A triple-band active switchable bandpass filter for S, C, and X bands

Abstract

The present invention discloses an S, C, X triple-band active switchable band-pass filter, comprising: a first-layer metal floor part, a first-layer dielectric substrate part, a second-layer metal floor part, a second-layer dielectric substrate part, a third-layer metal floor part, a third-layer dielectric substrate part, a fourth-layer metal floor part, a fourth-layer dielectric substrate part, a fifth-layer metal floor part, a fifth-layer dielectric substrate part, and a low-pass stepped impedance line part stacked in sequence. The present invention designs the filters for each frequency band separately, performs frequency band switching through the PIN diodes on the topmost layer and the frequency selection path, and realizes the on and off of the PIN diodes through the DC bias circuit to achieve the frequency selection function of a certain frequency band.

Description

Technical Field

[0001] The present invention relates to the technical field of active tunable filters, and particularly to an S, C, X triple-band active switchable band-pass filter. Background Art

[0002] With the vigorous development of wireless communication technology and integrated circuit technology, there is an urgent need for high-performance, multi-band and compact-sized band-pass filters. The use of active tunable units enables the filter to have more flexible frequency selectivity. At the same time, the interdigital resonant structure has the characteristics of small size, low return loss and fast roll-off speed, which is suitable for the high integration requirements of modern integrated circuits. Combining the DC electronic control unit with the filter can achieve the purpose of adjusting indicators such as the operating frequency and bandwidth of the filter.

[0003] The PIN diode has the characteristics of conducting under forward voltage and cutting off under reverse voltage. It can achieve the switching of circuit on and off by changing the bias voltage, so as to adjust characteristics such as the equivalent electrical size and state of the microwave structure.

[0004] The interdigital filter is composed of quasi-TEM mode microstrip line resonators placed in parallel. The length of each resonator is a quarter wavelength. One end of the resonator is short-circuited and the other end is open-circuited. Coupling is achieved through the field edges between adjacent resonant elements, thus realizing the band-pass effect. At the same time, the filter of this structure usually uses the method of tapped input and output for feeding. In 1962, G. L. Matthaei et al. first proposed the design method and circuit theory of the microstrip interdigital band-pass filter in the article "Interdigital Band-Pass Filters" (IRE Transactions on Microwave Theory and Techniques, vol. 10, no. 6, pp. 479-491, November 1962), providing ideas for the design of interdigital filters in various frequency bands; in 2012, King Yuk Chan et al. proposed an adjustable microstrip interdigital filter in the article "RF MEMS Switchable Interdigital Bandpass Filter" (IEEE Microwave and Wireless Components Letters, vol. 22, no. 1, pp. 44-46, Jan. 2012), realizing the switching of frequency bands by adjusting the coupling between the resonator and the load structure using MEMS switches. However, the cost of using MEMS switches in this structure is relatively high, and the open microstrip structure leads to excessive insertion loss. In 2010, Alexander Miller et al. proposed a method of changing the bandwidth by using PIN diodes to change the length of the stub in the article "Wideband Bandpass Filter With Reconfigurable Bandwidth" (IEEE Microwave and Wireless Components Letters, vol. 22, no. 1, pp. 28-30, Jan. 2010). However, due to the influence of the parasitic capacitance / inductance generated by the introduction of diodes, the adjustable frequency band range and bandwidth of this type of active filter are relatively narrow. With the rapid development of integrated circuits, there is an urgent need for a miniaturized active band-pass filter with a large range, wide band, high performance, easy adjustment, and low cost. This field has become a hot and difficult point in current research. Summary of the Invention

[0005] To solve the problems existing in the above-mentioned prior art, the present invention provides an S, C, and X-band active switchable band-pass filter.

[0006] To achieve the above technical objectives, the present invention adopts the following technical solutions:

[0007] An S, C, X three-band active switchable bandpass filter, comprising: a first-layer metal floor part, a first-layer dielectric substrate part, a second-layer metal floor part, a second-layer dielectric substrate part, a third-layer metal floor part, a third-layer dielectric substrate part, a fourth-layer metal floor part, a fourth-layer dielectric substrate part, a fifth-layer metal floor part, a fifth-layer dielectric substrate part, and a low-pass stepped impedance line part stacked in sequence.

[0008] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0009] The high-performance S, C, X three-band active switchable bandpass filter of the present invention designs each band filter separately, performs band switching through the top PIN diodes and the frequency selection path, and realizes the on and off of the PIN diodes through the DC bias circuit to achieve the frequency selection function of a certain band; each band adopts a 7th-order closed interdigital filter structure, which is composed of 7 quarter-wavelength resonators with one end short-circuited and the other end open-circuited. 3 pairs of resonators are symmetric with each other about the central resonator. The closed interdigital structure is composed of the middle filtering metal layer, the upper and lower floor layers, the upper and lower dielectric substrate layers, and the metal vias connecting the upper and lower floor layers; in order to suppress the harmonic resonance phenomenon generated by the S band at 8-10 GHz, a stepped impedance line structure with a cut-off frequency of 4 GHz is combined with the S band; in order to obtain a compact size, a stacked design and a vertical feeding design are adopted as a whole, and vias and through holes are used to connect the feeding part and the filtering part, and the bandpass part and the low-pass part. At the same time, by adjusting the feeding aperture size and the metal floor opening size, the parasitic inductance and parasitic capacitance effects generated by the metal vias are reduced, and excellent filtering performance is achieved. Compared with the traditional active adjustable structure, this filter can realize multi-band switching, is easy to tune, and has the characteristics of compact size, excellent performance, and low processing cost. Description of the Drawings

[0010] In order to more clearly illustrate the technical solutions of the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0011] Figure 1 Schematic diagram of the first-layer metal floor part, the first-layer dielectric substrate part, and the second-layer metal floor part.

[0012] Figure 2 Schematic diagram of the second-layer dielectric substrate part, the third-layer metal floor part, and the third-layer dielectric substrate part.

[0013] Figure 3Schematic diagram of the fourth-layer metal floor part, the fourth-layer dielectric substrate part, and the fifth-layer metal floor part.

[0014] Figure 4 Schematic diagram of the fifth-layer dielectric substrate part and the low-pass stepped impedance line part.

[0015] Figure 5 Schematic diagram of the S, C, and X-band active switchable band-pass filter structure.

[0016] Figure 6 Top view of the first-layer metal floor part.

[0017] Figure 7 Top view of the first-layer dielectric substrate part.

[0018] Figure 8 Top view of the second-layer metal floor part.

[0019] Figure 9 Top view of the second-layer dielectric substrate part.

[0020] Figure 10 Top view of the third-layer metal floor part.

