Artificial surface plasmon circuit structure supporting odd mode and even mode transmission

Abstract

The invention discloses an artificial surface plasmon circuit structure supporting odd mode and even mode transmission. The circuit structure comprises a dielectric substrate and metal structures on the upper layer and the lower layer of the dielectric substrate. The circuit structure comprises a feed structure, a transition section and an artificial surface plasmon transmission line structure, wherein the feed structure consists of a directional coupler, a phase shifter and a microstrip line; the transition section is designed for realizing mode conversion; in the circuit structure, odd-mode or even-mode transmission can be simply controlled by changing an input port. According to the artificial surface plasmon circuit structure supporting odd mode and even mode transmission, odd modes or even modes can be transmitted on the basis of not changing any circuit structure, the circuit structure is simple, operation is convenient, and the artificial surface plasmon circuit structure has good application prospects in modern communication systems.

Description

Technical Field

[0001] The invention relates to an artificial surface plasmon circuit structure supporting odd-mode and even-mode transmission, belonging to the field of communication and novel artificial electromagnetic technology. Background Art

[0002] Artificial surface plasmons, as a new type of artificial electromagnetic material, are developed from surface plasmons in the optical frequency band and have similar properties to surface plasmons in the optical frequency band: field confinement and field enhancement in the subwavelength range and flexible dispersion control. Artificial surface plasmons are widely used in RF circuit device design, antenna design and communication systems.

[0003] In microwave communications, circuits that support odd and even modes have stronger anti-interference capabilities than single-ended circuits, and can achieve larger bandwidths and higher data transmission rates. However, current research results are limited to a circuit that can only support odd or even mode transmission.

[0004] Therefore, an artificial surface plasmon circuit structure that can support odd-mode and even-mode transmission has great potential application value in the fields of modern communications, which are currently developing at a rapid pace. Summary of the invention

[0005] Purpose: In order to overcome the shortcomings of the prior art, the present invention provides an artificial surface plasmon circuit structure that supports odd-mode and even-mode transmission. Through the design of the feeding structure, transition section and artificial surface plasmon transmission line, it is possible to realize the transmission of different mode signals when different ports are input, that is, odd-mode transmission is performed when the first port inputs a signal; and even-mode transmission is performed when the second port inputs a signal. The circuit structure is easy to manufacture and simple and flexible to operate.

[0006] Technical solution: To solve the above technical problems, the technical solution adopted by the present invention is:

[0007] An artificial surface plasmon circuit structure supporting odd-mode and even-mode transmission comprises a dielectric substrate layer, a metal ground layer is arranged on the lower surface of the dielectric substrate layer, and a metal structure layer is arranged on the upper surface of the dielectric substrate layer.

[0008] The metal structure layer includes: a first feeding structure, a second feeding structure, a first transition section, a second transition section and an artificial surface plasmon transmission line. The entire circuit structure is axially symmetrical with the artificial surface plasmon transmission line. One end of the artificial surface plasmon transmission line is connected to one end of the first transition section, and the other end of the artificial surface plasmon transmission line is connected to one end of the second transition section. The other end of the first transition section is connected to one end of the first feeding structure, and the other end of the second transition section is connected to one end of the second feeding structure.

[0009] As a preferred solution, the first feeding structure and the second feeding structure both include: a directional coupler, a phase shifter, and a first microstrip line, a second microstrip line, a third microstrip line, and a fourth microstrip line. One end of the directional coupler is connected to one end of the first microstrip line and the second microstrip line respectively, the other end of the directional coupler is connected to one end of the third microstrip line and the fourth microstrip line respectively, and one end of the phase shifter is connected to the other end of the third microstrip line and the fourth microstrip line respectively.

[0010] As a preferred solution, the first microstrip line, the second microstrip line, the third microstrip line and the fourth microstrip line are all arranged in a stepped structure.

[0011] As a preferred solution, the phase shifter includes an upper branch of an "X-shaped" microstrip line structure and a lower branch of a straight microstrip line structure.

