Periodically loaded ring-mushroom structure fsiw transmission line

Abstract

The application discloses a FSIW transmission line with periodic loading ring-mushroom structure, which comprises a top metal layer, a middle metal layer, a bottom metal layer, a dielectric layer and a metalized via array; the FSIW is connected to a 50-ohm strip line through a trapezoidal transition zone. The application has the following advantages: a periodic ring-mushroom structure array is loaded in the middle metal layer of the FSIW, thereby avoiding the radiation loss of the ring-mushroom structure and maintaining the shielding property of the FSIW; the ring-mushroom structure in the FSIW has a strong slow wave effect, thereby reducing the size of the FSIW; and the transition structure between the 50-ohm strip line and the FSIW widens the bandwidth of the transmission line.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of microwave technology, and relates to a folded substrate integrated waveguide (FSIW) transmission line with a periodically loaded ring-mushroom structure. BACKGROUND

[0002] Planar transmission lines, such as microstrip lines and coplanar waveguides (CPW), are basic components of radio frequency and microwave circuits and systems. Compared with traditional metal waveguides, planar transmission lines have the advantages of small size, convenient system integration and circuit design, etc. However, due to the semi-open electromagnetic field structure of these planar circuits, as the operating frequency increases, there will be electromagnetic radiation and leakage that cannot be ignored, resulting in signal integrity problems such as delay, attenuation, crosstalk, etc. Substrate integrated waveguide (SIW) combines the respective advantages of traditional metal waveguides and planar transmission lines. Compared with metal waveguides, the size is greatly reduced, and compared with planar transmission lines, it has lower loss. SIW is widely used in high-frequency fields (above 10 GHz) due to its small size, low loss, and compatibility with planar circuits. However, due to the size, the application of SIW in low-frequency fields has been limited. To solve this problem, half-mode substrate integrated waveguide (HMSIW) and folded substrate integrated waveguide (FSIW) have emerged. These two technologies can reduce the transverse size by 50%. However, HMSIW introduces additional radiation loss due to its semi-open structure. In contrast, FSIW can reduce the size without significantly changing the transmission performance due to its closed structure.

[0003] Another method to reduce the size of SIW is to use a slow wave structure. In 2014, the concept of slow wave SIW (SW-SIW) was first proposed. This SW-SIW structure requires a double-layer dielectric substrate, where a uniform array of metalized vias is arranged in the lower dielectric substrate to connect with the bottom metal layer. When electromagnetic waves propagate in it, the electromagnetic field can be effectively separated, and a slow wave effect can be obtained. This slow wave effect is equivalent to increasing the dielectric constant of the substrate material, thereby obtaining a smaller cutoff frequency at the rated transverse width and a larger propagation phase at the rated longitudinal length. Compared with traditional SIW, SW-SIW can achieve synchronous reduction of transverse and longitudinal dimensions. A year later, a new structure combining this structure with HMSIW was proposed. The new structure is achieved by cutting the structure into two identical parts in the transverse direction based on the structure. The new structure combines the advantages of HMSIW and SW-SIW, further reducing the size of SIW. However, due to the semi-openness of HMSIW, more radiation loss is introduced, and the closed structure of SIW is also destroyed, resulting in poorer shielding performance.

[0004] In view of the problems of high loss and poor shielding performance of the HMSIW loaded with the metalized via array, the ring-mushroom structure is combined with the FSIW in the application. The ring-mushroom structure is located in the middle layer, and the metalized vias in the ring-mushroom structure are distributed in the upper and lower layers of dielectric, and the upper and lower metal and the metalized via array on the left and right sides form a closed structure. Since the ring-mushroom structure is loaded in the transmission line, the slow wave effect is formed, so the longitudinal and transverse dimensions of the FSIW can be reduced; the application is a closed structure, so the loss is lower. Therefore, the application has the characteristics of small size, wide passband and full closure. SUMMARY

[0005] The application aims to overcome the shortcomings of the prior art and provides a FSIW transmission line periodically loaded with a ring-mushroom structure, which has the advantages of small size, wide passband and full closure.

