A filter device and filter circuit
By introducing FBAR resonators in parallel at their resonant frequencies into the chip filter, a transmission zero is formed, which solves the problem of poor near-end suppression in the stopband of the chip filter and achieves better stopband suppression.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-08-11
- Publication Date
- 2026-04-14
AI Technical Summary
The poor near-end suppression of the stopband in chip filters limits their application.
An FBAR resonator is introduced into the chip filter, with the parallel resonant frequency at the near end of the stopband, forming a transmission zero. A T-type matching circuit is constructed through a matching inductor to improve the near-end suppression of the stopband.
The chip filter's stopband near-end suppression has been improved, enhancing its ability to suppress out-of-band interference signals.
Smart Images
Figure CN115412056B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of filter technology, and more particularly to a filter device and a filter circuit. Background Technology
[0002] Filters can effectively remove specific frequency components from a signal, or they can effectively remove other frequency components besides the specific frequency components. Stopband rejection ratio (PSRR) is an important indicator of a filter's performance. A higher PSRR indicates better suppression of out-of-band interference signals.
[0003] Chip filters, manufactured using chip technology, such as MMIC filters, MEMS filters, and silicon-based filters, are widely used in the field of communication technology. The structure of a chip filter determines its good far-end stopband suppression. However, the low Q value of chip filters results in poor near-end stopband suppression and slow roll-off, significantly limiting their applications. Summary of the Invention
[0004] This invention provides a filtering device to solve the problem of poor near-end suppression in the stopband of chip filters.
[0005] In a first aspect, embodiments of the present invention provide a filtering device, including a chip filter, a first FBAR resonator, a second FBAR resonator, a first matching inductor, a second matching inductor, and a third matching inductor; the chip filter, the first matching inductor, the first FBAR resonator, the second FBAR resonator, and the second matching inductor are connected in series sequentially; one end of the third matching inductor is connected between the first FBAR resonator and the second FBAR resonator, and the other end is grounded; a first end of the chip filter is an input end, and a second end is connected to the first matching inductor; the floating end of the second matching inductor is an output end; the parallel resonant frequency of the first FBAR resonator and the second FBAR resonator is within the frequency range near the stopband of the chip filter.
[0006] In one possible implementation, the frequency of the first FBAR resonator is the same as the parallel resonant frequency of the second FBAR resonator; the filtering device further includes a first frequency-modulated inductor; the first frequency-modulated inductor is connected in parallel with the second FBAR resonator, or the first frequency-modulated inductor is connected in parallel with the first FBAR resonator.
[0007] In one possible implementation, the parallel resonant frequency of the first FBAR resonator is different from the parallel resonant frequency of the second FBAR resonator.
[0008] In one possible implementation, the parallel resonant frequency of the first FBAR resonator and the second FBAR resonator is in the low-end frequency range near the stopband of the chip filter.
[0009] In one possible implementation, the parallel resonant frequency of the first FBAR resonator and the second FBAR resonator is in the high-end frequency range near the stopband of the chip filter.
[0010] In one possible implementation, when the first frequency-modulated inductor is connected in parallel with the second FBAR resonator, the parallel resonant frequency of the first FBAR resonator is in the low-end frequency range near the stopband of the chip filter, and the parallel resonant frequency of the second FBAR resonator is in the high-end frequency range near the stopband of the chip filter.
[0011] Alternatively, when the first frequency-modulated inductor is connected in parallel with the first FBAR resonator, the parallel resonant frequency of the second FBAR resonator is in the low-end frequency range near the stopband of the chip filter, and the parallel resonant frequency of the first FBAR resonator is in the high-end frequency range near the stopband of the chip filter.
[0012] In one possible implementation, the filtering device further includes a third FBAR resonator, a fourth FBAR resonator, a fourth matching inductor, a fifth matching inductor, and a sixth matching inductor; the fifth matching inductor, the fourth FBAR resonator, the third FBAR resonator, the fourth matching inductor, and the chip filter are connected in series in sequence; one end of the sixth matching inductor is connected between the third FBAR resonator and the fourth FBAR resonator, and the other end is grounded; the floating end of the fifth matching inductor is the input terminal; the first terminal of the chip filter is connected to the fourth matching inductor; the parallel resonant frequency of the third FBAR resonator and the fourth FBAR resonator is in the high-end frequency range near the stopband of the chip filter.
