CN114094292A

CN114094292A - High-rejection LC band-pass filter

Info

Publication number: CN114094292A
Application number: CN202111558873.0A
Authority: CN
Inventors: 李凯
Original assignee: Suzhou Xilamico Electronic Technology Co ltd
Current assignee: Suzhou Xilamico Electronic Technology Co ltd
Priority date: 2021-06-25
Filing date: 2021-12-20
Publication date: 2022-02-25
Also published as: CN113363689A

Abstract

The invention discloses a high-rejection LC band-pass filter, which adopts a 4-order design, forms 4 transmission zeros outside a band and can meet the requirement of out-of-band high rejection; and the whole size is 1.6mm multiplied by 0.8mm multiplied by 0.7mm, thereby achieving the purpose of miniaturization.

Description

High-rejection LC band-pass filter

Technical Field

The invention relates to a filter, in particular to a high-rejection LC band-pass filter.

Background

A band-pass filter is able to pass frequency components in a certain frequency range and attenuate frequency components in other ranges to very low levels. The bandpass filter should have a relatively flat passband with no attenuation or amplification within the passband and have all frequencies attenuated outside the passband, and the out-of-passband conversion should be accomplished over a very small frequency range. The requirements for practical application of the band-pass filter require that the band-pass filter has the characteristic of out-of-band high rejection, and that the size of the band-pass filter is miniaturized and can be as small as possible.

Disclosure of Invention

The invention aims to provide a high-rejection LC band-pass filter, which adopts microwave low-loss dielectric ceramic, adopts a 4-order design, and forms 4 transmission zeros outside a band so as to achieve out-of-band high rejection.

Preferably, the overall dimensions are 1.6mm by 0.8mm by 0.7 mm.

Preferably, the microwave low-loss dielectric ceramic has a dielectric constant of 40.

Preferably, the microwave low-loss dielectric ceramic has a dielectric loss of less than 0.002.

Preferably, the microwave low-loss dielectric ceramic is internally provided with an inductor and a capacitor.

Preferably, the inductor includes: the first inductor mainly comprises a fourth microstrip line and a through hole connected with the fourth microstrip line; a second inductor mainly formed by a first microstrip line; a third inductor mainly composed of a fifth microstrip line and a through hole connected with the fifth microstrip line; a fourth inductor formed mainly by an eighth via hole; a fifth inductor formed mainly by a third microstrip line; a sixth inductor formed mainly by the tenth via hole; a seventh inductor mainly composed of a sixth microstrip line and a through hole connected with the sixth microstrip line; the eighth inductor mainly comprises a seventh microstrip line and a through hole connected with the seventh microstrip line; a ninth inductance formed mainly by the second microstrip line.

Preferably, the capacitor includes: the first capacitor mainly comprises a fourth polar plate and a second polar plate; a second capacitor mainly formed by an eighth polar plate, a second polar plate and a third polar plate; a third capacitor mainly formed by an eighth polar plate and a sixth polar plate; a fourth capacitor mainly composed of the second polar plate and the first polar plate; a fifth capacitor mainly formed by the third polar plate and the first polar plate; a sixth capacitor mainly composed of a fifth polar plate and a third polar plate; and the seventh capacitor is mainly formed by the eighth polar plate and the seventh polar plate.

Preferably, the first inductor and the third capacitor form a resonator; enabling the fourth inductor and the fourth capacitor to form a vibrator and enabling the sixth inductor and the fifth capacitor to form a vibrator; the eighth inductor and the seventh capacitor form a vibrator.

Preferably, the second inductor and the ninth inductor are introduced, so that the filter forms two zeros at the high end.

Preferably, a second capacitor is introduced such that the filter forms a zero at each of the low and high ends.

The invention has the advantages and beneficial effects that: the high-rejection LC band-pass filter adopts a 4-order design, forms 4 transmission zeros outside a band and can meet the requirement of out-of-band high rejection; and the whole size is 1.6mm multiplied by 0.8mm multiplied by 0.7mm, thereby achieving the purpose of miniaturization.

The invention adopts microwave low-loss dielectric ceramic, the dielectric material (dielectric constant is 40, and dielectric loss is less than 0.002) is added with solvent, dispersant and adhesive, and the raw ceramic material is formed by tape casting process. The metal layer and the microstrip line of the invention are printed on the surface of the green ceramic chip. The invention laminates the multilayer structure together, then cuts and sinters into porcelain, finally obtains the finished product.

Drawings

FIG. 1 is an equivalent circuit diagram of the filter of the present invention;

fig. 2 and 3 are schematic diagrams of the internal structure of the filter of the present invention.

Detailed Description

The following description of the embodiments of the present invention will be made with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.

