 8 and the variable capacitor 4 form a non-contact bandwidth tuning structure. As shown in the figure, the variable capacitor 4 is arranged on the upper surface of the top-layer dielectric substrate 7, the outer end of the variable capacitor 4 is grounded, and the inner end of the variable capacitor 4 is electrically connected to the outer end of the frequency tuning microstrip line 8. Specifically, the outer end of the variable capacitor 4 is grounded through a first metallized through-hole 5 that passes through the middle-layer dielectric substrate 9 and the top-layer dielectric substrate 7, and the inner end of the variable capacitor 4 is electrically connected to the outer end of the frequency tuning microstrip line 8 through a second metallized through-hole 6 that passes through the top-layer dielectric substrate 7. Figure 1 As shown, the λ / 4T-type microstrip line resonator 2 is grounded through a third metallized through hole 3 , and the third metallized through hole 3 runs through the middle-layer dielectric substrate 9 and the top-layer dielectric substrate 7 .

[0025] The frequency tuning microstrip line 8 and the variable capacitor 4 form a non-contact bandwidth tuning structure. The transmitting end operating frequency of the microstrip patch antenna is tuned by adjusting the capacitance C of the variable capacitor. The embodiment of the present invention optimizes the size of each part of the antenna. The specific antenna parameters are shown in the following table:

[0026] parameter <![CDATA[l g ]]> <![CDATA[h1]]> <![CDATA[h2]]> <![CDATA[h3]]> <![CDATA[l p ]]> <![CDATA[w f ]]> <![CDATA[l f ]]> d Value(mm) 90 0.813 1.524 1.524 30.5 3.5 9 4.8 parameter w <![CDATA[l i ]]> <![CDATA[l s ]]> <![CDATA[w s ]]> <![CDATA[w f2 ]]> <![CDATA[l f2 ]]> <![CDATA[w r ]]> <![CDATA[l r ]]> Value(mm) 3 7.6 14 1.2 4.8 22 1.04 14.6

[0027] In the table, h1, h2, and h3 are the heights of the top dielectric substrate 7, the middle dielectric substrate 9, and the bottom dielectric substrate 12, respectively. p is the side length of the microstrip patch 1, d is the distance between the receiving end T-type microstrip line resonator 2 and the edge of the microstrip patch 1, w is the width of the frequency tuning microstrip line 8, l i is the length of the frequency tuning microstrip line 8 that overlaps the microstrip patch 1 in a non-contact manner across the top substrate 7, l s and w s are the length and width of the coupling slot 11 at the transmitting end, l r and w r are the length and width of the second branch of the T-type microstrip line resonator respectively.

[0028] The substrate used in the design is Rogers RO4003, which has a dielectric constant of ε r =3.38, loss tangent is tanδ=2.7×10 -3 , the volume of the top substrate 7 is l g × g ×h1, the volume of the intermediate substrate 9 is l g × g ×h2, the volume of the bottom substrate 12 is l g × g ×h3, the intermediate layer substrate 9 is a double-sided printed circuit board, the upper surface of the double-sided printed circuit board 9 is a frequency tuning microstrip line 8, and the lower surface is a metal reflection floor 11.

[0029] Figure 3 The simulated reflection coefficient of the transmitter of the frequency reconfigurable microstrip patch full-duplex filter antenna in this example under different capacitance values ​​and the simulated reflection coefficient of the receiver, the frequency adjustment range is 4.5%. It can be seen from the figure that the operating frequency of the transmitter moves down as C increases.

[0030] Figure 4 The simulated reflection coefficient and gain of the receiving end of the frequency reconfigurable microstrip patch full-duplex filter antenna in this example have a bandwidth of 4% and a maximum gain of 6.8dBi in the band.

[0031] Figure 5 The port isolation between the transmitting end and the receiving end of the frequency reconfigurable microstrip patch full-duplex filtering antenna in this example has an isolation degree greater than 65dB.

