CN115799781B - Coupled line band-pass filter - Google Patents
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Abstract
The embodiment of the application provides a coupled line band-pass filter, the filter includes microwave input port, microwave output port, coupled line unit and inductance capacitance unit at least, the both ends of coupled line unit respectively with microwave input port and microwave output port connects, the other port ground connection of coupled line unit, inductance capacitance unit with coupled line unit connects in parallel, inductance capacitance unit includes inductance and the electric capacity of establishing ties each other, adjusts filter bandwidth and out-of-band rejection through the Ze and Zo value of coupling line in the regulation coupled line unit, adjusts filter frequency and in-band matching through the length of regulation coupled line and inductance capacitance unit, and simple structure, easily realizes, can compromise the problem of small-size when solving the high performance of filter.
Description
Technical Field
The application relates to the technical field of filters, in particular to a coupled line band-pass filter.
Background
The filter is widely applied to the field of wireless communication, and the filter passes frequency band signals which are needed to be used, and unwanted frequency band signals are filtered, for example, base station communication, mobile phone communication and the like. The filter in-band impairments directly affect the receive sensitivity of the wireless communication signal and out-of-band rejection directly affects the interference of the out-of-band signal with the in-band signal.
Existing filter implementations generally include three types. The first is the use of lumped elements in the form of capacitive inductors, which form filters are difficult to implement at high frequencies (frequencies greater than 5 GHz); the second is the use of acoustic surface or bulk acoustic wave implementation, i.e. SAW and BAW form filters, which are also difficult to implement at high frequencies; the third is realized by using a microwave transmission line and utilizing a multi-section coupling line (quarter wavelength), as shown in fig. 1, wherein the input of the filter is I1, the output of the filter is O1, and the filter has better performance, but the size is difficult to be small, and the high integration is difficult to realize, so that the filter is deficient in practical application.
However, with the development of technology, modern communication systems have increasingly high requirements for filters, low in-band insertion loss, high out-of-band suppression, and high roll-off, and also need to be small in size. However, the implementation of the existing filter is not compatible with the requirements of the modern communication system for the filter.
Accordingly, there is a need to provide a new filter to meet the above-mentioned needs.
Disclosure of Invention
To solve one or more of the above-mentioned technical problems in the prior art, embodiments of the present application provide a coupled line bandpass filter to solve the problems in the prior art.
In order to achieve the above purpose, the technical scheme adopted by the application for solving the technical problems is as follows:
the application provides a coupled line band-pass filter, the filter includes microwave input port, microwave output port, coupled line unit and inductance capacitance unit at least, the both ends of coupled line unit respectively with microwave input port and microwave output port connects, the other port ground connection of coupled line unit, inductance capacitance unit with coupled line unit connects in parallel, inductance capacitance unit includes mutual series connection's inductance and electric capacity.
In a specific embodiment, the inductance-capacitance unit includes a stage, the coupling line unit includes a coupling line, the stage the inductance-capacitance unit includes a first inductance and a first capacitance that are connected in series, one end of the first inductance is connected to the microwave input port, the other end of the first inductance is connected to one end of the first capacitance, and the other end of the first capacitance is connected to the microwave output port.
In a specific embodiment, the length of the coupled line is equal to a quarter wavelength of the in-band operating center frequency of the filter.
In a specific embodiment, the inductance-capacitance unit comprises N stages, the coupling line unit comprises N coupling lines which are mutually connected in series, the N-th stage inductance-capacitance unit is connected in parallel to two ends of the N-th coupling line, the N-th stage inductance-capacitance unit comprises an N-th inductance and an N-th capacitance which are mutually connected in series, and N is more than or equal to 2, N is less than or equal to [1, N ].
