Microstrip coupler, circuit board and communication device

Abstract

The application relates to a microstrip coupler, a circuit board and a communication device. The microstrip coupler comprises a first ground layer, a first dielectric layer, a second ground layer, a coupling line, a second dielectric layer, a third ground layer and a signal line. The first projection of the coupling line on the third ground layer in the direction perpendicular to the third ground layer is completely non-overlapped with the second hollow area, and the second projection of the signal line on the second ground layer in the direction perpendicular to the second ground layer is completely non-overlapped with the first hollow area. Thus, a cavity is not needed on the signal line as in the related art, so that the product volume of the microstrip coupler can be reduced, miniaturization design is realized, the line length of the output end and the input end of the signal line can be reduced, the insertion loss is reduced, and the output efficiency of the power amplifier is improved; the coupling line and other devices located on both sides of the signal line do not interfere with each other, so that the signal can be normally and stably transmitted; in addition, the product area is reduced, which is beneficial to the arrangement of other devices.

Description

Technical Field

[0001] This application relates to the field of antenna communication technology, and in particular to a microstrip coupler, circuit board and communication device. Background Technology

[0002] In radio frequency (RF) module products, microstrip couplers are widely used to extract useful RF signals due to their low cost, simple manufacturing, and easy integration. They are the necessary signal source for transceiver RF modules to realize signal power detection, standing wave detection, DPD and CFR functions, and are widely used in the output linearity design of power amplifiers and the calibration of RF channels.

[0003] In related technologies, the microstrip couplers that are widely used are all co-layer couplers, that is, the microstrip line that transmits the main signal and the microstrip line that transmits the coupled signal are both arranged on the same layer of the circuit board (PCB), usually on the top or bottom layer. This form occupies a lot of space, and when used for high-power RF signal detection, a separate shielding cavity design is required. This form has great limitations in terms of physical space, which is not conducive to device layout and miniaturization of RF modules, and increases insertion loss. Summary of the Invention

[0004] Therefore, it is necessary to overcome the shortcomings of the existing technology and provide a microstrip coupler, circuit board and communication device that can reduce the space required for layout, reduce the insertion loss at the power amplifier output and improve the output efficiency of the power amplifier.

[0005] A microstrip coupler, the microstrip coupler comprising:

[0006] First grounding layer;

[0007] A first dielectric layer is disposed on the first ground layer;

[0008] The second grounding layer is disposed on the first dielectric layer on a side opposite to the first grounding layer, and the second grounding layer is provided with a first hollow area;

[0009] The coupling line is located on the same layer as the second ground layer and is disposed on the first dielectric layer at a location corresponding to the first hollow area;

[0010] The second dielectric layer is disposed on the second ground layer;

[0011] A third grounding layer, wherein the third grounding layer is disposed on the second dielectric layer on a side opposite to the second grounding layer, and the third grounding layer has a second hollow area; and

[0012] The signal line is located on the same layer as the third ground layer and is disposed on the second dielectric layer at a location corresponding to the second cutout area;

[0013] Wherein, the first projection of the coupling line on the third ground layer along the direction perpendicular to the third ground layer does not overlap with the second hollow area, and the second projection of the signal line on the second ground layer along the direction perpendicular to the second ground layer does not overlap with the first hollow area.

[0014] In one embodiment, the coupling line includes a coupling end, a first main body, and an isolation end connected in sequence; the signal line includes an input end, a second main body, and an output end connected in sequence; the input end and the coupling end are located on the same side, the second main body and the first main body are positioned corresponding to each other and coupled to each other, and the output end and the isolation end are located on the same side.

[0015] In one embodiment, the horizontal spacing between the branches at both ends of the first main body and the signal line is set as D1 and D2, respectively, and the vertical distance between the signal line and the coupling line is set as H, wherein D1 and D2 are each independently set to 0.2mm to 1.2mm, and H is set to 4mil to 40mil.

[0016] In one embodiment, the first main body includes a plurality of coupled branches connected in series.

[0017] In one embodiment, one of the coupling branches located in the middle is configured as a U-shaped branch.

[0018] In one embodiment, the characteristic impedance of each of the coupling stubs between the coupling end and the U-shaped stub tends to increase in the direction from the coupling end to the isolation end;

[0019] The characteristic impedance of each of the coupling stubs between the U-shaped stub and the isolation end tends to decrease in the direction from the coupling end to the isolation end.