[0013] In one possible implementation, the parallel resonant frequency range of the first FBAR resonator and the second FBAR resonator is 997 MHz to 1001 MHz; the upper electrode area of the first FBAR resonator and the second FBAR resonator ranges from 54,600 square micrometers to 54,800 square micrometers; and the inductance of the first frequency-modulated inductor is 15 nanohenries.
[0014] In one possible implementation, the chip filter, the first matching inductor, the second matching inductor, and the third matching inductor are fabricated using gallium arsenide monolithic microwave integrated circuit chip technology; the first FBAR resonator and the second FBAR resonator are connected to the chip filter, the first matching inductor, the second matching inductor, and the third matching inductor using a ball-mounted flip-chip process.
[0015] Secondly, embodiments of the present invention provide a filtering circuit, including any of the filtering devices described above.
[0016] This invention provides a filtering device and a filtering circuit. The filtering device includes a chip filter, a first FBAR resonator, a second FBAR resonator, a first matching inductor, a second matching inductor, and a third matching inductor. The chip filter, the first matching inductor, the first FBAR resonator, the second FBAR resonator, and the second matching inductor are connected in series. One end of the third matching inductor is connected between the first FBAR resonator and the second FBAR resonator, and the other end is grounded. The first end of the chip filter is the input end, and the second end is connected to the first matching inductor. The floating end of the second matching inductor is the output end. The parallel resonant frequency of the first FBAR resonator and the second FBAR resonator is within the frequency range of the near-stopband of the chip filter. By setting a high-Q FBAR resonator, a transmission zero is generated near the stopband of the chip filter, forming a notch. The parallel resonant frequency of the FBAR resonators determines the transmission zero frequency, thereby improving the near-stopband suppression of the chip filter. Attached Figure Description
[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0018] Figure 1 This is a circuit structure diagram of a filtering device provided in an embodiment of the present invention;
[0019] Figure 2 This is an impedance characteristic curve of an FBAR resonator before and after connecting a parallel inductor, provided by an embodiment of the present invention.
[0020] Figure 3 This is a circuit diagram of a filter device with an increased frequency modulation inductor provided in an embodiment of the present invention;
[0021] Figure 4 A waveform diagram of the amplitude-frequency response of a chip filter provided in an embodiment of the present invention;
[0022] Figure 5 An amplitude-frequency response curve of a filter device provided in an embodiment of the present invention;
[0023] Figure 6 This is a circuit diagram of a filter device that simultaneously generates low-end and high-end transmission zeros, provided as an embodiment of the present invention. Detailed Implementation
[0024] To enable those skilled in the art to better understand this solution, the technical solutions in the embodiments of this solution will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this solution, not all of them. Based on the embodiments of this solution, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this solution.
[0025] The term "comprising" and any other variations thereof in the specification, claims, and accompanying drawings of this invention mean "including but not limited to," and are intended to cover a non-exclusive inclusion, not limited to the examples listed herein. Furthermore, the terms "first" and "second," etc., are used to distinguish different objects, not to describe a specific order.
[0026] The implementation of the present invention will be described in detail below with reference to the accompanying drawings:
[0027] Figure 1 This is a circuit structure diagram of a filtering device provided in an embodiment of the present invention. (Refer to...) Figure 1 This invention provides a filtering device, including a chip filter 100, a first FBAR resonator 201, a second FBAR resonator 202, a first matching inductor L1, a second matching inductor L2, and a third matching inductor L3; the chip filter 100, the first matching inductor L1, the first FBAR resonator 201, the second FBAR resonator 202, and the second matching inductor L2 are connected in series; one end of the third matching inductor L3 is connected between the first FBAR resonator 201 and the second FBAR resonator 202, and the other end is grounded; the first end of the chip filter 100 is the input end, and the second end is connected to the first matching inductor L1; the floating end of the second matching inductor L2 is the output end; the parallel resonant frequency of the first FBAR resonator 201 and the second FBAR resonator 202 is within the frequency range near the stopband of the chip filter 100.
