A reconfigurable low-coupling dual-mode transmission line

Abstract

The present invention proposes a reconfigurable low-coupling dual-mode transmission line that can support the transmission of orthogonal dual-mode electromagnetic waves. By integrating diodes into the transmission line structure, the transmission line is made reconfigurable. The transmission line has three metal layers, with dielectrics filling the spaces between them. The metal layers are connected by conductive vias, and diodes are soldered to the metal layers. By controlling the bias voltage of the diodes, the transmission mode of the transmission line can be switched between dual-mode, odd-mode, even-mode, and cutoff states, thereby freely regulating the electromagnetic wave transmission characteristics. Because the transmitted dual-mode electromagnetic waves are orthogonal to each other, the transmission line proposed by the present invention can transmit multiple signals with lower crosstalk, and the coupling degree of the transmission line can decrease as the transmission distance increases. This transmission line has the advantages of multi-mode transmission, reconfigurability, low coupling, and high integration, and can provide a signal transmission solution for highly integrated, multifunctional systems.

Description

Technical Field

[0001] The present invention relates to low-coupling microwave transmission line technology, which is used to realize low-coupling and lossless microwave transmission lines for transmitting multiple signals in an integrated system, and belongs to the field of microwave devices and new artificial electromagnetic materials. Background Art

[0002] With the rapid development of information technology, systems are increasingly demanding the transmission of large amounts of information. This requires integrating more signal transmission channels into smaller system spaces. The microstrip line structure commonly used for signal transmission in current microwave systems has weak field confinement capabilities. As systems move toward higher integration densities and smaller spaces become increasingly compact, adjacent microstrip lines are prone to crosstalk, leading to signal distortion. Therefore, traditional microstrip line structures are not suitable for use in highly integrated microwave system designs.

[0003] To address these issues, researchers have proposed artificial surface plasmon structures that mimic the characteristics of surface plasmon structures. Surface plasmons are surface electromagnetic wave modes that exist at the interface between metals and dielectrics in the optical frequency band. The propagation of surface plasmon modes decays exponentially in the direction perpendicular to the interface, resulting in strong field confinement. However, in the microwave or terahertz frequency bands, surface plasmons have difficulty propagating on metal surfaces due to the ideal conductor properties of metals. To address this issue, researchers have proposed using various metamaterial structures to mimic surface plasmon modes in the microwave and terahertz bands. Among the many artificial surface plasmon metamaterial structures, ultrathin comb-like metal strips have become a hot topic of research in this area due to their compatibility with modern integrated circuit processes. Compared to traditional microstrip lines, artificial surface plasmon transmission lines offer advantages such as low crosstalk and easy conformality, making them suitable for highly integrated microwave and terahertz circuit systems. However, although general artificial surface plasmon structures can greatly reduce crosstalk between lines compared to microstrip lines, their transmission electromagnetic wave modes are both single-mode transmission like microstrip lines, and the space occupied still needs to be reduced. In addition, both artificial surface plasmon transmission lines and microstrip lines have the problem of increased inter-line coupling as the length of the transmission line increases. Therefore, how to further reduce the crosstalk of multi-channel signal transmission in integrated circuits and further reduce the space occupied by transmission lines remains a valuable research issue. Summary of the Invention

[0004] Technical Problem: To address existing problems, the present invention provides a reconfigurable low-coupling dual-mode transmission line that can transmit dual-mode electromagnetic waves with a low coupling degree and is reconfigurable. Compared to traditional microstrip and artificial surface plasmon transmission lines, this line offers advantages in low coupling, high integration, and flexible controllability, and holds great promise for practical application.

