CN219760986U - Band-pass filter and electronic device - Google Patents

Abstract

The present utility model relates to a bandpass filter and an electronic device, the bandpass filter comprising: the first tuning network comprises a first coarse tuning circuit, and is connected with the signal input end; the second tuning network comprises a second coarse tuning circuit, and is coupled with the first tuning network and connected with the signal output end; wherein the first coarse tuning circuit and the second coarse tuning circuit are used for improving linearity of the band-pass filter. By the mode, the linearity of the band-pass filter can be improved on the basis of realizing broadband tuning, so that the intermodulation interference resistance of the band-pass filter is improved.

Description

Band-pass filter and electronic device

Technical Field

The utility model relates to the technical field of communication, in particular to a band-pass filter and an electronic device.

Background

The ultrashort wave radio station is widely applied due to the advantages of wider passband and stable transmission signals. In the prior art, wide-frequency tuning of a band-pass filter is realized by adopting a varactor diode with an ultra-abrupt junction. However, this may cause the linearity of the band-pass filter to be deteriorated.

Disclosure of Invention

In order to solve the problems in the prior art, the utility model provides a band-pass filter and an electronic device, which can solve the problem of poor linearity of a broadband tuning band-pass filter.

The present utility model provides a bandpass filter including: the first tuning network comprises a first coarse tuning circuit, and is connected with the signal input end; the second tuning network comprises a second coarse tuning circuit, and is coupled with the first tuning network and connected with the signal output end; wherein the first coarse tuning circuit and the second coarse tuning circuit are configured to improve linearity of the band-pass filter.

In an embodiment, the first tuning network further comprises: a tap input circuit connected to the signal input, the tap input circuit for adjusting a quality factor of the first tuning network; a first fine tuning circuit connected in parallel with the tap input circuit and the first coarse tuning circuit to achieve coarse and fine tuning of the bandpass; the second tuning network further comprises: the tap output circuit is connected with the signal output end and is used for adjusting the quality factor of the second tuning network; and the second fine adjustment circuit is connected with the tap output circuit and the second coarse adjustment circuit in parallel so as to realize coarse adjustment and fine adjustment of the band-pass.

In an embodiment, the tap input circuit and the tap output circuit comprise a first inductor and a second inductor, the first inductor is connected in series with the second inductor, the signal input terminal is connected to a node between the first inductor and the second inductor in the tap input circuit, and the signal output terminal is connected to a node between the first inductor and the second inductor in the tap output circuit.

In an embodiment, the band-pass filter further includes a first tap inductor and a second tap inductor, one end of the first tap inductor is connected to the signal input end, the other end of the first tap inductor is connected to a node between the first inductor and the second inductor in the tap input circuit, one end of the second tap inductor is connected to the signal output end, and the other end of the second tap inductor is connected to a node between the first inductor and the second inductor in the tap output circuit.

In an embodiment, the first and second fine tuning circuits comprise at least one varactor stack, each of the transformer Rong Erji stacks in the first fine tuning circuit being connected in parallel with the tap input circuit and the first coarse tuning circuit, each of the transformer Rong Erji stacks in the second fine tuning circuit being connected in parallel with the tap output circuit and the second coarse tuning circuit.

In an embodiment, the varactor group comprises a first varactor and a second varactor, the cathodes of the first and second varactors being connected to each other.

In an embodiment, the band pass filter further comprises a first resistor and a second resistor; one end of the first resistor is connected with a tuning voltage input end, and the other end of the first resistor is connected with a node between the first varactor and the second varactor in each varactor group in the first fine tuning circuit; one end of the second resistor is connected with the tuning voltage input end, and the other end of the second resistor is connected with a node between the first varactor and the second varactor in each varactor group in the second fine-tuning circuit.

In an embodiment, the band-pass filter comprises a decoupling capacitor, through which the first fine-tuning circuit and/or the second fine-tuning circuit is connected to the tuning voltage input.