In a specific embodiment, one end of a first inductor in the first stage inductance-capacitance unit is connected with the microwave input port, the other end of the first inductor is connected with one end of the first capacitor, the other end of the first capacitor is connected with one end of the first coupling line far away from the microwave input port, one end of an nth inductor in the nth stage inductance-capacitance unit is connected with one end of the nth coupling line far away from the microwave output port, the other end of the nth inductor is connected with one end of the nth capacitor, and the other end of the nth capacitor is connected with the microwave output port.
In a specific embodiment, the lengths of the N coupled lines are each equal to a quarter wavelength of an in-band operating center frequency of the filter.
In a specific embodiment, the inductance-capacitance unit comprises a first stage, the coupling line unit comprises M coupling lines which are mutually connected in series, the first stage is connected with the two ends of the coupling line unit in parallel, M is more than or equal to 2, the inductance-capacitance unit comprises a first inductor and a first capacitor which are mutually connected in series, one end of the first inductor is connected with the microwave input port, the other end of the first inductor is connected with one end of the first capacitor, and the other end of the first capacitor is connected with the microwave output port.
In a specific embodiment, the length of each of the M coupled lines is equal to one quarter wavelength of the in-band operating center frequency of the filter.
In a specific embodiment, the filter further includes a capacitance unit, the coupling line unit includes a coupling line, the inductance-capacitance unit, the capacitance unit, and the coupling line are connected in parallel, the inductance-capacitance unit includes a first inductance and a first capacitance connected in series with each other, and the capacitance unit includes a second capacitance.
In a specific embodiment, one end of the first inductor is connected to the microwave input port, the other end of the first inductor is connected to one end of the first capacitor, the other end of the first capacitor is connected to the microwave output port, one end of the second capacitor is connected to the microwave input port, and the other end of the second capacitor is connected to the microwave output port.
In a specific embodiment, the length of the coupled line is equal to a quarter wavelength of the in-band operating center frequency of the filter.
In a specific embodiment, the coupled line is realized by a strip line in the form of a spiral.
The beneficial effects that technical scheme that this application embodiment provided brought are:
the coupling line band-pass filter at least comprises a microwave input port, a microwave output port, a coupling line unit and an inductance-capacitance unit, wherein two ends of the coupling line unit are respectively connected with the microwave input port and the microwave output port, the other ends of the coupling line unit are grounded, the inductance-capacitance unit is connected with the coupling line unit in parallel, the inductance-capacitance unit comprises an inductance and a capacitance which are connected in series, the bandwidth and the out-of-band inhibition of the filter are regulated by regulating the Ze and Zo values of the coupling line in the coupling line unit, and the frequency and the in-band matching of the filter are regulated by regulating the length of the coupling line and the inductance-capacitance unit.
Further, the arrangement of the coupling line is realized by the strip line in the spiral form, so that the size of the filter can be reduced, and the integration level of the filter can be increased.
All of the products of the present application need not have all of the effects described above.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic circuit diagram of a conventional multi-section coupled line bandpass filter;
fig. 2 is a schematic circuit diagram of a coupled line bandpass filter according to embodiment 1 of the present application;
fig. 3 is a schematic circuit diagram of a coupled line bandpass filter according to embodiment 2 of the present application;
fig. 4 is a schematic circuit diagram of a coupled line bandpass filter according to embodiment 3 of the present application;
fig. 5 is a schematic circuit diagram of a coupled line bandpass filter according to embodiment 4 of the application.
Fig. 6 is a schematic diagram of a filtering result of the coupled line bandpass filter provided in embodiment 1 of the present application;
fig. 7 is a schematic diagram of a filtering result of the coupled line bandpass filter according to embodiment 2 of the present application;
fig. 8 is a schematic diagram of a filtering result of the coupled line bandpass filter provided in embodiment 3 of the application;
fig. 9 is a schematic diagram of a filtering result of the coupled line bandpass filter provided in embodiment 4 of the application.
Detailed Description
For the purposes of making the objects, technical solutions and advantages of the present application more apparent, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the described embodiments are only some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present disclosure, are within the scope of the present disclosure.
