An ultra-wideband transition structure for substrate integrated coaxial line and microstrip line

Abstract

The application discloses a substrate integrated coaxial line and microstrip line ultra-wideband switching structure, which comprises a metal microstrip line, a V-shaped gradually-changing impedance matching section, a metal inner conductor and a top metal conductor. The microstrip line is extended from the metal inner conductor to form a specific shape, and the top metal conductor is hollowed out to form the V-shaped gradually-changing impedance matching section. The substrate integrated coaxial line and microstrip line ultra-wideband switching structure realizes bidirectional switching from the substrate integrated coaxial line to the microstrip line and from the microstrip line to the substrate integrated coaxial line, and has the characteristics of wide frequency band, miniaturization, low loss, easy integration and reduction of parasitic radiation.

Description

Technical Field

[0001] This invention relates to the field of broadband antenna technology, and more particularly to an ultra-wideband adapter structure. Background Technology

[0002] In the field of communications, switching structures are an indispensable part of communication links. With the rapid increase in information transmission rates between various communication devices, the performance optimization of switching structures has a significant impact on the performance indicators of the entire communication system, and at the same time, it has created a need for broadband and miniaturization.

[0003] Substrate-integrated coaxial transmission lines are formed by laminating coaxial transmission line layers consisting of an inner conductor, an outer conductor, an intermediate dielectric, and metallized vias. Substrate-integrated coaxial line technology inherits the excellent transmission characteristics of substrate-integrated waveguides while also possessing the advantages of small size, wide bandwidth, and non-dispersive transmission lines. It features low electromagnetic radiation, low insertion loss, compact structure, and ease of integration. Microstrip transmission lines consist of a single conductor strip on a dielectric substrate and are a widely used transmission structure in microwave integrated circuits. Compared to metallic waveguides, they offer advantages such as small size, light weight, wide operating bandwidth, high reliability, and low manufacturing cost.

[0004] Therefore, the transition structure between substrate-integrated coaxial lines and microstrip lines has always been a research hotspot. Currently, the commonly used transition structure between substrate-integrated coaxial lines and microstrip lines is a grounded coplanar waveguide structure. This structure consists of a dielectric substrate, a metal ground plane, and three conductor strips. A central conductor strip is fabricated on one surface of the dielectric substrate, and conductor planes are fabricated on both sides adjacent to the central conductor strip, forming a grounded coplanar waveguide with the metal ground plane. However, the bandwidth of the grounded coplanar waveguide in the transition application with substrate-integrated coaxial lines is relatively narrow, and the parasitic radiation generated by the three conductor strips cannot be ignored. Therefore, how to expand the bandwidth and reduce parasitic radiation has become a pressing technical challenge.

[0005] Currently, GCPW is also used as a transitional structure to achieve the switching between substrate integrated coaxial line and microstrip line: the substrate integrated coaxial line is converted to GCPW, and then the GCPW is converted to microstrip. However, the bandwidth achieved by this technology is relatively small and cannot meet the needs of modern communication switching.

[0006] Therefore, a new technical solution is needed to solve the above problems. Summary of the Invention

[0007] To address the problems arising from existing technologies, this invention provides a wideband, miniaturized, low-loss, and easily integrated ultrawideband adapter structure for substrate-integrated coaxial lines and microstrip lines.

[0008] To achieve the above objectives, the ultra-wideband transition structure of substrate-integrated coaxial line and microstrip line of the present invention can adopt the following technical solution:

[0009] An ultrawideband switching structure for substrate-integrated coaxial line and microstrip line includes an inner metal conductor, a top metal conductor, a bottom metal conductor, a dielectric layer between the top metal conductor and the bottom metal conductor, the inner metal conductor being located between the top metal conductor and the bottom metal conductor, and a metal microstrip line extending from one end of the inner metal conductor.

[0010] The metal microstrip line extends from one end of the metal inner conductor along the length extension direction. The width of the metal microstrip line gradually increases at the end connected to the metal inner conductor, forming a trapezoidal shape, while the width of the other end of the metal microstrip line remains unchanged, forming a rectangle.