[0020] In one embodiment, each of the coupling branches between the coupling end and the U-shaped branch, and each of the coupling branches between the U-shaped branch and the isolation end, is rectangular in shape, and each of them is aligned with each other on the side edge away from the signal line and arranged on the same straight line.

[0021] In one embodiment, the U-shaped branch includes two first connecting arms spaced apart from each other and a second connecting arm connected to each of the two first connecting arms; the characteristic impedance of the second connecting arm is less than the characteristic impedance of the first connecting arm.

[0022] In one embodiment, the width of the first connecting arm is set to Wu, and the length of the coupling end is set to L. O The length of the isolation end is set to L. G L O ≥2Wu, L G ≥2Wu.

[0023] In one embodiment, the first dielectric layer includes a first split layer and a second split layer, and the microstrip coupler further includes a fourth ground layer. The first ground layer, the first split layer, the fourth ground layer, the second split layer, the second ground layer, the second dielectric layer, and the third ground layer are arranged sequentially. The fourth ground layer is provided with a third hollow area corresponding to the first hollow area.

[0024] A circuit board comprising the microstrip coupler.

[0025] A communication device, the communication device including the microstrip coupler.

[0026] In the aforementioned microstrip coupler, circuit board, and communication equipment, the coupling line and signal line are arranged on different dielectric layers. The first projection and the second cutout area do not overlap at all, and the second projection and the first cutout area do not overlap at all. In this way, on the one hand, the first ground layer, the second ground layer, and the third ground layer cooperate to form a metal shielding cavity for the coupling line, avoiding mutual interference between the coupling line and the external electromagnetic environment. This eliminates the need for a separate cavity on the signal line as in related technologies, allowing for a reduction in the product size of the microstrip coupler and enabling miniaturization. It also reduces the length of the output and input ends of the signal line, thereby reducing insertion loss and improving the output efficiency of the power amplifier. On the other hand, because the coupling line and signal line are arranged on different layers, the coupling energy transmission between them is along the vertical direction, not along the horizontal direction as in related technologies. This prevents the coupling line from interfering with other devices located on both sides of the signal line, ensuring normal and stable signal transmission. In addition, the reduced product board area facilitates the arrangement of other devices. Attached Figure Description

[0027] Figure 1 This is an exploded view of a microstrip coupler according to an embodiment of this application.

[0028] Figure 2 for Figure 1 A top view of the structure shown.

[0029] Figure 3 for Figure 1 The exploded structure diagram of the coupling lines in the structure shown.

[0030] Figure 4 for Figure 1 The exploded structure diagram of the coupling lines in the structure shown.

[0031] 10. First grounding layer; 20. First dielectric layer; 21. First split layer; 22. Second split layer; 30. Second grounding layer; 31. First cutout area; 40. Coupled line; 41. Coupled end; 42. First main body; 421. Coupled branch; 422. U-shaped branch; 4221. First connecting arm; 4222. Second connecting arm; 43. Isolation end; 50. Second dielectric layer; 60. Third grounding layer; 61. Second cutout area; 70. Signal line; 71. Input end; 72. Second main body; 73. Output end; 80. Fourth grounding layer; 81. Third cutout area. Detailed Implementation

[0032] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0033] See Figures 1 to 3 , Figure 1 An exploded view of a microstrip coupler according to an embodiment of this application is shown. Figure 2 It shows Figure 1 A top view of the structure shown. Figure 3 It shows Figure 1 The diagram shows an exploded view of the coupling line 40 in the structure shown. An embodiment of this application provides a microstrip coupler, comprising: a first ground layer 10, a first dielectric layer 20, a second ground layer 30, a coupling line 40, a second dielectric layer 50, a third ground layer 60, and a signal line 70. The first dielectric layer 20 is disposed on the first ground layer 10. The second ground layer 30 is disposed on the first dielectric layer 20 on a side opposite to the first ground layer 10, and has a first cutout area 31. The coupling line 40 is located on the same layer as the second ground layer 30 and is disposed on the first dielectric layer 20 at a location corresponding to the first cutout area 31. The second dielectric layer 50 is disposed on the second ground layer 30. The third ground layer 60 is disposed on the second dielectric layer 50 on a side opposite to the second ground layer 30, and has a second cutout area 61. The signal line 70 is located on the same layer as the third ground layer 60 and is disposed on the second dielectric layer 50 at a location corresponding to the second cutout area 61. Among them, the first projection of the coupling line 40 on the third ground layer 60 along the direction perpendicular to the third ground layer 60 does not overlap with the second cutout area 61 at all, and the second projection of the signal line 70 on the second ground layer 30 along the direction perpendicular to the second ground layer 30 does not overlap with the first cutout area 31 at all.