As described in the background art, the implementation of the filter in the prior art is difficult to achieve either at high frequency (frequency is greater than 5 GHz), or the size is difficult to be small, so that high integration is difficult to achieve, and the implementation is deficient in practical application, so that the high requirement of the modern communication system on the filter is difficult to meet.
In view of the above problems, the embodiments of the present application creatively propose a new band-pass filter based on coupled lines, so as to solve the problems of high performance and small size at the same time. The filter at least comprises a microwave input port, a microwave output port, a coupling line unit and an inductance-capacitance unit. The coupling line unit at least comprises a coupling line, two ends of the coupling line unit are respectively connected with a microwave input port and a microwave output port, the other ports of the coupling line unit are grounded, the inductance-capacitance unit is connected with the coupling line unit in parallel, the inductance-capacitance unit comprises an inductance and a capacitance which are mutually connected in series, the bandwidth and the out-of-band suppression of the filter are adjusted by adjusting the Ze and Zo values of the coupling line, the frequency and the in-band matching of the filter are adjusted by adjusting the length of the coupling line and the inductance-capacitance unit, and therefore the problem of small size is solved while the high performance of the filter is simultaneously considered.
Embodiments of the present application will be described in detail below with reference to the accompanying drawings.
Example 1
Fig. 2 is a schematic structural diagram of a coupled line bandpass filter provided in embodiment 1 of the application, and referring to fig. 2, the filter generally includes a microwave input port I2, a microwave output port O2, a coupled line unit 100, and an lc unit 200. Both ends of the coupling line unit 100 are respectively connected with the microwave input port I2 and the microwave output port O2, the other ports of the coupling line unit 100 are grounded, and the inductance-capacitance unit 200 is connected in parallel with the coupling line unit 100.
The coupling line unit 100 in the embodiment of the present application includes one coupling line 110, and the lc unit 200 includes one stage, and preferably, the lc unit 200 includes a first inductor 210 and a first capacitor 220 connected in series with each other. In particular, one end of the first inductor 210 is connected to the microwave input port I2, the other end of the first inductor 210 is connected to one end of the first capacitor 220, and the other end of the first capacitor 220 is connected to the microwave output port O2. The length of the coupled line 110 is equal to a quarter wavelength of the filter in-band operating center frequency.
The coupling line band-pass filter provided in this embodiment of the present application may be applied to a range of 10MHz to 100GHz, and in a specific implementation, the Ze value of the coupling line 110 is 10 to 1000ohm, preferably 30ohm, the zo value is 2 to 100ohm, preferably 4ohm, the length of the coupling line 110 is 0.9 to 40mm, preferably 6.5mm, the size of the first inductor 210 is 0.2 to 10nH, preferably 1.5nH, and the size of the first capacitor 220 is 0.05 to 5pF, preferably 0.5pF. In specific application, the Zes are determined by the widths of the transmission lines (namely the coupling lines), the adjusting line widths influence out-of-band rejection, the Zo is determined by the widths of the coupling lines and the distances between the coupling lines, the distances have a large influence on the Zo, and the Zo influences the bandwidths, so that the bandwidths and the out-of-band rejection of the filter can be adjusted by adjusting the Zes and the Zo values of the coupling lines. Since the length of the coupled line (also called transmission line) is wavelength-dependent, i.e. frequency-dependent, the operating frequency of the filter can be adjusted by adjusting the length of the coupled line. In addition, the in-band matching may be adjusted by adjusting the first inductance and the first electrical connection.
