Miniaturized high-out-of-band rejection LTCC low-pass filter

Abstract

The utility model discloses a miniaturized LTCC low-pass filter with high out-of-band rejection, and the interior of a ceramic substrate is provided with an inner electrode, three inductors of an inductor layer and three parallel capacitors of a first capacitor layer form three resonators, and three transmission zero points are formed; the second capacitor layer and the third capacitor layer form a cross coupling capacitor, the third capacitor layer and the grounding layer form four grounding capacitors, and the three resonators are connected with one another and form a seven-order low-pass filter together with the four grounding capacitors; the bottom of the ceramic substrate is provided with an external electrode port, the external electrode port comprises two input / output ports and a grounding electrode port, the resonators are connected with the input / output ports, and the grounding capacitor is connected with a grounding point and the ports. According to the technical scheme, high suppression of multiple frequency multiplication is achieved, high-frequency warping points are suppressed, high-frequency stop-band suppression of the filter is improved, and the filter has the advantages of being small in size, low in loss, high in integration level, high in reliability and capable of being produced on a large scale.

Description

Technical Field

[0001] This utility model relates to the field of filter technology, and in particular to a miniaturized high out-of-band rejection LTCC low-pass filter. Background Technology

[0002] LTCC (Low Temperature Co-fired Ceramic) technology utilizes low-loss ceramic materials and employs metals such as silver and copper as embedded conductors. Its process includes multiple steps such as tape casting, drilling, printing, and lamination, allowing multiple passive components to be integrated into a multi-layer ceramic structure, achieving high integration and miniaturization. LTCC technology is widely used in fields such as electronic communications, automotive electronics, and aerospace, and its high reliability makes it suitable for manufacturing various electronic components.

[0003] Low-pass filters are an important passive device in the microwave field. They allow signals below a certain frequency to pass through, while greatly attenuating signals above that frequency.

[0004] Low-pass filters composed of multiple inductors and capacitors stacked in three dimensions using LTCC technology can fully utilize internal space, effectively reducing the size of passive components in RF systems, thus achieving high integration and miniaturization. Compared to other filters, LTCC low-pass filters achieve smaller size and insertion loss, but suffer from drawbacks such as embedded capacitors, low inductor quality factors, and poor rectangular coefficient and out-of-band rejection. LC low-pass filters designed with lumped parameters, due to the influence of internal parasitic parameters, exhibit waveform warping at higher frequencies, leading to decreased rejection, and may also exhibit anti-resonant warping points, causing a rapid deterioration in device performance. Utility Model Content

[0005] To address the aforementioned issues, this invention provides a miniaturized, high out-of-band rejection LTCC low-pass filter. It employs LTCC technology to achieve multi-layer stacking, constructs a resonator to create a transmission zero, and builds a seventh-order low-pass filter. Furthermore, it introduces capacitive cross-coupling to achieve high suppression of multiple harmonics, suppressing high-frequency warp points and improving the filter's high-frequency stopband rejection. This solves the problem of insufficient high-frequency suppression in existing LTCC low-pass filters. The filter features small size, low loss, high integration, high reliability, and mass production capability. It also uses bottom electrode packaging for easy mounting.

[0006] To achieve the above objectives, this utility model provides a miniaturized high out-of-band rejection LTCC low-pass filter, comprising: a ceramic substrate, an inner electrode, and an outer electrode port;

[0007] The internal electrode is disposed inside the ceramic substrate. The internal electrode includes an inductor layer, a first capacitor layer, a second capacitor layer, a third capacitor layer, and a ground layer. The three inductors of the inductor layer and the three parallel capacitors of the first capacitor layer constitute three resonators, forming three transmission zeros.

[0008] The second capacitor layer and the third capacitor layer form a cross-coupled capacitor, the third capacitor layer and the ground layer form four ground capacitors, the three resonators are interconnected, and together with the four ground capacitors, they form a seventh-order low-pass filter.

[0009] The outer electrode port is provided at the bottom of the ceramic substrate. The outer electrode port includes two input / output ports and one ground electrode port. The resonator is connected to the input / output ports, and the ground capacitor is connected to the ground electrode port.

