Double-passband filter based on copper-based micromachining technology

Abstract

The invention discloses a double-passband filter based on a copper-based micromachining process, which comprises a coaxial outer conductor and a coaxial inner conductor positioned in the coaxial outer conductor, and is characterized in that the coaxial inner conductor is connected with an input end feeder line and an output end feeder line; the coaxial inner conductor comprises a first quarter-wavelength transmission line, a second quarter-wavelength transmission line, a first half-wavelength transmission line and a second half-wavelength transmission line; the first quarter-wavelength transmission line and the second quarter-wavelength transmission line are simultaneously coupled with the first half-wavelength transmission line and the second half-wavelength transmission line, and the first half-wavelength transmission line and the second half-wavelength transmission line are mutually coupled. The beneficial effects of the invention are that the cable is small in transmission loss and high in signal shielding performance.

Description

Technical Field

[0001] The invention belongs to the field of microwave passive devices, and in particular relates to a dual-passband filter based on a copper-based micromachining process. Background Art

[0002] In order to solve the problem of increasingly tight communication spectrum, filters working in a single frequency band can no longer meet new communication requirements, and filters working in dual-band or even multi-band bands have gradually become a research hotspot. With the rapid and vigorous development of modern microwave and millimeter wave circuits, the performance indicators of the entire circuit system are becoming more stringent, and millimeter wave integrated circuits are developing in the direction of miniaturization, high integration, wide frequency band, low loss and no radiation. Rectangular micro-coaxial line, as an air-filled metal transmission line, is suitable for high operating frequencies and has the advantages of low loss, low line crosstalk and ultra-low dispersion.

[0003] Reference 1 (KSK Yeo and MJ Lancaster, "8 pole high temperature superconductor microstrip dual band bandpass filter design," 2011 IEEE MTT-SInternational Microwave Symposium, Baltimore, MD, USA, 2011, pp. 1-4.) proposes an HTS dual-band bandpass filter that improves isolation by generating a transmission zero between two frequency bands through electromagnetic coupling between two non-adjacent resonators. However, the structure is relatively large in size.

[0004] Reference 2 (F. Zhang, J. Li, P. Zhao, G. Huang and J. Xu, "A Frequency-Tunable High-Selectivity Dual-Band Bandpass Filter With Independently Controllable Passbands," 2018 International Conference on Microwave and Millimeter Wave Technology (ICMMT), Chengdu, China, 2018, pp. 1-3.) proposes a microstrip structure using a half-wavelength dual-mode resonator loaded by a pair of coupled varactor diodes, and independently controlling the center frequencies of the two passbands. This structure has high passband selectivity, but due to the low quality factor of the varactor diode, the insertion loss of this structure is high.

[0005] Reference 3 (D. Li, J. -A. Wang, Y. Liu and Z. Chen, "Miniaturized Dual-Band Bandpass Filter With Sharp Roll-Off Using Ring-Loaded Resonator," inIEEE Access, vol. 8, pp. 25588-25595, 2020.) proposes a dual-bandpass filter based on a ring resonator and a 0° feeding structure. Multiple transmission zeros are introduced by utilizing source-load coupling and 0° feeding. However, the center frequency of this structure is 2.4 GHz and 5.2 GHz, and the operating frequency is relatively low.

[0006] In summary, the problems with the existing technology are: the dual-passband filter has a large structural size, a low operating frequency, and a large loss. In order to solve the problem of the increasingly tight communication spectrum, filters working in a single frequency band can no longer meet the new communication requirements, and filters working in dual or even multi-bands have gradually become a research hotspot. With the rapid and vigorous development of modern microwave and millimeter wave circuits, the performance indicators of the entire circuit system are becoming more and more stringent. Millimeter wave integrated circuits are developing in the direction of miniaturization, high integration, wide frequency band, low loss, and no radiation. As an air-filled metal transmission line, the rectangular micro-coaxial line is suitable for high operating frequencies and has the advantages of low loss, low line crosstalk, and ultra-low dispersion. Summary of the invention

[0007] The object of the present invention is to provide a dual-passband filter based on copper-based micromachining technology.

[0008] To achieve the above object, the present invention provides the following technical solutions: A dual-passband filter based on a copper-based micromachining process comprises a coaxial outer conductor and a coaxial inner conductor located inside the coaxial outer conductor, the coaxial inner conductor is connected to an input end feeder and an output end feeder, the coaxial inner conductor comprises a first quarter wavelength transmission line, a second quarter wavelength transmission line, a first half wavelength transmission line and a second half wavelength transmission line, the first quarter wavelength transmission line and the second quarter wavelength transmission line are coupled to the first half wavelength transmission line and the second half wavelength transmission line at the same time, and the first half wavelength transmission line and the second half wavelength transmission line are coupled to each other.

[0009] Preferably, the coaxial outer conductor adopts a rectangular micro-coaxial five-layer process design in its height direction, each layer has the same height and the coaxial inner conductor is located in the third layer process of the coaxial outer conductor.

