Digital selectable band-pass filter based on loaded capacitor structure

Abstract

The utility model discloses a digital selectable band-pass filter based on a loading type capacitor structure, which belongs to the field of filters, and comprises an input microstrip line, an output microstrip line and a direct current port which are arranged on a substrate and are sequentially connected, a first frequency path and a second frequency path are respectively connected between the input microstrip line and the output microstrip line, the first frequency path comprises a first switch, a loaded capacitor network and a second switch which are connected in sequence; the second frequency path comprises a third switch, a loaded capacitor network and a fourth switch; each of the first switch, the second switch, the third switch and the fourth switch is composed of a plurality of radio frequency switch tubes; the direct current port is connected with the first switch, the second switch, the third switch and the fourth switch respectively; wherein the first switch and the second switch form a first single-pole double-throw switch, the third switch and the fourth switch form a second single-pole double-throw switch, and the loading type capacitor network is composed of a microstrip line and a grounding capacitor and used for filtering input signals. Compared with an interdigital band-pass filter structure, the band-pass filter has the advantages of compact structure, low cost, simple design and the like by introducing the loaded capacitor network.

Description

TECHNICAL FIELD

[0001] The utility model relates to filter technical field especially relates to a digital selectable band pass filter based on loading type capacitance structure. BACKGROUND

[0002] In communication system, filter is an indispensable device, its main function is selecting useful signal, removing unnecessary signal, reducing system response to unnecessary signal, and the performance of filter influences signal quality of communication system. Current filter assembly is developing towards integration and miniaturization, and the area of traditional interdigital band pass filter is big, structure is not compact, cost is high, therefore, design high performance, small size, light weight, high integration, high reliability filter has great significance to microwave communication system. SUMMARY

[0003] The utility model discloses a digital selectable band pass filter based on loading type capacitance structure, realizes high performance, small size, light weight, high integration and high reliability.

[0004] The utility model discloses a digital selectable band pass filter based on loading type capacitance structure, realizes high performance, small size, light weight, high integration and high reliability.

[0005] A digital selectable band pass filter based on loading type capacitance structure is provided, which comprises an input microstrip line, an output microstrip line and a direct current port arranged on a substrate and connected in sequence, a first frequency path and a second frequency path are connected between the input microstrip line and the output microstrip line, the first frequency path comprises a first switch, a loading type capacitance network and a second switch connected in sequence, the second frequency path comprises a third switch, a loading type capacitance network and a fourth switch, the first switch, the second switch, the third switch and the fourth switch are all composed of a plurality of radio frequency switch tubes, and the direct current port is connected with the first switch, the second switch, the third switch and the fourth switch.

[0006] Among them, the first switch and the second switch form a first single-pole double-throw switch, the third switch and the fourth switch form a second single-pole double-throw switch, the loading type capacitance network is composed of a microstrip line and a grounding capacitor, and is used for filtering an input signal.

[0007] In some embodiments, the first single-pole double-throw switch comprises a first switch tube, a second switch tube, a third switch tube and a fourth switch tube, the output end of the input microstrip line is connected with the first switch tube and the second switch tube respectively, the first switch tube is connected with the third switch tube, and the second switch tube is connected with the fourth switch tube; the second single-pole double-throw switch comprises a fifth switch tube, a sixth switch tube, a seventh switch tube and an eighth switch tube, the input end of the output microstrip line is connected with the fifth switch tube and the sixth switch tube respectively, the fifth switch tube is connected with the seventh switch tube, and the sixth switch tube is connected with the eighth switch tube.

[0008] The loading capacitor network is connected between the common connection points of the first switch tube and the third switch tube and the common connection points of the fifth switch tube and the seventh switch tube, and the common connection points of the second switch tube and the fourth switch tube and the common connection points of the sixth switch tube and the eighth switch tube respectively.

[0009] In some embodiments, the third switch tube, the fourth switch tube, the seventh switch tube and the eighth switch tube are all grounded.

[0010] Preferably, the third switch tube, the fourth switch tube, the seventh switch tube and the eighth switch tube are all grounded through a grounding hole.