[0010] In the above technical solution, preferably, the inductor layer is composed of three spiral inductors, and the spiral inductor is formed by two folded metal stubs connected through a through hole to form a three-dimensional spiral coil structure. The capacitors of the first capacitor layer, the second capacitor layer and the third capacitor layer all adopt the MIM structure and are composed of two layers of mutually insulated metal conductors. The grounding layer is composed of a large area of ​​metal conductor.

[0011] In the above technical solution, preferably, the inductor layer, the first capacitor layer, the second capacitor layer, the third capacitor layer and the ground layer are arranged in order from top to bottom in the ceramic substrate.

[0012] In the above technical solution, preferably, the three inductors in the inductor layer and the three capacitors in the first capacitor layer are positioned correspondingly, and the left and right sides of the corresponding inductors and capacitors are connected through metallized vias to form the resonator.

[0013] In the above technical solution, preferably, the metal conductor substrate of the second capacitor layer and the metal conductors of the two capacitors in the third capacitor layer constitute two mutually intersecting coupling capacitors.

[0014] In the above technical solution, preferably, of the four capacitors in the third capacitor layer, the two side capacitors are connected to the input / output port through metallized vias, the two middle capacitors are connected to the two ends of the resonator in the middle and on the corresponding side through metallized vias, and the four capacitors are also connected to the ground electrode port through metallized vias by the ground layer.

[0015] In the above technical solution, preferably, the two input / output ports are connected to the two ends of the three resonators through metallized vias.

[0016] In the above technical solution, preferably, the impedance of the input / output port is 50 ohms, and the two input / output ports are non-polarized.

[0017] Compared with the prior art, the beneficial effects of this utility model are as follows: it adopts LTCC process to realize multi-layer stacking, forms transmission zero by constructing resonators and constructs a seventh-order low-pass filter, and achieves high suppression of multiple harmonics by introducing capacitor cross-coupling, suppressing high-frequency warp points, improving the high-frequency stopband suppression of the filter, solving the problem of insufficient high-frequency band suppression in existing LTCC low-pass filters, and has the characteristics of small size, low loss, high integration, high reliability, and mass production capability, and adopts bottom electrode packaging, which is convenient for mounting. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of a miniaturized high out-of-band rejection LTCC low-pass filter disclosed in one embodiment of the present invention;

[0019] Figure 2 This is a schematic diagram of the S-parameter curves of a miniaturized high out-of-band rejection LTCC low-pass filter disclosed in one embodiment of the present invention.

[0020] Figure 3 This is a schematic diagram comparing the S11 curve of a miniaturized high out-of-band rejection LTCC low-pass filter disclosed in one embodiment of the present invention with the prior art.

[0021] Figure 4 This is a schematic diagram comparing the S21 curve of a miniaturized high out-of-band suppression LTCC low-pass filter disclosed in one embodiment of the present invention with the prior art. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0023] The present invention will now be described in further detail with reference to the accompanying drawings:

[0024] like Figure 1 As shown, a miniaturized high out-of-band rejection LTCC low-pass filter according to the present invention includes: a ceramic substrate, an inner electrode, and an outer electrode port;

[0025] An internal electrode is provided inside the ceramic substrate. The internal electrode includes an inductor layer, a first capacitor layer, a second capacitor layer, a third capacitor layer, and a ground layer. The three inductors in the inductor layer and the three parallel capacitors in the first capacitor layer constitute three resonators, forming three transmission zeros.

[0026] The second capacitor layer and the third capacitor layer form a cross-coupled capacitor. The third capacitor layer and the ground layer form four ground capacitors. The three resonators are interconnected and together with the four ground capacitors form a seventh-order low-pass filter.

[0027] An external electrode port is provided at the bottom of the ceramic substrate. The external electrode port includes two input / output ports and one ground electrode port. The resonator is connected to the input / output ports, and the ground capacitor is connected to the ground electrode port.

