Single- and dual-frequency switchable and dual-frequency bandwidth adjustable bandstop filters and their application methods

Abstract

This invention provides a single-band / dual-band switchable and dual-band bandwidth adjustable bandstop filter and its application method. The upper part includes a first microstrip transmission line, a second microstrip transmission line, and a first microstrip coupling line connected in sequence. The lower part includes a second microstrip coupling line, a third microstrip coupling line, a first switch, a second switch, and a grounding capacitor. The first, second, and third microstrip coupling lines connect to the first and second ports of the bandstop filter. The first switch connects to one end of the microstrip line in the second and third microstrip coupling lines, and the other end is connected to the grounding capacitor through the second switch. The second switch is connected in series with a bandstop adjustment capacitor. By changing the on / off state of the first and second switches, switching between a narrowband dual-band bandstop filter, an adjustable dual-band bandstop filter, and a wideband bandstop filter is achieved, ensuring more flexible performance in multi-band and complex environments, and effectively reducing the hardware burden of the system.

Description

Technical Field

[0001] This invention relates to the fields of microwave transmission and integrated circuit technology, and in particular to a single- or dual-frequency switchable and dual-frequency bandwidth adjustable bandstop filter and its application method. Background Technology

[0002] With the explosive development of fifth-generation (5G) mobile communication systems and the continuous advancement of sixth-generation (6G) mobile communication systems, radio frequency (RF) front-end modules in communication systems are developing towards miniaturization, high integration, broadband, and functional convergence. Band-stop filters have important applications in RF front-ends, effectively suppressing spurious signals at specific frequencies. For example, wireless broadcasting uses band-stop filters to eliminate unwanted transmission or reception frequency ranges, and transceivers use band-stop filters to suppress image frequencies generated by mixers. In traditional RF circuits, the operating frequency band of band-stop filters is fixed. Processing multi-band signals typically requires multiple channels and multiple integrated filters. However, this approach suffers from numerous disadvantages, including large circuit size, low integration density, insertion loss, poor port matching, and poor frequency selectivity. Therefore, a new solution is urgently needed to provide band-stop filters with switchable channel suppression capabilities.

[0003] This invention employs transmission lines and coupling lines to design a compact planar filter structure. It generates transmission zeros at specific frequencies and utilizes the electrical characteristics of capacitors, inductors, and diodes to design an RF switching switch, achieving a combined bandstop filter with single-band and dual-band stopband suppression and adjustable dual-band stopband bandwidth. Compared to traditional multi-filter series methods, this structure reduces circuit size and minimizes losses introduced by multiple components during transmission. Furthermore, the switch design adapts to RF frequency bands and impedance matching. Therefore, this single-band, dual-band, and dual-band bandstop filter structure has significant practical and research value. Summary of the Invention

[0004] This invention provides a single- or dual-frequency switchable and dual-frequency bandwidth adjustable bandstop filter and its application method, in order to eliminate or improve one or more defects existing in the prior art and solve the problem that the prior art bandstop filter cannot switch channels.

[0005] One aspect of the present invention provides a single- or dual-band switchable and dual-band bandwidth adjustable bandstop filter for use in radio frequency front-ends, comprising:

[0006] First microstrip transmission line;

[0007] A second microstrip transmission line, the first end of which is connected to the first microstrip transmission line;

[0008] The first microstrip coupling line has two microstrip lines whose first ends are connected to the second microstrip transmission line, and whose second ends are connected to the first port and the second port, respectively.

[0009] The second microstrip coupling line, wherein the first microstrip line of the second microstrip coupling line is connected to the first port;

[0010] The third microstrip coupling line, wherein the first microstrip line of the third microstrip coupling line is connected to the second port;

[0011] The first end of the second microstrip line in the second microstrip coupling line is connected to the first end of the second microstrip line in the third microstrip coupling line through a first switch, and the second end is connected to a grounding capacitor through a second switch. The second switch is connected in series with a stopband adjustment capacitor.

