Embedded multimode coupler, radio frequency module and communication equipment

Abstract

The embodiment of the present application provides an embedded multimode coupler, a radio frequency module and a communication device, wherein the embedded multimode coupler includes a substrate, the substrate includes a stacked first layer and a second layer, the first layer is provided with an input port, a straight-through port and a main line conductor, the second layer is provided with a coupling port, an isolation port and a secondary line conductor, the input port and the straight-through port are respectively connected to the two ends of the main line conductor, the coupling port and the isolation port are respectively connected to the two ends of the secondary line conductor, wherein the secondary line conductor includes a convex structure, the length extension direction of the top of the convex structure is consistent with the length extension direction of the main line conductor, and the top overlaps with the main line conductor in a top-down view. The embedded multimode coupler of the present application has the characteristics of high directivity, wide frequency response, small size, low insertion loss in the multi-frequency passband and good frequency response flatness.

Description

Technical Field

[0001] The present application relates to the field of coupler technology, and in particular to an embedded multi-mode coupler, a radio frequency module and a communication device. Background Art

[0002] With the continuous development of WIFI technology and broadband wireless communication technology, new modulation methods (such as QAM, QPSK) are used to improve spectrum utilization, which places high demands on the linear performance of power amplifiers. RF closed-loop systems, as linearization technology loop systems, especially couplers, as important components of closed-loop feedback, require higher performance requirements. However, current coupler technology often has problems with directivity, broadband response, and flatness within the frequency response band. Sometimes, in order to solve the above problems, it is necessary to increase design costs. Summary of the invention

[0003] In view of this, the purpose of the present application is to overcome the deficiencies in the prior art and to provide an embedded multi-mode coupler, a radio frequency module and a communication device.

[0004] An embodiment of the present application provides an embedded multimode coupler, including a substrate, wherein the substrate includes a first layer and a second layer stacked together, the first layer is provided with an input port, a through port and a main line conductor, the second layer is provided with a coupling port, an isolation port and a secondary line conductor, the input port and the through port are respectively connected to two ends of the main line conductor, the coupling port and the isolation port are respectively connected to two ends of the secondary line conductor, wherein the secondary line conductor includes a convex structure, the length extension direction of the top of the convex structure is consistent with the length extension direction of the main line conductor, and the top overlaps with the main line conductor in a top-down view.

[0005] In one embodiment, the lengths of the main conductor and the secondary conductor are equal and are set to be one quarter of the wavelength of the center frequency of the working frequency band.

[0006] In one embodiment, the embedded multimode coupler further includes: the length of the main line conductor and the secondary line conductor is a quarter wavelength of the center frequency of the lowest working frequency band among multiple available working frequency bands.

[0007] In one embodiment, the embedded multimode coupler further comprises: in a top view, the distances from the top of the convex structure to the two ends of the main line conductor are equal.

[0008] In one embodiment, the input port and the through port are respectively used to connect a load matching the characteristic impedance of the main line conductor.

[0009] In one embodiment, the embedded multimode coupler further includes: coupling capacitors located at the first layer, the input port and the through port are respectively connected to corresponding coupling capacitors, and each coupling capacitor is used to connect to an external object.

[0010] In one embodiment, the coupled port and the isolated port are respectively connected to a 50-ohm matched load through corresponding blind holes.

[0011] In one embodiment, the embedded multimode coupler further includes: a matching microstrip line located in the first layer, the coupling port and the isolation port are respectively connected to the corresponding matching microstrip line through corresponding blind holes, and each matching microstrip line is used to connect to an external object. Further, the matching microstrip line adopts a microstrip transmission line with a characteristic impedance of 50 ohms.

[0012] In one embodiment, the main line conductor is a microstrip line, and the secondary line conductor is a stripline.

[0013] In one embodiment, the substrate further includes a third layer stacked with the second layer, and the third layer is provided with a reference ground terminal corresponding to the microstrip line.

[0014] Another embodiment of the present application provides a radio frequency module, including the above-mentioned embedded multi-mode coupler.

[0015] Yet another embodiment of the present application provides a communication device, comprising the above-mentioned radio frequency module.

