A radio frequency circuit and base station antenna stripline combiner

Abstract

The present invention relates to the field of radio frequency technology, and in particular to a radio frequency circuit and a base station antenna stripline combiner using the radio frequency circuit. The radio frequency circuit includes a high-frequency path transmission line, a low-frequency path transmission line, and a combiner matching transmission line. The high-frequency path transmission line is provided with at least two spiral open-circuit resonant branches, and the low-frequency path transmission line is provided with at least two spiral open-circuit resonant branches. The stripline combiner includes a combiner cavity, a combiner dielectric substrate, and a PCB printed circuit board, a radio frequency circuit, and the radio frequency circuit is printed on the top and bottom of the PCB printed circuit board and connected through metallized vias. The PCB printed circuit board is placed in the combiner cavity. The present invention utilizes spiral open-circuit resonant branches and folded high-frequency path transmission lines to effectively reduce the lateral size of the radio frequency circuit and reduce its own cost. In addition, the out-of-band zero point generated by the spiral open-circuit resonant branches helps to improve out-of-band suppression.

Description

Technical Field

[0001] The present invention relates to the field of radio frequency technology, and in particular to a radio frequency circuit and a base station antenna stripline combiner using the radio frequency circuit. Background Art

[0002] With the rapid development of mobile communication technology and the dramatic increase in mobile communication traffic, there is an urgent need to increase the number of cellular cells and improve cell coverage quality to meet development needs and enhance user experience. In current mobile communication systems, operators often adopt a multi-system co-site approach to address the difficulties in site selection and high site construction costs. Multi-frequency shared antennas are a preferred solution.

[0003] However, current resonant cavity combiners have problems such as heavy weight, large size, high cost, difficulty in processing and assembly, making them unsuitable for integration into antennas. Although microstrip combiners can be built into antennas, their poor stability and high insertion loss reduce the antenna gain, which is not conducive to antenna signal coverage.

[0004] Therefore, the industry is in urgent need of a technical solution to the above technical problems. Summary of the Invention

[0005] To solve at least one of the above problems, the present invention provides a radio frequency circuit and a base station antenna stripline combiner using the radio frequency circuit.

[0006] In order to achieve the purpose of the present invention, the following technical solutions are adopted:

[0007] The present invention proposes a radio frequency circuit, which includes a high-frequency path transmission line, a low-frequency path transmission line and a combined matching transmission line. The high-frequency path transmission line is provided with at least two spiral open-circuit resonant branches, and the low-frequency path transmission line is provided with at least two spiral open-circuit resonant branches.

[0008] A further improvement is that the combined matching transmission line is composed of at least two sections of folded transmission lines with different widths.

[0009] A further improvement is that the high-frequency path transmission line is composed of at least three sections of transmission line folded lines with different widths, and a spiral open-circuit resonant branch is provided at the connection between any two of the at least three sections of transmission line with different widths.

[0010] A further improvement is that the low-frequency path transmission line is composed of at least three sections of transmission lines with different widths, and a spiral open-circuit resonant branch is provided at the connection between any two sections of the at least three sections of transmission lines with different widths.

[0011] A further improvement is that the spiral open-circuit resonant branches are arranged on the same side and / or different sides of the high-frequency path transmission line / the low-frequency path transmission line, and are isolated from each other by the high-frequency path transmission line / the low-frequency path transmission line.

[0012] A further improvement is that the transmission line widths of the combined matching transmission line and the high-frequency path transmission line are larger than the transmission line width of the low-frequency path transmission line.

[0013] On the other hand, the present invention proposes a base station antenna stripline combiner, which includes a combiner cavity, a combiner dielectric substrate and a PCB printed circuit board, and also includes a radio frequency circuit described in any one of the above items, wherein the radio frequency circuit is printed on the top and bottom of the PCB printed circuit board and connected through metallized vias, and the PCB printed circuit board is placed in the combiner cavity.

[0014] A further improvement is that the distance between adjacent metallized vias is less than one eighth of the operating wavelength.

[0015] A further improvement is that the medium base material of the combiner is air.

