Reconfigurable filter and design method

Abstract

The invention discloses a reconfigurable filter and a design method, relates to the technical field of radio frequency filter chips, and solves the problems that a tuned filter in the prior art cannot realize continuous adjustability, and is large in area and size and high in design complexity. The method comprises the following steps: determining an initial circuit of a quasi-elliptical filter network comprising a first LC structure and a second LC structure which are connected in series; calculating a first capacitance range of a variable capacitor in the first variable capacitor module according to a low-pass filtering network in the initial circuit; calculating parameters of each component in the low-pass filter network equivalent to the high-pass filter network through a frequency conversion method; calculating a second capacitance range of a variable capacitor in a second variable capacitor module according to the high-pass filtering network; optimizing the initial circuit of the reconfigurable filter according to the first capacitance range and the second capacitance range to obtain a reconfigurable filter circuit; the effect of adjusting the upper limit and the lower limit of the frequency by adjusting the voltage is achieved, and the circuit complexity is low.

Description

Technical Field

[0001] The present invention relates to the technical field of radio frequency filter chips, and in particular to a reconfigurable filter and a design method. Background Art

[0002] Continuously tunable bandpass filters (CTBF) play a vital role in wireless communications, radar systems, audio processing, and many other electronic applications. These filters can adjust their center frequency and bandwidth as needed to adapt to dynamically changing signal processing requirements. Traditional tunable filter design methods mainly include three types: mechanical tuning, electronic tuning, and digital tuning.

[0003] Mechanically tuned filters, such as filters tuned by variable capacitance diodes, can achieve continuous frequency adjustment, but their tuning speed is slow and they are easily affected by temperature and mechanical vibration, resulting in unstable performance; electronically tuned filters, such as filters based on voltage-controlled oscillators (VCOs), have fast tuning speeds, but they usually have problems with poor linearity and limited tuning range. In addition, these filters have high power consumption, and their size and complexity also become design challenges in high-frequency applications; digitally tuned filters, such as filters based on digital signal processors (DSPs), provide high precision and flexibility, but they usually require complex digital signal processing algorithms and may have processing delays in real-time applications.

[0004] Although the above technologies have achieved certain success in specific applications, they still have limitations in tuning speed, linearity, power consumption, size and cost. In particular, in high-frequency, broadband and high dynamic range application scenarios, existing technologies are difficult to meet the growing performance requirements. While the existing technologies pursue high performance, existing filters are often accompanied by high insertion loss and large size, which is particularly prominent in portable devices and space-constrained applications; complex tuning mechanisms and high-precision components increase the manufacturing cost of the filter, while reducing its manufacturability and reliability; in an environment with temperature changes, the performance of the filter may be affected, resulting in a decrease in signal processing quality. Summary of the invention

[0005] The present invention solves the problems in the prior art that the tunable filter cannot be continuously adjustable, has a large area and size, and has a high design complexity by providing a reconfigurable filter and a design method. The present invention realizes the function of adjusting the upper and lower limits of the frequency by adjusting the voltage, and has low circuit complexity.

[0006] In a first aspect, the present invention provides a method for designing a reconfigurable filter, the method comprising:

[0007] determining an initial circuit of a quasi-elliptical filter network including a first LC structure and a second LC structure connected in series;

[0008] Calculating a first capacitance range of a variable capacitor in a first variable capacitance module in the initial circuit according to a low-pass filter network in the initial circuit;

[0009] Calculate the parameters of each component in the high-pass filter network in the initial circuit which is equivalent to the low-pass filter network by means of frequency conversion;

[0010] Calculating a second capacitance range of a variable capacitor in a second variable capacitance module in the initial circuit according to the high-pass filter network;

[0011] The initial circuit of the reconfigurable filter is optimized according to the first capacitance range and the second capacitance range to obtain a reconfigurable filter circuit.

[0012] In combination with the first aspect, in a possible implementation manner, calculating a first capacitance range of a variable capacitor in a first variable capacitance module in the initial circuit according to a low-pass filter network in the initial circuit includes:

[0013] The first capacitance range is calculated based on the first balance condition and the parameters of each component in the low-pass filter network; wherein the first balance condition includes: determining that the DC component in the low-pass filter network and the radio frequency signal in the low-pass filter network will not crosstalk in the main path of the low-pass filter network.