In one embodiment, the first and second coarse tuning circuits include: a selection switch; the gear capacitor group comprises a plurality of gear capacitors, and the selection switch is connected with the gear capacitor group; the selection switch can be used for selectively connecting and conducting different gear capacitors so as to realize coarse adjustment.

In an embodiment, the selection switch comprises a single-pole double-throw switch, the gear capacitor group comprises a first gear capacitor and a second gear capacitor, a normally open end of the single-pole double-throw switch is connected with the first gear capacitor, and a normally closed end of the single-pole double-throw switch is connected with the second gear capacitor.

In an embodiment, the single pole double throw switch is a radio frequency switch, and the first gear capacitor and the second gear capacitor are high Q ceramic capacitors.

In one embodiment, the control terminals of the selection switches in the first and second coarse tuning circuits are connected to each other, and the switch control signal input terminal is connected to a node between the control terminal of the selection switch in the first coarse tuning circuit and the control terminal of the selection switch in the second coarse tuning circuit.

In an embodiment, the band-pass filter further comprises a coupling circuit, the first tuning network and the second tuning network being coupled by the coupling circuit, wherein the coupling circuit comprises a coupling inductance.

In one embodiment, the first tuning network and the second tuning network are connected to ground.

The utility model also provides an electronic device comprising a bandpass filter according to any one of the preceding claims.

The embodiment of the utility model has the beneficial effects that: unlike the prior art, the bandpass filter provided by the present utility model includes: the first tuning network comprises a first coarse tuning circuit, and is connected with the signal input end; the second tuning network comprises a second coarse tuning circuit, and is coupled with the first tuning network and connected with the signal output end; wherein the first coarse tuning circuit and the second coarse tuning circuit are configured to improve linearity of the band-pass filter. In this way, the band-pass filter can improve the linearity of the band-pass filter through the first coarse tuning circuit and the second coarse tuning circuit on the basis of realizing broadband tuning through the first tuning network and the second tuning network, thereby improving intermodulation interference resistance of the band-pass filter.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present utility model, the drawings required for the description of the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present utility model, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a schematic diagram of a band-pass filter according to an embodiment of the present utility model;

FIG. 2 is a schematic diagram of another embodiment of a bandpass filter according to the utility model;

FIG. 3 is a schematic diagram of an embodiment of an electronic device according to the present utility model;

fig. 4 is a block diagram illustrating a structural component of an embodiment of the electronic device of fig. 3.

Detailed Description

The technical solutions in the embodiments of the present utility model will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present utility model. It is to be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the utility model. It should be further noted that, for convenience of description, only some, but not all of the structures related to the present utility model are shown in the drawings. All other embodiments, which can be made by those skilled in the art based on the embodiments of the utility model without making any inventive effort, are intended to be within the scope of the utility model.

The terms "first," "second," "third," and the like in this disclosure are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first", "a second", and "a third" may explicitly or implicitly include at least one such feature. In the description of the present utility model, the meaning of "plurality" means at least two, for example, two, three, etc., unless specifically defined otherwise. All directional indications (such as up, down, left, right, front, back … …) in embodiments of the present utility model are merely used to explain the relative positional relationship, movement, etc. between the components in a particular gesture (as shown in the drawings), and if the particular gesture changes, the directional indication changes accordingly. Furthermore, the terms "comprise" and "have," as well as any variations thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not limited to only those listed steps or elements but may include other steps or elements not listed or inherent to such process, method, article, or apparatus.

Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the utility model. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Those of skill in the art will explicitly and implicitly appreciate that the embodiments described herein may be combined with other embodiments.

The band-pass filter provided by the utility model comprises: the first tuning network comprises a first coarse tuning circuit, and is connected with the signal input end; the second tuning network comprises a second coarse tuning circuit, and is coupled with the first tuning network and connected with the signal output end; wherein the first coarse tuning circuit and the second coarse tuning circuit are configured to improve linearity of the band-pass filter. In this way, the band-pass filter can improve the linearity of the band-pass filter through the first coarse tuning circuit and the second coarse tuning circuit on the basis of realizing broadband tuning through the first tuning network and the second tuning network, thereby improving intermodulation interference resistance of the band-pass filter.

