Band elimination filter capable of switching between single frequency and double frequency and adjustable in double-frequency bandwidth and application method

Abstract

The invention provides a band elimination filter capable of switching between single frequency and double frequency and adjustable in double-frequency bandwidth and an application method, the upper half part comprises a first micro-strip transmission line, a second micro-strip transmission line and a first micro-strip coupling line which are connected in sequence, and the lower half part comprises a second micro-strip coupling line, a third micro-strip coupling line, a first switch, a second switch and a grounding capacitor. The first microstrip coupling line, the second microstrip coupling line and the third microstrip coupling line are connected with a first port and a second port of the switchable band-stop filter, the first switch is connected with one end of a microstrip line in the second microstrip coupling line and the third microstrip coupling line, the other end of the microstrip line is connected with the grounding capacitor through the second switch, and the second switch is connected with the stop-band adjusting capacitor in series. Switching among the narrow-band dual-frequency band-stop filter, the adjustable dual-frequency band-stop filter and the broadband band-stop filter is achieved by changing the connection and disconnection states of the first switch and the second switch, the more flexible performance in the multi-band and complex environment is guaranteed, and the hardware burden of the system is effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of microwave transmission and integrated circuits, and in particular to a single-frequency and dual-frequency switchable and dual-frequency bandwidth adjustable band-stop filter and an application method thereof. Background Art

[0002] With the explosive development of the fifth generation mobile communication system (5G) and the continuous advancement of the sixth generation mobile communication system (6G), the RF front-end modules in the communication system are developing towards miniaturization, high integration, broadband, and functional integration. Band-stop filters have important applications in the RF front end, and can effectively suppress spurious signals of specific frequencies. For example, wireless broadcasting uses band-stop filters to eliminate the frequency range that is not desired to be transmitted or received, and band-stop filters are used in transceivers to suppress the image frequency generated by the mixer. In traditional RF circuits, the operating frequency band of the band-stop filter is fixed. When processing multi-band signals, multiple channels are usually required, and multiple filters need to be integrated. However, this method has many disadvantages such as large circuit size, low integration, insertion loss, poor port matching, and poor frequency selectivity. Therefore, there is an urgent need for a new solution to provide a band-stop filter with a switchable suppression channel function.

[0003] The present invention uses transmission lines and coupling lines to design a planar compact filtering structure, generates a transmission zero at a specific frequency, designs a radio frequency switching switch through the electrical characteristics of capacitors, inductors and diodes, and realizes a single-frequency and dual-frequency stopband suppression and a dual-frequency stopband bandwidth adjustable functional fusion band-stop filter. In terms of multi-signal suppression, this structure reduces the circuit size and the loss introduced by multi-component devices during transmission compared to the traditional multi-filter series connection method. At the same time, the switch design adapts to the radio frequency band and impedance matching. Therefore, the single-frequency and dual-frequency and dual-frequency band-stop filter structures have important practical and scientific research value. Summary of the invention

[0004] The embodiment of the present invention provides a single-frequency and dual-frequency switchable and dual-frequency bandwidth adjustable band-stop filter and an application method to eliminate or improve one or more defects existing in the prior art and solve the problem that the prior art band-stop filter cannot switch channels.

[0005] One aspect of the present invention provides a single-frequency and dual-frequency switchable and dual-frequency bandwidth adjustable band-stop filter applied to a radio frequency front end, comprising:

[0006] A first microstrip transmission line;

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

[0008] a first microstrip coupling line, wherein first ends of two microstrip lines in the first microstrip coupling line are commonly connected to the second microstrip transmission line, and second ends of the two microstrip lines in the first microstrip coupling line are respectively connected to a first port and a second port;

[0009] a second microstrip coupled line, wherein a first microstrip line in the second microstrip coupled line is connected to the first port;

[0010] a third microstrip coupling line, a first microstrip line of the third microstrip coupling line being connected to the second port;

[0011] The first ends of the second microstrip line in the second microstrip coupling line and the second microstrip line in the third microstrip coupling line are connected through a first switch, and the second ends are connected to a grounding capacitor through a second switch, and 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 stop-band adjustment capacitor 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 stop-band adjustment capacitor is grounded.