[0011] The V-shaped gradient impedance matching section is located at the end of the top metal conductor that is close to the metal microstrip line. The V-shaped gradient impedance matching section is formed by hollowing out the top metal conductor along its length to create a symmetrical V-shaped recess.

[0012] Furthermore, the V-shaped gradient impedance matching section has a length of 5mm to extend the impedance bandwidth.

[0013] Furthermore, the dielectric layer includes an upper dielectric layer, an intermediate adhesive layer, and a lower dielectric layer; a bottom metal conductor covers the lower surface of the lower dielectric layer; and a top metal conductor covers the upper surface of the upper dielectric layer.

[0014] Furthermore, the intermediate adhesive layer tightly connects the upper dielectric layer and the lower dielectric layer, with the upper dielectric layer completely overlapping the intermediate adhesive layer, and a portion of the lower dielectric layer extending out of the intermediate adhesive layer along its length.

[0015] Furthermore, a metal inner conductor is provided at the center of the portion of the upper surface of the lower dielectric layer that overlaps with the intermediate adhesive layer along the length extension direction; a metal microstrip line is provided at the center of the portion of the upper surface of the lower dielectric layer that extends beyond the intermediate adhesive layer along the length extension direction.

[0016] Furthermore, the ultra-wideband transition structure for substrate-integrated coaxial lines and microstrip lines also includes two rows of metallized vias parallel to the length extension direction. The vias are symmetrically arranged on both sides of the inner metal conductor and run through the entire ultra-wideband transition structure from top to bottom.

[0017] Furthermore, the intermediate adhesive layer is a Taconic TLC-27 substrate; the upper dielectric layer and the lower dielectric layer are both Taconic TLY-5 printed circuit boards.

[0018] Furthermore, the top metal conductor, upper dielectric layer, middle adhesive layer, lower dielectric layer, bottom metal conductor, inner metal conductor, and metallized via are sequentially arranged to form a substrate integrated coaxial line.

[0019] Furthermore, the metal microstrip line, top metal conductor, bottom metal conductor, inner metal conductor, and metallized via are made of copper.

[0020] Furthermore, the entire ultra-wideband transition structure is fabricated using a multilayer printed circuit board (PCB). A metal conductor with a V-shaped gradient impedance matching section is formed by metal plating on the upper dielectric layer's surface. A bottom metal conductor is formed by metal plating on the lower dielectric layer's lower surface, and an inner metal conductor is formed by metal plating at the center of the first half of the upper surface's length extension. A metal microstrip line is etched at the center of the second half of the upper surface's length extension. The upper and lower dielectric layers, along with the intermediate adhesive layer, are laminated together. Finally, two rows of through-holes are drilled at corresponding locations, and electrical connections are achieved through metal plating between the holes. The overall structure measures 15mm * 5mm * 0.678mm.

[0021] The present invention has the following beneficial effects:

[0022] 1. This invention cleverly combines substrate-integrated coaxial line and microstrip line, and adds a V-shaped gradual impedance matching section to ensure good impedance matching and good transmission characteristics in a wide frequency band.

[0023] 2. This invention uses a single conductor strip, which reduces parasitic radiation compared to the three conductor strips in the prior art, thereby improving the efficiency and quality of energy transmission.

[0024] 3. The substrate-integrated coaxial cable has low loss characteristics, and the semi-open structure formed by hollowing out the upper metal conductor and setting a V-shaped gradual impedance matching section in this invention will reduce the loss.

[0025] 4. Due to its simple structure, the structure of this invention can be directly applied in the design of antennas or radio frequency circuits without modification, with few restrictions on its use and easy integration.