[0012] In some embodiments, the first switch is composed of a DC blocking capacitor and a first switching diode connected in series, one end of the DC blocking capacitor is connected to a DC power supply greater than 0.7V, and one end of the first switching diode is grounded; the second switch is composed of an AC blocking inductor, a second switching diode, and the stopband adjustment capacitor connected in series, one end of the AC blocking inductor is connected to a DC power supply greater than 0.7V, and one end of the stopband adjustment capacitor is grounded.

[0013] In some embodiments, surface-mount capacitors are provided at both the first port and the second port.

[0014] In some embodiments, the first microstrip transmission line and the second microstrip transmission line are arranged in a folded configuration to save space.

[0015] In some embodiments, the electrical lengths of the first microstrip transmission line, the second microstrip transmission line, the first microstrip coupling line, the second microstrip coupling line, the third microstrip coupling line, and the grounding capacitor are set to θ = 90°.

[0016] In some embodiments, the band-stop filter uses a ceramic-filled polytetrafluoroethylene material as the dielectric substrate, with a dielectric constant of 3.66 and a loss tangent of 0.0037, and the thickness of the dielectric substrate is at least 0.762 mm.

[0017] In some embodiments, the first microstrip transmission line, the second microstrip transmission line, the first microstrip coupling line, the second microstrip coupling line, and the third microstrip coupling line are made of copper and have a thickness of at least 0.035 mm.

[0018] In some embodiments, the first switching diode and the second switching diode are made of gallium arsenide.

[0019] On the other hand, the present invention also provides an application method for a single- or dual-frequency switchable and dual-frequency bandwidth adjustable bandstop filter. The method is based on the aforementioned single- or dual-frequency switchable and dual-frequency bandwidth adjustable bandstop filter applied to an RF front-end, and includes:

[0020] When both the first switch and the second switch are turned off, the band-stop filter responds as a narrowband dual-frequency band-stop filter.

[0021] The first switch is controlled to be open and the second switch is connected. The band-stop filter response is an adjustable dual-frequency band-stop filter, and the capacitance value of the stopband adjustment capacitor is adjusted to control the dual-frequency bandwidth.

[0022] When the first switch is turned on and the second switch is turned off, the band-stop filter responds as a broadband band-stop filter.

[0023] In some embodiments, the band-stop filter switches to the narrowband dual-frequency band-stop filter based on a first control signal, switches to the adjustable dual-frequency band-stop filter based on a second control signal, and switches to the wideband band-stop filter based on a third control signal.

[0024] The beneficial effects of the present invention are at least as follows:

[0025] The single / dual-frequency switchable and dual-frequency bandwidth adjustable bandstop filter and its application method described in this invention comprises, in its upper part, a first microstrip transmission line, a second microstrip transmission line, and a first microstrip coupling line connected in sequence; and in its lower part, a second microstrip coupling line, a third microstrip coupling line, a first switch, a second switch, and a grounding capacitor. The first, second, and third microstrip coupling lines connect to the first and second ports of the bandstop filter. The first switch connects to one end of the microstrip line in the second and third microstrip coupling lines, and the other end is connected to the grounding capacitor via the second switch. By changing the on / off states of the first and second switches, switching between a narrowband dual-frequency bandstop filter, an adjustable dual-frequency bandstop filter, and a broadband bandstop filter is achieved.

[0026] Furthermore, it features highly flexible stopband suppression. It can quickly switch between single stopband, dual-band stop, and dual-band adjustable functions, effectively suppressing multiple unwanted frequency bands, reducing signal interference, improving the clarity and quality of the desired signal, and enhancing the system's adaptability.

[0027] Furthermore, a centralized RF switch design is adopted, using lumped capacitors, inductors, and diodes to achieve impedance matching for connecting and disconnecting different circuits, minimizing insertion and return losses. It also boasts advantages such as small size and easy integration into circuit systems.

[0028] Furthermore, enhanced system integration saves space and cost. Compared to the traditional method of multiple filters connected in series, this single- and dual-frequency switchable filter reduces the number of filters, shrinks the size, reduces system losses, and has a higher degree of integration, making it suitable for the needs of miniaturized devices.