[0013] In some embodiments, chip capacitors are disposed 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 manner 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 switchable band-stop filter uses a ceramic-filled polytetrafluoroethylene material as a dielectric substrate, with a dielectric constant of 3.66 and a loss tangent value 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 metal copper with 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 material.

[0019] On the other hand, the present invention also provides an application method of a switchable band-stop filter, the method is performed based on the single-dual-frequency switchable and dual-frequency bandwidth adjustable band-stop filter applied to the radio frequency front end, the method comprising:

[0020] Controlling the first switch and the second switch to be both turned off, so that the switchable band-stop filter responds as a narrow-band dual-frequency band-stop filter;

[0021] Controlling the first switch to be disconnected and the second switch to be connected, the switchable band-stop filter to respond as an adjustable dual-frequency band-stop filter, and adjusting the capacitance value of the stop-band adjustment capacitor to control the dual-frequency bandwidth;

[0022] The first switch is controlled to be connected and the second switch is controlled to be disconnected, and the switchable band-stop filter responds as a broadband band-stop filter.

[0023] In some embodiments, the switchable 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 broadband band stop filter based on a third control signal.

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

[0025] The single-dual-frequency switchable and dual-frequency bandwidth adjustable band-stop filter and application method of the present invention, 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 microstrip coupling line, the second microstrip coupling line and the third microstrip coupling line connect the first port and the second port of the switchable band-stop filter, the first switch connects one end of the microstrip line in the second microstrip coupling line and the third microstrip coupling line, and the other end is connected to the grounding capacitor through the second switch. By changing the connected and disconnected states of the first switch and the second switch, switching between the narrowband dual-frequency band-stop filter, the adjustable dual-frequency band-stop filter and the broadband band-stop filter is realized.

[0026] Furthermore, it has highly flexible stopband suppression. It can quickly switch between the three functions of single stopband, dual-band stopband and dual-band adjustable, effectively suppressing multiple unnecessary frequency bands, reducing signal interference, improving the clarity and quality of the required signal, and improving the adaptability of the system.

[0027] Furthermore, a centralized RF switch design is adopted, and the switch uses lumped capacitors and inductors and switch diodes to achieve the connection and disconnection of different circuits under impedance matching, with minimal insertion loss and return loss. At the same time, it has the advantages of small size and easy integration in the circuit system.

[0028] Furthermore, the enhanced system integration saves space and cost. Compared with the traditional method of connecting multiple filters in series, the single-frequency and dual-frequency switchable filter reduces the number of filters, reduces the volume, reduces system loss, has a higher degree of integration, and meets the needs of miniaturized equipment.

[0029] Additional advantages, purposes, and features of the present invention will be described in part in the following description, and will become apparent to those skilled in the art after studying the following, or may be learned from the practice of the present invention. The purposes and other advantages of the present invention may be achieved and obtained by the structures specifically indicated in the specification and the accompanying drawings.

[0030] Those skilled in the art will appreciate that the objectives and advantages that can be achieved with the present invention are not limited to the above specific description, and the above and other objectives that can be achieved by the present invention will be more clearly understood from the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The drawings described herein are used to provide a further understanding of the present invention, constitute a part of the present application, and do not constitute a limitation of the present invention. In the drawings:

[0032] Figure 1 The present invention is a layout of a single-band and dual-band switchable and dual-band bandwidth adjustable band-stop filter applied to a radio frequency front end according to an embodiment of the present invention.

[0033] FIG2( a ) is a circuit diagram of a single-band and dual-band switchable and dual-band bandwidth adjustable band-stop filter applied to a radio frequency front end according to an embodiment of the present invention.

[0034] FIG. 2( b ) is an actual circuit diagram of the first switch and the second switch in FIG. 2( a ).

[0035] FIG3( a ) is an overall structural diagram of a single- and dual-frequency switchable and dual-frequency bandwidth adjustable band-stop filter applied to a radio frequency front end according to an embodiment of the present invention when the response is a narrow-band dual-frequency band-stop filter.

[0036] FIG3( b ) is an even-mode circuit diagram of the single- and dual-frequency switchable and dual-frequency bandwidth adjustable band-stop filter according to an embodiment of the present invention when the response is a narrow-band dual-frequency band-stop filter.

