CN114124029B - Second-order adjustable LC notch filter for polar zero tracking - Google Patents
Second-order adjustable LC notch filter for polar zero tracking Download PDFInfo
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- CN114124029B CN114124029B CN202111443405.9A CN202111443405A CN114124029B CN 114124029 B CN114124029 B CN 114124029B CN 202111443405 A CN202111443405 A CN 202111443405A CN 114124029 B CN114124029 B CN 114124029B
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- 239000003990 capacitor Substances 0.000 claims abstract description 92
- 230000005764 inhibitory process Effects 0.000 abstract description 3
- 238000000034 method Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- 230000001360 synchronised effect Effects 0.000 description 1
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H11/00—Networks using active elements
- H03H11/02—Multiple-port networks
- H03H11/04—Frequency selective two-port networks
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H11/00—Networks using active elements
- H03H11/02—Multiple-port networks
- H03H11/04—Frequency selective two-port networks
- H03H2011/0488—Notch or bandstop filters
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Abstract
The invention discloses a second-order adjustable LC notch filter for pole zero tracking, which is characterized in that an Input end (Input), a first serial inductor (L1) of the filter, a second serial inductor (L2) of the filter and an Output end (Output) are sequentially connected in series, and two ends of a parallel switch capacitor (C1) are respectively connected with the Input end (Input) and the Output end (Output); the connection point of the first serial inductor (L1) of the filter and the second serial inductor (L2) of the filter is a node (A), one end of the third parallel inductor (L3) of the filter is connected with the node (A), and the other end is grounded. The invention realizes the tracking inhibition of the image signal of the broadband transceiver by utilizing the parallel switch capacitor based on the second-order LC filter network and effectively improves the inhibition ratio of the image signal in the broadband range.
Description
Technical Field
The invention relates to the technical field of electronic circuits, in particular to a polar zero tracking second-order LC notch filter circuit, and belongs to the technical field of notch filter design.
Background
In transceiver systems, image interference refers to interference signals generated during up and down mixing of signals. The generation of the image signal has a significant impact not only on the own transceiver system but also on other useful channels that are transmitted into space by the transmitter. The image rejection ratio is an indispensable indicator in transceiver systems due to the hazards of the image signal. There are two common methods for achieving image rejection: the first transceiver system adopts an I/Q path structure; the second is to add a notch filter. The method adopting the I/Q path structure needs an I path and a Q path, thereby greatly increasing the area and the power consumption of the system. For the above reasons, the method of using notch filter is more attractive for improving the performance of the transceiver system.
The main challenge currently faced in notch filter design is how to effectively reject image frequency signals in the broadband feedback range. In addition, for the polar zero tracking second order LC notch filter circuit, the bandwidth and gain of the useful signal should be kept unchanged while the broadband image signal is effectively suppressed.
Disclosure of Invention
Technical problems: the technical problems to be solved by the invention are as follows: providing a second-order adjustable LC notch filter for pole zero tracking, and realizing the function of pole zero tracking by a parallel switch capacitor based on a second-order LC filter network, thereby realizing tracking inhibition of the image signal of a transceiver; in the broadband range, the image signal rejection ratio of the transceiver is effectively improved.
The technical scheme is as follows: in order to solve the technical problems, the invention provides a second-order adjustable LC notch filter for polar zero tracking, which comprises the following components: the filter comprises an input end, a first filter series inductor, a second filter series inductor, a third filter parallel inductor, a parallel switch capacitor, an output end and a node; the input end, the first serial inductor of the filter, the second serial inductor of the filter and the output end are sequentially connected in series, and two ends of the parallel switch capacitor are respectively connected with the input end and the output end; the connection point of the first series inductor of the filter and the second series inductor of the filter is a node, one end of the third parallel inductor of the filter is connected with the node, and the other end is grounded.
The parallel switch capacitor is an adjustable parallel switch capacitor, and frequency tuning is achieved.
The parallel switch capacitor consists of a plurality of branches which are mutually connected in parallel, and the first branch is a second capacitor; the second branch is formed by sequentially connecting a third capacitor, a fourth switching transistor and a fourth capacitor in series; the third branch is formed by sequentially connecting a fifth capacitor, a third switching transistor and a sixth capacitor in series; the fourth branch is formed by sequentially connecting a seventh capacitor, a second switching transistor and an eighth capacitor in series; the fifth branch is formed by sequentially connecting a ninth capacitor, a first switching transistor and a tenth capacitor in series; the two ends of the branches connected in parallel are two ends of the parallel switch capacitor, one end of the branch is a second node, and the other end of the branch is a third node.