[0014] In combination with the first aspect, in a possible implementation manner, the method of calculating the parameters of each component in the high-pass filter network in the initial circuit that is equivalent to the low-pass filter network by a frequency conversion method includes:

[0015] According to the actual admittance of the low-pass filter network and the actual source impedance of the low-pass filter network, the impedance conversion factor γ is calculated. 0 ;

[0016] According to the impedance conversion factor γ 0 The parameters of each component in the high-pass filter network are calculated based on the parameters of each component in the low-pass filter network, and the low-pass filter network is equivalent to the high-pass filter network.

[0017] In combination with the first aspect, in a possible implementation manner, optimizing the initial circuit of the reconfigurable filter according to the first capacitance range and the second capacitance range to obtain the reconfigurable filter circuit includes:

[0018] According to the first capacitance range and the second capacitance range, respectively determining a first frequency band range of a low-frequency filter frequency band, a second frequency band range of a high-frequency filter frequency band, and a third frequency band range of a wide frequency band in the initial circuit;

[0019] The parameters of the low-pass filter network, the high-pass filter network, the first variable capacitance module and the second variable capacitance module are optimized according to the first frequency band range, the second frequency band range and the third frequency band range to obtain a reconfigurable filter circuit.

[0020] In a second aspect, the present invention provides a reconfigurable filter, the filter comprising: a low-pass filter network, a high-pass filter network, a first variable capacitance module and a second variable capacitance module; the low-pass filter network is connected to the first variable capacitance module;

[0021] The low-pass filter network is connected to the high-pass filter network;

[0022] The high-pass filter network is connected to the second variable capacitance module;

[0023] The low-pass filter network and the high-pass filter network are both connected to a standard impedance.

[0024] In combination with the second aspect, in a possible implementation, the low-pass filter network includes: an LC module and a microstrip line TL2, wherein the LC module includes: a first LC structure and a second LC structure connected in series;

[0025] The first LC structure includes a microstrip line TL1, an inductor L1 and a capacitor C1 connected in series in sequence;

[0026] The second LC structure includes a microstrip line TL3, an inductor L2 and a capacitor C2 connected in series in sequence;

[0027] The microstrip line TL2 is connected in series with the microstrip line TL1 and the microstrip line TL3.

[0028] In combination with the second aspect, in a possible implementation manner, the values ​​of the electrical components in the first LC structure and the second LC structure are the same.

[0029] In combination with the second aspect, in a possible implementation, the first variable capacitance module includes: a capacitor C3, an inductor L3, a DC power supply DC1, a switch device F1, a capacitor C4, an inductor L4 and a DC power supply DC2;

[0030] The first end of the capacitor C3 is connected to the low-pass filter network, and the second end of the capacitor C3 is connected to the first end of the inductor L3 and the gate of the switch device F1;

[0031] The second end of the inductor L3 is connected to the first end of the DC power supply DC1; the second end of the DC power supply DC1 is grounded;

[0032] The source and drain of the switch device F1 are connected to the first end of the inductor L4 and the first end of the capacitor C4;

[0033] The second end of the capacitor C4 is connected to the low-pass filter network;

[0034] The second end of the inductor L4 is connected to the first end of the DC power supply DC2;

[0035] A second terminal of the DC power supply DC2 is grounded.

[0036] In combination with the second aspect, in a possible implementation, the high-pass filter network includes: a capacitor C5, a capacitor C6, a microstrip line TL4, a microstrip line TL5, and a microstrip line TL6;

[0037] The first end of the capacitor C5 is connected to the low-pass filter network, and the second end of the capacitor C5 is connected to the first end of the capacitor C6;

[0038] The second end of the capacitor C6 is connected to the first end of the microstrip line TL6;

[0039] The second end of the microstrip line TL6 is grounded;

[0040] The first end of the microstrip line TL5 is connected to the second end of the capacitor C5, and the second end of the microstrip line TL5 is grounded;

[0041] A first end of the microstrip line TL4 is connected to a first end of the capacitor C5 , and a second end of the microstrip line TL4 is grounded.

