Microwave directional coupler based on multilayer circuit board

Abstract

The present invention provides a microwave directional coupler based on a multi-layer circuit board, comprising: a first port, a second port, a third port and a fourth port; a main transmission line, wherein the main transmission line is configured between the first port and the second port; and a coupling transmission line, wherein the coupling transmission line is configured between the third port and the fourth port, wherein the main transmission line and the coupling transmission line are formed by transmission lines arranged in 2N different metal layers, N being a natural number greater than 1, wherein the main transmission line is formed by connecting in parallel transmission lines configured in odd-numbered metal layers, and the coupling transmission line is formed by connecting in parallel transmission lines configured in even-numbered metal layers.

Description

Technical Field

[0001] The present invention relates to the field of microwave and wireless communication, and more particularly to a microwave directional coupler based on a multi-layer circuit board for microwave and wireless communication. Background Art

[0002] In microwave, radar and communication systems, it is necessary to distribute, synthesize, sample and detect the power of the transmission signal. Microwave directional coupler is a directional power distribution device that can divide a part of the power from the forward wave of the transmission line system in a certain proportion to achieve power branching, distribution or reverse synthesis.

[0003] The 3dB directional coupler is a special directional coupler, which is widely used in amplifier power synthesis and power distribution. It is an important component of balanced power amplifiers, analog and digital shifters.

[0004] Generally speaking, the on-chip 3dB directional coupler is a four-port component, which includes an input port, a through port, a coupled port, and an isolated port. Its main performance technical indicators include: operating frequency range, input / output voltage standing wave ratio, insertion loss, isolation, coupling, amplitude balance, phase balance, etc., as well as temperature stability, area, reliability, cost and other design requirements. Summary of the invention

[0005] This patent proposes a microwave directional coupler based on an on-chip multi-layer circuit board. By using transmission lines arranged in multiple metal layers to configure the main transmission line and the coupling transmission line, the microwave directional coupler has better parameter performance, occupies a small area, and can greatly reduce the minimum packaging area of ​​the module, providing a good solution for handheld devices and wearable devices.

[0006] According to an embodiment of the present invention, there is provided a microwave directional coupler based on a multilayer circuit board, comprising: a first port, a second port, a third port and a fourth port; a main transmission line, the main transmission line being configured between the first port and the second port; a coupled transmission line, the coupled transmission line being configured between the third port and the fourth port, wherein the main transmission line and the coupled transmission line are formed by transmission lines arranged in 2N different metal layers, N being a natural number greater than 1, wherein the main transmission line is formed by connecting in parallel transmission lines configured in odd-numbered metal layers, and the coupled transmission line is formed by connecting in parallel transmission lines configured in even-numbered metal layers.

[0007] According to an embodiment of the present invention, a microwave directional coupler based on a multi-layer circuit board is provided, wherein N=2, and wherein the main transmission line is formed by transmission lines configured in parallel on a first metal layer and a third metal layer, and wherein the coupled transmission line is formed by transmission lines configured in parallel on a second metal layer and a fourth metal layer.

[0008] According to an embodiment of the present invention, there is provided a microwave directional coupler based on a multi-layer circuit board, wherein the transmission lines arranged in 2N different metal layers are configured as a gyratory pattern.

[0009] According to an embodiment of the present invention, there is provided a microwave directional coupler based on a multi-layer circuit board, wherein the transmission line arranged in 2N different metal layers is configured as a microstrip line or a stripline.

[0010] According to an embodiment of the present invention, a microwave directional coupler based on a multi-layer circuit board is provided, wherein the transmission lines configured on odd-numbered metal layers are connected in parallel through a first through hole and a second through hole, and wherein the transmission lines configured on even-numbered metal layers are connected in parallel through a third through hole and a fourth through hole.

[0011] According to an embodiment of the present invention, a microwave directional coupler based on a multi-layer circuit board is provided, wherein the first through hole, the second through hole, the third through hole and the fourth through hole are located on the same side of the turn-shaped pattern.

[0012] According to an embodiment of the present invention, a microwave directional coupler based on a multi-layer circuit board is provided, wherein a first through hole, a second through hole, a third through hole and a fourth through hole are located at a center line of a turn-shaped pattern.

[0013] According to an embodiment of the present invention, a microwave directional coupler based on a multilayer circuit board is provided, further comprising a first ground plane and a second ground plane, wherein the first ground plane and the second ground plane are respectively arranged above and below the main transmission line and the coupling transmission line.