The first switch transistor, the second switch transistor, the third switch transistor and the fourth switch transistor are all N-type transistors.
The third capacitor, the fourth capacitor, the fifth capacitor, the sixth capacitor, the seventh capacitor, the eighth capacitor, the ninth capacitor and the tenth capacitor have the same capacitance value.
The capacitance value of the second capacitor (C2) is determined according to zero frequency omega z0 and a first series inductor (L1) of the filter, a second series inductor (L2) of the filter and a third series inductor (L3) of the filter in the state that the first switch transistor, the second switch transistor, the third switch transistor and the fourth switch transistor of the notch filter are all turned off. The values are calculated specifically as follows:
The grid electrode of the first transistor is connected with the zeroth digital control signal, the grid electrode of the second transistor is connected with the first digital control signal, the grid electrode of the third transistor is connected with the second digital control signal, and the grid electrode of the fourth transistor is connected with the third digital control signal.
The change of the zeroth digital control signal, the first digital control signal, the second digital control signal and the third digital control signal can change the capacitance value of the parallel switch capacitor, so that the polar zero frequency moves in an equal proportion, and the image signal rejection ratio is improved in a broadband range.
The first series inductor of the filter, the second series inductor of the filter and the third parallel inductor of the filter are plane inductors or cylindrical inductors.
The beneficial effects are that: the circuit structure of the second-order LC notch filter based on polar zero tracking generates zero at the frequency of an image signal and simultaneously generates a pole at the frequency of a useful signal; filtering the image signal and simultaneously retaining the useful signal; and the synchronous tracking of zero poles is realized through the switch parallel capacitor, and the suppression of the broadband mirror image signal is realized.
Drawings
Fig. 1 is a schematic diagram of a second-order tunable LC notch filter based on polar zero tracking according to the present invention.
Fig. 2 is a schematic diagram of a second-order adjustable LC notch filter circuit switch-adjustable parallel capacitance based on a pole zero tracking in the present invention.
Detailed Description
The invention is further explained below with reference to the drawings.
As shown in fig. 1, a second-order tunable LC notch filter for polar zero tracking of the present invention includes: the Input end Input, the first serial inductor L1 of the filter, the second serial inductor L2 of the filter, the third parallel inductor L3 of the filter, the parallel switch capacitor C1, the Output end Output and the node A; the Input end Input, the first serial inductor L1 of the filter, the second serial inductor L2 of the filter and the Output end Output are sequentially connected in series, and two ends of the parallel switch capacitor C1 are respectively connected with the Input end Input and the Output end Output; the connection point of the first serial inductor L1 of the filter and the second serial inductor L2 of the filter is a node A, one end of the third parallel inductor L3 of the filter is connected with the node A, and the other end is grounded. The first series inductor L1, the second series inductor L2 and the third parallel inductor L3 are plane inductors or cylindrical inductors.
As shown in fig. 2, the switch parallel capacitor C1 is an adjustable parallel switch capacitor, so as to realize frequency tuning.
The parallel switch capacitor C1 consists of a plurality of branches which are mutually connected in parallel, and the first branch is a second capacitor C2; the second branch is formed by sequentially connecting a third capacitor C3, a fourth switching transistor M4 and a fourth capacitor C4 in series; the third branch is formed by sequentially connecting a fifth capacitor C5, a third switching transistor M3 and a sixth capacitor C6 in series; the fourth branch is formed by sequentially connecting a seventh capacitor C7, a second switching transistor M2 and an eighth capacitor C8 in series; the fifth branch is formed by sequentially connecting a ninth capacitor C9, a first switching transistor M1 and a tenth capacitor C10 in series; the two ends of the several branches connected in parallel are two ends of the parallel switch capacitor C1, one end of the parallel switch capacitor is the second node N, and the other end of the parallel switch capacitor is the third node P. The third capacitor C3, the fourth capacitor C4, the fifth capacitor C5, the sixth capacitor C6, the seventh capacitor C7, the eighth capacitor C8, the ninth capacitor C9 and the tenth capacitor C10 have the same capacitance value.
As shown in fig. 2, in the switch parallel capacitor C1 of the present invention, the first switch transistor M1, the second switch transistor M2, the third switch transistor M3, and the fourth switch transistor M4 are all N-type transistors.
