A bandwidth-coded reconfigurable bandpass filter

Abstract

The present invention discloses a bandwidth-coded reconfigurable bandpass filter, comprising a first metal ground plane, a second dielectric substrate, a third interdigital resonator, a fourth dielectric substrate, and a fifth metal ground plane stacked in sequence. The first metal ground plane includes a first metal strip group, with the left and right sides of the first metal strip group connected to the first metal ground plane via a first diode group. The third interdigital resonator includes a middle metal ground plane, with a resonator group connected to the middle metal ground plane, and the upper and lower sides of the resonator group are connected to a grounded coplanar waveguide via tapped striplines. The fifth metal ground plane includes a fifth metal strip group, with the left and right sides of the fifth metal strip group connected to the fifth metal ground plane via a fifth diode group. The present invention has a wide bandwidth adjustment range and flexible discrete bandwidth control capabilities, is less dependent on tuning components, and offers superior performance.

Description

Technical Field

[0001] The invention belongs to the technical field of active tunable filters, and in particular relates to a bandwidth-coded reconfigurable bandpass filter. Background Art

[0002] With the rapid development of wireless communication and integrated circuit technologies, the demand for small, wide-band, and tunable bandpass filters is becoming increasingly urgent. At the same time, due to the complex modern communication environment, narrowband systems are no longer suitable for some applications, and there is an urgent need for bandpass filters that can switch between wideband and narrowband.

[0003] Active adjustable elements, such as PIN diodes and varactor diodes, can change the filter's equivalent circuit parameters by varying capacitance or branch length, thus achieving tunability. Furthermore, the stripline interdigital structure offers compact size and fast roll-off, making it suitable for use in modern miniaturized integrated circuits.

[0004] PIN diodes have the characteristics of being turned on by forward voltage and cut off by reverse voltage. The on and off of the circuit can be switched by changing the bias voltage, thereby adjusting the equivalent electrical size, state and other characteristics of the microwave structure.

[0005] An interdigitated stripline filter consists of a middle layer of parallel TEM-mode stripline resonators and two upper and lower ground planes. Each resonator is a quarter wavelength long, short-circuited at one end and open-circuited at the other. Adjacent resonant units are coupled via the field edges to achieve a bandpass effect. In 2018, Salman Arain et al. proposed a bandwidth-reconfigurable filter with high-frequency rejection in "Reconfigurable Bandwidth Bandpass Filter With Enhanced Out-of-Band Rejection Using π-Section-Loaded Ring Resonator" (IEEE Microwave and Wireless Component Letters, vol. 28, no. 1, Jan 2018). Using PIN transistors to control the connection and disconnection of branches, the filter extends the fractional bandwidth from 39.5% to 90%. However, this type of filter generally suffers from the problem of excessive dependence on the performance of the tuning element. In 2021, Fan et al. proposed a bandpass filter with adjustable bandwidth and center frequency in "Reconfigurable Bandpass Filter With Wide-Range Bandwidth and Frequency Control" (IEEE Transactions on Circuits and Systems, vol. 68, no. 6, June 2021). This filter is composed of a cascade of high-pass and low-pass filters, and uses varactor diodes to control the cutoff frequencies of the two filters, respectively, to adjust the upper and lower cutoff frequencies. However, this type of filter has a narrow adjustable range, and due to the nonlinear distortion of the varactor diode, the passband performance is less than ideal. In 2022, Ponnammal P. et al. proposed a switchable bandpass filter in "Miniaturized bandwidth reconfigurable microwave bandpass filter" (Microelectronics International: Journal of ISHM--Europe, the Microelectronics Society--Europe, 17 June 2022, Vol. 39, Issue 3, pages 121-131). This filter uses PIN diodes to switch between a hexagonal ring and its surrounding bias network, enabling switching between narrow dual-bandpass (center frequencies of 2.1 GHz and 4.5 GHz) and wide passband (2.1 to 5.9 GHz). However, this structure has limited adjustable states and the microstrip structure has certain radiation losses. Summary of the Invention

[0006] The purpose of the present invention is to provide a bandwidth-coded reconfigurable bandpass filter with a large adjustable bandwidth range, flexible discrete bandwidth control capability, low dependence on tuning elements and superior performance.