[0042] In combination with the second aspect, in a possible implementation, the second variable capacitance module includes: a capacitor C7, an inductor L6, a DC power supply DC3, a switch device F2, a capacitor C8, an inductor L5 and a DC power supply DC4;

[0043] The first end of the capacitor C7 is connected to the high-pass filter network, and the second end of the capacitor C7 is connected to the first end of the inductor L5 and the gate of the second switch device F2;

[0044] The second end of the inductor L5 is connected to the first end of the DC power supply DC3;

[0045] The second end of the DC power supply DC3 is grounded;

[0046] The source and drain of the switch device F2 are connected to the first end of the inductor L6 and the first end of the capacitor C8;

[0047] The second end of the capacitor C8 is grounded;

[0048] The second end of the inductor L6 is connected to the first end of the DC power supply DC4;

[0049] A second terminal of the DC power supply DC4 is grounded.

[0050] One or more technical solutions provided in the present invention have at least the following technical effects or advantages:

[0051] The present invention introduces a reconfigurable filter of a first LC structure and a second LC structure connected in series and an equivalent high-pass filter network after frequency conversion. At the same time, the key components that determine the upper and lower limits of the frequency are replaced by the capacitance characteristics of the switching device, so that the upper and lower limits of the frequency of the bandpass filter can be continuously adjusted by adjusting the voltage; and the circuit structure is reused, which greatly reduces the chip size and reduces the production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 A flow chart of the steps of a design method for a reconfigurable filter provided in an embodiment of the present invention;

[0053] Figure 2 A reconfigurable filter circuit diagram provided by an embodiment of the present invention;

[0054] Figure 3 A 3×50μm switch device layout structure acting as a variable capacitor in a reconfigurable filter provided in an embodiment of the present invention;

[0055] Figure 4 A schematic diagram of small signal test results of the widest filtering frequency band (highest upper limit, lowest lower limit) of the frequency band continuously adjustable filter provided by an embodiment of the present invention;

[0056] Figure 5 A schematic diagram of small signal test results of a low-frequency filter band (lowest upper limit, lowest lower limit) of a band-continuously adjustable filter provided by an embodiment of the present invention;

[0057] Figure 6 A schematic diagram of small signal test results of a high-frequency filtering band (highest upper limit, highest lower limit) of a continuously adjustable frequency filter provided by an embodiment of the present invention;

[0058] Figure 7 The test results of the reconfigurable filter provided in the embodiment of the present invention. DETAILED DESCRIPTION

[0059] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0060] The present invention provides a design method for a reconfigurable filter. Figure 1 As shown, the method includes the following steps S101 to S105.

[0061] S101, determining an initial circuit of a quasi-elliptical filter network including a first LC structure and a second LC structure connected in series; here, the initial circuit includes: a low-pass filter network, a high-pass filter network, a first variable capacitance module and a second variable capacitance module; the low-pass filter network is connected to the first variable capacitance module; the low-pass filter network is connected to the high-pass filter network; the high-pass filter network is connected to the second variable capacitance module; the low-pass filter network and the high-pass filter network are both connected to a standard impedance, and here, the standard impedance is set to 50Ω.

[0062] The low-pass filter network includes: an LC module and a microstrip line TL2, wherein the LC module includes: a first LC structure and a second LC structure connected in series; the first LC structure includes a microstrip line TL1, an inductor L1 and a capacitor C1 connected in series in sequence; the second LC structure includes a microstrip line TL3, an inductor L2 and a capacitor C2 connected in series in sequence; the microstrip line TL2 is connected in series with the microstrip line TL1 and the microstrip line TL3; and the values ​​of the electrical components in the first LC structure and the second LC structure are the same.

[0063] Here, the initial circuit of the reconfigurable filter is a 5th-order quasi-elliptic filter network (low-pass filter network), that is, based on the 5th-order Chebyshev low-pass network model, the parallel capacitor is improved to a first LC structure and a second LC structure in series, while keeping their values ​​the same, so as to generate a finite transmission zero point and improve the out-of-band suppression performance.