The present invention provides a high-rejection LC band-pass filter, as shown in fig. 2 and 3, comprising: the ceramic body with the size of 1.6mm multiplied by 0.8mm multiplied by 0.7mm, the dielectric constant of 40 and the dielectric loss of less than 0.002, an input pad P1 arranged at the left end of the bottom surface of the ceramic body, an output pad P2 arranged at the right end of the bottom surface of the ceramic body and symmetrically arranged with the input pad P1, a grounding pad GND arranged at the middle part of the bottom surface of the ceramic body and six metal layers arranged inside the ceramic body;

six metal levels are including setting gradually from top to bottom:

a first metal layer comprising, sequentially from left to right: a first microstrip line 31, a second microstrip line 32, a third microstrip line 33, and a fourth microstrip line 34; the first microstrip line 31, the second microstrip line 32, the third microstrip line 33 and the fourth microstrip line 34 all extend in the front-rear direction; the first microstrip line 31 and the fourth microstrip line 34 are symmetrically arranged; the second microstrip line 32 and the third microstrip line 33 are symmetrically arranged;

a second metal layer comprising: an eighth plate 108 located above the second plate 102 and the third plate 103, and a fifth microstrip line 35 located above the rear side of the first plate 101; the fifth microstrip line 35 extends in the left-right direction; the left end of the eighth polar plate 108 also extends above the sixth polar plate 106; the right end of the eighth polar plate 108 also extends to the upper part of the seventh polar plate 107;

a third metal layer comprising: a sixth plate 106 positioned above the input pad P1, and a seventh plate 107 positioned above the output pad P2; the sixth plate 106 is electrically connected to the input pad P1 through the third via 203; the seventh plate 107 is electrically connected to the output pad P2 through the fourth via 204; the sixth polar plate 106 and the seventh polar plate 107 are symmetrically arranged;

a fourth metal layer comprising: a fourth plate 104 located above the second plate 102, a sixth microstrip line 36 extending from the front side of the fourth plate 104 to above the input pad P1, a fifth plate 105 located above the third plate 103, and a seventh microstrip line 37 extending from the front side of the fifth plate 105 to above the output pad P2; the fourth polar plate 104 and the fifth polar plate 105 are symmetrically arranged; the sixth microstrip line 36 and the seventh microstrip line 37 are symmetrically arranged;

a fifth metal layer comprising: a second plate 102 positioned above the left half of the first plate 101, and a third plate 103 positioned above the right half of the first plate 101; the second plate 102 and the third plate 103 are symmetrically arranged;

a sixth metal layer comprising: the first pole plate 101 is positioned above the ground pad GND, a left extension part extends from the left end of the rear side of the first pole plate 101 to the position above the input pad P1, and a right extension part extends from the right end of the rear side of the first pole plate 101 to the position above the output pad P2; the first plate 101 is electrically connected with the left half part of the ground pad GND through a first via 201; the first plate 101 is electrically connected with the right half of the ground pad GND through the second via 202;

the front end of the first microstrip line 31 is located above the sixth microstrip line 36 and the sixth polar plate 106, and the front end of the first microstrip line 31 is electrically connected with the sixth polar plate 106 and the sixth microstrip line 36 through a fifth via hole 205; the rear end of the first microstrip line 31 is located above the left extension part of the first pole plate 101, and the rear end of the first microstrip line 31 is electrically connected with the left extension part of the first pole plate 101 through a sixth via hole 206;

the front end of the second microstrip line 32 is located above the second plate 102, and the front end of the second microstrip line 32 is electrically connected to the second plate 102 through a seventh via 207; the rear end of the second microstrip line 32 is located above the left end of the fifth microstrip line 35, and the rear end of the second microstrip line 32 is electrically connected with the left end of the fifth microstrip line 35 and the first pole plate 101 through the eighth via hole 208;

the front end of the third microstrip line 33 is located above the third plate 103, and the front end of the third microstrip line 33 is electrically connected with the third plate 103 through a ninth via 209; the rear end of the third microstrip line 33 is located above the right end of the fifth microstrip line 35, and the rear end of the third microstrip line 33 is electrically connected with the right end of the fifth microstrip line 35 and the first pole plate 101 through a tenth via 210; the eighth via hole 208 and the tenth via hole 210 are symmetrically arranged;

the front end of the fourth microstrip line 34 is located above the seventh microstrip line 37 and the seventh polar plate 107, and the front end of the fourth microstrip line 34 is electrically connected with the seventh polar plate 107 and the seventh microstrip line 37 through an eleventh via hole 211; the rear end of the fourth microstrip line 34 is located above the right extending portion of the first plate 101, and the rear end of the fourth microstrip line 34 is electrically connected to the right extending portion of the first plate 101 through a twelfth via hole 212.

The equivalent circuit diagram of the high-rejection LC band-pass filter is shown in FIG. 1, and the circuit diagram comprises seven capacitors and nine inductors.