[0006] The application adopts the following technical scheme:

[0007] A FSIW transmission line periodically loaded with a ring-mushroom structure, comprising:

[0008] a dielectric layer;

[0009] a top metal layer located on the upper surface of the dielectric layer;

[0010] a bottom metal layer located on the lower surface of the dielectric layer;

[0011] a middle metal layer located in the dielectric layer;

[0012] two rows of first metalized via arrays arranged in parallel, which penetrate the dielectric layer, and the two ends of each metalized via are connected with the top metal layer and the bottom metal layer respectively;

[0013] wherein:

[0014] the middle metal layer comprises a plurality of periodically arranged ring-mushroom structures, trapezoidal transition strips and strip lines; one side of the periodically arranged ring-mushroom structure is connected with one row of the first metalized via arrays, and the other side is not in contact with the other row of the first metalized via arrays;

[0015] a single ring-mushroom structure comprises a square metal patch, a square metal ring and a center metalized via; the square metal patch is inlaid in the interior of the square metal ring and is connected to the top metal layer and the bottom metal layer through the center metalized via; wherein a certain gap is left between the square metal ring and the square metal patch;

[0016] the two ends of the middle metal layer are respectively connected with one end of a trapezoidal transition strip, and the other end of the two trapezoidal transition strips is respectively connected with one end of a strip line.

[0017] As preferred, the width W of the square metal ring in the ring-mushroom structure is adjusted by regulating the width W of the passageway formed by the two rows of first metallized via arrays s , the width W of the square metal ring in the ring-mushroom structure g , the gap distance s between the square metal ring and the square metal patch in the ring-mushroom structure, and further the cutoff frequency of the FSIW.

[0018] As preferred, the plurality of ring-mushroom structures are periodically distributed in a 3x12 array.

[0019] As preferred, the square metal ring of the ring-mushroom structure near the crease (i.e. the side not in contact with the first metallized via array) is elongated in the direction of the crease by a certain width.

[0020] As preferred, the geometric centers of the square metal ring, the square metal patch, and the center metallized via coincide.

[0021] As preferred, the stripline adopts a 50-ohm impedance.

[0022] As preferred, the distance d between the trapezoidal transition strip and the crease in , d in affects the in-band S parameters and widens the relative bandwidth.

[0023] As preferred, the distance between the middle metal layer and the top metal layer and the bottom metal layer is equal.

[0024] As preferred, the dielectric layer is formed by stacking two dielectric substrates on top of each other, with the middle metal layer located between the two dielectric substrates; more preferably, the dielectric substrate adopts a Tanconic TLY-5 dielectric substrate with a relative permittivity of 2.2, a loss tangent of 0.0009, and a thickness of 0.508 mm.

[0025] As preferred, the passband of the periodically loaded ring-mushroom FSIW is set around 6.5 GHz.

[0026] As preferred, the center lines of the two trapezoidal transition strips and the two striplines are located on the same straight line.

[0027] The other ends of the two striplines are respectively the first port and the second port; in actual applications, the stripline ports can be further converted into microstrip, coplanar waveguide, or other ports through other switching structures, but this is not within the scope of protection of the present application.

[0028] Working principle:

[0029] When a signal is input from the first port, it is transmitted in the FSIW as a TE 0.5,0 mode, with the electric field direction along the y-axis direction. For the TE 0.5,0Any xoz plane inside the FSIW can be equivalent to an ideal electric wall, so the middle metal layer of the FSIW does not affect the TE 0.5,0 The first array of metalized vias is equivalent to an ideal electric wall, and the middle metal layer is connected to the first array of metalized vias on one side and not connected to the first array of metalized vias on the other side, resulting in the upper and lower layers of the FSIW being connected, and energy can propagate in both the upper and lower layers, which is equivalent to reducing the lateral size of the SIW by 50%. Since the SIW and the FSIW are both closed structures, their performances are basically the same. In addition, since the upper and lower layers of the FSIW are identical, the electric field distribution of the upper and lower layers is also the same.

[0030] When the signal is transmitted in the ring-mushroom structure, the top metal layer and the bottom metal layer can be equivalent to ground, and since the square metal patch in the ring-mushroom structure is connected to the top metal layer and the bottom metal layer through the center metalized via, the square metal patch in the ring-mushroom structure has a higher potential than the top metal layer and the bottom metal layer. Therefore, the square metal patch in the ring-mushroom structure, the top metal layer, the bottom metal layer, and the dielectric layer can be equivalent to a capacitor, increasing the capacitive effect of the transmission line. At the same time, the square metal ring in the ring-mushroom structure is connected to the upper and lower metal layers through the first array of metalized vias on one side, and since the square metal patch in the ring-mushroom structure and the square metal ring have different grounding paths, their potentials are also different. The square metal patch in the ring-mushroom structure, the dielectric layer, and the square metal ring in the ring-mushroom structure can be equivalent to a capacitor, also increasing the capacitive effect of the transmission line. When multiple ring-mushroom structures are connected, it is equivalent to multiple capacitors in parallel.

