CN111988007A - Bandpass Filters and Filters - Google Patents

Abstract

The invention discloses a band-pass filter and a filter. The band-pass filter includes a band-pass filtering unit and at least one band-stop filtering unit; the band-stop filtering unit is connected to the band-pass filtering unit, and the stop-band frequency range of the band-pass filtering unit is at least partially the same as the guard-band frequency range of the band-pass filtering unit. overlap; wherein, the guardband of the bandpass filtering unit is the frequency band between the passband and the suppression band of the bandpass filtering unit. The technical solution of the embodiment of the present invention is to add a band-stop filter unit to the band-pass filter, the stop-band frequency range of the band-stop filter unit and the guard-band frequency range of the band-pass filter unit at least partially overlap, because the band-stop filter unit can The frequency components in the stopband frequency range are rapidly attenuated, so that the frequency components in the guardband overlapping the stopband frequency range are rapidly attenuated, effectively improving the frequency components in the bandpass filter unit that overlap the stopband frequency range. The attenuation speed of the frequency components within the guardband, thereby improving the roll-off characteristics of the bandpass filter.

Description

Bandpass Filters and Filters

technical field

Embodiments of the present invention relate to the field of wireless communication technologies, and in particular, to a bandpass filter and a filter.

Background technique

RF filters are an important part of modern wireless communication front-ends. RF filters can select frequency bands for a given communication standard and suppress interference and noise in the environment. A radio frequency filter with better performance can help improve the signal-to-noise ratio of the transceiver and reduce its unintended electromagnetic radiation to the surrounding environment.

With the development of wireless communication systems, the information transmission process requires a larger bandwidth, and the frequency band spacing between them is getting smaller and smaller. Therefore, the filter is required to have a larger roll-off to meet the needs of information transmission.

In the prior art, the roll-off can be improved by higher order circuits consisting of more zeros and poles. However, higher-order circuits usually require more inductive components, resulting in larger circuit size and higher losses, so they cannot meet the application requirements of small portable devices.

其中，FBW为滤波器的相对百分比带宽，k²为组成滤波器的谐振器的机电耦合系数，表示电能与机械能相互转换的程度。Therefore, RF designers typically use two techniques to form filters to reduce the size of the filters, miniaturized filters that meet the needs of situations such as handheld mobile applications. The first technique can form filters based on lumped inductive elements such as capacitors and inductors implemented in low-loss technology platforms such as low temperature co-fired ceramics, which have moderate quality factor values and are formed by connecting inductors and capacitors The unloaded quality factor of the series or parallel resonators is usually less than 150. When the quality factor is relatively low, it is necessary to increase the bandwidth to produce low insertion loss. Since the filter insertion loss is inversely proportional to the quality factor and bandwidth of the filter, the lumped inductive element technology can produce large broadband filters, but its rolling The performance is mediocre. A second technique may form filters based on micro-acoustic resonators, such as surface acoustic wave or bulk acoustic wave devices. The quality factor values of filters formed based on micro-acoustic resonators (such as surface acoustic wave or bulk acoustic wave devices) can range from 800 to 10,000 depending on the type of acoustic technology, the materials involved, and the operating frequency range, but only by acoustic devices The relative percent bandwidth of the resulting filter is limited by the electromechanical coupling:

Among them, FBW is the relative percentage bandwidth of the filter, and k ² is the electromechanical coupling coefficient of the resonators that make up the filter, indicating the degree of mutual conversion between electrical energy and mechanical energy.

SUMMARY OF THE INVENTION

The present invention provides a band-pass filter and a filter, so that the band-pass filter has the characteristics of large bandwidth and sharp roll-off at the same time.

In a first aspect, an embodiment of the present invention provides a bandpass filter, including a bandpass filter unit and at least one bandstop filter unit;

The band-stop filtering unit is connected with the band-pass filtering unit, and the stop-band frequency range of the band-stop filtering unit and the guard-band frequency range of the band-pass filtering unit at least partially overlap; wherein, the guard-band of the band-pass filtering unit is a The frequency band between the passband and the rejection band.