[0028] FBAR resonators have parallel and series resonant frequencies. The impedance is highest at the parallel resonant frequency and lowest at the series resonant frequency. When an FBAR resonator is placed in a series branch, the signal cannot pass through at the parallel resonant frequency due to the highest impedance, creating a transmission zero and thus a notch frequency. The parallel resonant frequency of the FBAR resonator determines the frequency of the transmission zero, i.e., the notch frequency. FBAR resonators have the advantage of high Q values, typically reaching 1000-2000. A higher Q value results in a faster current drop at a given frequency offset, leading to a sharper notch curve and lower insertion loss. The frequency transition between the stopband and passband of the chip filter 100 is called the transition region; the near end of the stopband is the portion of the transition region close to the passband; the lower end of the near end of the stopband is the portion of the near end of the passband with a frequency lower than the passband frequency; and the higher end of the near end of the stopband is the portion of the near end of the passband with a frequency higher than the passband frequency.
[0029] The parallel resonant frequency of the FBAR resonator is within the frequency range of the near end of the stopband of the chip filter 100. That is, the FBAR resonator generates a transmission zero within the frequency range of the near end of the stopband of the chip filter 100, which improves the near end suppression of the stopband of the chip filter 100.
[0030] Adding an FBAR resonator to the port of chip filter 100 will affect the matching state of the port of chip filter 100; the first matching inductor L1, the second matching inductor L2 and the third matching inductor L3 form a T-type matching circuit, which is used to match the impedance of the port of chip filter 100 to 50Ω and eliminate the influence of the FBAR resonator on the matching impedance.
[0031] For example, the first end of the chip filter 100 is the input end, and the second end is connected to the first matching inductor L1; the first matching inductor L1, the first FBAR resonator 201, the second FBAR resonator 202, and the second matching inductor L2 are connected in series in sequence; one end of the second matching inductor L2 is connected to the second FBAR resonator 202; the other end of the second matching inductor L2 is a floating end, which serves as the output end of the filter device;
[0032] For example, the first end of the chip filter 100 is the output end, and the second end is connected to the first matching inductor L1; the first matching inductor L1, the first FBAR resonator 201, the second FBAR resonator 202, and the second matching inductor L2 are connected in series in sequence; one end of the second matching inductor L2 is connected to the second FBAR resonator 202; the other end of the second matching inductor L2 is a floating end, which serves as the input end of the filter device;
[0033] In an optional embodiment, the frequency of the first FBAR resonator 201 is the same as the parallel resonant frequency of the second FBAR resonator 202; the filtering device further includes a first frequency-modulated inductor 301; the first frequency-modulated inductor 301 is connected in parallel with the second FBAR resonator 202, or the first frequency-modulated inductor 301 is connected in parallel with the first FBAR resonator 201. For example, the first FBAR resonator 201 and the second FBAR resonator 202 are FBAR resonators of the same type.
[0034] Figure 2 The image shows the impedance characteristic curves of an FBAR resonator before and after connecting an inductor in parallel, as provided in an embodiment of the present invention. (Refer to...) Figure 2 The horizontal axis of the impedance characteristic curve represents frequency in GHz; the vertical axis represents impedance in dB; m3 is the series resonant frequency, at which the impedance of the FBAR resonator is minimum; m4 is the parallel resonant frequency, at which the impedance of the FBAR resonator is maximum.
[0035] The FBAR resonator provided in this embodiment of the invention has a series resonant frequency of 971.4 MHz and a parallel resonant frequency of 999.2 MHz. After connecting an inductor with a value of 15 nanohenries in parallel across the FBAR resonator, the series resonant frequency of the FBAR resonator remains unchanged, while the parallel resonant frequency increases from 999.2 MHz to 1025 MHz.
[0036] When an inductor is connected in parallel across an FBAR resonator, the parallel resonant frequency of the FBAR resonator increases, while the series resonant frequency remains unchanged. For example, after connecting the first frequency-modulating inductor 301 in parallel across the second FBAR resonator 202, the parallel resonant frequency of the second FBAR resonator 202 increases, thereby increasing the frequency at which the second FBAR resonator 202 generates a transmission zero. The difference between the parallel resonant frequencies of the first FBAR resonator 201 and the second FBAR resonator 202 increases, thus increasing the width of the notch generated by the two FBAR resonators. Changing the inductance value of the first frequency-modulating inductor 301 can adjust the frequency of the transmission zero and the width of the notch.
[0037] For example, the first frequency modulation inductor 301 is connected in parallel with the second FBAR resonator 202; one end of the first frequency modulation inductor 301 is connected to the input terminal of the second FBAR resonator 202, and the other end is connected to the output terminal of the second matching inductor L2; the output terminal of the second FBAR resonator 202 is connected to the input terminal of the second matching inductor L2.