[0021] Figure 11 Top view of the third-layer dielectric substrate part.

[0022] Figure 12 Top view of the fourth-layer metal floor part.

[0023] Figure 13 Top view of the fourth-layer dielectric substrate part.

[0024] Figure 14 Top view of the fifth-layer metal floor part.

[0025] Figure 15 Top view of the fifth-layer dielectric substrate part.

[0026] Figure 16 Top view of the fifth-layer dielectric substrate part.

[0027] Figure 17 Schematic diagram of the dimensions of the first-layer metal floor part.

[0028] Figure 18 Schematic diagram of the dimensions of the second-layer metal floor part.

[0029] Figure 19 Schematic diagram of the dimensions of the fourth-layer metal floor part.

[0030] Figure 20 Schematic diagram of the dimensions of the low-pass stepped impedance line part.

[0031] Figure 21Simulation S parameter diagram of the S, C, and X band active switchable bandpass filter. The abscissa represents frequency, and the ordinate represents the S parameter, with the unit of dB. 21 The abscissa represents frequency, and the ordinate represents the S parameter, with the unit of dB.

[0032] Figure 22 Simulation S parameter diagram of the S, C, and X band active switchable bandpass filter. 11 The abscissa represents frequency, and the ordinate represents the S parameter, with the unit of dB.

[0033] In the figure: 1. X-band DC bias pad; 1-1. X-band tapped input / output section; 1-2. X-band interdigital metal resonator section; 1-2-1. First X-band resonator; 1-2-2. Second X-band resonator; 1-2-3. Third X-band resonator; 1-2-4. Fourth X-band resonator; 1-2-5. Fifth X-band resonator; 1-2-6. Sixth X-band resonator; 1-2-7. Seventh X-band resonator; 2. C-band DC bias pad; 2-1. C-band tapped input / output section; 2-2. C-band interdigital metal resonator section; 2-2-1. First C-band resonator; 2-2-2. Second C-band resonator; 2-2-3. Third C-band resonator; 2-2-4. Fourth C-band resonator; 2-2-5. Fifth C-band resonator; 2-2-6. Sixth C-band resonator; 2-2-7. Seventh C-band resonator; 3. S-band DC bias pad; 3-1. S-band tapped input / output section; 3-2. S-band interdigital metal resonator section; 3-2-1. First S-band resonator; 3-2-2. Second S-band resonator; 3-2-3. Third S-band resonator; 3-2-4. Fourth S-band resonator; 3-2-5. Fifth S-band resonator; 3-2-6. Sixth S-band resonator; 3-2-7. Seventh S-band resonator; 4. Second-layer metal floor section; 5. First-layer metal floor section; 6. First-layer dielectric substrate section; 7. Second-layer dielectric substrate section; 8. Third-layer metal floor section; 9. Third-layer dielectric substrate section; 10. Fourth-layer metal floor section; 11. Fourth-layer dielectric substrate section; 12. Fifth-layer metal floor section; 13. Fifth-layer dielectric substrate section; 14. X-band feed metal via; 15. C-band feed metal via; 16. First S-band feed metal via; 17. C- and X-band ground metal via; 18-1. S-band frequency selection path; 18-2. X-band frequency selection path; 18-3. C-band frequency selection path; 19. DC bias pad; 19-1. S-band frequency selection PIN diode; 19-2. X-band frequency selection PIN diode; 19-3. C-band frequency selection PIN diode; 20-1. S-band inductor; 20-2. Input / output microstrip line DC bias inductor; 20-3. C-band inductor; 20-4. X-band inductor; 21. Second S-band feed metal via; 22. S-band ground metal via; 23. Multi-layer metal ground plane connection via; 24. Signal input / output terminal; 25. Low-pass stepped impedance line section; 25-1. First outer 20-ohm low-impedance line; 25-2. Upper left 100-ohm high-impedance line; 25-3. First inner 20-ohm low-impedance line; 25-4. Upper right 100-ohm high-impedance line; 25-5. Lower right 100-ohm high-impedance line; 25-6. Upper port of the stepped impedance line; 25-7. Lower port of the stepped impedance line; 25-8. Low-pass stepped impedance line same-layer metal floor25-9. Step impedance line and in-layer transmission microstrip line; 25-10. Second inner 20-ohm low impedance line; 25-11. Second outer 20-ohm low impedance line; 26. Circular slotted part; 27. S-band third-layer metal floor grounding via hole; 28. Middle metal plate; Detailed implementation manner

[0034] The following further describes the detailed implementation manner of the present invention with reference to the accompanying drawings.

[0035] As Figures 1 - 20 shown, an S, C, X triple-band active switchable bandpass filter includes: a first-layer metal floor part 5, a first-layer dielectric substrate part 6, a second-layer metal floor part 4, a second-layer dielectric substrate part 7, a third-layer metal floor part 8, a third-layer dielectric substrate part 9, a fourth-layer metal floor part 10, a fourth-layer dielectric substrate part 11, a fifth-layer metal floor part 12, a fifth-layer dielectric substrate part 13, and a low-pass step impedance line part 25 stacked in sequence. The thicknesses of the first-layer metal floor part 5, the second-layer metal floor part 4, the third-layer metal floor part 8, the fourth-layer metal floor part 10, the fifth-layer metal floor part 12, and the low-pass step impedance line part 25 are 0.035 mm; the thicknesses of the first-layer dielectric substrate part 6, the second-layer dielectric substrate part 7, the third-layer dielectric substrate part 9, the fourth-layer dielectric substrate part 11, and the fifth-layer dielectric substrate part 13 are 0.3 mm, the relative dielectric constant is 3.55, and the loss tangent is 0.0025.

[0036] The bandpass filter includes an X-band bandpass filtering unit. The X-band bandpass filtering unit includes an X-band DC bias pad 1 on the first-layer metal floor part 5, an X-band frequency selection path 18-2, an X-band frequency selection PIN diode 19-2, an X-band inductor 20-4, and an input / output microstrip line DC bias inductor 20-2; the left side of the X-band frequency selection path 18-2 is connected to the X-band DC bias pad 1 through the X-band inductor 20-4; the bottom side of the X-band frequency selection path 18-2 is connected to the signal input / output terminal 24 through the X-band frequency selection PIN diode 19-2; the right side of the signal input / output terminal 24 is connected to the DC bias pad 19 through the input / output microstrip line DC bias inductor 20-2;

