CN116937093B - Broadband reflection-free band-pass filter - Google Patents
Broadband reflection-free band-pass filter Download PDFInfo
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- CN116937093B CN116937093B CN202311188996.9A CN202311188996A CN116937093B CN 116937093 B CN116937093 B CN 116937093B CN 202311188996 A CN202311188996 A CN 202311188996A CN 116937093 B CN116937093 B CN 116937093B
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- 230000005540 biological transmission Effects 0.000 claims abstract description 53
- 230000008878 coupling Effects 0.000 claims abstract description 45
- 238000010168 coupling process Methods 0.000 claims abstract description 45
- 238000005859 coupling reaction Methods 0.000 claims abstract description 45
- 239000002184 metal Substances 0.000 claims abstract description 18
- 229910052751 metal Inorganic materials 0.000 claims abstract description 18
- 239000000758 substrate Substances 0.000 claims abstract description 14
- 238000001465 metallisation Methods 0.000 claims description 8
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 5
- 238000005253 cladding Methods 0.000 claims description 5
- 229910052802 copper Inorganic materials 0.000 claims description 5
- 239000010949 copper Substances 0.000 claims description 5
- 238000010521 absorption reaction Methods 0.000 abstract description 8
- 238000012545 processing Methods 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- 238000004891 communication Methods 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000003780 insertion Methods 0.000 description 2
- 230000037431 insertion Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000010295 mobile communication Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000004088 simulation Methods 0.000 description 2
- 230000002411 adverse Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P1/00—Auxiliary devices
- H01P1/20—Frequency-selective devices, e.g. filters
- H01P1/201—Filters for transverse electromagnetic waves
- H01P1/203—Strip line filters
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Abstract
The invention discloses a novel broadband reflectionless band-pass filter, which belongs to the technical field of microwaves and comprises a dielectric substrate, a metal floor arranged on the lower layer of the dielectric substrate, a microstrip line structure arranged on the upper layer of the dielectric substrate, a metalized through hole and a resistor. The microstrip line structure on the upper layer of the dielectric substrate comprises two sections of quarter-wavelength transmission lines serving as input and output ends, a section of parallel coupling lines arranged between the input and output ends serving as bandpass branches, and two same bandstop branches connected to the input and output ends and having the same left and right structures comprise a section of parallel coupling line with the tail ends connected in parallel and the ends connected in an open-circuited manner, wherein the front ends of the parallel coupling lines are connected with load resistors, and the load resistors are grounded through metallized through holes. The invention realizes the advantages of small return loss, good absorption performance, large relative bandwidth, simple structure, easy realization and low cost in the whole passband of the broadband non-reflection band-pass filter.
Description
Technical Field
The invention belongs to the technical field of microwaves, and particularly relates to a novel broadband reflectionless band-pass filter.
Background
With the continuous development of wireless communication technology, mobile terminal devices are being improved toward the goal of miniaturization and high performance, and the microwave devices constituting the terminal devices are in need of higher demands. The filter is an essential component of the front-end section of the radio frequency microwave and is one of the most important devices. Conventional filters reflect unwanted signals back to the input through the stop band, which may adversely affect the overall system performance. Therefore, the reflectionless filter has been developed, and a lossy filter element is adopted in the reflectionless filter to achieve the purpose of absorbing the stop band signal, so that the stop band signal is consumed in the filter, and the influence on a system is avoided. However, the bandwidth of the current reflectionless filter is narrow, and the absorption of the stopband reflected signal is low, so that the current high-speed development of modern wireless communication cannot be satisfied.
Disclosure of Invention
The technical problems to be solved by the invention are as follows: the novel broadband reflectionless band-pass filter is provided, the bandwidth is increased by cascading one band-pass branch through two band-stop branches, and the load resistance of a grounding metal floor is increased in the band-stop branch structure to absorb unnecessary stop band signals. The reflection-free filter has the advantages of simple structure, large working bandwidth, good absorption performance and easy processing, and has wide application prospect in a radio frequency microwave system.
The invention adopts the following technical scheme for solving the technical problems:
a novel broadband reflectionless band-pass filter comprises an upper microstrip line structure, a dielectric substrate and a lower metal floor which are sequentially arranged from top to bottom.