[0005] Technical solution: The present invention proposes a reconfigurable low-coupling dual-mode transmission line, the main body of which is composed of a plurality of reconfigurable low-coupling dual-mode transmission line units connected in series. The transmission line units are arranged in a straight line and are located in the middle of the overall structure of the transmission line, wherein each transmission line unit includes a five-layer structure, namely three metal layers and two dielectric layers, and the order of the layers is top metal layer unit, first dielectric layer, middle metal layer unit, second dielectric layer, and bottom metal layer unit; the top metal layer unit and the bottom metal layer unit are respectively connected to the middle metal layer unit through metal through holes; the overall layered structure of the transmission line is composed of three metal layers and two dielectric layers, like the transmission line unit, wherein the top metal layer includes multiple top metal layers. The units are connected in series, with upper feeding structures and upper bias circuit structures at both ends; the middle metal layer includes the plurality of middle metal layer units connected in series, with circular hole structures at both ends; the bottom metal layer includes the plurality of bottom metal layer units connected in series, with lower feeding structures and lower bias circuit structures at both ends; in order to excite two modes of electromagnetic waves, two independent input ports and two independent output ports are provided, wherein the first input port and the first output port are connected to the upper feeding structure on the top metal layer unit through a 50Ω microstrip line for exciting even-mode electromagnetic waves; the second input port and the second output port are placed on the bottom metal layer and connected to the lower feeding structure, and the transmission of odd-mode electromagnetic waves is excited through the transition of the slotted structure in the middle metal layer unit.

[0006] The top metal layer unit in the transmission line unit includes a microstrip line structure, a first top metal patch, a second top metal patch, a third top metal patch, and a fourth top metal patch symmetrically connected in parallel on both sides of the microstrip line structure, a first varactor diode connected between the first top metal patch and the second top metal patch, and a second varactor diode connected between the third top metal patch and the fourth top metal patch.

[0007] The middle metal layer unit in the transmission line unit is a metal ground, and a slot structure is provided in the middle of the middle metal layer unit along the signal transmission direction.

[0008] The bottom metal layer unit in the transmission line unit is provided with a first bottom metal patch, a second bottom metal patch, and a third bottom metal patch. The three bottom metal patches are arranged in a "U shape", and a first PIN diode is connected between the first bottom metal patch and the second bottom metal patch, and a second PIN diode is connected between the second bottom metal patch and the third bottom metal patch.

[0009] The first top metal patch of the top metal layer unit and the first bottom metal patch of the bottom metal layer unit are connected to the middle metal layer unit through metal through holes; the fourth top metal patch of the top metal layer unit and the third bottom metal patch of the bottom metal layer unit are connected to the middle metal layer unit through metal through holes.

[0010] In the transmission line, the microstrip line structures in a plurality of series-connected reconfigurable low-coupling dual-mode transmission line units are connected in series.

[0011] The second top metal patch and the third top metal patch are in a zigzag shape and are respectively connected to the microstrip line structure.

[0012] By controlling the bias voltages of the first and second varactor diodes in the top metal layer unit and the on and off states of the first and second PIN diodes in the bottom metal layer unit, the transmission mode of the transmission line is switched among dual mode, odd mode, even mode and cut-off state.

[0013] When the transmission line operates in a dual-mode transmission mode, two independent signals are transmitted, and the more transmission line units there are, that is, the longer the transmission line is, the higher the isolation between the two signals.

[0014] The materials of the first dielectric layer and the second dielectric layer are Rogers RO4003 substrates.

[0015] Beneficial effects: Compared with the prior art, the advantages of the present invention are:

[0016] 1. The present invention can realize dual-mode transmission of electromagnetic waves, effectively improving the information transmission capacity.

[0017] 2. The present invention can flexibly control the transmitted electromagnetic waves through diodes and has a reconfigurable function.

[0018] 3. The present invention can occupy less space when transmitting multi-channel signals compared to traditional single-mode transmission lines.

[0019] 4. The dual-mode signal transmitted by the present invention has a lower coupling degree, and as the length of the transmission line increases, the coupling degree can be further reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the structure of a reconfigurable low-coupling dual-mode transmission line unit; a is a schematic diagram of the mechanical structure, and b is a three-layer plan view. In the figure, V1 is the voltage loaded on the microstrip line, V2 is the voltage loaded on the metal ground and the metal patch connected to the metal through-hole, V3 is the voltage loaded on the metal patch on the bottom metal layer that is not connected to the metal through-hole, a1, a3, and a4 are the widths of different metal patches, a2 is the width of the microstrip line, b1, b2, b3, and b4 are the lengths of different metal patches, c1, c3, and c4 are the distances between different metal patches, c2 is the width of the slot on the metal ground, and z x is the length of the meander structure in the metal patch, z y is the width of the meander structure in the metal patch, r1 is the radius of the metal through hole, and p is the total length of the unit.