[0029] Additional advantages, objects, and features of the invention will be set forth in part in the description which follows, and will also become apparent in part to those skilled in the art upon studying the description, or may be learned by practice of the invention. The objects and other advantages of the invention can be realized and obtained by means of the structures specifically pointed out in the description and drawings.

[0030] Those skilled in the art will understand that the objectives and advantages achievable with the present invention are not limited to those specifically described above, and that the above and other objectives achievable with the present invention will become clearer from the following detailed description. Attached Figure Description

[0031] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, are not intended to limit the scope of the invention. In the drawings:

[0032] Figure 1 This is a layout of a single- or dual-frequency switchable and dual-frequency bandwidth adjustable bandstop filter applied to the radio frequency front end, as described in an embodiment of the present invention.

[0033] Figure 2(a) is a circuit diagram of a single- or dual-frequency switchable and dual-frequency bandwidth adjustable bandstop filter applied to the radio frequency front end according to an embodiment of the present invention.

[0034] Figure 2(b) is the actual circuit diagram of the first and second switches in Figure 2(a).

[0035] Figure 3(a) is an overall structural diagram of the single- or dual-frequency switchable and dual-frequency bandwidth adjustable bandstop filter applied to the radio frequency front end according to an embodiment of the present invention, when the response is a narrowband dual-frequency bandstop filter.

[0036] Figure 3(b) is an even-mode circuit diagram of the single / dual-frequency switchable and dual-frequency bandwidth adjustable bandstop filter according to an embodiment of the present invention, when the response is a narrowband dual-frequency bandstop filter.

[0037] Figure 3(c) is an odd-mode circuit diagram of the single / dual-frequency switchable and dual-frequency bandwidth adjustable bandstop filter according to an embodiment of the present invention when the response is a narrowband dual-frequency bandstop filter.

[0038] Figure 4 Figure 3(a) shows the simulation results of the narrowband dual-band stop filter.

[0039] Figure 5The response of the single / dual frequency switchable and dual-frequency bandwidth adjustable bandstop filter according to an embodiment of the present invention is shown in the figure of the influence of coefficient K1 on the normalized transmission zero in the adjustable dual-frequency bandstop filter.

[0040] Figure 6 The figure shows the simulation results of a single- or dual-frequency switchable and dual-frequency bandwidth adjustable bandstop filter according to an embodiment of the present invention, under different grounding capacitance conditions.

[0041] Figure 7 The figure shows the simulation results of the single / dual frequency switchable and dual frequency bandwidth adjustable bandstop filter according to an embodiment of the present invention.

[0042] Figure 8 The figure shows the simulation results of a single- or dual-frequency switchable and dual-frequency bandwidth adjustable bandstop filter with a response that is a wideband stop filter according to an embodiment of the present invention. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments and accompanying drawings. Here, the illustrative embodiments and descriptions of this invention are used to explain the invention, but are not intended to limit the invention.

[0044] It should also be noted that, in order to avoid obscuring the invention with unnecessary details, only the structures and / or processing steps closely related to the solution according to the invention are shown in the accompanying drawings, while other details that are not closely related to the invention are omitted.

[0045] It should be emphasized that the term "including / comprises" as used herein refers to the presence of a feature, element, step, or component, but does not exclude the presence or addition of one or more other features, elements, steps, or components.

[0046] It should also be noted that, unless otherwise specified, the term "connection" in this article can refer not only to a direct connection, but also to an indirect connection involving an intermediary.

[0047] Traditional microwave filters have several drawbacks compared to switchable dual-band stop filters. Traditional filters operate at a fixed frequency and cannot dynamically switch between multiple frequency bands. Therefore, multi-band applications may require multiple filters, increasing design complexity and size. Traditional filters cannot adapt to dynamic spectrum environments or the needs of multi-standard communication, and cannot be adjusted in real-time according to different signal interference conditions. They can only be implemented by connecting multiple channels in parallel, which further increases size, cost, and maintenance complexity. Due to their inflexible switching capabilities, traditional filters have lower integration with other RF components, increasing design difficulty and reducing overall system efficiency. In contrast, switchable dual-band stop filters offer more flexible performance across multiple frequency bands and in complex environments, effectively reducing the system's hardware burden.