[0011] In some embodiments, the loading capacitor network part comprises a first microstrip line, a first ground capacitor, a second microstrip line, a second ground capacitor, a third microstrip line, a third ground capacitor, a fourth microstrip line, a fourth ground capacitor, a fifth microstrip line, a fifth ground capacitor, a sixth microstrip line, a sixth ground capacitor, a seventh microstrip line, a seventh ground capacitor, an eighth microstrip line, an eighth ground capacitor, a ninth microstrip line, a ninth ground capacitor, a tenth microstrip line, a tenth ground capacitor, an eleventh microstrip line and an eleventh ground capacitor.

[0012] In some embodiments, the DC port comprises a first DC port, a second DC port, a third DC port and a fourth DC port; the gate of the third switch tube is connected with the first DC port through a first air bridge branch, a first gate resistor, a fourth air bridge branch, a fifth gate resistor connected with the gate of the seventh switch tube and a third air bridge branch in sequence; the gate of the first switch tube is connected with the second DC port through a second gate resistor, a sixth gate resistor connected with the gate of the fifth switch tube and a third air bridge branch in sequence; the gate of the second switch tube is connected with the third DC port through a third gate resistor, a seventh gate resistor connected with the gate of the sixth switch tube; and the gate of the fourth switch tube is connected with the fourth DC port through a fourth gate resistor, an eighth gate resistor connected with the gate of the eighth switch tube and a second air bridge branch in sequence.

[0013] Preferably, the first air bridge branch, the second air bridge branch, the third air bridge branch and the fourth air bridge branch are all composed of microstrip lines.

[0014] In some embodiments, the input microstrip line is a 50-ohm microstrip line, and the output microstrip line is a 50-ohm microstrip line.

[0015] In some embodiments, the substrate is a GaAs substrate with a thickness of 100 um.

[0016] In some embodiments, the parameters of the first microstrip line, the second microstrip line, the third microstrip line, the fourth microstrip line and the fifth microstrip line are all: width 70 um, length 414 um; and the parameters of the sixth microstrip line, the seventh microstrip line, the eighth microstrip line, the ninth microstrip line, the tenth microstrip line and the eleventh microstrip line are all: width 100 um, length 379 um.

[0017] It should be further noted that the technical features corresponding to the above options can be combined or replaced to form new technical solutions.

[0018] Compared with the prior art, the utility model has the beneficial effects that:

[0019] The utility model discloses a loading type capacitor network is introduced, and the microstrip line of open circuit branch can be replaced by the ground capacitor, and the microstrip line of different length is replaced by adjusting the size of ground capacitor, and compared with the interdigital band pass filter structure, the layout is smaller, and the filter is changed to have the action of selectable frequency by introducing the radio frequency switch element, and the switching of different frequency is achieved, and the filter has the advantages of compact structure, low cost, simple design and the like. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 A digital selectable band pass filter based on loading type capacitor structure is shown in the embodiment of the utility model, and the overall structural diagram is shown in the figure.

[0021] Figure 2 The layout of the digital selectable band pass filter is shown in the embodiment of the utility model.

[0022] Figure 3 The result of the first channel simulation is shown in the embodiment of the utility model.

[0023] Figure 4 The result of the second channel simulation is shown in the embodiment of the utility model. DETAILED DESCRIPTION

[0024] The technical solutions of the present application will be described clearly and completely below with reference to the drawings. Obviously, the described embodiments are some of the embodiments of the present application, but not all the embodiments. Based on the embodiments of the present application, all the other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present application.

[0025] In the description of the present application, it should be noted that the directions or positional relationships indicated by "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like are the directions or positional relationships described based on the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

[0026] In the description of the present application, it should be noted that, unless otherwise explicitly specified and limited, "mounting", "connection" and "connection" should be understood in a broad sense, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected, it can be mechanically connected, or it can be electrically connected, it can be directly connected, or indirectly connected through an intermediate medium, or it can be connected inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0027] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as there is no conflict.