[0037] FIG3( c ) is an odd-mode circuit diagram of the single- and dual-frequency switchable and dual-frequency bandwidth adjustable band-stop filter according to an embodiment of the present invention when the response is a narrow-band dual-frequency band-stop filter.

[0038] Figure 4 This is a simulation result diagram of the narrowband dual-frequency band-stop filter described in Figure 3(a).

[0039] Figure 5The response of the single-dual-frequency switchable and dual-frequency bandwidth adjustable band-stop filter described in an embodiment of the present invention is an influence diagram of the coefficient K1 on the normalized transmission zero point in the adjustable dual-frequency band-stop filter.

[0040] Figure 6 The single-dual-frequency switchable and dual-frequency bandwidth adjustable band-stop filter according to an embodiment of the present invention is a simulation result diagram of the adjustable dual-frequency band-stop filter under different grounding capacitance states.

[0041] Figure 7 This is a simulation result diagram of the single-dual-frequency switchable and dual-frequency bandwidth adjustable band-stop filter response as described in an embodiment of the present invention, which is an adjustable dual-frequency band-stop filter.

[0042] Figure 8 This is a simulation result diagram of the single-dual-frequency switchable and dual-frequency bandwidth adjustable band-stop filter response as a wideband band-stop filter according to an embodiment of the present invention. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments and the accompanying drawings. Here, the illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

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

[0045] It should be emphasized that the term “include / comprises” when used herein refers to the presence of features, elements, steps or components, 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” herein may refer not only to a direct connection but also to an indirect connection involving an intermediate.

[0047] Compared with dual-band stop filters with switchable functions, traditional microwave filters have some shortcomings. The operating frequency of traditional filters is fixed and cannot be dynamically switched between multiple frequency bands. Therefore, in multi-band applications, multiple filters may be required, which increases the design complexity and volume. Traditional filters cannot adapt to the needs of dynamic spectrum environments or multi-standard communications, and cannot be adjusted in real time according to different signal interference conditions. They can only be connected in parallel through multiple channels, which increases the volume, cost and maintenance complexity. Due to the inability to switch flexibly, the integration of traditional filters with other RF components is low, which increases the design difficulty and reduces the overall efficiency of the system. In contrast, dual-band stop filters with switchable functions can provide more flexible performance in multiple frequency bands and complex environments, and effectively reduce the hardware burden of the system.

[0048] It should be noted in advance that the “first end” and “second end” mentioned in this application refer to the relative input end or output end of a component.

[0049] The purpose of the present invention is to provide a single-dual-frequency switchable and dual-frequency bandwidth adjustable band-stop filter and an application method, by designing a unique topological structure of transmission lines and coupling lines to conduct electromagnetic waves, and using lumped parameter elements to design a two-port switch structure, by adjusting the voltage at the input end of the diode to control the on and off of the switch, thereby realizing the switching of three circuit functions of single-dual-frequency switching and dual-frequency adjustable band-stop (single-frequency band-stop, narrow-band dual-frequency band-stop and dual-frequency bandwidth adjustable). The switchable band-stop filter structure has the advantages of simple structure, small size, easy integration, etc.

[0050] The present invention provides a single-frequency and dual-frequency switchable and dual-frequency bandwidth adjustable band-stop filter, such as Figure 1 The system shown 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 commonly connected to the second microstrip transmission line, and the second ends of the two microstrip lines in the first microstrip coupling line are respectively connected to the first port and the second port.

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

[0054] A third microstrip coupled line, wherein a first microstrip line in the third microstrip coupled line is connected to the second port.

[0055] The first ends of the second microstrip line in the second microstrip coupling line and the second microstrip line in the third microstrip coupling line are connected through a first switch, and the second ends are connected to a grounding capacitor through a second switch, and 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 stop-band adjustment capacitor 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 stop-band adjustment capacitor is grounded.

[0057] In some embodiments, chip capacitors are disposed at both the first port and the second port.