[0048] It should be noted beforehand that the "first terminal" and "second terminal" mentioned in this application refer to the corresponding input or output terminals on the components.

[0049] The purpose of this invention is to provide a single-frequency / dual-frequency switchable and dual-frequency bandwidth adjustable bandstop filter and its application method. It utilizes a unique topology design for the transmission line and coupling line to conduct electromagnetic waves, and employs a two-port switch structure using lumped parameter elements. The switching on and off is controlled by adjusting the voltage at the diode input, thereby achieving switching between three circuit functions: single-frequency / dual-frequency switching, narrowband dual-frequency bandstop adjustment, and dual-frequency bandwidth adjustable. This bandstop filter structure has advantages such as simple structure, small size, and easy integration.

[0050] This invention provides a single- or dual-frequency switchable bandstop filter with adjustable dual-frequency bandwidth, such as... Figure 1 The diagram includes: a first microstrip transmission line, a second microstrip transmission line, a first microstrip coupling line, a second microstrip coupling line, a third microstrip coupling line, a first switch, a second switch, and a grounding capacitor.

[0051] The first end of the second microstrip transmission line is connected to the first microstrip transmission line.

[0052] The first ends of the two microstrip lines in the first microstrip coupling line are connected to the second microstrip transmission line, and the second ends of the two microstrip lines in the first microstrip coupling line are connected to the first port and the second port, respectively.

[0053] The second microstrip coupling line, in which the first microstrip line is connected to the first port.

[0054] The third microstrip coupling line, in which the first microstrip line is connected to the second port.

[0055] The first end of the second microstrip line in the second microstrip coupling line and the second microstrip line in the third microstrip coupling line are connected by a first switch, and the second end is connected to a grounding capacitor by a second switch. The second switch is connected in series with a stopband adjustment capacitor.

[0056] Specifically, as shown in Figure 2(b), the first switch is composed of a DC blocking capacitor and a first switching diode connected in series. One end of the DC blocking capacitor is connected to a DC power supply greater than 0.7V, and one end of the first switching diode is grounded. The second switch is composed of an AC blocking inductor, a second switching diode, and a stopband adjustment capacitor connected in series. One end of the AC blocking inductor is connected to a DC power supply greater than 0.7V, and one end of the stopband adjustment capacitor is grounded.

[0057] In some embodiments, surface-mount capacitors are provided at both the first port and the second port.

[0058] In some embodiments, the band-stop filter uses ceramic-filled polytetrafluoroethylene (PTFE) as the dielectric substrate, with a dielectric constant of 3.66 and a loss tangent of 0.0037. The thickness of the dielectric substrate is at least 0.762 mm. Specifically, Rogers RO4350B material is used as the dielectric substrate. The front side is a microstrip line, and the first microstrip transmission line, second microstrip transmission line, first microstrip coupling line, second microstrip coupling line, and third microstrip coupling line are made of copper with a thickness of at least 0.035 mm. The bottom side is ground, and the ground plane is covered with copper.