[0028] Referring to Figure 1 , a digital selectable bandpass filter based on a loaded capacitor structure is provided, comprising an input microstrip line, an output microstrip line and a direct current port arranged on a substrate and connected in sequence, a first frequency path and a second frequency path are connected between the input microstrip line and the output microstrip line, respectively, the first frequency path comprises a first switch, a loaded capacitor network and a second switch connected in sequence; the second frequency path comprises a third switch, a loaded capacitor network and a fourth switch; the first switch, the second switch, the third switch and the fourth switch are all composed of a plurality of radio frequency switch tubes; the direct current port is connected with the first switch, the second switch, the third switch and the fourth switch, respectively;

[0029] Among them, the first switch and the second switch form a first single-pole double-throw switch, the third switch and the fourth switch form a second single-pole double-throw switch, and the loaded capacitor network is composed of a microstrip line and a grounded capacitor, and is used for filtering an input signal.

[0030] As Figure 2 shown, a design layout of the above-mentioned digital selectable bandpass filter is given, from the figure, it can be seen that eight switch tubes and four DC ports are arranged on the substrate; the input end of the input microstrip line 101 is connected with the first end of the first switch tube 31 and the first end of the second switch tube 32 respectively; the second end of the first switch tube 31 is connected with the second end of the third switch tube 41, the second end of the third switch tube 41 is connected in turn through the grounding resistor 72, the twelfth microstrip line 102 and the first microstrip line 103, the first end of the first microstrip line 103 is grounded, the second end of the first microstrip line 103 is also connected with the first end of the first grounding capacitor 51 and the first end of the capacitor 52, the first end of the second microstrip line 104 is grounded, the second end of the second microstrip line 104 is also connected with the second end of the second grounding capacitor 53 and the second end of the capacitor 52; the right side of the second microstrip line 104 is the third microstrip line 105, the first end of the third microstrip line 105 is grounded, the second end of the third microstrip line 105 is connected with the third grounding capacitor 54, the right side of the third microstrip line 105 is the fourth microstrip line 106.

[0031] The output microstrip line 109 is connected with the first end of the fifth switch tube 33 and the first end of the sixth switch tube 34 respectively; the second end of the fifth switch tube 33 is connected with the second end of the seventh switch tube 43, the second end of the seventh switch tube 43 is connected in turn through the grounding resistor 71, the thirteenth microstrip line 108 and the fifth microstrip line 107, the first end of the fifth microstrip line 107 is grounded, the second end of the fifth microstrip line 107 is also connected with the first end of the fifth grounding capacitor 57 and the first end of the capacitor 56, the first end of the fourth microstrip line 106 is grounded, the second end of the fourth microstrip line 106 is also connected with the second end of the fourth grounding capacitor 55 and the second end of the capacitor 56;

[0032] The second end of the second switch tube 32 is connected with the second end of the fourth switch tube 42, the second end of the fourth switch tube 42 is connected in turn through the fourteenth microstrip line 117 and the eleventh microstrip line 116, the first end of the eleventh microstrip line 116 is grounded, the second end of the eleventh microstrip line 116 is also connected with the first end of the eleventh grounding capacitor 58 and the first end of the capacitor 59, the first end of the tenth microstrip line 115 is grounded, the second end of the tenth microstrip line 115 is also connected with the first end of the tenth grounding capacitor 510 and the second end of the capacitor 59; the right side of the tenth microstrip line 115 is the ninth microstrip line 114, the first end of the ninth microstrip line 114 is grounded, the second end of the ninth microstrip line 114 is also connected with the first end of the ninth grounding capacitor 511 and the first end of the capacitor 512, the first end of the eighth microstrip line 113 is grounded, the second end of the eighth microstrip line 113 is also connected with the second end of the eighth grounding capacitor 514 and the second end of the capacitor 512, the right side of the eighth microstrip line 113 is the seventh microstrip line 112.

[0033] The second end of the sixth switch tube 34 is connected with the second end of the eighth switch tube 44, the second end of the eighth switch tube 44 is connected in turn through the fifteenth microstrip line 110 and the sixth microstrip line 111, the first end of the sixth microstrip line 111 is grounded, the second end of the sixth microstrip line 111 is also connected with the sixth ground capacitor 517 and the first end of the capacitor 516, the first end of the seventh microstrip line 112 is connected with a grounding hole, the second end of the seventh microstrip line 112 is also connected with the seventh ground capacitor 515 and the second end of the capacitor 516;

[0034] The first end of the third switch tube 41, the first end of the fourth switch tube 42, the first end of the seventh switch tube 43 and the first end of the eighth switch tube 44 are grounded through grounding holes.