[0007] To achieve the above object, the present invention provides a bandwidth-coded reconfigurable bandpass filter, comprising a first metal ground plate, a second dielectric substrate, a third interdigital resonator, a fourth dielectric substrate, and a fifth metal ground plate stacked in sequence;

[0008] The bandpass filter is provided with a grounding through hole which sequentially penetrates the first metal grounding plate, the second dielectric substrate, the third interdigital resonator, the fourth dielectric substrate and the fifth metal grounding plate;

[0009] A top through groove is provided in the middle of the first metal grounding plate, and a first metal strip group is provided in the top through groove. The left and right sides of the first metal strip group are connected to the first metal grounding plate through the first diode group.

[0010] The third-layer interdigital resonator includes a middle metal ground plate, which is composed of symmetrically arranged concave ground plates with openings facing each other. A resonator group is connected between the two concave ground plates. The upper and lower sides of the resonator group are respectively connected to a grounded coplanar waveguide through a tapped stripline. The other end of the grounded coplanar waveguide is connected to the SMA connector.

[0011] A bottom through slot is provided in the middle of the fifth metal grounding plate, in which a fifth metal strip group is provided. The left and right sides of the fifth metal strip group are connected to the fifth metal grounding plate through a fifth diode group.

[0012] As a further solution of the present invention: the first layer of metal strip group includes a metal strip V, and metal strips IV and III are symmetrically distributed on the upper and lower sides of the metal strip V.

[0013] As a further solution of the present invention: the first layer diode group includes diode III, diode IV, and diode V, and the left and right sides of metal strips III, metal strip IV, and metal strip V are connected to the first layer metal ground plate through diode III, diode IV, and diode V respectively.

[0014] As a further solution of the present invention: the resonator group includes a resonator IV, and resonators III, resonator II, and resonator I are symmetrically distributed on the upper and lower sides of resonator IV; the left end of resonator I is short-circuited and the right end is open, the right end of resonator II is short-circuited and the left end is open, and the left end of resonator III is short-circuited and the right end is open.

[0015] As a further solution of the present invention: the fifth-layer metal strip group includes metal strip I and metal strip II, and the bottom layer through groove is divided into upper and lower parts by a middle partition, and the metal strip I and metal strip II are symmetrically distributed in the upper and lower parts respectively; the fifth-layer diode group includes diode I and diode II, and the left and right sides of metal strip I and metal strip II are connected to the fifth-layer metal ground plate through diode I and diode II respectively.

[0016] As a further embodiment of the present invention, the lateral dimension w of the first metal ground plate, the second dielectric substrate, the middle metal ground plate, the fourth dielectric substrate, and the fifth metal floor is 10 mm; the longitudinal dimension l of the first metal ground plate and the second dielectric substrate is 7.4 mm; and the longitudinal dimension p of the middle metal ground plate, the fourth dielectric substrate, and the fifth metal floor is 11.4 mm.

[0017] The thickness of the first metal floor, the third interdigital resonator, and the fifth metal floor is 0.035 mm. The relative dielectric constant of the second dielectric substrate and the fourth dielectric substrate is 3.55 and the thickness is 0.3 mm.

[0018] The diameter of the ground via is 0.2mm.

[0019] As a further solution of the present invention: the lateral dimension l of the top through groove is u The longitudinal dimension w is 7.644mm. u 3.2mm;

[0020] The longitudinal distance g between the metal strip III and the first metal ground plane u The longitudinal distance d between metal strip III and metal strip IV is 0.436 mm. u The longitudinal distance d between metal strip IV and metal strip V is 0.179 mm. l 0.16mm;

[0021] Transverse dimension S of metal strip III, metal strip IV, and metal strip V u Both are 6.944mm, and the longitudinal dimension w l Both are 0.33mm.