[0059] Reference Figure 1 The electrical lengths of the first microstrip transmission line, the second microstrip transmission line, the first microstrip coupling line, the second microstrip coupling line, the third microstrip coupling line, and the grounding capacitor are set to θ = 90°. For example, the first microstrip transmission line is 24.9 mm long and 0.7 mm wide, deployed using a bent structure; the second microstrip transmission line is 28.5 mm long and 0.8 mm wide, deployed using a bent structure; the two coupling lines in the first microstrip coupling line are 27 mm long, 0.5 mm wide, and spaced 1 mm apart, deployed using a bent structure; the coupling lines in the second and third microstrip coupling lines are each 28.5 mm long, 0.2 mm wide, and spaced 0.2 mm apart, deployed using a bent structure. The first port and the second port are both 27.8 mm long and 1.67 mm wide, and each is equipped with a surface-mount capacitor. The upper part of the band-stop filter, from top to bottom, includes the impedance of the first microstrip transmission line (Z1), the impedance of the second microstrip transmission line (Z2), and the first microstrip coupling line, which is symmetrical along the vertical axis, with odd-even mode impedances of Z1 and Z2. e3 and Z o3Its frequency response exhibits a sharp dual-band stopband characteristic. The stopband adjustment capacitor has a capacitance value of C. The lower half consists of a second microstrip coupling line, a third microstrip coupling line, a first switch, and a second switch. The second and third microstrip coupling lines are connected to the first and second ports, respectively, for inputting and outputting the signals to be processed. The first switch controls the connection of the upper ends of the second and third microstrip coupling lines, and the second switch controls the connection of the second and third microstrip coupling lines to the grounding capacitor. The lower half increases the transmission zero of the filter. By turning the switches on and off, three different filters can be implemented: a narrowband dual-band stop filter, an adjustable dual-band stop filter, and a wideband dual-band stop filter. The final responses are shown in Table 1.

[0060] Table 1. Three states of a band-stop filter

[0061]

[0062] In some embodiments, the first switch comprises a DC blocking capacitor and a first switching diode, and the second switch comprises an AC blocking inductor and a second switching diode. The DC blocking capacitor is 1nF, and the AC blocking inductor is... .

[0063] In some embodiments, the first microstrip transmission line and the second microstrip transmission line are arranged in a folded configuration to save space.

[0064] In some embodiments, the first switching diode and the second switching diode are made of gallium arsenide.

[0065] The circuit of this invention has a symmetrical structure with the vertical lines of the first and second microstrip transmission lines as the axis and the left and right branches being symmetrical laterally. Therefore, the odd-even mode impedance analysis method can be used for theoretical analysis to calculate and obtain the relationship between the impedance parameters in the circuit, so as to realize the filter design.

[0066] Figure 2(a) is a two-dimensional layout model of the present invention. Its schematic diagram is symmetrically constructed. To reduce size, the top two microstrip transmission lines are folded in the two-dimensional layout model. Surface-mount capacitors are used at the first and second ports to isolate DC current. Similarly, the capacitor at the first switch also isolates DC current. The size of the DC blocking capacitor can be set to... The inductor at the second switch isolates AC power, preventing microwaves from entering the DC circuit and causing damage. The bottom grounding capacitor C is a stopband bandwidth adjustment capacitor; when the bandstop filter is in the adjustable dual-frequency bandstop filter response state, changing the value of the grounding capacitor C adjusts the stopband bandwidth. In the first and second switches, the reverse current of the switching diodes is less than... The dimensions are approximately 1.6mm. The input and output port impedances are both set to Z0, the port width is 1.66mm, and the length is 10mm.

[0067] When both the first and second switches are open, the response is a narrowband dual-band stop filter. Figure 3(a) is the overall structure diagram of the narrowband dual-band stop filter, and the circuit analysis schematic diagram under odd and even mode excitation. First, an odd-mode excitation signal is added to the metal circuit layer, and the corresponding odd-mode circuit is analyzed. As shown in Figure 3(b), the even-mode circuit is excited by an even-mode signal with the same magnitude and phase. The symmetry plane of the even-mode circuit can be equivalent to an ideal magnetic wall. The current is zero, which is equivalent to an open circuit, and all circuits are open at the cutting point. Specifically, the even-mode circuit has a first even-mode transmission line, a second even-mode transmission line, an even-mode coupling line, and a coupling microstrip line (equal to the second microstrip coupling line or the third microstrip coupling line) arranged in sequence along the vertical direction. The characteristic impedance of the first even-mode transmission line is twice the characteristic impedance of the first microstrip transmission line, which is 2Z1. The characteristic impedance of the second even-mode transmission line is twice the characteristic impedance of the second microstrip transmission line, which is 2Z2. The characteristic impedance of the even-mode coupling line is the even-mode impedance of the first microstrip coupling line, which is Z. e3 The odd-mode impedance of the coupled microstrip line is Z. o4 and Z e4 Then, an even-mode excitation signal is added to the metal circuit layer, and the corresponding odd-mode circuit is analyzed. As shown in Figure 3(c), the odd-mode circuit is excited by an odd-mode signal with opposite magnitude and phase. The symmetry plane of the odd-mode circuit can be equivalent to an ideal electric wall, and a potential difference of zero is equivalent to a short circuit. Specifically, the odd-mode circuit has a first odd-mode coupling line and a coupling microstrip line arranged sequentially along the vertical direction. The characteristic impedance of the first odd-mode coupling line is Z, and the odd-mode impedance of the first microstrip coupling line is Z. o1 The odd-mode impedance of the coupled microstrip line is Z. o4 and Z e4 .