[0021] Figure 2 is the dispersion curve of the reconfigurable low-coupling dual-mode transmission line unit when it works in the dual-mode transmission state;

[0022] Figure 3 This is a schematic diagram of the overall structure of the reconfigurable low-coupling transmission line; the top portion shows the top metal layer structure, the middle portion shows the middle metal layer structure, and the bottom portion shows the bottom metal layer structure. In the figure, w1, w2, w3, w4, and w5 are the widths of the microstrip lines; l1, l2, l3, and l4 are the lengths of the microstrip lines; r2 and r5 are the radii of the circular patch structures; r4 is the radius of the circular hole in the metal ground; and r3 and r6 are the radii of the fan-shaped structure in the bias circuit.

[0023] Figure 4 It is the S parameter of the simulated and measured reconfigurable low-coupling dual-mode transmission line transmitting even-mode electromagnetic waves.

[0024] Figure 5 It is the S parameter of the simulated and measured reconfigurable low-coupling dual-mode transmission line transmitting odd-mode electromagnetic waves.

[0025] The figure includes: top metal layer unit 1, upper feed structure 11, upper bias circuit structure 12, microstrip line structure 1.1, first top metal patch 1.2, second top metal patch 1.3, third top metal patch 1.4, fourth top metal patch 1.5, first varactor diode 1.6, second varactor diode 1.7, first input port 1.8, first output port 1.9;

[0026] Intermediate metal layer unit 2, circular hole structure 21, slotted structure 2.1;

[0027] Bottom metal layer unit 3, lower feed structure 31, lower bias circuit structure 32, first bottom metal patch 3.1, second bottom metal patch 3.2, third bottom metal patch 3.3, first PIN diode 3.4, second PIN diode 3.5, second input port 3.6, second output port 3.7;

[0028] A first dielectric layer 4 , a second dielectric layer 5 , and a metal through hole 6 . DETAILED DESCRIPTION

[0029] The technical solution of the present invention is described in detail below with reference to the accompanying drawings and specific examples;

[0030] The reconfigurable low-coupling dual-mode transmission line body of the present invention is composed of a plurality of reconfigurable low-coupling dual-mode transmission line units connected in series, and the transmission line units are arranged in a straight line and located in the middle of the overall structure of the transmission line, wherein each transmission line unit includes a five-layer structure, namely three metal layers and two dielectric layers, and the order of the interlayer arrangement is top metal layer unit 1, first dielectric layer 4, middle metal layer unit 2, second dielectric layer 5, bottom metal layer unit 3; the top metal layer unit 1 and the bottom metal layer unit 3 are respectively connected to the middle metal layer unit 2 through a metal through hole 6; the overall layered structure of the transmission line is composed of three metal layers and two dielectric layers, like the transmission line unit, wherein the top metal layer includes a plurality of top metal layer units 1 connected in series, and an upper feed structure 11 and an upper bias structure are provided at both ends. Circuit structure 12; the intermediate metal layer includes the multiple intermediate metal layer units 2 connected in series, with circular hole structures 21 provided at both ends; the bottom metal layer includes the multiple bottom metal layer units 3 connected in series, with a lower feeding structure 31 and a lower bias circuit structure 32 provided at both ends; in order to excite two modes of electromagnetic waves, two independent input ports and two independent output ports are provided, wherein the first input port 1.8 and the first output port 1.9 are connected to the upper feeding structure 11 on the top metal layer unit 1 through a 50Ω microstrip line for exciting even-mode electromagnetic waves; the second input port 3.6 and the second output port 3.7 are placed on the bottom metal layer unit 3 and connected to the lower feeding structure 31, and the transmission of odd-mode electromagnetic waves is excited through the transition of the slot structure 2.1 in the intermediate metal layer unit 2.