[0022] As a further solution of the present invention: the dimension lc between the openings of the two concave ground plates is 7.644 mm, and the longitudinal dimension w is 7.644 mm. c 5mm;

[0023] The lateral dimension S0 of the grounded coplanar waveguide is 0.6 mm, the longitudinal dimension l1 is 1.5 mm, and the lateral spacing g0 between the grounded coplanar waveguide and the middle metal ground plate is 0.379 mm;

[0024] The lateral dimension w0 of the tapped stripline is 0.3 mm, and the longitudinal dimension l0 is 2.261 mm;

[0025] The lateral spacing d1 between resonator I and the middle metal ground plane is 0.121 mm, the lateral spacing d2 between resonator II and the middle metal ground plane is 1.147 mm, the lateral spacing d3 between resonator III and the middle metal ground plane is 1.122 mm, and the lateral spacing d4 between resonator IV and the middle metal ground plane is 1.113 mm;

[0026] The longitudinal spacing c1 between resonator I and resonator II is 0.08 mm, the longitudinal spacing c2 between resonator II and resonator III is 0.138 mm, and the longitudinal spacing c3 between resonator III and resonator IV is 0.171 mm;

[0027] The longitudinal dimension w0 of resonator I, resonator II, resonator III, and resonator IV is 0.3 mm.

[0028] As a further solution of the present invention: the lateral dimension l of the bottom through groove is d The longitudinal dimension w is 2.96mm. d 3.03mm;

[0029] The longitudinal distance g between the metal strip I and the fifth metal ground plate l The longitudinal distance g between the metal strip II and the fifth metal ground plane is 0.085 mm. d The longitudinal distance d between metal strips I and II is 0.05 mm. d 0.67mm;

[0030] Transverse dimension S of metal strip I and metal strip II d Both are 2.3mm, longitudinal dimension w l Both are 0.33mm.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] Diodes are used to control the connection between the metal strips and the grounding end to achieve switching between the non-grounded and grounded states. The metal strips are divided into 5 groups (3 groups on the first-layer metal grounding plate and 2 groups on the fifth-layer metal grounding plate). The states of the strips in each group are the same, and the states between each group are different. By regulating the states of different metal strips on the first-layer metal grounding plate and the fifth-layer metal grounding plate, the purpose of discrete control of bandwidth is achieved.

[0033] According to the state combination between each group of strips, there are 16 performance combinations that meet the requirements, with absolute bandwidth (-3dB) ranging from 2.29GHz to 5.68GHz, relative bandwidth ranging from 38% to 90%, and center frequencies all around 6GHz. The bandwidth has a large adjustable range and flexible discrete bandwidth control capability. The filter uses SMA coaxial connectors for feeding, and the AC signal input and output both use coplanar waveguides, and FPGA coding is used to control the active devices. Since the signal is concentrated between the ground plate and the transmission line, and the tuning element is at the ground plate, the dependence on the performance of the tuning element is not strong. Compared with traditional active adjustable structures, this bandpass filter has the characteristics of a large bandwidth adjustable range, compact size (10mm×11.4mm), weak dependence on tuning elements, superior performance, and low processing cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is an exploded view of the bandpass filter of the present invention;

[0035] Figure 2 Schematic diagram of the combined structure of the bandpass filter of the present invention;

[0036] Figure 3 Schematic diagram of the structure of the first metal ground plate of the bandpass filter of the present invention;

[0037] Figure 4 1 is a schematic structural diagram of the third layer of interdigital resonators of the bandpass filter of the present invention;

[0038] Figure 5 1 is a schematic structural diagram of the fifth metal ground plate of the bandpass filter of the present invention;

[0039] Figure 6 Schematic diagram of the dimensions of the first metal ground plate of the bandpass filter of the present invention;

[0040] Figure 7 Schematic diagram of the dimensions of the second dielectric substrate of the bandpass filter of the present invention;

[0041] Figure 8 Schematic diagram of the dimensions of the third layer of interdigital resonators of the bandpass filter of the present invention;

[0042] Figure 9 Schematic diagram of the dimensions of the fourth dielectric substrate of the bandpass filter of the present invention;

[0043] Figure 10 Schematic diagram of the dimensions of the fifth metal ground plate of the bandpass filter of the present invention;

[0044] Figure 11 Schematic diagram of the port of the bandpass filter of the present invention using FPGA for feeding (first metal ground plate);

