A compact coupler structure

Abstract

The application discloses a compact coupler structure, which comprises a dielectric substrate, a first layer of metal transmission line and a second layer of metal transmission line arranged on the dielectric substrate in sequence; the first layer of metal transmission line and the second layer of metal transmission line are electromagnetically coupled with each other; one end of the first layer of metal transmission line or the second layer of metal transmission line is an input port; any two ports of the remaining three ports are two output ports respectively; after an input signal is fed from the input port, the input signal is coupled through the first layer of metal transmission line and the second layer of metal transmission line and is output from the two output ports; the first layer of metal transmission line and the second layer of metal transmission line are respectively provided with a first control port and a second control port, and a first impedance element is connected between the first control port and the second control port to form a feedback channel between the two transmission lines; under the condition of medium and low frequency, power distribution is realized by the compact structure, and the two output ports are provided with a preset and settable phase difference to support flexible adjustment of port impedance.

Description

Technical Field

[0001] This invention belongs to the field of monolithic microwave integrated circuits (MMIC), specifically relating to a compact coupler structure. Background Technology

[0002] With the rapid development of fifth-generation mobile communication technology (5G) and future mobile communications, satellite internet, phased array radar, and other modern wireless systems, monolithic microwave integrated circuits (MMICs) are evolving towards high integration, multifunctionality, and miniaturization. Simultaneously, system-in-package (SiP) and heterogeneous integration technologies are placing stringent demands on the size, performance, and functional integration of passive devices. Under these trends, high-performance, compact couplers capable of integrating signal power distribution, phase transformation, impedance transformation, and other functions have become crucial fundamental components in RF front-end design.

[0003] Traditional planar couplers, such as branch-joint couplers, Lange couplers, and various structures based on quarter-wavelength transmission lines, offer good amplitude and phase characteristics, but their physical size is inversely proportional to the operating frequency. Their large size in the low-to-mid-frequency range makes them difficult to integrate. Secondly, traditional couplers have a fixed port impedance of 50Ω, while power transistors in compound semiconductor processes exhibit lower impedance at their optimal operating point. This results in an excessively large impedance ratio compared to the input and output impedances in circuit designs such as Doherty power amplifiers, leading to significant challenges in matching circuit design and limited design freedom. Furthermore, existing on-chip miniaturized couplers are manufactured using three-layer metal-interconnect semiconductor processes, making them unsuitable for design using two-layer metal-interconnect semiconductor processes. Summary of the Invention

[0004] This invention addresses the problems existing in the prior art by providing a compact coupler structure that can achieve power distribution in a compact structure under low and medium frequency conditions, provide a preset and configurable phase difference for the two output ports, and support flexible adjustment of port impedance.

[0005] To solve the above technical problems, the present invention provides the following technical solution: a compact coupler structure, comprising a dielectric substrate, on which a first layer of metal transmission lines and a second layer of metal transmission lines are sequentially disposed; the first layer of metal transmission lines and the second layer of metal transmission lines are electromagnetically coupled to each other; one end of the first layer of metal transmission lines or the second layer of metal transmission lines is an input port; any two of the remaining three ports are respectively a first output port and a second output port; after the input signal is fed in from the input port, it is coupled through the first layer of metal transmission lines and the second layer of metal transmission lines, and output from the two output ports; The first layer metal transmission line and the second layer metal transmission line are respectively provided with a first control port and a second control port. A first impedance element is connected between the first control port and the second control port to form a feedback path between the two transmission lines.

[0006] Furthermore, the aforementioned first-layer metal transmission line and second-layer metal transmission line are coupled through a thin-film dielectric layer.

[0007] Furthermore, the aforementioned thin film dielectric layer has a thickness on the submicron level, and the coupling coefficient between the first layer metal transmission line and the second layer metal transmission line is 0.7~0.9.

[0008] Furthermore, the width of the first layer metal transmission line is greater than the width of the second layer metal transmission line, and except for the positions of each port, the second layer metal transmission line is positioned directly opposite the first layer metal transmission line, so that the second layer metal transmission line falls completely within the width range of the first layer metal transmission line in the width direction.

[0009] Furthermore, the remaining port at both ends of the aforementioned first-layer metal transmission line or second-layer metal transmission line is a matching port, which is externally connected to a second impedance element.

