High-rectangularity integrated crystal filter
By optimizing the crystal resonator electrode design and adding coupling electrodes, the integrated crystal filter volume and cost problems are solved, high rectangularity and miniaturization are achieved, circuits are simplified, suitable for large-scale production, and application effects are improved.
Patent Information
- Application Number
- CN202411296599.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-18
- Publication Date
- 2024-12-24
AI Technical Summary
When increasing the rectangularity, the integrated crystal filter usually needs to increase the number of crystal resonators, resulting in an increase in the device volume, limiting its application, and the prior art cannot effectively reduce costs and volume through circuit structure adjustment.
By optimizing the internal electrode graphic design of the crystal resonator, increasing the coupling electrode, enhancing the coupling between electrodes, reducing the number of integrated crystal resonators and capacitor components, achieving a high rectangularity without increasing the circuit order, and using an elliptical electrode to Reduce clutter introduction.
It realizes the miniaturization of devices, reduces costs, simplifies circuit complexity, reduces losses, is suitable for large-scale production, and improves application effect. The rectangular coefficient is reduced from 4.56 to 2.34, and the center frequency and bandwidth meet the design requirements.
Smart Images
Figure CN119182380A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of crystal filters, and in particular to an integrated crystal filter with high rectangularity. Background Art
[0002] Crystal filters have the characteristics of good frequency selectivity and high stopband suppression, and are key components to ensure high-quality transmission of various command signals and voice signals. Crystal filters can be divided into separate crystal filters and integrated crystal filters according to the circuit structure. Usually, the crystal resonator used in the integrated crystal filter integrates two pairs of electrodes on a single chip; under the premise of the same circuit order, the fewer the number of crystal resonators, the more conducive to the miniaturization of the device. However, the integrated crystal filter has a simple circuit structure and a small adjustable range of the external circuit, and it is impossible to improve the rectangularity by adjusting the circuit structure. In practical applications, in order to improve the rectangularity, it is necessary to increase the number of series-connected crystal resonators, that is, to increase the circuit order, which further increases the device volume and limits the practical application of integrated crystal filters. Summary of the invention
[0003] To solve the above problems, the present invention provides an integrated crystal filter with high rectangularity. By optimizing the internal electrode pattern design of the crystal resonator, it can achieve high rectangularity without increasing the circuit order, reduce costs, and be suitable for mass production.
[0004] The specific scheme includes: a base, an integrated crystal resonator unit and a shell; the integrated crystal resonator unit is arranged in the base, and the shell is buckled on the base and fixedly connected to the base;
[0005] The base is also provided with an input impedance conversion network, an output impedance conversion network and a ground terminal;
[0006] The integrated crystal resonator unit comprises a first broadband integrated crystal resonator, a second broadband integrated crystal resonator and a narrowband integrated crystal resonator; each integrated crystal resonator is provided with a first upper surface connection point, a second upper surface connection point and a common surface connection point;
[0007] The input impedance conversion network is connected to the first upper surface connection point of the first broadband integrated crystal resonator, the output impedance conversion network is connected to the second upper surface connection point of the second broadband integrated crystal resonator, a plurality of narrowband integrated crystal resonators are connected in series between the second upper surface connection point of the first broadband integrated crystal resonator and the first upper surface connection point of the second broadband integrated crystal resonator, and every two integrated crystal resonators are coupled through a capacitor; the common surface connection points of all integrated crystal resonators are connected to the ground terminal.
[0008] Beneficial effects of the present invention:
[0009] The device size and loss are reduced, and the cost is reduced. The traditional method to improve the rectangularity of the integrated crystal filter is to increase the number of integrated crystal resonators and increase the circuit order. This patent achieves the same rectangularity and can reduce the number of integrated crystal resonators and capacitor elements, which not only reduces the device size and loss, but also simplifies the circuit complexity, reduces the device cost, and is suitable for mass production. In this patent, elliptical electrodes are used for coupling, which can minimize the introduction of clutter, reduce the impact of parasitic parameters on the performance of the crystal filter, and improve the application effect compared to rectangular electrodes.