[0038] For example, the first frequency modulation inductor 301 is connected in parallel with the second FBAR resonator 202; one end of the first frequency modulation inductor 301 is connected to the input terminal of the second FBAR resonator 202, and the other end is connected to the output terminal of the second FBAR resonator 202; the output terminal of the second FBAR resonator 202 is connected to the input terminal of the second matching inductor L2.
[0039] In an optional embodiment, the parallel resonant frequency of the first FBAR resonator 201 and the second FBAR resonator 202 is within the low-end frequency range of the near-stopband of the chip filter 100. The low-end of the near-stopband is the end with the lowest near-stopband frequency.
[0040] Figure 3 This is a circuit diagram of a filter device with an added frequency modulation inductor provided in an embodiment of the present invention. (Refer to...) Figure 3 :
[0041] In an optional embodiment, a filtering device includes a chip filter 100, a first FBAR resonator 201, a second FBAR resonator 202, a first matching inductor L1, a second matching inductor L2, a third matching inductor L3, and a first frequency modulation inductor 301; the chip filter 100, the first matching inductor L1, the first FBAR resonator 201, the second FBAR resonator 202, and the second matching inductor L2 are connected in series; one end of the third matching inductor L3 is connected between the first FBAR resonator 201 and the second FBAR resonator 202, and the other end is grounded; the first frequency modulation inductor 301 is connected in parallel with the second FBAR resonator 202; one end of the first frequency modulation inductor 301 is connected to the input terminal of the second FBAR resonator 202, and the other end is connected to the output terminal of the second matching inductor L2; the output terminal of the second FBAR resonator 202 is connected to the input terminal of the second matching inductor L2. The first terminal of the chip filter 100 is the input terminal, and the second terminal is connected to the first matching inductor L1; the floating end of the second matching inductor L2 is the output terminal. The frequency of the first FBAR resonator 201 is the same as the parallel resonant frequency of the second FBAR resonator 202; the parallel resonant frequency of the first FBAR resonator 201 and the second FBAR resonator 202 is within the frequency range near the stopband of the chip filter 100. For example, the first frequency modulation inductor 301 is connected in parallel with the first FBAR resonator 201; one end of the first frequency modulation inductor 301 is connected to the output terminal of the first FBAR resonator 201, and the other end is connected to the input terminal of the first matching inductor L1; the input terminal of the first FBAR resonator 201 is connected to the output terminal of the first matching inductor L1.
[0042] Figure 4 A frequency response curve of a chip filter 100 provided in an embodiment of the present invention. (Refer to...) Figure 4The horizontal axis represents frequency in GHz, and the vertical axis represents amplitude in dB. The solid curve is the amplitude-frequency response curve of the chip filter 100.
[0043] For example, in a filtering device provided by an embodiment of the present invention, the series resonant frequency of the first FBAR resonator 201 and the second FBAR resonator 202 is 971.4 MHz, and the parallel resonant frequency is 999.2 MHz; the inductance value of the first frequency modulation inductor 301 is 15 nanohenries; after the second FBAR resonator 202 is connected in parallel with the first frequency modulation inductor 301, the parallel resonant frequency increases from 999.2 MHz to 1025 MHz.
[0044] Figure 5 This is an amplitude-frequency response curve of a filter device provided in an embodiment of the present invention. (Refer to...) Figure 5 The horizontal axis represents frequency in GHz, and the vertical axis represents amplitude in dB. The solid curve represents the amplitude-frequency response curve of the filter device. The first FBAR resonator 201 and the second FBAR resonator 202 generate transmission zeros at the low end of the stopband near the chip filter 100; at the low-end frequency of 1102 MHz in the stopband, the amplitude of the filter device increases from 9.9 dB to 20 dB; the minimum insertion loss increases from 1.97 dB to 2.3 dB, with a relatively small increase in insertion loss.
[0045] In an optional embodiment, the parallel resonant frequency range of the first FBAR resonator 201 and the second FBAR resonator 202 is 997 MHz to 1001 MHz; the upper electrode area of the first FBAR resonator 201 and the second FBAR resonator 202 ranges from 54600 square micrometers to 54800 square micrometers; and the inductance of the first frequency-modulated inductor 301 is 15 nanohenries.
