Single-layer film metal millimeter wave band-pass filter

Abstract

The invention discloses a thin film metal band-pass filter, and belongs to the technical field of communication, the filter is manufactured on a high-resistivity substrate, the substrate is provided with a first grounding end and a second grounding end, a CPW structure is arranged between the first grounding end and the second grounding end, the CPW structure comprises first metal microstrip lines which are symmetrically arranged, and second metal microstrip lines which are symmetrically arranged are arranged between the first metal microstrip lines and the second metal microstrip lines. Two ends of the first metal microstrip line are respectively connected with the radio frequency input and the radio frequency output, and the second metal microstrip line and the third metal microstrip line are vertically arranged. The filter is compatible with a low-dimensional channel material processing process, can be used for preparing a monolithic microwave integrated circuit and is arranged on the front surface of a dielectric substrate, and a microstrip filter is used for allowing a frequency-selecting signal to pass through. According to the invention, the insertion loss is further reduced and the bandwidth is expanded by simplifying a miniaturized architecture, and the technical effects that the integrated circuit board is small in size and high in integration level, and the influence on the performance limitation of the filter is small are achieved.

Description

Technical Field

[0001] The present application belongs to the field of communication technology, and in particular relates to a bandpass filter under a single-layer thin-film metal radio frequency passive process for a monolithic microwave integrated circuit of low-dimensional channel materials such as carbon nanotubes. Background Art

[0002] In the early stage of research on monolithic microwave integrated circuits of low-dimensional channel materials, a single-layer thin film metal with a thickness of only 300-400 nm was used for RF passive processing technology, which is compatible with the processing of low-dimensional channel materials and is easy to integrate single-frequency microwaves to achieve on-chip frequency selection of RF signals.

[0003] Millimeter-wave bandpass filters are usually composed of capacitors and inductors equivalent to RF transmission lines. The use of coplanar waveguide structure solves the RF ground problem under single-layer metal process, making it easier to integrate with active devices of low-dimensional channel materials, and has received attention in recent years.

[0004] Thin film filters play an indispensable role in communication systems due to their high frequency of use, easy integration, compact structure, light weight and low processing cost. Such filters usually use a dielectric substrate with a high dielectric constant and are manufactured using sophisticated thin film processing technology. Due to their excellent harmful signal suppression function, thin film filters have been widely used in the field of modern signal processing.

[0005] In the face of the rapid development of mobile communications and high-frequency communication technologies, how to further reduce the size of thin-film filters to achieve better integration and applicability while ensuring filtering performance has become an important challenge in current technological development. How to integrate filters into compact circuit boards still has problems such as large size and low integration, as well as limited filter performance.

[0006] In view of the above problems, the present application proposes a bandpass filter using a single-layer thin-film metal radio frequency passive process for a monolithic microwave integrated circuit using low-dimensional channel materials such as carbon nanotubes. Summary of the invention

[0007] In order to solve the deficiencies of the prior art, the present application provides a millimeter wave bandpass filter under a single-layer thin-film metal RF passive process for a monolithic microwave integrated circuit of low-dimensional channel materials such as carbon nanotubes, which is used to solve the problems of large volume and low integration of filters integrated in compact circuit boards in the prior art, as well as limited filter performance. It can be combined with carbon-based RF active devices and integrated on the same substrate to form a carbon-based monolithic microwave integrated circuit.

[0008] The technical effects to be achieved by this application are achieved through the following solutions: In a first aspect, the present application provides a thin film metal bandpass filter, wherein the filter is fabricated on a high resistivity substrate, wherein a first ground terminal and a second ground terminal are provided on the substrate, and a CPW structure is provided between the first ground terminal and the second ground terminal, wherein the CPW structure comprises a first metal microstrip line, a second metal microstrip line and a third metal microstrip line which are symmetrically arranged, wherein the two ends of the first metal microstrip line are respectively connected to a radio frequency input and a radio frequency output, and the second metal microstrip line is arranged perpendicular to the third metal microstrip line.

[0009] In some embodiments, the symmetrically arranged first metal microstrip lines form a cavity.

[0010] In some embodiments, the second metal microstrip line and the third metal microstrip line are disposed in the cavity, and the third metal microstrip line is vertically disposed in the middle of the second metal microstrip line.

[0011] In some embodiments, the width of the first metal microstrip line is smaller than the vertical width of the second metal microstrip line, and the width of the second metal microstrip line is smaller than the vertical width of the third metal microstrip line.