[0010] The present invention enhances the coupling between the original two pairs of electrodes by adding coupling electrodes. The crystal filter designed by the present invention achieves a center frequency of 63.8 MHz and a bandwidth of 50 kHz. It generates transmission zeros at 63.76 MHz and 63.96 MHz, and the rectangular coefficient is reduced from 4.56 to 2.34, achieving high rectangularity. BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Figure 1 This is a structural diagram of the integrated crystal resonator of the present invention;
[0012] Figure 2 This is a structural diagram of the integrated crystal filter of the present invention;
[0013] Figure 3 This is a structural diagram of a broadband integrated crystal resonator of the present invention;
[0014] Figure 4 It is a simulation diagram of the present invention;
[0015] Among them, 11 is a first upper electrode, 12 is a first lower electrode, 21 is a second upper electrode, 22 is a second lower electrode, 31 is a first elliptical electrode, and 32 is a second elliptical electrode. DETAILED DESCRIPTION
[0016] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0017] The integrated crystal filter is composed of several integrated crystal resonators cascaded together, and the integrated crystal resonators are coupled to each other through capacitance. Usually, the wafer of a single integrated crystal resonator is plated with two pairs of electrodes of a certain shape, which are called input electrodes and output electrodes. Figure 1For example, when an electrical signal of a certain frequency is added to the input electrode, the input electrode will generate a thickness vibration mode of the corresponding frequency under the action of the inverse piezoelectric effect. Because the frequency of the electrode-free area of the chip is higher than that of the electrode area, reflection will be generated at the boundary of the middle area between the two electrodes, and a standing wave of the thickness vibration mode will be formed in the electrode area. The thickness vibration mode of the electrode area cannot freely propagate through the middle area to the adjacent integrated crystal resonator, but can only decay exponentially in this area. These decaying vibration modes can be coupled to a limited extent between the two pairs of electrodes. Through this coupling, the thickness vibration mode will be transmitted to the output electrode in turn, and the mechanical vibration wave will be converted into an electrical signal output through the positive piezoelectric effect.
[0018] Based on the above principle, the propagation of mechanical vibration waves on the chip can be controlled according to actual requirements by reasonably designing the parameters of each integrated crystal resonator, thereby achieving the purpose of filtering. In order to reduce the number of circuit elements and realize device miniaturization, the present invention provides an integrated crystal filter with high rectangularity. By appropriately increasing the coupling electrode method, the transmission zero point of the crystal resonator is moved toward the center frequency, reducing the stopband bandwidth, thereby improving the rectangularity of the integrated crystal filter without increasing the circuit order.
[0019] The integrated crystal filter proposed in the present invention comprises a base, an integrated crystal resonant unit and a housing; the integrated crystal resonant unit is arranged in the base, and the housing is buckled on the base and fixedly connected to the base;
[0020] The base is also provided with an input impedance conversion network, an output impedance conversion network and a ground terminal;
[0021] The integrated crystal resonator unit comprises a first broadband integrated crystal resonator, a second broadband integrated crystal resonator and a narrowband integrated crystal resonator; each integrated crystal resonator is provided with a first upper surface connection point, a second upper surface connection point and a common surface connection point;
[0022] The input impedance conversion network is connected to the first upper surface connection point of the first broadband integrated crystal resonator, the output impedance conversion network is connected to the second upper surface connection point of the second broadband integrated crystal resonator, a plurality of narrowband integrated crystal resonators are connected in series between the second upper surface connection point of the first broadband integrated crystal resonator and the first upper surface connection point of the second broadband integrated crystal resonator, and every two integrated crystal resonators are coupled through capacitance; the common surface connection points of all integrated crystal resonators are connected to the ground; the input impedance conversion network and the output impedance conversion network are also connected to the ground.
[0023] Specifically, Figure 2As shown, the second upper surface connection point of the first broadband integrated crystal resonator is connected to the first upper surface connection point of the first narrowband integrated crystal resonator, and the connection forms the first coupling point; the second upper surface connection point of the first narrowband integrated crystal resonator is connected to the first upper surface connection point of the second narrowband integrated crystal resonator, and the connection forms the second coupling point; and so on, the second upper surface connection point of the N-1th narrowband integrated crystal resonator is connected to the first upper surface connection point of the Nth narrowband integrated crystal resonator, and the connection forms the Nth coupling point; the second upper surface connection point of the Nth narrowband integrated crystal resonator is connected to the first upper surface connection point of the second broadband integrated crystal resonator, and the connection forms the N+1th coupling point; each coupling point is connected in parallel with a capacitor between the ground terminal.
[0024] The number N of narrow-band integrated crystal resonators is ≥1, which is set according to actual requirements.
[0025] Specifically, the electrical performance parameters of the two width integrated crystal resonators (i.e., the first broadband integrated crystal resonator and the second broadband integrated crystal resonator) should be exactly the same, the center frequency of the narrowband integrated crystal resonator should be exactly the same as the center frequency of the broadband integrated crystal resonator, and the bandwidth of the narrowband integrated crystal resonator is usually about 0.8 times the bandwidth of the broadband integrated crystal resonator.