[0068] When both the first and second switches are open, the response is a narrowband dual-band stop filter. Based on the pre-defined theoretical derivation and impedance calculation, when the single-ended input port Port1 satisfies the port impedance matching condition, the impedance parameter relationship satisfied by the odd-even mode circuit at this time is obtained, as shown in formula (1):

[0069] (1)

[0070] In formula (1), Y ino1 Y represents the input admittance of the upper half of the odd-mode circuit. ino2 Y represents the input admittance of the lower half of the odd-mode circuit. ine3 Y represents the input admittance of the upper half of the even-mode circuit. ine4Z represents the input admittance of the lower half of the even-mode circuit, Z1 represents the characteristic impedance of the first microstrip transmission line, Z2 represents the characteristic impedance of the second microstrip transmission line, and Z... e3 Z represents the even-mode impedance of the first microstrip coupled line. o3 Z represents the odd-mode impedance of the first microstrip coupled line. e3 Z represents the even-mode impedance of the first microstrip coupled line. o3 Z represents the odd-mode impedance of the first microstrip coupled line. e4 Z represents the even-mode impedance of the microstrip coupled line. o3 represents the odd-mode impedance of the microstrip coupled line. J represents the ordinal unit. The transmission zeros can be calculated from the input admittance formula as shown in equation (2), where f1 and f2 are the two transmission zeros at the two ends (the two transmission zeros with the lowest and highest frequencies), and f3 and f4 are the two transmission zeros in the middle.

[0071] (2)

[0072] in

[0073] (3)

[0074] The circuit parameters of the ideal simulation circuit are based on Table 2. Figure 4 This serves as an example of simulation results when the response of this invention is a narrowband dual-band stop filter.

[0075] Table 2 Circuit parameters of the ideal simulation circuit

[0076]

[0077] When both the first and second switches are closed, the response is a narrowband dual-band stop. The center frequencies of the two stopbands are 0.868 GHz and 2.412 GHz, respectively, with 30 dB stopband suppression ranges of 0.820 GHz–0.856 GHz and 2.344 GHz–2.48 GHz. The relative 30 dB bandwidth of the two stopbands is 8.24%. Two transmission zeros are located immediately adjacent to the two sides of the stopbands, significantly improving selectivity. (Using the formula...) Selectivity was quantitatively characterized, with selectivity values ​​of 228.1 dB / GHz and 95.34 dB / GHz.

[0078] When the first switch is open and the second switch is closed, the response is an adjustable dual-band stop. The stopband width can be adjusted by changing the capacitor C. Equations (4) and (5) can quantitatively characterize the effect of the stopband adjustment capacitor C on the transmission zeros. The two transmission zeros to the right of the center frequency are:

[0079] (4)

[0080] The three transmission zeros to the left of the center frequency are:

[0081] (5)

[0082] in

[0083] (6)

[0084] This invention provides a more intuitive observation of the changing trends of transmission zeros through formula derivation, using coefficient K1 to characterize the changing trends of transmission zeros f1 and f2, as follows: Figure 5 As shown.

[0085] (7)

[0086] Figure 6 Three typical capacitance values ​​were used to characterize the effect of changing the stopband adjustment capacitor C on the transmission zeros f3 and f4. It can then be concluded that both K1 and C can change the transmission zero and thus change the stopband bandwidth.

[0087] Figure 7 This is an example of simulation results when the response of this invention is an adjustable dual-band stop filter.

