Broadband waveguide-ground coplanar waveguide transition structure based on double dipole antenna

Abstract

The application discloses a broadband waveguide-ground coplanar waveguide transition structure based on a double-dipole antenna, and belongs to the technical field of terahertz waves, which comprises an input end waveguide, a rectangular metal cavity, a terahertz integrated chip and an output end waveguide; the terahertz integrated chip comprises a substrate, an integrated structure, a back gold layer and two first dipole antenna transition sections; the integrated structure comprises two coplanar waveguide center conductive strips, a first coplanar waveguide ground layer, two second coplanar waveguide ground layers, a plurality of air bridges and four antenna structures; the antenna structure and the first dipole antenna transition section in the corresponding same end region form a pair of dipole antennas, and there are totally four pairs of dipole antennas. In the application, the transition section for connecting the coplanar waveguide ground layer in the traditional on-chip dipole antenna is placed in the back gold layer, so that the area occupied by the dipole antenna is greatly reduced, the electromagnetic energy coupling efficiency is improved, the bandwidth of the transition structure is expanded, the structure is simple, easy to process, and has a good application prospect.

Description

Technical Field

[0001] This invention belongs to the field of terahertz technology, specifically relating to a broadband waveguide-ground coplanar waveguide transition structure based on a dual dipole antenna. Background Technology

[0002] Terahertz frequencies typically range from 0.1 THz to 10 THz, falling between the microwave and infrared bands and representing a transitional region from electronics to photonics. Due to its unique location, terahertz waves possess transient, broadband, and low-energy characteristics, leading to wide applications in security inspection, imaging, radar, communications, and astronomy. Terahertz monolithic integrated circuits are a crucial cornerstone of the future electronics and information industry.

[0003] Grounded coplanar waveguides are often used as transmission lines in terahertz monolithic integrated circuits due to their robust grounding structure and lower loss at high frequencies. However, because terahertz waves have high frequencies and small dimensions, traditional gold wire bonding introduces significant losses when designing waveguide-to-grounded coplanar waveguide transition structures. Therefore, on-chip antenna coupling can be used to achieve the transition. In 2011, V. Radisic et al. designed a waveguide-to-coplanar waveguide transition structure with integrated dual-dipole antennas based on 50nm InP HEMT (High Electron Mobility Transistor) technology in their paper "220-GHz solid-state power amplifier modules". However, their designed dual-dipole antenna transition structure places all the dipole antennas on the front side of the chip, occupying a large area and resulting in poor performance, with a relative bandwidth of only 19.5% at a return loss of 8dB.

[0004] To address the aforementioned issues, designing a small-area, wide-bandwidth on-chip integrated dual-dipole antenna waveguide transition structure to a grounded coplanar waveguide, based on the traditional dual-dipole antenna, has become an urgent problem to be solved. Summary of the Invention

[0005] To address the problems in the prior art, this invention provides a broadband waveguide-ground coplanar waveguide transition structure based on a dual dipole antenna. This structure reduces the antenna footprint while further improving electromagnetic energy coupling efficiency, achieving a wideband, high-performance terahertz waveguide-planar transmission line transition.

[0006] The technical solution adopted in this invention is as follows:

[0007] A broadband waveguide-ground coplanar waveguide transition structure based on a dual dipole antenna includes an input waveguide, a rectangular metal cavity, and an output waveguide in sequence, as well as a terahertz integrated chip disposed inside the rectangular metal cavity; the terahertz integrated chip is perpendicular to the H-plane of the input waveguide and the output waveguide.

[0008] The terahertz integrated chip includes a substrate, an integrated structure fabricated on the front side of the substrate, and a back gold layer and two first dipole antenna transition sections fabricated on the back side of the substrate; wherein, the integrated structure includes two coplanar waveguide center guide strips arranged along the signal transmission direction, a first coplanar waveguide ground layer located between the two coplanar waveguide center guide strips, two second coplanar waveguide ground layers located outside the two coplanar waveguide center guide strips respectively, multiple air bridges for connecting the first coplanar waveguide ground layers and the second coplanar waveguide ground layers, and four antenna structures;

[0009] The first coplanar waveguide grounding layer has a row of metal vias connected to the back metal along the signal transmission direction, and the second coplanar waveguide grounding layer has multiple metal vias connected to the back metal around its perimeter.

[0010] The two ends of the center guide strips of the two coplanar waveguides are respectively connected to the corresponding antenna structures, and the two transition sections of the first dipole antennas are respectively connected to the two ends of the back gold region corresponding to the ground layer of the first coplanar waveguide; the antenna structure and the transition section of the first dipole antenna in the corresponding same end region constitute a pair of dipole antennas, for a total of four pairs of dipole antennas.