[0064] According to the design requirements of the 5th-order quasi-elliptical filter network (low-pass filter network), select appropriate capacitance and inductance values, refer to the calculation method of Chebyshev low-pass filter design, and use design software for adjustment and optimization. Considering that the main transmission path needs to reduce the insertion loss caused by parasitic parameters, microstrip lines can be used instead of inductor structures. According to the calculated inductance value, it is converted into the characteristic impedance and electrical length of the transmission line. Combined with the process parameters such as the dielectric constant, dielectric layer and surface metal thickness of the microstrip line manufacturing, the microstrip line size calculation tool of the ADS simulation design software is used to calculate that the length and width of the microstrip line TL1 and microstrip line TL3 are 2200μm / 30μm, the length and width of the microstrip line TL2 are 1635μm / 12μm, the inductance of the inductor L1 and the inductor L2 is 410pH, and the capacitance of the capacitor C1 and the capacitor C2 is 280fF.

[0065] S102, calculating a first capacitance range of a variable capacitor in a first variable capacitance module in the initial circuit according to a low-pass filter network in the initial circuit.

[0066] Specifically, in step S102, a first capacitance range of a variable capacitor in a first variable capacitance module in the initial circuit is calculated according to a low-pass filtering network in the initial circuit, including: calculating the first capacitance range according to a first balance condition and parameters of each component in the low-pass filtering network; wherein the first balance condition includes: determining that a DC component in the low-pass filtering network and a radio frequency signal in the low-pass filtering network will not crosstalk in a main path of the low-pass filtering network.

[0067] The first variable capacitor module includes: a capacitor C3, an inductor L3, a DC power supply DC1, a switch device F1, a capacitor C4, an inductor L4 and a DC power supply DC2; the first end of the capacitor C3 is connected to a low-pass filter network, the second end of the capacitor C3 is connected to the first end of the inductor L3 and the gate of the switch device F1; the second end of the inductor L3 is connected to the first end of the DC power supply DC1; the second end of the DC power supply DC1 is grounded; the source and drain of the switch device F1 are connected to the first end of the inductor L4 and the first end of the capacitor C4; the second end of the capacitor C4 is connected to the low-pass filter network; the second end of the inductor L4 is connected to the first end of the DC power supply DC2; the second end of the DC power supply DC2 is grounded.

[0068] Exemplarily, a switch device is used to connect the first LC structure and the second LC structure in series. The size of the switch device needs to be selected. The size determines the capacitance range of the variable capacitor. In addition, it is necessary to ensure that the DC component and the RF signal will not cause crosstalk with the main path. By adjusting the gate index and gate width of the switch device multiple times, the capacitance of the gate source / gate drain capacitance within the voltage adjustment range is consistent with the calculated capacitance variation range. The size of the switch device F1 is selected to be 3×50 μm. Figure 3As shown, the gate-source voltage difference is 3 to 30 V. At the same time, the capacitance of capacitor C3 and capacitor C4 is determined to be 2 pF, and the inductance of inductor L3 and inductor L4 is determined to be 30 nH. Here, the switch device F1 uses a GaN switch active device compatible with the MMIC process, one end of which is connected to the gate, and the other end physically connects the source and drain to realize a voltage-controlled variable capacitor structure.

[0069] S103, calculating the parameters of each component in the high-pass filter network in the initial circuit which is equivalent to the low-pass filter network by means of frequency conversion.

[0070] The high-pass filter network includes: a capacitor C5, a capacitor C6, a microstrip line TL4, a microstrip line TL5 and a microstrip line TL6; the first end of the capacitor C5 is connected to the low-pass filter network, and the second end of the capacitor C5 is connected to the first end of the capacitor C6; the second end of the capacitor C6 is connected to the first end of the microstrip line TL6; the second end of the microstrip line TL6 is grounded; the first end of the microstrip line TL5 is connected to the second end of the capacitor C5, and the second end of the microstrip line TL5 is grounded; the first end of the microstrip line TL4 is connected to the first end of the capacitor C5, and the second end of the microstrip line TL4 is grounded.