[0088] When the first switch is in the connected state and the second switch is in the open state, the response is a wideband stop filter, and equations (8) and (9) characterize the transmission zeros of the wideband stop filter. It has a relative bandwidth of 113%. The transmission zeros f1 are located at the center frequency, f2 and f4 are located at the outermost two sides (the highest and lowest frequencies), and f3 and f5 are located on both sides of the center frequency.

[0089] (8)

[0090] in

[0091] (9)

[0092] Based on the above analysis and design, the band-stop filter provided by this invention is obtained. This filter can be widely used in antenna feeder arrays, high-selectivity microwave / RF systems, and multi-channel communication networks to reduce image interference and adjacent channel interference, thereby enabling the system to have higher signal transmission efficiency.

[0093] On the other hand, the present invention also provides an application method for a single- or dual-frequency switchable and dual-frequency bandwidth adjustable bandstop filter. The method is based on the aforementioned single- or dual-frequency switchable and dual-frequency bandwidth adjustable bandstop filter and includes steps S101 to S103:

[0094] Step S101: Control both the first and second switches to be open, and the band-stop filter response becomes a narrowband dual-frequency band-stop filter.

[0095] Step S102: Control the first switch to be open and the second switch to be open, the band-stop filter response to be an adjustable dual-frequency band-stop filter, and adjust the capacitance value of the stopband adjustment capacitor to control the dual-frequency bandwidth.

[0096] Step S103: Control the first switch to be connected and the second switch to be disconnected, and the band-stop filter response becomes a broadband band-stop filter.

[0097] In some embodiments, the band-stop filter switches to a narrowband dual-frequency band-stop filter based on a first control signal, to an adjustable dual-frequency band-stop filter based on a second control signal, and to a wideband band-stop filter based on a third control signal. The first, second, and third control signals can be issued based on a preset controller to achieve automatic and flexible switching.

[0098] In summary, the single / dual-band switchable and dual-band bandwidth adjustable bandstop filter and its application method described in this invention for use in RF front-ends comprises, in its upper part, a first microstrip transmission line, a second microstrip transmission line, and a first microstrip coupling line connected in sequence; and in its lower part, a second microstrip coupling line, a third microstrip coupling line, a first switch, a second switch, and a grounding capacitor. The first, second, and third microstrip coupling lines connect to the first and second ports of the bandstop filter. The first switch connects to one end of the microstrip line in the second and third microstrip coupling lines, and the other end is connected to the grounding capacitor via the second switch. By changing the on / off state of the first and second switches, switching between a narrowband dual-band bandstop filter, an adjustable dual-band bandstop filter, and a wideband bandstop filter is achieved, ensuring more flexible performance in multi-band and complex environments and effectively reducing the hardware burden of the system.

[0099] Those skilled in the art will understand that the exemplary components, systems, and methods described in conjunction with the embodiments disclosed herein can be implemented in hardware, software, or a combination of both. Whether implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this invention. When implemented in hardware, it can be, for example, electronic circuits, application-specific integrated circuits (ASICs), appropriate firmware, plug-ins, function cards, etc. When implemented in software, the elements of this invention are programs or code segments used to perform the desired tasks. The programs or code segments can be stored in a machine-readable medium or transmitted over a transmission medium or communication link via data signals carried in a carrier wave.

[0100] It should be understood that the present invention is not limited to the specific configurations and processes described above and illustrated in the figures. For the sake of brevity, a detailed description of known methods is omitted. In the above embodiments, several specific steps are described and illustrated as examples. However, the method of the present invention is not limited to the specific steps described and illustrated. Those skilled in the art may make various changes, modifications, and additions, or change the order of the steps after understanding the spirit of the present invention.

[0101] In the present invention, features described and / or illustrated for one embodiment may be used in the same or similar manner in one or more other embodiments, and / or combined with or replace features of other embodiments.