Optionally, the band-stop filtering unit includes at least one acoustic resonator.

Optionally, there is one band-stop filtering unit, which is denoted as the first band-stop filtering unit;

The first band-stop filtering unit is connected to the first end of the band-pass filtering unit, and the stop-band frequency range of the first band-stop filtering unit and the lower guard band frequency range of the band-pass filtering unit at least partially overlap; wherein, the lower guard band is The band between the passband of the bandpass filter unit and the suppression band whose frequency is lower than the passband.

Optionally, the first band-stop filtering unit includes a first acoustic resonator, and the first end of the first acoustic resonator is connected to the first end of the band-pass filtering unit and serves as the first end of the band-pass filter; The second end of the band-pass filter unit serves as the second end of the band-pass filter; the second end of the first acoustic resonator and the third end of the band-pass filter unit are connected to the fixed potential end.

Optionally, there is one band-stop filtering unit, denoted as the second band-stop filtering unit;

The second band-stop filter unit is connected to the second end of the band-pass filter unit, and the stop-band frequency range of the second band-stop filter unit at least partially overlaps with the upper guard band frequency range of the band-pass filter unit; wherein the upper guard band is The band between the passband of the bandpass filter unit and the suppression band whose frequency is higher than the passband.

Optionally, the second band-stop filtering unit includes a second acoustic resonator, the first end of the band-pass filtering unit is used as the first end of the band-pass filter, and the first end of the second acoustic resonator is connected to the first end of the band-pass filtering unit. The second end is connected, the second end of the second acoustic resonator is used as the second end of the band-pass filter, and the third end of the band-pass filter unit is connected to the fixed potential end.

Optionally, there are two band-stop filtering units, which are respectively a first band-stop filtering unit and a second band-stop filtering unit;

The first band-stop filter unit is connected to the first end of the band-pass filter unit, the second band-stop filter unit is connected to the second end of the band-pass filter unit, and the stop-band frequency range of the first band-stop filter unit is connected to the band-pass filter unit. The frequency range of the lower guard band overlaps at least partially, and the frequency range of the stop band of the second band-stop filtering unit overlaps at least partially with the frequency range of the upper guard band of the band-pass filtering unit; The band between the band and the suppression band whose frequency is lower than the pass band, and the upper guard band is the band between the pass band of the band-pass filter unit and the suppression band whose frequency is higher than the pass band.

Optionally, the first band-stop filtering unit includes a first acoustic resonator; the second band-stop filtering unit includes a second acoustic resonator;

The first end of the first acoustic resonator is connected to the first end of the band-pass filter unit, and serves as the first end of the band-pass filter, and the second end of the band-pass filter unit is connected to the first end of the second acoustic resonator connected, the second end of the second acoustic resonator serves as the second end of the band-pass filter, and the second end of the first acoustic resonator and the third end of the band-pass filter unit are connected to the fixed potential end.

Optionally, the bandpass filter unit includes at least one first filter circuit and two second filter circuits; each first filter circuit and each second filter circuit include an inductor and a capacitor, and the inductor and the capacitor are connected in parallel;

At least one first filter circuit is connected in series, the first end of the first first filter circuit is used as the first end of the band-pass filter unit, and the second end of the last first filter circuit is used as the second end of the band-pass filter unit; The second filter circuit and the first filter circuit form a π-type circuit, and the second end of the second filter circuit serves as the third end of the band-pass filter unit.

In a second aspect, an embodiment of the present invention further provides a filter, including implementing the bandpass filter according to any one of the first aspect.