Example two
The difference from the first embodiment is that in the embodiment of the present application, the filter is formed by coupling lines of multiple stages of lc units in parallel, that is, the lc units include N stages, and the coupling line units include N coupling lines connected in series with each other, where N is greater than or equal to 2. Each stage of inductance-capacitance unit is connected with one of the coupling lines in parallel, for example, the nth stage of inductance-capacitance unit is connected with two ends of the nth coupling line in parallel, and n is E [1, N ]. Each stage of the inductance-capacitance unit comprises an inductance and a capacitance which are mutually connected in series, for example, the nth stage of the inductance-capacitance unit comprises an nth inductance and an nth capacitance which are mutually connected in series. The length of the N coupled lines is equal to one quarter wavelength of the in-band operation center frequency of the filter.
In specific implementation, one end of a first inductor in the first-stage inductance-capacitance unit is connected with the microwave input port, the other end of the first inductor is connected with one end of the first capacitor, the other end of the first capacitor is connected with one end of the first coupling line far away from the microwave input port, one end of an nth inductor in the nth-stage inductance-capacitance unit is connected with one end of the nth coupling line far away from the microwave output port, the other end of the nth inductor is connected with one end of the nth capacitor, and the other end of the nth capacitor is connected with the microwave output port. It should be noted that, in the embodiment of the present application, the mode of connecting the multistage lc units in parallel with the coupled lines is used, so that the band-pass filter has better out-of-band rejection without increasing the size, and the performance of the band-pass filter is improved.
In this embodiment, the lc cell is described by taking two stages as an example, and referring to fig. 3, the filter generally includes a microwave input port I3, a microwave output port O3, a coupling line cell 100a, and an lc cell 200a. The coupled line unit 100a includes a first coupled line 110a and a second coupled line 120a connected in series, and the lc unit 200a includes two stages, i.e., a first stage lc unit 200a' and a second stage lc unit 200a″. The first stage lc cell 200a' is connected in parallel with the first coupled line 110a and the second stage lc cell 200a "is connected in parallel with the second coupled line 120 a. One end of the first coupling line 110a is connected to the microwave input port I3, the other end of the first coupling line 110a is connected to one end of the second coupling line 120a, the other end of the second coupling line 120a is connected to the microwave output port O3, and the remaining ports of the first coupling line 110a and the second coupling line 120a are grounded.
In particular, the length of the first coupling line 110a and the second coupling line 120a is equal to a quarter wavelength of the in-band operation center frequency of the filter, the first stage lc cell 200a ' includes a first inductor 210a ' and a first capacitor 220a ' connected in series, and the second stage lc cell 200a "includes a second inductor 210 a" and a second capacitor 220a "connected in series. One end of the first inductor 210a 'is connected to the microwave input port I3, the other end of the first inductor 210a' is connected to one end of the first capacitor 220a ', the other end of the first capacitor 220a' is connected to a junction of the first coupling line 110a and the second coupling line 120a (i.e., one end of the first coupling line 110a away from the microwave input port I3), one end of the second inductor 210a″ is connected to a junction of the second coupling line 120a and the first coupling line 110a (i.e., one end of the second coupling line 120a away from the microwave output port O3), the other end of the second inductor 210a″ is connected to one end of the second capacitor 220a ", and the other end of the second capacitor 220a″ is connected to the microwave output port O3.
The coupling line bandpass filter provided in this embodiment of the present application may be applied to a range of 1GHz to 40GHz, and in a specific implementation, the Ze value of the first coupling line 110a is 10ohm to 1000ohm, preferably 30ohm, the zo value is 2ohm to 100ohm, preferably 4ohm, the length of the first coupling line 110a is 0.9mm to 40mm, preferably 6.5mm, the Ze value of the second coupling line 120a is 10ohm to 1000ohm, preferably 30ohm, the zo value is 2ohm to 100ohm, preferably 12ohm, the length of the second coupling line 120a is 0.9mm to 40mm, preferably 6.5mm, the size of the first inductor 210a 'is 0.2nH to 10nH, preferably 1.5nH, the size of the second inductor 210a "is 0.2nH to 10nH, preferably 1.5nH, the size of the first capacitor 220a' is 0.05pF and preferably 0.5pF and the size of the second capacitor 220 a" is 0.5pF.