[0046] In an optional embodiment, the parallel resonant frequencies of the first FBAR resonator 201 and the second FBAR resonator 202 are in the high-end frequency range near the stopband of the chip filter 100.
[0047] In one optional embodiment, the parallel resonant frequency of the first FBAR resonator 201 is different from the parallel resonant frequency of the second FBAR resonator 202. For example, the parallel resonant frequencies of both the first FBAR resonator 201 and the second FBAR resonator 202 are in the low-end frequency range near the stopband; the different parallel resonant frequencies increase the width of the notch filter. Alternatively, the parallel resonant frequencies of both the first FBAR resonator 201 and the second FBAR resonator 202 are in the high-end frequency range near the stopband; the different parallel resonant frequencies increase the width of the notch filter.
[0048] In an optional embodiment, when the first frequency-modulated inductor 301 and the second FBAR resonator 202 are connected in parallel, the parallel resonant frequency of the first FBAR resonator 201 is in the low-end frequency range of the near-stopband of the chip filter 100; the parallel resonant frequency of the second FBAR resonator 202 is in the high-end frequency range of the near-stopband of the chip filter 100. The two FBAR resonators generate transmission zeros at the low and high ends, respectively, thereby improving the near-stopband suppression.
[0049] In an optional embodiment, when the first frequency modulation inductor 301 is connected in parallel with the first FBAR resonator 201, the parallel resonant frequency of the second FBAR resonator 202 is in the low-end frequency range of the near-end of the stopband of the chip filter 100, and the parallel resonant frequency of the first FBAR resonator 201 is in the high-end frequency range of the near-end of the stopband of the chip filter 100.
[0050] Figure 6 This is a circuit diagram of a filter device that simultaneously generates low-end and high-end transmission zeros, provided as an embodiment of the present invention. (Refer to...) Figure 6 :
[0051] In an optional embodiment, the filtering device further includes a third FBAR resonator 203, a fourth FBAR resonator 204, a fourth matching inductor L4, a fifth matching inductor L5, and a sixth matching inductor L6; the fifth matching inductor L5, the fourth FBAR resonator 204, the third FBAR resonator 203, the fourth matching inductor L4, and the chip filter 100 are connected in series; one end of the sixth matching inductor L6 is connected between the third FBAR resonator 203 and the fourth FBAR resonator 204, and the other end is grounded; the floating end of the fifth matching inductor L5 is the input terminal; the first terminal of the chip filter 100 is connected to the fourth matching inductor L4; the parallel resonant frequency of the third FBAR resonator 203 and the fourth FBAR resonator 204 is in the high-end frequency range near the stopband of the chip filter 100. The first FBAR resonator 201 and the second FBAR resonator 202 generate transmission zeros in the near-low end frequency range of the stopband of the chip filter, thereby improving the suppression of the near-low end of the stopband; the third FBAR resonator 203 and the fourth FBAR resonator 204 generate transmission zeros in the near-high end frequency range of the stopband, thereby improving the suppression of the near-high end of the stopband.
[0052] For example, the frequency of the third FBAR resonator 203 is the same as the parallel resonant frequency of the fourth FBAR resonator 204; the filtering device also includes a second frequency-modulated inductor; the second frequency-modulated inductor is connected in parallel with the fourth FBAR resonator 204. For example, the third FBAR resonator 203 and the fourth FBAR resonator 204 are FBAR resonators of the same type.
[0053] In an optional embodiment, the chip filter 100, the first matching inductor L1, the second matching inductor L2, and the third matching inductor L3 are fabricated using gallium arsenide monolithic microwave integrated circuit chip technology. The first FBAR resonator 201 and the second FBAR resonator 202 are connected to the chip filter 100, the first matching inductor L1, the second matching inductor L2, and the third matching inductor L3 using a flip-chip process. The chip filter 100, the first matching inductor L1, the second matching inductor L2, and the third matching inductor L3 are implemented using a monolithic microwave integrated circuit chip technology, with pre-reserved mounting positions for the FBAR resonators, which are then connected to the chip package using a flip-chip process.
[0054] For example, the first frequency modulation inductor 301 and the second frequency modulation inductor are implemented using a monolithic microwave integrated chip process.