[0045] Figure 12 Schematic diagram of the port of the bandpass filter of the present invention using FPGA for feeding (fifth metal ground plate);

[0046] Figure 13 This is a performance parameter table (absolute bandwidth, center frequency, return loss) of 16 combinations of the bandpass filter of the present invention, where 1 represents diode conduction and 0 represents diode cutoff;

[0047] Figure 14 It is a schematic diagram of the coupling capacitance of two parallel coupled transmission lines a and b under the electric wall and magnetic wall;

[0048] Figure 15 is the equivalent circuit diagram of the resonant frequency of two coupled transmission lines;

[0049] Figure 16 is the simulated insertion loss S of the bandpass filter of the present invention 21 Parameter diagram, the horizontal axis represents frequency, the vertical axis represents S parameter, the unit is dB;

[0050] Figure 17 is the simulated return loss S of the bandpass filter of the present invention 11 Parameter diagram, the horizontal axis represents frequency, the vertical axis represents S parameters, the unit is dB.

[0051] In the figure: 1. First layer metal ground plane, 2. Second layer dielectric substrate, 3. Third layer interdigital resonator, 4. Fourth layer dielectric substrate, 5. Fifth layer metal ground plane, 6. Ground via, 7. Top layer through slot, 8. Diode III, 9. Diode IV, 10. Diode V, 11. Metal strip III, 12. Metal strip IV, 13. Metal strip V, 14. Resonator I, 15. Resonator III, 16. Tapped stripline, 17. Grounded coplanar waveguide, 18. Resonator II, 19. Resonator IV, 20. Middle layer metal ground plane, 21. Bottom layer through slot, 22. Diode II, 23. Metal strip II, 24. Metal strip I, 25. Diode I. DETAILED DESCRIPTION

[0052] The present invention will be further described below by way of examples.

[0053] like Figures 1 to 5 As shown, a bandwidth-coded reconfigurable bandpass filter comprises a first metal ground plate 1, a second dielectric substrate 2, a third interdigital resonator 3, a fourth dielectric substrate 4, and a fifth metal ground plate 5, which are stacked in sequence;

[0054] The bandpass filter is provided with a grounding through hole 6 which sequentially penetrates the first metal grounding plate 1, the second dielectric substrate 2, the third interdigital resonator 3, the fourth dielectric substrate 4, and the fifth metal grounding plate 5;

[0055] A top through-groove 7 is provided in the middle of the first metal grounding plate 1. A first metal strip group is provided in the top through-groove 7. The left and right sides of the first metal strip group are connected to the first metal grounding plate 1 via a first diode group.

[0056] The third-layer interdigital resonator 3 includes a middle metal ground plate 20, which is composed of symmetrically arranged concave ground plates with openings facing each other. A resonator group is connected between the two concave ground plates. The upper and lower sides of the resonator group are respectively connected to a grounded coplanar waveguide 17 through a tapped stripline 16. The other end of the grounded coplanar waveguide 17 is connected to an SMA connector.

[0057] A bottom through slot 21 is provided in the middle of the fifth metal grounding plate 5 , and a fifth metal strip group is provided in the bottom through slot 21 . The left and right sides of the fifth metal strip group are connected to the fifth metal grounding plate 5 through the fifth diode group.

[0058] Further, such as Figure 3 As shown, the first layer of metal strip group includes a metal strip V13, and metal strips IV12 and III11 are symmetrically distributed on the upper and lower sides of the metal strip V13.

[0059] Furthermore, the first layer diode group includes diode III8, diode IV9, and diode V10, and the left and right sides of metal strips III11, metal strips IV12, and metal strips V13 are connected to the first layer metal ground plate 1 through diodes III8, IV9, and V10 respectively.

[0060] Further, such as Figure 4 As shown, the resonator group includes resonator IV19, and resonator III15, resonator II18, and resonator I14 are symmetrically distributed on the upper and lower sides of resonator IV19; the left end of resonator I14 is short-circuited and the right end is open, the right end of resonator II18 is short-circuited and the left end is open, and the left end of resonator III15 is short-circuited and the right end is open.