Referring to fig. 1, fig. 1 is a schematic structural diagram of a bandpass filter according to an embodiment of the utility model. The band-pass filter 100 is used to allow waves of a specific frequency band to pass and shield waves of other frequency bands, and simultaneously is used to ensure linearity on the basis of realizing an ultra-wide tuning range so as to improve intermodulation interference resistance.

The band pass filter 100 may include, but is not limited to, a first tuning network 110, a coupling circuit 120, and a second tuning network 130. The first tuning network 110 and the second tuning network 130 are used to filter the input signal to allow waves of a specific frequency band to pass and to shield waves of other frequency bands, while the bandwidth allowed to pass through the frequency bands can also be adjusted. The coupling circuit 120 is configured to couple the first tuning network 110 and the second tuning network 130. The first tuning network 110 is connected to the signal input terminal rf_in to receive a signal. The second tuning network 130 is coupled to the first tuning network 110 through the coupling circuit 120 to achieve an ultra-wide tuning range. The second tuning network 130 is connected to the signal output terminal rf_out to output the filtered signal of the specific frequency band.

Further, the first tuning network 110 may include, but is not limited to, a tap input circuit 111, a first fine tuning circuit 112, and a first coarse tuning circuit 113. The tap input circuit 111 may be used to adjust the quality factor of the first tuning network 110. The first coarse tuning circuit 113 may be used to implement coarse tuning in conjunction with the tap input circuit 111. The first fine tuning circuit 112 may be used to implement fine tuning in conjunction with the tap input circuit 111 and the first coarse tuning circuit 113. Specifically, the tap input circuit 111 is connected to the signal input terminal rf_in to receive a signal. The tap input circuit 111, the first fine tuning circuit 112 and the first coarse tuning circuit 113 are connected in parallel to achieve coarse and fine tuning of the bandpass.

In this embodiment, the second tuning network 130 and the first tuning network 110 are symmetrical. Likewise, the second tuning network 130 may include, but is not limited to, a tap output circuit 131, a second fine tuning circuit 132, and a second coarse tuning circuit 133. The tap output circuit 131 may be used to adjust the quality factor of the second tuning network 130. The second coarse tuning circuit 133 may be used to implement coarse tuning in conjunction with the tap output circuit 131. The second fine tuning circuit 132 may be used to implement fine tuning in conjunction with the tap output circuit 131 and the second coarse tuning circuit 133. Specifically, the tap output circuit 131 is connected to the signal output terminal rf_out to output the filtered signal of the specific frequency band. The tap output circuit 131, the second fine tuning circuit 132 and the second coarse tuning circuit 133 are connected in parallel to achieve coarse and fine tuning of the bandpass.

Further, the first tuning network 110 and the second tuning network 130 are connected to the ground GND to eliminate the filtered signal to ground.

Referring to fig. 1 and fig. 2 in combination, fig. 2 is a schematic structural diagram of another embodiment of a band-pass filter according to the present utility model. The tap input circuit 111 and the tap output circuit 131 may include, but are not limited to, a first inductance L1 and a second inductance L2. The first inductor L1 is connected in series with the second inductor L2. The signal input terminal rf_in is connected to a node between the first inductor L1 and the second inductor L2 IN the tap input circuit 111 to realize a tap input. The signal output terminal rf_out is connected to a node between the first inductor L1 and the second inductor L2 in the tap output circuit 131 to realize tap output. The quality factor of the first tuning network 110 may be improved by adjusting the inductance ratio between the first inductance L1 and the second inductance L2 in the tap input circuit 111. The quality factor of the second tuning network 130 may be improved by adjusting the inductance ratio between the first inductance L1 and the second inductance L2 in the tap output circuit 131.