[0071] Specifically, in step S103, the parameters of each component in the high-pass filter network equivalent to the low-pass filter network in the initial circuit are calculated by a frequency conversion method, including the following steps S1031 to S1032.

[0072] S1031, based on the actual admittance of the low-pass filter network and the actual source impedance of the low-pass filter network, calculate the impedance conversion factor γ 0 .

[0073] S1032, according to the impedance conversion factor γ 0 The parameters of each component in the high-pass filter network are calculated based on the parameters of each component in the low-pass filter network, and the low-pass filter network is equivalent to a high-pass filter network.

[0074] Exemplarily, a fifth-order quasi-elliptic filter network (low-pass filter network) is transformed into an equivalent high-pass filter network through frequency conversion. Frequency conversion is to convert the variable Ω into the frequency ω of other forms of filters such as high-pass or band-pass.

[0075] Here we first introduce an impedance conversion factor γ 0 , its function is to realize the conversion from normalized impedance to actual impedance.

[0076] Assume the actual source impedance of the filter is Z 0 , the actual source admittance is Y 0 , normalized source impedance g 0 =1, then the impedance conversion factor γ 0There are the following relations:

[0077] When 0 Indicates resistance:

[0078] γ 0 =Z 0 / g 0 ;

[0079] When 0 Indicates conductivity:

[0080] γ 0 =g 0 / Y 0 ;

[0081] The parameters of the components in the low-pass filter network satisfy the following conversion formula:

[0082] L→γ 0 L,C→C / γ 0 ,R→γ 0 R,G→G / γ 0 ;

[0083] When performing the conversion, let g be the common value of the components in the low-pass prototype. Since it is independent of frequency, the following expression is obtained to satisfy the transformation of any form of filter components:

[0084] When g represents resistance:

[0085] R = γ 0 g;

[0086] When g represents conductance:

[0087]

[0088] Assume that the frequency variable of the high-pass filter network is ω and the cutoff frequency is ω c , then the transformation formula is:

[0089]

[0090] Substituting the reactance element g into the equation:

[0091]

[0092] From the above formula, we can see that in the conversion from low-pass filter network to high-pass filter network, the inductor and capacitor components of the two are interchanged. According to the conversion formula, we can get:

[0093] When g represents capacitance:

[0094]

[0095] When g represents inductance:

[0096]

[0097] Here, the frequency conversion calculation method is used to transform the 5th-order quasi-elliptical filter network into an equivalent high-pass filter network. In order to reduce the insertion loss caused by parasitic parameters, the main path inductor is replaced by a microstrip line. After calculation and adjustment optimization, the capacitance of capacitors C5 and C6 is selected to be 1.1pF, the length and width of microstrip lines TL4 and TL6 are 1900μm / 12μm, and the length and width of microstrip line TL2 are 4300μm / 12μm.

[0098] S104, calculating a second capacitance range of a variable capacitor in a second variable capacitance module in the initial circuit according to the high-pass filter network.

[0099] The second variable capacitor module includes: a capacitor C7, an inductor L6, a DC power supply DC3, a switch device F2, a capacitor C8, an inductor L5 and a DC power supply DC4; the first end of the capacitor C7 is connected to the high-pass filter network, the second end of the capacitor C7 is connected to the first end of the inductor L5 and the gate of the second switch device F2; the second end of the inductor L5 is connected to the first end of the DC power supply DC3; the second end of the DC power supply DC3 is grounded; the source and drain of the switch device F2 are connected to the first end of the inductor L6 and the first end of the capacitor C8; the second end of the capacitor C8 is grounded; the second end of the inductor L6 is connected to the first end of the DC power supply DC4; the second end of the DC power supply DC4 is grounded.

[0100] For example, referring to the method for calculating the first capacitance range in S102, the second capacitance range is calculated. After calculation and adjustment optimization, the size of the switch device F2 is selected to be 6×100 μm, such as Figure 4 As shown, the gate-source voltage difference is 4-24V, and the capacitance of capacitors C7 and C8 is determined to be 2pF, and the inductance of inductors L5 and L6 is determined to be 30nH. Here, the switch device F2 uses a GaN switch active device compatible with the MMIC process.