[0035] Further, the direct current port comprises a first direct current port 121, a second direct current port 122, a third direct current port 123 and a fourth direct current port 124; the gate of the third switch tube 41 is connected in turn with the first direct current port 121 through the first air bridge branch 91, the first gate resistor 81, the fourth air bridge branch 94, the fifth gate resistor 85 connected with the gate of the seventh switch tube 43, the third air bridge branch 93; the gate of the first switch tube 31 is connected in turn with the second direct current port 122 through the second gate resistor 82, the sixth gate resistor 86 connected with the gate of the fifth switch tube 33, the third air bridge branch 93; the gate of the second switch tube 32 is connected in turn with the third direct current port 123 through the third gate resistor 83, the seventh gate resistor 87 connected with the gate of the sixth switch tube 34; the gate of the fourth switch tube 42 is connected in turn with the fourth direct current port 124 through the fourth gate resistor 84, the eighth gate resistor 88 connected with the gate of the eighth switch tube 44, the second air bridge branch 92.

[0036] Specifically, in the present example embodiment, the first microstrip line 103 and the first ground capacitor 51, the second microstrip line 104 and the second ground capacitor 53, the third microstrip line 105 and the third ground capacitor 54, the fourth microstrip line 106 and the fourth ground capacitor 55, the fifth microstrip line 107 and the fifth ground capacitor 57, the sixth microstrip line 111 and the sixth ground capacitor 517, the seventh microstrip line 112 and the seventh ground capacitor 515, the eighth microstrip line 113 and the eighth ground capacitor 514, the ninth microstrip line 114 and the ninth ground capacitor 511, the tenth microstrip line 115 and the tenth ground capacitor 510, the eleventh microstrip line 116 and the eleventh ground capacitor 58 form a loaded capacitor network, which has the advantage that the long microstrip line is replaced by the ground capacitor, thereby reducing the layout area.

[0037] Meanwhile, as shown in FIG. 1, the first switch tube 31, the second switch tube 32, the third switch tube 41, the fourth switch tube 42, the fifth switch tube 33, the sixth switch tube 34, the seventh switch tube 43 and the eighth switch tube 44 are connected in turn through the first microstrip line 103, the second microstrip line 104, the third microstrip line 105, the fourth microstrip line 106, the fifth microstrip line 107, the sixth microstrip line 111, the seventh microstrip line 112 and the eighth microstrip line 113. Figure 2As shown, the first switch comprises the first switch tube 31 and the third switch tube 41, and the second switch comprises the fifth switch tube 33 and the seventh switch tube 43, wherein the first switch tube 31 and the fifth switch tube 33 are in series, and the third switch tube 41 and the seventh switch tube 43 are in parallel; the third switch comprises the second switch tube 32 and the fourth switch tube 42, and the fourth switch comprises the sixth switch tube 34 and the eighth switch tube 44, wherein the second switch tube 32 and the sixth switch tube 34 are in series, and the fourth switch tube 42 and the eighth switch tube 44 are in parallel.

[0038] The first switch and the second switch form a first single-pole double-throw switch, and the third switch and the fourth switch form a second single-pole double-throw switch, and the filter selects different frequency paths through the first single-pole double-throw switch and the second single-pole double-throw switch.

[0039] In addition, in the example embodiment, the capacitor 52, the capacitor 56, the capacitor 59, the capacitor 512, and the capacitor 516 constitute inter-stage capacitors, which have the advantages that the capacitors formed between the microstrip lines are replaced by the series capacitors, the spacing between the microstrip lines is shortened, the layout area is reduced, and the volume is reduced.

[0040] In addition, in the example embodiment, the frequency of different passbands can be controlled by improving the size of the loading capacitors and the size of the inter-stage capacitors, which has a wide application market.

[0041] Further, the input end of the input microstrip line 101 is a 50-ohm microstrip line input end, and the output end of the output microstrip line 109 is a 50-ohm microstrip line output end.

