A phase difference adjustable balun based on dual-mode artificial surface plasmons

Abstract

The application discloses a phase difference adjustable balun based on a double-mode artificial surface plasmon, and utilizes a double-mode SSPP transmission structure to support orthogonal parallel transmission of odd-mode and even-mode electromagnetic waves, and cooperates with a Wilkinson power divider of an input port to realize two-way equal-amplitude and in-phase feeding; wherein, a varactor diode is loaded between even-mode SSPP units on an even-mode transmission path, and continuous phase movement of the even mode is realized by adjusting and controlling even-mode dispersion characteristics through a bias voltage; no regulating and controlling structure is loaded on the odd-mode transmission path, and the odd-mode transmission path is only used as a reference transmission line, and the phase of the odd-mode transmission path remains stable in a working frequency range; only the varactor diode on the even-mode side needs to be independently regulated and controlled, so that continuous adjustable output phase difference between a second port and a third port can be realized; the balun function of continuous adjustable phase difference is realized on a single transmission line, and has the advantages of compact structure, simple regulation and control, and high mode isolation degree, and can realize continuous adjustable output phase difference while maintaining a compact structure.

Description

Technical Field

[0001] This invention relates to the field of microwave and millimeter-wave device design technology, and in particular to a phase difference tunable balun based on dual-mode artificial surface plasmons. Background Technology

[0002] A balun is an important microwave device that converts unbalanced signals into balanced signals. It is widely used in microwave and millimeter-wave systems such as antenna feeding, balanced mixers, and power amplifiers. The core of balun design lies in achieving a specific phase difference between the two output ports while maintaining good amplitude balance within the operating frequency band.

[0003] In recent years, as communication systems have evolved towards multifunctionality and reconfigurability, higher demands have been placed on the phase difference control capabilities of baluns. Baluns with continuously adjustable output phase differences can provide flexible phase control methods for systems such as phased array antennas and beamforming networks, and have significant application value. However, the output phase difference of traditional baluns is usually fixed, making it difficult to achieve continuous adjustment. Existing adjustable balun schemes often require the introduction of additional phase-shifting networks or adjustable components, resulting in complex structures, increased size, and difficulty in control, and the amplitude balance is easily affected during the control process. Summary of the Invention

[0004] Purpose of the invention: This invention provides a phase difference-tunable balun based on dual-mode artificial surface plasmons, which can achieve continuous adjustment of the output phase difference while maintaining a compact structure.

[0005] Technical solution: The present invention provides a phase difference tunable balun based on dual-mode artificial surface plasmons, comprising: a top metal layer, a first dielectric layer, a ground layer, an adhesive layer, a second dielectric layer, and a bottom metal layer stacked sequentially from top to bottom;

[0006] The input signal enters the Wilkinson power divider through the first port and is split into two equal-amplitude, in-phase signals. The signal in the even-mode branch is impedance matched by the transition structure, which excites an even-mode SSPP wave that propagates along the periodic even-mode SSPP unit in the top metal layer, with an even-symmetric electric field distribution. The signal in the odd-mode branch is fed into the bottom 50Ω microstrip line through a via. Through the electromagnetic coupling of the odd-mode coupling disc and the odd-mode coupling aperture, an odd-mode SSPP wave is excited and propagates along the periodic odd-mode SSPP unit on the ground plane, with an odd-symmetric electric field distribution.

[0007] When different DC bias voltages are applied through the positive-feed structure, the varactor diodes on the even-mode transmission path exhibit different capacitance values, changing the equivalent circuit parameters of the even-mode SSPP unit. This dynamically controls the dispersion characteristics of the even-mode SSPP, causing continuous phase shift in the even mode. The dispersion characteristics on the odd-mode transmission path remain constant, and the phase remains stable, enabling continuous adjustment of the output phase difference between the second and third ports. Since the electromagnetic field distributions of the odd and even modes are orthogonal, the transmission of the two modes is naturally isolated, and phase modulation of the even mode does not affect the transmission characteristics of the odd mode.

[0008] Furthermore, the top metal layer includes a first port, a second port, a third port, a top 50Ω microstrip line, a 70.7Ω microstrip line, a 100Ω parallel resistor, a transition structure, several even-mode SSPP units, a varactor diode, a positive electrode feeding structure, a negative electrode feeding structure, a choke structure, and a via.