[0012] In some embodiments, the first metal microstrip line includes a first portion and a second portion, wherein a gap is formed between an end of the first portion and an end of the second portion, and an end of the third metal microstrip line is disposed in the gap.

[0013] In some embodiments, the high resistivity substrate is a substrate made of any one of Si, BeO, AlO3, and diamond.

[0014] In some embodiments, the deposited metal is a 400 nm Au thin film.

[0015] In some embodiments, the CPW structure is periodic.

[0016] In some embodiments, the dielectric constant of the substrate is 11.9.

[0017] In some embodiments, the lengths and widths of the first metal microstrip line, the second metal microstrip line, and the third metal microstrip line are adjustable.

[0018] The thin film metal bandpass filter provided in the present application adopts a hybrid coupling mode and can achieve filtering by adjusting the CPW line width and the distance between the signal line and the ground, thereby solving the problem of high insertion loss of existing thin film filters, and further reducing insertion loss and expanding bandwidth by simplifying the miniaturized architecture. It can be integrated with RF active devices of low-dimensional channel materials to realize a monolithic microwave integrated circuit, achieving the technical effect of small size and high integration of the integrated circuit board, and less impact on the performance limitation of the filter. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present application or the existing technical solutions, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 FIG. 4 is a schematic diagram of the structure of a thin film metal bandpass filter in an embodiment of the present application.

[0021] Figure 2 4 is a schematic diagram of a cascade connection of a thin film metal bandpass filter in an embodiment of the present application.

[0022] Figure 3 FIG. 4 is a schematic diagram of an equivalent circuit of a thin film metal bandpass filter in an embodiment of the present application.

[0023] Figure 4 The diagrams are simulation and measurement diagrams of a thin film metal bandpass filter in one embodiment of the present application.

[0024] Figure 5 A schematic diagram of the active device layout of a radio frequency active device of a low-dimensional channel material in an embodiment of the present application.

[0025] Figure 6 Schematic diagram of active device integration of a thin film metal millimeter wave bandpass filter and a radio frequency active device of a low-dimensional channel material in one embodiment of the present application. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the present application clearer, the technical solution of the present application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0027] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in one or more embodiments of the present application should be understood by people with ordinary skills in the field to which the present application belongs. The "first", "second" and similar words used in one or more embodiments of the present application do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0028] Although some progress has been made in the miniaturization of filters in related technologies, enabling them to be integrated into compact circuit boards, they still face the problems of large size and low integration. These problems not only limit the performance of the filter, especially in terms of filtering effect and bandwidth, but also affect its applicability in highly integrated circuits.

[0029] Faced with the rapid development of mobile communications and high-frequency communication technologies, how to further reduce the size of thin-film filters to achieve better integration and applicability while ensuring filtering performance has become an important challenge in current technological development.

[0030] This challenge involves not only innovations in materials science, but also optimization of filter design in electronic engineering, with the goal of achieving higher performance and a wider range of applications. Future research needs to focus on developing new materials and technologies to meet these high standards, especially in the context of the global push for 5G and higher communication standards. The high carrier mobility of carbon nanotubes makes carbon-based circuits have broad application prospects in the fields of space communications, high-speed wireless circuits, and radio frequency circuits for vehicle radar signal propagation.

[0031] Millimeter-wave electronic system products currently have broad market opportunities and are evolving towards high integration, high resolution, and smaller size. How to achieve higher resolution and higher gain of high-resolution millimeter-wave electronic systems and integration with carbon-based circuits has an important impact on improving the performance of millimeter-wave electronic system products.

[0032] Therefore, it is necessary to adopt the thin film metal bandpass filter provided by the present application to solve the above problems.

[0033] This application aims to solve a technical problem in the microwave and millimeter wave fields, namely how to exploit the slow-wave characteristics of periodic structures to realize miniaturized low-loss filters. Slow-wave structures do not perform well in chip sizes limited by passive components due to the large number of periods required to achieve deep attenuation levels and the increased insertion loss associated with them.

[0034] Therefore, this application proposes a new periodic structure design to overcome the limitations of traditional slow-wave structures and realize miniaturized low-loss filters while maintaining high performance and deep attenuation levels. By introducing periodic changes to increase the inductance and capacitance of the transmission line, slow-wave propagation is achieved while reducing the filter size and insertion loss, thereby solving the size and performance issues in microwave integrated circuits and monolithic integrated circuits.

[0035] The present application effectively increases the inductance and capacitance of the transmission line by introducing periodic changes along the propagation direction, such as drilling holes in a substrate or etching patterns on a microstrip ground plane, thereby achieving slow wave propagation.