In the technical solution of the embodiment of the present invention, the band-pass filter includes at least one band-stop filter unit, and the band-stop filter unit can rapidly attenuate the signal within the stop-band frequency range. The guardband frequency range of the pass filter unit is overlapped. Since the bandstop filter unit can rapidly attenuate the frequency components in the stopband frequency range, the frequency components in the guardband overlapping the stopband frequency range can be rapidly attenuated. The attenuation speed of the frequency components in the guardband overlapping the stopband frequency range in the bandpass filter unit is effectively improved, thereby improving the roll-off characteristic of the bandpass filter.

Description of drawings

1 is a schematic structural diagram of a bandpass filter provided by an embodiment of the present invention;

2 is a schematic performance diagram of a band-stop filtering unit and a band-pass filtering unit provided by an embodiment of the present invention;

3 is a schematic structural diagram of another bandpass filter provided by an embodiment of the present invention;

4 is a performance schematic diagram of an existing bandpass filter and a bandpass filter provided by an embodiment of the present invention;

5 is a schematic structural diagram of another bandpass filter provided by an embodiment of the present invention;

6 is a schematic structural diagram of another bandpass filter provided by an embodiment of the present invention;

7 is a performance schematic diagram of an existing bandpass filter and another bandpass filter provided by an embodiment of the present invention;

8 is a schematic structural diagram of another bandpass filter provided by an embodiment of the present invention;

9 is a schematic structural diagram of another bandpass filter provided by an embodiment of the present invention;

10 is a schematic performance diagram of an existing bandpass filter and another bandpass filter provided by an embodiment of the present invention;

FIG. 11 is a schematic structural diagram of another bandpass filter provided by an embodiment of the present invention.

Detailed ways

In order to make the purposes, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments These are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

FIG. 1 is a schematic structural diagram of a bandpass filter according to an embodiment of the present invention. As shown in FIG. 1 , the bandpass filter includes a bandpass filter unit 110 and at least one bandstop filter unit 120; the bandstop filter unit 120 is connected to the bandpass filter unit 110, and the stopband frequency range of the bandstop filter unit 120 is At least partially overlaps with the guardband frequency range of the bandpass filtering unit 110 ; wherein, the guardband of the bandpass filtering unit 110 is a frequency band between the passband and the rejection frequency band of the bandpass filtering unit 110 .

Specifically, FIG. 1 exemplarily shows that the band-pass filter includes one band-stop filtering unit 120 . In other embodiments, the band-pass filter may further include multiple band-stop filtering units 120 . The band-pass filter unit 110 is a device that allows waves of a specific frequency band to pass through while shielding other frequency bands (for example, an RLC tank can be a band-pass filter unit). When the bandpass filtering unit 110 allows a wave of a specific frequency band to pass, the frequency band corresponding to the wave of the specific frequency band is the passband of the bandpass filtering unit 110 . The frequency bands on both sides of the passband that are not allowed to pass are the suppression frequency bands of the bandpass filter unit 110 . The frequency band between the passband and the rejection frequency band of the bandpass filtering unit 110 is a guardband, and within the guardband range, the bandpass filtering unit 110 realizes the mutual conversion between the passband and the rejection frequency band. The band-stop filtering unit 120 refers to a filter that can pass most frequency components but attenuate frequency components in certain ranges to a very low level, as opposed to the concept of a band-pass filter. Wherein, when the band-stop filtering unit 120 attenuates frequency components in a certain range to a very low level, the frequency components in this range are the stop-band frequency range of the band-stop filtering unit 120 . In the band-pass filter, the stop-band frequency range of the band-stop filtering unit 120 and the guard-band frequency range of the band-pass filtering unit 110 are overlapped, because the band-stop filtering unit 120 can quickly detect the frequency components in the stop-band frequency range. Attenuation, so that the frequency components in the guardband overlapping the stopband frequency range are rapidly attenuated, effectively improving the attenuation speed of the frequency components in the guardband overlapping the stopband frequency range in the bandpass filter unit 110 , thereby improving the roll-off characteristics of the bandpass filter.

