Double-layer stacked microstrip band-pass filter

Abstract

The invention belongs to the technical field of integrated circuit manufacturing and filters, and discloses a double-layer stacked microstrip band-pass filter. The filter comprises an upper metal layer, an upper substrate, a middle metal layer, a lower substrate and a lower metal layer which are sequentially arranged from top to bottom. A double-layer stacking method is adopted, the multi-order resonators are placed on the lower glass substrate, the upper metal layer, the side wall metalized through holes and the lower metal layer form a metal cavity structure, and the size of the filter is remarkably reduced; the multi-order resonator adopts a stepped impedance resonator structure, so that a low-frequency end zero point generated by high-order mode coupling can be effectively used, and better out-of-band rejection can be obtained; a ceramic substrate or a glass substrate with a relatively large dielectric constant is selected, so that the high-frequency loss of a passive device is remarkably reduced, and the quality factor is improved.

Description

Technical Field

[0001] The present invention mainly relates to the field of integrated circuit manufacturing and filter technology, and in particular to a double-layer stacked microstrip bandpass filter. Background Art

[0002] The filter is one of the key components in radar, communication and measurement systems. Its function is to allow a certain frequency signal to pass smoothly, while suppressing the signals of other frequencies. Its performance has an important impact on the performance of the entire system. The technical indicators of the filter include passband bandwidth, return loss, out-of-band suppression, etc. Microstrip filters have the advantages of small size, light weight, wide frequency band, high reliability and low manufacturing cost. They are a widely used type of transmission line filter.

[0003] With the increasing requirements for miniaturization and integration, three-dimensional integration technology stacks traditional two-dimensional integrated circuits vertically, and through-silicon vias (TSVs) are key structures in three-dimensional integrated circuits. Traditional microstrip filters are difficult to integrate into the chips of three-dimensional systems due to the low dielectric constant of the silicon-based substrate, and silicon has the physical properties of semiconductors, which affects the performance of the filter. At present, how to make microstrip filters with miniaturized size and easy integration packaging is an urgent problem to be solved. Summary of the invention

[0004] The purpose of the present invention is to provide a double-layer stacked microstrip bandpass filter, which significantly reduces the size of the filter, reduces the high-frequency loss of passive components, and obtains better out-of-band suppression function by adopting a double-layer stacking method.

[0005] To achieve the above object, the present invention provides a double-layer stacked microstrip bandpass filter, comprising an upper metal layer, an upper substrate, an intermediate metal layer, a lower substrate and a lower metal layer arranged in sequence from top to bottom; The upper substrate is provided with a plurality of through holes, and the side walls of the through holes are metallized; The middle metal layer includes a first metal layer located on the lower surface of the upper substrate and a second metal layer located on the upper surface of the lower substrate, and the second metal layer on the upper surface of the lower substrate is provided with an input port and an output port; A plurality of through holes are arranged on the lower substrate, and the side walls of the through holes are metallized.

[0006] Further, the size of the upper metal layer, the size of the upper substrate, the size of the middle metal layer, the size of the lower substrate and the size of the lower metal layer all include the size in the first direction, the size in the second direction and the size in the third direction; In the first direction and the second direction, the upper metal layer and the upper substrate have the same size, and the lower substrate and the lower metal layer have the same size; In the first direction, the size of the lower substrate is larger than that of the upper substrate; In the second direction and the third direction, the size of the lower substrate is the same as the size of the upper substrate, and the size of the upper metal layer is the same as the size of the lower metal layer; The upper substrate and the lower substrate are connected by metal bonding. After the metal bonding, the upper substrate is located above the center of the lower substrate.

[0007] Furthermore, the input port and the output port are arranged at the center position of the short side of the second metal layer in the second direction. Except for the positions of the input port and the output port of the second metal layer, no through holes are set. The periphery of the upper substrate, the periphery of the middle metal layer and the periphery of the lower substrate are all set with equidistant corresponding through holes in the first direction and the second direction.

[0008] Furthermore, bonding metal bodies of equal distance and same size are arranged between the through holes of the first metal layer and the through holes of the second metal layer.

[0009] Further, the through holes at the periphery of the upper substrate, the periphery of the middle metal layer and the periphery of the lower substrate are axisymmetric with respect to a straight line passing through the input port and the output port in the first direction.

[0010] Furthermore, within the range formed by the through hole of the second metal layer, an input port, a plurality of order resonators, and an output port are arranged along the first direction; The first metal layer is connected to the upper metal layer through a through hole with sidewall metallization, and is connected to the second metal layer through a bonding metal body; The second metal layer is connected to the lower metal layer through a through hole with sidewall metallization, and is connected to the first metal layer through a bonding metal body.