[0036] Propose periodic structural units, such as narrowing the width of the coplanar waveguide center conductor to increase the inductance per unit length, and placing the two ground planes of the coplanar waveguide close to the center conductor to increase the capacitance with the ground. Design an equivalent circuit model of the periodic structure for circuit analysis and performance evaluation.

[0037] The performance of the designed periodic structure, including filtering characteristics, spurious responses, and attenuation levels, is verified through simulation and measured responses. The loss characteristics of the periodic structure are considered to ensure low insertion loss in the passband region to achieve high-performance filter applications.

[0038] The core invention of this design technology is to use the slow-wave characteristics of periodic structures in coplanar waveguide transmission lines to realize miniaturized low-loss filters. By introducing periodic changes to increase the inductance and capacitance of the transmission line, slow-wave propagation can be achieved while reducing the filter size and insertion loss. This design method can be applied to microwave integrated circuits and monolithic integrated circuits, helping to reduce chip size.

[0039] Various non-limiting implementations of the present application are described in detail below in conjunction with the accompanying drawings.

[0040] First, refer to Figure 1 , the thin film metal bandpass filter of the present application is described in detail: The present application provides a thin film metal bandpass filter, which is manufactured on a high-resistivity substrate 3, on which a first ground terminal 4 and a second ground terminal 5 are provided, and a CPW structure (coplanar waveguide structure) is provided between the first ground terminal and the second ground terminal, wherein the CPW structure comprises a first metal microstrip line 6, a second metal microstrip line 7 and a third metal microstrip line 8 which are symmetrically arranged, wherein the two ends of the first metal microstrip line 6 are respectively connected to a radio frequency input 1 and a radio frequency output 2, and the second metal microstrip line 7 is arranged perpendicular to the third metal microstrip line 8.

[0041] For example, the above-mentioned thin film metal bandpass filter can be cascaded through a 50Ω transmission line 9 (refer to Figure 2 ), multiple metal bandpass filters are cascaded through transmission line 9. Specifically, the RF output of a metal bandpass filter can be connected to the transmission line 9, and then connected to the RF input of another metal bandpass filter through the transmission line 9, so as to achieve the purpose of cascading different metal bandpass filters, wherein the transmission line is 50Ω for example, and transmission lines with other impedance parameters can be applied here.

[0042] In some embodiments, the symmetrically arranged first metal microstrip lines form a cavity, and the cavity is rectangular.

[0043] In some embodiments, the second metal microstrip line and the third metal microstrip line are disposed in the cavity, and the third metal microstrip line is vertically disposed in the middle of the second metal microstrip line, and the two form a cross structure.

[0044] In some embodiments, the width of the first metal microstrip line is smaller than the vertical width of the second metal microstrip line, and the width of the second metal microstrip line is smaller than the vertical width of the third metal microstrip line.

[0045] In some embodiments, the first metal microstrip line includes a first part and a second part, wherein a gap is formed between an end of the first part and an end of the second part, and an end of the third metal microstrip line is arranged in the gap. Specifically, the first part and the second part are symmetrically arranged, each part is U-shaped, and a gap is formed at the opposite ends of the U-shaped mouths.

[0046] In some embodiments, the high-resistivity substrate is a substrate made of any one of Si, BeO, AlO3, and diamond; wherein BeO, AlO3, and diamond are substrates with good heat dissipation performance; the dielectric constant of the substrate may be 11.9, and the resistivity may be ρ>4000Ω / cm, which is for exemplary purposes only, and substrates with other parameters may also be used here without limitation.

[0047] Specifically, according to the formula of skin depth: , the substrate can be a 400nm Au thin film.

[0048] In some embodiments, the CPW structure is periodic.

[0049] In some embodiments, the lengths and widths of the first metal microstrip line, the second metal microstrip line, and the third metal microstrip line are all adjustable, so bandpass filters of different frequency bands can be implemented together with their coupling spacings.

[0050] Since the fields in a microstrip line are concentrated in the dielectric substrate region, these periodic variations strongly perturb the properties of the microstrip field distribution. In contrast, the fields in a CPW are localized in the two slots, so penetrating the two ground planes has little effect on the propagation of the CPW guided waves. Therefore, in order to increase the effective inductance and capacitance along the CPW line, a Figure 1 The structure shown. The width of the CPW center conductor is narrowed, which enhances the inductance per unit length. To increase the capacitance to ground, the two ground planes of the CPW line are brought close to the center conductor.

[0051] The advantage of the above-mentioned thin film metal bandpass filter setting is that it can form coupling through the interdigital structure and allow the current to pass slowly, reducing interference and improving high-end suppression. In actual production, it can also avoid the influence of the through-hole size error on the center frequency, making the center frequency more stable.