[0012] As a preferred solution, the first transition section and the second transition section both include: a fifth microstrip line and a sixth microstrip line, the fifth microstrip line and the sixth microstrip line are arranged up and down, and artificial surface plasmon transition sections are provided at the ends of the fifth microstrip line and the sixth microstrip line, and the artificial surface plasmon transition section includes a plurality of artificial surface plasmon units arranged in sequence, and the tooth depths of the plurality of artificial surface plasmon units are set to different depths.

[0013] As a preferred solution, the tooth depths of the plurality of artificial surface plasmon units increase sequentially from one end of the fifth microstrip line and the sixth microstrip line toward the other side.

[0014] As a preferred solution, the artificial surface plasmon transmission line includes a plurality of artificial surface plasmon units arranged in sequence.

[0015] As a preferred solution, the artificial surface plasmon unit includes "cross"-shaped artificial surface plasmons arranged at intervals at the top and bottom.

[0016] As a preferred solution, the plasmon unit is axisymmetric about the vertical axis Φ3 and axisymmetric about the horizontal axis λ2.

[0017] As a preferred solution, the artificial surface plasmon transmission line uses 16 artificial surface plasmon units, and the artificial surface plasmon transition section uses 6 artificial surface plasmon units.

[0018] Beneficial effects: The present invention provides an artificial surface plasmon circuit structure that supports odd-mode and even-mode transmission, including a feeding structure, a transition section designed to achieve mode conversion, and an artificial surface plasmon transmission line; the feeding structure includes a directional coupler, a phase shifter, and a microstrip line; the unit structure of the artificial surface plasmon transmission line is composed of two identical "cross" shaped metal structures; the transition section designed to achieve mode conversion is composed of artificial surface plasmons with different tooth heights. The artificial surface plasmon circuit structure that supports odd-mode and even-mode transmission proposed by the present invention can achieve odd-mode and even-mode transmission without changing any circuit structure, and the transmission of different modes only requires changing the input port. Its advantages are as follows:

[0019] 1. The present invention is simple in design and convenient in processing and assembly. The present invention can be processed by using mature PCB processing technology.

[0020] 2. The artificial surface plasmon transmission line designed by the present invention has a stronger field confinement capability than the traditional transmission line, no crosstalk will occur between the transmission lines, and the size of the circuit structure can be effectively reduced.

[0021] 3. The feeding structure designed in the present invention can realize transmission of different modes (odd mode or even mode) through input from different ports (first port or second port) without changing any circuit structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the overall structure of the artificial surface plasmon circuit of the present invention.

[0023] Figure 2 It is a structural diagram of the feeding structure.

[0024] Figure 3 It is a structural diagram of the transition section.

[0025] Figure 4 It is a three-dimensional schematic diagram of the artificial surface plasmon unit.

[0026] Figure 5 This is a top-down schematic diagram of an artificial surface plasmon unit.

[0027] Figure 6 This is a schematic diagram of the port settings of the artificial surface plasmon circuit.

[0028] Figure 7 Schematic diagram of the dispersion curve simulation results of the artificial surface plasmon unit.

[0029] Figure 8 are the S parameters and phase difference of the feeding structure of the present invention, where, Figure 8(a) is the S parameter of the feeding structure when the first microstrip line is used as the first port input signal. Figure 8 (b) shows the phase difference between the third port and the fourth port when the first microstrip line is used as the first port input signal. Figure 8 (c) is the S parameter of the feeding structure when the second microstrip line is used as the second port input signal. Figure 8 (d) in the middle is the phase difference between the third port and the fourth port when the second microstrip line is used as the input signal of the second port.

[0030] Fig. 9 is the S parameter of the overall circuit structure of the present invention at different port inputs at a frequency of 17-18 GHz, wherein, Fig. 9 (a) is the S parameter of the entire circuit structure during odd-mode transmission when the first port is input. Fig. 9 (b) shows the S parameters of the entire circuit structure during even-mode transmission when the second port is input, including simulation results and test results. DETAILED DESCRIPTION

[0031] The following is a clear and complete description of the technical solutions in the examples of the present invention in conjunction with the accompanying drawings in the examples of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the protection scope of the present invention.

[0032] The present invention will be further described below in conjunction with specific embodiments.