[0010] Furthermore, the aforementioned first impedance element is configured to adjust the phase difference between the second output port and the first output port, as well as the port isolation. The absolute value of the phase difference is any preset target value within the range of 50° to 90°. This preset target value is jointly determined by the capacitance value of the first impedance element and the area of ​​the overlapping region between the first layer metal transmission line and the second layer metal transmission line. Both can change the even-mode / odd-mode propagation constant, thereby changing the phase difference. Specifically, increasing the capacitance value or increasing the overlapping region area will reduce the difference in even-mode / odd-mode propagation constants, thus reducing the phase difference; conversely, decreasing the capacitance value or decreasing the overlapping region area will increase the difference in propagation constants, and the phase difference will increase accordingly.

[0011] Simultaneously, the above two parameters are also used to adjust the port isolation between the two output ports. As the capacitance value of the first impedance element changes, or the overlap area changes, the parity-even mode propagation constant between the two transmission lines and the phase relationship between the direct coupling path and the feedback coupling path between the output ports both change, thereby enhancing or canceling the signal coupling between the output ports. Therefore, the isolation between the output ports exhibits a non-linear changing trend. Within a specific parameter range, the two coupling paths partially cancel each other out to improve the isolation between the output ports: by coordinating the adjustment of the capacitance value and the overlap area, the required isolation level can be obtained while setting the phase difference to any value within the range of 50° to 90°.

[0012] Furthermore, by adjusting the linewidth parameters of the first and second layer metal transmission lines, the inductance and capacitance per unit length of the two transmission lines can be changed respectively, thereby adjusting the even-mode impedance and odd-mode impedance. Simultaneously, by adjusting the impedance value of the second impedance element connected to the matching port, the odd-mode termination condition and the reflection characteristics of the coupling network can be changed, allowing the equivalent port impedances of the input port, the first output port, and the second output port to be jointly adjusted to a preset target value.

[0013] Furthermore, the first impedance element is a capacitor; the second impedance element is a grounding resistor.

[0014] Furthermore, the ratio of the signal output power of the aforementioned first output port to the second output port is set to any ratio between 5:1 and 1:5.

[0015] Based on the same inventive concept, the present invention also discloses a monolithic microwave integrated circuit, including the above-described compact coupler structure.

[0016] Compared to existing technologies, the beneficial technical effects of the present invention using the above technical solution are as follows: The present invention adopts a two-layer metal transmission line structure, achieving strong coupling between the two metal transmission lines through a thin-film dielectric layer. The input and output ports offer flexible selection, and the absolute value of the phase difference between the signals output from the first signal output port and the second signal output port can be preset to a target value between 50° and 90°, providing phase compensation functionality in circuit designs such as Doherty power amplifiers. Simultaneously, the port impedance values ​​of the signal input port, the first signal output port, and the second signal output port can be adjusted according to the output impedance and input impedance of the preceding and following stages, simplifying the design of inter-stage matching networks; and meeting the high integration and multi-functional fusion module requirements of mid-to-low frequency RF integrated circuits. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the compact coupler structure in the embodiment.

[0018] Figure 2 This is another schematic diagram of the compact coupler structure in the embodiment.

[0019] Figure 3 This is a circuit schematic diagram of the compact coupler structure in the embodiment.

[0020] Figure 4 The figure shows the simulation results of the reflection coefficient characteristics of the input and output ports of the compact coupler structure of the present invention.

[0021] Figure 5 The figure shows the simulation results of the insertion loss of the compact coupler structure of the present invention.

[0022] Figure 6The figure shows the simulation results of the phase difference between the two output ports of the compact coupler structure of the present invention.

[0023] Figure 7 The figure shows the simulation results of the isolation between the two ports of the compact coupler structure of the present invention.

[0024] Figure 8 Smith chart of impedance transformation for matching the output port impedance of a conventional coupler with the source impedance of the subsequent transistor.

[0025] Figure 9 The Smith chart shows the impedance transformation corresponding to the matching of the output port impedance of the compact coupler of this invention with the source impedance of the subsequent transistor. Detailed Implementation

[0026] To better understand the technical content of the present invention, specific embodiments are described below in conjunction with the accompanying drawings.

[0027] In this invention, various aspects of the invention are described with reference to the accompanying drawings, in which numerous illustrative embodiments are shown. Embodiments of the invention are not limited to those depicted in the drawings. It should be understood that the invention is implemented through any of the various concepts and embodiments described above, as well as the concepts and embodiments described in detail below, because the concepts and embodiments disclosed herein are not limited to any particular implementation. Furthermore, some aspects of the invention disclosed may be used alone or in any suitable combination with other aspects of the invention disclosed.

