WO2001010021A1 - Analog filter - Google Patents
Analog filter Download PDFInfo
- Publication number
- WO2001010021A1 WO2001010021A1 PCT/EP2000/006537 EP0006537W WO0110021A1 WO 2001010021 A1 WO2001010021 A1 WO 2001010021A1 EP 0006537 W EP0006537 W EP 0006537W WO 0110021 A1 WO0110021 A1 WO 0110021A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- filter
- delta
- network
- node
- analog filter
- Prior art date
Links
Classifications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H7/00—Multiple-port networks comprising only passive electrical elements as network components
- H03H7/01—Frequency selective two-port networks
- H03H7/17—Structural details of sub-circuits of frequency selective networks
- H03H7/1741—Comprising typical LC combinations, irrespective of presence and location of additional resistors
- H03H7/1758—Series LC in shunt or branch path
-
- 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
- H03H11/08—Frequency selective two-port networks using gyrators
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H11/00—Networks using active elements
- H03H11/46—One-port networks
- H03H11/48—One-port networks simulating reactances
- H03H11/50—One-port networks simulating reactances using gyrators
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H7/00—Multiple-port networks comprising only passive electrical elements as network components
- H03H7/01—Frequency selective two-port networks
- H03H7/0115—Frequency selective two-port networks comprising only inductors and capacitors
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H7/00—Multiple-port networks comprising only passive electrical elements as network components
- H03H7/01—Frequency selective two-port networks
- H03H7/075—Ladder networks, e.g. electric wave filters
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H7/00—Multiple-port networks comprising only passive electrical elements as network components
- H03H7/01—Frequency selective two-port networks
- H03H7/17—Structural details of sub-circuits of frequency selective networks
- H03H7/1716—Comprising foot-point elements
- H03H7/1725—Element to ground being common to different shunt paths, i.e. Y-structure
Definitions
- the present invention relates to an analog filter.
- the invention relates to on-chip IF filters which require a high accuracy and thus a careful implementation.
- the analog filters considered by the invention may be passive analog filters using only passive components like coils and capacitors.
- the analog filters of the present invention may also be active analog filters where inductances are replaced by gyrators (gyrator-C or gm-C filters) .
- Fig. 1 shows a typical construction of a conventional filter circuit.
- the filter circuit comprises at least one filter stage FSTi and a plurality of filter stages FST1, ... FSTi ...FSTI can be cascaded.
- the filter circuit is fed by a source S and terminated with a termination impedance T.
- T termination impedance
- each filter stage FSTi adds one pole to the filter transfer function, then the filter transfer function is of the order I.
- the filter transfer function of an analog filter is represented by a polynomial of order I having a plurality of zeros and poles in the complex plane.
- the used components must have very exact values or automatic tuning circuits of the resonator (filter) components must be used, in order to minimize the influence of parasitics, especially those that cannot be compensated by existing desired components.
- automatic tuning can for example be preferably used in the case of gyrator-C or gm-C filters .
- the design of analog filters is well advanced and various techniques are available how a predetermined desired filter transfer function is realized in practice.
- the design starts from a basic, low-pass prototype filter circuit comprising at least one filter stage FSTI.
- a capacitor Cl is connected between ground GND and an input terminal INI of the filter stage FSTI.
- a capacitor C5 is connected between ground GND and an output terminal OUTI of the filter stage FSTI.
- a source S which e.g. consists of a current source I and a resistor Rl .
- a capacitive network formed by the capacitor C3 can be present and be connected to ground GND and an impedance network, for example an inductive network formed by star-connection of the inductances L2 , L3 , L4, is connected between the capacitor C3 and the input and output terminals INI, OUTI. Whilst the impedance network LI, L2 , L3 is always present, there are filter circuits where the capacitive network is missing, i.e. the capacitor C3 is just a wire to ground.
- a plurality of filter stages FSTI, FST2 , FST3 each having the basic construction as shown in Fig. 2a.
- the filter stages FSTI, FST2 , FST3 are cascaded, such that the respective inductances L41, L22; L42, L23 are serially connected.
- the circuit in Fig. 3a is reduced to the filter in Fig. 3b where the coils L41, L22; L42, L23 are merged into a single inductance L', L' ' which results in the filter circuit in Fig. 3b.
- a filter circuit of a predetermined order can be implemented.
- Fig. 2a Starting with the basic filter design for one filter stage FSTI as shown in Fig. 2a, it has recently been proposed to provide means for transforming the configuration into sets of grounded resonators which are free from solitary parasitics (adding new undesired poles or zeros) .
- a band-pass transformation is applied to the filter stage FSTI in Fig. 2a resulting in a typical conventional bandpass prototype transformation as shown in Fig. 2b.
- Fig. 2c shows a typical gyrator realisation of Fig. 2b where the coils are replaced by gyrators as shown in Fig. 4a (to be described later) .
- Fig. 2c is the bandpass transformed version of
- FIG. 4b showing the gyrator realisation of Fig. 2a.