[0061] Further, such as Figure 5 As shown, the fifth-layer metal strip group includes metal strip I24 and metal strip II23. The bottom through groove 21 is divided into upper and lower parts by a partition in the middle. The metal strip I24 and metal strip II23 are symmetrically distributed in the upper and lower parts respectively; the fifth-layer diode group includes diode I25 and diode II22. The left and right sides of the metal strip I24 and metal strip II23 are connected to the fifth-layer metal ground plate 5 through diode I25 and diode II22 respectively.

[0062] Further, such as Figures 6 to 10 As shown, the transverse dimension w of the first metal ground plate 1, the second dielectric substrate 2, the middle metal ground plate 20, the fourth dielectric substrate 4, and the fifth metal floor are all 10 mm. The longitudinal dimension l of the first metal ground plate 1 and the second dielectric substrate 2 are both 7.4 mm. The longitudinal dimension p of the middle metal ground plate 20, the fourth dielectric substrate 4, and the fifth metal floor are all 11.4 mm.

[0063] The thickness of the first metal floor, the third interdigital resonator 3, and the fifth metal floor is 0.035 mm. The relative dielectric constant of the second dielectric substrate 2 and the fourth dielectric substrate 4 is 3.55 and the thickness is 0.3 mm.

[0064] The diameter of the ground through-hole 6 is 0.2 mm.

[0065] Furthermore, the transverse dimension l of the top through groove 7 is u The longitudinal dimension w is 7.644mm. u 3.2mm;

[0066] The longitudinal distance g between the metal strip III11 and the first metal ground plate 1 u The longitudinal distance d between the metal strip III11 and the metal strip IV12 is 0.436 mm. u The longitudinal distance d between the metal strip IV12 and the metal strip V13 is 0.179 mm. l 0.16mm;

[0067] Transverse dimensions S of metal strips III11, IV12, and V13 u Both are 6.944mm, and the longitudinal dimension w l Both are 0.33mm.

[0068] Furthermore, the opening dimension lc of the two concave ground plates is 7.644 mm, and the longitudinal dimension w c 5mm;

[0069] The transverse dimension S0 of the grounded coplanar waveguide 17 is 0.6 mm, the longitudinal dimension l1 is 1.5 mm, and the transverse spacing g0 between the grounded coplanar waveguide 17 and the middle metal ground plate 20 is 0.379 mm;

[0070] The lateral dimension w0 of the tapped stripline 16 is 0.3 mm, and the longitudinal dimension l0 is 2.261 mm;

[0071] The lateral spacing d1 between the resonator I14 and the middle metal ground plate 20 is 0.121 mm, the lateral spacing d2 between the resonator II18 and the middle metal ground plate 20 is 1.147 mm, the lateral spacing d3 between the resonator III15 and the middle metal ground plate 20 is 1.122 mm, and the lateral spacing d4 between the resonator IV19 and the middle metal ground plate 20 is 1.113 mm.

[0072] The longitudinal spacing c1 between resonator I14 and resonator II18 is 0.08 mm, the longitudinal spacing c2 between resonator II18 and resonator III15 is 0.138 mm, and the longitudinal spacing c3 between resonator III15 and resonator IV19 is 0.171 mm;

[0073] The longitudinal dimension w0 of resonator I14, resonator II18, resonator III15, and resonator IV19 is 0.3 mm.

[0074] Furthermore, the horizontal dimension l of the bottom through groove 21 is d The longitudinal dimension w is 2.96mm. d 3.03mm;

[0075] The longitudinal distance g between the metal strip I24 and the fifth metal ground plate 5 l The longitudinal distance g between the metal strip II23 and the fifth metal ground plate 5 is 0.085 mm. d The longitudinal distance d between the metal strip I24 and the metal strip II23 is 0.05 mm. d 0.67mm;

[0076] Transverse dimension S of metal strip I24 and metal strip II23 d Both are 2.3mm, longitudinal dimension w l Both are 0.33mm.

[0077] like Figure 13 As shown, the size limitation of the above structure ensures that the bandpass filter has 16 combinations with excellent passband performance, with absolute bandwidth (-3dB) ranging from 2.29GHz to 5.68GHz, relative bandwidth ranging from 38% to 90%, center frequency around 6GHz, wide adjustable bandwidth range, and flexible discrete bandwidth control capability.