[0026] Preferably, if Figure 3 As shown, the first broadband integrated crystal resonator includes a chip, and a broadband resonant electrode unit arranged on the chip; the broadband resonant electrode unit includes a first rectangular metal electrode pair, an elliptical metal electrode pair, and a second rectangular metal electrode pair arranged in parallel from left to right; there are gaps between the elliptical metal electrode pair and the first rectangular metal electrode pair and the second rectangular metal electrode pair, and the gaps are equal in size; the second broadband integrated crystal resonator has the same structure as the first broadband integrated crystal resonator.
[0027] Preferably, the narrowband integrated crystal resonator comprises a wafer, and a narrowband resonant electrode unit arranged on the wafer; the narrowband resonant electrode unit comprises a first rectangular metal electrode pair and a second rectangular metal electrode pair arranged in parallel from left to right, such as Figure 1 shown.
[0028] Specifically, the first rectangular metal electrode pair includes a first upper electrode 11 and a first lower electrode 12; the first upper electrode 11 is located on the upper surface of the chip, the first lower electrode 12 is located on the lower surface of the chip, and the first upper electrode 11 and the first lower electrode 12 correspond in position; the second rectangular metal electrode pair includes a second upper electrode 21 and a second lower electrode 22; the second upper electrode 21 is located on the upper surface of the chip, the second lower electrode 22 is located on the lower surface of the chip, and the second upper electrode 21 and the second lower electrode 22 correspond in position; the first upper electrode 11, the first lower electrode 12, the second upper electrode 21 and the second lower electrode 22 have the same size.
[0029] Specifically, an electrode transmission line is vertically led out from the middle of the left side of the first upper electrode 11 to the left edge of the chip to form a first upper surface connection point, and an electrode transmission line is vertically led out from the middle of the right side of the second upper electrode 21 to the right edge of the chip to form a second upper surface connection point; an electrode transmission line is vertically led out from the middle of the lower side of the first lower electrode 12 and the second lower electrode 22 respectively, and these two electrode transmission lines are connected to form a common surface connection point.
[0030] Specifically, the elliptical metal electrode pair includes a first elliptical electrode 31 and a second elliptical electrode 32. The first elliptical electrode 31 is located on the upper surface of the chip, and the second elliptical electrode 32 is located on the lower surface of the chip. The first elliptical electrode 31 and the second elliptical electrode 32 correspond in position and have the same size.
[0031] Specifically, the first rectangular metal electrode pair and the second rectangular metal electrode pair have the same size, the length of the first rectangular metal electrode pair is C, and the long axis length of the elliptical electrode pair is 1 / 3C to 1 / 2C; the spacing between the first rectangular metal electrode pair and the second rectangular metal electrode pair is D, and the short axis length of the elliptical electrode pair is 1 / 4D to 1 / 3D.
[0032] In one embodiment, the main method for preparing the crystal filter includes:
[0033] According to the working filter of the crystal filter, the chip (quartz or other crystal material) is ground. The frequency of the chip itself after grinding is generally 1.05 to 1.08 times the working frequency of the crystal filter;
[0034] according to Figure 1 , Figure 3 Based on the electrode pattern design results, a special coating fixture is processed; the electrode is plated at the determined position of the wafer by vacuum coating;
[0035] The electrode thickness is adjusted by ion beam or chemical etching so that the frequency of the integrated crystal resonator meets the operating frequency range specified by the crystal filter. The integrated crystal resonator is packaged in a special housing.
[0036] According to the circuit structure, the integrated crystal resonators are cascaded and the peripheral circuit parameters are debugged; the integrated crystal filter packaging, marking and testing are completed.
[0037] The present invention enhances the coupling between the original two pairs of electrodes by adding coupling electrodes. Figure 1 ), a transmission zero appears outside the high-frequency component of the crystal filter. The equivalent circuit is as follows: Figure 2 shown.
[0038] Figure 4 The simulation curves of the actual designed filter are shown in Figure 2, (a) is before improvement, and (b) is after improvement. This method realizes the design of a crystal filter with a center frequency of 63.8MHz and a bandwidth of 50kHz. It generates transmission zeros at 63.76MHz and 63.96MHz, and the rectangular coefficient is reduced from 4.56 to 2.34, achieving a high rectangularity design.
[0039] In the present invention, unless otherwise clearly stipulated and limited, the terms such as "installation", "setting", "connection", "fixation" and "rotation" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium; it can be the internal connection of two elements or the interaction relationship between two elements. Unless otherwise clearly defined, ordinary technicians in this field can understand the specific meanings of the above terms in the present invention according to the specific circumstances.
[0040] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.