Specifically, the seven capacitors are respectively:

1) a first capacitor C1 mainly composed of a fourth plate 104 and a second plate 102;

2) a second capacitor C2 formed mainly by the eighth plate 108, the second plate 102, and the third plate 103;

3) a third capacitor C3 formed mainly by the eighth plate 108 and the sixth plate 106;

4) a fourth capacitor C4 mainly composed of the second plate 102 and the first plate 101;

5) a fifth capacitor C5 formed by the third plate 103 and the first plate 101;

6) a sixth capacitor C6 mainly composed of the fifth plate 105 and the third plate 103;

7) and a seventh capacitor C7 formed by the eighth plate 108 and the seventh plate 107.

The nine inductors are respectively:

1) a first inductor L1 mainly composed of the first microstrip line 31 and a through hole connected thereto;

2) a second inductance L2 mainly formed by the sixth microstrip line 36;

3) a third inductor L3 mainly composed of the second microstrip line 32 and a through hole connected thereto;

4) a fourth inductance L4 formed mainly by an eighth via hole;

5) a fifth inductance L5 mainly formed by the fifth microstrip line 35;

6) a sixth inductance L6 formed mainly by the tenth via hole;

7) a seventh inductor L7 mainly composed of the third microstrip line 33 and a through hole connected thereto;

8) an eighth inductor L8 mainly composed of the fourth microstrip line 34 and a through hole connected thereto;

9) a ninth inductance L9 formed mainly by the seventh microstrip line 37.

Wherein:

the first inductor L1, the third capacitor C3, the fourth inductor L4, the fourth capacitor C4, the sixth inductor L6, the fifth capacitor C5, the eighth inductor L8 and the seventh capacitor C7 form four vibrators;

the second inductor L2 and the ninth inductor L9 are introduced, so that the filter of the invention forms two zeros at the high end;

a second capacitor C2 is introduced to form a zero at each of the low and high ends of the filter of the present invention.

Through tests, the passband insertion loss of the filter is lower than 1.5dB, and the out-of-band rejection reaches more than 40dB at both 4G and 9G.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the technical principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims

1. The high-rejection LC band-pass filter is characterized in that microwave low-loss dielectric ceramic is adopted, the filter adopts a 4-order design, 4 transmission zeros are formed outside a band, and out-of-band high rejection is achieved.

2. The high rejection LC band pass filter according to claim 1, wherein the overall dimensions are 1.6mm x 0.8mm x 0.7 mm.

3. The high rejection LC band pass filter according to claim 1, wherein the dielectric constant of the microwave low loss dielectric ceramic is 40.

4. The high rejection LC band pass filter according to claim 1, wherein the microwave low loss dielectric ceramic has a dielectric loss of less than 0.002.

5. The high rejection LC band pass filter according to claim 1, wherein said microwave low loss dielectric ceramic has an inductor and a capacitor disposed therein.

6. The high rejection LC band pass filter according to claim 5, wherein said inductor comprises:

the first inductor mainly comprises a fourth microstrip line and a through hole connected with the fourth microstrip line;

a second inductor mainly formed by a first microstrip line;

a third inductor mainly composed of a fifth microstrip line and a through hole connected with the fifth microstrip line;

a fourth inductor formed mainly by an eighth via hole;

a fifth inductor formed mainly by a third microstrip line;

a sixth inductor formed mainly by the tenth via hole;

a seventh inductor mainly composed of a sixth microstrip line and a through hole connected with the sixth microstrip line;

the eighth inductor mainly comprises a seventh microstrip line and a through hole connected with the seventh microstrip line;

a ninth inductance formed mainly by the second microstrip line.

7. The high rejection LC band pass filter according to claim 6, wherein said capacitor comprises:

the first capacitor mainly comprises a fourth polar plate and a second polar plate;

a second capacitor mainly formed by an eighth polar plate, a second polar plate and a third polar plate;

a third capacitor mainly formed by an eighth polar plate and a sixth polar plate;

a fourth capacitor mainly composed of the second polar plate and the first polar plate;

a fifth capacitor mainly formed by the third polar plate and the first polar plate;

a sixth capacitor mainly composed of a fifth polar plate and a third polar plate;

and the seventh capacitor is mainly formed by the eighth polar plate and the seventh polar plate.

8. The high rejection LC band pass filter of claim 7, wherein the first inductor and the third capacitor are formed into a dipole;

the fourth inductor and the fourth capacitor form a vibrator

Enabling the sixth inductor and the fifth capacitor to form a vibrator;

the eighth inductor and the seventh capacitor form a vibrator.

9. The high rejection LC band pass filter of claim 8, wherein said second inductor and said ninth inductor are introduced such that said filter forms two zeros at a high side.

10. The high rejection LC band pass filter according to claim 9, wherein a second capacitor is introduced such that the filter forms a zero at each of the low and high sides.