[0028] This invention discloses a compact coupler structure, particularly suitable for Doherty power amplifier architectures operating in the mid-to-low frequency range. The coupler employs a two-layer metal transmission line structure to achieve a compact design, and its output port features adjustable impedance and a preset target phase difference of 50° to 90°. Example

[0029] like Figure 1 , Figure 2 As shown, this embodiment provides a compact coupler structure, including a dielectric substrate, on which a first layer of metal transmission lines metal1 and a second layer of metal transmission lines metal2 are sequentially arranged in a vertically distributed manner; the first layer of metal transmission lines metal1 and the second layer of metal transmission lines metal2 are electromagnetically coupled to each other. The first layer metal transmission line metal1 has port 1, port 2 and port 3; the second layer metal transmission line metal2 has port 4, port 5 and port 6, with port 4 serving as the signal input port IN, and port 1 and port 5 serving as the first output port OUT1 and the second output port OUT2, respectively. After the input signal is fed in from the signal input port IN, it is coupled through the first layer metal transmission line metal1 and the second layer metal transmission line metal2, and output from the first output port OUT1 and the second output port OUT2. It should be noted here that the input port and the two output ports only need to be the two ends of the first layer metal transmission line and the second layer metal transmission line; it is not limited to the correspondence of port 4 as the signal input port, port 1 as the first output port and port 5 as the second output port in the embodiment.

[0030] Of the four ports at both ends of the two-layer metal transmission line, port 2, excluding the input port, the first output port, and the second output port, is used as a matching port. This port is connected to one end of the grounding resistor R, and the other end of the grounding resistor R is grounded. By changing the widths of the first and second metal transmission lines, the characteristic impedances of the two metal transmission lines are adjusted respectively; at the same time, the impedance value of the grounding resistor R is adjusted; thereby setting the impedances of the input port, the first output port, and the second output port to their respective desired target impedance values.

[0031] A capacitor C is connected between ports 3 and 6. The capacitor C is used to adjust the phase difference between the second output port and the first output port, as well as the isolation between the ports. The absolute value of the phase difference can be any preset target value in the range of 50° to 90°. This preset target value is determined by the capacitance value of the first impedance element and the area of ​​the overlapping region between the first layer metal transmission line and the second layer metal transmission line. Specifically, increasing the capacitance value or increasing the area of ​​the overlapping region will decrease the phase difference; decreasing the capacitance value or decreasing the area of ​​the overlapping region will increase the phase difference.

[0032] Simultaneously, the above two parameters are also used to adjust the port isolation between the two output ports. As the capacitance value of the first impedance element changes, or the overlap area changes, the odd-even mode propagation constant between the two transmission lines and the phase relationship between the direct coupling path and the feedback coupling path between the output ports both change, thereby enhancing or canceling the signal coupling between the output ports. Therefore, the isolation between the output ports exhibits a non-linear changing trend. Within a specific parameter range, the two coupling paths partially cancel each other out to improve the isolation between the output ports. By optimizing the adjustment of the capacitance value and the overlap area, the required isolation level can be obtained while fixing the phase difference to any value within the preset range of 50° to 90°.

[0033] It should be noted here that ports 3 and 6 are located outside the ports at both ends of the first and second metal transmission lines, respectively. Their specific locations are not limited, as long as these two ports can be connected across a capacitor C.

[0034] In this embodiment, the width of the first layer metal transmission line metal1 is greater than the width of the second layer metal transmission line metal2. Except for ports 1, 2, 3, 4, 5, and 6, the second layer metal transmission line is positioned directly opposite the first layer metal transmission line, so that the second layer metal transmission line falls completely within the width range of the first layer metal transmission line in the width direction.

[0035] In this embodiment, the first metal transmission line and the second metal transmission line are coupled through a thin film dielectric layer with a thickness of submicron. The coupling coefficient between the first metal transmission line and the second metal transmission line is 0.7~0.9. A uniformly distributed interlayer coupling capacitor is formed between the two metal layers. This structure reduces the length of the metal lines and realizes the miniaturization of the coupler.