[0078] The filter works as follows:

[0079] The signal is fed into the grounded coplanar waveguide 17 of the third-layer interdigital resonator 3 through the SMA head, and then fed into the grounded coplanar waveguide 17 at the other end after passing through resonator I14, resonator II18, resonator III15, resonator IV19, resonator III15, resonator II18, and resonator I14, and then output through the SMA.

[0080] At the same time, if Figure 11 and Figure 12 As shown, FPGA is used to control the on-off of the diode groups of the first metal ground plate 1 and the fifth metal ground plate 5 to form different on-off combinations to change the self-capacitance and mutual capacitance of the coupled transmission line, thereby changing the bandwidth of the filter and realizing the discrete adjustable bandwidth function. Specifically: the 10 output GPIO ports of the FPGA are connected to the corresponding 10 ports of the filter (port1-port10), and the order of the ports corresponds to the coding order. Among them, port 1 is always connected to a low level. When other ports are connected to a high level, the diode corresponding to the port is turned on (the corresponding metal strip is grounded); when other ports are connected to a low level, the diode corresponding to the port is turned off (the corresponding metal strip is not grounded), thereby controlling the state of the metal strip to achieve the purpose of coding and regulating the bandwidth of the filter. For example, to ground the metal strips I24 and V13 and keep the others ungrounded, you only need to turn on diodes I25 and V10, that is, connect port 1 to a low level, and connect port 6, port 7, and port 8 to a high level. The code is: 0000011100000000 (0700), and so on.

[0081] The specific theory is as follows:

[0082] The relationship between the bandwidth and coupling coefficient of the coupled filter is as follows:

[0083]

[0084] where k nm is the coupling coefficient between the nth resonator and the mth resonator, BW is the absolute bandwidth of the filter, f0 is the center frequency of the filter, g n g m is the first low-pass prototype coefficient. For parallel coupled transmission lines, the coupling coefficient k nm It is inversely proportional to the spacing S between adjacent transmission lines, and the coupling coefficient k is easy to obtain nm with C nm It is directly proportional to C nn Inversely proportional.

[0085] like Figure 14 The figure shows the coupling capacitance diagram of two parallel coupled transmission lines a and b under the electric wall and magnetic wall, where the mutual capacitance satisfies the relationship: C ab =4(C fo '-C fe '), where C fo ' is the mutual coupling capacitance of the two transmission lines under the electric wall, C fe' is the edge capacitance when another coupling line exists under the magnetic wall; the self-capacitance of transmission line a (or b) satisfies: C a =4(C f +C p +C fe '), where C f is the fringe capacitance of a single transmission line in an uncoupled state, C p is the capacitance of a single transmission line to ground.

[0086] After the first metal ground plane 1 and the fifth metal ground plane 5 are grooved, if the metal strips of the first metal ground plane 1 and the fifth metal ground plane 5 are not grounded, the strip line will lose the metal ground, which will cause the edge capacitance C fe 'Decrease; at the same time, due to C p with C f The decrease of the self-capacitance of a single transmission line reduces, resulting in the mutual coupling capacitance C of the two transmission lines fo 'Increase. Eventually, the mutual capacitance C ab Increase, extending the bandwidth of the filter.

[0087] If the metal strips of the first and fifth metal ground planes 1 and 5 are grounded, the stripline has a metal ground, the opposite of being ungrounded. Therefore, by controlling the diodes connecting the metal ground planes and the metal strips, the grounding state of the metal strips can be changed, flexibly adjusting the filter bandwidth.

[0088] Taking the resonant frequency of two coupled transmission lines as an example, the equivalent circuit diagram is as follows: Figure 15 As shown;

[0089] Where L and C represent the self-inductance and self-capacitance of a single transmission line, C m Represents the coupling capacitor, and its high-frequency and low-frequency resonant frequencies can be expressed as:

[0090]

[0091] When the metal strips of the first metal ground plane 1 are not grounded, the mutual capacitance C m increases, the self-capacitance C decreases, and the mutual capacitance C m The increase is greater than the decrease in self-capacitance C. Therefore, the high-frequency resonant frequency f m Increase, low frequency resonant frequency f e Decreases, and f e The reduction is slightly lower than f m The increase in the bandwidth results in an increase in the center frequency and a slight shift of the center frequency to higher frequencies.