[0014] According to an embodiment of the present invention, a microwave directional coupler based on a multi-layer circuit board is provided, wherein the dielectric thickness L between metal layers is determined according to the number of metal layers 2N.

[0015] According to an embodiment of the present invention, a microwave directional coupler based on a multi-layer circuit board is provided, wherein the parasitic capacitance between transmission lines is adjusted by adjusting the positions of transmission lines arranged in 2N different metal layers in the horizontal direction or the vertical direction.

[0016] According to an embodiment of the present invention, a microwave directional coupler based on a multi-layer circuit board is provided, wherein the directional coupler has a bandwidth of 3.5 GHz-4.5 GHz. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic diagram showing the principle of a directional coupler;

[0018] Figure 2 is a schematic diagram showing a directional coupler of a single-layer circuit board;

[0019] Figure 3 is a schematic diagram showing a directional coupler of a double-layer circuit board;

[0020] Figure 4 is a schematic diagram showing a directional coupler of a multi-layer circuit board;

[0021] Figure 5 is a schematic diagram showing the transmission and coupling loss of a directional coupler of a multi-layer circuit board;

[0022] Figure 6 is a schematic diagram showing phase balance of a directional coupler of a multi-layer circuit board; and

[0023] Figure 7 is a schematic diagram showing the isolation of a directional coupler of a multi-layer circuit board. DETAILED DESCRIPTION

[0024] Before proceeding to the following detailed description, it may be advantageous to set forth the definitions of certain words and phrases used throughout this patent document. The terms "coupled", "connected" and their derivatives refer to any direct or indirect communication between two or more elements, whether or not those elements are in physical contact with each other. The terms "transmit", "receive" and "communication" and their derivatives cover direct and indirect communication. The terms "include" and "comprise" and their derivatives refer to including but not limited to. The term "or" is inclusive, meaning and / or. The phrase "associated with..." and its derivatives refer to including, including within, interconnecting, including, including within, connecting or connecting with, coupling or coupling with, communicating with, cooperating, interweaving, parallel, close to, binding or binding with, having, having attributes, having a relationship or having a relationship with, etc. The term "controller" refers to any device, system or part thereof that controls at least one operation. Such a controller can be implemented with hardware, or a combination of hardware and software and / or firmware. The functions associated with any particular controller can be centralized or distributed, whether local or remote. The phrase "at least one of", when used with a list of items, means that different combinations of one or more of the listed items may be used, and only one of the items in the list may be required. For example, "at least one of A, B, C" includes any of the following combinations: A, B, C, A and B, A and C, B and C, A and B and C.

[0025] Definitions for other specific words and phrases are provided throughout this patent document. Those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior and future uses of such defined words and phrases.

[0026] In this patent document, the application combination of circuit blocks and the division of sub-circuit blocks are only used for illustration, and the application combination of circuit blocks and the division of sub-circuit blocks may have different forms without departing from the scope of the present disclosure.

[0027] The following discussion Figures 1 to 7 The various embodiments used to describe the principles of the present disclosure in this patent document are for illustration only and should not be interpreted in any way as limiting the scope of the present disclosure. Those skilled in the art will appreciate that the principles of the present disclosure can be implemented in any appropriately arranged system or device.

[0028] Figure 1 is a schematic diagram showing the principle of a directional coupler.

[0029] See also Figure 1 A common directional coupler consists of two sections of transmission lines (a first transmission line and a second transmission line) that are close and parallel to each other, one of which is used as the main transmission line of the signal (for example, the first transmission line), and the other section (for example, the second transmission line) is used as the coupling line of the signal. The first transmission line and the second transmission line can be microstrip lines or strip lines. Specifically, Figure 1 As shown, the first transmission line includes port 1 (Port1), the first transmission line section TL1, the first coupled transmission line section CL1, the second transmission line section TL2 and port 2 (Port2); the second transmission line includes port 3 (Port3), the third transmission line section TL3, the second coupled transmission line section CL2, the fourth transmission line section TL4 and port 4 (Port4). For example, when a microwave signal is input from port 1 (Port1), port 2 (Port2) is a through port, port 3 (Port3) is a coupled port, and port 4 (Port4) is an isolated port.

[0030] Figure 2 is a schematic diagram showing a directional coupler of a single-layer circuit board.

