Cavity filter and wireless communication equipment

Abstract

The utility model provides a cavity filter and wireless communication equipment, and relates to the technical field of communication. The cavity filter comprises: a resonant cavity forming a resonant cavity; the resonator is arranged in the resonant cavity; the circuit board is arranged on the outer surface of the resonant cavity, and an MEMS variable capacitor is arranged on the circuit board; the connecting piece is connected with the resonator and the circuit board; wherein the MEMS variable capacitor is electrically connected with the resonator through the connecting piece, and the cavity filter is configured to adjust the resonant frequency by controlling the capacitance value of the MEMS variable capacitor. According to the cavity filter, the circuit board provided with the MEMS variable capacitor is arranged on the resonant cavity, and the MEMS variable capacitor and the resonator are electrically connected through the connecting piece, so that the cavity filter can adjust the resonant frequency by controlling the capacitance value of the MEMS variable capacitor; therefore, the tuning function of the cavity filter can be realized by means of the circuit board through software control and the like, and an overlarge tuning structure does not need to be introduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of communication, in particular to a cavity filter and a wireless communication device. BACKGROUND

[0002] The filter is one of the important components in the communication system. With the development of information technology, the tunable function becomes an important function of the filter. The filter with the tunable function can change the resonant frequency, so as to realize the communication frequency band adjustment of the communication system.

[0003] The cavity filter is a filter based on the resonant cavity. The resonant cavity filter utilizes the resonance characteristics of the resonant cavity to realize the filtering of the specific frequency signal, has good anti-interference ability and high quality factor, and is widely used in wireless communication devices such as base stations, and can meet the requirements of high stability, large bandwidth, large power and other indicators of the wireless communication devices such as base stations. However, the tunable design of the related cavity filter is not ideal, and there are usually problems of inconvenient tuning or large tuning structure volume. UTILITY MODEL CONTENT

[0004] To solve the above technical problems, one technical solution adopted by the present application is to provide a cavity filter, which comprises: a resonant cavity body forming a resonant cavity; a resonator arranged in the resonant cavity; a circuit board arranged on the outer surface of the resonant cavity body, the circuit board being provided with a MEMS variable capacitor; and a connecting piece connecting the resonator and the circuit board; wherein the MEMS variable capacitor is electrically connected to the resonator through the connecting piece, and the cavity filter is configured to realize the adjustment of the resonant frequency by controlling the capacitance value of the MEMS variable capacitor.

[0005] In some embodiments, the cavity filter comprises a voltage controller arranged on the circuit board and connected to the pin of the MEMS variable capacitor, for controlling the voltage value of the pin to realize the control of the frequency range of the cavity filter.

[0006] In some embodiments, the cavity filter comprises a feedback device arranged on the circuit board and electrically connected to the MEMS variable capacitor, for collecting and feeding back the state information related to the temperature change of the MEMS variable capacitor.

[0007] In some embodiments, the MEMS variable capacitor comprises a variable capacitance module, and the variable capacitance module comprises at least one MEMS variable capacitance diode.

[0008] In some embodiments, the variable capacitance module includes a plurality of MEMS variable capacitors connected in parallel, the MEMS variable capacitor further includes a radio frequency signal access end and a voltage signal control end, the variable capacitance module is grounded and connected with the radio frequency signal access end to form a radio frequency link, and connected with the voltage signal control end to form a direct current link, and the MEMS variable capacitor is configured to adjust the capacitance value of the variable capacitance module by controlling the bias voltage through the voltage signal control end.

[0009] In some embodiments, the MEMS variable capacitor includes a power supply end, a voltage signal control end, a radio frequency signal access end, a plurality of capacitors and a radio frequency MEMS switch, the radio frequency MEMS switch includes a power supply port, a control port, an antenna port and a plurality of radio frequency ports, the power supply port is connected with the power supply end, the control port is connected with the voltage signal control end, the antenna port is connected with the radio frequency signal access end, and the plurality of radio frequency ports are respectively connected with the capacitors with different capacitance values.

[0010] The antenna port is connected with one of the plurality of radio frequency ports, and the radio frequency MEMS switch is configured to receive a control signal through the control port and adjust the connection state of the antenna port and the plurality of radio frequency ports based on the control signal to adjust the transmission path of the radio frequency signal.

[0011] In some embodiments, the resonant cavity includes a shell and a cover plate, the shell is provided with a mounting opening, the cover plate covers the mounting opening and forms a resonant cavity with the shell, the circuit board is arranged on the outer surface of the cover plate, the connecting piece penetrates the cover plate, and one end of the connecting piece is connected with the resonator and the other end is connected with the circuit board.

[0012] In some embodiments, the resonator has an inner cavity, and the resonator is separated from the cover plate, the cavity filter further includes a tuning rod, the tuning rod penetrates the cover plate and is inserted into the inner cavity, and the cavity filter is further configured to adjust the resonant frequency by controlling the insertion depth of the tuning rod in the inner cavity.

[0013] In some embodiments, the cavity filter includes a coupling rod and a plurality of cascaded resonant cavities, the coupling rod is arranged between each adjacent two resonant cavities for adjusting the bandwidth of the cavity filter; wherein the plurality of cascaded resonant cavities are integrally formed, the resonant cavities of each adjacent two resonant cavities are communicated, the coupling rod is inserted into the resonant cavities, and the cavity filter is configured to adjust the bandwidth by controlling the insertion depth of the coupling rod in the resonant cavities.

[0014] Another technical solution adopted by the present application is to provide a wireless communication device, the wireless communication device includes the cavity filter described above, and the cavity filter is used for frequency selection and control processing of communication signals of the wireless communication device to reduce signal interference.

[0015] Compared with the prior art, the cavity filter provided by the present application has the following beneficial effects:

[0016] The application sets the circuit board provided with the MEMS variable capacitor on the outer surface of the resonant cavity, and connects the circuit board and the resonator in the resonant cavity by the connecting piece to electrically connect the MEMS variable capacitor and the resonator, so that the cavity filter can adjust the resonant frequency by controlling the capacitance value of the MEMS variable capacitor, so that the cavity filter can realize the tuning function by the circuit board in the mode of software control, and does not need to introduce a too large tuning structure, which can facilitate the tuning and also avoid the too large size of the cavity filter. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0018] Figure 1 is a cross-sectional structure schematic diagram of the cavity filter provided by some embodiments of the present application;

[0019] Figure 2 is Figure 1 a single-cavity equivalent circuit schematic diagram of the cavity filter in the embodiment;

[0020] Figure 3 is Figure 1 an equivalent circuit schematic diagram of the cavity filter in the embodiment;

[0021] Figure 4 is a cross-sectional structure schematic diagram of the cavity filter provided by some embodiments of the present application;