[0009] The first port is the input port. The top 50Ω microstrip line, 70.7Ω microstrip line, and 100Ω parallel resistor constitute the Wilkinson power divider. A transition structure connects the even-mode output port of the Wilkinson power divider to the even-mode SSPP unit for impedance matching. A varactor diode is connected across adjacent even-mode SSPP units. A bias voltage is applied through the positive electrode feeding structure to dynamically adjust the dispersion characteristics of the even-mode SSPP and achieve continuous control of the even-mode phase. The negative terminal of the varactor diode is connected to the ground plane through a via via the negative electrode feeding structure to form a DC loop. A choke structure is used to isolate the DC control signal from the RF signal. The odd-mode output port of the Wilkinson power divider is connected to the bottom 50Ω microstrip line through a via. The second port is located at the output end of the even-mode SSPP unit as the even-mode output port.

[0010] Furthermore, the choke structure adopts a fan-shaped stub structure to suppress the interference of radio frequency signals on the DC bias network and achieve isolation between DC control signals and radio frequency signals.

[0011] Furthermore, the even-mode SSPP unit includes a central conductor, parallel stubs, and gaps; the parallel stubs are symmetrically loaded on both sides of the central conductor; adjacent even-mode SSPP units are physically isolated by gaps to achieve electrical connection.

[0012] Furthermore, the ground plane includes odd-mode coupling circular holes and odd-mode SSPP units; the odd-mode SSPP units include odd-mode central slots and symmetrical slots, with the symmetrical slots etched on both sides of the odd-mode central slots to form periodically arranged odd-mode SSPP units; the odd-mode central slots extend along the length of the ground plane, and the odd-mode SSPP waves are transmitted along the odd-mode SSPP units on the ground plane, without any varactor diodes or other control structures being loaded, and are only used as transmission lines.

[0013] Furthermore, the bottom metal layer includes a bottom 50Ω microstrip line and an odd-mode coupling disc; the bottom 50Ω microstrip line is connected to the odd-mode output port of the Wilkinson power divider through a via; the bottom 50Ω microstrip line and the odd-mode coupling disc are coupled through an odd-mode coupling aperture to excite an odd-mode SSPP wave; a third port is located at the output end of the odd-mode SSPP wave, serving as the odd-mode output port; the bottom 50Ω microstrip line and the odd-mode coupling disc in the bottom metal layer are located directly below the odd-mode coupling aperture, and the odd-mode SSPP wave is excited by electromagnetic coupling, realizing the conversion of the odd-mode signal between the bottom microstrip line mode and the odd-mode SSPP mode.

[0014] Furthermore, the top and bottom metal layers are made of copper.

[0015] Furthermore, the materials for the first and second dielectric layers are Rogers RT 5880.

[0016] Furthermore, the adhesive layer is made of Rogers RO 4450B.

[0017] Furthermore, within the 13.5GHz to 15.5GHz frequency band, by independently adjusting the bias voltage of the varactor diode on the even-mode transmission path, the even mode can achieve a maximum continuous phase shift of 260°, while the odd-mode phase remains unaffected. The phase difference between the second and third ports can be continuously adjusted within the range of 0° to 180°.

[0018] Beneficial Effects: Compared with the prior art, the present invention has the following significant advantages: The present invention utilizes a dual-mode SSPP transmission structure to support the orthogonal parallel transmission of odd-mode and even-mode electromagnetic waves respectively, and uses a Wilkinson power divider at the input port to achieve two-way equal-amplitude and in-phase feeding; wherein, varactor diodes are loaded between the even-mode SSPP units on the even-mode transmission path, and the dispersion characteristics of the even-mode are dynamically controlled by adjusting the bias voltage, so that the even-mode produces continuous phase shift; no control structure is loaded on the odd-mode transmission path, which is only used as a reference transmission line, and its phase remains stable within the operating frequency band; since the electromagnetic field distributions of odd-mode and even-mode are orthogonal, the transmission of the two modes is naturally isolated and does not interfere with each other, and the phase control of the even-mode does not affect the transmission characteristics of the odd-mode. Only the varactor diode on the even-mode side needs to be independently controlled to achieve continuous adjustment of the output phase difference between the second port and the third port; the balun function with continuously adjustable phase difference is realized on a single transmission line, which has the advantages of compact structure, simple control, and high mode isolation, and solves the technical problem that existing adjustable baluns are difficult to balance continuous phase difference control and simple and compact structure. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0020] Figure 2 This is a schematic diagram of the SSPP unit structure of the present invention.