Exemplarily, FIG. 2 is a schematic performance diagram of a band-stop filtering unit and a band-pass filtering unit provided by an embodiment of the present invention. Among them, the abscissa is the normalized frequency of the filter, and the ordinate is the insertion loss of the signal. The curve 101 is the performance curve of the band-pass filter unit, the curve 102 is the performance curve of the band-pass filter unit, and the guard band B of the band-pass filter unit 110 is between the pass-band A and the suppression band C of the band-pass filter unit. As can be seen from the figure, the guardband B of the band-pass filtering unit 110 overlaps with the stop-band frequency range of the band-stop filtering unit 120. When the band-pass filter is working, the band-stop filtering unit 120 can detect signals in the stop-band frequency range. Fast attenuation is achieved, so that the frequency components in the guardband B that overlap with it are rapidly attenuated, thereby improving the attenuation speed of the frequency components in the guardband that overlaps with the stopband frequency range in the bandpass filtering unit 110, thereby improving the frequency range of the bandpass filter unit 110. roll-off characteristics of the pass filter.

In addition, it can be seen from FIG. 2 that the roll-off slopes on both sides of the stop band of the band-stop filter unit 120 are different, and the band-stop filter unit 120 can be set in series or in parallel by the band-stop filter unit 120 and the band-pass filter unit 110, so that the band-stop filter unit 120 rolls in the middle. The side with the larger drop slope is close to the passband of the bandpass filter unit 110, which further improves the roll-off characteristic of the bandpass filter.

FIG. 3 is a schematic structural diagram of another bandpass filter provided by an embodiment of the present invention. As shown in FIG. 3 , the band-stop filtering unit 120 includes at least one acoustic resonator.

Specifically, an acoustic resonator refers to an electronic component that generates a resonant frequency based on surface acoustic waves, bulk acoustic waves or other types of acoustic waves. Acoustic resonators can improve the roll-off of the filter formed by the acoustic resonator by reducing the relatively small relative percentage bandwidth range. For example, the electromechanical coupling coefficient ^k of resonators in state-of-the-art surface acoustic wave devices and bulk acoustic wave devices can be as high as 15%, while keeping the quality factor of the filter still above 1000. At this point, the relative percent bandwidth of the filter is limited to about 7.5%.

Commonly used types of acoustic resonators include, but are not limited to, surface acoustic wave resonators based _on LiNbO and LiTaO, bulk acoustic resonators based _on AlN, Sc- or Mg-doped AlN films, such as thin-film cavity acoustic resonators (films). bulkacoustic resonator, FBAR) and solid mounted resonators (Solidly mounted resonators, SMRs), based on transfer integrated single crystal quality piezoelectric thin film (for example, the material of single crystal quality piezoelectric thin film can be LiNbO ₃ , LiTaO ₃ , quartz and AlN at least one of) to form an acoustic resonator. The acoustic resonator has a relatively stable frequency, good anti-interference performance and high quality factor, so it is beneficial to produce a sharp roll-off, which can further improve the roll-off characteristics of the band-pass filter.

It should be noted that, when the band-stop filter unit 120 includes an acoustic resonator, the electromechanical coupling coefficient k ² of the acoustic resonator can be made larger than 12%, so that the stop-band frequency range of the band-stop filter unit 120 is the same as that of the band-pass filter unit 110 . The guardband frequency ranges at least partially overlap.

Continuing to refer to FIG. 3 , there is one band-stop filtering unit 120 , which is denoted as the first band-stop filtering unit 121 ; the first band-stop filtering unit 121 is connected to the first end of the band-pass filtering unit 110 , and the The stopband frequency range at least partially overlaps with the lower guardband frequency range of the bandpass filter unit 110 ; wherein the lower guardband is a frequency band between the passband of the bandpass filter unit and the suppression band whose frequency is lower than the passband.