Claims
1. An integrated crystal filter with high rectangularity, characterized in that: It comprises a base, an integrated crystal resonator unit and a shell; the integrated crystal resonator unit is arranged in the base, and the shell is buckled on the base and fixedly connected to the base; The base is also provided with an input impedance conversion network, an output impedance conversion network and a ground terminal; The integrated crystal resonator unit comprises a first broadband integrated crystal resonator, a second broadband integrated crystal resonator and a narrowband integrated crystal resonator; each integrated crystal resonator is provided with a first upper surface connection point, a second upper surface connection point and a common surface connection point; The input impedance conversion network is connected to the first upper surface connection point of the first broadband integrated crystal resonator, the output impedance conversion network is connected to the second upper surface connection point of the second broadband integrated crystal resonator, a plurality of narrowband integrated crystal resonators are connected in series between the second upper surface connection point of the first broadband integrated crystal resonator and the first upper surface connection point of the second broadband integrated crystal resonator, and every two integrated crystal resonators are coupled through a capacitor; the common surface connection points of all integrated crystal resonators are connected to the ground terminal.
2. The high rectangular integrated crystal filter according to claim 1, characterized in that: The second upper surface connection point of the first broadband integrated crystal resonator is connected to the first upper surface connection point of the first narrowband integrated crystal resonator, and the connection forms the first coupling point; the second upper surface connection point of the first narrowband integrated crystal resonator is connected to the first upper surface connection point of the second narrowband integrated crystal resonator, and the connection forms the second coupling point; and so on, the second upper surface connection point of the N-1th narrowband integrated crystal resonator is connected to the first upper surface connection point of the Nth narrowband integrated crystal resonator, and the connection forms the Nth coupling point; the second upper surface connection point of the Nth narrowband integrated crystal resonator is connected to the first upper surface connection point of the second broadband integrated crystal resonator, and the connection forms the N+1th coupling point; each coupling point is connected in parallel with a capacitor between the ground terminal.
3. The high rectangular integrated crystal filter according to claim 1, characterized in that: The first broadband integrated crystal resonator includes a chip and a broadband resonant electrode unit arranged on the chip; the broadband resonant electrode unit includes a first rectangular metal electrode pair, an elliptical metal electrode pair and a second rectangular metal electrode pair arranged in parallel from left to right; a gap is left between the elliptical metal electrode pair and the first rectangular metal electrode pair and the second rectangular metal electrode pair; the second broadband integrated crystal resonator has the same structure as the first broadband integrated crystal resonator.
4. The high rectangular integrated crystal filter according to claim 1, characterized in that: The narrowband integrated crystal resonator comprises a wafer and a narrowband resonance electrode unit arranged on the wafer; the narrowband resonance electrode unit comprises a first rectangular metal electrode pair and a second rectangular metal electrode pair sequentially arranged in parallel from left to right.
5. The highly rectangular integrated crystal filter according to claim 3 or 4, characterized in that: The first rectangular metal electrode pair includes a first upper electrode and a first lower electrode; the first upper electrode is located on the upper surface of the chip, the first lower electrode is located on the lower surface of the chip, and the first upper electrode corresponds to the first lower electrode; the second rectangular metal electrode pair includes a second upper electrode and a second lower electrode; the second upper electrode is located on the upper surface of the chip, the second lower electrode is located on the lower surface of the chip, and the second upper electrode corresponds to the second lower electrode; the first upper electrode, the first lower electrode, the second upper electrode and the second lower electrode have the same size.
6. The highly rectangular integrated crystal filter according to claim 5, characterized in that: An electrode transmission line is led out from the middle of the left side of the first upper electrode to the left edge of the chip to form a first upper surface connection point, and an electrode transmission line is led out from the middle of the right side of the second upper electrode to the right edge of the chip to form a second upper surface connection point; an electrode transmission line is led out from the middle of the lower side of the first lower electrode and the second lower electrode respectively, and these two electrode transmission lines are connected to form a common surface connection point.
7. The high rectangular integrated crystal filter according to claim 3, characterized in that: The elliptical metal electrode pair includes a first elliptical electrode and a second elliptical electrode. The first elliptical electrode is located on the upper surface of the wafer, and the second elliptical electrode is located on the lower surface of the wafer. The first elliptical electrode corresponds to the second elliptical electrode in position and has the same size as the second elliptical electrode.
8. The high rectangular integrated crystal filter according to claim 3, characterized in that: The first rectangular metal electrode pair and the second rectangular metal electrode pair have the same size. The length of the first rectangular metal electrode pair is C, and the major axis length of the elliptical electrode pair is 1 / 3C to 1 / 2C. The spacing between the first rectangular metal electrode pair and the second rectangular metal electrode pair is D, and the minor axis length of the elliptical electrode pair is 1 / 4D to 1 / 3D.