[0058] In some embodiments, the switchable band-stop filter uses a ceramic-filled polytetrafluoroethylene material as a dielectric substrate, with a dielectric constant of 3.66 and a loss tangent value of 0.0037, and the thickness of the dielectric substrate is at least 0.762 mm. Specifically, Rogers RO4350B material is used as the dielectric substrate material. The front side is a microstrip line, and 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 metal copper with a thickness of at least 0.035 mm. The bottom side is a ground, and the ground is covered with metal 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°. Exemplarily, the length of the first microstrip transmission line is 24.9mm, the width is 0.7mm, and it is deployed in a bending structure; the length of the second microstrip transmission line is 28.5mm, the width is 0.8mm, and it is deployed in a bending structure; the length of the two coupling lines in the first microstrip coupling line is 27mm, the width is 0.5mm, the interval is 1mm, and it is deployed in a bending structure; the length of each coupling line in the second microstrip coupling line and the third microstrip coupling line is 28.5mm, the width is 0.2mm, the interval is 0.2mm, and it is deployed in a bending structure. The first port and the second port are both 27.8mm long and 1.67mm wide, and are respectively provided with patch capacitors. The upper part of the switchable band-stop filter includes the first microstrip transmission line with an impedance of Z1, the second microstrip transmission line with an impedance of Z2, and the first microstrip coupling line symmetrical along the longitudinal axis, and its odd and even mode impedance is Z. e3 and Z o3, and its frequency response has a sharp dual-frequency stopband characteristic. The capacitance value of the stopband adjustment capacitor is C. The lower part is composed of a second microstrip coupling line, a third microstrip coupling line, a first switch and a second switch. The second microstrip coupling line and the third microstrip coupling line are respectively connected to the first port and the second port for inputting and outputting the signal to be processed. The first switch controls the upper end connection of the second microstrip coupling line and the third microstrip coupling line, and the second switch controls the connection between the second microstrip coupling line and the third microstrip coupling line and the grounding capacitor. The access of the lower part increases the transmission zero point of the filter. By turning on / off the switch, three different filters can be realized, namely a narrowband dual-frequency band stop filter, an adjustable dual-frequency band stop filter and a broadband dual-frequency band stop filter. Finally, the different responses are shown in Table 1.

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

[0061]

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

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

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

[0065] The circuit of the present invention is a symmetrical structure with the vertical line where the first microstrip transmission line and the second microstrip transmission line are located as the axis, and the left and right branches are laterally symmetrical. 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 to realize the filter design.

[0066] FIG2(a) is a two-dimensional layout model of the present invention, and the structure of its schematic diagram is symmetrical. In order to reduce the size of the two-dimensional layout model, the top two microstrip transmission lines are folded. Chip capacitors are used at the first port and the second port to isolate DC. Similarly, the capacitor at the first switch also isolates DC. The size of the DC isolation capacitor can be set to 0.8mm×0.6mm. The inductor at the second switch isolates AC to prevent microwaves from entering the DC circuit and causing damage. The bottom ground capacitor C is a stopband bandwidth adjustment capacitor. When the switchable band stop filter is in the adjustable dual-band band stop filter response state, the stopband bandwidth can be adjusted by changing the value of the ground capacitor C. In the first switch and the second switch, the reverse current of the switch diode is less than 10μA, and the size is about 1.6mm. The input and output port impedances are both set to Z0, the port width is set to 1.66mm, and the length is set to 10mm.

[0067] When the first switch and the second switch are both disconnected, the response is a narrowband dual-frequency band-stop filter. Figure 3(a) is an overall structural diagram of the narrowband dual-frequency band-stop filter and a schematic diagram of the circuit analysis 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 using an even-mode signal of the same magnitude and phase. The symmetry plane of the even-mode circuit can be equivalent to an ideal magnetic wall. Zero current is equivalent to an open circuit, and all circuits are open at the cutting point. Specifically, the even-mode circuit is provided with a first even-mode transmission line, a second even-mode transmission line, an even-mode coupling line, and a coupled microstrip line (equal to the second microstrip coupling line or the third microstrip coupling line) in the vertical direction. The characteristic impedance of the first even-mode transmission line is 2Z1, which is twice the characteristic impedance of the first microstrip transmission line. The characteristic impedance of the second even-mode transmission line is 2Z2, which is twice the characteristic impedance of the second microstrip transmission line. The characteristic impedance of the even-mode coupling line is Z, and the even-mode impedance of the first microstrip coupling line is Z. e3 , the odd and even 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 the potential difference of zero is equivalent to a short circuit. Specifically, the odd-mode circuit is provided with a first odd-mode coupling line and a coupled microstrip line in the vertical direction. The characteristic impedance of the first odd-mode coupling line is Z. o1 , the odd and even mode impedance of the coupled microstrip line is Z o4 and Z e4 .