[0092] like Figure 16 The simulation S shown 21 In the parameter diagram, the horizontal axis represents the frequency and the vertical axis represents the S parameter in dB. Figure 17 The simulation S shown 11 Parameter diagram, the horizontal axis represents frequency, the vertical axis represents S parameters, the unit is dB.

[0093] Figure 16 and Figure 17 Figure 3 is the S-parameter diagram of 6 main states among the 16 states. The triangular solid line represents the S-parameter when all diodes are turned on; the square solid line represents the S-parameter when diode group II is disconnected and other tube groups are turned on; the circular solid line represents the S-parameter when diode group I, diode group II, and diode group V are disconnected and other tube groups are turned on; the inverted triangle solid line represents the S-parameter when diode group I, diode group IV, and diode group V are disconnected and other tube groups are turned on; the star solid line represents the S-parameter when diode group III, diode group IV, and diode group V are disconnected and other tube groups are turned on; the diamond solid line represents the S-parameter diagram when all diodes are cut off.

[0094] It can be seen that the center frequencies of the six curves are all around 6 GHz, and the -3dB bandwidth ranges from 2.29 GHz to 5.68 GHz. The insertion loss S 21 All above -1dB, return loss S 11 All are below -10dB, with good performance and a wide adjustable range.

Claims

1. A bandwidth-coded reconfigurable bandpass filter, characterized in that: It comprises a first metal grounding plate (1), a second dielectric substrate (2), a third interdigital resonator (3), a fourth dielectric substrate (4), and a fifth metal grounding plate (5) stacked in sequence; The bandpass filter is provided with a grounding through hole (6) which sequentially penetrates the first metal grounding plate (1), the second dielectric substrate (2), the third interdigital resonator (3), the fourth dielectric substrate (4), and the fifth metal grounding plate (5); A top through groove (7) is provided in the middle of the first metal grounding plate (1), a first metal strip group is provided in the top through groove (7), and the left and right sides of the first metal strip group are connected to the first metal grounding plate (1) via the first diode group; The third interdigital resonator (3) includes a middle metal ground plate (20), which is composed of concave ground plates that are symmetrically arranged and have openings facing each other. A resonator group is connected between the two concave ground plates. The upper and lower sides of the resonator group are respectively connected to a grounded coplanar waveguide (17) through a tapped stripline (16). The other end of the grounded coplanar waveguide (17) is connected to an SMA head. A bottom through slot (21) is provided in the middle of the fifth metal grounding plate (5), a fifth metal strip group is provided in the bottom through slot (21), and the left and right sides of the fifth metal strip group are connected to the fifth metal grounding plate (5) via a fifth diode group.

2. A bandwidth coded reconfigurable bandpass filter according to claim 1, characterized in that: The first layer of metal strip group includes a metal strip V (13), and metal strips IV (12) and metal strips III (11) are symmetrically distributed on the upper and lower sides of the metal strip V (13).

3. A bandwidth coded reconfigurable bandpass filter according to claim 2, characterized in that: The first layer diode group includes diode III (8), diode IV (9), and diode V (10). The left and right sides of metal strips III (11), metal strips IV (12), and metal strips V (13) are connected to the first layer metal ground plate (1) through diodes III (8), diodes IV (9), and diodes V (10), respectively.

4. The bandwidth coded reconfigurable bandpass filter according to claim 1, wherein: The resonator group includes a resonator IV (19), and resonators III (15), II (18), and I (14) are symmetrically distributed on the upper and lower sides of the resonator IV (19); the left end of the resonator I (14) is short-circuited and the right end is open, the right end of the resonator II (18) is short-circuited and the left end is open, and the left end of the resonator III (15) is short-circuited and the right end is open.