[0037] The X-band bandpass filtering unit includes an X-band tapped input / output section 1-1 and an X-band interdigital metal resonator section 1-2 located on the second-layer metal floor portion 4; the X-band interdigital metal resonator section 1-2 includes a first X-band resonator 1-2-1, a second X-band resonator 1-2-2, a third X-band resonator 1-2-3, a fourth X-band resonator 1-2-4, a fifth X-band resonator 1-2-5, a sixth X-band resonator 1-2-6, and a seventh X-band resonator 1-2-7; two X-band tapped input / output sections 1-1 are respectively located above the first X-band resonator 1-2-1 and below the seventh X-band resonator 1-2-7; the first X-band resonator 1-2-1 and the seventh X-band resonator 1-2-7 are symmetric about the fourth X-band resonator 1-2-4; the second X-band resonator 1-2-2 and the sixth X-band resonator 1-2-6 are symmetric about the fourth X-band resonator 1-2-4; the third X-band resonator 1-2-3 and the fifth X-band resonator 1-2-5 are symmetric about the fourth X-band resonator 1-2-4; the left sides of the first X-band resonator 1-2-1, the third X-band resonator 1-2-3, the fifth X-band resonator 1-2-5, and the seventh X-band resonator 1-2-7 are open-circuited and the right sides are short-circuited; the left sides of the second X-band resonator 1-2-2, the fourth X-band resonator 1-2-4, and the sixth X-band resonator 1-2-6 are short-circuited and the right sides are open-circuited;

[0038] The X-band bandpass filtering unit includes an X-band feeding metal via 14, and the X-band feeding metal via 14 is located on the X-band frequency-selective path 18-2 and on the X-band tapped input / output section 1-1, and sequentially penetrates through the first-layer metal floor portion 5, the first-layer dielectric substrate portion 6, and the second-layer metal floor portion 4;

[0039] The X-band bandpass filtering unit includes a C and X-band grounding metal via 17, and the C and X-band grounding metal via 17 is located on the middle metal plate 28 in the middle of the first-layer metal floor portion 5 and sequentially penetrates through the first-layer metal floor portion 5, the first-layer dielectric substrate portion 6, the second-layer metal floor portion 4, the second-layer dielectric substrate portion 7, and the third-layer metal floor portion 8;

[0040] The C and X-band grounding metal via 17 includes a plurality of vias located on the left side of the middle metal plate 28, a plurality of vias distributed in an I shape located in the middle of the metal plate 28, and a plurality of vias located on the right side of the middle metal plate 28.

[0041] The bandpass filter includes a C-band bandpass filtering unit, and the C-band bandpass filtering unit includes a C-band DC bias pad 2, a C-band frequency-selective path 18-3, a C-band frequency-selective PIN diode 19-3, and a C-band inductor 20-3 on the first-layer metal floor portion 5;

[0042] The right side of the C-band frequency-selective path 18-3 is connected to the C-band DC bias pad 2 through the C-band inductor 20-3; the left side of the C-band frequency-selective path 18-3 is connected to the signal input / output terminal 24 through the C-band frequency-selective PIN diode 19-3;

[0043] The C-band bandpass filter unit includes a C-band tapped input / output part 2-1 and a C-band interdigital metal resonator part 2-2 located on the second-layer metal floor part 4; the C-band interdigital metal resonator part 2-2 includes a first C-band resonator 2-2-1, a second C-band resonator 2-2-2, a third C-band resonator 2-2-3, a fourth C-band resonator 2-2-4, a fifth C-band resonator 2-2-5, a sixth C-band resonator 2-2-6, and a seventh C-band resonator 2-2-7; two C-band tapped input / output parts 2-1 are respectively located above the first C-band resonator 2-2-1 and below the seventh C-band resonator 2-2-7; the first C-band resonator 2-2-1 and the seventh C-band resonator 2-2-7 are symmetric about the fourth C-band resonator 2-2-4; the second C-band resonator 2-2-2 and the sixth C-band resonator 2-2-6 are symmetric about the fourth C-band resonator 2-2-4; the third C-band resonator 2-2-3 and the fifth C-band resonator 2-2-5 are symmetric about the fourth C-band resonator 2-2-4; the left sides of the first C-band resonator 2-2-1, the third C-band resonator 2-2-3, the fifth C-band resonator 2-2-5, and the seventh C-band resonator 2-2-7 are open and the right sides are shorted; the left sides of the second C-band resonator 2-2-2, the fourth C-band resonator 2-2-4, and the sixth C-band resonator 2-2-6 are shorted and the right sides are open;

[0044] The C-band bandpass filter unit includes a C-band feed-through metal via 15, which is located on the C-band frequency-selective path 18-3 and on the C-band tapped input / output part 2-1, and sequentially penetrates the first-layer metal floor part 5, the first-layer dielectric substrate part 6, and the second-layer metal floor part 4.

[0045] The bandpass filter includes an S-band bandpass filter unit, and the S-band bandpass filter unit includes an S-band DC bias pad 3, an S-band frequency-selective path 18-1, an S-band frequency-selective PIN diode 19-1, and an S-band inductor 20-1 on the first-layer metal floor part 5;

[0046] The upper side of the S-band frequency-selective path 18-1 is connected to the S-band DC bias pad 3 through the S-band inductor 20-1; the right side of the S-band frequency-selective path 18-1 is connected to the signal input / output terminal 24 through the S-band frequency-selective PIN diode 19-1;

[0047] The S-band bandpass filtering unit includes an S-band tapped input / output part 3-1 and an S-band interdigital metal resonator part 3-2 located on the fourth-layer metal floor part 10; the S-band interdigital metal resonator part 3-2 includes a first S-band resonator 3-2-1, a second S-band resonator 3-2-2, a third S-band resonator 3-2-3, a fourth S-band resonator 3-2-4, a fifth S-band resonator 3-2-5, a sixth S-band resonator 3-2-6, and a seventh S-band resonator 3-2-7; two S-band tapped input / output parts 3-1 are respectively located above the first S-band resonator 3-2-1 and below the seventh S-band resonator 3-2-7; the first S-band resonator 3-2-1 and the seventh S-band resonator 3-2-7 are symmetric about the fourth S-band resonator 3-2-4; the second S-band resonator 3-2-2 and the sixth S-band resonator 3-2-6 are symmetric about the fourth S-band resonator 3-2-4; the third S-band resonator 3-2-3 and the fifth S-band resonator 3-2-5 are symmetric about the fourth S-band resonator 3-2-4; the left sides of the first S-band resonator 3-2-1, the third S-band resonator 3-2-3, the fifth S-band resonator 3-2-5, and the seventh S-band resonator 3-2-7 are open-circuited and the right sides are short-circuited; the left sides of the second S-band resonator 3-2-2, the fourth S-band resonator 3-2-4, and the sixth S-band resonator 3-2-6 are short-circuited and the right sides are open-circuited;