The concrete connection is as follows: the ninth capacitor C9 is respectively connected with the second node N and the drain end of the first transistor M1, the tenth capacitor C10 is respectively connected with the third node P and the source end of the first transistor M1, the seventh capacitor C7 is respectively connected with the second node N and the drain end of the second transistor M2, the eighth capacitor C8 is respectively connected with the third node P and the source end of the second transistor M2, the fifth capacitor C5 is respectively connected with the second node N and the drain end of the third transistor M3, the sixth capacitor C6 is respectively connected with the third node P and the source end of the third transistor M3, the third capacitor C3 is respectively connected with the second node N and the drain end of the fourth transistor M4, the fourth capacitor C4 is respectively connected with the third node P and the source end of the fourth transistor M4, the second capacitor C2 is connected between the second node N and the third node P in a bridging manner, the grid electrode of the first transistor M1 is connected with the zero digital control signal B0, the grid electrode of the second transistor M2 is connected with the first digital control signal B1, the grid electrode of the third transistor M3 is connected with the digital control signal B2, and the fourth transistor M4 is connected with the digital control signal B3.
The pole zero tracking second-order LC notch filter circuit poles can be obtained by calculating the filter output current and the input current:
The zero point is:
And then the pole-zero frequency ratio is obtained as follows:
as shown in the above equation, the filter pole zero ratio is independent of the switch shunt capacitance C1. The capacitance value of the parallel switch capacitor C1 can be changed by controlling the digital signals B0-B3, so that the polar zero frequency is moved in an equal proportion, and the image signal rejection ratio is improved in a broadband range.
Claims (8)
1. A pole zero tracking second order tunable LC notch filter comprising: an Input end (Input), a first series inductor (L1) of the filter, a second series inductor (L2) of the filter, a third parallel inductor (L3) of the filter, a parallel switch capacitor (C1), an Output end (Output) and a node (A); the Input end (Input), the first filter series inductor (L1), the second filter series inductor (L2) and the Output end (Output) are sequentially connected in series, and two ends of the parallel switch capacitor (C1) are respectively connected with the Input end (Input) and the Output end (Output); the connection point of the first serial inductor (L1) of the filter and the second serial inductor (L2) of the filter is a node (A), one end of the third parallel inductor (L3) of the filter is connected with the node (A), and the other end is grounded;
The parallel switch capacitor (C1) consists of a plurality of branches which are mutually connected in parallel, and the first branch is a second capacitor (C2); the second branch is formed by sequentially connecting a third capacitor (C3), a fourth switching transistor (M4) and a fourth capacitor (C4) in series; the third branch is formed by sequentially connecting a fifth capacitor (C5), a third switching transistor (M3) and a sixth capacitor (C6) in series; the fourth branch is formed by sequentially connecting a seventh capacitor (C7), a second switching transistor (M2) and an eighth capacitor (C8) in series; the fifth branch is formed by sequentially connecting a ninth capacitor (C9), a first switching transistor (M1) and a tenth capacitor (C10) in series; two ends of the branches which are mutually connected in parallel are two ends of a parallel switch capacitor (C1), one end of the parallel switch capacitor is a second node (N), and the other end of the parallel switch capacitor is a third node (P);
The capacitance value of the second capacitor (C2) is determined according to zero frequency omega z0 and a first series inductor (L1) of the filter, a second series inductor (L2) of the filter and a third series inductor (L3) of the filter in the state that the first switch transistor, the second switch transistor, the third switch transistor and the fourth switch transistor of the notch filter are all turned off.
2. The pole zero tracking second order tunable LC notch filter of claim 1, wherein the shunt switch capacitor (C1) is a tunable shunt switch capacitor, to achieve frequency tuning.
3. The pole-zero tracking second order tunable LC notch filter of claim 1, wherein the first switching transistor (M1), the second switching transistor (M2), the third switching transistor (M3), and the fourth switching transistor (M4) are all N-type transistors.
4. The pole-zero tracking second order tunable LC notch filter of claim 1, wherein the third capacitor (C3), the fourth capacitor (C4), the fifth capacitor (C5), the sixth capacitor (C6), the seventh capacitor (C7), the eighth capacitor (C8), the ninth capacitor (C9), and the tenth capacitor (C10) have the same capacitance value.
5. The polar zero tracking second order tunable LC notch filter of claim 1, wherein the second capacitance (C2) capacitance value:
6. The pole-zero tracking second order tunable LC notch filter of claim 1, wherein the gate of the first transistor (M1) is connected to the zeroth digital control signal (B0), the gate of the second transistor (M2) is connected to the first digital control signal (B1), the gate of the third transistor (M3) is connected to the second digital control signal (B2), and the gate of the fourth transistor (M4) is connected to the third digital control signal (B3).