[0034] It should be noted that, since the first projection of the coupling line 40 on the third grounding layer 60 along the direction perpendicular to the third grounding layer 60 does not overlap with the second cutout area 61 at all, that is, the first projection completely avoids the second cutout area 61; similarly, the second projection completely avoids the first cutout area 31.

[0035] In the aforementioned microstrip coupler, the coupling line 40 and the signal line 70 are arranged on different dielectric layers. The first projection and the second cutout area 61 do not overlap at all, and the second projection and the first cutout area 31 do not overlap at all. In this way, on the one hand, the first ground layer 10, the second ground layer 30 and the third ground layer 60 cooperate to form a metal shielding cavity for the coupling line 40, avoiding mutual interference between the coupling line 40 and the external electromagnetic environment. This eliminates the need for a separate cavity on the signal line 70 as in related technologies, thereby reducing the product size of the microstrip coupler and achieving miniaturization. It also reduces the length of the output terminal 73 and the input terminal 71 of the signal line 70, thereby reducing insertion loss and improving the output efficiency of the power amplifier. On the other hand, because the coupling line 40 and the signal line 70 are arranged in different layers, the coupling energy transmission between them is along the vertical direction, not along the horizontal direction as in related technologies. This prevents the coupling line 40 from interfering with other devices located on both sides of the signal line 70, ensuring normal and stable signal transmission. In addition, the reduced product board area is beneficial for the arrangement of other devices.

[0036] Please see Figure 1 In this case, no grounding layer is provided above the signal line 70, and a second grounding layer 30 is provided below the signal line 70. Together with the second grounding layer 30 below it, they form a microstrip line.

[0037] In one embodiment, when a microstrip coupler is used in a castle structure, the number of castle interfaces can be reduced.

[0038] Please see Figures 1 to 3 In one embodiment, the coupling line 40 includes a coupling terminal 41, a first main body portion 42, and an isolation terminal 43 connected in sequence. Furthermore, the signal line 70 includes an input terminal 71, a second main body portion 72, and an output terminal 73 connected in sequence. The input terminal 71 and the coupling terminal 41 are located on the same side, the second main body portion 72 and the first main body portion 42 are positioned correspondingly and coupled to each other, and the output terminal 73 and the isolation terminal 43 are located on the same side.

[0039] In one embodiment, the impedance values ​​of the coupling terminal 41 and the isolation terminal 43 are respectively designed to be 50Ω, or can be any other value such as 100Ω, 150Ω, etc., depending on actual needs.

[0040] In one embodiment, the impedance values ​​of the input terminal 71 and the output terminal 73 are, but are not limited to, designed to be 50Ω, and can also be any other value such as 100Ω, 150Ω, etc., depending on actual needs.

[0041] Please see Figure 2 In this design, the horizontal distances between the branches at both ends of the first main body 42 and the signal line 70 are set as D1 and D2, respectively, and the vertical distance between the signal line 70 and the coupling line 40 is set as H, which is the thickness of the second dielectric layer 50. D1, D2, and H together determine the coupling degree between the coupling line 40 and the signal line 70. The coupling degree determined by these three parameters increases the degree of freedom compared to the coupling degree determined by a single distance in related technologies, and can achieve better coupling flatness.

[0042] Please see Figure 2 In one embodiment, D1 and D2 are each independently set to 0.2mm to 1.2mm, specifically for example, 0.2mm, 0.4mm, 0.6mm, 0.8mm, 1mm, 1.2mm, etc., or can be set to any value other than 0.2mm to 1.2mm. The specific values ​​can be flexibly adjusted and set according to actual needs, and are not limited here.

[0043] In one embodiment, H is set to 4mil to 40mil, specifically for values ​​such as 4mil, 10mil, 15mil, 20mil, 24mil, 30mil, 35mil, 40mil, etc. It can also be set to any value outside of 4mil to 40mil. The specific value can be flexibly adjusted and set according to actual needs, and is not limited here.