[0048] The S-band bandpass filtering unit includes a plurality of multi-layer metal ground plane connection vias 23 located on the first-layer metal floor part 5; the multi-layer metal ground plane connection vias 23 sequentially penetrate through the first-layer metal floor part 5, the first-layer dielectric substrate part 6, the second-layer metal floor part 4, the second-layer dielectric substrate part 7, the third-layer metal floor part 8, the third-layer dielectric substrate part 9, the fourth-layer metal floor part 10, the fourth-layer dielectric substrate part 11, the fifth-layer metal floor part 12, the fifth-layer dielectric substrate part 13, and the low-pass stepped impedance line part 25; a low-pass stepped impedance line same-layer metal floor 25-8 is provided outside the multi-layer metal ground plane connection vias 23 on the first-layer metal floor part 5 and the low-pass stepped impedance line part 25;

[0049] The S-band bandpass filter unit comprises a first S-band feeding metal through hole 16, which is located on the S-band frequency selection path 18-1 and sequentially penetrates the first metal floor portion 5, the first dielectric substrate portion 6, the second metal floor portion 4, the second dielectric substrate portion 7, the third metal floor portion 8, the third dielectric substrate portion 9, the fourth metal floor portion 10, the fourth dielectric substrate portion 11, the fifth metal floor portion 12, the fifth dielectric substrate portion 13 and the low-pass step impedance line portion 25; the outer sides of the first S-band feeding metal through hole 16 on the second metal floor portion 4, the third metal floor portion 8, the fourth metal floor portion 10 and the fifth metal floor portion 12 are respectively provided with circular slotted portions 26;

[0050] The S-band bandpass filter unit includes a second S-band feeding metal through hole 21, which is located on the S-band tap input and output part 3-1 and sequentially penetrates the fourth metal floor part 10, the fourth dielectric substrate part 11, the fifth metal floor part 12, the fifth dielectric substrate part 13 and the low-pass step impedance line part 25; a circular slot part 26 is provided on the outer side of the second S-band feeding metal through hole 21 on the fifth metal floor part 12;

[0051] The S-band bandpass filter unit includes an S-band third-layer metal floor grounding through hole 27 located on the third-layer metal floor portion 8, and the S-band third-layer metal floor grounding through hole 27 includes a plurality of through holes located on the left side of the C- and X-band grounding metal through holes 17 and a plurality of through holes located on the right side of the plurality of through holes distributed in an I-shape;

[0052] The S-band bandpass filter unit includes a plurality of S-band grounding metal through holes 22 that sequentially penetrate the third dielectric substrate portion 9, the fourth metal floor portion 10, the fourth dielectric substrate portion 11, and the fifth metal floor portion 12, and the plurality of S-band grounding metal through holes 22 are respectively located around the S-band interdigital metal resonator portion 3-2;

[0053] The S-band bandpass filter unit includes a step impedance upper port 25-6, a first outer 20-ohm low impedance line 25-1, an upper left 100-ohm high impedance line 25-2, a first inner 20-ohm low impedance line 25-3, an upper right 100-ohm high impedance line 25-4, a second inner 20-ohm low impedance line 25-10, a lower right 100-ohm high impedance line 25-5, a second outer 20-ohm low impedance line 25-11, and a step impedance lower port 25-7, which are sequentially connected on a low-pass step impedance line part 25; among them, the upper right 100-ohm high impedance line 25-4 and the lower right 100-ohm high impedance line 25-5 are bent; the low-pass step impedance line part 25 further includes a step impedance same-layer transmission microstrip line 25-9 under the first outer 20-ohm low impedance line 25-1; two first S-band feeding metal vias 16 on the low-pass step impedance line part 25 are respectively located on the step impedance upper port 25-6 and at the bottom of the step impedance same-layer transmission microstrip line 25-9; two second S-band feeding metal vias 21 on the low-pass step impedance line part 25 are respectively located on the step impedance lower port 25-7 and at the top of the step impedance same-layer transmission microstrip line 25-9.

[0054] On the first-layer metal floor part 5, the width dimension w of the signal input / output terminal 24, the S-band frequency selection path 18-1, the X-band frequency selection path 18-2, and the C-band frequency selection path 18-3 is 0.634 mm; the diameter dimension R of the first S-band feeding metal via 16 s is 0.2 mm; the diameter dimension R of the X-band feeding metal via 14 x is 0.2 mm; the diameter dimension R of the C-band feeding metal via 15 c is 0.3 mm.

[0055] On the second-layer metal floor part 4, the transverse dimension l of the slotted part of the X-band bandpass filter unit x is 4.28 mm, the distance l from the X-band tap input / output part 1-1 to the metal floor on its right xt is 1.83 mm, the distance c from the left end of the first X-band resonator 1-2-1 to the metal floor on its left x1 is 0.05 mm; the distance c from the right end of the second X-band resonator 1-2-2 to the metal floor on its right x2 is 0.43 mm; the distance c from the left end of the third X-band resonator 1-2-3 to the metal floor on its left x3 is 0.42 mm; the distance c from the right end of the fourth X-band resonator 1-2-4 to the metal floor on its right x4 is 0.41 mm, and the distance d between the first X-band resonator 1-2-1 and the second X-band resonator 1-2-2 x1is 0.095 mm, the distance d between the second X-band resonator 1-2-2 and the third X-band resonator 1-2-3 x2 is 0.136 mm, the distance d between the third X-band resonator 1-2-3 and the fourth X-band resonator 1-2-4 x3 is 0.154 mm, the width w of the 7 X-band resonators x are all 0.24 mm. The size limitation of the X-band bandpass filter unit ensures that the passband bandwidth under X-band bandpass filtering is 4 GHz and the center frequency is 10 GHz.

[0056] On the second-layer metal floor part 4, the transverse dimension l of the slotted part of the C-band bandpass filter unit c is 7.394 mm, the distance l between the C-band tap input / output part 2-1 and the metal floor on its right ct is 3.773 mm, the distance c between the left end of the first C-band resonator 2-2-1 and the metal floor on its left t1 is 0.042 mm; the distance c between the right end of the second C-band resonator 2-2-2 and the metal floor on its right t2 is 0.747 mm; the distance c between the left end of the third C-band resonator 2-2-3 and the metal floor on its left t3 is 0.822 mm; the distance c between the right end of the fourth C-band resonator 2-2-4 and the metal floor on its right t4 is 0.813 mm, the distance d between the first C-band resonator 2-2-1 and the second C-band resonator 2-2-2 c1 is 0.042 mm, the distance d between the second C-band resonator 2-2-2 and the third C-band resonator 2-2-3 c2 is 0.052 mm, the distance d between the third C-band resonator 2-2-3 and the fourth C-band resonator 2-2-4 c3 is 0.06 mm, the width w of the 7 C-band resonators c are all 0.3 mm. The size limitation of the C-band bandpass filter unit ensures that the passband bandwidth under C-band bandpass filtering is 4 GHz and the center frequency is 6 GHz.