[0016] The embodiments of the present application have the following advantages:

[0017] The embedded multimode coupler of the present application is realized by overlapping the secondary conductor and the main conductor microstrip line in parallel, and the secondary conductor adopts a rotationally coupled main conductor design. The embedded multimode coupler not only has low insertion loss and good frequency response flatness in the multi-frequency passband, has good frequency response selectivity, but also has the characteristics of good directivity, wide frequency response and small size. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 A schematic structural diagram of an embedded multimode coupler according to an embodiment of the present application is shown;

[0020] Figure 2An equivalent circuit diagram of the embedded multimode coupler according to an embodiment of the present application is shown;

[0021] Figure 3 A schematic diagram showing an application of the embedded multimode coupler of an embodiment of the present application for a directional coupler;

[0022] Figure 4 A schematic diagram of a multi-layer stacked structure of an embedded multimode coupler according to an embodiment of the present application is shown;

[0023] Figure 5a-Figure 5i An S-parameter simulation diagram of the embedded multimode coupler according to an embodiment of the present application is shown. DETAILED DESCRIPTION

[0024] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application.

[0025] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. In contrast, when an element is referred to as being "directly on" another element, there is no intermediate element. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0026] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0027] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of the template are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0029] Please refer to Figure 1 This embodiment proposes a multimode coupler, which adopts an embedded structure design and can be applied to radio frequency communication systems and products, etc. The coupler can improve the large fluctuation of the feedback signal in the passband, maximize the linearity of the output radio frequency signal, and thus improve the quality of the whole system, etc. The embedded multimode coupler is described in detail below.

[0030] In this embodiment, the embedded multimode coupler is a four-port network, which is located on different layers of the substrate. Figure 1 As shown, the multimode coupler includes a substrate, which includes a first layer and a second layer stacked, wherein the first layer is provided with an input port P1, a through port P2 and a main line conductor, and the second layer is provided with a coupling port P3, an isolation port P4 and a secondary line conductor. On the first layer, the input port P1 and the through port P2 are respectively connected to the two ends of the main line conductor. On the second layer, the coupling port P3 and the isolation port P4 are respectively connected to the two ends of the secondary line conductor.

[0031] Different from the traditional parallel coupling design, this coupler sets the secondary conductor and the main conductor in different layers. Usually, the layer where the main conductor is located is the top layer, and the secondary conductor is located in the second layer below the top layer. Relative to the top layer, the secondary conductor is an embedded structure, so it is called an embedded multimode coupler. When the coupling port P3 and the isolation port P4 are needed, the two ports of the second layer can be led to the top layer of the substrate by using blind holes, or they can be led to other layers below by using buried holes.

[0032] In this embodiment, the secondary conductor will adopt a bent structure to form a new overlapping parallel coupling structure with the main conductor. Figure 1As shown, the secondary line conductor includes a convex structure, the length extension direction of the top of the convex structure is consistent with the length extension direction of the main line conductor, and the top overlaps with the main line conductor in a top-down view. The main line conductor adopts a microstrip line, and the secondary line conductor adopts a stripline. Usually, the main line conductor adopts a straight microstrip line structure, and its length extension direction is the connection direction of the input port P1 and the straight-through port P2, while the length extension direction of the top of the convex structure is the same as the connection direction of the input port P1 and the straight-through port P2, that is, the top of the convex structure of the main line conductor and the secondary line conductor is parallel. Furthermore, the upper left corner and the upper right corner of the second conductor segment and the turning point of the third conductor segment all adopt a cut-angle structure design.

[0033] In one embodiment, the secondary conductor comprises a convex structure, such as Figure 1 As shown, the convex structure includes a first conductor segment, a second conductor segment, and a third conductor segment connected in sequence, wherein the second conductor segment is located between the first conductor segment and the third conductor segment, the first conductor segment and the third conductor segment are mirror-symmetrical along the center line of the second conductor segment, the other end of the first conductor segment is provided with a coupling port P3, and the other end of the third conductor segment is provided with an isolation port P4. It should be understood that the division of the second conductor segment is not limited to the middle line segment area at the top of the convex structure, and in some other embodiments, it can also include a partial area of ​​two vertical line segments at 90 degrees to the middle line segment, etc., which also has the mirror-symmetrical characteristics.