Specifically, when the stopband frequency range of the first band-stop filtering unit 121 and the lower guardband frequency range of the band-pass filtering unit 110 at least partially overlap, the first band-stop filtering unit 121 may The frequency components of at least a part of the lower guardband whose stop frequency ranges overlap are rapidly attenuated, thereby effectively improving the roll-off of the lower guardband of the bandpass filtering unit 110 . Exemplarily, FIG. 4 is a schematic diagram of the performance of an existing bandpass filter and a bandpass filter provided by an embodiment of the present invention. The abscissa is the normalized frequency, the ordinate is the insertion loss of the signal, the curve 103 is the performance curve of a band-pass filter provided by the embodiment of the present invention, and the curve 104 is the performance curve of the existing band-pass filter . It can be seen from FIG. 4 that the roll-off of the lower guard band of the band-pass filter provided by the embodiment of the present invention is larger than the roll-off of the lower guard band of the existing band-pass filter. It can be seen from this that, by arranging the first band-stop filtering unit 121 at the first end of the band-pass filtering unit 110, the roll-off of the lower guard band of the band-pass filter can be effectively improved. Moreover, the first band-stop filtering unit 121 can increase the zero point of the band-pass filter, so that the roll-off characteristic of the band-pass filter can be further improved.

It should be noted that, the bandpass filter unit 110 provided in the embodiment of the present invention may be a filter unit composed of an arbitrarily formed inductor and capacitor. Exemplarily, FIG. 5 is a schematic structural diagram of another bandpass filter provided by an embodiment of the present invention. As shown in FIG. 5 , the bandpass filter unit 110 includes at least one first filter circuit 111 and two second filter circuits 112 ; each of the first filter circuits 111 and each of the second filter circuits 112 includes an inductor L and a capacitor C , the inductor L and the capacitor C are connected in parallel; at least one first filter circuit 111 is connected in series, the first end of the first first filter circuit 111 is used as the first end of the band-pass filter unit 110, and the first end of the last first filter circuit 111 The two ends serve as the second end of the bandpass filter unit 110 ; the second filter circuit 112 and the first filter circuit 111 form a π-type circuit, and the second end of the second filter circuit 112 serves as the third end of the bandpass filter unit 110 . Specifically, the first filter circuit 111 is connected in series, so that the band-pass filter unit 110 can generate zeros, and the second filter circuit 112 is connected in parallel, so that the band-pass filter unit 110 can generate poles. By setting the number of zeros and poles, it can be set as required. Roll-off and size of the bandpass filter unit 110. In FIG. 5, since the bandpass filter unit 110 has two zeros and two poles, its relative percentage bandwidth is 26%, and the guardband percentage bandwidth is about 16%.

Continuing to refer to FIG. 5 , the first band-stop filtering unit 121 includes a first acoustic resonator 001 , and the first end B11 of the first acoustic resonator 001 is connected to the first end A1 of the band-pass filtering unit 110 and serves as a band-pass filter unit 110 . The first end of the filter; the second end A2 of the bandpass filtering unit 110 is used as the second end of the bandpass filter; the second end B12 of the first acoustic resonator 001 and the third end A3 of the bandpass filtering unit 110 Connect to the fixed potential terminal.

Specifically, as shown in FIG. 5 , the first acoustic resonator 001 is connected in parallel with the band-pass filter unit 110 , and at this time, the side with the larger roll-off slope in the band-stop of the first acoustic resonator 001 can be made close to the band-pass The passband of the filtering unit 110 can further improve the roll-off characteristic of the bandpass filter.

FIG. 6 is a schematic structural diagram of another band-pass filter provided by an embodiment of the present invention. As shown in FIG. 6, there is one band-stop filtering unit 120, which is denoted as the second band-stop filtering unit 122; the second band-stop filtering unit 122 is connected to the second end of the bandpass filter unit 110, and the stopband frequency range of the second bandstop filter unit 122 overlaps at least partially with the upper guardband frequency range of the bandpass filter unit; wherein, the upper guardband is a bandpass filter The band between the passband of a cell and the rejection band with frequencies above the passband.

