CN113972455B - Mechanically tunable low pass filter - Google Patents
Mechanically tunable low pass filter Download PDFInfo
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- CN113972455B CN113972455B CN202111408904.4A CN202111408904A CN113972455B CN 113972455 B CN113972455 B CN 113972455B CN 202111408904 A CN202111408904 A CN 202111408904A CN 113972455 B CN113972455 B CN 113972455B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P1/00—Auxiliary devices
- H01P1/20—Frequency-selective devices, e.g. filters
- H01P1/201—Filters for transverse electromagnetic waves
- H01P1/203—Strip line filters
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Abstract
The invention discloses a mechanically adjustable low-pass filter, which comprises a metal cavity, a sliding block, a PCB (printed circuit board) and a transmission device, wherein the metal cavity is provided with a first end and a second end; the PCB is arranged below the sliding block; the sliding block slides along the length direction of the PCB through a transmission device at one end of the cavity body; the PCB comprises a lower dielectric layer and a metal conducting strip layer attached to the upper surface of the dielectric layer; the upper metal conductive tape layer consists of a first input/output end, a second input/output end and a plurality of high-low impedance transmission lines; the sliding block is provided with a plurality of metal raised lines which respectively correspond to the high-low impedance transmission lines in the longitudinal position; the slide block is pushed to move to change the coverage area of the raised strips on the slide block and the low-impedance transmission lines and the high-impedance transmission lines of the low-pass filter, so that the equivalent capacitance inductance value is changed to achieve the purpose of adjusting the cut-off frequency of the low-pass filter. The invention has the advantages of large adjusting range, high adjusting resolution and simple adjusting mode.
Description
Technical Field
The invention discloses a mechanical adjustable low-pass filter, and belongs to the technical field of basic electrical elements.
Background
The filter is one of the key devices in radar, communication and measurement systems, and has the function of allowing signals of a certain part of frequencies to pass smoothly, and allowing signals of another part of frequencies to be greatly suppressed. With the continuous development of mobile communication technology and the continuous emergence of wireless communication technologies such as WCDMA, WLANs and the like, most of them are concentrated in the low frequency band of the radio frequency and microwave frequency bands, which makes the spectrum resources particularly crowded. The passband of the traditional microstrip filter can not be flexibly adjusted, and the defect of fixed performance exists. In order to adapt to different frequency bands, conventionally, a plurality of filters are used, and a switch is used for switching the frequency bands, but the disadvantage is obvious that more switches and filters are needed. Therefore, the study of tunable filters provides a good solution to this problem. The filter is used in communication equipment, the frequency and the bandwidth of the filter have good flexibility to the whole system through external control, meanwhile, the use of the number of the filters is reduced, and the development requirements of a wireless communication system are well met.
Disclosure of Invention
Aiming at the defects of the background technology, the invention provides a mechanical adjustable low-pass filter, realizes an adjustable filter with large adjustment range of low frequency and cut-off frequency and flexible adjustment, and solves the technical problem that the conventional low-frequency filter is inconvenient to adjust. The invention changes the coverage area of the convex strip on the sliding block and the low impedance transmission line and the high impedance transmission line of the low-pass filter by pushing the sliding block to move, thereby changing the inductance value of the equivalent capacitor and achieving the purpose of adjusting the cut-off frequency of the low-pass filter.