5. The bandwidth coded reconfigurable bandpass filter according to claim 1, wherein: The fifth layer of metal strip group includes metal strip I (24) and metal strip II (23). The bottom layer through groove (21) is divided into upper and lower parts by a partition in the middle. The metal strip I (24) and metal strip II (23) are symmetrically distributed in the upper and lower parts respectively. The fifth layer of diode group includes diode I (25) and diode II (22). The left and right sides of the metal strip I (24) and metal strip II (23) are connected to the fifth layer of metal ground plate (5) through diode I (25) and diode II (22) respectively.

6. The bandwidth coded reconfigurable bandpass filter according to claim 2, wherein: The transverse dimensions w of the first metal grounding plate (1), the second dielectric substrate (2), the middle metal grounding plate (20), the fourth dielectric substrate (4), and the fifth metal floor are all 10 mm, and the longitudinal dimensions l of the first metal grounding plate (1) and the second dielectric substrate (2) are all 7.4 mm; the longitudinal dimensions p of the middle metal grounding plate (20), the fourth dielectric substrate (4), and the fifth metal floor are all 11.4 mm. The first metal floor, the third interdigital resonator (3), and the fifth metal floor have a thickness of 0.035 mm, and the second dielectric substrate (2) and the fourth dielectric substrate (4) have a relative dielectric constant of 3.55 and a thickness of 0.3 mm. The diameter of the grounding through hole (6) is 0.2 mm.

7. The bandwidth coded reconfigurable bandpass filter according to claim 6, wherein: The transverse dimension l of the top through groove (7) u The longitudinal dimension w is 7.644mm. u 3.2mm; The longitudinal distance g between the metal strip III (11) and the first metal ground plate (1) u The longitudinal distance d between the metal strip III (11) and the metal strip IV (12) is 0.436 mm. u The longitudinal distance d between the metal strip IV (12) and the metal strip V (13) is 0.179 mm. l 0.16mm; Transverse dimensions S of metal strip III (11), metal strip IV (12), and metal strip V (13) u Both are 6.944mm, and the longitudinal dimension w l Both are 0.33mm.

8. The bandwidth coded reconfigurable bandpass filter according to claim 4, wherein: The opening dimension lc of the two concave ground plates is 7.644 mm, and the longitudinal dimension w c 5mm; The transverse dimension S0 of the grounded coplanar waveguide (17) is 0.6 mm, the longitudinal dimension l1 is 1.5 mm, and the transverse spacing g0 between the grounded coplanar waveguide (17) and the middle metal ground plate (20) is 0.379 mm; The lateral dimension w0 of the tapped stripline (16) is 0.3 mm, and the longitudinal dimension l0 is 2.261 mm; The lateral spacing d1 between the resonator I (14) and the middle metal ground plate (20) is 0.121 mm, the lateral spacing d2 between the resonator II (18) and the middle metal ground plate (20) is 1.147 mm, the lateral spacing d3 between the resonator III (15) and the middle metal ground plate (20) is 1.122 mm, and the lateral spacing d4 between the resonator IV (19) and the middle metal ground plate (20) is 1.113 mm; The longitudinal spacing c1 between resonator I (14) and resonator II (18) is 0.08 mm, the longitudinal spacing c2 between resonator II (18) and resonator III (15) is 0.138 mm, and the longitudinal spacing c3 between resonator III (15) and resonator IV (19) is 0.171 mm; The longitudinal dimension w0 of resonator I (14), resonator II (18), resonator III (15), and resonator IV (19) is 0.3 mm.

9. The bandwidth coded reconfigurable bandpass filter according to claim 5, wherein: The horizontal dimension l of the bottom through groove (21) d The longitudinal dimension w is 2.96mm. d 3.03mm; The longitudinal distance g between the metal strip I (24) and the fifth metal ground plate (5) l The longitudinal distance g between the metal strip II (23) and the fifth metal ground plate (5) is 0.085 mm. d The longitudinal distance d between the metal strip I (24) and the metal strip II (23) is 0.05 mm. d 0.67mm; Transverse dimension S of metal strip I (24) and metal strip II (23) d Both are 2.3mm, longitudinal dimension w l Both are 0.33mm.

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