[0021] Figure 3 This invention relates to the effect of the capacitance value of the varactor diode on the odd-even mode dispersion characteristics.

[0022] Figure 4 This is a simulation diagram of the reflection coefficient of the even mode under different states of the varactor diode according to the present invention.

[0023] Figure 5 This is a simulation diagram of the even-mode transmission coefficient of the varactor diode under different conditions according to the present invention.

[0024] Figure 6 This is a simulation diagram of the phase shift of the even mode under different states of the varactor diode according to the present invention.

[0025] Figure 7 This is a simulation diagram of the transmission coefficient of odd mode under different states of the varactor diode according to the present invention.

[0026] Figure 8 This is a simulation diagram of the phase shift of the odd mode under different states of the varactor diode according to the present invention.

[0027] Figure 9 This is a simulation diagram of the phase difference between odd and even modes in different states of the varactor diode according to the present invention.

[0028] Figure 10 This is a simulation diagram of the isolation between odd and even modes of the varactor diode under different conditions according to the present invention.

[0029] The structure includes: 1. Top metal layer; 2. First dielectric layer; 3. Ground layer; 4. Adhesive layer; 5. Second dielectric layer; 6. Bottom metal layer; 1.1 Top 50Ω microstrip line; 1.2 70.7Ω microstrip line; 1.3 100Ω parallel resistor; 1.4 Transition structure; 1.5 Even-mode SSPP unit; 1.5.1 Center conductor; 1.5.2 Parallel stub; 1.5.3 Gap; 1.6 Varactor diode; 1.7 Positive feed structure; 1.8 Negative feed structure; 1.9 Choke structure; 1.10 Through hole; 1.11 First port; 1.12 Second port; 1.13 Third port; 3.1 Odd mode center slot; 3.2 Odd mode coupling circular hole; 3.3 Odd mode SSPP unit; 3.3.1 Symmetrical slot; 6.1 Bottom 50Ω microstrip line; 6.2 Odd mode coupling disc. Detailed Implementation

[0030] like Figure 1 As shown, a phase difference tunable balun based on dual-mode artificial surface plasmons includes: a top metal layer 1, a first dielectric layer 2, a ground layer 3, an adhesive layer 4, a second dielectric layer 5, and a bottom metal layer 6 stacked sequentially from top to bottom.

[0031] The top metal layer 1 includes a first port 11, a second port 12, a third port 13, a top 50Ω microstrip line 1.1, a 70.7Ω microstrip line 1.2, a 100Ω parallel resistor 1.3, a transition structure 1.4, several even-mode SSPP units 1.5, a varactor diode 1.6, a positive electrode feeding structure 1.7, a negative electrode feeding structure 1.8, a choke structure 1.9, and a via 1.10.

[0032] Port 11 is the input port of the balun. The top 50Ω microstrip line 1.1, the 70.7Ω microstrip line 1.2, and the 100Ω parallel resistor 1.3 constitute a Wilkinson power divider. The Wilkinson power divider splits the signal input to port 11 into two signals with equal amplitude and phase. One signal is fed into the even-mode SSPP unit 1.5 through the transition structure 1.4 to excite the even-mode SSPP wave, and the other signal is connected to the bottom 50Ω microstrip line 6.1 through the via 1.10 to excite the odd-mode SSPP wave.

[0033] Transition structure 1.4 is a matching transformation section that connects the even-mode output port of the Wilkinson power divider to the even-mode SSPP unit 1.5 to achieve impedance matching between the two.

[0034] The working principle of this invention is as follows: The input signal enters the Wilkinson power divider through the first port 11 and is split into two equal-amplitude, in-phase signals. The signal in the even-mode branch is impedance matched by the transition structure 1.4, which excites an even-mode SSPP wave, which propagates along the periodic even-mode SSPP unit 1.5 of the top metal layer 1, with an even-symmetric electric field distribution. The signal in the odd-mode branch is fed into the bottom 50Ω microstrip line 6.1 through the via 1.10, and through the electromagnetic coupling of the odd-mode coupling disc 6.2 and the odd-mode coupling via 3.2, an odd-mode SSPP wave is excited, which propagates along the periodic odd-mode SSPP unit 3.3 on the ground layer 3, with an odd-symmetric electric field distribution.