[0068] When both the first switch and the second switch are disconnected, the response is a narrowband dual-frequency band-stop filter. After the preset theoretical derivation and impedance calculation, when the single-ended input port Port1 meets the port impedance matching condition, the impedance parameter relationship satisfied by the odd-even mode circuit is obtained, as shown in formula (1):

[0069]

[0070] In formula (1), Y ino1 represents the input admittance of the upper half of the odd-mode circuit, Y ino2 represents the input admittance of the lower half of the odd-mode circuit, Y ine3 represents the input admittance of the upper part of the even-mode circuit, Y ine4 represents the input admittance of the lower part 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 represents the even-mode impedance of the first microstrip coupled line, Z o3represents the odd-mode impedance of the first microstrip coupled line, Z e3 represents the even-mode impedance of the first microstrip coupled line, Z o3 represents the odd-mode impedance of the first microstrip coupled line, Z e4 represents the even-mode impedance of the microstrip coupled line, Z o3 represents the odd-mode impedance of the microstrip coupled line. J represents the ordinal unit. The transmission zero point can be calculated from the input admittance formula as shown in equation (2), where f1 and f2 are the two transmission zero points at both ends (the two transmission zero points with the lowest and highest frequencies), and f3 and f4 are the two transmission zero points in the middle.

[0071]

[0072] in

[0073]

[0074] Based on the circuit parameters of the ideal simulation circuit in Table 2, we get Figure 4 As an example of simulation results when the response of the present invention is a narrow-band dual-frequency band-stop filter.

[0075] Table 2 Circuit parameters of ideal simulation circuit

[0076] <![CDATA[Z1]]> <![CDATA[Z2]]> <![CDATA[Z o3 ]]> <![CDATA[Z e3 ]]> <![CDATA[Z o4 ]]> <![CDATA[Z e4 ]]> C 90Ω 98Ω 80Ω 100Ω 70Ω 170Ω 62pF

[0077] When the first switch and the second switch are both in the off state, the response is a narrowband dual-band stop. The center frequencies of the two stopbands are 0.868GHz and 2.412GHz, respectively. The 30dB stopband suppression intervals are 0.820GHz-0.856GHz and 2.344GHz-2.48GHz, and the 30dB relative bandwidth of the two stopbands is 8.24%. There are two transmission zeros on both sides of the stopband, which greatly improves its selectivity. Using the formula The selectivity was quantitatively characterized, where the selectivity was 228.1dB / GHz and 95.34dB / GHz.

[0078] When the first switch is in the off state and the second switch is in the on state, the response is an adjustable dual-band stop. At this time, the stopband width can be adjusted by changing the capacitor C. The influence of the stopband adjustment capacitor C on the transmission zero point can be quantitatively characterized by equations (4) and (5). The two transmission zero points to the right of the center frequency are:

[0079]

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

[0081]

[0082] in

[0083]

[0084] The present invention uses a formula to more intuitively observe the change trend of the transmission zero point, and characterizes the change trend of the transmission zero points f1 and f2 based on the coefficient K1 as follows: Figure 5 shown.

[0085]

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

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

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

[0089]

[0090] in

[0091]

[0092] Based on the above analysis and design, the switchable band-stop filter provided by the present invention is obtained. The filter can be widely used in antenna feeder arrays, highly selective microwave / RF systems and multi-channel communication networks to reduce image interference and adjacent channel interference, so that the system has higher signal transmission efficiency.