[0052] Figure 3 FIG. 1 is a schematic diagram of an equivalent circuit of a thin film metal bandpass filter in an embodiment of the present application. Figure 3 Provide explanation.

[0053] As can be seen from the figure, the equivalent circuit of the filter includes an RF input and an RF output, which are respectively connected to their respective resistors L0. The equivalent circuit also includes resistors L1 / L2 / L3 and capacitors C0 / C1. The specific structure can be seen in Figure 2 The filter can change the center frequency by adjusting the length of the resonator, and can also change the coupling amount by adjusting the staggered amount of adjacent resonators (i.e., changing or adjusting the length and width of the first metal microstrip line, the second metal microstrip line, and the third metal microstrip line). Specifically, reducing the values ​​of C0 and C1 can increase the center frequency, and increasing the values ​​of L2 and L3 can reduce the center frequency.

[0054] Figure 4 The simulation and measurement diagram of the thin film metal bandpass filter in one embodiment of the present application. Through the simulation and measurement of the above filter, it can be obtained Figure 4 , the specific simulation process is as follows: First, determine the electrical performance indicators of the above-mentioned filter, such as bandwidth, center frequency, out-of-band suppression and insertion loss, and determine the type of the above-mentioned filter to be selected. The present application adopts the above-mentioned filter circuit structure based on capacitive coupling; Second, confirm the order of the above filter according to the bandwidth, center frequency and insertion loss indicators, and confirm the resonant frequency of the above filter (including filters of each order); Third, create a simulation schematic in ADS (Advanced Design System, simulation software), set the filter parameters of the preliminary design and simulate to obtain the preliminary results of the filter; Fourth, add target and optimization controls in the simulation software ADS, use the two controls of the target value (GOAL) and optimization function (Optimize) of the ADS software to optimize the S parameters of the above filter, set the target value and optimization variables, and use the Optimize function of ADS to automatically optimize until the optimization process is completed when the target value is approached; Fifth, determine the optimized filter parameters to complete the design of the above filter.

[0055] refer to Figure 3 It can be seen that the horizontal axis represents frequency (GHz) and the numerical axis represents S parameter (dB). The figure shows |S 11 |Related curves, including simulation values ​​|S 11 |(Simulated|S 11 |) and the measured value |S 11 |(Measured|S 11 |), and also shows |S 21 |Related curves, including simulation values ​​|S 21 |(Simulated|S 21 |) and the measured value |S 21 |(Measured|S 21 |).

[0056] It can be seen that the measured S parameters also show that the return loss at 30-50 GHz is more than 10 dB, the return loss at the center frequency is lower but the insertion loss is higher than the simulation; the insertion loss is less than 2 dB in the passband, with a minimum value of 1.1 dB; the measured input return loss is better than 10 dB from 30 to 50 GHz.

[0057] The thin film metal bandpass filter provided above adopts a hybrid coupling mode and can achieve filtering by adjusting the CPW line width and the distance between the signal line and the ground, thereby solving the problem of high insertion loss of existing thin film filters, and further reducing insertion loss and expanding bandwidth by simplifying the miniaturized architecture, thereby achieving the technical effect of small size and high integration of the integrated circuit board, and less impact on the performance limitation of the filter.

[0058] The thin film metal bandpass filter of the present application can achieve the following advantages: 1. No need to drill holes, reducing process steps.

[0059] 2. The slow-wave characteristics exhibited by the periodic structure can reduce the size of microstrip circuit components.

[0060] 3. The slow-wave characteristics of the periodic structure can reduce the size of microstrip circuit elements, which helps to reduce the chip size limited by passive components, thereby promoting the miniaturization of microwave integrated circuits and monolithic integrated circuits.

[0061] 4. Planar design, compatible with thin film carbon-based device processes.

[0062] 5. Reduce insertion loss and improve signal integrity.

[0063] 6. No additional ion implantation or cross-bonding cover layer procedures are required, and the minimum size of the unit cell is still large enough, so only photolithography is required. This design simplifies the manufacturing process, improves manufacturing efficiency, and ensures the stability and reliability of the structure.

[0064] It should be noted that the method of one or more embodiments of the present application can be performed by a single device, such as a computer or server. The method of this embodiment can also be applied to a distributed scenario and completed by multiple devices cooperating with each other. In the case of such a distributed scenario, one of the multiple devices can only perform one or more steps in the method of one or more embodiments of the present application, and the multiple devices will interact with each other to complete the described method.