[0031] Normally, the equivalent dielectric constant of a dielectric is equal to the dielectric constant of the dielectric itself. However, by changing the structure to enhance the capacitive effect of the transmission line, it is equivalent to increasing the equivalent dielectric constant of the dielectric. The lateral size of the transmission line is inversely proportional to the equivalent dielectric constant of the dielectric, so the lateral size of the transmission line can be reduced. The speed of electromagnetic waves propagating in different media is inversely proportional to the equivalent dielectric constant of the dielectric, so this structure can also reduce the transmission speed of electromagnetic waves and reduce the longitudinal size of the transmission line.

[0032] Since the FSIW has the advantages of wide bandwidth and low loss, loading the ring-mushroom structure can form a slow wave effect, and the longitudinal and lateral sizes of the transmission line are reduced at the same time, so the present application has the characteristics of small size, wide passband, and full sealing.

[0033] The present application has the following advantages:

[0034] (1) Compared with the traditional FSIW transmission line, the periodic loading of the ring-mushroom structure reduces the lateral size and longitudinal size of the transmission line by 32.5% and 41%, respectively;

[0035] (2) The transmission line structure of the present application is completely closed, has good shielding property, is not easily affected by external complex electromagnetic environment, and avoids crosstalk with other transmission lines;

[0036] (3) The transmission line has wideband characteristics, and the relative bandwidth of -20 dB is as high as 68%. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 is a three-dimensional schematic view of the FSIW transmission line of the present application;

[0038] Figure 2 (a) and (b) are respectively a top view and a side view of the FSIW transmission line of the present application;

[0039] Figure 3 (a), (b) and (c) are respectively a three-dimensional electric field amplitude distribution diagram of the FSIW transmission line when a signal is input from the first port, and cross-sectional electric field and magnetic field amplitude distribution diagrams at AA'.

[0040] Figure 4 is a simulation result of the dispersion characteristics of the unit structure and the FSIW of the same size.

[0041] Figure 5 (a) and (b) are simulation results of the S parameters and the attenuation constant of the present application. DETAILED DESCRIPTION

[0042] The present application will be further described below in conjunction with the drawings.

[0043] Figure 1 is a periodic ring-mushroom structure transmission line provided by the present application, comprising a top metal layer 1, a middle metal layer 2, a bottom metal layer 3, a dielectric layer 4, two rows of first metallized via arrays 5, a first port 6, and a second port 7.

[0044] The length and width of the dielectric layer 4 extend along the y-axis and the x-axis respectively, and the upper and lower thicknesses extend along the z-axis, and the x, y and z axes form an orthogonal coordinate system.

[0045] The middle metal layer 2 comprises a periodic ring-mushroom array 2a, a trapezoidal transition strip 2b, and a 50-ohm strip line 2c; one side of the periodic ring-mushroom array 2a is connected to one row of first metallized via arrays 5a distributed along the x-axis, and the other side edge is not in contact with the other row of first metallized via arrays 5b along the x-axis. Therefore, the middle metal layer 2, in combination with the top metal layer 1 and the bottom metal layer 3 and the first metallized via arrays 5, jointly constructs an FSIW, and the side not in contact with the first metallized via arrays 5b is a fold of the FSIW; the FSIW is connected to the 50-ohm strip line 2c through the trapezoidal transition strip 2b; the first port 6 and the second port 7 are strip line ports.

[0046] Table 1 Size parameters of FSIW transmission line in this embodiment (unit: mm)

[0047] a s [WC g ]]> d in ]]> d [WC s ]]> 3 0.2 0.1 1.6 0.4 10 d1 d x ]]> d x1 ]]> h d p ]]> 0.5 0.2 0.2 0.508 0.1

[0048] wherein a represents the y-axis width of a single ring-mushroom structure, s represents the gap distance between the square metal ring and the square metal patch in the ring-mushroom structure, W g represents the line width of the square metal ring, d in represents the distance between the trapezoidal transition strip and the outer edge of the square metal ring, d s represents the diameter of the central metalized via, W x represents the distance between the first metalized via array 5 not in contact with the periodic ring-mushroom array 2a and the square metal patch, d x1 represents the distance between the first metalized via array 5 connected with the periodic ring-mushroom array 2a and the square metal patch, 2h represents the thickness of the dielectric layer 4, d p represents the width of the square metal ring of the ring-mushroom structure elongated in the direction of the fold near the fold.