[0044] Please see Figures 1 to 3 The electrical length of the first main body 42 is set to 1 / 4 of the working wavelength, which includes, but is not limited to, regular shapes such as straight lines and broken lines, as well as other irregular shapes. The specific shape can be flexibly adjusted and set according to actual needs.

[0045] Please see Figures 1 to 3 In one embodiment, the first main body 42 includes a plurality of coupling branches 421 connected in series. This allows for flexible adjustment and setting of the length and width of each coupling branch 421 according to actual needs, thereby achieving better coupling flatness and directivity. Furthermore, the sum of the electrical lengths of all coupling branches 421 only needs to satisfy 1 / 4 of the operating wavelength; different combinations of lengths can meet the requirements of different operating frequency bands.

[0046] Please see Figure 2 and Figure 3 In one embodiment, the first main body 42 is configured as a symmetrical structure to improve performance; of course, it can also be configured as an asymmetrical structure.

[0047] Please see Figure 2 and Figure 3 In one embodiment, a coupling branch 421 located in the middle is configured as a U-shaped branch 422. Thus, at least one coupling branch 421 is provided on each of the opposite sides of the U-shaped branch 422. Furthermore, by configuring the coupling branch 421 in the middle as a U-shaped branch 422, the distance between the opposite ends of the first main body 42 can be reduced, the coupling isolation can be increased, and the directivity and bandwidth can be improved.

[0048] Please see Figure 2 and Figure 3 In one embodiment, each coupling stub 421 has a different characteristic impedance, that is, the coupling stub 421 is designed as a discontinuous impedance, which improves the performance of the microstrip coupler.

[0049] Please see Figure 2 and Figure 3 In one embodiment, the characteristic impedance of each coupling stub 421 between the coupling end 41 and the U-shaped stub 422 increases in the direction from the coupling end 41 to the isolation end 43. Thus, the width of each coupling stub 421 between the coupling end 41 and the U-shaped stub 422 decreases, and the coupling stub 421 is designed with discontinuous impedance, which improves the in-band coupling flatness and the directivity of the coupling line 40.

[0050] Please see Figure 2 and Figure 3 In one embodiment, the characteristic impedance of each coupling stub 421 between the U-shaped stub 422 and the isolation end 43 decreases in the direction from the coupling end 41 to the isolation end 43. Thus, the width of each coupling stub 421 between the coupling end 41 and the U-shaped stub 422 increases, and the coupling stub 421 is designed with discontinuous impedance, which improves the in-band coupling flatness and the directivity of the coupling line 40.

[0051] Please see Figure 2 and Figure 3 In one embodiment, each coupling stub 421 between the coupling end 41 and the U-shaped stub 422, and each coupling stub 421 between the U-shaped stub 422 and the isolation end 43, is rectangular in shape, and each of its edges facing away from the signal line 70 is aligned with each other and arranged on the same straight line. In this way, the lower edges of each coupling stub 421 other than the U-shaped stub 422 on the first main body 42 are aligned with each other, improving the continuity of the characteristic impedance changes of each continuous stub.

[0052] Please see Figures 2 to 4, in a specific embodiment, there are seven coupling branches 421 on the first main body portion 42, the fourth coupling branch 421 is configured as a U-shaped branch 422, and the remaining six coupling branches 421 are configured in a rectangular shape. The sum of the electrical lengths of all the coupling branches 421 of the first main body portion 42 should be approximately equal to 1 / 4 of the operating wavelength, for example, in [λ min / 4, λ max / 4], each coupling branch 421 has its own length and width. Wherein, the widths of the six coupling branches 421 are respectively set as W1, W2, W3, W4, W5 and W6, wherein W1>W2>W3, W4<W5<W6, and the width of the coupling branch 421 is, for example, 0.2mm to 2.2mm; in addition, the lengths of the six coupling branches 421 are respectively set as L1, L2, L3, L4, L5 and L6, and the lengths of the respective coupling branches 421 are not significantly different. In this case, the respective coupling branches 421 have different characteristic impedances, which can increase the adjustment flexibility of directivity and further improve the directivity.