[0011] Furthermore, the four antenna structures are of different sizes.

[0012] Furthermore, the antenna structure includes a second dipole antenna transition section and a coupling stub in sequence.

[0013] Furthermore, the coupling stub includes a series of short stubs and a polygonal coupling disk; wherein the short stubs are perpendicular to the transition section of the second dipole antenna; the maximum size of the polygonal coupling disk is greater than the width of the short stubs to increase the electromagnetic coupling area.

[0014] Furthermore, by adjusting the length and width of the transition section of the first dipole antenna, the length and width of the transition section of the second dipole antenna, the length and width of the short stub, and the maximum size of the polygonal coupling disk, the energy input from the input waveguide is coupled to the dipole antenna with the highest efficiency.

[0015] Furthermore, the width of the first coplanar waveguide grounding layer is slightly larger than the diameter of the internal metal via.

[0016] Furthermore, the input waveguide includes a standard rectangular input waveguide and a height-reduced input waveguide in sequence, and the output waveguide includes a height-reduced output waveguide and a standard rectangular output waveguide in sequence.

[0017] Furthermore, the end of the reduced-height input waveguide and the beginning of the reduced-height output waveguide extend into the rectangular metal cavity, respectively, and the dipole antennas at both ends are located inside the end of the reduced-height input waveguide and the beginning of the reduced-height output waveguide, respectively.

[0018] Furthermore, the substrate is made of InP.

[0019] Furthermore, the thickness of the substrate is 15–60 μm.

[0020] The beneficial effects of this invention are as follows:

[0021] The broadband waveguide-to-ground coplanar waveguide transition structure proposed in this invention, by placing the transition section connecting the coplanar waveguide ground layer in the traditional on-chip dipole antenna on the back gold layer, greatly reduces the area occupied by the dipole antenna, improves the electromagnetic energy coupling efficiency, and expands the bandwidth of the transition structure. This invention is applied to the transition from waveguide to on-chip transmission line in terahertz monolithic integrated circuits. It has a simple structure, is easy to process, and has good application prospects. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a broadband waveguide-ground coplanar waveguide transition structure based on a dual dipole antenna provided in Embodiment 1 of the present invention.

[0023] Figure 2 for Figure 1 AA cross-section view;

[0024] Figure 3 This is a detailed front view of the terahertz integrated chip in Embodiment 1 of the present invention.

[0025] Figure 4 This is a detailed view of the back structure of the terahertz integrated chip in Embodiment 1 of the present invention;

[0026] Figure 5 The simulation results of S11 and S21 of the broadband waveguide-ground coplanar waveguide transition structure based on a dual dipole antenna provided in Embodiment 1 of the present invention applied to the 110-170GHz frequency band are shown in the figure.

[0027] The explanations of the markings in the attached diagram are as follows:

[0028] 101: Antenna structure; 102: InP substrate; 103: Coplanar waveguide center guide strip; 104: First coplanar waveguide ground layer; 105: Second coplanar waveguide ground layer; 106: Air bridge; 107: Back gold; 108: Metal via; 201: Rectangular metal cavity; 202: Standard rectangular input waveguide; 203: Height-reduced input waveguide; 204: Height-reduced output waveguide; 205: Standard rectangular output waveguide; 1011: First dipole antenna transition section; 1012: Second dipole antenna transition section; 1013: Short stub; 1014: Octagonal coupling disk. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0030] Example 1

[0031] This embodiment provides a broadband waveguide-ground coplanar waveguide transition structure based on a dual-dipole antenna, as shown in the following figure. Figure 1 As shown, the device includes, in sequence, a standard rectangular input waveguide 202, a height-reducing input waveguide 203, a rectangular metal cavity 201, a height-reducing output waveguide 204, and a standard rectangular output waveguide 205, as well as a terahertz integrated chip disposed inside the rectangular metal cavity 201; wherein, the terahertz integrated chip is perpendicular to the H-plane of the height-reducing input waveguide 203 and the height-reducing output waveguide 204; the terahertz on-chip integrated dipole antenna has a symmetrical structure about the signal transmission direction.