Specifically, when the stopband frequency range of the second band-stop filtering unit 122 and the upper guardband frequency range of the band-pass filtering unit 110 at least partially overlap, the second band-stop filtering unit 122 may The frequency components of at least part of the upper guardband where the blocking frequency ranges overlap are rapidly attenuated, thereby effectively improving the roll-off of the upper guardband of the bandpass filtering unit 110 . Exemplarily, FIG. 7 is a schematic performance diagram of an existing bandpass filter and another bandpass filter provided by an embodiment of the present invention. The abscissa is the normalized frequency, the ordinate is the insertion loss of the signal, the curve 105 is the performance curve of another bandpass filter provided by the embodiment of the present invention, and the curve 106 is the performance of the existing bandpass filter curve. It can be seen from FIG. 7 that the roll-off of the upper guard band of another band-pass filter provided by the embodiment of the present invention is larger than the roll-off of the upper guard band of the existing band-pass filter. It can be seen from this that, by disposing the second band-stop filtering unit 122 at the second end of the band-pass filtering unit 110, the roll-off of the upper guard band of the band-pass filter can be effectively improved. Moreover, the second band-stop filtering unit 122 can increase the zero point of the band-pass filter, so that the roll-off characteristic of the band-pass filter can be further improved.

FIG. 8 is a schematic structural diagram of another bandpass filter provided by an embodiment of the present invention. As shown in FIG. 8 , the second band-stop filter unit 122 includes a second acoustic resonator 002 , the first end A1 of the band-pass filter unit 110 serves as the first end of the band-pass filter, and the first end A1 of the second acoustic resonator 002 The end B21 is connected to the second end A2 of the bandpass filter unit 110, the second end B22 of the second acoustic resonator 002 serves as the second end of the bandpass filter, and the third end A3 of the bandpass filter unit 110 is connected to the fixed potential end connect.

Specifically, as shown in FIG. 8 , the second acoustic resonator 002 is connected in series with the band-pass filter unit 110 . At this time, the side with the larger roll-off slope in the band rejection of the second acoustic resonator 002 can be brought close to the band-pass filter unit. 110 passband, which can further improve the roll-off characteristics of the bandpass filter.

FIG. 9 is a schematic structural diagram of another band-pass filter provided by an embodiment of the present invention. As shown in FIG. 9 , there are two band-stop filtering units 120 , which are a first band-stop filtering unit 121 and a second band-stop filtering unit, respectively. Unit 122; the first band-stop filtering unit 121 is connected to the first end of the band-pass filtering unit 110, the second band-stop filtering unit 122 is connected to the second end of the band-pass filtering unit, and the stop band of the first band-stop filtering unit 121 The frequency range at least partially overlaps the lower guardband frequency range of the bandpass filtering unit 110, and the stopband frequency range of the second bandstop filtering unit 122 at least partially overlaps the upper guardband frequency range of the bandpass filtering unit 110; wherein, The lower guardband is the frequency band between the passband of the band-pass filtering unit and the suppression frequency band whose frequency is lower than the passband, and the upper guardband is the frequency band between the passband of the bandpass filtering unit and the suppression frequency band whose frequency is higher than the passband.