[0049] Figure 2 (a), (b) are top view and side view of the present application. The main part of the periodic ring-mushroom structure transmission line provided by the present application is composed of a plurality of identical unit structures arranged periodically and seamlessly connected. Each unit structure contains 3 ring-mushroom structures of the same size arranged longitudinally and seamlessly connected. A single ring-mushroom structure includes a square metal ring 2a1, a square metal patch 2a2, and a central metalized via 2a3. The central metalized via 2a3 penetrates through the entire dielectric layer and is connected with the top metal layer and the bottom metal layer. The outer diameter of the square metal ring in the ring-mushroom structure is a, the ring width is W g , and the gap between the square metal ring and the square metal patch in the ring-mushroom structure is s, s and W g mainly affect the cutoff frequency of the transmission line. In order to reduce the error in the process, the outer ring of the ring-mushroom structure near the fold is elongated in the direction of the fold by d p . The trapezoidal transition strip 2b is connected with the middle metal layer at a distance d in from the FSIW fold, d in mainly affects the S parameter in the band and widens the relative bandwidth.

[0050] The right-angle trapezoidal trapezoidal transition strip 2b is connected with the ring-mushroom structure at the lower base, connected with the 50-ohm strip line 2c at the upper base, and the right-angle side is close to the FSIW fold.

[0051] The thickness of the upper and lower dielectric layers is the same. The thickness h of the dielectric substrate and the size a of a single ring-mushroom structure together determine the frequency band applicable to the ring-mushroom structure.

[0052] Figure 3 (a), (b), and (c) are the three-dimensional electric field amplitude distribution diagrams of the transmission line when signals are input from the first and second ports, and the cross-sectional electric and magnetic field amplitude distribution diagrams at point AA'. First, as can be seen from the diagrams, the electric field is completely confined inside the transmission line, with the strongest electric field near the gap. The field strength decreases along the x-direction and is almost uniformly distributed along the y-direction, which is consistent with the TE in FSIW. 0.5,0 The mode field distribution is similar; secondly, it can be observed that the electric field is concentrated around the intermediate metal layer, which indicates that the electric field is enhanced and the equivalent parallel capacitance of the transmission line is enhanced; finally, from the electric field and magnetic field distribution at the cross section at AA', it can be found that the electric field and magnetic field are separate, the electric field is distributed around the intermediate metal layer, while the magnetic field is distributed in the medium. The separation of the electric field and magnetic field in space is a typical phenomenon of the slow wave effect.

[0053] Figure 4 These are simulation results of the unit structure of the present invention and the dispersion characteristics of an FSIW of the same size, wherein V c The speed of light is used. As shown in the figure, the cutoff frequency of this invention is 3.46 GHz, which is 32.5% lower than that of an FSIW of the same size (5.12 GHz), meaning the lateral dimension can be reduced by 32.5%. At the same time, when the normalized phase velocity of the FSIW of the same size is 1, the normalized phase velocity of this invention is 1.71, which is 41% slower than that of the FSIW of the same size, meaning the longitudinal dimension can be reduced by 41%, and the total area is reduced by 60%.

[0054] Figure 5 Figures (a) and (b) show the simulation results of the S-parameters and the attenuation constant of this invention. As can be seen from the figures, in the 3–11 GHz frequency band, when the signal is input from the first port, its return loss (|S...)... 11 The relative bandwidth of -20dB is 68%, and the in-band (4-8GHz) attenuation constant is less than 0.0075dB / mm. It can be seen that the invented transmission line has good broadband characteristics and extremely low loss.

[0055] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A FSIW transmission line with periodic loading ring-mushroom structures, characterized in that The application relates to a FSIW (Finline Substrate Integrated Waveguide) transmission line, which comprises a medium layer, a top metal layer on the upper surface of the medium layer, a bottom metal layer on the lower surface of the medium layer, and an intermediate metal layer in the medium layer. Two rows of first metalized via arrays are arranged in parallel and penetrate the medium layer, and the two ends of each metalized via are connected with the top metal layer and the bottom metal layer respectively. The intermediate metal layer comprises a plurality of periodically arranged ring-mushroom structures, trapezoidal transition strips and strip lines. One side of the periodically arranged ring-mushroom structures is connected with one row of the first metalized via arrays, and the other side is not in contact with the other row of the first metalized via arrays. Each ring-mushroom structure comprises a square metal patch, a square metal ring and a central metalized via. The square metal patch is embedded in the square metal ring and is connected to the top metal layer and the bottom metal layer through the central metalized via. The square metal ring of the ring-mushroom structure near the FSIW crease is extended in the crease direction by a certain width. The geometric centers of the square metal ring, the square metal patch and the central metalized via coincide. The trapezoidal transition strips are a certain distance away from the crease. The distance between the intermediate metal layer and the top metal layer and the bottom metal layer is equal.