[0033] Embodiment 1:

[0034] This embodiment introduces an artificial surface plasmon circuit structure that supports odd-mode and even-mode transmission, such as Figure 1 As shown, it includes: a dielectric substrate layer 1, a metal ground layer arranged on the lower surface of the dielectric substrate layer 1, and a metal structure layer 2 arranged on the upper surface of the dielectric substrate layer 1.

[0035] The metal structure layer 2 includes: a first feeding structure 2-1, a second feeding structure 2-5, a first transition section 2-2 designed to achieve mode conversion, a second transition section 2-4 and an artificial surface plasmon transmission line 2-3. The entire circuit structure is axially symmetrical with the artificial surface plasmon transmission line 2-3 as the center. One end of the artificial surface plasmon transmission line 2-3 is connected to one end of the first transition section 2-2, and the other end of the artificial surface plasmon transmission line 2-3 is connected to one end of the second transition section 2-4. The other end of the first transition section 2-2 is connected to one end of the first feeding structure 2-1, and the other end of the second transition section 2-4 is connected to one end of the second feeding structure 2-5.

[0036] Further, an embodiment, such as Figure 2 As shown, the first feeding structure 2-1 and the second feeding structure 2-5 both include: a directional coupler 2-1-1, a phase shifter 2-1-2, and a first microstrip line 2-1-3, a second microstrip line 2-1-4, a third microstrip line 2-1-5, and a fourth microstrip line 2-1-6 connected thereto, one end of the directional coupler 2-1-1 being respectively connected to one end of the first microstrip line 2-1-3 and one end of the second microstrip line 2-1-4, the other end of the directional coupler 2-1-1 being respectively connected to one end of the third microstrip line 2-1-5 and one end of the fourth microstrip line 2-1-6, and one end of the phase shifter 2-1-2 being respectively connected to the other end of the third microstrip line 2-1-5 and the fourth microstrip line 2-1-6.

[0037] Furthermore, in one embodiment, the directional coupler 2-1-1 is axisymmetric about the vertical axis Φ1 and axisymmetric about the horizontal axis λ1. The phase shifter 2-1-2 is axisymmetric about the vertical axis Φ2.

[0038] Furthermore, in one embodiment, the first microstrip line 2-1-3 and the second microstrip line 2-1-4 are axially symmetrical about the horizontal axis λ1, and the third microstrip line 2-1-5 and the fourth microstrip line 2-1-6 are axially symmetrical about the horizontal axis λ1.

[0039] Furthermore, in one embodiment, the first microstrip line 2-1-3, the second microstrip line 2-1-4, the third microstrip line 2-1-5 and the fourth microstrip line 2-1-6 are arranged in a stepped structure to achieve impedance matching.

[0040] Furthermore, in one embodiment, the phase shifter 2-1-2 includes an upper branch of an "X-shaped" microstrip line structure and a lower branch of a straight microstrip line structure.

[0041] Further, an embodiment, such as Figure 3 As shown, the first transition section 2-2 and the second transition section 2-4 both include: a fifth microstrip line 2-2-1 and a sixth microstrip line 2-2-2, the fifth microstrip line 2-2-1 and the sixth microstrip line 2-2-2 are arranged up and down, and artificial surface plasmon transition sections 2-2-3 are provided at the ends of the fifth microstrip line 2-2-1 and the sixth microstrip line 2-2-2, and the artificial surface plasmon transition section 2-2-3 includes a plurality of plasmon units 2-3-1 arranged in sequence, and the tooth depths 2-2-3-1 of the plurality of plasmon units 2-3-1 are set to different depths.

[0042] Furthermore, in one embodiment, six plasmon units 2-3-1 are arranged on the artificial surface plasmon transition section 2-2-3, and the tooth depth 2-2-3-1 of the six plasmon units 2-3-1 increases successively from one end of the fifth microstrip line 2-2-1 and the sixth microstrip line 2-2-2 to the other side.

[0043] Further, an embodiment, such as Figure 4 As shown, the artificial surface plasmon transmission line 2-3 includes a plurality of plasmon units 2-3-1 arranged in sequence, and the plasmon unit 2-3-1 includes "cross"-shaped artificial surface plasmons 2-3-1-1 arranged at intervals above and below.