[0028] In this embodiment, LTCC technology is used to achieve multi-layer stacking. A transmission zero is formed by constructing a resonator and a seventh-order low-pass filter is constructed. High suppression of multiple harmonics is achieved by introducing capacitive cross-coupling, which suppresses high-frequency warp points and improves the high-frequency stopband suppression of the filter. This solves the problem of insufficient high-frequency suppression in existing LTCC low-pass filters. It features small size, low loss, high integration, high reliability, and mass production capability. Furthermore, it uses bottom electrode packaging for easy mounting.

[0029] In the above embodiment, preferably, the inductor layer is composed of three spiral inductors L1, L2, and L3. The spiral inductor is formed by two folded metal stubs connected through a through hole to form a three-dimensional spiral coil structure. The capacitors of the first capacitor layer, the second capacitor layer, and the third capacitor layer all adopt a MIM structure, which is composed of two layers of mutually insulated metal conductors. The grounding layer is composed of a large area of ​​metal conductor.

[0030] In the above embodiments, preferably, the inductor layer, the first capacitor layer, the second capacitor layer, the third capacitor layer and the ground layer are arranged in order from top to bottom in the ceramic substrate.

[0031] In the above embodiment, preferably, the positions of the three inductors in the inductor layer and the three capacitors in the first capacitor layer correspond to each other, and the left and right sides of the corresponding inductors and capacitors are connected through metallized vias to form a resonator.

[0032] In the above embodiment, preferably, the metal conductor substrate of the second capacitor layer and the metal conductors of the two capacitors in the third capacitor layer constitute two mutually intersecting coupling capacitors.

[0033] Specifically, the inductor layer includes a first inductor L1, a second inductor L2, and a third inductor L3; the first capacitor layer includes a first capacitor C1, a second capacitor C2, and a third capacitor C3; the second capacitor layer includes an eighth capacitor C8 and a ninth capacitor C9; the third capacitor layer includes a fourth capacitor C4, a fifth capacitor C5, a sixth capacitor C6, and a seventh capacitor C7; and the ground layer includes a ground metal GND.

[0034] L1 and C1 form the first resonator, creating the first transmission zero; L2 and C2 form the second resonator, creating the second transmission zero; L3 and C3 form the third resonator, creating the third transmission zero. C4, C5, C6, and C7 interact with GND to form four grounding capacitors. The metal electrodes of the second capacitor layer C8 and C9 and the metal electrodes of the third capacitor layer form cross-coupled capacitors. C4, C5, C6, and C7 are connected to the two ends of the first, second, and third resonators through metallized vias.

[0035] The LTCC low-pass filter is a bottom-electrode package, with external electrode ports P1, P2, and P3 all located at the bottom of the device.

[0036] In the above embodiment, preferably, of the four capacitors in the third capacitor layer, the two side capacitors are connected to the input / output ports through metallized vias, the two middle capacitors are connected to the two ends of the middle and corresponding side resonators through metallized vias, and the four capacitors are also connected to the ground electrode port through metallized vias by the ground layer.

[0037] Specifically, ground electrode C4 is connected to port P1 via a metallized via on one side, and to ground electrode P3 via a metallized via on the other side via the GND layer. Ground electrode C5 is connected to the first and second resonators via a metallized via on one side, and to ground electrode P3 via a metallized via the GND layer on the other side. Ground electrode C6 is connected to the second and third resonators via a metallized via on one side, and to ground electrode P3 via a metallized via the GND layer on the other side. Ground electrode C7 is connected to port P2 via a metallized via on one side, and to ground electrode P3 via a metallized via the GND layer on the other side.

[0038] In the above embodiment, preferably, the two input / output ports are connected to the two ends of the three resonators through metallized vias. Specifically, P1 is connected to L1, C1, and C4 through metallized vias, and P2 is connected to L3, C3, and C5 through metallized vias. The left side of the first resonator is connected to port P1, and the right side is connected to the second resonator. The right side of the second resonator is connected to the third resonator, and the right side of the third resonator is connected to port P2 through a metallized via.

[0039] In the above embodiment, preferably, the impedance of the input / output port is 50 ohms, and the two input / output ports are non-polarized and can be used as input / output ports respectively, that is, the input / output ports can be interchanged.