[0016] A further improvement is that the combiner cavity is formed by pultrusion of aluminum alloy and the surface is electroplated with tin to facilitate welding.

[0017] Compared with the prior art, the solution of the present invention has the following advantages:

[0018] 1. In the RF circuit described in the present invention, the use of spiral open-circuit resonant branches and folded routing of high-frequency path transmission lines can further effectively reduce the lateral size of the RF circuit and reduce its own cost. In addition, the out-of-band zero point generated by the spiral open-circuit resonant branches helps to improve out-of-band suppression.

[0019] 2. In the radio frequency circuit of the present invention, the width of the combining and matching transmission line and the high-frequency path transmission line is relatively wide, which helps to reduce the insertion loss of the radio frequency circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the planar structure of the PCB printed circuit board in the present invention;

[0021] Figure 2 A side cross-sectional view of a stripline combiner for a base station antenna according to the present invention;

[0022] Figure 3 This is a simulation result diagram of the present invention.

[0023] Explanation of the accompanying drawings: 1-combiner cavity, 2-PCB printed circuit board, 3-combiner dielectric substrate, 11-signal combining port, 22-high-frequency signal port, 33-low-frequency signal port, 100-combiner matching transmission line, 200-high-frequency path transmission line, 300-low-frequency path transmission line, 44-metallized via, 1001-first spiral open-circuit resonant branch, 1002-second spiral open-circuit resonant branch, 1003-third spiral open-circuit resonant branch, 1004-fourth spiral open-circuit resonant branch. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. These drawings are simplified schematic diagrams, which only illustrate the basic structure of the present invention in a schematic manner. Therefore, the drawings only show the structures related to the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0025] It should be noted that when an element is referred to as being “mounted on” another element, it may be directly on the other element or there may be an intermediate element. When an element is referred to as being “connected to” another element, it may be directly connected to the other element or there may be an intermediate element.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention pertains. The terms used herein in the specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The terms "and" and "and" as used herein include any and all combinations of one or more of the associated listed items.

[0027] To more clearly present the technical solution of the present invention, this paper uses a base station antenna stripline combiner using a radio frequency circuit as an example to comprehensively and systematically introduce the technical solution of the present invention. It should be noted that the examples listed in this specification are only some embodiments and should not be construed as limiting the application scenarios of the technical solution of the present invention.

[0028] Please refer to Figure 1 、 Figure 2 、 Figure 3, an embodiment of the present invention provides a 703MHz-798MHz / 885MHz-960MHz base station antenna stripline combiner, which can be used for built-in combining of base station antennas. The stripline combiner is a dual-cavity structure with two upper and lower layers, including two combiner RF circuits, and is suitable for dual-polarization base station antenna arrays. The stripline combiner includes a combiner cavity 1, a PCB printed circuit board 2, and a combiner dielectric substrate 3. The RF circuit is printed on the top and bottom of the PCB printed circuit board 2 and is connected through metallized vias 44. The PCB printed circuit board 2 is placed in the combiner cavity 1.

[0029] Specifically, in a preferred solution of the embodiment of the present invention, the distance between adjacent metallized vias 44 is less than one eighth of the operating wavelength.

[0030] Specifically, in a preferred solution of the embodiment of the present invention, the combiner medium substrate 3 is preferably air.

[0031] In a preferred embodiment of the present invention, the combiner cavity 1 is formed by pultrusion of aluminum alloy and electroplated with tin on the surface for easy soldering. The PCB printed circuit board 2 has good anti-interference performance, which helps to improve intermodulation stability.

[0032] Specifically, in an embodiment of the present invention, a radio frequency circuit is printed on the PCB printed circuit board 2, and the radio frequency circuit includes a high-frequency path transmission line 200, a low-frequency path transmission line 300 and a combining matching transmission line 100. The high-frequency path transmission line 200 is provided with at least two spiral open-circuit resonant branches, and the low-frequency path transmission line 300 is provided with at least two spiral open-circuit resonant branches.