[0044] Further, an embodiment, such as Figure 5 As shown, the plasmon unit 2 - 3 - 1 is axially symmetrical about the vertical axis Φ3 and axially symmetrical about the horizontal axis λ2.

[0045] Furthermore, in one embodiment, the number of the plasmon units 2-3-1 is set to 16.

[0046] Further, an embodiment, such as Figure 6 As shown, the first microstrip line 2-1-3 of the first feeding structure 2-1 is used as the first port, the second microstrip line 2-1-4 of the first feeding structure 2-1 is used as the second port, the third microstrip line 2-1-5 of the first feeding structure 2-1 is used as the third port, and the fourth microstrip line 2-1-6 of the first feeding structure 2-1 is used as the fourth port. The third microstrip line 2-1-5 of the second feeding structure 2-5 is used as the fifth port, and the fourth microstrip line 2-1-6 of the second feeding structure 2-5 is used as the sixth port.

[0047] Furthermore, in one embodiment, the dielectric substrate 1 is configured as a rectangular parallelepiped structure.

[0048] Embodiment 2:

[0049] This embodiment introduces an embodiment of an artificial surface plasmon circuit structure that supports odd-mode and even-mode transmission. In this embodiment, the dimensions of each component of the directional coupler 2-1-1 are: a = 0.68 mm, b = 1.003 mm, c = 3.1 mm, d = 3.4 mm, l2 = 9.4 mm, where a is the width of the arm structure of the directional coupler, b is the width of the long frame structure of the directional coupler, c is the inner cavity height of the long frame structure of the directional coupler, d is the length of the long frame structure of the directional coupler, and l2 is the length of the directional coupler. The four arm structures of the directional coupler are axially symmetrical about the axis Φ1 and the axis λ1.

[0050] The dimensions of the components of the phase shifter 2-1-2 are: l4 = 4.5 mm, l5 = 4.4 mm, l6 = 15 mm, w2 = 6 mm, w3 = 1.52 mm, x = 1.5 mm, where l4 is the length of the horizontal microstrip line at one end of the "J-shaped" microstrip line structure, l5 is the length of the upper end microstrip line of the "J-shaped" microstrip line, l6 is the length of the straight microstrip line structure, w2 is the spacing between the "J-shaped" microstrip line structure and the straight microstrip line structure, w3 is the width of the horizontal microstrip line at one end of the "J-shaped" microstrip line structure, and x is the length of the inner angle of the "J-shaped" microstrip line structure.

[0051] In order to experimentally test the impedance matching of the port, such as 50 ohm matching, the dimensions of the microstrip line of the feeding structure are: l1 = 9 mm, w1 = 8.12 mm, l3 = 5 mm, where l1 is the distance between the beginning and the end of the first microstrip line or the second microstrip line, w1 is the distance between the beginning and the end of the first microstrip line and the second microstrip line, and l3 is the distance between the beginning and the end of the third microstrip line or the fourth microstrip line.

[0052] Artificial surface plasmon transmission is a special TM mode and cannot directly transition from the TEM mode of the microstrip line. Therefore, a progressive artificial surface plasmon transition section is designed to achieve mode conversion, in which the depth h of the tooth depth changes in steps of 0.09 mm. The microstrip line transition section is used to achieve impedance matching between the transition section and the phase shifter. The dimensions of each component of the transition section are p1 = 2 mm, p2 = 2 mm, and h6 = 0.507 mm, in which p1 is the length of the fifth microstrip line or the sixth microstrip line, p2 is the width of the fifth microstrip line or the sixth microstrip line, and h6 is the depth of the tooth depth of the sixth plasmon unit.

[0053] The thickness of the dielectric substrate layer is Rogers RT5880, which is 0.508 mm, has a relative dielectric constant of 2.2 and a loss tangent of 0.0009.

[0054] The structure of the artificial surface plasmon unit is a symmetrical "cross" shaped metal structure, consisting of two "cross" shaped artificial surface plasmons, where l = 2.4 mm, w = 1.52 mm, s = 0.39 mm, p = 0.6 mm, h = 0.51mm, and b = 0.508 mm, where l is the length period of the plasmon unit, w is the width of the "cross" shaped artificial surface plasmon, s is the spacing between the two "cross" shaped artificial surface plasmons, p is the length of the tooth depth of the "cross" shaped artificial surface plasmon, h is the depth of the tooth depth of the "cross" shaped artificial surface plasmon, and b is the thickness of the dielectric substrate layer.