[0032] like Figure 2 As shown, the terahertz integrated chip includes a 50μm thick InP substrate 102, an integrated structure fabricated on the front side of the InP substrate 102, and a 6μm thick back gold layer 107 and two first dipole antenna transition sections 1011 fabricated on the back side of the InP substrate 102; wherein, the integrated structure is as follows Figure 3As shown, the device includes two coplanar waveguide center guide strips 103 arranged along the signal transmission direction, a first coplanar waveguide ground layer 104 located between the two coplanar waveguide center guide strips 103, two second coplanar waveguide ground layers 105 located outside the two coplanar waveguide center guide strips 103 respectively, multiple air bridges 106 for connecting the first coplanar waveguide ground layer 104 and the second coplanar waveguide ground layer 105, and four antenna structures 101; the two second coplanar waveguide ground layers 105 are symmetrically arranged about the first coplanar waveguide ground layer 104; the two ends of the two coplanar waveguide center guide strips 103 are respectively connected to the corresponding antenna structures 101, that is, the two ends of the first coplanar waveguide center guide strip 103 are respectively connected to two antenna structures 101, and the two ends of the second coplanar waveguide center guide strip 103 are respectively connected to the remaining two antenna structures 101.

[0033] In this embodiment, the four antenna structures have the same structure and size, each including a second dipole antenna transition section 1012, a short stub 1013, and an octagonal coupling disk 1014 in sequence; wherein, the second dipole antenna transition section 1012 is connected to one end of the corresponding coplanar waveguide center guide strip 103; the short stub 1013 is perpendicular to the second dipole antenna transition section 1012; the maximum size of the octagonal coupling disk 1014 is larger than the width of the short stub 1013, so as to increase the electromagnetic coupling area and reduce the processing difficulty.

[0034] The first coplanar waveguide grounding layer 104 has a row of metal vias 108 connected to the back metal 107 along the signal transmission direction. The second coplanar waveguide grounding layer 105 has a plurality of metal vias 108 connected to the back metal 107 around its perimeter. The diameter of each metal via 108 is 30 μm and the spacing between adjacent metal vias 108 is 69 μm.

[0035] like Figure 4 As shown, the two first dipole antenna transition sections 1011 are respectively connected to the two ends of the back gold 107 region corresponding to the first coplanar waveguide grounding layer 104; the antenna structure 101 and the first dipole antenna transition section 1011 in the corresponding same end region constitute a pair of dipole antennas, and the two antenna structures 101 in the same end region share a first dipole antenna transition section 1011, thereby forming four pairs of dipole antennas.

[0036] The end of the reduced height input waveguide 203 and the beginning of the reduced height output waveguide 204 extend into the rectangular metal cavity 201, respectively. Two pairs of dipole antennas at one end are located inside the end of the reduced height input waveguide 203, and two pairs of dipole antennas at the other end are located inside the beginning of the reduced height output waveguide 204.

[0037] By adjusting the length and width of the first dipole antenna transition section 1011, the length and width of the second dipole antenna transition section 1012, the length and width of the short stub 1012, and the maximum size of the octagonal coupling disk 1014, the energy input from the standard rectangular input waveguide 202 and the reduced-height input waveguide 203 is coupled to the dipole antenna with the highest efficiency.

[0038] In this embodiment, the InP substrate 102 has a width of 1200 μm; the width and thickness of the two coplanar waveguide center guide strips 103 are 26 μm and 3.2 μm, respectively; the width and thickness of the first coplanar waveguide ground layer 104 are 60 μm and 3.2 μm, respectively; the width and thickness of the two second coplanar waveguide ground layers 105 are 440 μm and 3.2 μm, respectively; and the gap width between the coplanar waveguide center guide strips 103 and the first coplanar waveguide ground layer 104 (second coplanar waveguide ground layer 105) is 20 μm.

[0039] In this embodiment, the four pairs of dipole antennas are all the same size, specifically: the two coplanar waveguide center guide strips 103 extend beyond the first coplanar waveguide ground layer 104 (second coplanar waveguide ground layer 105) by a length of 260μm; the length and width of the first dipole antenna transition section 1011 are 248μm and 35μm, respectively; the length and width of the second dipole antenna transition section 1012 are 260μm and 24μm, respectively; the length and width of the short stub 1013 are 60μm and 40μm, respectively; and the diameter of the octagonal coupling disk 1014 is 35μm.

[0040] The broadband waveguide-to-ground coplanar waveguide transition structure based on a dual dipole antenna proposed in this embodiment can be applied to terahertz monolithic-to-waveguide transition in the 110-170 GHz frequency band. The specific working principle is as follows: the signal energy input sequentially from the standard rectangular input waveguide 202 and the reduced height input waveguide 203 is coupled by the antenna structure 101, converting the TE10 mode transmitted in the rectangular waveguide into the TEM mode transmitted in the ground coplanar waveguide. Then the signal is transmitted to the terahertz integrated chip, completing the terahertz monolithic-to-waveguide transition.