[0026] 5. The present invention is 15mm long, 5mm wide, and 0.678mm high, achieving miniaturization. Attached Figure Description

[0027] Figure 1 This is an exploded perspective view of the ultra-wideband switching structure of the present invention;

[0028] Figure 2 This is a top view of the ultra-wideband switching structure of the present invention;

[0029] Figure 3 This is a side view of the ultra-wideband switching structure of the present invention;

[0030] Figure 4 This is a bottom view of the ultra-wideband switching structure of the present invention;

[0031] Figure 5 This is a comparison diagram of S-parameters under different V-shaped gradual impedance matching section lengths in the ultra-wideband transition structure of the present invention.

[0032] In the figure, 1 is a metal microstrip line, 2 is a metallized via on the left, 3 is a metal inner conductor, 4 is a V-shaped tapered impedance matching section, 5 is a metallized via on the right, 6 is a top metal conductor, 7 is an upper dielectric layer, 8 is an intermediate bonding layer, 9 is a lower dielectric layer, and 10 is a bottom metal conductor. Detailed Implementation

[0033] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. After reading the present invention, any modifications of the present invention in various equivalent forms by those skilled in the art will fall within the scope defined by the appended claims.

[0034] Please see Figures 1 to 4 The present invention discloses an ultra-wideband transition structure 100 for substrate-integrated coaxial line and microstrip line, including a metal microstrip line 1, a left metallized via 2, a metal inner conductor 3, a V-shaped tapered impedance matching section 4, a right metallized via 5, a top metal conductor 6, an upper dielectric layer 7, an intermediate adhesive layer 8, a lower dielectric layer 9, and a bottom metal conductor 10.

[0035] In this invention, the metal microstrip line 1 extends from one end of the metal inner conductor 3 along the length extension direction. The width of the metal microstrip line 1 at the end connected to the metal inner conductor 3 gradually increases to form a trapezoid, while the width of the other end of the metal microstrip line 1 remains unchanged to form a rectangle. The metal microstrip line 1 and the metal inner conductor 3 are located at the center of the upper surface of the lower dielectric layer 9 along the length extension direction. The top metal conductor 6 is hollowed out along the length extension direction to form a symmetrical V-shaped recess, which is the V-shaped gradual impedance matching section 4. The invention is simulated using simulation software, and the length of the V-shaped gradual impedance matching section 4 is set to 5mm based on the simulation results.

[0036] The intermediate adhesive layer 8 tightly connects the upper dielectric layer 7 and the lower dielectric layer 9, with the upper dielectric layer 7 completely overlapping the intermediate adhesive layer 8. A portion of the lower dielectric layer 9 extends beyond the intermediate adhesive layer 8 along its length. The bottom metal conductor 10 covers the lower surface of the lower dielectric layer 9, and the top metal conductor 6 covers the upper surface of the upper dielectric layer 7. A metal inner conductor 3 is located at the center of the portion of the upper surface of the lower dielectric layer 9 that overlaps with the intermediate adhesive layer 8 along its length. A metal microstrip line 1 is located at the center of the portion of the upper surface of the lower dielectric layer 9 that extends beyond the intermediate adhesive layer 8 along its length. Metallized vias are symmetrically arranged on both sides of the metal inner conductor 3, penetrating the entire ultra-wideband transition structure 100 from top to bottom. The left metallized via 2 and the right metallized via 3 form a closed structure with good shielding. The top metal conductor 6, upper dielectric layer 7, intermediate adhesive layer 8, lower dielectric layer 9, bottom metal conductor 10, metal inner conductor 3, and metallized vias are arranged sequentially to form a substrate integration coaxial line.

[0037] The ultra-wideband transition structure 100 integrating coaxial cable and microstrip line on the substrate is processed using a multilayer printed circuit board (PCB). A top metal conductor 6 with a V-shaped gradient impedance matching section 4 is formed by metal plating on the upper dielectric layer 7. A bottom metal conductor 10 is formed by metal plating on the lower dielectric layer 9. An inner metal conductor 3 is formed by metal plating at the center of the first half of the upper surface of the lower dielectric layer 9 along its length extension direction. A metal microstrip line 1 is etched at the center of the second half of the upper surface of the lower dielectric layer 9 along its length extension direction. The upper layer 7, the lower dielectric layer 9, and the intermediate adhesive layer 8 are laminated together. Finally, two rows of through holes are drilled at corresponding positions, and electrical connection is achieved through metal plating between the holes.