[0040] In practice, the miniaturized high out-of-band rejection LTCC low-pass filter proposed in this invention has a size of only 3.2mm × 1.6mm × 0.95mm, made from... Figure 2 It can be seen that the passband range is 0 to 1 GHz, the stopband range is 1.5 to 6 GHz, the passband loss is less than 0.8 dB, the in-band echo is greater than 25 dB, and the out-of-band rejection is greater than 30 dB.

[0041] Figure 3 , Figure 4 For comparison of the electrical performance of filters of the same size, the waveforms of the prior art filters are sourced from the manufacturer's website. It can be seen that within the passband, the return loss and insertion loss of this invention are similar to those of the prior art. Within the stopband, after 3.4 GHz, the out-of-band suppression of the prior art solution deteriorates significantly compared to the 1.5 GHz–3 GHz band, reaching less than 15 dB around 6 GHz, while this invention still maintains 30 dB stopband suppression at 6 GHz.

[0042] As can be seen from the above comparison, the miniaturized high out-of-band rejection LTCC low-pass filter of the present invention can solve the problem of insufficient high-frequency suppression in the existing LTCC low-pass filter. It has certain performance advantages compared with currently available devices and can better meet application requirements.

[0043] The above are merely preferred embodiments of this utility model and are not intended to limit the scope of this utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A miniaturized high out-of-band rejection LTCC low-pass filter, characterized in that The application relates to a ceramic filter, which comprises a ceramic base, an inner electrode and an outer electrode port. The inner electrode is arranged in the ceramic base and comprises an inductance layer, a first capacitance layer, a second capacitance layer, a third capacitance layer and a ground layer; three inductances of the inductance layer and three parallel capacitances of the first capacitance layer form three resonators, which form three transmission zeros. The second capacitance layer and the third capacitance layer form cross-coupling capacitances, the third capacitance layer and the ground layer form four ground capacitances, the three resonators are connected to each other and the four ground capacitances form a seven-order low-pass filter. The outer electrode port is arranged at the bottom of the ceramic base and comprises two input / output ports and a ground electrode port; the resonators are connected to the input / output ports and the ground capacitances are connected to the ground electrode port. The inductance layer is composed of three spiral inductances, the spiral inductances are connected by two folded metal short stubs through through holes to form a three-dimensional spiral coil structure, the capacitances of the first capacitance layer, the second capacitance layer and the third capacitance layer are all MIM structures composed of two layers of mutually insulated metal conductors, and the ground layer is composed of a whole large-area metal conductor.

2. The miniaturized high out-of-band rejection LTCC low-pass filter according to claim 1, characterized in that The inductance layer, the first capacitance layer, the second capacitance layer, the third capacitance layer and the ground layer are arranged in the ceramic base from top to bottom.

3. The miniaturized high out-of-band rejection LTCC low-pass filter according to claim 1, characterized in that The three inductances in the inductance layer and the three capacitances in the first capacitance layer correspond in position, and the inductances and the capacitances corresponding in position are connected through metallized through holes on the left and right sides to form the resonators.

4. The miniaturized high out-of-band rejection LTCC low-pass filter according to claim 1, characterized in that The metal conductor substrate of the second capacitance layer and the metal conductors of two capacitances in the third capacitance layer form two mutually intersecting coupling capacitances.

5. The miniaturized high out-of-band rejection LTCC low-pass filter according to claim 1, characterized in that Among the four capacitances of the third capacitance layer, the two side capacitances are connected to the input / output ports through metallized through holes, the two middle capacitances are connected to the two ends of the resonators on the middle and corresponding sides through metallized holes, and the four capacitances are connected to the ground electrode port through the ground layer and metallized through holes.

6. The miniaturized high out-of-band rejection LTCC low-pass filter according to claim 1, characterized in that The two input / output ports are connected to the two ends of the three resonators through metallized through holes.

7. The miniaturized high out-of-band rejection LTCC low-pass filter according to claim 1, characterized in that The impedance of the input / output port is 50 ohms, and the two input / output ports have no polarity.

8. The miniaturized high out-of-band rejection LTCC low-pass filter according to claim 1, characterized in that ​

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