[0041] Figure 5 The figures for S11 and S21 show the simulation results of the terahertz monolithic waveguide transition applied to the 110–170 GHz frequency band in this embodiment. It can be seen that in the 117–171 GHz frequency band, the back-to-back simulation insertion loss is better than 1 dB, the single-sided transition loss is better than 0.4 dB, the return loss is better than 15 dB, and the relative bandwidth is 37.5%. The performance is excellent and significantly better than the performance of the waveguide-to-coplanar waveguide transition structure of the traditional integrated dual dipole antenna.

[0042] In summary, Embodiment 1 of the present invention employs a dual dipole antenna transition structure and cleverly places the transition section connecting the front of the dipole antenna to the ground coplanar waveguide on the back metal ground layer. This not only reduces the area occupied by the antenna but also greatly increases the coupling efficiency, ultimately achieving a wide-bandwidth, high-performance terahertz monolithic waveguide transition.

[0043] The above embodiments are only for illustrating the principles and advantages of the present invention, and are not intended to limit the present invention. They are only for helping to understand the principles of the present invention. The scope of protection of the present invention is not limited to the above configurations and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the disclosed technology without departing from the essence of the present invention, but they are still within the scope of protection of the present invention.

Claims

1. A broadband waveguide-ground coplanar waveguide transition structure based on a dual-dipole antenna, characterized in that, It includes an input waveguide, a rectangular metal cavity, and an output waveguide, arranged sequentially, as well as a terahertz integrated chip disposed inside the rectangular metal cavity; the terahertz integrated chip is perpendicular to the H-plane of the input waveguide and the output waveguide; The terahertz integrated chip includes a substrate, an integrated structure fabricated on the front side of the substrate, and a back gold layer and two first dipole antenna transition sections fabricated on the back side of the substrate; wherein, the integrated structure includes two coplanar waveguide center guide strips arranged along the signal transmission direction, a first coplanar waveguide ground layer located between the two coplanar waveguide center guide strips, two second coplanar waveguide ground layers located outside the two coplanar waveguide center guide strips respectively, multiple air bridges for connecting the first coplanar waveguide ground layers and the second coplanar waveguide ground layers, and four antenna structures; The first coplanar waveguide grounding layer has a row of metal vias connected to the back metal along the signal transmission direction, and the second coplanar waveguide grounding layer has multiple metal vias connected to the back metal around its perimeter. The two ends of the center guide strips of the two coplanar waveguides are respectively connected to the corresponding antenna structures, and the two transition sections of the first dipole antennas are respectively connected to the two ends of the back gold region corresponding to the ground layer of the first coplanar waveguide; the antenna structure and the transition section of the first dipole antenna in the corresponding same end region constitute a pair of dipole antennas, for a total of four pairs of dipole antennas.

2. The broadband waveguide-ground coplanar waveguide transition structure based on a dual dipole antenna according to claim 1, characterized in that, The four antenna structures are of different sizes.

3. The broadband waveguide-ground coplanar waveguide transition structure based on a dual dipole antenna according to claim 1, characterized in that, The antenna structure includes a second dipole antenna transition section and a coupling stub in sequence.

4. The broadband waveguide-ground coplanar waveguide transition structure based on a dual dipole antenna according to claim 3, characterized in that, The coupling stub includes a series of short stubs and a polygonal coupling disk; wherein the short stubs are perpendicular to the transition section of the second dipole antenna; and the maximum size of the polygonal coupling disk is greater than the width of the short stubs.

5. The broadband waveguide-ground coplanar waveguide transition structure based on a dual dipole antenna according to claim 4, characterized in that, By adjusting the length and width of the transition section of the first dipole antenna, the length and width of the transition section of the second dipole antenna, the length and width of the short stub, and the maximum size of the polygonal coupling disk, the energy input from the input waveguide is coupled to the dipole antenna with the highest efficiency.

6. The broadband waveguide-ground coplanar waveguide transition structure based on a dual dipole antenna according to claim 1, characterized in that, The input waveguide includes a standard rectangular input waveguide and a height-reduced input waveguide in sequence, and the output waveguide includes a height-reduced output waveguide and a standard rectangular output waveguide in sequence.

7. The broadband waveguide-ground coplanar waveguide transition structure based on a dual dipole antenna according to claim 6, characterized in that, The end of the reduced-height input waveguide and the beginning of the reduced-height output waveguide extend into the rectangular metal cavity, respectively, and the dipole antennas at both ends are located inside the end of the reduced-height input waveguide and the beginning of the reduced-height output waveguide, respectively.

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