[0010] Preferably, the first quarter-wavelength transmission line and the second quarter-wavelength transmission line are connected by a short-circuit grounding wire, the first half-wavelength transmission line and the second half-wavelength transmission line are both bent in a "J" shape, the first half-wavelength transmission line is connected to the input end feeder, and the second half-wavelength transmission line is connected to the output end feeder.

[0011] Preferably, the first half wavelength transmission line and the second half wavelength transmission line are symmetrically arranged with the two X-shaped openings facing each other, and the first quarter wavelength transmission line and the second quarter wavelength transmission line are located inside the two openings.

[0012] Preferably, the impedance of the input feeder and the output feeder are both 50 ohms.

[0013] Preferably, a plurality of rectangular release holes are provided at intervals on the inner wall and the outer wall of the coaxial outer conductor.

[0014] Preferably, the coaxial outer conductor is provided with a plurality of dielectric support strips located below the coaxial inner conductor and used for fixing the coaxial inner conductor.

[0015] The beneficial effects of the present invention are as follows: the present invention adopts a copper-based micromachining process. Compared with the commonly used planar PCB process, the planar transmission line has a higher transmission loss in the high frequency band, while the micro-coaxial line has a small insertion loss, and its advantages are particularly obvious at high frequencies, and the signal shielding is high. Multiple transmission zero points are introduced by using source-load coupling, and the out-of-band suppression capability is strong. The three-dimensional structure is obtained by using the copper-based micromachining process, which is convenient for three-dimensional integrated processing and integration of the device, and has a small size and high precision at the micron level. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural schematic diagram of the present invention.

[0017] Figure 2 It is a side view of the present invention.

[0018] Figure 3 It is a top view of the present invention.

[0019] Figure 4 yes Figure 3 Schematic diagram of the structural dimensions.

[0020] Figure 5 It is the S parameter simulation curve diagram of the present invention.

[0021] Among them: 1. coaxial outer conductor; 2. coaxial inner conductor; 21. first quarter-wavelength transmission line; 22. second quarter-wavelength transmission line; 23. first half-wavelength transmission line; 24. second half-wavelength transmission line; 3. input end feed line; 4. output end feed line; 5. dielectric support bar; 6. ground wire; 7. rectangular release hole. DETAILED DESCRIPTION

[0022] The technical solution of this patent is further described in detail below in conjunction with specific implementation methods.

[0023] like Figures 1 to 4 As shown, a dual-passband filter based on copper-based micromachining technology of the present invention comprises a coaxial outer conductor 1 and a coaxial inner conductor 2 located inside the coaxial outer conductor 1, the coaxial inner conductor 2 is connected with an input end feeder 3 and an output end feeder 4, the coaxial inner conductor 2 comprises a first quarter wavelength transmission line 21, a second quarter wavelength transmission line 22, a first half wavelength transmission line 23 and a second half wavelength transmission line 24, the first quarter wavelength transmission line 21 and the second quarter wavelength transmission line 22 are coupled with the first half wavelength transmission line 23 and the second half wavelength transmission line 24 at the same time, and the first half wavelength transmission line 23 and the second half wavelength transmission line 24 are coupled with each other. The coaxial inner conductor 2 and the coaxial outer conductor 1 are both made of copper, which has good conductivity and low loss during signal transmission. The coaxial outer conductor 1 covers the outside of the coaxial inner conductor 2 to shield electromagnetic interference, and the frequencies outside the specific frequency point are effectively filtered out by coupling the first half wavelength transmission line 23 and the second half wavelength transmission line 24 to each other, and the first quarter wavelength transmission line 21 and the second quarter wavelength transmission line 22 are coupled to the first half wavelength transmission line 23 and the second half wavelength transmission line 24 at the same time.

[0024] The coaxial outer conductor 1 adopts a rectangular micro-coaxial five-layer process design in its height direction, each layer has the same height and the coaxial inner conductor 2 is located in the third layer process of the coaxial outer conductor 1; compared with the traditional planar PCB process, this structure has low transmission loss in the high frequency band.

[0025] The first quarter-wavelength transmission line 21 and the second quarter-wavelength transmission line 22 are connected by a short-circuit grounding line 6, and the first half-wavelength transmission line 23 and the second half-wavelength transmission line 24 are both bent in a "J" shape. The first half-wavelength transmission line 23 is connected to the input end feeder 3, and the second half-wavelength transmission line 24 is connected to the output end feeder 4. Through the "J" shape design, the phase area between the first quarter-wavelength transmission line 21 and the first half-wavelength transmission line 23 and the relative area between the second quarter-wavelength transmission line 22 and the second half-wavelength transmission line 24 are increased.

[0026] The first half-wavelength transmission line 23 and the second half-wavelength transmission line 24 are symmetrically arranged, and the two X-shaped openings face each other. The first quarter-wavelength transmission line 21 and the second quarter-wavelength transmission line 22 are located inside the two openings.

[0027] The impedance of the input feeder 3 and the output feeder 4 is 50 ohms, which can simultaneously meet the maximum power transmission and the minimum loss. At the same time, the 50 ohm system impedance is also matched to the impedance of the quarter wavelength and the port of the transmission line, resulting in small reflection loss.