The invention adopts the following technical scheme for realizing the aim of the invention:
a mechanical adjustable low-pass filter comprises a metal cavity, a sliding block, a PCB and a transmission device;
the metal cavity is in a cuboid shape and consists of a cavity cover plate and a cavity main body; the cavity body comprises a first cavity short side plate, a second cavity short side plate, two long side plates and a bottom plate; a through hole is formed in the short side plate of the second cavity;
symmetrical grooves are formed in the two long side plates of the cavity body and used for inserting the sliding blocks; the transmission device consists of a screw and a high knurled nut, one end of the screw is fixedly connected with the sliding block, the other end of the screw extends out of the metal cavity from a through hole on the short side plate of the second cavity, the part of the screw extending out of the metal cavity is provided with an external thread, and the external thread is matched with the internal thread of the high knurled nut; the sliding block slides along the length direction of the PCB through a transmission device at one end of the cavity body; the PCB is arranged below the sliding block;
step-shaped bulges are arranged at the joints of the two long side plates and the bottom plate of the cavity body and used for arranging and fixing the low-pass filter PCB; the PCB comprises a lower dielectric layer and a metal conducting strip layer attached to the upper surface of the dielectric layer; the upper metal conductive tape layer consists of a first input/output end, a second input/output end and a plurality of high-low impedance transmission lines; the high-impedance transmission line and the low-impedance line are alternately arranged between the first input/output end and the second input/output end, and the high-impedance transmission line is bent; the low-impedance transmission line is in a rectangular strip shape; the sliding block is provided with a plurality of metal raised lines which respectively correspond to the high-low impedance transmission lines in the longitudinal position; the distance between the PCB and the slider is greater than the thickness of the metal raised line; the characteristic impedance is changed by changing the coverage area of the metal convex strip on the transmission line through longitudinally sliding the slide block, so that the cut-off frequency of the low-pass filter is changed.
Furthermore, the plurality of high-impedance transmission lines comprise a first high-impedance transmission line and a second high-impedance transmission line, and the plurality of low-impedance transmission lines comprise a first low-impedance transmission line, a second low-impedance transmission line and a third low-impedance transmission line;
the first input/output end, the first low-impedance transmission line, the first high-impedance transmission line, the second low-impedance transmission line, the second high-impedance transmission line, the third low-impedance transmission line and the second input/output end are connected in sequence; the high-impedance transmission line and the low-impedance transmission line are arranged in parallel, the high-impedance transmission line comprises a main transmission line and two corners, the two corners are connected with the low-impedance transmission line, and corner cutting treatment is carried out on the corners; the first input/output end and the second input/output end are positioned on the same horizontal line and are symmetrical about a central axis in the length direction of the PCB, the central axis is superposed with the central axis in the length direction of the second low-impedance transmission line, the corresponding first low-impedance transmission line and the corresponding third low-impedance transmission line are symmetrical about the central axis, and the first high-impedance transmission line and the second high-impedance transmission line are also symmetrical about the central axis.
Furthermore, the first input/output end and the second input/output end are composed of a microstrip line and a suspension line; the length of the microstrip line is 0.55mm, and the width of the microstrip line is 4 mm; the length of the suspension line is 14.97mm, and the width is 6 mm.
Furthermore, the length of the low-impedance transmission line and the length of the high-impedance transmission line are both smaller than one fourth of the working wavelength, and the width of the low-impedance transmission line is larger than that of the high-impedance transmission line.
Further, the first low impedance transmission line has a length of 47.59mm and a width of 8 mm; the length of the second low-impedance transmission line is 47.59mm, and the width of the second low-impedance transmission line is 20 mm; the first high impedance transmission line is divided into three sections, the width of the three sections is 2.5mm, and the total length of the three sections is 35 mm.
Further, the plurality of metal ribs comprise; the first inductance adjusting metal strip, the second inductance adjusting metal strip, the first capacitance adjusting metal strip, the second capacitance adjusting metal strip and the third capacitance adjusting metal strip;
the first inductance adjusting metal strip and the second inductance adjusting metal strip correspond to the first high-impedance transmission line and the second high-impedance transmission line in the longitudinal position and are symmetrical about a central axis in the length direction of the sliding block; the first capacitance adjusting metal strip and the third capacitance adjusting metal strip correspond to the first low-impedance transmission line and the third low-impedance transmission line in the longitudinal position and are symmetrical about a central axis in the length direction of the sliding block, and the central axis in the length direction of the sliding block is superposed with the central axis in the length direction of the second capacitance adjusting metal strip; the second capacitance adjusting metal strip corresponds to the second low-impedance transmission line in the longitudinal position;
the widths of the first inductance regulating metal strip and the second inductance regulating metal strip are larger than the widths of the first high-impedance transmission line and the second high-impedance transmission line; the widths of the first capacitance adjusting metal strip and the third capacitance adjusting metal strip are equal to the widths of the first low-impedance transmission line and the third low-impedance transmission line; the width of the second capacitance adjusting metal strip is equal to that of the second low-impedance transmission line.