[0101] S105 , optimizing the initial circuit of the reconfigurable filter according to the first capacitance range and the second capacitance range to obtain a reconfigurable filter circuit.

[0102] Specifically, in step S105, the initial circuit of the reconfigurable filter is optimized according to the first capacitance range and the second capacitance range to obtain the reconfigurable filter circuit, including the following steps S1051 to S1052.

[0103] S1051, determining a first frequency band range of a low frequency filter band, a second frequency band range of a high frequency filter band, and a third frequency band range of a wide frequency band in an initial circuit according to the first capacitance range and the second capacitance range.

[0104] S1052, optimizing the parameters of the low-pass filter network, the high-pass filter network, the first variable capacitance module and the second variable capacitance module according to the first frequency band range, the second frequency band range and the third frequency band range to obtain a reconfigurable filter circuit.

[0105] For example, after the overall circuit structure design is completed, Figure 2 As shown, various parameters are optimized again within the three frequency bands of the widest filter band (highest upper limit, lowest lower limit), the low-frequency filter band (lowest upper limit, lowest lower limit), and the high-frequency filter band (highest upper limit, highest lower limit) to ensure the performance of the overall circuit.

[0106] The present invention can respectively control the changes of the upper frequency limit and the lower frequency limit of the bandpass filter by respectively adjusting the gate-source voltage of the switch devices in the low-pass filter network and the high-pass filter network.

[0107] In a specific embodiment provided by the present invention, the test results of the designed band-continuously adjustable filter are as follows: Figure 5 , Figure 6 and Figure 7 As shown, the filter can control the lower frequency limit to continuously change from 4.5 to 5.5 GHz and the upper frequency limit to continuously change from 5.5 to 8 GHz simply by adjusting the voltage of the variable capacitor in the high-pass filter network and the low-pass filter network.

[0108] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. All or part of the present invention can be used in many general or special computer system environments or configurations. For example: personal computers, server computers, handheld devices or portable devices, tablet devices, mobile communication terminals, multi-processor systems, microprocessor-based systems, programmable electronic devices, network PCs, minicomputers, mainframe computers, distributed computing environments including any of the above systems or devices, etc.

[0109] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some or all of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the present invention.

Claims

1. A design method for a reconfigurable filter, characterized in that: include: determining an initial circuit of a quasi-elliptical filter network including a first LC structure and a second LC structure connected in series; Calculating a first capacitance range of a variable capacitor in a first variable capacitance module in the initial circuit according to a low-pass filter network in the initial circuit; Calculate the parameters of each component in the high-pass filter network in the initial circuit which is equivalent to the low-pass filter network by means of frequency conversion; Calculating a second capacitance range of a variable capacitor in a second variable capacitance module in the initial circuit according to the high-pass filter network; The initial circuit of the reconfigurable filter is optimized according to the first capacitance range and the second capacitance range to obtain a reconfigurable filter circuit.

2. The design method of the reconfigurable filter according to claim 1, characterized in that: The step of calculating a first capacitance range of a variable capacitor in a first variable capacitance module in the initial circuit according to a low-pass filter network in the initial circuit comprises: The first capacitance range is calculated based on the first balance condition and the parameters of each component in the low-pass filter network; wherein the first balance condition includes: determining that the DC component in the low-pass filter network and the radio frequency signal in the low-pass filter network will not crosstalk in the main path of the low-pass filter network.

3. The design method of the reconfigurable filter according to claim 1, characterized in that: The method of calculating the parameters of each component in the high-pass filter network in the initial circuit which is equivalent to the low-pass filter network by the frequency conversion method includes: An impedance conversion factor γ0 is calculated according to an actual admittance of the low-pass filter network and an actual source impedance of the low-pass filter network; According to the impedance conversion factor γ0 and the parameters of the components in the low-pass filter network, the parameters of the components in the high-pass filter network are calculated, and the low-pass filter network is equivalent to the high-pass filter network.