[0022] Figure 5 is Figure 4 a single-cavity equivalent circuit schematic diagram of the cavity filter in the embodiment;

[0023] Figure 6 is Figure 4 an equivalent circuit schematic diagram of the cavity filter in the embodiment;

[0024] Figure 7 is Figure 4 a single-cavity frequency change schematic diagram of the cavity filter in the embodiment;

[0025] Figure 8 is Figure 4 a Q value change schematic diagram of the cavity filter in the embodiment;

[0026] Figure 9 is Figure 1 a simulation transmission response curve schematic diagram of the cavity filter in the embodiment;

[0027] Figure 10 is a schematic diagram of a profile structure of a cavity filter provided by some embodiments of the present application; Figure 4 is a simulated transmission response curve of a cavity filter in an embodiment;

[0028] Figure 11 is a schematic diagram of a profile structure of a cavity filter provided by some embodiments of the present application;

[0029] Figure 12 is a schematic diagram of a circuit structure of a MEMS variable capacitor provided by some embodiments of the present application;

[0030] Figure 13 is a schematic diagram of a circuit structure of a MEMS variable capacitor provided by some embodiments of the present application;

[0031] Figure 14 is a flowchart of a frequency control method of a cavity filter provided by some embodiments of the present application;

[0032] Figure 15 is a schematic diagram of a partial structure of a cavity filter provided by some embodiments of the present application;

[0033] Figure 16 is a schematic diagram of a performance test of a cavity filter provided by some embodiments of the present application;

[0034] Figure 17 is a schematic diagram of a performance test of a cavity filter provided by some embodiments of the present application;

[0035] Figure 18 is a schematic diagram of a structure of a cavity filter provided by some embodiments of the present application;

[0036] Figure 19 is a schematic diagram of a profile structure of a cavity filter provided by some embodiments of the present application; Figure 11 is a simulated reflection response S11 curve of a cavity filter in an embodiment;

[0037] Figure 20 is a schematic diagram of a profile structure of a cavity filter provided by some embodiments of the present application; Figure 11 is a simulated reflection response S22 curve of a cavity filter in an embodiment;

[0038] Figure 21 is a schematic diagram of a profile structure of a cavity filter provided by some embodiments of the present application; Figure 11 is a simulated transmission response S12 curve of a cavity filter in an embodiment;

[0039] Figure 22 is a schematic diagram of a structure of a wireless communication device provided by some embodiments of the present application;

[0040] Figure 23 is a schematic diagram of a structure of a wireless communication device provided by some embodiments of the present application;

[0041] Figure 24 is Figure 23 Band variation diagram of the wireless communication device in the embodiment;

[0042] Figure 25 is the application scenario diagram of the wireless communication device provided by some embodiments of the present application. DETAILED DESCRIPTION

[0043] In the following description, specific details are set forth, such as particular system architectures, techniques, etc., in order to provide a thorough understanding of the embodiments of the present application. However, persons having ordinary skill in the art will readily understand that the present application can be practiced without these specific details. In other instances, well-known structures, devices, circuits, and methods have not been described in detail in order to avoid obscuring the description of the present application.

[0044] In order to make the above objectives, characteristics and advantages of the present application more apparent and comprehensible, the specific embodiments of the present application are described in detail below with reference to the accompanying drawings. It can be understood that the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by persons having ordinary skill in the art without making any creative efforts fall within the scope of protection of the present application.

[0045] It should be understood that the terms "comprising" and "having" and any variations thereof used in the present application and the appended claims are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device including a series of steps or units is not limited to the listed steps or units, but optionally also includes steps or units not listed, or optionally also includes other steps or units inherent to the process, method, product or device.

[0046] The embodiments of the present application provide a cavity filter. Please refer to Figure 1 , Figure 1 is a cross-sectional structure diagram of the cavity filter provided by some embodiments of the present application.

[0047] In Figure 1 In the embodiments, the cavity filter 10 includes a resonant cavity 100, a resonator 200 and a tuning rod 300. The resonant cavity 100 forms a resonant cavity 101, which is an internal space of the resonant cavity 100. The resonator 200 is arranged in the resonant cavity 101. The tuning rod 300 is inserted into the surface of the resonant cavity 100 and extends into the resonant cavity 101.

[0048] The resonator 200 is an electronic component that can generate a resonant frequency. The resonator 200 can amplify or attenuate signals of a specific frequency. By designing the circuit parameters of the resonator 200, such as the capacitance and inductance parameters, the cavity filter 10 can have a strong response to signals within a certain frequency range and attenuate or suppress signals of other frequencies, achieving the effect of selective filtering.

[0049] The main function of the tuning rod 300 in the cavity filter 10 is to adjust the resonant frequency of the resonant cavity 101. The cavity filter 10 can change the inductance or capacitance value of the resonant cavity 101 by changing the length of the tuning rod 300 extending into the resonant cavity 101 or its relative position with other parts of the resonant cavity 101, thereby changing its resonant frequency.

[0050] Please refer to Figure 1 and Figure 2 , Figure 2 is Figure 1 a single-cavity equivalent circuit diagram of the cavity filter in the embodiment.

[0051] The resonant cavity 101 of the cavity filter 10 can be equivalent to an LC (inductance-capacitance) resonant circuit. In the resonant state, the electromagnetic field mode of the resonant cavity 101 is usually a TEM (Transverse Electromagnetic Wave) mode, in which the electric field and the magnetic field are completely perpendicular, and the electric field is mainly concentrated between the inner and outer conductors, while the magnetic field is around the outer periphery of the inner and outer conductors. Among them, the surface of the resonator 200 of the cavity filter 10 and the surface of the resonant cavity 100 can be equivalent to a capacitor.

[0052] In the equivalent circuit, the inner and outer conductors of the resonant cavity 101 can be regarded as an inductor L, and the medium (usually air) between the inner and outer conductors can be regarded as a capacitor C. When the resonant cavity 101 works at the resonant frequency, the resonant frequency of the inductor L and the capacitor C matches, so that the whole system reaches the resonant state. In this state, the electromagnetic energy of the resonant cavity 101 oscillates between the inductor and the capacitor without significant energy loss.

[0053] Please refer to Figure 3 , Figure 3 is Figure 1 a schematic diagram of the equivalent circuit of the cavity filter in the embodiment.

[0054] Among them, each capacitor (C1, C2, C3, C4, C5, C6) and each inductor (L1, L3, L5) as the main filter element forms a resonant network through a specific connection mode. Capacitors are used to store electric charge, while inductors are used to store magnetic field energy, and the combination of the two determines the frequency response characteristics of the filter.

[0055] In the resonant network, the values of the capacitor and the inductor are precisely selected to control the center frequency and bandwidth of the filter. When an input signal enters the cavity filter 10 through the input port Port1 (Port2 represents the output port), it encounters the resonant circuits composed of capacitors and inductors. These circuits resonate at a certain frequency, so that the signals at this frequency are amplified or selectively passed, while the signals at other frequencies are attenuated or blocked.