[0042] Further, the first end of the first switch tube 31 and the second end of the first switch tube 31 are one of a source or a drain, respectively; the first end of the second switch tube 32 and the second end of the second switch tube 32 are one of a source or a drain, respectively; the first end of the fifth switch tube 33 and the second end of the fifth switch tube 33 are one of a source or a drain, respectively; the first end of the sixth switch tube 34 and the second end of the sixth switch tube 34 are one of a source or a drain, respectively; the first end of the third switch tube 41 and the second end of the third switch tube 41 are one of a source or a drain, respectively; the first end of the fourth switch tube 42 and the second end of the fourth switch tube 42 are one of a source or a drain, respectively; the first end of the seventh switch tube 43 and the second end of the seventh switch tube 43 are one of a source or a drain, respectively; and the first end of the eighth switch tube 44 and the second end of the eighth switch tube 44 are one of a source or a drain, respectively.

[0043] Further, the third switch tube 41, the fourth switch tube 42, the seventh switch tube 43, the eighth switch tube 44, the ground end of the first ground capacitor 51, the ground end of the capacitor 52, the ground end of the second ground capacitor 53, the ground end of the third ground capacitor 54, the ground end of the fourth ground capacitor 55, the ground end of the capacitor 56, the ground end of the fifth ground capacitor 57, the ground end of the eleventh capacitor 58, the ground end of the capacitor 59, the ground end of the tenth ground capacitor 510, the ground end of the ninth ground capacitor 511, the ground end of the capacitor 512, the ground end of the eighth ground capacitor 514, the ground end of the seventh ground capacitor 515, the ground end of the capacitor 516, the ground end of the sixth ground capacitor 517, the ground end of the resistor 71, the ground end of the resistor 72, the ground end of the first microstrip line 103, the ground end of the second microstrip line 104, the ground end of the third microstrip line 105, the ground end of the fourth microstrip line 106, the ground end of the fifth microstrip line 107, the ground end of the sixth microstrip line 111, the ground end of the sixth microstrip line 112, the ground end of the seventh microstrip line 113, the ground end of the eighth microstrip line 114, the ground end of the ninth microstrip line 115, the ground end of the tenth microstrip line 116 are grounded respectively through the ground holes opened on the substrate.

[0044] Specifically, as Figure 2As shown, the second end of the third switch tube 41 is connected to the first ground hole 61, the resistance 72 is connected to the second ground hole 62, the first end of the first microstrip line 103 is connected to the third ground hole 63, the first ground capacitor 51 is connected to the fifteenth ground hole 615, the first end of the second microstrip line 104 is connected to the fourth ground hole 64, the second ground capacitor 53 is connected to the fourteenth ground hole 614, the first end of the third microstrip line 105 is connected to the fifth ground hole 65, the third ground capacitor 54 is connected to the thirteenth ground hole 613, the first end of the fourth microstrip line 106 is connected to the sixth ground hole 66, the fourth ground capacitor 55 is connected to the twelfth ground hole 612, the first end of the fifth microstrip line 107 is connected to the seventh ground hole 67, the fifth ground capacitor 57 is connected to the eleventh ground hole 611, the resistance 71 is connected to the second ground hole 610, the second end of the seventh switch tube 43 is connected to the eighth ground hole 68, the second end of the eighth switch tube 44 is connected to the ninth ground hole 69, the second end of the fourth switch tube 42 is connected to the sixteenth ground hole 616, the first end of the eleventh microstrip line 116 is connected to the seventeenth ground hole 617, the eleventh ground capacitor 58 is connected to the twenty-eighth ground hole 628, the first end of the tenth microstrip line 115 is connected to the eighteenth ground hole 618, the tenth ground capacitor 510 is connected to the twenty-seventh ground hole 627, the first end of the ninth microstrip line 114 is connected to the nineteenth ground hole 619, the ninth ground capacitor 511 is connected to the twenty-sixth ground hole 626, the first end of the eighth microstrip line 113 is connected to the twentieth ground hole 620, the eighth ground capacitor 514 is connected to the twenty-fifth ground hole 625, the first end of the seventh microstrip line 112 is connected to the twenty-first ground hole 621, the seventh ground capacitor 515 is connected to the twenty-fourth ground hole 624, the first end of the sixth microstrip line 111 is connected to the twenty-second ground hole 622, and the sixth ground capacitor 517 is connected to the twenty-third ground hole 623.