The microstrip line structure comprises an input transmission line, an output transmission line, a first parallel coupling line, a second parallel coupling line, a third parallel coupling line, two quarter-wavelength transmission lines with open terminals, two load resistors and two metallized through holes.
Further, the microstrip line structure comprises a first band-stop branch and a second band-stop branch, the third parallel coupling line is used as a band-stop branch of the filter and is arranged between the input transmission line and the output transmission line, and the third parallel coupling line is connected with the two band-stop branches with the same left and right structures of the input transmission line.
The first band-stop branch is a quarter-wavelength transmission line with the end connected with a first open-ended circuit, the initial end of one parallel line in the first parallel coupling line is connected with one end of an input transmission line, the initial end of the other parallel line in the first parallel coupling line is connected with one end of a first load resistor, the other end of the first load resistor is connected with one end of a first metallization through hole, and the first metallization through hole is hollowed into a cylinder through the middle and is connected with a metal floor through copper cladding all around to be grounded.
The second band-stop branch is a quarter-wavelength transmission line with the tail end connected with a second open-ended circuit, the initial end of one parallel line in the second parallel coupling line is connected with one end of the output transmission line, the initial end of the other parallel line in the second parallel coupling line is connected with one end of a second load resistor, the other end of the second load resistor is connected with one end of a second metalized through hole, and the second metalized through hole is hollowed into a cylinder through the middle and is connected with a metal floor through copper cladding at the periphery for grounding.
Further, the dielectric substrate has a length in the range of 55-60 mm, a width in the range of 40-45 mm, and a height in the range of 0.5-1.0 mm.
Further, the metal floor has a length in the range of 55-60 mm and a width in the range of 40-45 mm.
Furthermore, the impedance of the input transmission line and the impedance of the output transmission line are both 50 omega, and the impedance of the input transmission line and the impedance of the output transmission line are used as input and output ends of the filter and are used for connecting the filter with the SMA female head, so that the test is convenient.
Further, the third parallel coupled line has a length in the range of 25-35 mm, a width in the range of 0.3-0.6 mm, and a gap in the range of 0.12-0.22 mm.
Further, the first parallel coupled line and the second parallel coupled line have a length in the range of 25-35 mm, a width in the range of 0.3-0.6 mm, and a gap in the range of 1.5-2.5 mm.
Further, the two open-ended quarter wavelength transmission lines have a length in the range of 25-35 mm and a width in the range of 1.5-2.5 mm.
Further, the two load resistors are used as band-stop branches of the filter, and the resistance values of the two load resistors are 59 Ω.
Further, the diameter of the two metallized through holes is 1 millimeter; the microstrip line structure is connected with the metal floor below the dielectric substrate through the first metallization through hole and the second metallization through hole.
Further, the first band-stop branch is connected to the upper end of the third parallel coupling line, the second band-stop branch is connected to the lower end of the third parallel coupling line, and a gap and a line width exist therein, so that the first band-stop branch is higher than the second band-stop branch by 0.67 mm in the y-axis direction for convenience of connection.
Compared with the prior art, the invention adopts the technical proposal and has the following remarkable technical effects:
the invention provides a novel broadband reflectionless band-pass filter, the passband bandwidth is 1.21-2.99 GHz, the relative bandwidth is 71.2%, the return loss passband is 0-5 GHz and is lower than-15 and dB, the filter structure is fully simplified, the manufacturing process is simple, the cost is low, the working bandwidth is large, the absorption performance is good, and the application requirements of the next-generation broadband mobile communication are met.
Drawings
Fig. 1 is a schematic three-dimensional structure of a reflection-free band-pass filter of the present invention.
Fig. 2 is a schematic top view of the reflection-free band-pass filter of the present invention.
Fig. 3 is a schematic circuit diagram of a reflection-free band-pass filter according to the present invention.
FIG. 4 shows the bandpass branches of the reflection-free bandpass filter according to the invention at different coupling coefficients k 12 In the case of the bandpass branch input impedance Z in1 Is a graph of the variation of (a).
FIG. 5 shows the bandpass branches of the reflectionless bandpass filter of the invention at different Z 5 In the case of the band-reject branch input impedance Z in2 Is a graph of the variation of (a).
FIG. 6 shows the bandpass branches of the reflection-free bandpass filter of the invention at different coupling coefficients k 34 The band-pass branch input impedance Z in2 Is a graph of the variation of (a).