[0056] The cavity filter 10 can be composed of a plurality of resonant cavities 101 combined in different arrangements, each of which can be equivalent to a parallel inductor and capacitor. When a signal passes through the cavity filter 10, signals within the passband will pass through, and signals outside the passband will be suppressed, thereby achieving the effect of filtering.

[0057] In Figure 1 In an embodiment, the cavity filter 10 can change the resonant frequency of the resonant cavity 101 by adjusting the length of the tuning rod 300 extending into the resonant cavity 101. The tuning rod 300 can change the resonant frequency by changing the capacitance between the inner and outer conductors. Alternatively, the tuning rod 300 can be a coupling screw. The cavity filter 10 can change the length of the tuning rod 300 extending into the resonator 200 by rotating the tuning rod 300, thereby achieving the tuning function.

[0058] However, Figure 1 The tuning method of the cavity filter 10 shown is mechanical adjustment, which has the disadvantage of inconvenient control. Based on this, the present application also provides another cavity filter 10 to solve this problem.

[0059] Please refer to Figures 4 to 6 , Figure 4 is a cross-sectional structure diagram of the cavity filter provided by another embodiment of the present application, Figure 5 is Figure 4 is a single-cavity equivalent circuit diagram of the cavity filter in an embodiment, Figure 6 is Figure 4 is a schematic diagram of the equivalent circuit of the cavity filter in an embodiment.

[0060] On the basis of the cavity filter 10 shown, Figure 1 On the basis of the cavity filter 10 shown, Figure 4 The cavity filter 10 shown further includes a circuit board 400 and a connecting piece 500. The circuit board 400 is provided with a MEMS variable capacitor 410. The capacitance value of the MEMS variable capacitor 410 can be changed. Figure 5 The circuit diagram shown can be considered as being based on the circuit diagram shown in Figure 2 The circuit diagram shown can be considered as being based on the circuit diagram shown in Figure 6The circuit diagram shown can be considered as a basis for Figure 3 A plurality of adjustable capacitors are connected in parallel on the basis of the circuit diagram shown. The above has been described and will not be repeated here.

[0061] The MEMS variable capacitor 410 is electrically connected to the resonator 200 through the connecting piece 500. The cavity filter 10 is configured to achieve adjustment of the resonant frequency by controlling the capacitance value of the MEMS variable capacitor 410. Among them, the circuit board 400 can be arranged on the outer surface of the resonant cavity 100. The connecting piece 500 can connect the resonator 200 and the circuit board 400, and the MEMS variable capacitor 410 can be directly or indirectly connected with the connecting piece 500.

[0062] Among them, the circuit board 400 is a printed circuit board (PCB), which can provide mechanical support for fixing and assembling various electronic components such as integrated circuits, and realize wiring and electrical connection between these components. MEMS is the abbreviation of Micro ElectroMechanical Systems, i.e. micro-electro-mechanical system, and MEMS component is a high value-added component that integrates mechanical parts, electronic circuits, sensors, and actuators on a circuit board using microfabrication technology. The MEMS variable capacitor 410 can include a capacitor element with variable capacitance processed on the circuit board 400 using microfabrication technology.

[0063] It should be noted that the setting method of the MEMS variable capacitor 410 on the circuit board 400 is not limited to microfabrication, and other setting methods such as thin film deposition technology, using physical vapor deposition (PVD) or chemical vapor deposition (CVD), depositing one or more layers of metal thin film such as copper, gold or titanium on the circuit board 400 as the electrode of the capacitor; for example, photoetching and etching technology, using photoresist and mask plate to form the required pattern structure on the circuit board 400, through the steps of exposure and development, the pattern on the mask plate is transferred to the photoresist, and then wet etching or dry etching is used to remove the part of the circuit board 400 not protected by the photoresist, forming the required groove or hole structure, which can be used as the dielectric layer or the isolation layer between the electrodes of the capacitor; such as packaging and integration technology, packaging the prepared MEMS variable capacitor 410 with the circuit board 400, and integrating the MEMS variable capacitor 410 with other electronic components on the circuit board 400 to form a complete electronic system.

[0064] The formula of the resonant frequency of the cavity filter 10 is as follows:

[0065]

[0066] Among them, the size of the resonant frequency Fr is inversely proportional to the size of the capacitance value C. When the capacitance value C changes, the resonant frequency FR also changes.

[0067] The capacitance formula is as follows:

[0068] C = (εS) / (4πkd);

[0069] Where (ε) / (4πk) is a constant, S is the relative area of ​​the two electrodes of the capacitor, and d is the distance between the two electrodes of the capacitor. When S and d change, the capacitance C also changes, and thus the resonant frequency Fr also changes. When the resonant frequency of each single cavity of the cavity filter 10 shifts simultaneously, the cavity filter 10 as a whole will experience a frequency shift.

[0070] Please refer to the following: Figure 7 and Figure 8 , Figure 7 yes Figure 4 A schematic diagram of the single-cavity frequency variation of the cavity filter in the embodiment. Figure 8 yes Figure 4 A schematic diagram illustrating the Q-value variation of the cavity filter in the embodiment. (See diagram below.) Figure 7 As shown, the resonant frequency (vertical axis, unit Hz) of the cavity filter 10 decreases as the capacitance value (horizontal axis, unit pF) increases. Figure 7 and Figure 8 As shown, the Q value of cavity filter 10 ( Figure 8 The vertical axis and the resonant frequency show roughly the same trend, indicating that the tuning structure of the cavity filter 10 will not lead to an increase in insertion loss.

[0071] exist Figure 4 In this embodiment, the cavity filter 10 can adjust the resonant frequency by controlling the capacitance value of the MEMS variable capacitor 410. The cavity filter 10 can also adjust the resonant frequency by controlling the insertion length of the tuning rod 300 within the resonant cavity 101. In other words, the cavity filter 10 can include both mechanical and MEMS adjustment, possessing dual-tunable characteristics.

[0072] The frequency offset of the cavity filter 10 can be controlled by a combination of mechanical and MEMS adjustments. The cavity filter 10 can be optimized using a mechanical adjustment structure, followed by further adjustment using a MEMS structure. This reduces product complexity, lowers the manufacturing difficulty of the cavity filter 10, and improves production efficiency. In other embodiments, the cavity filter 10 may also be adjusted without mechanical adjustment, i.e., without the tuning lever 300, using only MEMS adjustment.