[0011] Furthermore, the multi-order resonator is a step impedance resonator, and the bonding metal body is a bonding metal ball.

[0012] Furthermore, the metals used in the upper metal layer, the middle metal layer and the lower metal layer are all the same.

[0013] Furthermore, the upper substrate and the lower substrate are made of ceramic or glass.

[0014] Furthermore, the metals used in the upper metal layer, the middle metal layer and the lower metal layer are all gold.

[0015] Beneficial effects: The present invention provides a double-layer stacked microstrip bandpass filter, which adopts a double-layer stacking method to place a number-order resonator on a lower glass substrate, and the upper metal layer, the side wall metallized through-holes and the lower metal layer form a metal cavity structure, which significantly reduces the size of the filter; the number-order resonator adopts a step impedance resonator structure, which can effectively use the low-frequency end zero point generated by high-order mode electrical coupling to obtain better out-of-band suppression; a ceramic substrate or a glass substrate with a large dielectric constant is selected to significantly reduce the high-frequency loss of passive devices and improve the quality factor. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural front view of a double-layer stacked microwave bandpass filter involved in an embodiment of the present invention; Figure 2 is a structural top view of a double-layer stacked microwave bandpass filter involved in an embodiment of the present invention; Figure 3 is a top view of an upper metal layer of a double-layer stacked microwave bandpass filter according to an embodiment of the present invention; Figure 4 is a top view of a first metal layer of an intermediate metal layer of a double-layer stacked microwave bandpass filter according to an embodiment of the present invention; Figure 5 is a top view of a second metal layer of an intermediate metal layer of a double-layer stacked microwave bandpass filter according to an embodiment of the present invention; Figure 6 is a top view of a lower metal layer of a double-layer stacked microwave bandpass filter according to an embodiment of the present invention; Figure 7 is a high-order mode electric field intensity distribution diagram of a single resonator in a double-layer stacked microwave bandpass filter involved in an embodiment of the present invention; Figure 8 It is a frequency response diagram of a double-layer stacked microwave bandpass filter involved in an embodiment of the present invention.

[0018] Description of reference numerals: Among them: 1 is the upper metal layer; 2 is the upper substrate; 3 is the middle metal layer; 4 is the lower substrate; 5 is the lower metal layer; 6 is the input port; 7 is the output port; 8 is the side wall metallized through hole; 9 is the metal bonding ball; 10 is the multi-order resonator. DETAILED DESCRIPTION

[0019] The preferred mechanism and implementation method of the present invention are further described below in conjunction with the accompanying drawings and specific implementation methods.

[0020] The electromagnetic resonance modes of the filter in this embodiment are mainly TE101 and TE201, and the passband is 7 GHz-8 GHz. Figures 1 to 6 , Figure 1 1 is a structural front view of a double-layer stacked microwave bandpass filter according to an embodiment of the present invention. Figure 2 is a top view of the structure of a double-layer stacked microwave bandpass filter according to an embodiment of the present invention, Figures 3 to 6 They are respectively a top view of the upper metal layer, the first metal layer of the middle metal layer, the second metal layer of the middle metal layer and the bottom metal layer of the double-layer stacked microwave bandpass filter according to the embodiment of the present invention. Figure 1 As shown, the double-layer stacked microwave bandpass filter of this embodiment includes an upper metal layer 1, an upper substrate 2, an intermediate metal layer 3 (including a first metal layer and a second metal layer), a lower substrate 4 and a lower metal layer 5, which are arranged in sequence from top to bottom. Among them, the metal pattern of the upper metal layer 1 is the same as that of the upper substrate, the material is gold, and the film thickness is 5μm; the upper substrate 2 uses a glass ceramic with a dielectric constant of 32.2 at 1-15GHz, the substrate thickness is 254μm, and there is a circle of equidistantly arranged sidewall metallized through holes 9 on the periphery of the substrate, the diameter of the through hole is 100μm, and the metallized material of the through hole is the same as that of the upper substrate. The sidewall metallized through hole can connect the upper metal layer with the first metal layer of the intermediate metal layer, and can also be used as a metal cavity to shield part of the electromagnetic field, so that the size of the filter can be further reduced; the first layer of metal of the intermediate metal layer 3 is made of gold, the film thickness is 5μm, and the shape is The middle metal layer 3 is distributed in a U-shaped pattern. Except for the positions of the input port and the output port on both sides in the first direction, the first metal layer of the middle metal layer 3 is connected to the upper metal layer 1 through the side wall metallization through hole, and is also connected to the second metal layer of the middle metal layer 3 through the bonding metal ball 9; the second metal layer of the middle metal layer 3 is made of gold, with a film thickness of 5μm, and the outer shape is axisymmetric about the straight line in the first direction passing through the input port and the output port. Except for the positions of the input port and the output port on both sides in the first direction, the second metal layer of the middle metal layer 3 is connected to the lower metal layer 5 through the side wall metallization through hole, and is also connected to the first metal layer of the middle metal layer 3 through the bonding metal ball 9. The middle part of the second metal layer of the middle metal layer 3 is the input port, the sixth-order resonant cavity, and the output port; the material and thickness of the lower substrate 4 are the same as those of the upper substrate 2; the pattern of the lower metal layer 5 is the same as the lower surface of the lower substrate, and the metal material and thickness are consistent with those of the upper metal layer 1.