[0033] Preferably, in the embodiment of the present invention, the combined and matched transmission line 100 is composed of at least two sections of folded transmission lines with different widths. Those skilled in the art may set the specific number of transmission lines in the combined and matched transmission line 100 according to actual needs, as long as there are at least two sections of transmission lines with different widths.

[0034] Preferably, in an embodiment of the present invention, the high-frequency path transmission line 200 is composed of at least three folded transmission line segments of varying widths, and a spiral open-circuit resonant branch is provided at the junction of any two of the at least three folded transmission line segments of varying widths. Those skilled in the art may adjust the specific number of transmission lines in the high-frequency path transmission line 200 based on actual needs, as long as the high-frequency path transmission line 200 comprises at least three folded transmission line segments of varying widths.

[0035] Preferably, in an embodiment of the present invention, the low-frequency path transmission line 300 is composed of at least three transmission line segments of varying widths, with a spiral open-circuit resonant branch provided at the junction of any two of the at least three transmission line segments of varying widths. Those skilled in the art may adjust the specific number of transmission lines in the low-frequency path transmission line 300 based on actual needs, as long as the low-frequency path transmission line 300 comprises at least three transmission line segments of varying widths.

[0036] By setting the combiner matching transmission line 100, the low-frequency path transmission line 300 and the high-frequency path transmission line 200 to be composed of multiple transmission lines with different widths, and at the same time, the combiner matching transmission line 100 and the high-frequency path transmission line 200 are folded and routed, it helps to adjust and improve the impedance matching effect of the combiner, reduce the return loss, and effectively reduce the lateral size of the RF circuit.

[0037] Specifically, if Figure 1 As shown, taking an embodiment of the present invention as an example, the combined matching transmission line 100 is composed of two sections of folded transmission line traces with different widths. The high-frequency path transmission line 200 is composed of three sections of folded transmission line traces with different widths. Accordingly, the three sections of transmission line traces with different widths in the high-frequency path transmission line 200 are provided with two spiral open resonant branches, namely, a first spiral open resonant branch 1001 and a first spiral open resonant branch 1002. The low-frequency path transmission line 300 is composed of three sections of transmission line traces with different widths. Accordingly, the three sections of transmission line traces with different widths in the low-frequency path transmission line 300 are provided with two spiral open resonant branches, namely, a third spiral open resonant branch 1003 and a fourth spiral open resonant branch 1004. Spiral open resonant branches, i.e., spiral-shaped open resonant branches, can more effectively reduce the lateral size of RF circuits compared to open branches in the prior art, while also generating out-of-band zeros and improving out-of-band suppression.

[0038] Specifically, in an embodiment of the present invention, the RF circuit includes a combining and matching transmission line 100, a high-frequency path transmission line 200, a low-frequency path transmission line 300, a metallized via 44, a first spiral open-circuit resonant branch 1001, a second spiral open-circuit resonant branch 1002, a third spiral open-circuit resonant branch 1003, and a fourth spiral open-circuit resonant branch 1004. The RF signal is input from the signal combining port 11, and when passing through the high-frequency path transmission line 200, the first spiral open-circuit resonant branch 1001 and the second spiral open-circuit resonant branch 1002 generate zero-point suppression of the 703MHz-798MHz frequency band signal and the 885MHz-960MHz frequency band signal, which arrive at the high-frequency signal port 22; when passing through the low-frequency path transmission line 300, the third spiral open-circuit resonant branch 1003 and the fourth spiral open-circuit resonant branch 1004 generate zero-point suppression of the 885MHz-960MHz frequency band signal and the 703MHz-798MHz frequency band signal, which arrive at the low-frequency signal port 33 to realize the combining / splitting function of the RF signal.

[0039] At the same time, the transmission line widths of the combined matching transmission line 100 and the high-frequency path transmission line 200 are controlled to be relatively wide. The transmission line widths of the combined matching transmission line 100 and the high-frequency path transmission line 200 are larger than the transmission line widths of the low-frequency path transmission line 300, which is beneficial to reducing insertion loss. In addition, the combined matching transmission line 100 and the high-frequency path transmission line 200 adopt a folded routing method, which can cooperate with the spiral open-circuit resonant branch to further effectively reduce the lateral size of the RF circuit and reduce its own cost.