When the sliding block is at an initial position, the first inductance adjusting metal strip and the second inductance adjusting metal strip completely cover the main transmission lines of the first high-impedance transmission line and the second high-impedance transmission line respectively, and the first capacitance adjusting metal strip, the second capacitance adjusting metal strip and the third capacitance adjusting metal strip do not cover the first low-impedance transmission line, the second low-impedance transmission line and the third low-impedance transmission line respectively;
after the sliding block starts to slide, the areas of the first inductance adjusting metal strip and the second inductance adjusting metal strip, which cover the first high-impedance transmission line and the second high-impedance transmission line, are gradually reduced, the areas of the first capacitance adjusting metal strip, the second capacitance adjusting metal strip and the third capacitance adjusting metal strip, which cover the first low-impedance transmission line, and the areas of the second low-impedance transmission line and the third low-impedance transmission line, which are gradually increased.
Further, the first inductance adjusting metal strip and the second inductance adjusting metal strip are 58.735mm in length and 4.5mm in width, the first capacitance adjusting metal strip and the third capacitance adjusting metal strip are 56.31mm in length and 8mm in width, and the second capacitance adjusting metal strip is 78.81mm in length and 20mm in width; the thickness of each of the plurality of metal strips was 7 mm.
Furthermore, a distance of 0.7mm is reserved between the PCB and the metal strip on the sliding block; the distance between the middle part of the PCB and the bottom plate of the cavity body is 3.048 mm; the dielectric constant of the lower dielectric plate of the PCB is 3.66, and the thickness of the lower dielectric plate is 0.254 mm.
Further, the grooves on the long side plates of the cavity body are separated from the cavity bottom plate 10.302mm, and the width of the grooves is 2 mm.
Furthermore, a through hole is formed in the sliding block and used for being connected with the screw rod, and the position of the through hole in the sliding block corresponds to the position of the through hole in the short side plate of the second cavity.
By adopting the technical scheme, the invention has the following beneficial effects:
(1) the degree of freedom of the longitudinal sliding of the sliding block is large, and the sensitivity of the precision of the cut-off frequency adjustment to the sliding distance is low.
(2) The cut-off frequency adjusting range is large, and the mechanical adjustable low-pass filter can achieve the cut-off frequency adjusting range of 490MHz on the basis of the cut-off frequency of 1 GHz.
(3) The slider can make electric capacity and inductance increase simultaneously or reduce through the control of screw rod, and the accommodation range is wide and the passband return loss keeps better in whole regulation process.
Drawings
Fig. 1 is a schematic diagram of the construction of the mechanically tunable low-pass filter of the present invention.
Fig. 2 is a front view of the PCB of fig. 1.
FIG. 3 is a schematic view of the slider sliding; where figure 3a shows a slider sliding of 0mm, figure 3b shows a slider sliding of 10mm and figure 3c shows a slider sliding of 30 mm.
Fig. 4 is a schematic structural view of the slider in fig. 1.
Fig. 5 is a frequency response plot of S11 for the mechanically tunable low pass filter of the present invention.
Fig. 6 is a frequency response curve of S21 for the mechanically tunable low pass filter of the present invention.
The reference numbers in the figures illustrate: 1. cavity apron, 2, the slider, 3, first short cavity curb plate, 4, the PCB board, 5, the cavity main part, 6, the screw rod, 7, the short cavity curb plate of second, 8, high knurling nut, 9, first input/output port, 10, second input/output port, 11, first low impedance transmission line, 12, first high impedance transmission line, 13, second low impedance transmission line, 14, the high impedance transmission line of second, 15, the third low impedance transmission line, 16, first inductance regulation metal strip, 17, second inductance regulation metal strip, 18, first capacitance regulation metal strip, 19, second capacitance regulation metal strip, 20, the third capacitance regulation metal strip.