[0031] exist Figure 2 In the directional coupler of the single-layer circuit board, the left-right coupling method is adopted. The first transmission line (TL1) and the second transmission line (TL2) are formed in the layer Metal2, and they are parallel to each other and configured in a rotating pattern. The number of layers required for the directional coupler of the single-layer circuit board is small, but due to the reasons of line width and spacing, it occupies a large area. At the same time, due to the different lengths of the two transmission lines, the various performances of the directional coupler of the single-layer circuit board are affected.

[0032] Figure 3 is a schematic diagram showing a directional coupler of a double-layer circuit board.

[0033] Figure 3 The directional coupler of the double-layer circuit board shown uses two parallel transmission lines of the same length. Specifically, the first transmission line (TL1) is formed in the layer Metal2 and is configured as a rotational pattern; the second transmission line (TL2) is formed in the layer Metal3 and is also configured as a rotational pattern. The four ports of the directional coupler of the double-layer circuit board are completely reciprocally equivalent, but due to the process limitations on the thickness of the dielectric between the upper and lower metal layers, the coupling degree cannot be effectively adjusted and cannot meet the design requirements. At the same time, the parasitic resistance of the transmission line affects the loss of the directional coupler.

[0034] Figure 4 is a schematic diagram showing a directional coupler of a multi-layer circuit board.

[0035] Figure 4 The directional coupler of the multi-layer circuit board shown in FIG. is realized by using a multi-layer high-frequency low-loss dielectric stacking process technology. Figure 4 As shown, the directional coupler of the multilayer circuit board includes four transmission lines, namely, a first transmission line (TL1), a second transmission line (TL2), a third transmission line (TL3) and a fourth transmission line (TL4). The first transmission line (TL1) is formed in the metal layer Metal 2 and is configured as a turn-shaped pattern; the second transmission line (TL2) is formed in the metal layer Metal 3 and is configured as a turn-shaped pattern; the third transmission line (TL3) is formed in the metal layer Metal 4 and is configured as a turn-shaped pattern; and the fourth transmission line (TL4) is formed in the metal layer Metal 5 and is configured as a turn-shaped pattern, wherein the metal layers Metal 2, Metal 3, Metal 4 and Metal 5 are parallel to each other, and wherein the turn-shaped pattern is a non-closed pattern shape. The transmission line TL1 in the metal layer Metal 2 is connected in parallel with the transmission line TL3 in the metal layer Metal 4 and serves as the main transmission line of the signal. The transmission line TL2 in the metal layer Metal 3 is connected in parallel with the transmission line TL4 in the metal layer Metal 5 and serves as a coupled transmission line for the signal. The transmission line TL1 is connected with the transmission line TL3 through a through hole, for example, the transmission line TL1 is connected with the transmission line TL3 in parallel through a first through hole and a second through hole; and the transmission line TL2 is connected with the transmission line TL4 through a through hole, for example, the transmission line TL2 is connected with the transmission line TL4 in parallel through a third through hole and a fourth through hole. Figure 4, the first through hole and the second through hole are located on the same side of the rotation shape, and the third through hole and the fourth through hole are located on the same side of the rotation shape, so that the main transmission line and the coupled transmission line of the directional coupler of the multilayer circuit board are symmetrical to each other. Those skilled in the art should understand that the positions of the first through hole to the fourth through hole of the directional coupler of the multilayer circuit board according to the present invention can be adjusted. For example, the first through hole to the fourth through hole can be located near the midline position of the rotation shape to make the structure of the directional coupler of the multilayer circuit board more symmetrical. According to an embodiment of the present invention, the transmission line is configured as a microstrip line or a stripline.

[0036] Port 1 (Port1) and Port 2 (Port2) are connected to the main transmission line through the first port through hole and the second port through hole, and Port 3 (Port3) and Port 4 (Port4) are connected to the coupling transmission line through the third port through hole and the fourth port through hole. In addition, by configuring the directional coupler of the multi-layer circuit board into a completely symmetrical structure, its four ports are completely reciprocally equivalent. In addition, the metal layer Metal1 and the metal layer Metal 6 are used as ground planes, which are respectively configured on the upper and lower parts of the main transmission line and the coupling transmission line.