[0032] Figure 6-Figure 7 The simulated E-plane and H-plane radiation patterns of the antenna transmitter at different variable capacitor values ​​of 0.3pF and 0.7pF. It can be seen from the figure that the cross polarization of the antenna is at least 20dB lower than the main polarization. At the same time, it can be inferred that the antenna can show a stable broadside radiation pattern in the entire frequency tuning range.

[0033] Figure 8-Figure 9 The simulated E-plane and H-plane radiation patterns of the antenna receiving end at 2.45GHz and 2.53GHz are shown in the figure. It can be seen from the figure that the cross polarization of the antenna is at least 20dB lower than the main polarization.

[0034] In addition to the above embodiments, the present invention may also have other implementation modes. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope required by the present invention.

Claims

1. A dual-polarization frequency reconfigurable microstrip patch filter antenna for full-duplex communication, comprising a bottom dielectric substrate (12), a metal reflective floor (10), an intermediate dielectric substrate (9), a top dielectric substrate (7) and a microstrip patch (1) stacked in sequence from bottom to top, wherein a transmitting end microstrip feed line (13) for coupling feeding is arranged on the lower surface of the bottom dielectric substrate (12), and the metal reflective floor (10) is provided with a coupling slot (11) corresponding to the transmitting end microstrip feed line (13), characterized in that: The upper surface of the intermediate dielectric substrate (9) is provided with a frequency tuning microstrip line (8) loaded with a variable capacitor (4) and located directly above the transmitting end microstrip feed line (13) and overlapping the microstrip patch (1) in a non-contact manner via the top dielectric substrate (7); a pair of λ / 4 T-type microstrip line resonators (2) symmetrical about the center line of the frequency tuning microstrip line (8) are provided on a horizontal mid-plane of the microstrip patch (1); the frequency tuning microstrip line (8) and the variable capacitor (4) form a non-contact frequency tuning structure.

2. The dual-polarization frequency reconfigurable microstrip patch filter antenna for full-duplex communication according to claim 1, characterized in that: The variable capacitor (4) is arranged on the upper surface of the top dielectric substrate (7); the outer end of the variable capacitor (4) is grounded via a first metallized through hole (5); and the inner end of the variable capacitor (4) is electrically connected to the outer end of a frequency tuning microstrip line (8) via a second metallized through hole (6).

3. The dual-polarization frequency reconfigurable microstrip patch filter antenna for full-duplex communication according to claim 2, characterized in that: The outer end of the variable capacitor (4) is electrically connected to the metal reflective floor (10) via a first metallized through hole (5) penetrating the middle dielectric substrate (9) and the top dielectric substrate (7), and the second metallized through hole (6) penetrating the top dielectric substrate (7).

4. The dual-polarization frequency reconfigurable microstrip patch filter antenna for full-duplex communication according to claim 1, characterized in that: The λ / 4 T-type microstrip line resonator (2) is grounded via a third metallized through hole (3).

5. The dual-polarization frequency reconfigurable microstrip patch filter antenna for full-duplex communication according to claim 4, characterized in that: The λ / 4 T-type microstrip line resonator (2) is electrically connected to the metal reflective floor (10) via a third metallized through hole (3) that penetrates the middle-layer dielectric substrate (9) and the top-layer dielectric substrate (7).

6. The dual-polarization frequency reconfigurable microstrip patch filter antenna for full-duplex communication according to claim 1, characterized in that: The frequency tuning microstrip line (8) is located on the vertical mid-plane of the intermediate layer dielectric substrate (9).

7. The dual-polarization frequency reconfigurable microstrip patch filter antenna for full-duplex communication according to claim 1, characterized in that: The overlapping area between the frequency tuning microstrip line (8) and the microstrip patch (1) is controlled by adjusting the capacitance value of the variable capacitor (4), thereby tuning the operating frequency of the transmitting end of the microstrip patch filter antenna.

8. The dual-polarization frequency reconfigurable microstrip patch filter antenna for full-duplex communication according to claim 1, characterized in that: The variable capacitor (4) is a variable capacitance diode.

9. The frequency reconfigurable dual-polarization microstrip patch filter antenna for full-duplex communication according to claim 1, characterized in that: The microstrip patch (1) is a rectangular microstrip patch.

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