In particular applications, as described above with reference to the first and second coupling lines 110a, 120a, the bandwidth and out-of-band rejection of the filter can be adjusted by adjusting the Ze and Zo values of the first and second coupling lines 110a, 120a, the operating frequency of the filter can be adjusted by adjusting the lengths of the first and second coupling lines 110a, 120a, and the in-band matching of the filter can be adjusted by adjusting the first inductance 210a ', the first and second capacitances 220a', 210a ', 220 a'.
Example III
The difference from the first embodiment is that in the embodiment of the present application, the filter is formed by connecting a plurality of coupling lines in parallel with a first-stage inductance-capacitance unit, that is, the inductance-capacitance unit includes a first stage, and the coupling line unit includes M coupling lines connected in series with each other, where M is greater than or equal to 2. The inductance-capacitance unit is connected in parallel with two ends of a coupling line unit formed by M coupling lines which are mutually connected in series. The inductance-capacitance units comprise a first inductance and a first capacitance which are mutually connected in series, and the lengths of the M coupling lines are equal to one quarter wavelength of the in-band working center frequency of the filter.
In specific implementation, one end of a first inductor in the inductance-capacitance unit is connected with the microwave input port, the other end of the first inductor is connected with one end of the first capacitor, and the other end of the first capacitor is connected with the microwave output port. In this embodiment of the present application, the circuit implementation is simpler when the band-pass filter has high performance by using the manner of connecting the lc cells in parallel with the multistage coupled line.
In this embodiment, for example, the coupled line unit includes 2 coupled lines connected in series, and referring to fig. 4, the filter generally includes a microwave input port I4, a microwave output port O4, a coupled line unit 100b, and an lc unit 200b. The coupled line unit 100b includes a first coupled line 110b and a second coupled line 120b connected in series, and the lc unit 200b includes a first inductor 210b and a first capacitor 220b. One end of the first coupling line 110b is connected to the microwave input port I4, the other end of the first coupling line 110b is connected to one end of the second coupling line 120b, the other end of the second coupling line 120b is connected to the microwave output port O4, and the remaining ports of the first coupling line 110b and the second coupling line 120b are grounded.
In practice, the length of the first coupled line 110b and the second coupled line 120b is equal to one quarter wavelength of the in-band operating center frequency of the filter. One end of the first inductor 210b is connected to the microwave input port I4, the other end of the first inductor 210b is connected to one end of the first capacitor 220b, and the other end of the first capacitor 220b is connected to the microwave output port O4.
The coupled line bandpass filter provided in this embodiment of the present application may be applied to a range of 1GHz to 40GHz, and in a specific implementation, the Ze value of the first coupled line 110b is 10ohm to 1000ohm, preferably 30ohm, the zo value is 2ohm to 100ohm, preferably 4ohm, the length of the first coupled line 110b is 0.9mm to 40mm, preferably 6.5mm, the Ze value of the second coupled line 120b is 10ohm to 1000ohm, preferably 30ohm, the zo value is 2ohm to 100ohm, preferably 4ohm, the length of the second coupled line 120b is 0.9mm to 40mm, preferably 6.5mm, and the size of the first inductor 210b is 0.2nH to 10nH, preferably 2.5nH, the size of the first capacitor 220b is 0.05pF to 5pF, preferably 0.3pF.
In particular applications, as described above, in the embodiments of the present application, the bandwidth and the out-of-band rejection of the filter may be adjusted by adjusting the values of Ze and Zo of the first coupling line 110b and the second coupling line 120b, the operating frequency of the filter may be adjusted by adjusting the lengths of the first coupling line 110b and the second coupling line 120b, and the in-band matching of the filter may be adjusted by adjusting the first inductor 210b and the first capacitor 220b.