[0055] The artificial surface plasmon unit and the metal layer are both made of metallic copper, with a thickness of t = 0.035 mm.

[0056] The eigenmode solver of the simulation software can be used to simulate the dispersion curve of the plasmon unit under this parameter, such as Figure 7 As shown in the figure, the simulation results prove that: (1) the designed plasmon unit itself can support both odd and even modes; (2) the odd-mode cutoff frequency is slightly lower than the even-mode cutoff frequency, indicating that the field binding of the odd mode is stronger; (3) the plasmon unit is at a high cutoff frequency (above 20 GHz), which lays the foundation for the design of the entire circuit structure.

[0057] When an artificial surface plasmon circuit structure supporting odd-mode and even-mode transmission is used, when an input signal is input through a first port, a directional coupler converts the input signal into a differential signal, and the differential signal becomes a required odd-mode signal after a phase shifter, and the generated odd-mode signal is then transmitted through an artificial surface plasmon transmission line, and finally the odd-mode signal is coupled back to a single-port output through a transition section and a feeding structure; when an input signal is input through a second port, a directional coupler converts the input signal into a differential signal, and the differential signal becomes a required even-mode signal after a phase shifter, and the generated even-mode signal is then transmitted through an artificial surface plasmon transmission line, and finally the even-mode signal is coupled back to a single-port output through a transition section and a feeding structure. The feeding structure can realize the transmission of signals of different modes when different ports are input, that is, when the first port is input, the entire circuit structure transmits an odd-mode signal (phase difference of 180°), and when the second port is input, the entire circuit structure transmits an even-mode signal (phase difference of 0°).

[0058] like Figure 8 As shown, the simulation results of the feeding structure with the first port as the excitation source are as follows Figure 8 As shown in (a) and 8 (b), the designed feeding structure has good transmission at 17-18 GHz, and can achieve a phase shift performance of 180°±10° in the frequency band of 17-18 GHz, that is, the first port can achieve odd-mode feeding in the range of 17-18 GHz; similarly, the simulation results of the second port as an excitation source are shown in Figure 8 As shown in (c) and 8 (d), the feeding structure can achieve good transmission in the range of 17-18 GHz, and the phase difference between the third port and the fourth port is maintained at 0°±15° in the range of 17-18 GHz. It can be seen that the second port can achieve even-mode feeding in the range of 17-18 GHz. In summary, the designed feeding structure can perform both odd-mode feeding and even-mode feeding in the working frequency band of 17-18 GHz, which proves the rationality of the design of the present invention.

[0059] like Fig. 9 As shown, Fig. 9(a) and Fig. 9 (b) shows the S parameter diagram of the entire circuit structure under the excitation of the first port and the second port, including simulation results and test results. It can be seen that under the excitation of the first port or the second port, the reflection coefficient S 11 or S 22 It is lower than -10 dB in the frequency band, which means that the reflected energy is less than 10%, proving that the reflection of the entire designed circuit structure is small. From the figure, it can be seen that within 17-18 GHz, the simulation and test results of the two-port excitation both show good transmission characteristics. The specific transmission situation is: first, the directional coupler converts the single-port input signal into a differential signal, and the differential signal becomes the required odd-mode or even-mode signal after the phase shifter. The generated odd-mode and even-mode signals are then transmitted through the artificial surface plasmon transmission line, and finally the signal is coupled back to the single-port signal output through the phase shifter and directional coupler with the same feeding structure. The simulation data is in good agreement with the test data.

[0060] In summary, the artificial surface plasmon circuit structure supporting odd-mode and even-mode transmission proposed in the present invention realizes the transmission of both odd-mode and even-mode modes without changing the circuit structure.