[0073] Please combine Figure 3 and Figure 6 See Figure 9 and Figure 10 , Figure 9 yes Figure 1Simulation transmission response curve of the cavity filter in the embodiment, Figure 10 is Figure 4 Simulation transmission response curve of the cavity filter in the embodiment. Figure 9 and Figure 10 Both show the simulation transmission response S11 curve and the simulation transmission response S21 curve, the S11 curve represents the reflection coefficient of the 1 port (port1) as shown in Figure 3 or Figure 6 S21 represents the transmission coefficient of the signal from the 1 port to the 2 port (port2). From the simulation waveform comparison of Figure 9 and Figure 10 It can be seen that, Figure 4 The cavity filter 10 of the embodiment is in Figure 1 After adding the adjustable capacitor to the cavity filter 10 of the embodiment, the frequency point of the cavity filter 10 is shifted from 351-355MHz to 346-350MHz.

[0074] Please refer to Figure 11 , Figure 11 is a cross-sectional structure schematic diagram of the cavity filter provided by some embodiments of the application.

[0075] In some embodiments, the resonant cavity 100 of the cavity filter 10 can include a shell 110 and a cover plate 120. The shell 110 is provided with a mounting port 102. The cover plate 120 covers the mounting port 102 and forms a resonant cavity 101 with the shell 110. The resonator 200 is arranged in the resonant cavity 101. The circuit board 400 provided with the MEMS variable capacitor 410 can be arranged on the outer surface of the cover plate 120. The circuit board 400 and the resonator 200 can be respectively located on the opposite sides of the cover plate 120. Among them, the shell 110 can be a groove, and the internal space thereof can be used to form the resonant cavity 101, and the slot of the shell 110 forms the mounting port 102. The cover plate 120 can be covered on the shell 110 and block the mounting port 102 to cooperate with the shell 110 to form a closed resonant cavity 101.

[0076] The resonator 200 and the MEMS variable capacitor 410 are electrically connected through the connecting piece 500, which is not limited to the contact or space coupling mode. The connecting piece 500 can be arranged through the cover plate 120, and one end of the connecting piece 500 is connected with the resonator 200 and the other end is connected with the circuit board 400. The connecting piece 500 can be a rod. Alternatively, the connecting piece 500 can be integrally formed with the resonator 200. In other embodiments, the connecting piece 500 can also be other structures, such as a lead. Among them, the connecting piece 500 can directly contact the MEMS variable capacitor 410 to realize the electrical connection between the MEMS variable capacitor 410 and the resonator 200. The connecting piece 500 can also be electrically connected through the circuit on the circuit board 400.

[0077] In this embodiment, the cavity filter 10 can adjust the resonant frequency by controlling the capacitance value of the MEMS variable capacitor 410. Thus, the cavity filter 10 can achieve tuning via software control and the circuit board 400, without the need for an excessively large tuning structure. This facilitates tuning while avoiding an overly large cavity filter 10. The MEMS variable capacitor 410 is a structure with an adjustable capacitance value; for example, it can be one or more MEMS components, or a module composed of multiple components and circuitry, depending on the specific requirements. The following illustrates the structure of the MEMS variable capacitor 410 provided in some embodiments of this application.

[0078] Please see Figure 12 , Figure 12 This is a schematic diagram of the circuit structure of the MEMS variable capacitor 410 provided in some embodiments of this application.

[0079] In some embodiments, the MEMS variable capacitor 410 includes a varactor module 411, which includes at least one MEMS varactor diode 412. The MEMS varactor diode 412 is a MEMS device whose junction capacitance can change with the applied voltage. The cavity filter 10 can adjust the junction capacitance of the MEMS varactor diode 412 by controlling the voltage, thereby adjusting the capacitance value of the varactor module 411.

[0080] Optionally, the varactor module 411 includes a plurality of MEMS varactor diodes 412 connected in parallel, the number of which is, for example, but not limited to, [number of diodes]. Figure 12 As shown in the diagram, when adjusting the capacitance value, the voltage provided by the voltage source is evenly distributed across multiple MEMS varactor diodes 412. As the bias voltage changes, the capacitance value of each MEMS varactor diode 412 also changes accordingly. These changes in capacitance value directly affect the total capacitance value of the entire parallel capacitor structure.

[0081] The MEMS variable capacitor 410 includes an RF signal input terminal RF-IN and a voltage signal control terminal VT-VBPF. The varactor module 411 is grounded and connected to the RF signal input terminal RF-IN to form an RF link, and connected to the voltage signal control terminal VT-VBPF to form a DC link. The MEMS variable capacitor 410 can be configured to adjust the capacitance value of the varactor module 411 by controlling the bias voltage through the voltage signal control terminal VT-VBPF. The RF signal input terminal RF-IN is connected to the resonator 200 via a connector 500.

[0082] Wherein, the radio frequency link is a radio frequency signal transmission link, and the direct current link is a control voltage link. In some embodiments, the MEMS variable capacitor 410 can further include a resistor or a capacitor electrically connected to the variable capacitance module 411 to realize functions such as direct current isolation and filtering.

[0083] As shown in FIG. 4, the MEMS variable capacitor 410 can further include a capacitor C1 and a capacitor C2 in parallel on the direct current link, and the capacitor C1 and the capacitor C2 are grounded and can be used to filter out direct current power supply noise. Figure 12

[0084] On the radio frequency link, the MEMS variable capacitor 410 can further include a resistor R2 and a capacitor C9, which can be connected in series and connected in series with the variable capacitance module 411. Wherein, the resistor R2 can be used as a reserved debugging structure. The capacitor C9 can be used for direct current isolation, that is, using the characteristic that the capacitor can block (or isolate) direct current (DC) in the circuit, only allowing alternating current (AC) to pass through, and preventing direct current from passing through. The direct current isolation function of the capacitor C9 can be used to extract the alternating current component in the radio frequency signal, filter out unnecessary components such as direct current bias, and thus obtain a purer signal.

[0085] Please refer to Figure 13 , Figure 13 is a circuit structure schematic diagram of the MEMS variable capacitor provided by some other embodiments of the present application.

[0086] In some embodiments, the MEMS variable capacitor 410 includes a radio frequency MEMS switch 413. As shown in FIG. 5, the radio frequency MEMS switch 413 includes a power supply port VDD, a control port (VC1, VC2), an antenna port ANT, and a plurality of radio frequency ports (RF1, RF2, RF3, RF4). The radio frequency MEMS switch 413 further includes a ground port (GND1, GND2). Figure 13

[0087] The MEMS variable capacitor 410 further includes a power supply end VT-SWITCH, a voltage signal control end (VT-VC1, VT-VC2), a radio frequency signal access end RF-IN, and a plurality of capacitors (C1, C2, C3, C4).

[0088] ​​The power port VDD is connected to the power terminal VT-SWITCH, which is used to provide the necessary voltage for the circuit. The control port (VC1, VC2) is connected to the voltage signal control terminal (VT-VC1, VT-VC2), specifically, the control port VC1 is connected to the voltage signal control terminal VT-VC1, and the control port VC2 is connected to the voltage signal control terminal VT-VC2, which is used to adjust the path of the radio frequency signal.