Further, the band-pass filter 100 may further include a first tap inductance L3 and a second tap inductance L4. One end of the first tap inductor L3 is connected to the signal input terminal rf_in to receive a signal. The other end of the first tap inductor L3 is connected to a node between the first inductor L1 and the second inductor L2 in the tap input circuit 111 to realize tap input. One end of the second tap inductor L4 is connected to the signal output terminal rf_out to output a signal. The other end of the second tap inductor L4 is connected to a node between the first inductor L1 and the second inductor L2 in the tap output circuit 131 to realize tap output.

Further, the first and second fine tuning circuits 112 and 132 may include, but are not limited to, at least one varactor group 1001. In the present embodiment, the first fine adjustment circuit 112 and the second fine adjustment circuit 132 each include two varactor groups 1001. In other embodiments, the first and second fine tuning circuits 112 and 132 may include more than two varactor groups 1001 to meet the fine tuning requirements. Each varactor group 1001 in the first fine tuning circuit 112 is connected in parallel with the tap input circuit 111 and the first coarse tuning circuit 113 to achieve fine tuning. Each varactor group 1001 in the second fine tuning circuit 132 is connected in parallel with the tap output circuit 131 and the second coarse tuning circuit 133 to achieve fine tuning. The varactor diode group 1001 includes a first varactor diode D1 and a second varactor diode D2. The cathodes of the first and second varactors D1 and D2 are connected to each other.

Further, the band-pass filter 100 further includes a first resistor R1 and a second resistor R2. One end of the first resistor R1 is connected to the tuning voltage input terminal v_tuner to isolate the resonant tank. The other end of the first resistor R1 is connected to a node between the first varactor D1 and the second varactor D2 in each varactor group 1001 in the first fine tuning circuit 112, so as to adjust the capacitance of the first varactor D1 and the second varactor D2 by tuning the voltage, thereby achieving fine tuning. One end of the second resistor R2 is connected to the tuning voltage input terminal v_tuner to isolate the resonant tank. The other end of the second resistor R2 is connected to a node between the first varactor D1 and the second varactor D2 in each varactor group 1001 in the second fine tuning circuit 132, so as to adjust the capacitance of the first varactor D1 and the second varactor D2 by tuning the voltage, thereby achieving fine tuning.

Further, the band-pass filter 100 includes a decoupling capacitor C1. The decoupling capacitor C1 may function as decoupling. The first fine tuning circuit 112 and/or the second fine tuning circuit 132 are connected to the tuning voltage input terminal v_tuner through the decoupling capacitor C1 to reduce noise coupled to the tuning voltage input terminal v_tuner by the first fine tuning circuit 112 and/or the second fine tuning circuit 132.

Alternatively, the decoupling capacitor C1 may be a polar capacitor. The polar capacitor has the advantages of small volume, large capacity and low cost.

Further, the first coarse tuning circuit 113 and the second coarse tuning circuit 133 may include, but are not limited to, a selection switch 1002 and a set of gear capacitors 1003. The shift capacitor group 1003 includes a plurality of shift capacitors. In the present embodiment, the gear capacitor set 1003 includes two gear capacitors, such as a first gear capacitor C2 and a second gear capacitor C3. In other embodiments, the set of gear capacitors 1003 may include more than two gear capacitors to meet different coarse tuning ranges or steps. The selection switch 1002 is connected to the shift position capacitor group 1003. Wherein, the selection switch 1002 can selectively connect and connect different gear capacitors to realize coarse adjustment. The selector switch 1002 comprises a single pole double throw switch SPDT. The shift capacitor group 1003 includes a first shift capacitor C2 and a second shift capacitor C3. The normally open end of the single pole double throw switch SPDT is connected with the first gear capacitor C2. The normally closed end of the single pole double throw switch SPDT is connected with the second gear capacitor C3. The control terminals of the selection switch 1002 of the first coarse tuning circuit 113 and the second coarse tuning circuit 133 are connected to each other. The switch control signal input terminal sw_io is connected to a node between the control terminal of the selection switch 1002 in the first coarse tuning circuit 113 and the control terminal of the selection switch 1002 in the second coarse tuning circuit 133, so as to switch and connect different gear capacitors.