[0035] When different DC bias voltages are applied through the positive-feed structure 1.7, the varactor diode 1.6 on the even-mode transmission path exhibits different capacitance values, changing the equivalent circuit parameters of the even-mode SSPP unit 1.5, thereby dynamically controlling the dispersion characteristics of the even-mode SSPP and causing continuous phase shift in the even mode. There are no control structures on the odd-mode transmission path, so its dispersion characteristics remain fixed, and its phase remains stable. Because the electromagnetic field distributions of the odd and even modes are orthogonal, the transmission of the two modes is naturally isolated, and phase modulation of the even mode does not affect the transmission characteristics of the odd mode.

[0036] like Figure 2As shown, the even-mode SSPP unit 1.5 includes a central conductor 1.5.1, parallel stubs 1.5.2, and a slot 1.5.3. The parallel stubs 1.5.2 are symmetrically loaded on both sides of the central conductor 1.5.1 and extend outward from the central conductor. Several even-mode SSPP units 1.5 are arranged periodically. Adjacent even-mode SSPP units 1.5 are physically isolated from each other through slots 1.5.3 and electrically connected through electromagnetic coupling via the slots.

[0037] A varactor diode 1.6 is laterally connected between adjacent even-mode SSPP units 1.5. The anode of the varactor diode 1.6 is biased via a positive feed structure 1.7, and the cathode is connected to the ground plane 3 via a via a negative feed structure 1.8, forming a complete DC bias circuit. A choke structure 1.9 is located in the DC bias network, employing a fan-shaped stub structure to suppress interference from AC RF signals to the DC bias network, achieving isolation between DC control signals and RF signals. The even-mode signal is transmitted through the even-mode SSPP unit 1.5 and output from the second port 12.

[0038] Ground plane 3 includes odd-mode coupling circular holes 3.2 and odd-mode SSPP units 3.3. An odd-mode central slot 3.1 extends along the length of ground plane 3. The odd-mode SSPP unit 3.3 includes an odd-mode central slot 3.1 and symmetrical slots 3.3.1. The symmetrical slots 3.3.1 are etched on both sides of the odd-mode central slot 3.1, symmetrically distributed to form periodically arranged odd-mode SSPP units 3.3. Odd-mode coupling circular holes 3.2 are located at both ends of ground plane 3 to achieve coupling conversion between the bottom microstrip line mode and the odd-mode SSPP mode. It should be noted that no varactor diodes or other control structures are loaded on the odd-mode transmission path; the odd-mode SSPP unit 3.3 is used only as a transmission line, and its phase remains stable within the operating frequency band.

[0039] The bottom metal layer 6 includes a bottom 50Ω microstrip line 6.1 and an odd-mode coupling disc 6.2. The bottom 50Ω microstrip line 6.1 is connected to the odd-mode output port of the Wilkinson power divider through a via 1.10. The bottom 50Ω microstrip line 6.1 and the odd-mode coupling disc 6.2 are positioned below the odd-mode coupling disc 3.2, and are electromagnetically coupled through the disc 3.2 to convert the bottom microstrip line mode into an odd-mode SSPP mode, thus generating an odd-mode SSPP wave. The odd-mode SSPP wave propagates along the odd-mode SSPP unit 3.3 on the ground plane 3, and its electromagnetic field is odd-symmetric about the ground plane 3. After transmission, the odd-mode signal is converted back to the microstrip line mode at the other end through the same coupling structure and output from the third port 13.

[0040] In this embodiment, the top metal layer 1 and the bottom metal layer 6 are made of copper, the first dielectric layer 2 and the second dielectric layer 5 are made of Rogers RT 5880, and the adhesive layer 4 is made of Rogers RO 4450B. The main parameter settings of the balun are shown in Table 1.