[0089] The antenna port ANT is connected to the radio frequency signal access end RF-IN. The plurality of radio frequency ports (RF1, RF2, RF3, RF4) are respectively connected to capacitors (C1, C2, C3, C4) with different capacitance values, specifically, the radio frequency port RF1 is connected to the capacitor C1, the radio frequency port RF2 is connected to the capacitor C2, the radio frequency port RF3 is connected to the capacitor C3, and the radio frequency port RF4 is connected to the capacitor C4. The capacitors C1, C2, C3, and C4 have different capacitance values. In other embodiments, the number of capacitors with different capacitance values can also be less than 4 or more than 4, and the radio frequency MEMS switch 413 has a corresponding number of radio frequency ports.

[0090] The antenna port ANT is connected to one of the plurality of radio frequency ports (RF1, RF2, RF3, RF4), and the radio frequency MEMS switch 413 is configured to receive a control signal through the control port (VC1, VC2) and adjust the connection state of the antenna port ANT and the plurality of radio frequency ports (RF1, RF2, RF3, RF4) based on the control signal, to achieve adjustment of the transmission path of the radio frequency signal.

[0091] Each radio frequency port (RF1, RF2, RF3, RF4) is connected to the antenna port ANT through a capacitor (C1, C2, C3, C4) with a different capacitance value, which is used to adjust the radio frequency performance of the filter. For example, when the control port VC2 voltage rises, the radio frequency MEMS switch 413 can connect the radio frequency port RF4 to the antenna port ANT, at which time the capacitor C4 acts as a matching element. For another example, when the control port VC1 voltage changes, the radio frequency MEMS switch 413 can switch to the radio frequency port RF3, using the capacitor C3 for matching.

[0092] When the control port VC1 or the control port VC2 receives a control signal and reaches a specific voltage, the radio frequency MEMS switch 413 will turn on the corresponding radio frequency port (RF1, RF2, RF3, RF4) to the antenna port ANT, while selecting the corresponding adjustment capacitor. The MEMS variable capacitor 410 can control the on-off of the radio frequency port RF4, the radio frequency port RF3, the radio frequency port RF2, and the radio frequency port RF1 through the power supply end VT-SWITCH, the voltage signal control end VT-VC1, and the voltage signal control end VT-VC2. This design allows the circuit to dynamically adjust the transmission path of the radio frequency signal according to the external control signal to meet different communication needs.

[0093] Optionally, the MEMS variable capacitor 410 further includes capacitors C5, C6, and C7 as shown in the figure. The capacitor C5 is connected in parallel with the power supply port VDD and grounded, the capacitor C6 is connected in parallel with the voltage signal control end VT-VC1 and grounded, and the capacitor C7 is connected in parallel with the voltage signal control end VT-VC2 and grounded, for filtering and matching of the radio frequency signal. The MEMS variable capacitor 410 can further include a capacitor C8 for DC isolation, which is connected in series with the antenna port ANT and the radio frequency signal access end RF-IN. The MEMS variable capacitor 410 can further include a resistor R3 connected in series with the antenna port ANT and the radio frequency signal access end RF-IN, which is used for matching of the antenna port ANT and can further ensure stable transmission of the radio frequency signal. Figure 13

[0094] The cavity filter 10 provided by the embodiments of the present application can conveniently adjust the resonant frequency by controlling the capacitance value of the MEMS variable capacitor 410. The capacitance value of the MEMS variable capacitor 410 can change according to the change of the control voltage. The cavity filter 10 can control the voltage through a software algorithm, and then control the capacitance value of the MEMS variable capacitor 410, so as to control the frequency range of the cavity filter 10.

[0095] Please refer to Figure 14 , Figure 14 is a flowchart of the frequency control method of the cavity filter provided by some embodiments of the present application.

[0096] In some embodiments, the frequency control method of the cavity filter 10 can include the following steps:

[0097] S1: Read the device frequency band configuration. The device can be a communication device to which the cavity filter 10 is applied. When the frequency band of the device changes, the cavity filter 10 can perform step S1.

[0098] S2: Load the mapping table. The mapping table can be pre-stored in the cavity filter 10.

[0099] ​S3: Analyzing the voltage value according to the mapping table and the device frequency band. The device adjustable frequency band is in one-to-one correspondence with the voltage value.

[0100] S4: Controlling the voltage. After determining the voltage value corresponding to the device frequency band according to the mapping table, the control voltage of the cavity filter 10 is controlled to control the capacitance value of the MEMS variable capacitor 410 to reach the preset value. In step S4, the cavity filter 10 can control the voltage through the voltage signal control end VT-VBPF as shown in Figure 12 , or control the voltage through the voltage signal control end VT-VC1 and the voltage signal control end VT-VC2 as shown in Figure 13 .

[0101] Please refer to Figure 15 , Figure 15 is a partial structure diagram of the cavity filter provided by some embodiments of the present application.

[0102] In some embodiments, the cavity filter 10 includes a voltage controller 420 for controlling the voltage to achieve control of the capacitance value of the MEMS variable capacitor 410. The voltage controller 420 can be arranged on the circuit board 400 and connected with the pin of the MEMS variable capacitor 410, which can be used to control the voltage value of the pin to achieve control of the frequency band range of the cavity filter 10. For example, the voltage controller 420 can be connected with the voltage signal control end VT-VBPF as shown in Figure 12 , or connected with the voltage signal control end VT-VC1 and the voltage signal control end VT-VC2 as shown in Figure 13 . Of course, the voltage controller 420 can also be arranged at other positions.

[0103] Wherein, the electronic element used by the voltage controller 420 can be selected according to actual conditions, for example but not limited to digital potentiometer, operational amplifier (Op-Amp), digital-to-analog converter (DAC), programmable voltage source, application specific integrated circuit (ASIC) and the like.

[0104] In the embodiments of the present application, the cavity filter 10 can use the software algorithm as shown in Figure 14 to control the voltage value of the corresponding pin of the MEMS variable capacitor 410 through the configuration of the voltage controller 420, thereby achieving the effect of controlling the adjustable filter frequency band range.

[0105] In some embodiments, the cavity filter 10 can include a feedback device 430 arranged on the circuit board 400 and electrically connected with the MEMS variable capacitor 410, which is used to collect and feedback the state information related to the temperature change of the MEMS variable capacitor 410.

[0106] It can be understood that the MEMS variable capacitor 410 and other components of the cavity filter 10 can have characteristic changes under high and low temperature environments.