[0038] This invention utilizes a substrate-integrated coaxial cable with good sealing properties as one end of the adapter structure 100, which is easy to integrate with other circuits and reduces energy loss during propagation. On the other hand, the other end of the adapter uses a microstrip line structure, which is widely used in circuit design. Microstrip lines can be used in the design of numerous empirical circuits and are applicable to a frequency range of 3-40 GHz. They are also small in size, lightweight, have a low profile, are low in cost, and are easy to manufacture and apply. This invention 100 cleverly combines a substrate-integrated coaxial cable and a microstrip line, resulting in high energy transfer efficiency and good impedance matching, thus providing excellent transmission characteristics over a wide frequency range.

[0039] In this embodiment, the diameter of the left metallized through hole 2 and the right metallized through hole 3 is 0.4 mm, the hole spacing between adjacent metallized through holes in each row is 0.6 mm, and the distance between the left metallized through hole 2 and the right metallized through hole 3 is 2 mm. Appropriate through hole size and hole spacing can reduce the processing difficulty and achieve the purpose of preventing electromagnetic wave leakage.

[0040] Both the upper dielectric layer 7 and the lower dielectric layer 9 are Taconic TLY-5 printed circuit boards with a thickness of 0.254 mm, and the intermediate adhesive layer 8 is a Taconic TLC-27 adhesive layer with a thickness of 0.1 mm. The metal microstrip line 1, the metal inner conductor 3, the upper metal conductor 6, the lower metal conductor 10, and the metallized via 2 are all made of copper.

[0041] The width of the metal microstrip line 1 gradually increases from 0.4 mm (the width of the inner metal conductor 3) to 0.7 mm, then remains constant at 0.7 mm. This gradually increasing width is a transition section, and a suitable transition method is used to effectively improve impedance matching and extend the impedance bandwidth. This invention 100 uses a single conductor strip, which reduces parasitic radiation compared to the three conductor strips used in existing technologies, improving energy transmission efficiency and quality. A V-shaped tapered impedance matching segment 4 is formed along the length extension direction of the top metal conductor 6. This segment is symmetrical about its central axis and has a length of 5 mm. A suitable length for this segment extends the impedance bandwidth, and the semi-open structure also reduces losses. The overall structure 100 measures 15 mm * 5 mm * 0.678 mm.

[0042] like Figure 5 As shown, in this embodiment, simulation software is used to perform parameter simulation of the invention. Since the invention operates in free space, after the model of the transition structure 100 is created, the boundary of the structure 100 is set as an ideal boundary condition, and the input port of the transition structure 100 is set as a waveguide port. The performance of the 3-40GHz frequency band is then analyzed and calculated.

[0043] By varying the length of the V-shaped tapered impedance matching section 4, the corresponding scattering parameters, i.e., S-parameters, were statistically analyzed and compared. S-parameters are crucial parameters in microwave transmission; S21 is the forward transmission coefficient, i.e., gain, and S11 is the input reflection coefficient, i.e., input return loss. When the length of the V-shaped tapered impedance matching section 4 is 2.5mm and 4.1mm, the standing wave characteristics of this adapter structure 100 are not ideal. S11 is greater than -15dB between 15-20GHz, and the transmission characteristics are not stable enough. Simultaneously, the amplitude of S21 vibration is large. When the length of the V-shaped tapered impedance matching section 4 is 5mm, S11 is less than -15dB in the 3-40GHz range, and S21 tends to stabilize. Therefore, 5mm was chosen as the length of the V-shaped tapered impedance matching section 4.

[0044] In summary, the ultra-wideband transition structure of substrate-integrated coaxial line and microstrip line of the present invention has the characteristics of wide bandwidth, miniaturization, low loss, easy integration, and reduced parasitic radiation.