[0036] In this invention, the first and second layer metal transmission lines form a wide-side electromagnetic coupling structure through an overlapping region. The transmission characteristics between the two transmission lines are determined by both even and odd modes. The phase difference between output ports OUT1 and OUT2 is mainly determined by the difference between the propagation constants of even and odd modes. The first impedance element and the overlapping region between the two metal transmission lines together constitute a composite coupling network. The area of ​​the overlapping region determines the distributed coupling capacitance between the two transmission lines, while the first impedance element further alters the feedback coupling strength between the two transmission lines. When the capacitance value of the first impedance element increases, or the area of ​​the overlapping region between the first and second layer metal transmission lines increases, the coupling between the two transmission lines strengthens, the equivalent capacitance of the odd mode increases, the propagation speed of the odd mode decreases, and the propagation constant of the odd mode increases, thereby reducing the difference in propagation constants between even and odd modes, and thus gradually reducing the phase difference between OUT1 and OUT2. By jointly adjusting the capacitance value of the first impedance element and the area of ​​the overlapping region between the two metal transmission lines, the phase difference between OUT1 and OUT2 can be stably controlled within a preset target value in the range of 50° to 90°. Meanwhile, the isolation between OUT1 and OUT2 is determined by the direct electromagnetic coupling path and the feedback coupling path between the output terminals. When the capacitance value of the first impedance element and the area of ​​the overlapping region are within a preset range, partial phase cancellation is formed between the two coupling paths, thereby reducing crosstalk between the output terminals and improving the isolation between OUT1 and OUT2. When the capacitance value or the area of ​​the overlapping region increases further, the energy leakage between the output terminals increases due to the enhanced coupling exceeding the phase compensation effect, resulting in a decrease in the isolation between OUT1 and OUT2. Therefore, the isolation between OUT1 and OUT2 changes nonlinearly with the capacitance value of the first impedance element and the area of ​​the overlapping region, and reaches the required isolation state within a specific parameter range.

[0037] like Figure 3As shown, the signal is input from the input port IN, passes through the second metal transmission line metal2 to the second output port OUT2, and is output through the first metal transmission line metal1 and capacitor C via coupling to the first output port OUT1. Capacitor C adjusts the phase and isolation. By adjusting the capacitance value of C and the overlapping area of ​​metal1 and metal2, the phase difference and isolation between OUT1 and OUT2 can be changed, making the phase difference between OUT1 and OUT2 a preset target value of 50° to 90°.

[0038] By adjusting the linewidth parameters of the first and second layer metal transmission lines, the inductance and capacitance per unit length of the two transmission lines can be changed, thereby adjusting the even-mode and odd-mode impedances. Simultaneously, by adjusting the impedance value of the second impedance element connected to the matching port, the odd-mode termination condition and the reflection characteristics of the coupling network can be altered, allowing the equivalent port impedances of the input port, the first output port, and the second output port to be jointly adjusted to a preset target value.

[0039] The port impedances of input port IN, first output port OUT1, and second output port OUT2 are jointly determined by the characteristic impedances of the first-layer metal transmission line metal1, the second-layer metal transmission line metal2, and the external resistor R connected to the matching port. The characteristic impedances of the first and second-layer metal transmission lines are determined by their linewidth, metal thickness, dielectric thickness, and dielectric constant, respectively. Changing the linewidths of metal1 and metal2 adjusts the characteristic impedances of the two transmission lines. The external resistor R at the matching port alters the termination matching conditions of the coupling structure and affects the amplitude-phase relationship of the reflected, transmitted, and coupled waves within the coupling region. Therefore, by synergistically changing the characteristic impedances of metal1 and metal2, as well as the resistance value of R, the equivalent port impedances of input port IN, first output port OUT1, and second output port OUT2 can be adjusted, matching each port impedance to a preset target value, thereby reducing port reflections and improving signal transmission efficiency. Compared to the traditional 50Ω port impedance, the port impedance of each port in this embodiment is 10Ω, which is more suitable for matching the output impedance of the power amplifier's preamplifier stage and the input impedance of the power amplifier's output stage. This is equivalent to achieving an impedance transformation from 50Ω to 10Ω, simplifying the matching network design and widening the bandwidth.

[0040] The compact coupler in this embodiment integrates power distribution, phase adjustment, and impedance transformation functions with a miniaturized design, making it more suitable for compound semiconductor integrated circuit design.

[0041] In one implementation, the schematic diagram of the compact coupler circuit is referenced. Figure 3With a layout area of ​​251μm*214μm, it achieves a compact design compared to other couplers operating in this frequency band.