7. The pole-zero tracking second order tunable LC notch filter of claim 6, wherein the change of the zeroth digital control signal (B0), the first digital control signal (B1), the second digital control signal (B2), and the third digital control signal (B3) changes the capacitance value of the shunt switch capacitor (C1) such that the pole-zero frequency is equally scaled, thereby increasing the image signal rejection ratio in a wide band range.
8. The pole-zero tracking second order tunable LC notch filter of claim 1, wherein the filter first series inductor (L1), the filter second series inductor (L2), and the filter third parallel inductor (L3) are planar inductors or cylindrical inductors.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111443405.9A CN114124029B (en) | 2021-11-30 | 2021-11-30 | Second-order adjustable LC notch filter for polar zero tracking |
| PCT/CN2022/136957 WO2023098918A1 (en) | 2021-11-30 | 2022-12-06 | Second-order adjustable lc notch filter for pole zero tracking |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111443405.9A CN114124029B (en) | 2021-11-30 | 2021-11-30 | Second-order adjustable LC notch filter for polar zero tracking |
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| Publication Number | Publication Date |
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| CN114124029A CN114124029A (en) | 2022-03-01 |
| CN114124029B true CN114124029B (en) | 2024-06-28 |
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| CN202111443405.9A Active CN114124029B (en) | 2021-11-30 | 2021-11-30 | Second-order adjustable LC notch filter for polar zero tracking |
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| WO (1) | WO2023098918A1 (en) |
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| CN114124029B (en) * | 2021-11-30 | 2024-06-28 | 东南大学 | Second-order adjustable LC notch filter for polar zero tracking |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102497519A (en) * | 2011-11-30 | 2012-06-13 | 重庆大学 | Ultrahigh frequency high image rejection filter |
| CN104067514A (en) * | 2012-01-23 | 2014-09-24 | 高通股份有限公司 | Impedance matching circuit with tunable notch filters for power amplifier |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6990327B2 (en) * | 2003-04-30 | 2006-01-24 | Agency For Science Technology And Research | Wideband monolithic tunable high-Q notch filter for image rejection in RF application |
| US20050040909A1 (en) * | 2003-08-20 | 2005-02-24 | Waight Matthew Glenn | Broadband integrated digitally tunable filters |
| KR100692306B1 (en) * | 2005-04-01 | 2007-03-09 | 인티그런트 테크놀로지즈(주) | Tracking filter for tuning channel in wide-band |
| US9143172B2 (en) * | 2009-06-03 | 2015-09-22 | Qualcomm Incorporated | Tunable matching circuits for power amplifiers |
| CN202034953U (en) * | 2010-11-26 | 2011-11-09 | 惠州Tcl王牌高频电子有限公司 | Electronic tuner having image rejection function |
| CN104038158A (en) * | 2014-06-05 | 2014-09-10 | 西安电子科技大学 | Low-noise amplifier structure |
| CN111490801A (en) * | 2019-01-29 | 2020-08-04 | 上海川土微电子有限公司 | Radio frequency receiver architecture with adjustable image rejection ratio |
| CN114124029B (en) * | 2021-11-30 | 2024-06-28 | 东南大学 | Second-order adjustable LC notch filter for polar zero tracking |
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2021
- 2021-11-30 CN CN202111443405.9A patent/CN114124029B/en active Active
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- 2022-12-06 WO PCT/CN2022/136957 patent/WO2023098918A1/en unknown
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102497519A (en) * | 2011-11-30 | 2012-06-13 | 重庆大学 | Ultrahigh frequency high image rejection filter |
| CN104067514A (en) * | 2012-01-23 | 2014-09-24 | 高通股份有限公司 | Impedance matching circuit with tunable notch filters for power amplifier |
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| Publication number | Publication date |
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| WO2023098918A1 (en) | 2023-06-08 |
| CN114124029A (en) | 2022-03-01 |
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Address after: 211189 No. 2 Southeast University Road, Jiangning District, Nanjing, Jiangsu Patentee after: SOUTHEAST University Country or region after: China Patentee after: Zijinshan Laboratory Address before: 211189 No. 2 Southeast University Road, Jiangning District, Nanjing, Jiangsu Patentee before: SOUTHEAST University Country or region before: China Patentee before: Purple Mountain Laboratories |