Alternatively, the single pole double throw switch SPDT may be a radio frequency switch.

Alternatively, the first gear capacitor C2 and the second gear capacitor C3 may be high Q ceramic capacitors.

In other embodiments, the first coarse tuning circuit and the second coarse tuning circuit may include a selection switch and a gear inductor group. The selection switch can realize coarse adjustment by selecting and connecting different gear inductors in the gear inductor group. When the general frequency band adjusting range is larger than 2 times, the gear inductor is selected to realize coarse adjustment. When the frequency band adjusting range is smaller than 2 times, the gear capacitor is selected to realize coarse adjustment.

Further, the coupling circuit 120 includes a coupling inductance L5. The first tuning network 110 and the second tuning network 130 are coupled by a coupling inductance L5.

In other embodiments, the coupling circuit may include a coupling capacitance. The first tuning network and the second tuning network may be coupled by a coupling capacitance.

With continued reference to fig. 2, the band-pass filter 100 operates as follows:

coarse tuning process: when the frequency band is lower than 1/3 of the tuning range, the switch control signal is supplied through the switch control signal input terminal sw_io to control the selection switch 1002 in the first coarse tuning circuit 113 and the second coarse tuning circuit 133 to select the corresponding shift capacitor (e.g., the first shift capacitor C2, where the capacitance value of the first shift capacitor C2 is greater than the capacitance value of the second shift capacitor C3). When the frequency band is higher than 1/3 of the tuning range, the switch control signal is supplied through the switch control signal input terminal sw_io to control the selection switch 1002 in the first coarse tuning circuit 113 and the second coarse tuning circuit 133 to select the corresponding shift capacitor (e.g., the second shift capacitor C3). In general, the higher the frequency band, the smaller the capacitance value of the shift position capacitance selected by the selection switch 1002.

It will be appreciated that the center frequency of the bandpass is inversely proportional to the capacitance, and the width of the bandpass is directly proportional to the center frequency, so that the smaller the capacitance value of the gear capacitor selected by the selector switch 1002, the larger the corresponding center frequency, and the larger the corresponding bandpass width, to adapt to the high-frequency band.

Fine tuning process: in the low frequency range (for example, the frequency range is lower than 1/3 of the tuning range), after the coarse tuning is completed (the first shift capacitor C2 is selected by the above-mentioned selection switch 1002), the tuning voltage is transmitted through the tuning voltage input terminal v_tuner to change the capacitance values of the first varactor diode D1 and the second varactor diode D2 in the varactor diode group 1001 in the first fine tuning circuit 112 and the second fine tuning circuit 132, so as to adapt to the capacitance values of the first shift capacitor C2 in the shift capacitor group 1003 in the first coarse tuning circuit 113 and the second coarse tuning circuit 133; then, the capacitance values of the first varactor diode D1 and the second varactor diode D2 are adjusted within the adaptive capacitance value range, so that the fine adjustment of the passband within the whole low-frequency range can be realized.

Similarly, in the high frequency range (for example, the frequency range is higher than 1/3 of the tuning range), after the coarse tuning is completed (the second shift capacitor C3 is selected by the above-mentioned selection switch 1002), the tuning voltage is supplied through the tuning voltage input terminal v_tuner to change the capacitance values of the first varactor diode D1 and the second varactor diode D2 in the varactor diode group 1001 in the first fine tuning circuit 112 and the second fine tuning circuit 132, so as to adapt to the capacitance values of the second shift capacitor C3 in the shift capacitor group 1003 in the first coarse tuning circuit 113 and the second coarse tuning circuit 133; then, the capacitance values of the first varactor diode D1 and the second varactor diode D2 are adjusted within the adaptive capacitance value range, so that the fine adjustment of the passband within the whole high-frequency range can be realized.