Detailed Description
The technical scheme of the invention is explained in detail in the following with reference to the attached drawings.
As shown in fig. 1, the mechanically tunable low-pass filter disclosed by the invention comprises a metal cavity, a slider 2, a PCB 4 and a transmission device;
the metal cavity is cuboid and consists of a cavity cover plate 1 and a cavity body 5; the cavity body 5 comprises a first cavity short side plate 3, a second cavity short side plate 7, two long side plates and a bottom plate; a through hole is formed in the short side plate 7 of the second cavity;
symmetrical grooves are formed in the two long side plates of the cavity body 5 and used for inserting the sliding blocks 2; the groove on the long side plate of the cavity body 5 is 10.302mm away from the cavity bottom plate, and the width of the groove is 2 mm. The transmission device consists of a screw 6 and a high knurled nut 8, one end of the screw 6 is fixedly connected with the sliding block 2, the other end of the screw 6 extends out of the metal cavity from a through hole on a short side plate 7 of the second cavity, the part of the screw 6 extending out of the metal cavity is provided with an external thread, and the external thread is matched with the internal thread of the high knurled nut 8; and a through hole is formed in the sliding block 2 and is used for being connected with the screw rod 6, and the position of the through hole in the sliding block 2 corresponds to the position of the through hole in the short side plate 7 of the second cavity. The sliding block 2 slides along the length direction of the PCB 4 through a transmission device at one end of the cavity body 5; the change of the position of the slider 2 can affect the change of the capacitance inductance between the microstrip line on the PCB 4 and the slider, thereby changing the characteristic impedance to affect the cut-off frequency of the low-pass filter, meanwhile, two sides of the PCB 4 are fixed on the cavity body 5, and a cavity, namely a suspension microstrip line structure, is formed between the middle part and the groove of the cavity body 5. The PCB 4 is arranged below the sliding block 2; step-shaped bulges are arranged at the joints of the two long side plates and the bottom plate of the cavity body 5 and are used for arranging and fixing the low-pass filter PCB 4;
as shown in fig. 2, the PCB 4 includes a lower dielectric layer and a metal tape layer attached to an upper surface of the dielectric layer; the upper metal conductive tape layer consists of a first input/output end 9, a second input/output end 10 and a plurality of high-low impedance transmission lines; the plurality of high impedance transmission lines comprise a first high impedance transmission line 12 and a second high impedance transmission line 14, and the plurality of low impedance transmission lines comprise a first low impedance transmission line 10, a second low impedance transmission line 13 and a third low impedance transmission line 15; the high impedance transmission line and the low impedance line are alternately arranged between the first input/output end 9 and the second input/output end 10, and the first input/output end 9, the first low impedance transmission line 11, the first high impedance transmission line 12, the second low impedance transmission line 13, the second high impedance transmission line 14, the third low impedance transmission line 15 and the second input/output end 10 are sequentially connected; the high-impedance transmission line is bent; the low-impedance transmission line is in a rectangular strip shape; the high-impedance transmission line and the low-impedance transmission line are arranged in parallel, the high-impedance transmission line comprises a main transmission line and two corners, the two corners are connected with the low-impedance transmission line, and corner cutting treatment is carried out on the corners; the first input/output end 9 and the second input/output end 10 are located on the same horizontal line and are symmetrical with respect to a central axis in the length direction of the PCB 4, the central axis coincides with a central axis in the length direction of the second low-impedance transmission line 13, the corresponding first low-impedance transmission line 11 and the third low-impedance transmission line 15 are symmetrical with respect to the central axis, and the first high-impedance transmission line 12 and the second high-impedance transmission line 14 are also symmetrical with respect to the central axis. The length of the low-impedance transmission line and the length of the high-impedance transmission line are both smaller than one fourth of the working wavelength, and the width of the low-impedance transmission line is larger than that of the high-impedance transmission line.