[0028] A plurality of rectangular release holes 7 are provided at intervals on the inner wall and the outer wall of the coaxial outer conductor 1 , and the air pressure inside and outside the coaxial outer conductor 1 can be balanced through the rectangular release holes 7 .

[0029] The coaxial outer conductor 1 is provided with a plurality of dielectric support bars 5 located below the coaxial inner conductor 2 and used for fixing the coaxial inner conductor 2 . The dielectric support bars 5 are made of insulating materials, such as ceramics.

[0030] The present invention adopts a copper-based micromachining process. Compared with the commonly used planar PCB process, the planar transmission line has a higher transmission loss in the high frequency band, while the micro-coaxial line has a small insertion loss, and its advantages are particularly obvious at high frequencies, and the signal shielding is high. The three-dimensional structure manufactured by using the rectangular micro-coaxial process is convenient for three-dimensional integrated processing and integration of the device, and has a small size and high precision of micron level. At the same time, multiple transmission zeros are introduced by using source-load coupling, which has a strong out-of-band suppression capability. In addition, the filter has a simple and compact structure, and has good out-of-band suppression capability and small loss, and has good application prospects in modern wireless communication systems. .

[0031] The size specifications of the present invention are as follows Figure 5 As shown: the horizontal area of ​​the present invention is 5.388×3.472mm², and a 5-layer process design is adopted. The height of each layer is the same, the total height is 0.5mm, the inner conductor width is 0.195mm, and the height is 0.1mm. Figure 4 , 5 The size parameters of the dual-passband filter are as follows: W1 = 0.19mm, W2 = 0.13mm, Wp = 0.195mm, gap =0.135mm, gap1 = 0.1mm, Ls = 0.16mm, Lp = 0.3mm, L1 = 0.73mm, L2 = 2.07mm, L3 = 0.8mm, n = 0.712mm, n1 = 0.53mm, m = 0.14mm, s = 0.074mm.

[0032] The present invention is modeled and simulated in the electromagnetic simulation software Ansys Electronics Desktop 2022R1, such as Figure 5 As shown, the passband center frequencies of the dual-passband filter are 20.6 GHz and 29.44 GHz, respectively; the in-band return losses are better than 20.31 dB and 22.29 dB, respectively; the insertion losses are less than 0.91 dB and 0.68 dB, respectively; and the two zeros outside the passband at 17.53 GHz and 22.87 GHz improve the out-of-band suppression capability of the dual-passband filter.

[0033] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0034] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A dual-passband filter based on copper-based micromachining technology, characterized in that: The invention comprises a coaxial outer conductor (1) and a coaxial inner conductor (2) located inside the coaxial outer conductor (1); an input end feeder (3) and an output end feeder (4) are connected to the coaxial inner conductor (2); the coaxial inner conductor (2) comprises a first quarter wavelength transmission line (21), a second quarter wavelength transmission line (22), a first half wavelength transmission line (23) and a second half wavelength transmission line (24); the first quarter wavelength transmission line (21) and the second quarter wavelength transmission line (22) are coupled to each other; the first quarter wavelength transmission line (21) and the first half wavelength transmission line (23) are coupled to each other; the second quarter wavelength transmission line (22) and the second half wavelength transmission line (24) are coupled; and the first half wavelength transmission line (23) and the second half wavelength transmission line (24) are coupled to each other.

2. The dual-passband filter based on copper-based micromachining technology according to claim 1, characterized in that: The coaxial outer conductor (1) adopts a rectangular micro-coaxial five-layer process design in its height direction, each layer has the same height, and the coaxial inner conductor (2) is located in the third layer of the coaxial outer conductor (1).

3. The dual-passband filter based on copper-based micromachining technology according to claim 1, characterized in that: The first quarter-wavelength transmission line (21) and the second quarter-wavelength transmission line (22) are connected via a short-circuit grounding line (6); the first half-wavelength transmission line (23) and the second half-wavelength transmission line (24) are both bent in a "J" shape; the first half-wavelength transmission line (23) is connected to an input end feeder line (3); and the second half-wavelength transmission line (24) is connected to an output end feeder line (4).

4. The dual-passband filter based on copper-based micromachining technology according to claim 3, characterized in that: The first half-wavelength transmission line (23) and the second half-wavelength transmission line (24) are symmetrically arranged, and the two X-shaped openings face each other, and the first quarter-wavelength transmission line (21) and the second quarter-wavelength transmission line (22) are located on the inner sides of the two openings.

5. The dual-passband filter based on copper-based micromachining technology according to claim 1, characterized in that: The impedance of the input end feeder (3) and the output end feeder (4) are both 50 ohms.

6. The dual-passband filter based on copper-based micromachining technology according to claim 1, characterized in that: A plurality of rectangular release holes (7) are provided at intervals on the outer side wall of the coaxial outer conductor (1).

7. The dual-passband filter based on copper-based micromachining technology according to claim 1, characterized in that: The dielectric support strip (5) is inserted into the third layer of the coaxial outer conductor (1), and the lower surface of the dielectric support strip (5) is flush with the lower surface of the coaxial inner conductor (2), so as to fix the coaxial inner conductor (2).

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