FIG. 7 shows the input impedance Z after matching of the reflection-free band-pass filter of the present invention in Is a graph of the variation of (a).
Fig. 8 is a graph of S11 parameters calculated by HFSS software for a reflection-free bandpass filter according to an embodiment of the invention.
Fig. 9 is a graph of S21 parameters calculated by HFSS software for a reflection-free bandpass filter according to an embodiment of the invention.
FIG. 10 is a graph comparing S11 and S21 parameters calculated using HFSS software with actual processing tests of a reflectionless bandpass filter according to an embodiment of the present invention.
Description of the embodiments
The invention is further described below with reference to the accompanying drawings. The following examples are only for more clearly illustrating the technical aspects of the present invention, and are not intended to limit the scope of the present invention.
It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
The invention provides a novel broadband reflectionless band-pass filter, which comprises a microstrip line structure 1, a dielectric substrate 2 and a metal floor 3 which are sequentially arranged from top to bottom as shown in figures 1 and 2.
In this example, the dielectric substrate 2 used was rogers 5880, which had a dielectric constant of 2.2, a loss tangent of 0.0009, and a substrate thickness of 0.8 mm. The thickness of the microstrip line structure 1 and the metal floor 3 is 0.0175 mm.
The microstrip line structure 1 comprises an input transmission line 4, an output transmission line 4', a third parallel coupled line 5, a first parallel coupled line 6, a second parallel coupled line 6', a first open ended quarter wavelength transmission line 7, a second open ended quarter wavelength transmission line 7', a first load resistor 8, a second load resistor 8', a first metallized via 9 and a second metallized via 9'.
The upper microstrip line structure 1 comprises a first band-stop branch and a second band-stop branch, the third parallel coupling line 5 is used as a band-stop branch of the filter and is arranged between the input transmission line 4 and the output transmission line 4', and the third parallel coupling line is connected with the two band-stop branches with the same left and right structures of the input transmission line.
The first band-stop branch is a quarter-wavelength transmission line 7 with the end connected with a first open-ended circuit, the initial end of one parallel line in the first parallel coupling line 6 is connected with one end of the input transmission line 4, the initial end of the other parallel line in the first parallel coupling line 6 is connected with one end of a first load resistor 8, the other end of the first load resistor 8 is connected with one end of a first metallization through hole 9, and the first metallization through hole 9 is hollowed into a cylinder through the middle and is connected with the metal floor 3 through copper cladding at the periphery for grounding.
The second band-stop branch is a quarter-wavelength transmission line 7 'with the end connected with a second open-ended circuit, the initial end of one parallel line in the second parallel coupling line 6' is connected with one end of an output transmission line 4', the initial end of the other parallel line in the second parallel coupling line 6' is connected with one end of a second load resistor 8', the other end of the second load resistor 8' is connected with one end of a second metalized through hole 9', and the second metalized through hole 9' is hollowed into a cylinder through the middle and is connected with the metal floor 3 through copper cladding at the periphery for grounding.
The first band-stop branch and the second band-stop branch have the same structure but are asymmetric, and the first band-stop branch is 0.67 mm higher than the second band-stop branch in the y-axis direction.
The length of the input transmission line 4 and the length of the output transmission line 4' are 27.3 mm, the width is 2.4 mm, the impedance is 50 omega, and the input transmission line and the output transmission line are used as input and output ends of the filter and are used for connecting the filter with the SMA female head, so that the test is convenient.
The third parallel coupled line 5 has a length in the range of 25-35 mm, a width in the range of 0.3-0.6 mm and a gap of 0.16 mm.
The first parallel coupled line 6 and the second parallel coupled line 6' have a length in the range of 25-35 mm, a width in the range of 0.3-0.6 mm, and a gap of 2.16 mm.
The first open ended quarter wave transmission line 7 and the second open ended quarter wave transmission line 7' are 28.97 mm in length and 1.53 mm in width.
The first load resistor 8 and the second load resistor 8' are used as band-stop branches of the filter, and the resistance values of the first load resistor and the second load resistor are 59 omega.
The first metallized via 9 and the second metallized via 9' have a diameter of 1 millimeter; the microstrip line structure 1 is connected to the metal floor 3 through a first metallized via 9 and a second metallized via 9'.