A plurality of metal raised lines are arranged on the sliding block 2, and the metal raised lines are respectively corresponding to the high-low impedance transmission lines in the longitudinal position. The distance between the PCB 4 and the slider 2 is greater than the thickness of the metal raised line;
the plurality of metal convex strips comprise; a first inductance adjusting metal strip 16, a second inductance adjusting metal strip 17, a first capacitance adjusting metal strip 18, a second capacitance adjusting metal strip 19 and a third capacitance adjusting metal strip 20;
the first inductance adjusting metal strip 16 and the second inductance adjusting metal strip 17 correspond to the first high-impedance transmission line 12 and the second high-impedance transmission line 14 in the longitudinal position and are symmetrical about a central axis of the sliding block 2 in the length direction; the first capacitance adjusting metal strip 18 and the third capacitance adjusting metal strip 20 correspond to the first low-impedance transmission line 11 and the third low-impedance transmission line 15 in the longitudinal position and are symmetrical about a central axis of the sliding block 2 in the length direction, and the central axis of the sliding block 2 in the length direction is superposed with the central axis of the second capacitance adjusting metal strip 19 in the length direction; the second capacitance adjustment metal strip 19 corresponds to the second low impedance transmission line 13 in longitudinal position; the widths of the first inductance-adjusting metal strip 16 and the second inductance-adjusting metal strip 17 are greater than the widths of the first high-impedance transmission line 12 and the second high-impedance transmission line 14; the widths of the first capacitance adjustment metal strip 18 and the third capacitance adjustment metal strip 20 are equal to the widths of the first low-impedance transmission line 11 and the third low-impedance transmission line 15; the width of the second capacitance adjustment metal strip 19 is equal to the width of the second low impedance transmission line 13.
When the slider 2 is at the initial position, the first inductance-adjusting metal strip 16 and the second inductance-adjusting metal strip 17 completely cover the main transmission lines of the first high-impedance transmission line 12 and the second high-impedance transmission line 14, respectively, and the first capacitance-adjusting metal strip 18, the second capacitance-adjusting metal strip 19 and the third capacitance-adjusting metal strip 20 do not cover the first low-impedance transmission line 10, the second low-impedance transmission line 13 and the third low-impedance transmission line 15;
after the slider 2 starts to slide, the areas of the first inductance adjusting metal strip 16 and the second inductance adjusting metal strip 17 covering the first high-impedance transmission line 12 and the second high-impedance transmission line 14 are gradually reduced, the areas of the first capacitance adjusting metal strip 18, the second capacitance adjusting metal strip 19 and the third capacitance adjusting metal strip 20 covering the first low-impedance transmission line 10 are gradually increased, and the areas of the second low-impedance transmission line 13 and the third low-impedance transmission line 15 are gradually increased.
As shown in fig. 2, the first input/output terminal 9 and the second input/output terminal 10 are formed of transmission lines having different widths at both ends because the both sides of the PCB are in contact with the cavity and the distance between the both sides and the middle portion and the body of the cavity is different, and the width of the 50 Ω line needs to be recalculated.
In the embodiment, a mechanical adjustable low-pass filter with a cut-off frequency adjusting range of 0.68-1GHz is designed, and a distance of 0.7mm is formed between the PCB 4 and the metal strip on the slider 2; the distance between the middle part of the PCB 4 and the bottom plate of the cavity body 5 is 3.048 mm; the dielectric constant of the lower dielectric plate of the PCB 4 is 3.66, and the thickness is 0.254 mm.
The first input/output end 9 and the second input/output end 10 are composed of a microstrip line and a suspension line; the length of the microstrip line is 0.55mm, and the width of the microstrip line is 4 mm; the length of the suspension wire is 14.97mm, and the width of the suspension wire is 6 mm; the length of the first low-impedance transmission line 11 is 47.59mm, and the width is 8 mm; the second low impedance transmission line 13 has a length of 47.59mm and a width of 20 mm; the first high impedance transmission line 12 is divided into three sections with a width of 2.5mm and a total length of 35 mm.