[0065] It should be noted that the above describes specific embodiments of the present application. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recorded in the claims can be performed in an order different from that in the embodiments and still achieve the desired results. In addition, the processes depicted in the accompanying drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0066] Based on the same inventive concept, corresponding to any of the above-mentioned embodiments and methods, one or more embodiments of the present application also provide a non-transitory computer-readable storage medium, wherein the non-transitory computer-readable storage medium stores computer instructions, and the computer instructions are used to enable the computer to execute the thin film metal bandpass filter described in any of the above embodiments.

[0067] The computer-readable medium of this embodiment includes permanent and non-permanent, removable and non-removable media, and information storage can be implemented by any method or technology. Information can be computer-readable instructions, data structures, modules of programs, or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, read-only compact disk read-only memory (CD-ROM), digital versatile disk (DVD) or other optical storage, magnetic cassettes, tape disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device.

[0068] The computer instructions stored in the storage medium of the above embodiment are used to enable the computer to execute the thin film metal bandpass filter described in any of the above embodiments, and have the beneficial effects of the corresponding method embodiments, which will not be repeated here.

[0069] A person skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present application (including the claims) is limited to these examples. In line with the concept of the present application, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of different aspects of one or more embodiments of the present application as described above, which are not provided in detail for the sake of simplicity.

[0070] In addition, to simplify the description and discussion, and in order not to make one or more embodiments of the present application difficult to understand, the well-known power / ground connections to the integrated circuit (IC) chip and other components may or may not be shown in the provided figures. In addition, the device may be shown in the form of a block diagram to avoid making one or more embodiments of the present application difficult to understand, and this also takes into account the fact that the details of the implementation of these block diagram devices are highly dependent on the platform on which one or more embodiments of the present application will be implemented (that is, these details should be fully within the scope of understanding of those skilled in the art). Where specific details (e.g., circuits) are set forth to describe exemplary embodiments of the present application, it is obvious to those skilled in the art that one or more embodiments of the present application can be implemented without these specific details or with changes in these specific details. Therefore, these descriptions should be considered illustrative rather than restrictive.

[0071] Although the present application has been described in conjunction with specific embodiments of the present application, many alternatives, modifications and variations of these embodiments will be apparent to those skilled in the art from the foregoing description. For example, other memory architectures (e.g., dynamic RAM (DRAM)) may use the discussed embodiments.

[0072] One or more embodiments of the present application are intended to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of one or more embodiments of the present application should be included in the scope of protection of the present application.

Claims

1. A thin film metal bandpass filter, characterized in that: The filter is manufactured on a high-resistivity substrate, a first ground terminal and a second ground terminal are provided on the substrate, a CPW structure is provided between the first ground terminal and the second ground terminal, the CPW structure comprises a first metal microstrip line, a second metal microstrip line and a third metal microstrip line which are symmetrically arranged, wherein the two ends of the first metal microstrip line are respectively connected to a radio frequency input and a radio frequency output, and the second metal microstrip line is vertically arranged to the third metal microstrip line.

2. The thin film metal bandpass filter according to claim 1, characterized in that: The symmetrically arranged first metal microstrip lines form a cavity.

3. The thin film metal bandpass filter according to claim 2, characterized in that: The second metal microstrip line and the third metal microstrip line are arranged in the cavity, and the third metal microstrip line is vertically arranged in the middle of the second metal microstrip line.

4. The thin film metal bandpass filter according to claim 3, characterized in that: The width of the first metal microstrip line is smaller than the vertical width of the second metal microstrip line, and the width of the second metal microstrip line is smaller than the vertical width of the third metal microstrip line.

5. The thin film metal bandpass filter according to claim 4, characterized in that: The first metal microstrip line includes a first portion and a second portion, wherein a gap is formed between an end of the first portion and an end of the second portion, and an end of the third metal microstrip line is disposed in the gap.

6. The thin film metal bandpass filter according to claim 1, characterized in that: The high resistivity substrate is a substrate made of any material among Si, BeO, AlO3 and diamond.

7. The thin film metal bandpass filter according to claim 6, characterized in that: The deposited metal is a 400nm Au film.

8. The thin film metal bandpass filter according to claim 1, characterized in that: The CPW structure is periodic.

9. The thin film metal bandpass filter according to claim 1, characterized in that: The dielectric constant of the substrate is 11.

9.

10. The thin film metal bandpass filter according to claim 1 or 8, characterized in that: The lengths and widths of the first metal microstrip line, the second metal microstrip line and the third metal microstrip line are all adjustable.

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