[0040] Furthermore, the spiral open-circuit resonant branches are arranged on the same side and / or different sides of the high-frequency path transmission line 200 / low-frequency path transmission line 300, and are isolated from each other by the high-frequency path transmission line 200 / low-frequency path transmission line 300, thereby improving the stability of circuit performance.

[0041] It should be pointed out that in other embodiments, there is no limit on the number of spiral open-circuit resonant branches of the high-frequency path transmission line 200 and / or the low-frequency path transmission line 300, as long as the number is at least two and the path bandwidth requirements of the high-frequency path transmission line 200 and the low-frequency path transmission line 300 are met.

[0042] like Figure 3As shown, the present invention generates out-of-band zeros by folding the transmission line and applying spiral open-circuit resonant branches, improving out-of-band rejection while effectively shortening the combiner's lateral dimensions and reducing its cost. The combiner achieves return loss below -21dB in both the 703MHz-798MHz and 885MHz-960MHz operating frequency bands, out-of-band rejection below -28dB, and in-band insertion loss within -0.2dB. The combiner boasts superior overall electrical performance, high stability, a simple structure, ease of installation, a compact size, and low cost.

[0043] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0044] The above-described embodiments merely represent specific implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, and all such variations and improvements fall within the scope of protection of the present invention.

Claims

1. A radio frequency circuit, characterized in that: Applicable to two operating frequency bands of 703MHz-798MHz and 885MHz-960MHz, the radio frequency circuit includes a high-frequency path transmission line, a low-frequency path transmission line, and a combined matching transmission line. The high-frequency path transmission line is provided with two spiral open-circuit resonant branches, and the low-frequency path transmission line is provided with two spiral open-circuit resonant branches; The combined matching transmission line is composed of two sections of folded transmission lines with different widths; the high-frequency path transmission line is composed of three sections of folded transmission lines with different widths, and the connection between any two of the three sections of transmission lines with different widths is provided with a spiral open-circuit resonant branch, which is a first spiral open-circuit resonant branch and a second spiral open-circuit resonant branch; the low-frequency path transmission line is composed of three sections of transmission lines with different widths, and the connection between any two of the three sections of transmission lines with different widths is provided with a spiral open-circuit resonant branch, which is a third spiral open-circuit resonant branch and a fourth spiral open-circuit resonant branch; the spiral open-circuit resonant branches can reduce the lateral size of the radio frequency circuit and can generate out-of-band zero points, thereby improving out-of-band suppression; The first spiral open-circuit resonant branch node and the second spiral open-circuit resonant branch node are arranged on the same side of the high-frequency path transmission line, and the high-frequency path transmission line with a folded routing isolates the first spiral open-circuit resonant branch node and the second spiral open-circuit resonant branch node from each other. The third spiral open-circuit resonant branch node and the fourth spiral open-circuit resonant branch node are arranged on different sides of the low-frequency path transmission line and are isolated from each other by the low-frequency path transmission line, thereby improving the stability of the circuit performance.

2. The radio frequency circuit according to claim 1, characterized in that: The transmission line widths of the combined matching transmission line and the high-frequency path transmission line are greater than the transmission line width of the low-frequency path transmission line.

3. A stripline combiner for a base station antenna, comprising a combiner cavity, a combiner dielectric substrate, and a PCB printed circuit board, characterized in that: It also includes a radio frequency circuit as described in any one of claims 1-2, wherein the radio frequency circuit is printed on the top and bottom of a PCB printed circuit board and connected through metallized vias, and the PCB printed circuit board is placed in the combiner cavity.

4. The stripline combiner for base station antenna according to claim 3, characterized in that: The distance between adjacent metalized vias is less than one eighth of the operating wavelength.

5. The stripline combiner for base station antenna according to claim 3, characterized in that: The medium base material of the combiner is air.

6. The stripline combiner for base station antenna according to claim 3, characterized in that: The combiner cavity is formed by pultrusion of aluminum alloy and the surface is electroplated with tin for easy welding.

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