[0042] The performance of the compact coupler of this invention is verified through experiments below, such as... Figure 4 As shown, the simulation results of the reflection coefficient characteristics of the input and output ports of the compact coupler of the present invention indicate that the input and output matching of the compact coupler of the present invention achieves a good value, and the reflection coefficients of the input port return loss / reflection coefficient S11, the output port return loss / reflection coefficient S22, and the matching port return loss / reflection coefficient S33 are all less than -12dB. like Figure 5 As shown, the simulation results of the output insertion loss of the compact coupler of the present invention show that the S21 curve increases from -4.1dB to -2.5dB with increasing frequency, while the S31 curve decreases from -3.5dB to -6.2dB with increasing frequency. like Figure 6 As shown in the figure, the simulation results of the phase difference between the two output ports of the compact coupler of the present invention are presented. It can be seen from the figure that the phase difference between the two output ports is 90°.

[0043] like Figure 7 As shown in the figure, the simulation results of the isolation between the two output ports of the compact coupler of the present invention show that the isolation between the output ports is greater than -8.6dB.

[0044] like Figure 9 As shown, the Smith chart corresponding to the impedance transformation of the compact coupler of the present invention, which matches the output port impedance with the source impedance of the subsequent transistor, is shown in the figure. Figure 8 A comparison of the Smith charts corresponding to the impedance transformation of traditional couplers shows that traditional couplers require two stages of LC networks for impedance transformation, while the compact coupler structure of this invention only requires one stage of LC network to achieve impedance transformation. The compact coupler structure of this invention can significantly simplify the design of matching circuits and improve bandwidth.

[0045] While the present invention has been described above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A compact coupler structure, comprising a dielectric substrate, characterized in that, A first layer of metal transmission lines and a second layer of metal transmission lines are sequentially arranged on the dielectric substrate; the first layer of metal transmission lines and the second layer of metal transmission lines are electromagnetically coupled to each other; one end of the first layer of metal transmission lines or the second layer of metal transmission lines is an input port; any two of the remaining three ports are respectively the first output port and the second output port; after the radio frequency signal is input from the input port, it is coupled through the first layer of metal transmission lines and the second layer of metal transmission lines and output from the two output ports; the first layer of metal transmission lines and the second layer of metal transmission lines are respectively provided with a first control port and a second control port, and a first impedance element is connected between the first control port and the second control port to form a feedback path between the two transmission lines.

2. The compact coupler structure according to claim 1, characterized in that, The first metal transmission line and the second metal transmission line are coupled through a thin film dielectric layer.

3. The compact coupler structure according to claim 2, characterized in that, The thickness of the thin film dielectric layer is in the submicron range, and the coupling coefficient between the first layer metal transmission line and the second layer metal transmission line is 0.7~0.

9.

4. The compact coupler structure according to claim 2 or 3, characterized in that, The width of the first layer metal transmission line is greater than the width of the second layer metal transmission line, and except for the positions of each port, the second layer metal transmission line is positioned directly opposite the first layer metal transmission line, so that the second layer metal transmission line falls completely within the width range of the first layer metal transmission line in the width direction.

5. The compact coupler structure according to claim 4, characterized in that, The remaining port at both ends of the first or second layer metal transmission line is a matching port, which is connected to a second impedance element.

6. The compact coupler structure according to claim 5, characterized in that, The first impedance element is configured to adjust the phase difference between the second output port and the first output port and the port isolation; the absolute value of the phase difference is any preset value in the range of 50° to 90°, which is determined by the capacitance value of the first impedance element and the area of ​​the overlapping region between the first layer metal transmission line and the second layer metal transmission line.

7. The compact coupler structure according to claim 6, characterized in that, By changing the widths of the first and second metal transmission lines, the characteristic impedances of the two metal transmission lines are adjusted respectively; at the same time, the impedance value of the second impedance element connected to the matching port is adjusted; thereby setting the impedances of the input port, the first output port, and the second output port to their respective desired target impedance values.

8. The compact coupler structure according to claim 7, characterized in that, The first impedance element is a capacitor; the second impedance element is a resistor.

9. The compact coupler structure according to claim 1, characterized in that, The ratio of the signal output power of the first output port to that of the second output port is set to any ratio between 5:1 and 1:

5.

10. A monolithic microwave integrated circuit, characterized in that, Includes the compact coupler structure as described in any one of claims 1-9.

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