[0037] refer to Figure 4 The characteristic impedance of the main transmission line formed by the parallel-connected transmission lines TL1 and TL3 is jointly determined by TL1 and TL3, and the characteristic impedance of the coupled transmission line is jointly determined by the transmission lines TL2 and TL4. The characteristic impedance is adjusted by adjusting the width of the transmission lines TL1 and TL3 in the main transmission line. Similarly, the characteristic impedance is adjusted by adjusting the width of the transmission lines TL2 and TL4 in the coupled transmission line.

[0038] refer to Figure 4 The coupling degree between the main transmission line and the coupling transmission line is mainly affected by parasitic capacitances C1, C2 and C3. The parasitic capacitances C1, C2 and C3 are adjusted by adjusting the thickness L of the multilayer metal interlayer dielectric (for example, the dielectric thickness L can be determined according to the number of metal layers used). According to an embodiment of the present invention, a dielectric material with a dielectric constant of 3.9 can be used. The adjustable range of the dielectric thickness L is 25um-60um. When the line width is reduced to reduce the size of the coupler, the parasitic capacitances C1, C2 and C3 will be affected and reduced. At this time, the dielectric thickness L can be reduced, or a material with a higher dielectric constant can be used to improve the coupling degree.

[0039] In addition, the positions of the transmission lines TL1, TL2, TL3 and TL4 are adjusted in the vertical direction or the horizontal direction so that the position deviation of the transmission line is Δd (for example, the deviation Δd can be preferably configured as 50% of the line width of the transmission line). According to an embodiment of the present invention, the coupling degree is reduced by the position deviation Δd, and the deviation range can be 0-300%. And when the material thickness reaches the maximum, the parasitic capacitances C1, C2 and C3 can be further reduced by the position deviation Δd, thereby providing more flexibility for the coupling degree design, but a larger deviation will increase the size of the coupler. In addition, although in Figure 4 The embodiment shows a structure of using four metal layers to form a directional coupler. Those skilled in the art should understand that more metal layers can be used to form a directional coupler to further reduce the size of parasitic capacitance and increase design flexibility.

[0040] The structure of the directional coupler of the multi-layer circuit board significantly improves the design flexibility of the characteristic impedance and coupling degree of the transmission line, making it easier to meet the design requirements. Figure 4 , due to the parallel connection of multiple layers of metal, the parasitic resistance loss of the transmission line is reduced by 50%, thereby reducing the overall loss of the coupler. In addition, the multi-layer circuit board directional coupler has a smaller thermal resistance and can provide stronger heat dissipation capabilities.

[0041] Those skilled in the art should understand that although Figure 4 In the illustrated embodiment, the main transmission line and the coupled transmission line are formed by four transmission lines, namely, the first transmission line (TL1), the second transmission line (TL2), the third transmission line (TL3) and the fourth transmission line (TL4). However, different numbers of transmission lines may be used to form the present invention. For example, in the present invention, 2N (N is a natural number greater than 1) transmission lines are used to form the main transmission line and the coupled transmission line, wherein the transmission lines numbered as odd numbers are connected in parallel to form the main transmission line, and the transmission lines numbered as even numbers are connected in parallel to form the coupled transmission line.

[0042] Figure 5 is a schematic diagram showing the transmission and coupling loss of a directional coupler of a multi-layer circuit board; Figure 6 is a schematic diagram showing phase balance of a directional coupler of a multi-layer circuit board; and Figure 7 is a schematic diagram showing the isolation of a directional coupler of a multi-layer circuit board.

[0043] According to an embodiment of the present invention, the wiring of the coupler is made of, for example, metal copper, wherein the line width and line spacing are configured to be 50um and 40um respectively, and the thickness is 15um. The coupler is configured as a 6-layer circuit board, wherein a dielectric material with a dielectric constant of 3.9 (e.g., Hitachi_705G) is selected, the layer spacing is 30um, and the total size is 750um*2000um without using position deviation to reduce the area. Reference Figure 5 The directional coupler using the multi-layer circuit board according to the embodiment of the present invention has a wide bandwidth of 3.5 GHz-4.5 GHz, wherein at 3.5 GHz, its coupling loss is -3.287 dB, and at 4.5 GHz, its coupling loss is -3.340 dB. Figure 6 , the directional coupler of the multilayer circuit board has a phase deviation of 89.544° at 3.5GHz and a phase deviation of 90.454° at 4.5GHz in the bandwidth of 3.5GHz-4.5GHz. Figure 7 , the directional coupler of the multilayer circuit board has a bandwidth of 3.5GHz-4.5GHz, and at 3.5GHz, its isolation is -32.238dB, and at 4.5GHz, its isolation is -22.523dB. It can be seen from the above diagram that the directional coupler of the multilayer circuit board according to the present invention has a small loss, a good phase balance performance, and a good isolation effect.