[0031] In the three-layer metal structure, top metal layer unit 1 and middle metal layer unit 2 are the primary structures supporting dual-mode electromagnetic wave transmission, while bottom metal layer unit 3 is primarily used to apply bias voltage to control the diode. Top metal layer unit 1 and bottom metal layer unit 3 are connected by metal vias through middle metal layer unit 2.

[0032] The top metal layer 1 in the transmission line unit includes a microstrip line structure 1.1, a first top metal patch 1.2, a second top metal patch 1.3, a third top metal patch 1.4, and a fourth top metal patch 1.5 symmetrically connected in parallel on both sides of the microstrip line structure 1.1, a first varactor diode 1.6 is connected between the first top metal patch 1.2 and the second top metal patch 1.3, and a second varactor diode 1.7 is connected between the third top metal patch 1.4 and the fourth top metal patch 1.5.

[0033] The middle metal layer 2 in the transmission line unit is a metal ground, and a slot structure 2.1 is provided in the middle of the middle metal layer 2 along the signal transmission direction.

[0034] The bottom metal layer 3 in the transmission line unit is provided with a first bottom metal patch 3.1, a second bottom metal patch 3.2, and a third bottom metal patch 3.3. The three bottom metal patches are arranged in a "U" shape, and a first PIN diode 3.4 is connected between the first bottom metal patch 3.1 and the second bottom metal patch 3.2, and a second PIN diode 3.5 is connected between the second bottom metal patch 3.2 and the third bottom metal patch 3.3.

[0035] The first top metal patch 1.2 of the top metal layer 1 and the first bottom metal patch 3.1 of the bottom metal layer 3 are connected to the middle metal layer 2 via metal vias 6. The fourth top metal patch 1.5 of the top metal layer 1 and the third bottom metal patch 3.3 of the bottom metal layer 3 are connected to the middle metal layer 2 via metal vias 6. In the transmission line, the microstrip line structures 1.1 of multiple series-connected reconfigurable low-coupling dual-mode transmission line units are connected in series. The second top metal patch 1.3 and the third top metal patch 1.4 are arranged in a zigzag shape and are respectively connected to the microstrip line structures 1.1. By controlling the bias voltages of the first varactor diode 1.6 and the second varactor diode 1.7 in the top metal layer 1 and the on / off switching of the first PIN diode 3.4 and the second PIN diode 3.5 in the bottom metal layer unit 3, the transmission mode of the transmission line can be switched between dual-mode, odd-mode, even-mode, and cut-off states.

[0036] The more series-connected reconfigurable low-coupling dual-mode transmission line units there are, the stronger the field binding capability is.

[0037] The reconfigurable low-coupling dual-mode transmission line unit has a microstrip line in the top metal layer unit 1 loaded with a voltage V1, a patch in the top metal layer unit 1 and the bottom metal layer unit 3 connected by a metal through-hole loaded with a voltage V2, and an independent patch in the bottom metal layer unit 3 loaded with a voltage V3. The capacitance of the varactor diode can be controlled by the bias voltage (V1-V2), and the on-off of the PIN diode can be controlled by the bias voltage (V2-V3). By flexibly changing the bias voltage, the transmission line can operate in single odd-mode transmission, single even-mode transmission, dual-mode transmission, and cut-off states.

[0038] The dielectric layer is made of Rogers RO4003 substrate, and its thicknesses are t1 and t2 respectively. The more the number of the plurality of series-connected reconfigurable low-coupling dual-mode transmission line units is, the stronger the field confinement capability is.

[0039] The specific structure of the reconfigurable low-coupling dual-mode transmission line unit is as follows: Figure 1As shown, the unit period p = 8mm, the patch width a1 = 0.4mm in the top metal layer unit 1, the patch length b1 = 0.6mm, b2 = 0.8mm, the patch gap c1 = 0.2mm, the microstrip line width a2 = 0.16mm, and the meandering structure length z between the patch and the microstrip line x =0.6mm, width z y =0.14mm, metal through hole radius r1 =0.15mm. In the bottom metal layer unit 3, the patch width a3 =0.66mm, a4 =1.8mm, the patch length b3 =0.9mm, b4 =1mm, and the patch gap c3 =0.48, c4 =0.2mm.