Specifically, when the stopband frequency range of the first band-stop filtering unit 121 and the lower guardband frequency range of the band-pass filtering unit 110 at least partially overlap, the first band-stop filtering unit 121 may The frequency components of at least a part of the lower guardband whose stop frequency ranges overlap are rapidly attenuated, thereby effectively improving the roll-off of the lower guardband of the bandpass filtering unit 110 . Meanwhile, when the stopband frequency range of the second band-stop filtering unit 122 and the upper guardband frequency range of the band-pass filtering unit 110 at least partially overlap, the second band-stop filtering unit 122 can compare the frequency range of the band-pass filtering unit 110 with the band-stop filter unit 110 . The frequency components of at least part of the upper guardband whose frequency ranges overlap are rapidly attenuated, thereby effectively improving the roll-off of the upper guardband of the bandpass filtering unit 110 . Exemplarily, FIG. 10 is a schematic performance diagram of an existing bandpass filter and another bandpass filter provided by an embodiment of the present invention. The abscissa is the normalized frequency, the ordinate is the insertion loss of the signal, the curve 107 is the performance curve of another bandpass filter provided by the embodiment of the present invention, and the curve 108 is the performance of the existing bandpass filter curve. It can be seen from FIG. 10 that the roll-off of the upper guard band of another band-pass filter provided by the embodiment of the present invention is larger than that of the upper guard band of the existing band-pass filter, and the roll-off of the lower guard band is larger than that of the existing band-pass filter. There is a roll-off of the lower guardband of some bandpass filters. It can be seen from the above that, by arranging the first band-rejection rate unit 121 at the first end of the band-pass filtering unit 110, and disposing the second band-rejection filtering unit 122 at the second end of the band-pass filtering unit 110, the band-pass filtering unit can be effectively improved. Roll-off of the upper and lower guard belts of the device.

FIG. 11 is a schematic structural diagram of another bandpass filter provided by an embodiment of the present invention; as shown in FIG. 11 , the first bandstop filtering unit 121 includes the first acoustic resonator 001; the second bandstop filtering unit 122 includes the first acoustic resonator 001; Two acoustic resonators 002; the first end B11 of the first acoustic resonator 001 is connected to the first end A1 of the bandpass filter unit 110, and serves as the first end of the bandpass filter and the second end of the bandpass filter unit 110. The end A2 is connected to the first end B21 of the second acoustic resonator 002, the second end B22 of the second acoustic resonator 002 serves as the second end of the band-pass filter, the second end B12 of the first acoustic resonator 001 and The third terminal A3 of the band-pass filtering unit 110 is connected to the fixed potential terminal.

Specifically, as shown in FIG. 11 , the first acoustic resonator 001 is connected in parallel with the band-pass filter unit 110 , and at this time, the side with the larger roll-off slope in the band-stop of the first acoustic resonator 001 can be brought close to the band-pass The passband of the filtering unit 110 can further improve the roll-off characteristic of the lower guardband of the bandpass filter. At the same time, the second acoustic resonator 002 is connected in series with the band-pass filter unit 110. At this time, the side with the larger roll-off slope in the band rejection of the second acoustic resonator 002 can be close to the pass-band of the band-pass filter unit 110, so that the The roll-off characteristics of the upper guardband of the band-pass filter are further improved, so the roll-off characteristics of the upper guardband and the lower guardband of the band-pass filter can be simultaneously improved. Also, the first acoustic resonator 001 and the second acoustic resonator 002 can increase the zero point of the band-pass filter, so that the roll-off characteristic of the band-pass filter can be further improved.

An embodiment of the present invention further provides a filter, including a bandpass filter implementing any one of the foregoing embodiments. The filter includes the band-pass filter provided by any embodiment of the present invention, and therefore has the beneficial effects of the band-pass filter provided by the embodiment of the present invention, which is not repeated here.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that it can still be The technical solutions described in the foregoing embodiments are modified, or some technical features thereof are equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (10)