FIG. 3 is a schematic drawing of slider sliding, 0mm, 10mm and 30mm for slider sliding, respectively.
Fig. 4 shows a slider structure, respectively illustrating the positions of the lc adjusting metal strips. The first inductance adjusting metal strip 16 and the second inductance adjusting metal strip 17 are 58.735mm in length and 4.5mm in width, the first capacitance adjusting metal strip 18 and the third capacitance adjusting metal strip 20 are 56.31mm in length and 8mm in width, and the second capacitance adjusting metal strip 19 is 78.81mm in length and 20mm in width; the thickness of each of the plurality of metal strips was 7 mm.
| S of filter 11 The | amplitude response, the reflection characteristic response. FIG. 5 shows the | S of the mechanically tunable low-pass filter of the present invention at 0.1-2GHz 11 And the curve of the I frequency response graph is shown schematically, S is the sliding distance of the sliding block in the cavity, the return loss of the sliding block can reach below-10 dB, the range of the cut-off frequency is 0.62-1.11GHz, and the cut-off frequency can be changed to 490 MHz.
| S of filter 21 The | amplitude response, the transfer characteristic response. FIG. 6 shows the | S of the mechanically tunable low-pass filter of the present invention at 0.1-2.0GHz 21 The curve of the | frequency response graph is schematic, S is the sliding distance of the sliding block in the cavityThe insertion loss is less than 0.2dB, the range of cut-off frequency is 0.62-1.11GHz, and the cut-off frequency can be changed to 490 MHz.
It should be noted that this embodiment only takes the form of a fifth order filter, and changes the cutoff frequency of the filter by changing the characteristic impedance of the transmission line with a slider above the suspension line.
The working principle of the invention is as follows: when the sliding block slides, each metal raised line covers a section of high-impedance line or low-impedance line on the PCB in whole or in part respectively. When the sliding block slides longitudinally, the coverage area of the convex strip covering the high-impedance transmission line and the high-impedance transmission line is reduced, so that the equivalent characteristic impedance of the high-impedance transmission line is increased, namely the equivalent inductance value is increased; meanwhile, the coverage area between the convex strip covering the low-impedance transmission line and the low-impedance transmission line is increased, so that the equivalent impedance of the high-impedance transmission line is reduced, namely the equivalent capacitance value is increased. The equivalent inductance and the equivalent capacitance are simultaneously increased, so that the cut-off frequency of the low-pass filter is reduced, good pass-band and stop-band characteristics are kept, and the mechanical adjustability of the cut-off frequency of the low-pass filter is realized.
While the foregoing is directed to the preferred embodiment of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
Claims (8)
1. A mechanical adjustable low-pass filter is characterized by comprising a metal cavity, a sliding block (2), a PCB (printed circuit board) (4) and a transmission device;
the metal cavity is cuboid and consists of a cavity cover plate (1) and a cavity body (5); the cavity body (5) comprises a first cavity short side plate (3), a second cavity short side plate (7), two long side plates and a bottom plate; a through hole is formed in the short side plate (7) of the second cavity;
symmetrical grooves for inserting the sliding blocks (2) are formed in the two long side plates of the cavity body (5); the transmission device consists of a screw rod (6) and a high knurled nut (8), one end of the screw rod (6) is fixedly connected with the sliding block (2), the other end of the screw rod (6) extends out of the metal cavity from a through hole on a short side plate (7) of the second cavity, the part of the screw rod (6) extending out of the metal cavity is provided with an external thread, and the external thread is matched with the internal thread of the high knurled nut (8); the sliding block (2) slides along the length direction of the PCB (4) through a transmission device at one end of the cavity body (5); the PCB (4) is arranged below the sliding block (2);
step-shaped bulges are arranged at the joints of the two long side plates and the bottom plate of the cavity body (5) and used for arranging and fixing the low-pass filter PCB (4); the PCB (4) comprises a lower dielectric layer and a metal conducting strip layer attached to the upper surface of the dielectric layer; the upper metal conducting strip layer consists of a first input/output end (9), a second input/output end (10) and a plurality of high-low impedance transmission lines; the high-impedance transmission line and the low-impedance line are alternately arranged between the first input/output end (9) and the second input/output end (10), and the high-impedance transmission line is bent; the low-impedance transmission line is in a rectangular strip shape; the slider (2) is provided with a plurality of metal raised strips, the metal raised strips respectively correspond to the high-low impedance transmission lines in the longitudinal position, and the slider (2) is longitudinally slid to change the coverage area of the metal raised strips on the transmission lines so as to change the characteristic impedance and further change the cut-off frequency of the low-pass filter; the distance between the PCB (4) and the slider (2) is greater than the thickness of the metal convex strip; the plurality of high impedance transmission lines comprise a first high impedance transmission line (12) and a second high impedance transmission line (14), and the plurality of low impedance transmission lines comprise a first low impedance transmission line (11), a second low impedance transmission line (13) and a third low impedance transmission line (15);