- the inventor has investigated such a band-pass transformation for transforming structure into sets of ground resonators and has discovered that the filter transfer function of such a transformed structure is more stable since it is free from solitary parasitics as explained before.
- Active filter circuits in which a stable frequency characteristic can be obtained for the change of parasitic capacitance and a Q value can be adjusted by a mutual conductance amplifier in a one stage constitution is for example known from patent abstracts of Japan JP 08196642.
- the stable frequency characteristic is obtained by means of additional tuning circuitry.
- the object of the present invention is to provide an analog filter having one or more filter stages as explained above in which no solitary parasitics or additional purely resistive nodes are caused in the filter transfer function.
- an analog filter including at least one filter stage having an input terminal, an output terminal and an impedance network connected between said input and output terminals and ground, said impedance network having arranged three impedance elements in a Delta-configuration, such that a first node of the Delta-configuration is connected to the input terminal, a second node of the Delta- configuration is connected to the output terminal and the third node is connected to ground.
- a further network is inserted between said third node and ground.
- said impedance network comprises three inductors or three capacitors or a mixture of inductors/capacitors in a delta-configuration .
- said further network comprises a capacitor or an inductor or a parallel or serial capacitor-inductor network.
- the analog filter according to the invention has no additional purely resistive nodes, since the delta configuration of the three impedance elements ensures that all inductor terminals can be connected to capacitors. Therefore, no undesired poles/zeros are caused in the filter transfer function.
- Inductances of the impedance network can be realized by coils or pairs of gyrators.
- Fig. 1 shows basic construction of an analog filter IF having a plurality of filter stages FSTi;
- Fig. 2a shows a typical conventional low-pass prototype filter having a single filter stage FSTI
- Fig. 2b shows a typical conventional bandpass prototype transformation of Fig. 2a
- Fig. 2c shows a typical gyrator realisation of the circuit in Fig. 2b;
- Fig. 3a, 3b shows the construction of a multiple stage filter where each filter stage has the basic construction as shown in Fig. 2a;
- Fig. 4a, 4b shows the construction of a conventional analog filter using gyrators to replace the coils in Fig. 2a;
- Fig. 5 shows a basic construction of the filter circuit according to the invention;
- Fig. 6 shows an embodiment of the analog filter according to Fig. 5;
- Fig. 7a, 7b shows circuits including a delta-configuration for a multiple stage filter
- Fig. 8a, 8b shows an active filter where the inductances in Fig. 6 are replaced by gyrators.
- Fig. 5 shows a principle block diagram of the analog filter according to the invention where only one filter stage FSTi is used. However, the following explanations will be equally true if the invention is applied to each filter stage of a multiple-stage filter circuit.
- the analog filter has an input terminal INi, an output terminal OUTi, and an impedance network INET connected to ground GND and to the input INi and the output OUTi .
- a further network CNET shown in dashed lines
- the further network CNET can be a capacitive network and the impedance network INET can be a purely inductive network.
- a first capacitor Cl can be connected between the input terminal INi and ground GND and a second capacitor
- C5 can be connected between the output terminal OUTi and ground GND.
- the resistors Rl and R5 serve as the source and termination impedances. All components Cl, C5, Rl , R2 are optional elements as far as the inventive principle is concerned.
- the low-pass prototype filter circuit of Fig. 5 has an impedance network INET formed of an inductive network including a star-type connection of inductances L2 , L3 , L4 and there is a further network CNET formed by a capacitive network, i.e. a capacitor C3 , according to the invention - instead of using a band-pass transformation - a star-delta-transformation is used resulting in the structure of the impedance (inductive) network INET' shown in Fig. 6.
- the star-delta transformation according to the invention can be applied to any star-type impedance network INET, i.e. the impedances LI, L2 , L3 themselves may be constituted by impedance networks comprising parallel and/or serial connections of inductors and/or capacitors.
- the impedances of the delta-configuration La, Lb, Lc are general impedances, i.e. inductances and/or capacitances. That is, all impedances
- Ll, L2 , L3 of the original network INET can be impedance networks themselves and thus also the impedances La, Lb, Lc of the transformed impedance network INET' can generally be impedance networks.
- the star-delta transformation is usually used in power engineering for example to transform a star-type connection of stator coils into a delta-type configuration of stator coils in an electric motor as is well known for persons skilled in the art.
- the star-delta transformation leads to a configuration where the three inductor or in the general case impedance elements La, Lb, Lc are arranged in a delta-configuration such that a first node Nli of the delta-configuration is connected to the input terminal INi, a second node N2i of the delta-configuration is connected to the output terminal OUTi and the third node N3i is connected to the capacitive network CNET which can again be formed by a capacitor C3 as in Fig. 2a or directly to ground (if the capacitor C3 is missing) .
- the first node Nli is connected to the capacitor Cl
- the second node N2i is connected to the capacitor C5
- the third node N3i is connected to a capacitor C3 or a capacitive network CNET or directly to ground depending on the type of filter circuit.