Compared with a bandpass filter adopting a hyperabrupt junction varactor, the bandpass filter 100 provided by the utility model breaks through the bottleneck of large varactor ratio and high tuning voltage of the hyperabrupt junction varactor, can realize an ultra-wide tuning range by only needing a common varactor, and has the advantages of wide selection range and low cost. Meanwhile, the high-Q ceramic capacitor is connected through the selection switch, so that the ratio of the total capacitance of the nonlinear capacitor of the varactor to the total capacitance in the tuning network is reduced, the linearity of the band-pass filter is improved, and the intermodulation interference resistance of the band-pass filter is improved.

The bandpass filter 100 provided by the present utility model includes: a first tuning network 110 including a first coarse tuning circuit 113, the first tuning network 110 being coupled to the signal input terminal rf_in; a second tuning network 130 including a second coarse tuning circuit 133, the second tuning network 130 being coupled to the first tuning network 110, the second tuning network 130 being connected to the signal output terminal rf_out; wherein the first coarse tuning circuit 113 and the second coarse tuning circuit 133 are used to improve the linearity of the band-pass filter 100. In this way, the band-pass filter 100 can improve the linearity of the band-pass filter 100 through the first coarse tuning circuit 113 and the second coarse tuning circuit 133 on the basis of the broadband tuning through the first tuning network 110 and the second tuning network 130, thereby improving intermodulation interference resistance of the band-pass filter 100.

The band-pass filter 100 provided by the utility model can realize broadband tuning, has good linearity and strong intermodulation interference resistance, and can be applied to a plurality of electronic devices for ultrashort wave communication.

Referring to fig. 3, fig. 3 is a schematic structural diagram of an electronic device according to an embodiment of the utility model. Specifically, the electronic device 1000 may be a mobile phone, a tablet computer, a notebook computer, a wearable device, an intercom, a hand table, a car table, a back table, and the like. The electronic device 1000 may include, but is not limited to, a band pass filter 100.

Referring to fig. 4, fig. 4 is a block diagram illustrating a structural component of an embodiment of the electronic device of fig. 3. Structural components of electronic device 1000 may include, but are not limited to, RF circuitry 910, memory 920, input unit 930, display unit 940, sensor 950, audio circuitry 960, wifi module 970, processor 980, power source 990, and so forth. Wherein the RF circuit 910, the memory 920, the input unit 930, the display unit 940, the sensor 950, the audio circuit 960, and the wifi module 970 are coupled to the processor 980, respectively; the power source 990 is used to supply power to the entire electronic device 1000.

Specifically, RF circuitry 910 is used to send and receive signals; memory 920 is used to store data instruction information; the input unit 930 is used for inputting information, and may specifically include a touch panel 931 and other input devices 932 such as operation keys; the display unit 940 may include a display panel 941, etc.; the sensor 950 includes an infrared sensor, a laser sensor, etc., for detecting a user proximity signal, a distance signal, etc.; a speaker 961 and a microphone 962 are coupled to the processor 980 by an audio circuit 960 for receiving and transmitting audio signals; the wifi module 970 is configured to receive and transmit wifi signals, and the processor 980 is configured to process data information of the electronic device.

The foregoing description is only of embodiments of the present utility model, and is not intended to limit the scope of the utility model, and all equivalent structures or equivalent processes using the descriptions and the drawings of the present utility model or directly or indirectly applied to other related technical fields are included in the scope of the present utility model.

Claims (15)

1. A bandpass filter, comprising:

the first tuning network comprises a first coarse tuning circuit, and is connected with the signal input end;

the second tuning network comprises a second coarse tuning circuit, and is coupled with the first tuning network and connected with the signal output end;

wherein the first coarse tuning circuit and the second coarse tuning circuit are configured to improve linearity of the band-pass filter.