[0053] Refer to Figures 2 to 4 , in one embodiment, the U-shaped branch 422 comprises two first connecting arms 4221 arranged at an opposite interval and a second connecting arm 4222 respectively connected to the two first connecting arms 4221. The characteristic impedance of the second connecting arm 4222 is smaller than that of the first connecting arms 4221.

[0054] Wherein, the main design parameters of the U-shaped branch 422 include the width Wu of the first connecting arms 4221, the length Lu of the second connecting arm 4222 and the spacing between the two first connecting arms 4221, which affect the frequency response and directivity of the coupling line 40. The directivity of the coupling line 40 can be adjusted accordingly by adjusting the widths and lengths of the first connecting arms 4221 and the second connecting arm 4222.

[0055] Wherein, the characteristic impedance of the two first connecting arms 4221 is set to 50 ohms. The width of the first connecting arms 4221 is equal to the strip line width of the input end 71 and the output end 73.

[0056] Refer to Figures 2 to 4 , in one embodiment, the width and length of the second connecting arm 4222 need to be adjusted to obtain optimal directivity, where Lu<L1+L2+L3, for example, Lu≈2*L3. After Lu is determined, L1, W1, L2, W2, L3 and W3 can be adjusted sequentially to finely tune the directivity. The fine tuning idea is to first confirm the return loss of the four ports, optimize the return loss of each port to the optimal level, then determine the central optimal frequency point of the directivity: if the frequency point shifts to higher frequency, L1, L2 and L3 are sequentially reduced and shortened, and W1, W2 and W3 are widened; otherwise, adjustment is performed in the opposite direction.

[0057] In one embodiment, the coupling degree of the microstrip coupler is mainly determined by D1, D2, and H. The coupling degree can be adjusted by increasing or decreasing D1, D2, and H.

[0058] Please see Figures 2 to 4 In one embodiment, the width of the first connecting arm 4221 is set to Wu, and the length of the coupling end 41 is set to L. O The length of the isolation end 43 is set to L. G L O ≥2Wu, L G ≥2Wu.

[0059] The widths of coupling end 41 and isolation end 43 are calculated based on the dielectric layer parameters of the upper and lower layers of coupling line 40. For example, the upper dielectric layer may be a 20mil RO4350 substrate, and the two lower dielectric layers may be 3.66mil ± 0.3mil and 5.12mil ± 0.5mil FR4 substrates respectively. The width of coupling end 41 is set to W. O The width of the isolation end 43 is set to W. G W O With W G Each is independently set to 0.2mm to 1.2mm.

[0060] In some embodiments, the different layers of signal line 70 and coupling line 40 are not limited to two dielectric layers, but can be applied to multilayer PCBs and castle structures. For castle structures, signal line 70 is generally on the top dielectric layer, and coupling line 40 is on other layers besides the top layer.

[0061] Please see Figures 1 to 3 In one embodiment, the first dielectric layer 20 includes a first split layer 21 and a second split layer 22. The microstrip coupler also includes a fourth ground layer 80, and the first ground layer 10, the first split layer 21, the fourth ground layer 80, the second split layer 22, the second ground layer 30, the second dielectric layer 50, and the third ground layer 60 are sequentially disposed. The fourth ground layer 80 is provided with a third cutout area 81 corresponding to the first cutout area 31.

[0062] In one embodiment, the thicknesses of the first split layer 21, the second split layer 22, and the second dielectric layer 50 are independently set to 2mil to 40mil.

[0063] Example 1

[0064] Design a 30dB microstrip coupler for 3900MHz to 4900MHz, with a directivity requirement of >25dB.

[0065] The second dielectric layer 50 uses an R04350B substrate with a thickness of 20mil±2mil and an equivalent dielectric constant of 3.66±0.3. The first split layer 21 uses an FR4 material with a thickness of 3.66mil±0.3mil and an equivalent dielectric constant of 4.4±0.4. The second split layer 22 uses an FR4 substrate with a thickness of 5.12mil±0.5mil and an equivalent dielectric constant of 4.4±0.4.

[0066] First, determine Lu. To support the 3900-4900MHz frequency band, Lu is set to 7.3mm to 9.2mm, specifically, 8mm is selected.

[0067] Since the height of H is already determined by the thickness of the board, H = 20mil, then D1 and D2 are adjusted to determine the coupling at the center frequency point as -30dB. At this time, D1 = D2 = 1.03mm.