[0057] On the fourth-layer metal floor part 10, the transverse dimension l of the slotted part of the S-band bandpass filter unit s is 15.45 mm, the distance l between the S-band tap input / output part 3-1 and the metal floor on its right st is 9.805 mm, the distance c between the left end of the first S-band resonator 3-2-1 and the metal floor on its left s1 is 0.05 mm; the distance c between the right end of the second S-band resonator 3-2-2 and the metal floor on its right s2is 2.487 mm; the distance c from the left end of the third S-band resonator 3-2-3 to the metal floor on its left side s3 is 2.35 mm; the distance c from the right end of the fourth S-band resonator 3-2-4 to the metal floor on its right side s4 is 2.387 mm, the distance between the first S-band resonator 3-2-1 and the second S-band resonator 3-2-2 is 0.095 mm, the distance between the second S-band resonator 3-2-2 and the third S-band resonator 3-2-3 is 0.136 mm, the distance between the third S-band resonator 3-2-3 and the fourth S-band resonator 3-2-4 is 0.154 mm, the width w of the 7 S-band resonators s are all 0.17 mm. The size limitation of the S-band bandpass filter unit ensures that the passband bandwidth under S-band bandpass filtering is 2 GHz and the center frequency is 3 GHz.

[0058] On the low-pass stepped impedance line part 25, the transverse dimension w of the first part of the low-pass stepped impedance line same-layer metal floor 25-8 2 is 0.6 mm, the longitudinal dimension l 9 is 1.8 mm; the transverse dimension l' of the second part of the low-pass stepped impedance line same-layer metal floor 25-8 9 is 1.8 mm, the longitudinal dimension w 2 is 0.6 mm; the transverse dimension l of the upper-side port 25-6 of the stepped impedance line 0 is 0.848 mm, the longitudinal dimension w 1 is 0.634 mm; the transverse dimension l of the lower-side port 25-7 of the stepped impedance line 8 is 6.028 mm, the longitudinal dimension w 1 is 0.634 mm; the transverse dimension l of the first outer 20-ohm low-impedance line 25-1 and the second outer 20-ohm low-impedance line 25-11 1 is 2.104 mm, the longitudinal dimension w l is 2.414 mm; the transverse dimension l of the first inner 20-ohm low-impedance line 25-3 3 is 4.673 mm, the longitudinal dimension w l is 2.414 mm; the transverse dimension w of the second inner 20-ohm low-impedance line 25-10 l is 2.414 mm, the longitudinal dimension l 3 is 4.673 mm; the transverse dimension l of the upper-left 100-ohm high-impedance line 25-2 2 is 4.507 mm, the longitudinal dimension w h is 0.084 mm; the transverse dimension l of the upper-right 100-ohm high-impedance line 25-44 +l 5 is 2.271 mm + 2.515 mm = 4.786 mm, and the longitudinal dimension w h is 0.084 mm; the transverse dimension l 6 +l 7 of the 100-ohm high-impedance line 25-5 on the lower right side is 0.449 mm + 4.058 mm = 4.507 mm, and the longitudinal dimension w h is 0.084 mm; the transverse dimension w 1 of the first part of the stepped-impedance line same-layer transmission microstrip line 25-9 is 0.634 mm, and the longitudinal dimension l 10 is 0.6 mm; the transverse dimension w 1 of the second part of the stepped-impedance line same-layer transmission microstrip line 25-9 is 0.634 mm, and the longitudinal dimension l 11 is 5.764 mm, the tilt angle θ is 71.3°, and the transverse dimension l 12 of the upper boundary of the third part of the stepped-impedance line same-layer transmission microstrip line 25-9 is 0.634 mm, and the transverse dimension l' 12 is 0.634 mm, and the longitudinal dimension w 1 is 0.634 mm. The size limitation of the low-pass stepped-impedance line part 25 ensures that the cut-off frequency of the low-pass part is 4 GHz, which can effectively suppress the harmonic resonance generated at 7 - 10 GHz in the S band.

[0059] When a forward voltage is applied to the S-band frequency-selective PIN diode 19-1 (the S-band DC bias pad 3 is connected to the high level of the DC source, and the DC bias pad 19 is connected to the low level of the DC source), the S-band frequency-selective PIN diode 19-1 conducts. The AC signal first enters the signal input / output terminal 24 through the SMA connector, passes through the S-band 18-1 frequency-selective path, then enters the low-pass stepped-impedance line part 25 through the first S-band feeding metal through-hole 16, and then is fed into the S-band tap input / output part 3-1 and the S-band interdigital metal resonator part 3-2 of the S-band interdigital band-pass filtering part through the second S-band feeding metal through-hole 21, and finally reaches the signal input / output terminal 24, realizing the S-band filtering function with harmonic resonance suppression;

[0060] When a forward voltage is applied to the X-band frequency-selective PIN diode 19-2 (the X-band DC bias pad 1 is connected to the high level of the DC source, and the DC bias pad 19 is connected to the low level of the DC source), the X-band frequency-selective PIN diode 19-2 conducts. The AC signal first enters the signal input / output terminal 24 through the SMA connector, passes through the X-band 18-2 frequency-selective path, then enters the X-band tap input / output part 1-1 and the X-band interdigital metal resonator part 1-2 of the X-band interdigital band-pass filtering part through the X-band feeding metal through-hole 14, and finally reaches the signal input / output terminal 24 to realize the X-band filtering function;

[0061] When a forward voltage is applied to the C-band frequency-selective PIN diode 19-3 (the C-band DC bias pad 2 is connected to the high level of the DC source, and the DC bias pad 19 is connected to the low level of the DC source), the C-band frequency-selective PIN diode 19-3 conducts. The AC signal first enters the signal input / output terminal 24 through the SMA connector. After passing through the C-band 18-3 frequency-selective path, it is then fed into the C-band tap input / output part 2-1 and the C-band interdigital metal resonator part 2-2 of the C-band interdigital bandpass filter section through the C-band feed-through via 15, and finally reaches the signal input / output terminal 24 to achieve the C-band filtering function.