[0045] Further, the substrate is a GaAs substrate with a thickness of 100 um.

[0046] Further, the parameters of the first microstrip line 103, the second microstrip line 104, the third microstrip line 105, the fourth microstrip line 106, and the fifth microstrip line 107 are as follows: width 70um, length 414um; the parameters of the sixth microstrip line 111, the seventh microstrip line 112, the eighth microstrip line 113, the ninth microstrip line 114, the tenth microstrip line 115, and the eleventh microstrip line 116 are as follows: width 100um, length 379um; the distance between the first microstrip line 103 and the second microstrip line 104 is 130um; the distance between the second microstrip line 104 and the third microstrip line 105 is 110um; the distance between the third microstrip line 105 and the fourth microstrip line 106 is 110um; the distance between the fourth microstrip line 106 and the fifth microstrip line 107 is 130um; the distance between the sixth microstrip line 111 and the seventh microstrip line 112 is 100um; the distance between the seventh microstrip line 112 and the eighth microstrip line 113 is 160um; the distance between the eighth microstrip line 113 and the ninth microstrip line 114 is 70um; the distance between the ninth microstrip line 114 and the tenth microstrip line 115 is 160um; and the distance between the tenth microstrip line 115 and the eleventh microstrip line 116 is 100um.

[0047] Further, the sizes of the first switch tube 31, the second switch tube 32, the fifth switch tube 33, and the sixth switch tube 34 are all 2*100um, and the sizes of the third switch tube 41, the fourth switch tube 42, the seventh switch tube 43, and the eighth switch tube 44 are all 2*50um.

[0048] Further, Figure 3 For Figure 2 The results of the simulation of the first channel of the middle layout include S21, S11, and S22 curve diagrams. At this time, the voltage of the first DC port 121 is-5V, the voltage of the second DC port 122 is 0V, the voltage of the third DC port 123 is-5V, the voltage of the fourth DC port 124 is 0V, and the filter follows the first frequency path (the first channel). In the diagram, the passband frequency is 12GHz-12.25GHz, the passband insertion loss S21 is-9.8dB, the out-of-band rejection at 10GHz and 14GHz is less than-40dB, and the input-output return loss is less than-12.5dB.

[0049] Figure 4 For Figure 2The results of the second channel simulation of the middle version of the layout, including S21, S11, S22 curve diagram, at this time, the first DC port 121 voltage is 0V, the second DC port 122 voltage is-5V, the third DC port 123 voltage is 0V, the fourth DC port 124 voltage is-5V, the filter walks the second frequency path (the second channel). The passband frequency in the figure is 16GHz~16.25GHz, the passband insertion loss S21 is-7.9dB, the out-of-band rejection at 14GHz and 18GHz is less than-35dB, and the input-output return loss is less than-17.5dB.

[0050] The above specific embodiments are detailed descriptions of the utility model, and cannot be determined as the specific embodiments of the utility model are limited to these descriptions. For ordinary skilled persons in the technical field to which the utility model belongs, without departing from the concept of the utility model, a number of simple deductions and substitutions can also be made, which should be regarded as belonging to the protection scope of the utility model.

Claims

1. A digitally selectable bandpass filter based on a loaded capacitance structure, characterized by, The application relates to a frequency path switching circuit, which comprises input microstrip lines, output microstrip lines and DC ports arranged on a substrate and connected in sequence, first frequency paths and second frequency paths connected between the input microstrip lines and the output microstrip lines respectively, the first frequency paths comprising first switches, loaded capacitor networks and second switches connected in sequence, the second frequency paths comprising third switches, loaded capacitor networks and fourth switches, the first switches, the second switches, the third switches and the fourth switches being composed of multiple radio frequency switch tubes, and the DC ports being connected with the first switches, the second switches, the third switches and the fourth switches respectively. The first switch and the second switch form a first single-pole double-throw switch, the third switch and the fourth switch form a second single-pole double-throw switch, and the loaded capacitor network is composed of a microstrip line and a grounding capacitor and used for filtering input signals.