Claims

1. A substrate integrated coaxial line and microstrip line transition structure, comprising a metal inner conductor, a top layer metal conductor, a bottom layer metal conductor, a dielectric layer between the top layer metal conductor and the bottom layer metal conductor, characterized in that, The medium layer comprises an upper medium layer, an intermediate adhesive layer, and a lower medium layer. The bottom metal conductor covers the lower surface of the lower medium layer, and the top metal conductor covers the upper surface of the upper medium layer; the upper surface of the lower medium layer has only one metal structure, which is a metal inner conductor and a metal microstrip line; the upper medium layer completely overlaps the intermediate adhesive layer, and a part of the lower medium layer extends out of the intermediate adhesive layer along the length extension direction; the center of the part of the upper surface of the lower medium layer overlapping the intermediate adhesive layer is provided with the metal inner conductor along the length extension direction; the center of the part of the upper surface of the lower medium layer beyond the intermediate adhesive layer is provided with the metal microstrip line along the length extension direction. The metal microstrip line extends from one end of the metal inner conductor along the length extension direction, and the width of the connecting end of the metal microstrip line and the metal inner conductor gradually increases in a trapezoidal shape, and the width of the other end of the metal microstrip line remains unchanged in a rectangular shape. A V-shaped gradually changing impedance matching section is arranged at the end close to the metal microstrip line of the top metal conductor, and the V-shaped gradually changing impedance matching section is a symmetric V-shaped recess formed by hollowing out the top metal conductor along the length extension direction; the length of the V-shaped gradually changing impedance matching section is 5 mm to expand the impedance bandwidth, and the obtained bandwidth frequency range is 3-40 GHz.

2. The substrate integrated coaxial line and microstrip line transition structure of claim 1, wherein, The intermediate adhesive layer tightly connects the upper medium layer and the lower medium layer.

3. The substrate integrated coaxial line and microstrip line transition structure of claim 1, wherein, The substrate integrated coaxial line and microstrip line ultra-wideband adapter structure further comprises two rows of metalized through holes parallel to the length extension direction, which are symmetrically arranged on both sides of the metal inner conductor and penetrate through the entire ultra-wideband adapter structure from top to bottom.

4. The substrate integrated coaxial line and microstrip line transition structure of claim 2, wherein, The intermediate adhesive layer is a Taconic TLC-27 substrate, and the upper medium layer and the lower medium layer are both Taconic TLY-5 printed circuit substrates.

5. The substrate integrated coaxial line and microstrip line transition structure of claim 1 or 3, wherein, The top metal conductor, the upper medium layer, the intermediate adhesive layer, the lower medium layer, the bottom metal conductor, the metal inner conductor, and the metalized through hole are sequentially arranged to form a substrate integrated coaxial line.

6. The substrate integrated coaxial line and microstrip line transition structure according to claim 1 or 3, wherein, The metal microstrip line, the top metal conductor, the bottom metal conductor, the metal inner conductor, and the metalized through hole are made of copper.

7. The substrate integrated coaxial line and microstrip line transition structure according to claim 1 or 3, characterized in that, The entire ultra-wideband adapter structure is processed by using a PCB multi-layer printed circuit board, the top metal conductor provided with the V-shaped gradually changing impedance matching section is formed by plating metal on the upper surface of the upper medium layer, the bottom metal conductor is formed by plating metal on the lower surface of the lower medium layer, and the metal inner conductor is formed by plating metal at the center position of the first half of the length extension direction of the upper surface of the lower medium layer; The metal microstrip line is etched at the center position of the second half of the length extension direction of the upper surface of the lower medium layer, the upper and lower medium layers and the intermediate adhesive layer are laminated and formed, and finally two rows of through holes are drilled at the corresponding positions to realize electrical connection by plating metal between the holes. The metal microstrip line, the top metal conductor, the bottom metal conductor, the metal inner conductor, and the metalized through hole are made of copper.

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