[0062] As Figures 21 - 22 shown in the simulation S-parameter diagram of the S, C, and X-band active switchable bandpass filter, the abscissa represents frequency, and the ordinate represents the S-parameter, with the unit of dB. From Figures 21 - 22 it can be seen that when the S-band frequency-selective PIN diode 19-1 conducts and other diodes are all cut off, the filter has a -3dB bandwidth of 1.92 GHz - 4.08 GHz (relative bandwidth 72%) and is in the S-band; the in-band insertion loss is better than -0.6 dB, and the return loss is better than -12 dB. When the X-band frequency-selective PIN diode 19-2 conducts and other diodes are all cut off, the filter has a -3dB bandwidth of 7.93 GHz - 12.15 GHz (relative bandwidth 42%) and is in the X-band; the in-band insertion loss is better than -0.6 dB, and the return loss is better than -12 dB. When the C-band frequency-selective PIN diode 19-3 conducts and other diodes are all cut off, the filter has a -3dB bandwidth of 3.90 GHz - 8.06 GHz (relative bandwidth 69%) and is in the C-band; the in-band insertion loss is better than -0.5 dB, and the return loss is better than -13 dB. From the simulation results, it can be seen that without changing the input electromagnetic wave signal, by controlling the DC source to conduct and cut off the PIN diodes, the bandpass filtering effect can be switched very efficiently among the S, C, and X bands with excellent performance.

[0063] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. An S, C, X three-band active switchable bandpass filter, characterized in that: include: The eleven layers of structure stacked in sequence are respectively a first metal floor portion (5), a first dielectric substrate portion (6), a second metal floor portion (4), a second dielectric substrate portion (7), a third metal floor portion (8), a third dielectric substrate portion (9), a fourth metal floor portion (10), a fourth dielectric substrate portion (11), a fifth metal floor portion (12), a fifth dielectric substrate portion (13) and a low-pass step impedance line portion (25); The bandpass filter comprises an X-band bandpass filter unit, which comprises an X-band DC bias pad (1), an X-band frequency selection path (18-2), an X-band frequency selection PIN diode (19-2), an X-band inductor (20-4) and an input / output microstrip line DC bias inductor (20-2) on a first metal floor portion (5); the left side of the X-band frequency selection path (18-2) is connected to the X-band DC bias pad (1) through the X-band inductor (20-4); the bottom side of the X-band frequency selection path (18-2) is connected to a signal input / output terminal (24) through an X-band frequency selection PIN diode (19-2); the right side of the signal input / output terminal (24) is connected to the DC bias pad (19) through the input / output microstrip line DC bias inductor (20-2); The X-band bandpass filter unit comprises an X-band tap input-output portion (1-1) and an X-band interdigital metal resonator portion (1-2) located on the second metal floor portion (4); the X-band interdigital metal resonator portion (1-2) comprises seven X-band resonators with one end short-circuited and one end open-circuited; two X-band tap input-output portions (1-1) are located on both sides of the seven X-band resonators; The X-band bandpass filter unit comprises an X-band feeding metal through hole (14), which is located on the X-band frequency selection path (18-2) and on the X-band tap input and output part (1-1), and sequentially penetrates the first metal floor part (5), the first dielectric substrate part (6) and the second metal floor part (4); The X-band bandpass filter unit comprises a C-band and an X-band grounding metal through hole (17), wherein the C-band and the X-band grounding metal through hole (17) is located on a middle metal plate (28) in the middle of the first metal floor portion (5) and sequentially penetrates the first metal floor portion (5), the first dielectric substrate portion (6), the second metal floor portion (4), the second dielectric substrate portion (7) and the third metal floor portion (8); The C and X band grounding metal through holes (17) include a plurality of through holes located on the left side of the middle metal plate (28), a plurality of through holes located in the middle of the metal plate (28) and distributed in an I-shape, and a plurality of through holes located on the right side of the middle metal plate (28); The bandpass filter comprises a C-band bandpass filter unit, and the C-band bandpass filter unit comprises a C-band DC bias pad (2) on the first metal floor portion (5), a C-band frequency selection path (18-3), a C-band frequency selection PIN diode (19-3) and a C-band inductor (20-3); The right side of the C-band frequency selection path (18-3) is connected to the C-band DC bias pad (2) via the C-band inductor (20-3); the left side of the C-band frequency selection path (18-3) is connected to the signal input and output end (24) via the C-band frequency selection PIN diode (19-3); The C-band bandpass filter unit comprises a C-band tap input-output portion (2-1) and a C-band interdigital metal resonator portion (2-2) located on the second metal floor portion (4); the C-band interdigital metal resonator portion (2-2) comprises seven C-band resonators with one end short-circuited and one end open-circuited; two C-band tap input-output portions (2-1) are located on both sides of the seven C-band resonators; The C-band bandpass filter unit comprises a C-band feeding metal through hole (15), which is located on the C-band frequency selection path (18-3) and on the C-band tap input and output part (2-1), and sequentially penetrates the first metal floor part (5), the first dielectric substrate part (6) and the second metal floor part (4); The bandpass filter comprises an S-band bandpass filter unit, and the S-band bandpass filter unit comprises an S-band DC bias pad (3) on the first metal floor portion (5), an S-band frequency selection path (18-1), an S-band frequency selection PIN diode (19-1) and an S-band inductor (20-1); The upper side of the S-band frequency selection path (18-1) is connected to the S-band DC bias pad (3) via the S-band inductor (20-1); the right side of the S-band frequency selection path (18-1) is connected to the signal input and output end (24) via the S-band frequency selection PIN diode (19-1); The S-band bandpass filter unit comprises an S-band tap input and output portion (3-1) and an S-band interdigital metal resonator portion (3-2) located on the fourth metal floor portion (10); The S-band interdigital metal resonator part (3-2) includes seven S-band resonators with one end short-circuited and one end open-circuited; two S-band tap input and output parts (3-1) are located on both sides of the seven S-band resonators; The S-band bandpass filter unit comprises a plurality of multi-layer metal grounding plate connecting through holes (23) located on the first layer metal floor portion (5); the multi-layer metal grounding plate connecting through holes (23) sequentially penetrate the eleven-layer structure; The S-band bandpass filter unit comprises a first S-band feeding metal through hole (16), which is located on the S-band frequency selection path (18-1) and sequentially passes through the eleven-layer structure; the outer sides of the first S-band feeding metal through hole (16) on the second metal floor portion (4), the third metal floor portion (8), the fourth metal floor portion (10) and the fifth metal floor portion (12) are respectively provided with circular slotted portions (26); The S-band bandpass filter unit comprises a second S-band feeding metal through hole (21), the second S-band feeding metal through hole (21) is located on the S-band tap input and output part (3-1), and sequentially penetrates the fourth metal floor part (10), the fourth dielectric substrate part (11), the fifth metal floor part (12), the fifth dielectric substrate part (13) and the low-pass step impedance line part (25); a circular slot part (26) is provided on the outer side of the second S-band feeding metal through hole (21) on the fifth metal floor part (12); The S-band bandpass filter unit comprises an S-band third-layer metal floor grounding through hole (27) located on the third-layer metal floor portion (8), the S-band third-layer metal floor grounding through hole (27) comprising a plurality of through holes located on the left side of the C- and X-band grounding metal through holes (17) and a plurality of through holes located on the right side of the plurality of through holes distributed in an I-shape; The S-band bandpass filter unit comprises a plurality of S-band grounding metal through holes (22) which sequentially penetrate the third dielectric substrate portion (9), the fourth metal floor portion (10), the fourth dielectric substrate portion (11) and the fifth metal floor portion (12); the plurality of S-band grounding metal through holes (22) are respectively located around the S-band interdigital metal resonator portion (3-2).