Example IV
In the embodiment of the present application, referring to fig. 5, the filter generally includes a microwave input port I5, a microwave output port O5, a coupling line unit 100c, an inductance-capacitance unit 200c and a capacitance unit 300, and the inductance-capacitance unit 200c, the capacitance unit 300 and the coupling line unit 100c are connected in parallel. The coupled line unit 100c includes a coupled line 110c, the lc unit 200c includes a first inductor 210c and a first capacitor 220c, and the capacitor unit 300 includes a second capacitor 310. One end of the first inductor 210c is connected to the microwave input port I5, the other end of the first inductor 210c is connected to one end of the first capacitor 220c, the other end of the first capacitor 220c is connected to the microwave output port O5, one end of the second capacitor 310 is connected to the microwave input port I5, the other end is connected to the microwave output port O5, one end of the coupling line 110c is connected to the microwave input port I5, the other end is connected to the microwave output port O5, and the remaining ports of the coupling line 110c are grounded.
Preferably, the length of the coupled line 110c is equal to a quarter wavelength of the in-band operating center frequency of the filter.
It should be noted that, in the embodiment of the present application, by using the manner of parallel connection of the inductance and capacitance units and parallel connection of the coupling lines, the roll-off of the band-pass filter can be improved, so that the band-pass filter has better out-of-band rejection, and the performance of the band-pass filter is improved.
The coupling line band-pass filter provided in this embodiment of the present application may be applied to a range of 1GHz to 40GHz, and in a specific implementation, the Ze value of the coupling line 110c is 10ohm to 1000ohm, preferably 30ohm, the zo value is 2ohm to 100ohm, preferably 4ohm, the length of the coupling line 110c is 0.9mm to 40mm, preferably 6.5mm, the size of the first inductor 210c is 0.2nH to 10nH, preferably the size of the first capacitor 220c of 2nH is 0.05pF to 5pF, preferably the size of the second capacitor 310 of 0.3pF is 0.05pF to 10pF, preferably 0.5pF.
In particular applications, as described above, in the embodiments of the present application, the bandwidth and out-of-band rejection of the filter can be adjusted by adjusting the Ze and Zo values of the coupling line 110c, the operating frequency of the filter can be adjusted by adjusting the length of the coupling line 110c, and the in-band matching of the filter can be adjusted by adjusting the first inductor 210c, the first capacitor 220c, and the second capacitor 310 and the first inductor 210c and the first capacitor 220c form resonance, so as to provide higher roll-off.
The filtering results of the filters provided in the first to fourth embodiments are measured, wherein the parameters of the related components in the first to fourth embodiments are the preferred values. Referring to fig. 6 to 9, it can be seen that the coupled line bandpass filter provided in the first embodiment has better out-of-band rejection at 150MHz of the operating frequency band, which indicates that the coupled line bandpass filter has better roll-off performance out-of-band; compared with the first embodiment, the coupling line band-pass filter provided by the second embodiment has better out-of-band rejection at 150MHz of the working frequency band, which shows that the coupling line band-pass filter has better roll-off performance out-of-band; compared with the first embodiment, the coupling line band-pass filter provided by the third embodiment has the same out-of-band rejection at 150MHz outside the working frequency band (the out-of-band rejection is referenced by-10 dB), which indicates that the filter has simpler circuit structure under the condition of the same performance; compared with the first embodiment, the coupling line band-pass filter provided by the fourth embodiment has the same out-of-band rejection at 100MHz outside the working frequency band (the out-of-band rejection is taken as a reference), which indicates that the roll-off of the filter at high frequency is better, and the coupling line band-pass filter is more suitable for the application situation of the rejection frequency band being very close.
In the description of the present application, it should be understood that the terms "vertical," "parallel," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like indicate an orientation or a positional relationship based on that shown in the drawings, merely for convenience of description and to simplify the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present application. Furthermore, the terms "first," "second," and the like, 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" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present application, unless otherwise indicated, the meaning of "a plurality" is two or more.