- the impedances Ll, L2 , L3 are all inductances then of course also the transformed impedances will be inductances. If they are capacitances, then La, Lb, Lc will be capacitances, and if they are a mixture of coils and/or capacitors, then the impedances La, Lb, Lc will also be a mixture of coils and/or capacitors.
- the invention is not specifically restricted to any special kind of impedance network INET, INET' (as long as INET is a star-configuration and INET' is a delta- configuration) and also the further network is optional.
- the star-delta transformation according to the invention removes the parasitic nodes (for gyrator configurations) and the solitary parasitics (in case of inductances not realized by gyrators) and thus eliminates the instability problem of the filter transfer function.
- the star-delta transformation can also be applied to a multistage analog filter shown in Fig. 7a or 7b. Comparing Fig. 7 with Fig. 3, all star-type connections in Fig. 3a, 3b have been replaced by delta-configurations of coils. Therefore also in the multi-stage filter the advantages of the present invention are prevalent. If each inductor element for example in the filter circuit of
- Fig. 6 are replaced by active components like gyrators, also an active filter as shown in Fig. 8a, 8b can benefit from the star-delta transformation according to the invention.
- gyrator-C or gm-C active filters where solitary parasitic nodes are removed by the star-delta transformations on the prototype filters can be constructed.
- the present invention can be applied to any type of analog filter having star-type connections of coils and/or capacitors and is not limited to active filters where the impedance network is realized by inductors and where inductors are replaced by gyrators.
- Any type of filter circuit with a star-type impedance network INET with/without a further network CNET can benefit from the star-delta transformation according to the invention.
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Filters And Equalizers (AREA)
- Networks Using Active Elements (AREA)
Abstract
Description
Claims
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP00947963A EP1201030A1 (en) | 1999-08-03 | 2000-07-10 | Analog filter |
AU61575/00A AU6157500A (en) | 1999-08-03 | 2000-07-10 | Analog filter |
JP2001514538A JP2003506946A (en) | 1999-08-03 | 2000-07-10 | Analog filter |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE19936430A DE19936430A1 (en) | 1999-08-03 | 1999-08-03 | Analog filter |
DE19936430.3 | 1999-08-03 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2001010021A1 true WO2001010021A1 (en) | 2001-02-08 |
Family
ID=7916970
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/EP2000/006537 WO2001010021A1 (en) | 1999-08-03 | 2000-07-10 | Analog filter |
Country Status (6)
Country | Link |
---|---|
EP (1) | EP1201030A1 (en) |
JP (1) | JP2003506946A (en) |
CN (1) | CN1369135A (en) |
AU (1) | AU6157500A (en) |
DE (1) | DE19936430A1 (en) |
WO (1) | WO2001010021A1 (en) |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE102010029152A1 (en) | 2010-05-20 | 2011-11-24 | Continental Teves Ag & Co. Ohg | Active insulation filter |
CN102829853B (en) * | 2012-08-22 | 2015-12-09 | 中联重科股份有限公司 | Transmitter, multistage filter and weighing system |
CN106936136B (en) * | 2017-04-24 | 2018-03-27 | 韶关市佰瑞节能科技有限公司 | A kind of all-pass wave filtering harmonic elimination structure and control method for medium voltage network system |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5202655A (en) * | 1990-12-28 | 1993-04-13 | Sharp Kabushiki Kaisha | Microwave active filter circuit using pseudo gyrator |
EP0833445A2 (en) * | 1996-09-27 | 1998-04-01 | Lucent Technologies Inc. | Filter having tunable center frequency and/or tunable bandwidth |
WO1999038256A1 (en) * | 1998-01-21 | 1999-07-29 | Kmy Instruments Llc | Passive programmable wide-range filter |
-
1999
- 1999-08-03 DE DE19936430A patent/DE19936430A1/en not_active Ceased
-
2000
- 2000-07-10 JP JP2001514538A patent/JP2003506946A/en not_active Withdrawn
- 2000-07-10 CN CN00811283A patent/CN1369135A/en active Pending
- 2000-07-10 AU AU61575/00A patent/AU6157500A/en not_active Abandoned
- 2000-07-10 EP EP00947963A patent/EP1201030A1/en not_active Withdrawn
- 2000-07-10 WO PCT/EP2000/006537 patent/WO2001010021A1/en not_active Application Discontinuation
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5202655A (en) * | 1990-12-28 | 1993-04-13 | Sharp Kabushiki Kaisha | Microwave active filter circuit using pseudo gyrator |
EP0833445A2 (en) * | 1996-09-27 | 1998-04-01 | Lucent Technologies Inc. | Filter having tunable center frequency and/or tunable bandwidth |
WO1999038256A1 (en) * | 1998-01-21 | 1999-07-29 | Kmy Instruments Llc | Passive programmable wide-range filter |
Also Published As
Publication number | Publication date |
---|---|
JP2003506946A (en) | 2003-02-18 |
EP1201030A1 (en) | 2002-05-02 |
DE19936430A1 (en) | 2001-04-12 |
CN1369135A (en) | 2002-09-11 |
AU6157500A (en) | 2001-02-19 |
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