[0040] The operating frequency of the transmission line is set to 4GHz. When the diode is in different states, the reconfigurable low-coupling dual-mode transmission line can transmit electromagnetic waves of different modes. When the voltage of the varactor diode is 0.2pF and the PIN diode is disconnected, the transmission line can operate in a dual-mode transmission state; when the voltage of the varactor diode is 0.6pF and the PIN diode is disconnected, the transmission line unit can only support odd-mode electromagnetic wave transmission; when the capacitance of the varactor diode is 0.2pF and the PIN diode is turned on, the transmission line unit can only support even-mode electromagnetic wave transmission; when the capacitance of the varactor diode is 0.6pF and the PIN diode is turned on, the transmission line unit is in a cut-off state and cannot transmit electromagnetic waves. In the dual-mode working state, the dispersion curve of the reconfigurable low-coupling dual-mode transmission line unit is as follows: Figure 2 shown.

[0041] Feeding method and bias circuit for reconfigurable low-coupling dual-mode transmission line Figure 3As shown, to excite two modes of electromagnetic waves, two independent input and two independent output ports are required. The first input port 1.8 and the first output port 1.9 are connected to the transmission line on the top metal layer unit 1 via a 50Ω microstrip line to excite even-mode electromagnetic waves. The second input port 3.6 and the second output port 3.7 are placed on the bottom metal layer unit 3, and the transition of the slot structure in the middle metal layer unit 2 excites the transmission of odd-mode electromagnetic waves. The 50Ω microstrip line width w1 = 1.8mm. Due to the circular hole in the middle metal layer unit 2, a circular structure is added to the 50Ω feed line for impedance matching. The radius of this circular structure is r2 = 1.5mm, and the radius of the circular hole is r4 = 1.5mm. The width of the feed line connected to the port in the bottom metal layer unit 3 is w3 = 0.45mm. The distance between the feed line end and the metal patch is l3 = 6mm, and the radius of the circular structure at the feed line end is r5 = 1.5mm. The bias circuit line in top metal layer unit 1 has a length l2 = 13 mm, a width w2 = 0.2 mm, and a fan-out patch radius r3 = 8 mm. The bias circuit line in bottom metal layer unit 3 has a length l4 = 13 mm, a width w4 = 0.2 mm, a fan-out patch radius r6 = 8 mm, and a line width w5 = 0.16 mm connecting the patches.

[0042] The simulation and measured results of the transmission line structure formed by 40 units in series are shown in Figure 2. Figure 4 and Figure 5 As shown in the figure, at the operating frequency of 4 GHz, the insertion loss of the even mode and odd mode of the overall structure is higher than -1.37 dB, and the isolation is less than -35 dB, indicating that the transmission line can maintain a high isolation when transmitting two signals.

Claims

1. A reconfigurable low-coupling dual-mode transmission line, characterized in that: The transmission line body is composed of a plurality of reconfigurable low-coupling dual-mode transmission line units connected in series. The transmission line units are arranged in a straight line and are located in the middle of the overall structure of the transmission line. Each transmission line unit includes a five-layer structure, namely three metal layers and two dielectric layers. The order of the layers is top metal layer unit (1), first dielectric layer (4), middle metal layer unit (2), second dielectric layer (5), and bottom metal layer unit (3). The top metal layer unit (1) and the bottom metal layer unit (3) are connected to the middle metal layer unit (2) through metal through holes (6) respectively. The overall layered structure of the transmission line is composed of three metal layers and two dielectric layers, just like the transmission line unit. The top metal layer includes a plurality of top metal layer units (1) connected in series, and an upper feed structure (11) and an upper bias circuit structure (12) are provided at both ends. The intermediate metal layer comprises the plurality of intermediate metal layer units (2) connected in series, with circular hole structures (21) provided at both ends; the bottom metal layer comprises the plurality of bottom metal layer units (3) connected in series, with a lower feeding structure (31) and a lower bias circuit structure (32) provided at both ends; in order to excite electromagnetic waves of two modes, two independent input ports and two independent output ports are provided, wherein the first input port (1.8) and the first output port (1.9) are connected to the upper feeding structure (11) on the top metal layer unit (1) through a 50Ω microstrip line, for exciting even-mode electromagnetic waves; the second input port (3.6) and the second output port (3.7) are placed on the bottom metal layer and connected to the lower feeding structure (31), and excite the transmission of odd-mode electromagnetic waves through the transition of the slotted structure (2.1) in the intermediate metal layer unit (2).