[0093] On the other hand, the present invention further provides an application method of a switchable band-stop filter, the method is based on the above-mentioned single-frequency and dual-frequency switchable and dual-frequency bandwidth adjustable band-stop filter, the method comprises steps S101 to S103:

[0094] Step S101: Control the first switch and the second switch to be turned off, so that the switchable band-stop filter responds to a narrow-band dual-frequency band-stop filter.

[0095] Step S102: Control the first switch to be disconnected and the second switch to be connected, so that the switchable band-stop filter responds as an adjustable dual-band band-stop filter, and adjusts the capacitance value of the stop-band adjustment capacitor to control the dual-band bandwidth.

[0096] Step S103: control the first switch to be connected and the second switch to be disconnected, so that the switchable band-stop filter responds to be a broadband band-stop filter.

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

[0098] In summary, the single-dual-frequency switchable and dual-frequency bandwidth adjustable band-stop filter and application method applied to the RF front end of the present invention, the upper part includes a first microstrip transmission line, a second microstrip transmission line and a first microstrip coupling line connected in sequence, and 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 microstrip coupling line, the second microstrip coupling line and the third microstrip coupling line connect the first port and the second port of the switchable band-stop filter, the first switch connects one end of the microstrip line in the second microstrip coupling line and the third microstrip coupling line, and the other end is connected to the grounding capacitor through the second switch. By changing the connected and disconnected states of the first switch and the second switch, switching between a narrowband dual-frequency band-stop filter, an adjustable dual-frequency band-stop filter and a broadband band-stop filter is realized, ensuring more flexible performance in multiple frequency bands and complex environments, and effectively reducing the hardware burden of the system.

[0099] It should be understood by those skilled in the art 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 the two. Whether it is performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention. When implemented in hardware, it can be, for example, an electronic circuit, an application specific integrated circuit (ASIC), appropriate firmware, a plug-in, a function card, etc. When implemented in software, the elements of the present invention are programs or code segments used to perform the required tasks. The program or code segment can be stored in a machine-readable medium, or transmitted on a transmission medium or a communication link via a data signal carried in a carrier.

[0100] It should be clear that the present invention is not limited to the specific configuration and processing described above and shown in the figures. For the sake of simplicity, a detailed description of the known method is omitted here. In the above embodiments, several specific steps are described and shown as examples. However, the method process of the present invention is not limited to the specific steps described and shown, and those skilled in the art can make various changes, modifications and additions, or change the order between 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 features of other embodiments or replace features of other embodiments.

[0102] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the embodiments of the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

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

2. The single-frequency and dual-frequency switchable and dual-frequency bandwidth adjustable band-stop filter applied to the radio frequency front end according to claim 1 is 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 stop-band adjustment capacitor 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 stop-band adjustment capacitor is grounded.

3. The single-frequency and dual-frequency switchable and dual-frequency bandwidth adjustable band-stop filter applied to the radio frequency front end according to claim 1, characterized in that: Chip capacitors are provided at the first port and the second port.

4. The single-frequency and dual-frequency switchable and dual-frequency bandwidth adjustable band-stop filter applied to the radio frequency 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 manner to save space.

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

7. The single-frequency and dual-frequency switchable and dual-frequency bandwidth adjustable band-stop filter applied to a 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 metal copper with a thickness of at least 0.035 mm.

8. The single-frequency and dual-frequency switchable and dual-frequency bandwidth adjustable band-stop filter applied to a 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 material.

9. An application method of a switchable band-stop filter, characterized in that: The method is performed based on the single-dual-frequency switchable and dual-frequency bandwidth adjustable band-stop filter applied to the radio frequency front end according to any one of claims 1 to 8, and the method comprises: Controlling the first switch and the second switch to be both turned off, so that the switchable band-stop filter responds as a narrow-band dual-frequency band-stop filter; Controlling the first switch to be disconnected and the second switch to be connected, the switchable band-stop filter to respond as an adjustable dual-frequency band-stop filter, and adjusting the capacitance value of the stop-band adjustment capacitor to control the dual-frequency bandwidth; The first switch is controlled to be connected and the second switch is controlled to be disconnected, and the switchable band-stop filter responds as a broadband band-stop filter.

10. The application method of the switchable band-stop filter according to claim 9, characterized in that: The switchable 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 broadband band-stop filter based on a third control signal.

Images