1. a bandpass filter, is characterized in that, comprises bandpass filter unit and at least one bandstop filter unit; The band-stop filtering unit is connected to the band-pass filtering unit, and the stop-band frequency range of the band-stop filtering unit and the guard-band frequency range of the band-pass filtering unit at least partially overlap; wherein, the band-pass filtering unit The guardband of the unit is the frequency band between the passband and the rejection band of the bandpass filter unit. 2. The bandpass filter of claim 1, wherein the bandstop filter unit comprises at least one acoustic resonator. 3. band-pass filter according to claim 2, is characterized in that, described band-stop filtering unit is one, denoted as first band-stop filtering unit; The first band-stop filtering unit is connected to the first end of the band-pass filtering unit, and the stop-band frequency range of the first band-stop filtering unit at least partially intersects the lower guard-band frequency range of the band-pass filtering unit. wherein, the lower guardband is a frequency band between the passband of the bandpass filtering unit and the suppression band whose frequency is lower than the passband. 4. The band-pass filter according to claim 3, wherein the first band-stop filtering unit comprises a first acoustic resonator, and the first end of the first acoustic resonator is connected to the band The first end of the pass filter unit is connected and used as the first end of the band pass filter; the second end of the band pass filter unit is used as the second end of the band pass filter; the first acoustic The second end of the resonator and the third end of the band-pass filtering unit are connected to the fixed potential end. 5. band-pass filter according to claim 1, is characterized in that, described band-stop filtering unit is one, denoted as the second band-stop filtering unit; The second band-stop filtering unit is connected to the second end of the band-pass filtering unit, and the stop-band frequency range of the second band-stop filtering unit at least partially intersects the upper guardband frequency range of the band-pass filtering unit. wherein, the upper guardband is a frequency band between the passband of the bandpass filtering unit and the suppression band whose frequency is higher than the passband. 6. The band-pass filter according to claim 5, wherein the second band-stop filtering unit comprises a second acoustic resonator, and the first end of the band-pass filtering unit serves as the band-pass filter The first end of the second acoustic resonator is connected to the second end of the band-pass filter unit, and the second end of the second acoustic resonator serves as the second end of the band-pass filter. terminal, the third terminal of the band-pass filtering unit is connected to the fixed potential terminal. 7. bandpass filter according to claim 1, is characterized in that, described bandstop filtering unit is two, is respectively the first bandstop filtering unit and the second bandstop filtering unit; The first band-stop filtering unit is connected to the first end of the band-pass filtering unit, the second band-stop filtering unit is connected to the second end of the band-pass filtering unit, and the first band-stop filtering unit The stopband frequency range of the second bandpass filter unit at least partially overlaps with the lower guardband frequency range of the bandpass filter unit, and the stopband frequency range of the second bandpass filter unit and the upper guardband frequency range of the bandpass filter unit at least partially overlap. Partially overlapping; wherein, the lower guardband is a frequency band between the passband of the bandpass filtering unit and the suppression frequency band whose frequency is lower than the passband, and the upper guardband is the frequency band of the bandpass filtering unit. A frequency band between a passband and a rejection frequency band above the passband. 8. The band-pass filter according to claim 7, wherein the first band-stop filtering unit comprises a first acoustic resonator; the second band-stop filtering unit comprises a second acoustic resonator; The first end of the first acoustic resonator is connected to the first end of the band-pass filter unit, and serves as the first end of the band-pass filter, and the second end of the band-pass filter unit is connected to the band-pass filter unit. The first end of the second acoustic resonator is connected, the second end of the second acoustic resonator serves as the second end of the band-pass filter, and the second end of the first acoustic resonator is connected to the second end of the band-pass filter. The third end of the band-pass filtering unit is connected to the fixed potential end. 9. The bandpass filter according to any one of claims 4, 6 or 8, wherein the bandpass filtering unit comprises at least one first filter circuit and two second filter circuits; The first filter circuit and each of the second filter circuits include an inductor and a capacitor, and the inductor and the capacitor are connected in parallel; At least one of the first filter circuits is connected in series, the first end of the first first filter circuit is used as the first end of the band-pass filter unit, and the second end of the last first filter circuit is used as the first end of the band-pass filter unit. The second end of the bandpass filter unit; the second filter circuit and the first filter circuit form a π-type circuit, and the second end of the second filter circuit serves as the third end of the bandpass filter unit. 10. A filter, characterized by comprising the bandpass filter according to any one of claims 1-9.

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