2. The S, C, X three-band active switchable bandpass filter according to claim 1, characterized in that: The X-band interdigital metal resonator part (1-2) comprises: a first X-band resonator (1-2-1), a second X-band resonator (1-2-2), a third X-band resonator (1-2-3), a fourth X-band resonator (1-2-4), a fifth X-band resonator (1-2-5), a sixth X-band resonator (1-2-6) and a seventh X-band resonator (1-2-7); two X-band tap input and output parts (1-1) are respectively located at the upper part of the first X-band resonator (1-2-1) and the lower part of the seventh X-band resonator (1-2-7); the first X-band resonator (1-2-1) and the seventh X-band resonator (1-2-7) are connected with each other with respect to the fourth X-band resonator (1-2 -4); the second X-band resonator (1-2-2) and the sixth X-band resonator (1-2-6) are symmetrical about the fourth X-band resonator (1-2-4); the third X-band resonator (1-2-3) and the fifth X-band resonator (1-2-5) are symmetrical about the fourth X-band resonator (1-2-4); the first X-band resonator (1-2-1), the third X-band resonator (1-2-3), the fifth X-band resonator (1-2-5) and the seventh X-band resonator (1-2-7) are open-circuited on the left and short-circuited on the right; the second X-band resonator (1-2-2), the fourth X-band resonator (1-2-4) and the sixth X-band resonator (1-2-6) are short-circuited on the left and open-circuited on the right.

3. The S, C, X three-band active switchable bandpass filter according to claim 1, characterized in that: The C-band interdigital metal resonator part (2-2) comprises: a first C-band resonator (2-2-1), a second C-band resonator (2-2-2), a third C-band resonator (2-2-3), a fourth C-band resonator (2-2-4), a fifth C-band resonator (2-2-5), a sixth C-band resonator (2-2-6) and a seventh C-band resonator (2-2-7); two C-band tap input and output parts (2-1) are respectively located at the upper part of the first C-band resonator (2-2-1) and the lower part of the seventh C-band resonator (2-2-7); the first C-band resonator (2-2-1) and the seventh C-band resonator (2-2-7) are connected with each other with respect to the fourth C-band resonator (2-2 -4); the second C-band resonator (2-2-2) and the sixth C-band resonator (2-2-6) are symmetrical about the fourth C-band resonator (2-2-4); the third C-band resonator (2-2-3) and the fifth C-band resonator (2-2-5) are symmetrical about the fourth C-band resonator (2-2-4); the first C-band resonator (2-2-1), the third C-band resonator (2-2-3), the fifth C-band resonator (2-2-5) and the seventh C-band resonator (2-2-7) are open-circuited on the left and short-circuited on the right; the second C-band resonator (2-2-2), the fourth C-band resonator (2-2-4) and the sixth C-band resonator (2-2-6) are short-circuited on the left and open-circuited on the right.

4. The S, C, X three-band active switchable bandpass filter according to claim 1, characterized in that: The S-band interdigital metal resonator part (3-2) comprises: a first S-band resonator (3-2-1), a second S-band resonator (3-2-2), a third S-band resonator (3-2-3), a fourth S-band resonator (3-2-4), a fifth S-band resonator (3-2-5), a sixth S-band resonator (3-2-6) and a seventh S-band resonator (3-2-7); two S-band tap input and output parts (3-1) are respectively located at the upper part of the first S-band resonator (3-2-1) and the lower part of the seventh S-band resonator (3-2-7); the first S-band resonator (3-2-1) and the seventh S-band resonator (3-2-7) are connected with each other with respect to the fourth S-band resonator (3-2 -4); the second S-band resonator (3-2-2) and the sixth S-band resonator (3-2-6) are symmetrical about the fourth S-band resonator (3-2-4); the third S-band resonator (3-2-3) and the fifth S-band resonator (3-2-5) are symmetrical about the fourth S-band resonator (3-2-4); the first S-band resonator (3-2-1), the third S-band resonator (3-2-3), the fifth S-band resonator (3-2-5) and the seventh S-band resonator (3-2-7) are open-circuited on the left and short-circuited on the right; the second S-band resonator (3-2-2), the fourth S-band resonator (3-2-4) and the sixth S-band resonator (3-2-6) are short-circuited on the left and open-circuited on the right.

5. The S, C, X three-band active switchable bandpass filter according to claim 1, characterized in that: The S-band bandpass filter unit comprises a step impedance line upper port (25-6), a first outer 20 ohm low impedance line (25-1), a left upper 100 ohm high impedance line (25-2), a first inner 20 ohm low impedance line (25-3), a right upper 100 ohm high impedance line (25-4), a second inner 20 ohm low impedance line (25-10), a right lower 100 ohm high impedance line (25-5), a second outer 20 ohm low impedance line (25-11) and a step impedance line lower port (25-7) connected in sequence on a low-pass step impedance line part (25); wherein the right upper 100 ohm high impedance line (25-4) and the right lower 100 ohm high impedance line (25-5) are connected in sequence to the step impedance line upper port (25-6); wherein the right upper 100 ohm high impedance line (25-4) and the right lower 100 ohm high impedance line (25-2) are connected to the step impedance line lower port (25-7) in sequence; The 100 ohm high impedance line (25-5) is bent; the low-pass step impedance line portion (25) further comprises a step impedance line same-layer transmission microstrip line (25-9) below the first outer 20 ohm low impedance line (25-1); two first S-band feeding metal through holes (16) on the low-pass step impedance line portion (25) are respectively located on the upper side port (25-6) of the step impedance line and the bottom of the step impedance line same-layer transmission microstrip line (25-9); and two second S-band feeding metal through holes (21) on the low-pass step impedance line portion (25) are respectively located on the lower side port (25-7) of the step impedance line and the top of the step impedance line same-layer transmission microstrip line (25-9).