2. The digitally selectable bandpass filter based on loaded capacitance structure according to claim 1, characterized in that, The first single-pole double-throw switch comprises first switch tubes, second switch tubes, third switch tubes and fourth switch tubes, the output ends of the input microstrip lines are connected with the first switch tubes and the second switch tubes respectively, the first switch tubes are connected with the third switch tubes, and the second switch tubes are connected with the fourth switch tubes; the second single-pole double-throw switch comprises fifth switch tubes, sixth switch tubes, seventh switch tubes and eighth switch tubes, the input ends of the output microstrip lines are connected with the fifth switch tubes and the sixth switch tubes respectively, the fifth switch tubes are connected with the seventh switch tubes, and the sixth switch tubes are connected with the eighth switch tubes. The loaded capacitor network is connected between the common connection points of the first switch tubes and the third switch tubes and the common connection points of the fifth switch tubes and the seventh switch tubes and between the common connection points of the second switch tubes and the fourth switch tubes and the common connection points of the sixth switch tubes and the eighth switch tubes.

3. The digitally selectable bandpass filter based on loaded capacitance structure according to claim 2, characterized in that, The third switch tubes, the fourth switch tubes, the seventh switch tubes and the eighth switch tubes are grounded.

4. The digitally selectable bandpass filter based on loaded capacitance structure according to claim 3, characterized in that, The third switch tubes, the fourth switch tubes, the seventh switch tubes and the eighth switch tubes are grounded through grounding holes.

5. The digitally selectable bandpass filter based on loaded capacitance structure according to claim 2, characterized in that, The loaded capacitor network part comprises first microstrip lines, first grounding capacitors, second microstrip lines, second grounding capacitors, third microstrip lines, third grounding capacitors, fourth microstrip lines, fourth grounding capacitors, fifth microstrip lines, fifth grounding capacitors, sixth microstrip lines, sixth grounding capacitors, seventh microstrip lines, seventh grounding capacitors, eighth microstrip lines, eighth grounding capacitors, ninth microstrip lines, ninth grounding capacitors, tenth microstrip lines, tenth grounding capacitors, eleventh microstrip lines and eleventh grounding capacitors.

6. The digitally selectable bandpass filter based on loaded capacitance structure according to claim 2, characterized in that, The direct current port comprises a first direct current port, a second direct current port, a third direct current port and a fourth direct current port; the gate of the third switch tube is connected with the first direct current port through a first air bridge branch, a first gate resistor, a fourth air bridge branch, a fifth gate resistor connected with the gate of the seventh switch tube, a third air bridge branch in sequence; the gate of the first switch tube is connected with the second direct current port through a second gate resistor, a sixth gate resistor connected with the gate of the fifth switch tube, a third air bridge branch in sequence; the gate of the second switch tube is connected with the third direct current port through a third gate resistor, a seventh gate resistor connected with the gate of the sixth switch tube in sequence; the gate of the fourth switch tube is connected with the fourth direct current port through a fourth gate resistor, an eighth gate resistor connected with the gate of the eighth switch tube, a second air bridge branch in sequence.

7. The digitally selectable bandpass filter based on loaded capacitance structure according to claim 5, characterized in that, The first air bridge branch, the second air bridge branch, the third air bridge branch and the fourth air bridge branch are all composed of microstrip lines.

8. The digitally selectable bandpass filter based on loaded capacitance structure according to claim 1, characterized in that, The input microstrip line is a 50-ohm microstrip line, and the output microstrip line is a 50-ohm microstrip line.

9. The digitally selectable bandpass filter based on loaded capacitance structure according to claim 1, characterized in that, The substrate is a GaAs substrate with a thickness of 100 um.

10. The digitally selectable bandpass filter based on loaded capacitance structure according to claim 4, characterized in that, The parameters of the first microstrip line, the second microstrip line, the third microstrip line, the fourth microstrip line and the fifth microstrip line are all as follows: width 70 um, length 414 um; the parameters of the sixth microstrip line, the seventh microstrip line, the eighth microstrip line, the ninth microstrip line, the tenth microstrip line and the eleventh microstrip line are all as follows: width 100 um, length 379 um.

Images