2. The reconfigurable low-coupling dual-mode transmission line according to claim 1, characterized in that The top metal layer unit (1) in the transmission line unit comprises a microstrip line structure (1.1), a first top metal patch (1.2), a second top metal patch (1.3), a third top metal patch (1.4), and a fourth top metal patch (1.5) symmetrically connected in parallel on both sides of the microstrip line structure (1.1); a first varactor diode (1.6) is connected between the first top metal patch (1.2) and the second top metal patch (1.3); and a second varactor diode (1.7) is connected between the third top metal patch (1.4) and the fourth top metal patch (1.5).

3. The reconfigurable low-coupling dual-mode transmission line according to claim 1, characterized in that The middle metal layer unit (2) in the transmission line unit is a metal ground, and a slot structure (2.1) is provided in the middle of the middle metal layer unit (2) along the signal transmission direction.

4. The reconfigurable low-coupling dual-mode transmission line according to claim 1, characterized in that The bottom metal layer unit (3) in the transmission line unit is provided with a first bottom metal patch (3.1), a second bottom metal patch (3.2), and a third bottom metal patch (3.3); the three bottom metal patches are arranged in a "U" shape; a first PIN diode (3.4) is connected between the first bottom metal patch (3.1) and the second bottom metal patch (3.2); and a second PIN diode (3.5) is connected between the second bottom metal patch (3.2) and the third bottom metal patch (3.3).

5. The reconfigurable low-coupling dual-mode transmission line according to claim 1, characterized in that The first top metal patch (1.2) of the top metal layer unit (1) and the first bottom metal patch (3.1) of the bottom metal layer unit (3) are connected to the middle metal layer unit (2) via a metal through-hole (6); and the fourth top metal patch (1.5) of the top metal layer unit (1) and the third bottom metal patch (3.3) of the bottom metal layer unit (3) are connected to the middle metal layer unit (2) via a metal through-hole (6).

6. The reconfigurable low-coupling dual-mode transmission line according to claim 1, characterized in that In the transmission line, microstrip line structures (1.1) in a plurality of series-connected reconfigurable low-coupling dual-mode transmission line units are connected in series.

7. The reconfigurable low-coupling dual-mode transmission line according to claim 2, characterized in that The second top metal patch (1.3) and the third top metal patch (1.4) are in a zigzag shape and are respectively connected to the microstrip line structure (1.1).

8. The reconfigurable low-coupling dual-mode transmission line according to claim 1, characterized in that By controlling the bias voltages of a first varactor diode (1.6) and a second varactor diode (1.7) in a top metal layer unit (1) and the on / off switching of a first PIN diode (3.4) and a second PIN diode (3.5) in a bottom metal layer unit (3), the transmission mode of the transmission line is switched among dual mode, odd mode, even mode and cut-off states.

9. The reconfigurable low-coupling dual-mode transmission line according to claim 1, characterized in that When the transmission line operates in a dual-mode transmission mode, two independent signals are transmitted, and the more transmission line units there are, that is, the longer the transmission line is, the higher the isolation between the two signals.

10. The reconfigurable low-coupling dual-mode transmission line according to claim 1, characterized in that The materials of the first dielectric layer (4) and the second dielectric layer (5) are Rogers RO4003 substrates.

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