the first input/output end (9), the first low-impedance transmission line (11), the first high-impedance transmission line (12), the second low-impedance transmission line (13), the second high-impedance transmission line (14), the third low-impedance transmission line (15) and the second input/output end (10) are connected in sequence; the high-impedance transmission line and the low-impedance transmission line are arranged in parallel, the high-impedance transmission line comprises a main transmission line and two corners, the two corners are connected with the low-impedance transmission line, and corner cutting treatment is carried out on the corners; the first input/output end (9) and the second input/output end (10) are positioned on the same horizontal line and are symmetrical about a central axis of the PCB (4) in the length direction, the central axis is superposed with a central axis of the second low-impedance transmission line (13) in the length direction, the corresponding first low-impedance transmission line (11) and the corresponding third low-impedance transmission line (15) are symmetrical about the central axis, and the first high-impedance transmission line (12) and the second high-impedance transmission line (14) are also symmetrical about the central axis; the plurality of metal convex strips comprise; a first inductance adjusting metal strip (16), a second inductance adjusting metal strip (17), a first capacitance adjusting metal strip (18), a second capacitance adjusting metal strip (19) and a third capacitance adjusting metal strip (20);
the first inductance adjusting metal strip (16) and the second inductance adjusting metal strip (17) correspond to the first high-impedance transmission line (12) and the second high-impedance transmission line (14) in the longitudinal position and are symmetrical about a central axis of the sliding block (2) in the length direction; the first capacitance adjusting metal strip (18) and the third capacitance adjusting metal strip (20) correspond to the first low-impedance transmission line (11) and the third low-impedance transmission line (15) in the longitudinal position and are symmetrical about a central axis of the sliding block (2) in the length direction, and the central axis of the sliding block (2) in the length direction is superposed with the central axis of the second capacitance adjusting metal strip (19) in the length direction; the second capacitance adjusting metal strip (19) corresponds to the second low-impedance transmission line (13) in the longitudinal position;
the widths of the first inductance adjusting metal strip (16) and the second inductance adjusting metal strip (17) are larger than the widths of the first high-impedance transmission line (12) and the second high-impedance transmission line (14); the widths of the first capacitance adjusting metal strip (18) and the third capacitance adjusting metal strip (20) are equal to the widths of the first low-impedance transmission line (11) and the third low-impedance transmission line (15); the width of the second capacitance adjusting metal strip (19) is equal to that of the second low-impedance transmission line (13);
when the sliding block (2) is at an initial position, the first inductance adjusting metal strip (16) and the second inductance adjusting metal strip (17) completely cover the main transmission lines of the first high-impedance transmission line (12) and the second high-impedance transmission line (14) respectively, and the first capacitance adjusting metal strip (18), the second capacitance adjusting metal strip (19) and the third capacitance adjusting metal strip (20) do not cover the first low-impedance transmission line (11), the second low-impedance transmission line (13) and the third low-impedance transmission line (15);
after the sliding block (2) starts to slide, the areas of the first inductance adjusting metal strip (16) and the second inductance adjusting metal strip (17) covering the first high-impedance transmission line (12) and the second high-impedance transmission line (14) are gradually reduced, the areas of the first capacitance adjusting metal strip (18), the second capacitance adjusting metal strip (19) and the third capacitance adjusting metal strip (20) covering the first low-impedance transmission line (11), and the areas of the second low-impedance transmission line (13) and the third low-impedance transmission line (15) are gradually increased.