As shown in the circuit diagram of fig. 3, the port impedance Z 0 =50Ω, all electrical lengths θ=90°. The reflectionless band-pass filter can be divided into two parts, one is a section of parallel coupling transmission line Z 1 、Z 2 The other band-pass branch is a band-stop branch with identical left and right structures. The band-stop branch in FIG. 3 is formed by a section of parallel coupled transmission line Z 3 、Z 4 Quarter-wavelength transmission line Z with end parallel and open-ended 5 The other end terminal is grounded and has an absorption load resistor with the impedance of 59 omega.
For the bandpass branch portion, the input impedance Zin1 is determined by the coupling coefficient k between parallel coupled lines 12 Determined, FIG. 4 shows the coupling coefficient k of parallel coupled lines 12 The relation with the input impedance Zin1 which varies with frequency when the coupling coefficient k 12 When the coupling coefficient k is larger than-6.6 or smaller than-6.6, the out-of-band matching change is small but the in-band matching is poor, and finally the coupling coefficient k of the parallel coupling lines is selected 12 Is-6.6.
For the band-reject leg section, the input impedance Zin2 is determined by the coupling coefficient k between parallel coupled lines 34 And impedance Z 5 Determined, FIG. 5 shows the different impedances Z 5 With the input impedance Zin2, Z can be seen 5 Out-of-band matching becomes better but in-band bandwidth becomes narrower at greater than 50Ω, whereas Z is the opposite 5 Out-of-band matching at less than 50Ω degrades absorption performance but widens bandwidth, thereby determining the impedance Z of the open ended quarter wavelength transmission line 5 50 omega, in determining the transmission line impedance Z 5 In the case of (a), fig. 6 shows the coupling coefficient k of different parallel coupled lines 34 As a function of frequency, as a function of the coupling coefficient k, with the input impedance Zin2 34 When the coupling coefficient k is larger than-21.5 or smaller than-21.5, the out-of-band matching variation is small but the in-band matching is poor, and finally the coupling coefficient k of the parallel coupling lines is selected 34 Is-21.5.
FIG. 7 shows the overall input impedance Z after the band-pass branch and the band-stop branch are connected in parallel in The relation to the frequency variation can be seen as the input impedance Z in The impedance matching is good as the frequency varies up and down at 50Ω.
Fig. 8 shows the return loss S11 of the reflection-free band-pass filter of the present embodiment calculated by HFSS software, and it can be seen from the figure that the S11 passband of the present invention is lower than-15 dB at 0-5 GHz, the passband is wide, the in-band return loss can be small, the absorption performance is good, and the reflection-free purpose is satisfied.
Fig. 9 shows the insertion loss S21 of the reflection-free band-pass filter of this embodiment calculated by HFSS software, and it can be seen from the figure that the passband bandwidth of-3 dB of the present invention is 1.21-2.99 GHz, the relative bandwidth fbw=71.2%, and the relative bandwidth is large, so as to meet the design requirement of the filter.
In fig. 10, after a real object is processed, the return loss and the insertion loss of the real object of the reflectionless band-pass filter are measured by using a vector network analyzer, and compared with data obtained by calculation of HFSS software, the passband bandwidth of the real object is 1.24-2.93 GHz, the relative bandwidth FBW=67.6%, the return loss S11 is lower than-11 dB in the passband frequency of 0-5 GHz, and the real object is matched with a simulation result graph, wherein the errors comprise the processing loss, the measurement error and the vacuum medium, the air medium in the simulation, and the vacuum medium and the air medium are in the error range.
In conclusion, the novel broadband reflectionless band-pass filter provided by the invention has the advantages of simple manufacturing process, low cost, large working bandwidth and good absorption performance, and can meet the application requirements of the broadband mobile communication of the new generation.
While embodiments of the present invention have been shown and described, it will be understood that the above embodiments are illustrative and not to be construed as limiting the invention, and that variations, modifications, alternatives, and variations may be made to the above embodiments by one of ordinary skill in the art within the scope of the invention. Any other corresponding changes and modifications made in accordance with the technical idea of the present invention shall be included in the scope of the claims of the present invention.