2. The FSIW transmission line of periodic loaded ring-mushroom structure according to claim 1, characterized in that By regulating the pass width of the two rows of first metallized via hole array W s , the width of the square metal ring in the ring-mushroom structure W g , the gap distance between the square metal ring and the square metal patch in the ring-mushroom structure s , thereby changing the cutoff frequency of the FSIW.

3. The FSIW transmission line of periodic loaded ring-mushroom structure according to claim 1, characterized in that The medium layer is formed by stacking two medium substrates, and the intermediate metal layer is located between the two medium substrates.

4. The FSIW transmission line of periodic loaded ring-mushroom structure according to claim 1, characterized in that The passband of the periodically loaded ring-mushroom FSIW is set to 6.5 GHz.

5. The FSIW transmission line of periodic loaded ring-mushroom structure according to claim 1, characterized in that The center lines of the two trapezoidal transition strips and the two strip lines are located on the same straight line.

6. The FSIW transmission line of periodic loaded ring-mushroom structure according to claim 1, characterized in that When the signal is conducted in the ring-mushroom structure, the top metal layer and the bottom metal layer are equivalent to the ground.

7. The FSIW transmission line of periodically loaded ring-mushroom structure according to claim 6, characterized in that The square metal patch in the ring-mushroom structure is higher in potential than the top metal layer and the bottom metal layer because the square metal patch is connected to the top metal layer and the bottom metal layer through the central metalized via.

8. The FSIW transmission line of periodic loaded ring-mushroom structure according to claim 1, characterized in that Therefore, the square metal patch in the ring-mushroom structure, the top metal layer, the bottom metal layer and the medium layer are equivalent to a capacitor, which increases the capacitive effect of the FSIW transmission line.

9. The FSIW transmission line of periodic loaded ring-mushroom structure according to claim 1, characterized in that Meanwhile, the square metal ring in the ring-mushroom structure is connected to the upper and lower metal layers through one side of the first metalized via array.

10. The FSIW transmission line of periodically loaded ring-mushroom structure according to any one of claims 1-9, characterized in that When the signal is input from the stripline port, the TE 0.5,0 mode is transmitted in the FSIW, and the electric field direction is along the length direction of the dielectric layer; the length and width of the dielectric layer respectively extend along the y-axis and the x-axis, and the upper and lower thicknesses extend along the z-axis, and the x, y and z axes form an orthogonal coordinate system, and for the TE 0.5,0 mode, any xoz plane inside the FSIW can be equivalent to an ideal electric wall, so the middle metal layer of the FSIW does not affect the TE 0.5,0 mode electric field distribution; the first array of metallized vias is equivalent to an ideal electric wall, and one side of the middle metal layer is connected to the first array of metallized vias and the other side is not connected to the first array of metallized vias, resulting in that the upper and lower layers of the dielectric of the FSIW are connected, and energy can be simultaneously propagated in the upper and lower layers; since the upper and lower layers of the FSIW are completely the same, the electric field distributions of the upper and lower layers are also the same; Because the square metal patch in the ring-mushroom structure and the square metal ring have different grounding paths, their potentials are different. Therefore, the square metal patch in the ring-mushroom structure, the medium layer and the square metal ring in the ring-mushroom structure are equivalent to a capacitor, which increases the capacitive effect of the FSIW transmission line. When multiple ring-mushroom structures are connected, they are equivalent to multiple capacitors in parallel. By increasing the capacitive effect of the FSIW transmission line, the equivalent dielectric constant of the medium is increased. Because the lateral size of the transmission line is inversely proportional to the equivalent dielectric constant of the medium, the lateral size of the FSIW transmission line is reduced. Because the propagation speed of electromagnetic waves in different media is inversely proportional to the equivalent dielectric constant of the medium, the transmission speed of electromagnetic waves is reduced, and the longitudinal size of the FSIW transmission line is reduced.

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