[0034] It can be understood that by designing the microstrip line of the secondary conductor and the main conductor to overlap in parallel and increase the coupling capacitance between the two, that is, increasing the capacitance at both ends of the coupling, the difference in phase velocity between the even mode and the odd mode of the microstrip line can be compensated, so that the phase velocity of the odd mode and the even mode become the same, thereby achieving the purpose of increasing directivity and solving the problem of flatness of multi-frequency response. The secondary conductor forms a rotating coupling structure with the main conductor by adopting a bending design, which can not only keep the amplitude-frequency characteristics of the output end flat within the band and obtain good frequency response selectivity, but also form an angle with the main conductor. The secondary conductor adopts a rotating structure, and there is a discontinuity at the connection between them, so that the signal reflected by the coupling port P3 is the same as the signal transmitted from the input port P1 to the isolation port P4, and the phase is opposite, which can eliminate the port power, thereby improving the directivity and the frequency response is also greatly improved.

[0035] Furthermore, the embedded multimode coupler also includes: in a top view, the distance from the top of the convex structure to the two ends of the main line conductor is equal, that is, the convex structure overlaps with the center of the main line conductor and is symmetrically distributed at both ends of its center, which can further improve the coupling coefficient, etc.

[0036] In this embodiment, the lengths of the main conductor and the secondary conductor are equal and are set to a quarter wavelength of the center frequency of the operating frequency band. Exemplarily, if the embedded multimode coupler is used as a directional coupler, for example, its operating frequency band is 2412-2482 MHz, then the lengths of the main conductor and the secondary conductor can be set to a quarter wavelength corresponding to the center frequency of 2412-2482 MHz. It can be understood that the so-called multimode means that the coupler can be applied to multiple operating frequencies in the designed operating frequency band.

[0037] Furthermore, if the coupler is applicable to multiple operating frequency bands, the length of the main conductor and the auxiliary conductor is set to be a quarter wavelength of the center frequency of the lowest operating frequency band among the multiple available operating frequency bands. For example, if the design frequency is 2412-2482 MHz and 5180-5850 MHz, the length of the coupler will be a quarter wavelength of the center frequency of the 2412-2482 MHz frequency band.

[0038] It can be understood that when the length of the coupler is one quarter of the wavelength of the working signal, the phase difference between the through port P2 and the coupled port P3 is close to 90 degrees, thereby improving the isolation between the input port P1 and the isolated port P4. In addition, the power of the signal coupled to the coupled port P3 will be maximized, and the coupler at this time not only has a smaller size, but also has a lower transmission loss.

[0039] Exemplarily, the input port P1 and the through port P2 are used to connect to a load that matches the characteristic impedance of the main line conductor. For example, a load with a characteristic impedance of 50 ohms can be directly connected. Of course, in some other embodiments, the embedded multimode coupler further includes: a coupling capacitor located on the first layer, the input port P1 and the through port P2 are respectively connected to the corresponding coupling capacitors, and then each coupling capacitor is used to connect to other components and other external objects. Figure 2 The equivalent circuit of an embedded multimode coupler is shown. Inductor L1 is the equivalent inductance of the main conductor microstrip line, inductor L2 is the equivalent inductance of the secondary conductor microstrip line, capacitor C4 and capacitor C3 are the equivalent coupling capacitors of the main conductor and the secondary conductor, capacitor C1 and capacitor C2 are the equivalent parasitic capacitors of the main conductor and the reference ground, capacitor C5 and capacitor C6 are the equivalent parasitic capacitors of the secondary conductor and the reference ground. TL1, TL2, TL3 and TL4 represent the characteristic impedance 50 ohm microstrip lines connected to the ports of the coupler.