Claims (10)
1. The broadband reflectionless band-pass filter comprises a microstrip line structure (1), a dielectric substrate (2) and a metal floor (3), wherein the microstrip line structure (1) is arranged on the upper layer of the dielectric substrate (2), and the metal floor (3) is arranged on the lower layer of the dielectric substrate (2), and is characterized in that the microstrip line structure (1) comprises an input transmission line (4), an output transmission line (4 '), a third parallel coupling line (5), a first parallel coupling line (6), a second parallel coupling line (6'), a first open-ended quarter-wavelength transmission line (7), a second open-ended quarter-wavelength transmission line (7 '), a first load resistor (8'), a second load resistor (8 '), a first metalized through hole (9) and a second metalized through hole (9');
the microstrip line structure (1) comprises a first band-stop branch and a second band-stop branch, the third parallel coupling line (5) is used as a band-pass branch of the filter and is arranged between the input transmission line (4) and the output transmission line (4') so as to connect the two band-stop branches with the same left and right structures of the input transmission line;
the first band-stop branch is a quarter-wavelength transmission line (7) with the tail end of the first parallel coupling line (6) connected with a first open-ended circuit, the initial end of one parallel line in the first parallel coupling line (6) is connected with one end of the input transmission line (4), the initial end of the other parallel line in the first parallel coupling line (6) is connected with one end of a first load resistor (8), the other end of the first load resistor (8) is connected with one end of a first metallization through hole (9), and the first metallization through hole (9) is hollowed into a cylinder through the middle and is connected with a metal floor (3) by copper-clad all around for grounding;
the second band-stop branch is a quarter-wavelength transmission line (7 ') with the end connected with a second open-ended circuit, the initial end of one parallel line in the second parallel coupling line (6') is connected with one end of an output transmission line (4 '), the initial end of the other parallel line in the second parallel coupling line (6') is connected with one end of a second load resistor (8 '), the other end of the second load resistor (8') is connected with one end of a second metalized through hole (9 '), and the second metalized through hole (9') is hollowed into a cylinder through the middle and is connected with a metal floor (3) by copper cladding all around to be grounded.
2. The broadband reflectionless bandpass filter according to claim 1, wherein the first band reject branch is identical in structure to the second band reject branch but asymmetric, the first band reject branch being 0.67 mm higher than the second band reject branch in the y-axis direction.
3. Broadband reflectionless bandpass filter according to claim 1, characterized in that the dielectric substrate (2) has a length in the range of 55-60 mm, a width in the range of 40-45 mm and a height in the range of 0.5-1.0 mm.
4. Broadband reflectionless bandpass filter according to claim 1, characterized in that the metal floor (3) has a length in the range of 55-60 mm and a width in the range of 40-45 mm.
5. Broadband reflectionless bandpass filter according to claim 1, characterized in that the input transmission line (4) and the output transmission line (4') have an impedance of 50 Ω.
6. Broadband reflectionless bandpass filter according to claim 1, characterized in that the third parallel coupling line (5) has a length in the range of 25-35 mm, a width in the range of 0.3-0.6 mm and a gap in the range of 0.12-0.22 mm.
7. Broadband reflectionless bandpass filter according to claim 1, characterized in that the first parallel-coupled line (6) and the second parallel-coupled line (6') have a length in the range of 25-35 mm, a width in the range of 0.3-0.6 mm and a gap in the range of 1.5-2.5 mm.
8. Broadband reflectionless bandpass filter according to claim 1, characterized in that the first open-ended quarter-wavelength transmission line (7) and the second open-ended quarter-wavelength transmission line (7') have a length in the range of 25-35 mm and a width in the range of 1.5-2.5 mm.
9. Broadband reflectionless bandpass filter according to claim 1, characterized in that the first load resistor (8) and the second load resistor (8') are used as bandstop branches of the filter, which have a resistance of 59 Ω.
10. Broadband reflectionless bandpass filter according to claim 1, characterized in that the first metallized through hole (9) and the second metallized through hole (9') have a diameter of 1 mm; the microstrip line structure (1) is connected with the metal floor (3) through a first metallized through hole (9) and a second metallized through hole (9').
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| CN202311188996.9A CN116937093B (en) | 2023-09-15 | 2023-09-15 | Broadband reflection-free band-pass filter |
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| CN202311188996.9A CN116937093B (en) | 2023-09-15 | 2023-09-15 | Broadband reflection-free band-pass filter |
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