[0102] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A single- or dual-band switchable and dual-band bandwidth adjustable bandstop filter for use in radio frequency front-ends, characterized in that, include: First microstrip transmission line; A second microstrip transmission line, the first end of which is connected to the first microstrip transmission line; The first microstrip coupling line has two microstrip lines whose first ends are connected to the second microstrip transmission line, and whose second ends are connected to the first port and the second port, respectively. The second microstrip coupling line, wherein the first microstrip line of the second microstrip coupling line is connected to the first port; The third microstrip coupling line, wherein the first microstrip line of the third microstrip coupling line is connected to the second port; The first end of the second microstrip line in the second microstrip coupling line is connected to the first end of the second microstrip line in the third microstrip coupling line through a first switch, and the second end is connected to a grounding capacitor through a second switch. The second switch is connected in series with a stopband adjustment capacitor.

2. The single / dual-band switchable and dual-band bandwidth adjustable bandstop filter applied to the RF front end according to claim 1, characterized in that, The first switch is composed of a DC blocking capacitor and a first switching diode connected in series. One end of the DC blocking capacitor is connected to a DC power supply greater than 0.7V, and one end of the first switching diode is grounded. The second switch is composed of an AC blocking inductor, a second switching diode, and the stopband adjustment capacitor connected in series. One end of the AC blocking inductor is connected to a DC power supply greater than 0.7V, and one end of the stopband adjustment capacitor is grounded.

3. The single / dual-band switchable and dual-band bandwidth adjustable bandstop filter applied to the radio frequency front end according to claim 1, characterized in that, Both the first port and the second port are equipped with surface-mount capacitors.

4. The single / dual-band switchable and dual-band bandwidth adjustable bandstop filter applied to the RF front end according to claim 1, characterized in that, The first microstrip transmission line and the second microstrip transmission line are arranged in a folded configuration to save space.

5. The single / dual-band switchable and dual-band bandwidth adjustable bandstop filter applied to the radio frequency front end according to claim 1, characterized in that, The electrical lengths of the first microstrip transmission line, the second microstrip transmission line, the first microstrip coupling line, the second microstrip coupling line, the third microstrip coupling line, and the grounding capacitor are set to θ = 90°.

6. The single / dual-band switchable and dual-band bandwidth adjustable bandstop filter applied to the radio frequency front end according to claim 1, characterized in that, The band-stop filter uses polytetrafluoroethylene (PTFE) material filled with ceramic as the dielectric substrate, with a dielectric constant of 3.66 and a loss tangent of 0.0037. The thickness of the dielectric substrate is at least 0.762 mm.

7. The single / dual-band switchable and dual-band bandwidth adjustable bandstop filter applied to the radio frequency front end according to claim 6, characterized in that, The first microstrip transmission line, the second microstrip transmission line, the first microstrip coupling line, the second microstrip coupling line, and the third microstrip coupling line are made of copper and have a thickness of at least 0.035 mm.

8. The single / dual-band switchable and dual-band bandwidth adjustable bandstop filter applied to the radio frequency front end according to claim 2, characterized in that, The first switching diode and the second switching diode are made of gallium arsenide.

9. An application method for a single- or dual-frequency switchable and dual-frequency bandwidth adjustable bandstop filter, characterized in that, The method is performed based on the single- or dual-band switchable and dual-band bandwidth adjustable bandstop filter applied to the radio frequency front end as described in any one of claims 1 to 8, and the method includes: When both the first switch and the second switch are turned off, the band-stop filter responds as a narrowband dual-frequency band-stop filter. The first switch is controlled to be disconnected and the second switch is connected. The band-stop filter responds to be an adjustable dual-frequency band-stop filter, and the capacitance value of the stopband adjustment capacitor is adjusted to control the dual-frequency bandwidth. When the first switch is turned on and the second switch is turned off, the band-stop filter responds as a broadband band-stop filter.

10. The application method of the single / dual-frequency switchable and dual-frequency bandwidth adjustable bandstop filter according to claim 9, characterized in that, The band-stop filter switches to the narrowband dual-frequency band-stop filter based on a first control signal, switches to the adjustable dual-frequency band-stop filter based on a second control signal, and switches to the wideband band-stop filter based on a third control signal.

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