[0107] For example, under a high temperature environment, the MEMS variable capacitor 410 can have characteristic changes such as a change in capacitance value, a decrease in insulation resistance, etc. The change in capacitance value is caused by the fact that the dielectric material inside the capacitor can expand due to heat under high temperature, thereby affecting the dielectric constant and causing a change in capacitance value. The decrease in insulation resistance is caused by the fact that the insulation resistance inside the capacitor can decrease due to an increase in electron activity as the temperature rises, thereby causing an increase in leakage current and affecting the stability and lifespan of the capacitor.

[0108] For another example, under a low temperature environment, the MEMS variable capacitor 410 can have characteristic changes such as a change in capacitance value, a change in leakage current, a change in inter-electrode resistance, internal loss, etc. The change in capacitance value is caused by the fact that the resistivity of metal can decrease under a low temperature environment, and the capacitance value of the capacitor is related to the resistivity, so the capacitance value can increase, and at the same time, the dielectric constant inside the capacitor can also increase as the temperature decreases, further causing a change in capacitance value. The change in leakage current is caused by the fact that the dielectric constant can increase due to low temperature, and the resistance of electrons flowing in the dielectric increases, thereby causing a decrease in leakage current. The change in inter-electrode resistance is caused by the fact that the metal conductor inside the capacitor can become more fragile due to low temperature, causing small pits and oxides to appear on the surface of the metal, which can cause the inter-electrode resistance of the capacitor to increase. The change in internal loss is caused by the fact that the flowability of molecules and ions inside the dielectric can decrease under a low temperature environment, and the internal loss caused by the movement and friction of molecules and ions due to the electric field can also decrease accordingly.

[0109] The feedback device 430 is an electronic element that can detect such characteristic changes and feed them back, such as but not limited to a capacitance-voltage converter (CVC), an insulation resistance tester, a leakage current monitor, a temperature sensor, an application-specific integrated circuit (ASIC) chip, etc., and the specific electronic element to be used can be determined according to the data to be fed back.

[0110] The embodiments of the present application can collect and feed back the state information related to the change in temperature of the MEMS variable capacitor 410 through the feedback device 430, and then the software algorithm can be automatically corrected according to the collected feedback data, thereby obtaining a more accurate frequency response, which is conducive to improving the frequency adjustment accuracy of the cavity filter 10 and making the product more intelligent. The feedback object of the feedback device 430 can be the voltage controller 420, or can be designed as other objects such as a background according to needs.

[0111] Please continue to refer to Figure 11In some embodiments, the resonator 200 can have an inner cavity 201. The cavity filter 10 can further include a tuning rod 300 which passes through the cover plate 120 and is inserted into the inner cavity 201. The cavity filter 10 can be further configured to achieve adjustment of the resonant frequency by controlling the insertion depth of the tuning rod 300 in the inner cavity 201.

[0112] The cavity filter 10 can change the length of the tuning rod 300 extending into the inner cavity 201 to change the capacitance value of the resonant cavity 101, and thus change the resonant frequency thereof. The resonator 200 can be spaced apart from the cover plate 120. The substance between the resonator 200 and the cover plate 120 can determine the dielectric constant ε in the capacitance formula C=(εS) / (4πkd). The substance between the resonator 200 and the cover plate 120 can be air, in which case the dielectric constant is equivalent to 1. In other embodiments, a dielectric plate can be provided between the resonator 200 and the cover plate 120, and the cavity filter 10 can select a dielectric plate of a corresponding material according to the required dielectric constant.

[0113] Embodiments of the present application can achieve control of the resonant frequency of the cavity filter 10 by controlling the MEMS adjustment mode of the MEMS variable capacitor 410 to adjust the capacitance value thereof, and the mechanical adjustment mode of adjusting the extension length of the tuning rod 300, so that the cavity filter 10 can be adjusted according to the required frequency during use.

[0114] Embodiments of the present application combine the structures of mechanical adjustment and MEMS adjustment, so that the cavity filter 10 can be changed within a certain frequency range, and the capacitance of 0-1 PF can be satisfied by adjusting the tuning rod 300, thereby reducing the types of capacitors, reducing the production difficulty, and helping to improve the production efficiency.

[0115] Please refer to Figure 16 and Figure 17 , Figure 16 is a performance test schematic diagram of a cavity filter provided by some embodiments of the present application, Figure 17 is a performance test schematic diagram of a cavity filter provided by some other embodiments of the present application.

[0116] Compared with the cavity filter 10 shown in Figure 16 , the cavity filter 10 shown in Figure 17 has a skirt around the periphery of one end of the resonator 200 close to the cover plate 120, which serves to reduce the frequency of the resonant cavity 101. A conventional filter needs to determine the shape of the resonator 200 during production and processing according to the required frequency, for example, the resonator 200 is processed into a structure without a skirt as shown in Figure 16 when the required frequency is higher, and the resonator 200 is processed into a structure with a skirt as shown in Figure 17The skirt structure makes the production and processing of the product more complex and the cost higher.

[0117] The embodiment of the present application can realize the control of the resonant frequency of the cavity filter 10 through the above-mentioned MEMS adjustment and mechanical adjustment, so it is not necessary to adjust the shape of the resonator 200 according to the required frequency during processing, which is beneficial to reduce the processing difficulty and reduce the manufacturing cost. For example, the embodiment of the present application can process the cavity filter 10 into the structure shown in the figure without skirt regardless of the required frequency, and it is not necessary to set the skirt for the resonator 200. Figure 16 From the frequency data and Q value data of the resonator 200 shown in the figure, it can be seen that the frequency and Q value of the two are basically the same, and it can be seen that the method of simplifying the structure of the resonator 200 of the embodiment of the present application will not cause the increase of the insertion loss. Figure 16 Figure 17 From the frequency data and Q value data of the resonator 200 shown in the figure, it can be seen that the frequency and Q value of the two are basically the same, and it can be seen that the method of simplifying the structure of the resonator 200 of the embodiment of the present application will not cause the increase of the insertion loss.

[0118] It should be noted that the above-mentioned embodiment shows a single cavity structure of the cavity filter 10, and the cavity filter 10 provided by the embodiment of the present application can include a plurality of resonant cavities 100. Please refer to Figure 18 , Figure 18 is a structural schematic diagram of the cavity filter provided by some embodiments of the present application.

[0119] In some embodiments, the cavity filter 10 can include a coupling rod 600 and a plurality of cascaded resonant cavities 100. The coupling rod 600 can be arranged between every two adjacent resonant cavities 100, for adjusting the bandwidth of the cavity filter 10. The coupling rod 600 is inserted into the resonant cavity 101, and the cavity filter 10 can be configured to realize the adjustment of the bandwidth by controlling the insertion depth of the coupling rod 600 in the resonant cavity 101.