2. A bandpass filter according to claim 1, characterized in that,

the first tuning network further comprises:

a tap input circuit connected to the signal input, the tap input circuit for adjusting a quality factor of the first tuning network;

a first fine tuning circuit connected in parallel with the tap input circuit and the first coarse tuning circuit to achieve coarse and fine tuning of the bandpass;

the second tuning network further comprises:

the tap output circuit is connected with the signal output end and is used for adjusting the quality factor of the second tuning network;

and the second fine adjustment circuit is connected with the tap output circuit and the second coarse adjustment circuit in parallel so as to realize coarse adjustment and fine adjustment of the band-pass.

3. The bandpass filter according to claim 2, wherein the tap input circuit and the tap output circuit comprise a first inductance and a second inductance, the first inductance being connected in series with the second inductance, the signal input terminal being connected to a node between the first inductance and the second inductance in the tap input circuit, the signal output terminal being connected to a node between the first inductance and the second inductance in the tap output circuit.

4. A bandpass filter according to claim 3 further comprising a first tapped inductor and a second tapped inductor, one end of the first tapped inductor being connected to the signal input, the other end of the first tapped inductor being connected to a node between the first inductor and the second inductor in the tap input circuit, one end of the second tapped inductor being connected to the signal output, the other end of the second tapped inductor being connected to a node between the first inductor and the second inductor in the tap output circuit.

5. The bandpass filter according to claim 2, wherein the first and second fine tuning circuits comprise at least one varactor group, each of the first fine tuning circuits having the set of variations Rong Erji in parallel with the tap input circuit and the first coarse tuning circuit, each of the second fine tuning circuits having the set of variations Rong Erji in parallel with the tap output circuit and the second coarse tuning circuit.

6. The bandpass filter according to claim 5, wherein the varactor group comprises a first varactor and a second varactor, cathodes of the first and second varactors being connected to each other.

7. A bandpass filter according to claim 6, wherein,

the band-pass filter further comprises a first resistor and a second resistor;

one end of the first resistor is connected with a tuning voltage input end, and the other end of the first resistor is connected with a node between the first varactor and the second varactor in each varactor group in the first fine tuning circuit;

one end of the second resistor is connected with the tuning voltage input end, and the other end of the second resistor is connected with a node between the first varactor and the second varactor in each varactor group in the second fine-tuning circuit.

8. The bandpass filter according to claim 2, characterized in that the bandpass filter comprises a decoupling capacitor through which the first fine-tuning circuit and/or the second fine-tuning circuit is connected to a tuning voltage input.

9. The bandpass filter according to claim 1, wherein the first and second coarse tuning circuits comprise:

a selection switch;

the gear capacitor group comprises a plurality of gear capacitors, and the selection switch is connected with the gear capacitor group;

the selection switch can be used for selectively connecting and conducting different gear capacitors so as to realize coarse adjustment.

10. The bandpass filter according to claim 9, wherein the selection switch comprises a single pole double throw switch, the set of gear capacitors comprises a first gear capacitor and a second gear capacitor, a normally open end of the single pole double throw switch is connected to the first gear capacitor, and a normally closed end of the single pole double throw switch is connected to the second gear capacitor.

11. The bandpass filter according to claim 10, wherein the single pole double throw switch is a radio frequency switch, and the first gear capacitor and the second gear capacitor are high Q ceramic capacitors.

12. A bandpass filter as defined in claim 11, wherein the control terminals of the selection switches in the first and second coarse tuning circuits are connected to each other, and wherein a switch control signal input terminal is connected to a node between the control terminal of the selection switch in the first coarse tuning circuit and the control terminal of the selection switch in the second coarse tuning circuit.

13. The bandpass filter according to claim 1, further comprising a coupling circuit through which the first tuning network and the second tuning network are coupled, wherein the coupling circuit comprises a coupling inductance.

14. The bandpass filter according to claim 1, wherein the first tuning network and the second tuning network are connected to ground.

15. An electronic device comprising a bandpass filter according to any one of claims 1-14.