[0055] In an optional embodiment, corresponding to any of the above-described filtering devices, the present invention also provides a filtering circuit, which includes any of the above-described filtering devices and has the advantages of the above-described filtering devices, which will not be described in detail here.
[0056] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A filtering device, characterized in that, It includes a chip filter, a first FBAR resonator, a second FBAR resonator, a first matching inductor, a second matching inductor, a third matching inductor, and a first frequency modulation inductor; The chip filter, the first matching inductor, the first FBAR resonator, the second FBAR resonator, and the second matching inductor are connected in series in sequence; one end of the third matching inductor is connected between the first FBAR resonator and the second FBAR resonator, and the other end is grounded; The first end of the chip filter is the input end, and the second end is connected to the first matching inductor; the floating end of the second matching inductor is the output end. The parallel resonant frequency of the first FBAR resonator and the second FBAR resonator is within the frequency range of the near end of the stopband of the chip filter. The first frequency-modulating inductor is connected in parallel with the first FBAR resonator or the second FBAR resonator, and the parallel resonant frequencies of the two FBAR resonators correspond to the low-end frequency range and the high-end frequency range of the near end of the stopband of the chip filter, respectively. When an inductor is connected in parallel across the two ends of the FBAR resonator, the parallel resonant frequency of the FBAR resonator increases while the series resonant frequency remains unchanged.
2. The filtering device as described in claim 1, characterized in that, The frequency of the first FBAR resonator is the same as the parallel resonant frequency of the second FBAR resonator. The first frequency-modulated inductor is connected in parallel with the second FBAR resonator, or the first frequency-modulated inductor is connected in parallel with the first FBAR resonator.
3. The filtering device as described in claim 1, characterized in that, The parallel resonant frequency of the first FBAR resonator is different from that of the second FBAR resonator.
4. The filtering device as described in claim 2, characterized in that, The parallel resonant frequency of the first FBAR resonator and the second FBAR resonator is in the low-end frequency range near the stopband of the chip filter.
5. The filtering device as described in claim 2, characterized in that, The parallel resonant frequency of the first FBAR resonator and the second FBAR resonator is in the high-end frequency range near the stopband of the chip filter.
6. The filtering device as described in claim 2, characterized in that, When the first frequency-modulated inductor and the second FBAR resonator are connected in parallel, the parallel resonant frequency of the first FBAR resonator is in the low-end frequency range near the stopband of the chip filter, and the parallel resonant frequency of the second FBAR resonator is in the high-end frequency range near the stopband of the chip filter; or, When the first frequency-modulated inductor is connected in parallel with the first FBAR resonator, the parallel resonant frequency of the second FBAR resonator is in the low-end frequency range near the stopband of the chip filter, and the parallel resonant frequency of the first FBAR resonator is in the high-end frequency range near the stopband of the chip filter.
7. The filtering device as described in claim 4, characterized in that, The filtering device further includes a third FBAR resonator, a fourth FBAR resonator, a fourth matching inductor, a fifth matching inductor, and a sixth matching inductor; The fifth matching inductor, the fourth FBAR resonator, the third FBAR resonator, the fourth matching inductor, and the chip filter are connected in series in sequence. One end of the sixth matching inductor is connected between the third FBAR resonator and the fourth FBAR resonator, and the other end is grounded; The floating end of the fifth matching inductor is the input terminal; the first terminal of the chip filter is connected to the fourth matching inductor. The parallel resonant frequencies of the third and fourth FBAR resonators are in the high-end frequency range near the stopband of the chip filter.
8. The filtering device as described in claim 4, characterized in that, The parallel resonant frequency range of the first FBAR resonator and the second FBAR resonator is 997 MHz to 1001 MHz. The upper electrode area of the first FBAR resonator and the second FBAR resonator ranges from 54,600 square micrometers to 54,800 square micrometers. The inductance of the first frequency modulation inductor is 15 nanohenries.
9. The filtering device according to any one of claims 1 to 8, characterized in that, The chip filter, the first matching inductor, the second matching inductor, and the third matching inductor are fabricated using gallium arsenide monolithic microwave integrated circuit chip technology. The first FBAR resonator and the second FBAR resonator are connected to the chip filter, the first matching inductor, the second matching inductor and the third matching inductor using a ball-mounted flip-chip process.
10. A filter circuit, characterized in that, Includes the filtering device as described in any one of claims 1 to 9.
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