[0120] In the process of adjusting the resonant frequency, the cavity filter 10 can change the coupling strength between the resonant cavities 101 by adjusting the position of the coupling rod 600, thereby affecting the bandwidth of the filter. The change of the coupling strength will change the energy exchange efficiency between the resonant cavities 101, thereby affecting the passband width of the cavity filter 10.

[0121] Among them, a plurality of cascaded resonant cavities 100 can be integrally formed. The resonant cavities 101 of every two adjacent resonant cavities 100 are communicated. The coupling rod 600 can be telescopically inserted between the two adjacent resonant cavities 100 to adjust the energy exchange efficiency between the two communicated resonant cavities 101, thereby realizing the adjustment of the bandwidth of the cavity filter 10. Alternatively, the coupling rod 600 can be a screw rod, and the adjustment of the insertion depth in the resonant cavity 101 is realized in a screw manner.

[0122] Please refer to Figures 19 to 21 , Figure 19 is​Figure 11 Simulation reflection response S11 curve of the cavity filter in the embodiment, Figure 20 is Figure 11 Simulation reflection response S22 curve of the cavity filter in the embodiment, Figure 21 is Figure 11 Simulation transmission response S12 curve of the cavity filter in the embodiment.

[0123] wherein, Figure 19 represents the reflection coefficient S11 of the 1-port of the cavity filter 10, Figure 20 represents the reflection coefficient S22 of the 2-port of the cavity filter 10, Figure 21 represents the transmission coefficient S12 of the cavity filter 10 from the 1-port to the 2-port. The abscissa corresponds to the frequency, in MHz.

[0124] wherein, Figures 19 to 21 all form 4 curves, respectively named as curve 1, curve 2, curve 3 and curve 4. The capacitance values corresponding to each curve are different. As shown in the figure, the capacitance value corresponding to curve 1 is 1pF, the capacitance value corresponding to curve 2 is 4pF, the capacitance value corresponding to curve 3 is 7pF, and the capacitance value corresponding to curve 4 is 10pF. The m value of each curve can represent the intermediate frequency and bandwidth.

[0125] Take curve 4 as an example, the intermediate frequency is the midpoint of m1 and m2, i.e. the intermediate value of 327MHz and 330MHz, which is 328.5MHz, and the bandwidth is the width of m1 and m2, which is 327MHz-330MHz. Similarly, the intermediate frequency of curve 3 is 353.875MHz, and the bandwidth is 352MHz-355.75MHz; the intermediate frequency of curve 2 is 385.5MHz, and the bandwidth is 383MHz-387MHz; the intermediate frequency of curve 1 is 422.5MHz, and the bandwidth is 419.75MHz-425.25MHz.

[0126] The embodiment of the present application can control the capacitance value through MEMS adjustment or mechanical adjustment, and then control the frequency of the cavity filter 10. From Figures 19 to 21 It can be seen that the frequency variation trend of the cavity filter 10 is gradually reduced with the increase of the capacitance value.

[0127] The cavity filter 10 provided by the embodiments of the present application has a frequency adjustable range of 240MHz, can realize filter normalization, and is beneficial to enrich product application scenarios. The cavity filter 10 provided by the embodiments of the present application has a transmission zero point, has the characteristics of low insertion loss, high suppression, large power, and miniaturization, and has strong practicability. In the case of loading a conventional coaxial cavity filter 10 to the size limit, the cavity filter 10 provided by the embodiments of the present application can achieve smaller product size and lighter weight on the basis of the original.

[0128] The embodiments of the present application also provide a wireless communication device. Please refer to Figure 22 , Figure 22 is a structural schematic diagram of a wireless communication device provided by some embodiments of the present application.

[0129] The wireless communication device 20 provided by the embodiments of the present application includes the cavity filter 10 described above. The cavity filter 10 can be used for frequency selection and control processing of communication signals of the wireless communication device 20, so as to reduce signal interference. The wireless communication device 20 is, for example but not limited to, a base station.

[0130] Please refer to Figure 23 and Figure 24 , Figure 23 is a structural schematic diagram of a wireless communication device provided by some embodiments of the present application, Figure 24 is Figure 23 a frequency band change schematic diagram of the wireless communication device in the embodiments.

[0131] In some embodiments, the wireless communication device 20 can include a signal transceiver 21, a power amplifier 22, and a duplexer 23. The signal transceiver 21 can be a TRX board, which is a full name of a transceiver board (Transceiver Board) and is one of the core components in a wireless communication system. The TRX board is responsible for mutual conversion between analog signals and radio frequency signals: in the transmission process, the analog signal processed by the baseband is converted into a radio frequency signal, so as to be sent out through an antenna; in the receiving process, the radio frequency signal received by the antenna is converted into an analog signal for further processing by the baseband processing system. The TRX board usually includes a radio frequency front-end processing circuit, such as a power amplifier 22, a low noise amplifier (LNA), a filter, and necessary control logic and interface circuit.

[0132] The power amplifier 22 can be a PA board, which is a full name of a power amplifier board (Power Amplifier Board), which is a circuit board 400 specially used for amplifying radio frequency signals. In a wireless communication system, the power amplifier 22 is one of the core components of the radio frequency front end, which functions to amplify the weak radio frequency signals in the transmission channel to a sufficient power level to ensure that the signals can cover a long distance and maintain high communication quality. The PA board usually contains multiple stages of amplification circuits, as well as necessary matching networks, protection circuits and control logic to ensure that the power amplifier 22 can work stably and efficiently.

[0133] The cavity filter 10 provided by the embodiments of the present application can be applied to the duplexer 23. The duplexer 23 (Duplexer) is a special bidirectional three-terminal filter used to isolate the transmission and reception signals to ensure that they can work normally at the same time without interfering with each other. The duplexer 23 is usually composed of two sets of band-stop filters with different frequencies, which uses the frequency division function of high-pass, low-pass or band-pass filters to make the same antenna or transmission line can be used for two signal paths. In the transmission state, the duplexer 23 allows the transmission signal to pass and transmit to the antenna, while preventing the reception signal from entering the transmission path; in the reception state, the duplexer 23 allows the reception signal to pass and transmit to the receiver, while preventing the transmission signal from entering the reception path. In this way, the duplexer 23 realizes effective isolation of the transmission and reception signals.

[0134] As shown in Figure 24 , the wireless communication device 20 provided by the embodiments of the present application can adjust the frequency of the duplexer 23 to realize the adjustment of the frequency band of the whole machine.

[0135] Taking the wireless communication device 20 as a base station as an example. When a certain base station and the center link fail, one of the transmission channels of the duplexer 23 can be frequency-shifted according to the pre-set plan, so that it can be interconnected with the adjacent base station, so as to realize the connection with the center by using the adjacent base station link.

[0136] Please refer to Figure 25 , Figure 25 is a schematic diagram of the application scenario of the wireless communication device provided by some embodiments of the present application.