[0068] The lengths of L1, L2, L3, L4, L5, and L6 can be determined based on 1 / 4 of the working wavelength. Considering that the coupling line 40 is composed of 7 coupling stubs 421, we can initially confirm that L1 = L6 = 1.2mm, L2 = L5 = 1.1mm, L3 = L4 = 1.1mm, and Lu = 1.2mm. Then, we set the stepped impedance. The characteristic impedance of the coupling stub 421 should conform to the direction of directional optimization. According to the principle of reflection superposition and cancellation, the signal flowing into the isolation terminal 43 on the coupling line 40 passes through the stepped impedance line, so that the directionality is optimal. Therefore, W1≈3W2≈5W3, and the impedance Z1≈0.5Z2≈0.35Z3 is initially set as W1 = W6 = 1.02mm, W2 = W5 = 0.35mm, W3 = W4 = 0.2mm, WO = WG = 0.26mm, and WU = 1.05mm, thus obtaining the preliminary dimensions of the coupling line 40.

[0069] Finally, based on the principles of coupling degree and directionality adjustment, the length and width of each coupling branch 421 of the 40 segments of the coupling line are finely adjusted to obtain the coupler A.

[0070]

[0071] In one embodiment, a circuit board is provided, which is configured as a multilayer circuit board or as a component of a multilayer circuit board, including but not limited to a double-layer circuit board. The circuit board includes a microstrip coupler as described in any of the above embodiments.

[0072] In the aforementioned circuit board, the coupling line 40 and the signal line 70 are arranged on different dielectric layers. The first projection and the second cutout area 61 do not overlap at all, and the second projection and the first cutout area 31 do not overlap at all. In this way, on the one hand, the first ground layer 10, the second ground layer 30 and the third ground layer 60 cooperate to form a metal shielding cavity for the coupling line 40, avoiding mutual interference between the coupling line 40 and the external electromagnetic environment. This eliminates the need for a separate cavity on the signal line 70 as in related technologies, allowing for a reduction in the product size of the microstrip coupler and achieving miniaturization. It also reduces the length of the output terminal 73 and the input terminal 71 of the signal line 70, thereby reducing insertion loss and improving the output efficiency of the power amplifier. On the other hand, because the coupling line 40 and the signal line 70 are arranged on different layers, the coupling energy transmission between them is along the vertical direction, not along the horizontal direction as in related technologies. This prevents the coupling line 40 from interfering with other devices located on both sides of the signal line 70, ensuring normal and stable signal transmission. In addition, the reduced product board area facilitates the arrangement of other devices.

[0073] In one embodiment, the number of microstrip couplers integrated on the circuit board can be one or two. When the circuit board includes multiple microstrip couplers, it is possible to couple multiple radio frequency signals of different frequency bands for detecting power information of multiple radio frequency signals of different frequency bands.

[0074] In one embodiment, a communication device includes the microstrip coupler of any of the above embodiments. The communication device can be a handheld device, an in-vehicle device, a wearable device, a computing device, or other processing device connected to a wireless modem, as well as various forms of user equipment (UE) (e.g., mobile phone), mobile station (MS), etc. For ease of description, the devices mentioned above are collectively referred to as communication devices. Network devices may include base stations, access points, etc.

[0075] In the aforementioned communication device, the coupling line 40 and the signal line 70 are arranged on different dielectric layers. The first projection and the second cutout area 61 do not overlap at all, and the second projection and the first cutout area 31 do not overlap at all. In this way, on the one hand, the first ground layer 10, the second ground layer 30 and the third ground layer 60 cooperate to form a metal shielding cavity for the coupling line 40, avoiding mutual interference between the coupling line 40 and the external electromagnetic environment. This eliminates the need for a separate cavity on the signal line 70 as in related technologies, thereby reducing the product size of the microstrip coupler and achieving miniaturization. It also reduces the length of the output end 73 and the input end 71 of the signal line 70, thereby reducing insertion loss and improving the output efficiency of the power amplifier. On the other hand, because the coupling line 40 and the signal line 70 are arranged on different layers, the coupling energy transmission between them is along the vertical direction, not along the horizontal direction as in related technologies. This prevents the coupling line 40 from interfering with other devices located on both sides of the signal line 70, ensuring normal and stable signal transmission. In addition, the reduced product board area is beneficial for the arrangement of other devices.