[0041] Table 1 SSPP balun parameter settings

[0042] Top 50 ohm microstrip line width / mm 0.7 Transition structure width / mm 1.8 Choke sector radius / mm 3.2 Center guide band width of the dipole mode / mm 0.6 Even mode guide strip width / mm 0.15 Pair mold gap width / mm 0.15 Even-type branch height / mm 1.2 Even-mode branch width / mm 0.35 Unit period length / mm 3.5 Odd-mode coupling circular hole radius / mm 0.3 Odd-shaped center groove width / mm 0.15 Odd-mode symmetrical groove height / mm 0.925 Odd-mode symmetrical slot width / mm 0.15 50-ohm microstrip line width at the bottom / mm 0.95 Odd-mode coupling disc radius / mm 0.7

[0043] like Figure 3 As shown, the dispersion characteristics of even and odd modes of a varactor diode under different capacitance values ​​are simulated using the CST intrinsic mode solver. It can be observed that as the capacitance value changes, the dispersion curve of the even mode changes significantly, and the phase constant at a fixed frequency point changes accordingly; while the dispersion curve of the odd mode remains unchanged.

[0044] like Figure 4 and Figure 5 As shown, the S-parameters of the even mode under different capacitance values ​​were simulated using the CST time-domain solver. The simulation results show that within the operating frequency band of 13.5 GHz to 15.5 GHz, the reflection coefficient of the even mode is below -13 dB, indicating good impedance matching; the transmission coefficient of the even mode remains above -6 dB, indicating good transmission efficiency.

[0045] like Figure 6 As shown, the phase shift simulation results of the even mode under different capacitance values ​​indicate that the even mode can achieve a maximum continuous phase shift of 260° within the operating frequency band.

[0046] like Figure 7 and Figure 8 As shown, the transmission coefficient and phase shift of the odd mode under different capacitance values ​​are simulated. The simulation results show that during even-mode modulation, the transmission coefficient and phase of the odd mode remain stable within the operating frequency band and are not affected by changes in the bias voltage of the even-mode varactor diode, verifying the independent transmission characteristics of the two modes.

[0047] like Figure 9 As shown, the output phase difference between the second port 12 and the third port 13 is simulated. The simulation results show that by independently adjusting the bias voltage of the varactor diode 1.6 on the even-mode transmission path, the phase difference between the second port 12 and the third port 13 can be continuously adjusted within the range of 0° to 180°, verifying the phase difference control function of the balun.

[0048] like Figure 10 As shown, the isolation between odd and even modes is simulated. The simulation results show that the isolation between odd and even modes is good within the operating frequency band, verifying the orthogonal independent transmission characteristics between the two modes.

[0049] This invention relates to a phase-difference-tunable balun based on dual-mode artificial surface plasmon polaritons (ASPPs). Utilizing a dual-mode SSPP transmission structure, it supports orthogonal parallel transmission of odd and even modes respectively. Combined with a Wilkinson power divider, it achieves equal-amplitude feeding. Continuous adjustment of the phase difference between the two output ports is achieved solely through independent phase modulation using varactor diodes loaded on the even-mode transmission path. This invention features a compact structure, simple control, and good mode isolation, solving the technical problem of existing baluns that struggle to balance continuous phase difference control with a simple and compact structure.

Claims

1. A phase difference-tunable balun based on dual-mode artificial surface plasmons, characterized in that, include: The layers stacked from top to bottom are: a top metal layer, a first dielectric layer, a floor layer, an adhesive layer, a second dielectric layer, and a bottom metal layer. The input signal enters the Wilkinson power divider through the first port and is split into two equal-amplitude, in-phase signals. The signal in the even-mode branch is impedance matched by the transition structure, which excites an even-mode SSPP wave that propagates along the periodic even-mode SSPP unit in the top metal layer, with an even-symmetric electric field distribution. The signal in the odd-mode branch is fed into the bottom 50Ω microstrip line through a via. Through the electromagnetic coupling of the odd-mode coupling disc and the odd-mode coupling aperture, an odd-mode SSPP wave is excited and propagates along the periodic odd-mode SSPP unit on the ground plane, with an odd-symmetric electric field distribution. When different DC bias voltages are applied through the positive electrode feeding structure, the varactor diodes on the even-mode transmission path exhibit different capacitance values, changing the equivalent circuit parameters of the even-mode SSPP unit, thereby dynamically controlling the dispersion characteristics of the even-mode SSPP and causing continuous phase shift in the even mode; the dispersion characteristics on the odd-mode transmission path remain unchanged, and the phase remains stable, realizing continuous adjustment of the output phase difference between the second and third ports.