[0044] According to the directional coupler of the multi-layer circuit board of the present invention, by forming the directional coupler in the multi-layer circuit board, the design of the coupler and the like is more flexible and easy to meet the design requirements. In addition, by forming the directional coupler through the multi-layer circuit board, the working bandwidth of the directional coupler is wider and its performance index is more excellent. By forming the directional coupler through the multi-layer circuit board, the directional coupler has better heat dissipation performance. By forming the directional coupler through the multi-layer circuit board and using the same rotational pattern in each layer, the structure is simple. Since the directional coupler of the multi-layer circuit board has a completely symmetrical structure, its electrical performance consistency is good and it is easier to produce. In addition, by forming the directional coupler through the multi-layer circuit board, there is no need to additionally design a special structure or a special process to form the directional coupler, so that the cost of the product is low and it can be mass-produced.

[0045] The miniature 3dB directional coupler based on the on-chip multi-layer circuit board according to the present invention has good performance and occupies a small area, and can greatly reduce the minimum packaging area of ​​the module, providing a good solution for handheld devices and wearable devices.

[0046] Although the present disclosure has been described with exemplary embodiments, various changes and modifications may be suggested to one skilled in the art. The present disclosure is intended to encompass such changes and modifications as fall within the scope of the appended claims.

[0047] Any description in the present invention should not be construed as implying that any particular element, step, or function is an essential element that must be included in the claims scope. The scope of the patented subject matter is limited solely by the claims.

Claims

1. A microwave directional coupler based on a multi-layer circuit board, comprising: a first port, a second port, a third port, and a fourth port; a main transmission line, the main transmission line being arranged between the first port and the second port; a coupled transmission line, the coupled transmission line being arranged between the third port and the fourth port, The main transmission line and the coupling transmission line are formed by transmission lines arranged in 2N different metal layers, where N is a natural number greater than 1. wherein the main transmission line is formed by connecting the transmission lines arranged in odd-numbered metal layers in parallel, and the coupled transmission line is formed by connecting the transmission lines arranged in even-numbered metal layers in parallel, The transmission lines arranged on the odd-numbered metal layers are connected in parallel through the first through hole and the second through hole. The transmission lines arranged on the even-numbered metal layers are connected in parallel through the third through hole and the fourth through hole. The first through hole and the second through hole as well as the third through hole and the fourth through hole are located on the same side of the rotational pattern. Wherein, the transmission lines arranged in 2N different metal layers are configured as a rotation-shaped pattern.

2. The microwave directional coupler based on a multi-layer circuit board according to claim 1, wherein: N = 2, and The main transmission line is formed by connecting the transmission lines arranged on the first metal layer and the third metal layer in parallel. The coupled transmission line is formed by connecting in parallel the transmission lines arranged on the second metal layer and the fourth metal layer.

3. The microwave directional coupler based on a multi-layer circuit board according to claim 1, wherein: The transmission lines arranged in 2N different metal layers are configured as microstrip lines or strip lines.

4. The microwave directional coupler based on a multi-layer circuit board according to claim 1, wherein: The first through hole, the second through hole, the third through hole and the fourth through hole are located at the center line of the rotational pattern.

5. The microwave directional coupler based on a multi-layer circuit board according to claim 1, further comprising a first ground plane and a second ground plane, wherein the first ground plane and the second ground plane are respectively arranged above and below the main transmission line and the coupled transmission line.

6. The microwave directional coupler based on a multi-layer circuit board according to claim 1, wherein: The dielectric thickness L between the metal layers is determined according to the number of metal layers 2N.

7. The microwave directional coupler based on a multi-layer circuit board according to claim 1, wherein: The parasitic capacitance between the transmission lines is adjusted by adjusting the positions of the transmission lines arranged in 2N different metal layers in the horizontal direction or the vertical direction.

8. The microwave directional coupler based on a multi-layer circuit board according to claim 1, wherein: The directional coupler has a bandwidth of 3.5 GHz to 4.5 GHz.

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