[0076] In the description of this application, it should be understood that if terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" appear, these terms indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0077] Furthermore, where the terms "first" and "second" appear, these terms are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, where the term "multiple" appears, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0078] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0079] In this application, unless otherwise expressly specified and limited, the use of descriptions such as "above" or "below" the second feature indicates that the first and second features are in direct contact or indirect contact via an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. Similarly, "below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0080] It should be noted that if an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. If an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. If so, the terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used in this application are for illustrative purposes only and do not represent the only possible implementation.

[0081] The technical features of the above embodiments can be combined in any way. For the sake of brevity, 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.

[0082] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A microstrip coupler, characterized in that, The microstrip coupler includes: First grounding layer; A first dielectric layer is disposed on the first ground layer; The second grounding layer is disposed on the first dielectric layer on a side opposite to the first grounding layer, and the second grounding layer is provided with a first hollow area; The coupling line is located on the same layer as the second ground layer and is disposed on the first dielectric layer at a location corresponding to the first hollow area; The second dielectric layer is disposed on the second ground layer; A third grounding layer, wherein the third grounding layer is disposed on the second dielectric layer on a side opposite to the second grounding layer, and the third grounding layer has a second hollow area; and The signal line is located on the same layer as the third ground layer and is disposed on the second dielectric layer at a location corresponding to the second cutout area; Wherein, the first projection of the coupling line on the third ground layer along the direction perpendicular to the third ground layer does not overlap with the second hollow area, and the second projection of the signal line on the second ground layer along the direction perpendicular to the second ground layer does not overlap with the first hollow area; the coupling line includes a coupling end, a first main body, and an isolation end connected in sequence; the signal line includes an input end, a second main body, and an output end connected in sequence; the input end and the coupling end are located on the same side, the second main body and the first main body are corresponding in position and coupled to each other, and the output end and the isolation end are located on the same side.

2. The microstrip coupler according to claim 1, characterized in that, The horizontal distances between the branches at both ends of the first main body and the signal line are set as D1 and D2, respectively, and the vertical distance between the signal line and the coupling line is set as H. D1 and D2 are each independently set to 0.2mm~1.2mm, and H is set to 4mil~40mil.

3. The microstrip coupler according to claim 1, characterized in that, The first main body includes a plurality of coupled branches connected in series.

4. The microstrip coupler according to claim 3, characterized in that, One of the coupled branches located in the middle position is designated as a U-shaped branch.

5. The microstrip coupler according to claim 4, characterized in that, The characteristic impedance of each of the coupling stubs between the coupling end and the U-shaped stub tends to increase in the direction from the coupling end to the isolation end; The characteristic impedance of each of the coupling stubs between the U-shaped stub and the isolation end tends to decrease in the direction from the coupling end to the isolation end.

6. The microstrip coupler according to claim 5, characterized in that, Each of the coupling branches between the coupling end and the U-shaped branch, and each of the coupling branches between the U-shaped branch and the isolation end, is rectangular in shape, and each of them is aligned with each other on the side edge away from the signal line and arranged on the same straight line.

7. The microstrip coupler according to claim 4, characterized in that, The U-shaped branch includes two first connecting arms that are spaced apart from each other and a second connecting arm that is connected to the two first connecting arms respectively; the characteristic impedance of the second connecting arm is less than the characteristic impedance of the first connecting arm.

8. The microstrip coupler according to claim 7, characterized in that, The width of the first connecting arm is set to Wu, and the length of the coupling end is set to L. O The length of the isolation end is set to L. G L O ≥2Wu, L G ≥2Wu.

9. The microstrip coupler according to any one of claims 1 to 8, characterized in that, The first dielectric layer includes a first split layer and a second split layer. The microstrip coupler also includes a fourth ground layer. The first ground layer, the first split layer, the fourth ground layer, the second split layer, the second ground layer, the second dielectric layer, and the third ground layer are arranged in sequence. The fourth ground layer is provided with a third hollow area corresponding to the first hollow area.

10. A circuit board, characterized in that, The circuit board includes a microstrip coupler as described in any one of claims 1 to 9.

11. A communication device, characterized in that, The communication device includes a microstrip coupler as described in any one of claims 1 to 9.

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