[0040] Further, the coupling port P3 and the isolation port P4 can be used to connect some compensation elements. Exemplarily, the coupling port P3 and the isolation port P4 of the embedded multimode coupler are respectively used to connect impedance-matched loads through corresponding blind holes. For example, a load with an impedance of 50 ohms can be directly connected. Among them, the parasitic capacitance generated by the blind hole can be used to compensate for the parasitic reactance generated when the rotating coupling microstrip is used, thereby improving the return loss of the port.

[0041] Alternatively, in some other embodiments, the embedded multimode coupler further includes: a matching microstrip line located on the first layer, the coupling port P3 and the isolation port P4 are respectively connected to the corresponding matching microstrip line through corresponding blind holes, and each matching microstrip line is used to connect to an external object. For example, the matching microstrip line can be a microstrip line with a characteristic impedance of 50 ohms. For example, Figure 3 The schematic diagram of an application of a directional coupler is shown, wherein both ends of the main conductor and the secondary conductor can be connected to an equivalent load Z0 with a characteristic impedance of 50 ohms.

[0042] It can be understood that the reserved component compensation of the coupling port P3 and the isolation port P4 can be used to adjust the reflection coefficient of the isolation port P4, so as to change the amplitude and phase of the reflected signal of the isolation port P4, thereby achieving a phase opposite to the signal of the input port P1, and achieving a power cancellation effect. On the other hand, by utilizing the slope relationship between the modulus value of the impedance of the resonant circuit and the coupler frequency, by selecting a suitable circuit topology structure, the modulus of the impedance is monotonically decreased when it deviates from the resonant frequency point, so that the amplitude-frequency characteristics of the output end of the directional coupler remain flat within the band and the bandwidth is expanded, further achieving the consistency and stability of the microstrip line.

[0043] In actual use, the embedded multimode coupler is usually designed as a multi-layer structure. For example, if the embedded multimode coupler is a three-layer structure, the substrate may also include a third layer stacked with the second layer, for example, the third layer is provided with a reference ground corresponding to the microstrip line, etc. For another example, if the embedded multimode coupler is a four-layer structure, for example, the substrate may also include a fourth layer stacked with the third layer, for example, the fourth layer may be provided with a power ground, etc. In one embodiment, Figure 4 As shown, the first layer D1 is the main conductor layer, the second layer D2 is the secondary conductor layer, the third layer D3 is the microstrip line reference layer, and the fourth layer D4 is the power layer. It can be understood that the above-mentioned microstrip line reference layer and power layer are only examples. For couplers with three or more layers, the structural design of the third layer and above can be set according to actual needs.

[0044] Take an embedded multimode coupler with a four-layer structure as an example. The two working frequency bands of the coupler are 2412-2482MHz and 5180-5850MHz. The substrate is a commonly used FR-4 grade copper-clad epoxy glass fiber cloth laminate, with a relative dielectric constant εr = 4.5 and a dielectric loss of 0.022. By forming the above-mentioned embedded multimode coupler on the substrate, the actual size of the coupler is only 1.2x0.5mm, which is nearly 20% smaller than the size of the traditional coupler. Figure 5a-Figure 5i The simulation test curves of multiple S parameters of a coupler are shown, wherein the horizontal axis represents the signal frequency of the tuned coupler, the vertical axis of each curve represents different amplitudes or phases, and each m point on the curve is a frequency test point. Figure 5a S(1,1) in), S22 (corresponding to Figure 5b S(2,2) in), S33 (corresponding to Figure 5c S(3,3)) and S44 (corresponding to Figure 5d The S(4,4) in the figure represent the impedance matching performance parameters of the ports P1, P2, P3 and P4 of the embedded multimode coupler respectively; S21 (corresponding to Figure 5e S(2,1)) in the figure represents the insertion loss of the embedded multimode coupler; S31 (corresponding to Figure 5f S(3,1) in the figure represents the coupling degree of the embedded multimode coupler; S41 (corresponding to Figure 5g S(4,1)) in the figure represents the isolation of the embedded multimode coupler; Figure 5h The D in represents the directivity of the embedded multimode coupler; Figure 5i The ratio in the equation represents the phase difference between the through port and the coupled port of the embedded multimode coupler. Figures 5a to 5i From the simulation test curve shown, it can be seen that the coupler has high directivity and good frequency response selectivity, the amplitude-frequency characteristics of its output end remain flat and wide frequency response within the band, and the transmission loss is small.