[0061] The circuit structure includes a dielectric substrate and two metal structures above and below it; the circuit structure includes a feeding structure composed of a directional coupler and a phase shifter, a transition section designed to achieve mode conversion, and an artificial surface plasmon transmission line structure. In the circuit structure, odd-mode or even-mode transmission can be controlled simply by changing the input port. The artificial surface plasmon circuit structure supporting odd-mode and even-mode transmission proposed by the present invention can transmit odd-mode and even-mode without changing any circuit structure, and the circuit structure is simple and easy to operate, and has good application prospects in modern communication systems.

[0062] The circuit design of the present invention improves the flexibility and efficiency of the circuit and broadens the application field of the artificial surface plasmon transmission line.

[0063] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An artificial surface plasmon circuit structure supporting odd-mode and even-mode transmission, characterized in that: include: A dielectric substrate layer, wherein a metal ground layer is disposed on the lower surface of the dielectric substrate layer, and a metal structural layer is disposed on the upper surface of the dielectric substrate layer; The metal structure layer includes: a first feeding structure, a second feeding structure, a first transition section, a second transition section and an artificial surface plasmon transmission line. The entire circuit structure is axially symmetrical with the artificial surface plasmon transmission line. One end of the artificial surface plasmon transmission line is connected to one end of the first transition section, and the other end of the artificial surface plasmon transmission line is connected to one end of the second transition section; the other end of the first transition section is connected to one end of the first feeding structure, and the other end of the second transition section is connected to one end of the second feeding structure.

2. The artificial surface plasmon circuit structure supporting odd-mode and even-mode transmission according to claim 1, characterized in that: The first feeding structure and the second feeding structure both include: a directional coupler, a phase shifter, and a first microstrip line, a second microstrip line, a third microstrip line, and a fourth microstrip line. One end of the directional coupler is connected to one end of the first microstrip line and one end of the second microstrip line, respectively, and the other end of the directional coupler is connected to one end of the third microstrip line and one end of the fourth microstrip line, respectively. One end of the phase shifter is connected to the other end of the third microstrip line and the fourth microstrip line, respectively.

3. The artificial surface plasmon circuit structure supporting odd-mode and even-mode transmission according to claim 2, characterized in that: The first microstrip line, the second microstrip line, the third microstrip line and the fourth microstrip line are all arranged in a stepped structure.

4. The artificial surface plasmon circuit structure supporting odd-mode and even-mode transmission according to claim 2, characterized in that: The phase shifter comprises an upper branch of a "X-shaped" microstrip line structure and a lower branch of a straight microstrip line structure.

5. The artificial surface plasmon circuit structure supporting odd-mode and even-mode transmission according to claim 1, characterized in that: The first transition section and the second transition section both include: a fifth microstrip line and a sixth microstrip line, the fifth microstrip line and the sixth microstrip line are arranged up and down, and artificial surface plasmon transition sections are provided at the ends of the fifth microstrip line and the sixth microstrip line, and the artificial surface plasmon transition section includes a plurality of plasmon units arranged in sequence, and the tooth depths of the plurality of artificial surface plasmon units are set to different depths.

6. The artificial surface plasmon circuit structure supporting odd-mode and even-mode transmission according to claim 5, characterized in that: The tooth depths of the plurality of artificial surface plasmon units increase sequentially from one end of the fifth microstrip line and the sixth microstrip line to the other side.

7. The artificial surface plasmon circuit structure supporting odd-mode and even-mode transmission according to claim 1, characterized in that: The artificial surface plasmon transmission line comprises a plurality of artificial surface plasmon units arranged in sequence.

8. An artificial surface plasmon circuit structure supporting odd-mode and even-mode transmission according to claim 5 or 7, characterized in that: The artificial surface plasmon unit comprises artificial surface plasmons in a cross shape which are arranged at intervals at the top and the bottom.

9. The artificial surface plasmon circuit structure supporting odd-mode and even-mode transmission according to claim 8, characterized in that: The artificial surface plasmon unit is axisymmetric about the vertical axis Φ3 and axisymmetric about the horizontal axis λ2.

10. An artificial surface plasmon circuit structure supporting odd-mode and even-mode transmission according to claim 5 or 7, characterized in that: The artificial surface plasmon transmission line adopts 16 artificial surface plasmon units, and the artificial surface plasmon transition section adopts 6 artificial surface plasmon units.

Images