4. The design method of a reconfigurable filter according to claim 1, characterized in that: The step of optimizing the initial circuit of the reconfigurable filter according to the first capacitance range and the second capacitance range to obtain a reconfigurable filter circuit comprises: According to the first capacitance range and the second capacitance range, respectively determining a first frequency band range of a low-frequency filter frequency band, a second frequency band range of a high-frequency filter frequency band, and a third frequency band range of a wide frequency band in the initial circuit; The parameters of the low-pass filter network, the high-pass filter network, the first variable capacitance module and the second variable capacitance module are optimized according to the first frequency band range, the second frequency band range and the third frequency band range to obtain a reconfigurable filter circuit.

5. A reconfigurable filter, characterized in that: According to the design method of any one of claims 1 to 4, the reconfigurable filter comprises: a low-pass filter network, a high-pass filter network, a first variable capacitor module and a second variable capacitor module; the low-pass filter network is connected to the first variable capacitor module; The low-pass filter network is connected to the high-pass filter network; The high-pass filter network is connected to the second variable capacitance module; The low-pass filter network and the high-pass filter network are both connected to a standard impedance.

6. The reconfigurable filter according to claim 5, characterized in that: The low-pass filter network includes: an LC module and a microstrip line TL2, wherein the LC module includes: a first LC structure and a second LC structure connected in series; The first LC structure includes a microstrip line TL1, an inductor L1 and a capacitor C1 connected in series in sequence; The second LC structure includes a microstrip line TL3, an inductor L2 and a capacitor C2 connected in series in sequence; The microstrip line TL2 is connected in series with the microstrip line TL1 and the microstrip line TL3.

7. The reconfigurable filter according to claim 6, characterized in that: The values ​​of the electrical components in the first LC structure and the second LC structure are the same.

8. The reconfigurable filter according to claim 5, characterized in that: The first variable capacitance module includes: a capacitor C3, an inductor L3, a DC power supply DC1, a switch device F1, a capacitor C4, an inductor L4 and a DC power supply DC2; The first end of the capacitor C3 is connected to the low-pass filter network, and the second end of the capacitor C3 is connected to the first end of the inductor L3 and the gate of the switch device F1; The second end of the inductor L3 is connected to the first end of the DC power supply DC1; the second end of the DC power supply DC1 is grounded; The source and drain of the switch device F1 are connected to the first end of the inductor L4 and the first end of the capacitor C4; The second end of the capacitor C4 is connected to the low-pass filter network; The second end of the inductor L4 is connected to the first end of the DC power supply DC2; A second terminal of the DC power supply DC2 is grounded.

9. The design method of a reconfigurable filter according to claim 5, characterized in that: The high-pass filter network includes: capacitor C5, capacitor C6, microstrip line TL4, microstrip line TL5 and microstrip line TL6; The first end of the capacitor C5 is connected to the low-pass filter network, and the second end of the capacitor C5 is connected to the first end of the capacitor C6; The second end of the capacitor C6 is connected to the first end of the microstrip line TL6; The second end of the microstrip line TL6 is grounded; The first end of the microstrip line TL5 is connected to the second end of the capacitor C5, and the second end of the microstrip line TL5 is grounded; A first end of the microstrip line TL4 is connected to a first end of the capacitor C5 , and a second end of the microstrip line TL4 is grounded.

10. The design method of a reconfigurable filter according to claim 5, characterized in that: The second variable capacitance module comprises: a capacitor C7, an inductor L6, a DC power supply DC3, a switch device F2, a capacitor C8, an inductor L5 and a DC power supply DC4; The first end of the capacitor C7 is connected to the high-pass filter network, and the second end of the capacitor C7 is connected to the first end of the inductor L5 and the gate of the second switch device F2; The second end of the inductor L5 is connected to the first end of the DC power supply DC3; A second end of the DC power supply DC3 is grounded; The source and drain of the switch device F2 are connected to the first end of the inductor L6 and the first end of the capacitor C8; The second end of the capacitor C8 is grounded; The second end of the inductor L6 is connected to the first end of the DC power supply DC4; A second terminal of the DC power supply DC4 is grounded.

Images