[0021] Specifically, the first-order resonant cavity in the second metal layer of the intermediate metal layer 3 is connected to the input port, and the sixth-order resonant cavity is connected to the output port. The width of the input port and the output port and the distance between the input port and the output port and the peripheral metal jointly regulate the impedance of the port. In this embodiment, the width of the input port and the output port is set to 50μm, and the distance between the input port and the output port and the peripheral metal is 300μm, so that the matching impedance is 50Ω. In this embodiment, the input and output ports are both at the center of the short side of the filter. In order to better match the tap position, a bending line is selected to connect the input and output ports to the first-order resonator and the sixth-order resonator.

[0022] Furthermore, in this embodiment, the metal layer of the second metal layer of the intermediate metal layer forms a filter resonant cavity, and the resonant cavity uses a quarter-wavelength resonator, whose parasitic frequency is 3 times the fundamental frequency, and the parasitic passband of the filter is at 3 times the fundamental frequency, which can effectively improve the out-of-band suppression. The resonator is a step impedance resonator structure. Compared with the uniform impedance resonator structure, the step impedance resonator structure has one more degree of freedom in structural design, and can flexibly adjust the length and width of the transmission line to achieve the miniaturization of the resonator. On the other hand, it can better utilize the high-order mode coupling between resonators. Figure 7 This is a high-order mode electric field intensity distribution diagram of a single resonator in the double-layer stacked microwave bandpass filter of this embodiment. The resonators are arranged in an interdigitated manner, which can better couple the resonators, thereby generating a zero point at the low-frequency end of the filter passband through bypass coupling, and the coupling position is regulated by controlling the strength of the coupling.

[0023] Furthermore, the resonant cavity uses a resonator with a step impedance resonator structure, which can reduce the metal loss of the resonator along the length direction, but the increase in equivalent capacitance increases the dielectric loss of the resonator, so the Q value of the resonator is slightly lower than that of the uniform impedance resonator structure.

[0024] Furthermore, the Q value of the resonator is related to the metallized through hole at the open end, and the Q value of the resonator increases with the increase of the aperture. In this embodiment, the size of the resonator through hole is consistent with the size of the peripheral metal through hole, both of which are 100 μm.

[0025] The working process of the filter in this embodiment is as follows: first, the electromagnetic wave to be filtered is input from the input port to the first-order resonator; then, it is magnetically coupled and transmitted to the second-order resonator through the first-order resonator, and is transmitted to the second-order resonator through bypass coupling; each order of resonators is coupled and propagated in turn, and finally the filtered electromagnetic wave is output from the output port. Figure 8This is the frequency response diagram of the double-layer stacked microwave bandpass filter of this embodiment. As shown in the figure, the passband frequency is 7 to 8 GHz, the zero point generated by bypass coupling is at 4.4 GHz, and the zero point generated by crosstalk is at 9.3 GHz. Compared with the frequency response diagram of the filter without zero points at low frequency, this embodiment effectively utilizes the zero point of bypass coupling, further reducing the transmission coefficient at the low-frequency end of the passband (4.4 GHz to 6.8 GHz), thereby obtaining better out-of-band suppression. In filters with ordinary interdigital structures, the zero point position is often far away from the passband or there is no zero point, which cannot be used to enhance out-of-band suppression. This embodiment adjusts the zero point position to 4.4 GHz by regulating the high-order mode coupling (bypass coupling) between resonators, thereby effectively improving out-of-band suppression.