2. A mechanically tunable low-pass filter according to claim 1, characterized in that the first input/output (9) and the second input/output (10) are made up of a length of microstrip line and a length of suspended line; the length of the microstrip line is 0.55mm, and the width of the microstrip line is 4 mm; the suspension line is 14.97mm long and 6mm wide.
3. A mechanically tunable low pass filter according to claim 1, wherein the low impedance transmission line and the high impedance transmission line are each less than one quarter of the operating wavelength long, and the width of the low impedance transmission line is greater than the width of the high impedance transmission line.
4. A mechanically tunable low pass filter according to claim 3, characterised in that the first low impedance transmission line (11) has a length of 47.59mm and a width of 8 mm; the length of the second low impedance transmission line (13) is 47.59mm, and the width is 20 mm; the first high impedance transmission line (12) is divided into three sections, the width of the three sections is 2.5mm, and the total length of the three sections is 35 mm.
5. A mechanically tunable low-pass filter according to claim 4, characterized in that the first (16) and second (17) inductively tunable metal strips are 58.735mm in length and 4.5mm in width, the first (18) and third (20) capacitively tunable metal strips are 56.31mm in length and 8mm in width, and the second (19) capacitively tunable metal strip is 78.81mm in length and 20mm in width; the thickness of each of the plurality of metal strips was 7 mm.
6. A mechanically tunable low pass filter according to claim 5, characterized in that there is a spacing of 0.7mm between the PCB board (4) and the metal strips on the slider (2); the distance between the middle part of the PCB (4) and the bottom plate of the cavity body (5) is 3.048 mm; the dielectric constant of the lower dielectric plate of the PCB (4) is 3.66, and the thickness of the lower dielectric plate is 0.254 mm.
7. A mechanically tunable low pass filter according to claim 1, wherein the grooves on the long side plates of the cavity body (5) are distant 10.302mm from the cavity bottom plate, the groove width being 2 mm.
8. A mechanically tunable low pass filter according to claim 1, wherein the slide (2) has a through hole for connection to a threaded rod (6), the position of the through hole in the slide (2) corresponding to the position of the through hole in the short side plate (7) of the second cavity.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101150215A (en) * | 2006-09-22 | 2008-03-26 | 鸿富锦精密工业（深圳）有限公司 | Filter |
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| DE3382762T2 (en) * | 1982-05-10 | 1995-05-04 | Oki Electric Ind Co Ltd | Dielectric filter. |
| EP1119070B1 (en) * | 1995-11-16 | 2003-08-27 | NGK Spark Plug Co. Ltd. | Dielectric filter and method of adjusting central frequency of the same |
| CN102610878B (en) * | 2011-09-30 | 2014-06-18 | 电子科技大学 | Coaxial low-pass filter |
| CN105161797B (en) * | 2015-07-15 | 2018-03-02 | 安徽四创电子股份有限公司 | One kind miniaturization dielectric phase shifter |
| CN206806478U (en) * | 2017-03-30 | 2017-12-26 | 湖北大学 | It is a kind of to load T-shaped minor matters in parallel and the Microstrip Low-Pass of defect ground structure |
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| CN101150215A (en) * | 2006-09-22 | 2008-03-26 | 鸿富锦精密工业（深圳）有限公司 | Filter |
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