6. The S, C, X three-band active switchable bandpass filter according to claim 1, characterized in that: On the first metal floor portion (5), the width dimension w of the signal input and output terminal (24), the S-band frequency selection path (18-1), the X-band frequency selection path (18-2) and the C-band frequency selection path (18-3) is 0.634 mm; the diameter dimension R of the first S-band feeding metal through hole (16) is s The diameter size R of the X-band feeding metal through hole (14) is 0.2 mm. x The diameter of the C-band feeding metal through hole (15) is 0.2 mm. c It is 0.3mm.

7. The S, C, X three-band active switchable bandpass filter according to claim 1, characterized in that: On the second metal floor portion (4), the lateral dimension of the slotted portion of the X-band bandpass filter unit is l x The distance between the X-band tap input and output part (1-1) and the metal floor on its right side is l xt is 1.83 mm, and the distance c between the left end of the first X-band resonator (1-2-1) and the metal floor on its left side is x1 is 0.05mm; the distance c between the right end of the second X-band resonator (1-2-2) and the metal floor on its right side is x2 is 0.43 mm; the distance c between the left end of the third X-band resonator (1-2-3) and the metal floor on its left side is x3 is 0.42 mm; the distance c between the right end of the fourth X-band resonator (1-2-4) and the metal floor on its right side is x4 is 0.41 mm, and the distance d between the first X-band resonator (1-2-1) and the second X-band resonator (1-2-2) is x1 is 0.095 mm, and the distance d between the second X-band resonator (1-2-2) and the third X-band resonator (1-2-3) is x2 is 0.136 mm, and the distance d between the third X-band resonator (1-2-3) and the fourth X-band resonator (1-2-4) is x3 The width w of the 7 X-band resonators is 0.154 mm. x Both are 0.24mm.

8. The S, C, X three-band active switchable bandpass filter according to claim 1, characterized in that: On the second metal floor portion (4), the lateral dimension l of the slotted portion of the C-band bandpass filter unit is c The distance between the C-band tap input and output part (2-1) and the metal floor on its right side is l ct The distance c between the left end of the first C-band resonator (2-2-1) and the metal floor on its left side is 3.773 mm. t1 is 0.042mm; the distance c between the right end of the second C-band resonator (2-2-2) and the metal floor on its right side is t2 is 0.747 mm; the distance c between the left end of the third C-band resonator (2-2-3) and the metal floor on its left side is t3 The distance c between the right end of the fourth C-band resonator (2-2-4) and the metal floor on its right side is 0.822 mm. t4 is 0.813 mm, and the distance d between the first C-band resonator (2-2-1) and the second C-band resonator (2-2-2) is c1 is 0.042 mm, and the distance d between the second C-band resonator (2-2-2) and the third C-band resonator (2-2-3) is c2 is 0.052 mm, and the distance d between the third C-band resonator (2-2-3) and the fourth C-band resonator (2-2-4) is c3 The width w of the 7 C-band resonators is 0.06 mm. c Both are 0.3mm; The transverse dimension of the slotted portion of the S-band bandpass filter unit on the fourth metal floor portion (10) is l s The distance between the S-band tap input and output part (3-1) and the metal floor on its right side is l st is 9.805 mm, and the distance c between the left end of the first S-band resonator (3-2-1) and the metal floor on its left side is s1 is 0.05mm; the distance c between the right end of the second S-band resonator (3-2-2) and the metal floor on its right side is s2 is 2.487 mm; the distance c between the left end of the third S-band resonator (3-2-3) and the metal floor on its left side is s3 is 2.35mm; the distance c between the right end of the fourth S-band resonator (3-2-4) and the metal floor on its right side s4 is 2.387 mm, and the distance d between the first S-band resonator (3-2-1) and the second S-band resonator (3-2-2) is s1 is 0.095 mm, and the distance d between the second S-band resonator (3-2-2) and the third S-band resonator (3-2-3) is s2 is 0.136 mm, and the distance d between the third S-band resonator (3-2-3) and the fourth S-band resonator (3-2-4) is s3 The width w of the 7 S-band resonators is 0.154 mm. s Both are 0.17mm.

9. The S, C, X three-band active switchable bandpass filter according to claim 1, characterized in that: On the low-pass step impedance line part (25), the first part of the low-pass step impedance line on the same layer of metal floor (25-8) has a lateral dimension w2 of 0.6 mm and a longitudinal dimension l9 of 1.8 mm; the second part of the low-pass step impedance line on the same layer of metal floor (25-8) has a lateral dimension l'9 of 1.8 mm and a longitudinal dimension w2 of 0.6 mm; the upper port (25-6) of the step impedance line has a lateral dimension l0 of 0.848 mm and a longitudinal dimension w1 of 0.634 mm; the lower port (25-7) of the step impedance line has a lateral dimension l8 of 6.028 mm and a longitudinal dimension w1 of 0.634 mm; the first outer 20 ohm low impedance line (25-1) and the second outer 20 ohm low impedance line (25-11) have a lateral dimension l1 of 2.104 mm and a longitudinal dimension w l The first inner 20 ohm low impedance line (25-3) has a lateral dimension l3 of 4.673 mm and a longitudinal dimension w l The second inner 20 ohm low impedance line (25-10) has a lateral dimension w l The horizontal dimension l2 of the 100 ohm high impedance line (25-2) on the upper left side is 4.507 mm, and the vertical dimension w h The horizontal dimension l4+l5 of the 100 ohm high impedance line (25-4) on the upper right side is 2.271mm+2.515mm=4.786mm, and the vertical dimension w h The horizontal dimension l6+l7 of the 100 ohm high impedance line (25-5) on the lower right side is 0.449mm+4.058mm=4.507mm, and the vertical dimension w h The first part of the step impedance line same-layer transmission microstrip line (25-9) has a lateral dimension w1 of 0.634 mm and a longitudinal dimension l 10 The second part of the step impedance line same layer transmission microstrip line (25-9) has a lateral dimension w1 of 0.634 mm and a longitudinal dimension l 11 is 5.764 mm, the tilt angle θ is 71.3°, and the lateral dimension l of the upper boundary of the third part of the step impedance line same-layer transmission microstrip line (25-9) 12 0.634mm, the horizontal dimension of the lower boundary is l' 12 It is 0.634mm and the longitudinal dimension w1 is 0.634mm.

10. The S, C, X three-band active switchable bandpass filter according to claim 1, characterized in that: The thickness of the first metal floor portion (5), the second metal floor portion (4), the third metal floor portion (8), the fourth metal floor portion (10), the fifth metal floor portion (12) and the low-pass step impedance line portion (25) is 0.035 mm; the thickness of the first dielectric substrate portion (6), the second dielectric substrate portion (7), the third dielectric substrate portion (9), the fourth dielectric substrate portion (11) and the fifth dielectric substrate portion (13) is 0.3 mm, the relative dielectric constant is 3.55, and the loss tangent is 0.0025.

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