[0026] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0027] The length of the step impedance part of the first to sixth order resonators is 600μm and the width is 600μm; the total length of the first to sixth order resonators are 1574μm, 1535μm, 1539μm, 1539μm, 1535μm, 1574μm, and the width is 120μm. The eigenmode frequency of a single resonator is around 7.461GHz. The diameter of the hole disk around the metal through hole at the root of each resonator is 100μm, which is easy to process and manufacture. The spacing between resonators of each order is 308μm, 365μm, 375μm, 365μm, and 308μm, respectively, which are used to match electrical coupling and magnetic coupling.

[0028] Furthermore, the two dielectric substrates are bonded by gold balls with a diameter of 50 μm, and the positions are selected at the midpoints of the two peripheral metal through holes.

[0029] The present invention provides a double-layer stacked microstrip bandpass filter. A double-layer stacking method is adopted to place a number-order resonator on a lower glass substrate. An upper metal layer, a sidewall metallized through hole and a lower metal layer form a metal cavity structure, which significantly reduces the size of the filter. The number-order resonator adopts a step impedance resonator structure, which can effectively use the low-frequency end zero point generated by high-order mode electrical coupling, thereby obtaining better out-of-band suppression. A ceramic substrate or a glass substrate with a large dielectric constant is selected to significantly reduce the high-frequency loss of passive devices and improve the quality factor.

[0030] Finally, it should be noted that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. However, any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A double-layer stacked microstrip bandpass filter, characterized in that: It includes an upper metal layer, an upper substrate, an intermediate metal layer, a lower substrate and a lower metal layer arranged in sequence from top to bottom; A plurality of through holes are provided on the upper substrate, and the side walls of the through holes are metallized; The middle metal layer includes a first metal layer located on the lower surface of the upper substrate and a second metal layer located on the upper surface of the lower substrate, and the second metal layer on the upper surface of the lower substrate is provided with an input port and an output port; A plurality of through holes are arranged on the lower substrate, and the side walls of the through holes are metallized.

2. The double-layer stacked microstrip bandpass filter according to claim 1, characterized in that: The size of the upper metal layer, the size of the upper substrate, the size of the middle metal layer, the size of the lower substrate and the size of the lower metal layer all include the size in the first direction, the size in the second direction and the size in the third direction; In the first direction and the second direction, the upper metal layer and the upper substrate have the same size, and the lower substrate and the lower metal layer have the same size; In the first direction, the size of the lower substrate is larger than that of the upper substrate; In the second direction and the third direction, the size of the lower substrate is the same as the size of the upper substrate, and the size of the upper metal layer is the same as the size of the lower metal layer; The upper substrate and the lower substrate are connected by metal bonding. After the metal bonding, the upper substrate is located above the center of the lower substrate.

3. The double-layer stacked microstrip bandpass filter according to claim 2, characterized in that: The input port and the output port are arranged at the center position of the short side of the second metal layer in the second direction. Except for the positions of the input port and the output port of the second metal layer, no through holes are set. The periphery of the upper substrate, the periphery of the middle metal layer and the periphery of the lower substrate are all set with equidistant corresponding through holes in the first direction and the second direction.

4. The double-layer stacked microstrip bandpass filter according to claim 3, characterized in that: Bonding metal bodies of equal distance and same size are also arranged between the through holes of the first metal layer and the through holes of the second metal layer.

5. The double-layer stacked microstrip bandpass filter according to claim 3, characterized in that: The through holes at the periphery of the upper substrate, the periphery in the intermediate metal layer, and the periphery of the lower substrate are axisymmetric with respect to a straight line passing through the input port and the output port in a first direction.

6. The double-layer stacked microstrip bandpass filter according to claim 4, characterized in that: An input port, a plurality of order resonators, and an output port are arranged along a first direction within a range formed by the through hole of the second metal layer; The first metal layer is connected to the upper metal layer through a through hole with sidewall metallization, and is connected to the second metal layer through a bonding metal body; The second metal layer is connected to the lower metal layer through a through hole with sidewall metallization, and is connected to the first metal layer through a bonding metal body.

7. The double-layer stacked microstrip bandpass filter according to claim 6, characterized in that: The multi-order resonator is a step impedance resonator, and the bonding metal body is a bonding metal ball.

8. The double-layer stacked microstrip bandpass filter according to claim 1, characterized in that: The metals used in the upper metal layer, the middle metal layer and the lower metal layer are all the same.

9. The double-layer stacked microstrip bandpass filter according to claim 1, characterized in that: The upper substrate and the lower substrate are made of ceramic or glass.

10. The double-layer stacked microstrip bandpass filter according to claim 8, characterized in that: The metals used in the upper metal layer, the middle metal layer and the lower metal layer are all gold.

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