2. The phase difference tunable balun based on dual-mode artificial surface plasmons as described in claim 1, characterized in that, The top metal layer includes a first port, a second port, a third port, a top 50Ω microstrip line, a 70.7Ω microstrip line, a 100Ω parallel resistor, a transition structure, several even-mode SSPP units, a varactor diode, a positive electrode feed structure, a negative electrode feed structure, a choke structure, and a via. The first port is the input port. The top 50Ω microstrip line, 70.7Ω microstrip line, and 100Ω parallel resistor constitute the Wilkinson power divider. A transition structure connects the even-mode output port of the Wilkinson power divider to the even-mode SSPP unit for impedance matching. A varactor diode is connected across adjacent even-mode SSPP units. A bias voltage is applied through the positive electrode feeding structure to dynamically adjust the dispersion characteristics of the even-mode SSPP and achieve continuous control of the even-mode phase. The negative terminal of the varactor diode is connected to the ground plane through a via via the negative electrode feeding structure to form a DC loop. A choke structure is used to isolate the DC control signal from the RF signal. The odd-mode output port of the Wilkinson power divider is connected to the bottom 50Ω microstrip line through a via. The second port is located at the output end of the even-mode SSPP unit as the even-mode output port.

3. The phase difference tunable balun based on dual-mode artificial surface plasmons as described in claim 2, characterized in that, The choke structure adopts a fan-shaped stub structure to suppress the interference of radio frequency signals on the DC bias network and achieve isolation between DC control signals and radio frequency signals.

4. The phase difference tunable balun based on dual-mode artificial surface plasmons as described in claim 1, characterized in that, The even-mode SSPP unit includes a central conductor, parallel stubs, and gaps; the parallel stubs are symmetrically loaded on both sides of the central conductor; adjacent even-mode SSPP units are physically isolated by gaps to achieve electrical connection.

5. The phase difference tunable balun based on dual-mode artificial surface plasmons as described in claim 1, characterized in that, The ground plane includes odd-mode coupling circular holes and odd-mode SSPP units; the odd-mode SSPP units include odd-mode central slots and symmetrical slots, with symmetrical slots etched on both sides of the odd-mode central slots to form periodically arranged odd-mode SSPP units; the odd-mode central slots extend along the length of the ground plane, and the odd-mode SSPP waves are transmitted along the odd-mode SSPP units on the ground plane, without any varactor diodes or other control structures, and are used only as transmission lines.

6. The phase difference tunable balun based on dual-mode artificial surface plasmons as described in claim 1, characterized in that, The bottom metal layer includes a bottom 50Ω microstrip line and an odd-mode coupling disc; the bottom 50Ω microstrip line is connected to the odd-mode output port of the Wilkinson power divider through a via; the bottom 50Ω microstrip line and the odd-mode coupling disc are coupled through an odd-mode coupling aperture to excite an odd-mode SSPP wave; a third port is located at the output end of the odd-mode SSPP wave, serving as the odd-mode output port; the bottom 50Ω microstrip line and the odd-mode coupling disc in the bottom metal layer are located directly below the odd-mode coupling aperture, and the odd-mode SSPP wave is excited by electromagnetic coupling, realizing the conversion of the odd-mode signal between the bottom microstrip line mode and the odd-mode SSPP mode.

7. The phase difference tunable balun based on dual-mode artificial surface plasmons as described in claim 1, characterized in that, The top and bottom metal layers are made of copper.

8. The phase difference tunable balun based on dual-mode artificial surface plasmons as described in claim 1, characterized in that, The materials for the first and second dielectric layers are Rogers RT 5880.

9. The phase difference tunable balun based on dual-mode artificial surface plasmons as described in claim 1, characterized in that, The adhesive layer material is Rogers RO 4450B.

10. The phase difference tunable balun based on dual-mode artificial surface plasmons as described in claim 1, characterized in that, Within the 13.5GHz to 15.5GHz frequency band, by independently adjusting the bias voltage of the varactor diode on the even-mode transmission path, the even mode can achieve a maximum continuous phase shift of 260°, while the odd-mode phase remains unaffected. The phase difference between the second and third ports can be continuously adjusted within the range of 0° to 180°.

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