In the description of the present application, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the terms in this application will be understood by those of ordinary skill in the art in a specific context.
The foregoing description of the preferred embodiments of the present application is not intended to limit the invention to the particular embodiments of the present application, but to limit the scope of the invention to the particular embodiments of the present application.
Claims (12)
1. The coupling line band-pass filter is characterized by at least comprising a microwave input port, a microwave output port, a coupling line unit and an inductance-capacitance unit, wherein two ends of the coupling line unit are respectively connected with the microwave input port and the microwave output port, the other ports of the coupling line unit are grounded, the inductance-capacitance unit is connected with the coupling line unit in parallel, and the inductance-capacitance unit comprises an inductance and a capacitance which are mutually connected in series.
2. The coupled line bandpass filter according to claim 1, wherein the inductance-capacitance unit comprises a stage, the coupled line unit comprises a coupled line, the inductance-capacitance unit comprises a first inductance and a first capacitance connected in series, one end of the first inductance is connected to the microwave input port, the other end of the first inductance is connected to one end of the first capacitance, and the other end of the first capacitance is connected to the microwave output port.
3. The coupled-line bandpass filter according to claim 2, characterized in that the length of the coupled line is equal to a quarter wavelength of the in-band operating center frequency of the filter.
4. The coupled line bandpass filter according to claim 1, wherein the lc unit comprises N stages, the coupled line unit comprises N coupled lines connected in series, the N-th stage lc unit is connected in parallel to two ends of the N-th coupled line, the N-th stage lc unit comprises N-th inductor and N-th capacitor connected in series, and N is equal to or greater than 2, N e [1, N ].
5. The coupled line bandpass filter according to claim 4, wherein one end of a first inductor in the first stage of the lc unit is connected to the microwave input port, the other end of the first inductor is connected to one end of a first capacitor, the other end of the first capacitor is connected to one end of the first coupled line away from the microwave input port, one end of an nth inductor in the nth stage of the lc unit is connected to one end of the nth coupled line away from the microwave output port, the other end of the nth inductor is connected to one end of the nth capacitor, and the other end of the nth capacitor is connected to the microwave output port.
6. The coupled-line bandpass filter according to claim 5, wherein the length of the N coupled lines is equal to one quarter wavelength of the in-band operating center frequency of the filter.
7. The coupled line bandpass filter according to claim 1, wherein the inductance-capacitance unit comprises a stage, the coupled line unit comprises M coupled lines connected in series, the inductance-capacitance unit is connected in parallel to two ends of the coupled line unit, M is greater than or equal to 2, the inductance-capacitance unit comprises a first inductance and a first capacitance connected in series, one end of the first inductance is connected with the microwave input port, the other end of the first inductance is connected with one end of the first capacitance, and the other end of the first capacitance is connected with the microwave output port.
8. The coupled-line bandpass filter according to claim 7, wherein M of the coupled lines each have a length equal to one quarter wavelength of an in-band operating center frequency of the filter.
9. The coupled line bandpass filter according to claim 1, wherein the filter further comprises a capacitance unit, the coupled line unit comprises a coupled line, the lc unit, the capacitance unit, and the coupled line are connected in parallel, the lc unit comprises a first inductance and a first capacitance connected in series with each other, and the capacitance unit comprises a second capacitance.
10. The coupled line bandpass filter according to claim 9, wherein one end of the first inductor is connected to the microwave input port, the other end of the first inductor is connected to one end of the first capacitor, the other end of the first capacitor is connected to the microwave output port, one end of the second capacitor is connected to the microwave input port, and the other end is connected to the microwave output port.
11. The coupled-line bandpass filter according to claim 10, wherein the length of the coupled line is equal to one quarter wavelength of the in-band operating center frequency of the filter.
12. The coupled line bandpass filter according to any one of claims 1 to 11, characterized in that the coupled line is realized by a strip line in spiral form.
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| CN115799781A (en) | 2023-03-14 |
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