[0045] The embedded multimode coupler proposed in this embodiment is designed to overlap the secondary conductor and the main conductor microstrip line in parallel to increase the coupling capacitance between the two, which can effectively solve the directivity and multi-frequency response flatness problems of the coupler, and can also obtain a wider coupling coefficient to solve the disadvantage of difficult process in the traditional parallel coupling method to make the coupling coefficient strong; and the secondary conductor adopts a rotationally coupled main conductor microstrip line design, that is, it forms an angle with the main conductor, which can keep the amplitude-frequency characteristics of the output end flat within the band, and obtain a wider frequency response selectivity, thereby improving the frequency response amplitude of the feedback signal within the passband, greatly improving the linearity of the radio frequency system and the system communication quality.

[0046] The present application also proposes a radio frequency module, which exemplarily includes the embedded multimode coupler in the above-mentioned embodiment 1. In wireless communication products, the embedded multimode coupler has the characteristics of wide frequency response, low insertion loss, good multi-frequency selectivity, good flatness in the passband, high isolation and good directivity. In addition, due to the embedded bending structure design, the volume of the entire coupler is small, which reduces the cost.

[0047] The present application also proposes a communication device, such as a wireless telephone, a mobile phone, etc. Exemplarily, the communication device includes the above-mentioned radio frequency module, wherein the radio frequency module includes an embedded multimode coupler. By using the above-mentioned embedded multimode coupler structure, the problems of the traditional parallel coupler can be solved, and the signal linearization can be maximized in the application of the radio frequency closed-loop system, thereby improving the signal quality of the whole system.

[0048] In all examples shown and described herein, any specific values ​​should be interpreted as merely exemplary and not as limiting, and thus other examples of the exemplary embodiments may have different values.

[0049] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0050] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application.

Claims

1. An embedded multimode coupler, characterized in that: The invention comprises a substrate, wherein the substrate comprises a first layer and a second layer stacked, wherein the first layer is provided with an input port, a through port and a main line conductor, and the second layer is provided with a coupling port, an isolation port and a secondary line conductor, wherein the input port and the through port are respectively connected to two ends of the main line conductor, and the coupling port and the isolation port are respectively connected to two ends of the secondary line conductor, wherein the secondary line conductor comprises a convex structure, wherein the length extension direction of the top of the convex structure is consistent with the length extension direction of the main line conductor, the top overlaps with the main line conductor in a top view, the secondary line conductor forms a rotation coupling structure with the main line conductor by adopting a bending design, the main line conductor is a microstrip line, and the secondary line conductor is a strip line; The lengths of the main conductor and the secondary conductor are equal and are set to a quarter of the wavelength of the center frequency of the working frequency band; It also includes: the length of the main line conductor and the secondary line conductor is a quarter of the wavelength of the center frequency point of the lowest working frequency band among multiple available working frequency bands.

2. The embedded multimode coupler according to claim 1, characterized in that: Also includes: In a top view, the distances from the top of the convex structure to the two ends of the main conductor are equal.

3. The embedded multimode coupler according to claim 1, characterized in that: Also includes: The coupling capacitors located at the first layer, the input port and the through port are respectively connected to the corresponding coupling capacitors, and each coupling capacitor is used to connect to an external object.

4. The embedded multimode coupler according to claim 1 or 3, characterized in that: Also includes: The matching microstrip line located in the first layer, the coupling port and the isolation port are respectively connected to the corresponding matching microstrip line through corresponding blind holes, and each matching microstrip line is used to connect to an external object.

5. The embedded multimode coupler according to claim 1, characterized in that: The substrate further includes a third layer stacked with the second layer, and the third layer is provided with a reference ground end corresponding to the microstrip line.

6. A radio frequency module, characterized in that: The method comprises the embedded multimode coupler as claimed in any one of claims 1 to 5.

7. A communication device, characterized in that: Includes the radio frequency module described in claim 6.

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