[0137] In some embodiments, the wireless communication device 20 includes a transmission unit 24 and a reception unit 25, the transmission unit 24 is used for transmitting signals of a specific frequency band, and the reception unit 25 is used for receiving signals of a specific frequency band. The cavity filter 10 described above can be applied to the transmission unit 24 and the reception unit 25, so that the signal frequency band transmitted by the transmission unit 24 and the signal frequency band received by the reception unit 25 can be adjusted.

[0138] In this way, the wireless communication device 20 can change the object of its communication connection by adjusting the frequency band of its transmitted signal or the frequency band of its received signal when the communication connection with the outside is abnormal. In some application scenarios, the wireless communication device 20 transmits signals to the base station outside through the transmitting unit 24, and when the transmitting unit 24 cannot communicate with the base station successfully, the transmitting unit 24 can adjust the frequency band of its transmitted signal to communicate with other base stations, for example, to communicate with another base station adjacent to it. For example, when the transmitting unit 24 cannot communicate with the base station in the frequency band of 420-425 MHz, it can adjust the frequency band to 430-435 MHz to transmit signals to other base stations. Similarly, when the receiving unit 25 cannot communicate with the base station successfully, it can adjust the frequency band of its received signal to receive signals transmitted by other base stations.

[0139] The frequency band adjustment range of the cavity filter 10 can be designed according to the needs of the wireless communication device 20. For example, when the wireless communication device 20 can only support 5 MHz, the frequency band adjustment of the cavity filter 10 can be set to 5 MHz as the adjustment unit, and the cavity filter 10 can realize the adjustment of any 5 MHz frequency band in 350-470 MHz, which can reduce the dead stock. It can be understood that when the frequency band supported by the wireless communication device 20 is other values, the frequency band adjustment of the filter can also be changed accordingly.

[0140] The embodiment of the present application can form a plurality of frequency band combinations by the above design, so that the number of cavity filters 10 required by the wireless communication device 20 can be greatly reduced.

[0141] It should be understood that the terms used herein in the specification and the appended claims should not be construed as limiting the application unless otherwise explicitly intended by the inventor. As used in the specification and the appended claims, the singular forms "a," "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. As used in the description of the application, the terms "first," "second," and the like do not imply any relative importance or a specific order but are merely used to distinguish one feature from another. Thus, features limited by "first," "second" can explicitly or implicitly include one or more of the features. As used in the description of the application, the meaning of "a plurality of" is two or more, unless otherwise explicitly limited.

[0142] In the description of the application, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the application. In the description, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any suitable manner in any one or more embodiments or examples. In addition, the skilled person in the art can combine and combine the different embodiments or examples described in the specification and the features of the different embodiments or examples without contradiction.

[0143] The above is only some embodiments of the application, and does not limit the patent scope of the application, and any equivalent structure or equivalent process transformation using the content of the specification and drawings, or direct or indirect application in other related technical fields, are also included in the patent protection scope of the application.

Claims

1. A cavity filter, characterized by, The cavity filter comprises: a resonant cavity, forming a resonant cavity; a resonator, arranged in the resonant cavity; a circuit board, arranged on an outer surface of the resonant cavity, the circuit board being provided with a MEMS variable capacitor; a connecting piece, connecting the resonator and the circuit board; wherein the MEMS variable capacitor is electrically connected to the resonator through the connecting piece, and the cavity filter is configured to adjust the resonant frequency by controlling the capacitance value of the MEMS variable capacitor.

2. The cavity filter of claim 1, wherein, The cavity filter comprises a voltage controller, which is arranged on the circuit board and connected to a pin of the MEMS variable capacitor, for controlling the voltage value of the pin to control the frequency range of the cavity filter.

3. The cavity filter of claim 1, wherein, The cavity filter comprises a feedback device, which is arranged on the circuit board and electrically connected to the MEMS variable capacitor, for collecting and feeding back the state information of the MEMS variable capacitor related to temperature change.

4. The cavity filter of claim 1, wherein, The MEMS variable capacitor comprises a variable capacitance module, and the variable capacitance module comprises at least one MEMS variable capacitance diode.

5. The cavity filter of claim 4, wherein, The variable capacitance module comprises a plurality of parallel-connected MEMS variable capacitance diodes, and the MEMS variable capacitor further comprises a radio frequency signal access end and a voltage signal control end, the variable capacitance module is grounded and connected to the radio frequency signal access end to form a radio frequency link, and connected to the voltage signal control end to form a direct current link, and the MEMS variable capacitor is configured to control the bias voltage through the voltage signal control end to adjust the capacitance value of the variable capacitance module.

6. The cavity filter of claim 1, wherein, The MEMS variable capacitor comprises a power supply end, a voltage signal control end, a radio frequency signal access end, a plurality of capacitors and a radio frequency MEMS switch, the radio frequency MEMS switch comprises a power supply port, a control port, an antenna port and a plurality of radio frequency ports, the power supply port is connected to the power supply end, the control port is connected to the voltage signal control end, the antenna port is connected to the radio frequency signal access end, and a plurality of the radio frequency ports are respectively connected to the capacitors with different capacitance values; wherein the antenna port is connected to one of the plurality of radio frequency ports, and the radio frequency MEMS switch is configured to receive a control signal through the control port and adjust the connection state of the antenna port and the plurality of radio frequency ports based on the control signal, to adjust the transmission path of the radio frequency signal.

7. The cavity filter of claim 1, wherein, The resonant cavity comprises a shell and a cover plate, the shell is provided with a mounting port, the cover plate covers the mounting port and forms the resonant cavity together with the shell, the circuit board is arranged on an outer surface of the cover plate, the connecting piece penetrates the cover plate, and one end of the connecting piece is connected to the resonator and the other end is connected to the circuit board.

8. The cavity filter of claim 7, wherein, The resonator has an inner cavity, and the resonator is separated from the cover plate, the cavity filter further comprises a tuning rod, the tuning rod penetrates the cover plate and is inserted into the inner cavity, and the cavity filter is further configured to adjust the resonant frequency by controlling the insertion depth of the tuning rod in the inner cavity.

9. The cavity filter of claim 1, wherein, The cavity filter comprises a coupling rod and a plurality of cascaded resonant cavities, the coupling rod is arranged between every two adjacent resonant cavities for adjusting the bandwidth of the cavity filter; wherein the plurality of cascaded resonant cavities are integrally formed, the resonant cavities of every two adjacent resonant cavities are communicated, the coupling rod is inserted into the resonant cavities, and the cavity filter is configured to realize the adjustment of the bandwidth by controlling the insertion depth of the coupling rod in the resonant cavities.

10. A wireless communication device, comprising: The wireless communication device comprises the cavity filter according to any one of claims 1-9, and the cavity filter is used for frequency selection and control processing of communication signals of the wireless communication device to reduce signal interference.

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