WO2023079469A1 - Compact lc filter for radio frequency power transmitters - Google Patents
Compact lc filter for radio frequency power transmitters Download PDFInfo
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- WO2023079469A1 WO2023079469A1 PCT/IB2022/060580 IB2022060580W WO2023079469A1 WO 2023079469 A1 WO2023079469 A1 WO 2023079469A1 IB 2022060580 W IB2022060580 W IB 2022060580W WO 2023079469 A1 WO2023079469 A1 WO 2023079469A1
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- WIPO (PCT)
- Prior art keywords
- printed circuit
- circuit board
- filter
- radio frequency
- input terminal
- Prior art date
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- 239000003990 capacitor Substances 0.000 claims abstract description 20
- 238000012546 transfer Methods 0.000 claims abstract description 5
- 229910052751 metal Inorganic materials 0.000 claims abstract description 4
- 239000002184 metal Substances 0.000 claims abstract description 4
- 238000001259 photo etching Methods 0.000 claims abstract description 4
- 239000000463 material Substances 0.000 claims description 8
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 3
- 239000002131 composite material Substances 0.000 claims description 2
- 239000004020 conductor Substances 0.000 claims description 2
- 239000003365 glass fiber Substances 0.000 claims description 2
- 229910010293 ceramic material Inorganic materials 0.000 claims 1
- 239000006112 glass ceramic composition Substances 0.000 claims 1
- 239000004810 polytetrafluoroethylene Substances 0.000 claims 1
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims 1
- 238000004519 manufacturing process Methods 0.000 description 5
- 230000005540 biological transmission Effects 0.000 description 4
- 238000010276 construction Methods 0.000 description 3
- 239000000919 ceramic Substances 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 230000003071 parasitic effect Effects 0.000 description 2
- 230000008646 thermal stress Effects 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 239000004411 aluminium Substances 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 230000003321 amplification Effects 0.000 description 1
- 230000003749 cleanliness Effects 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000000295 emission spectrum Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000020169 heat generation Effects 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
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- 238000003199 nucleic acid amplification method Methods 0.000 description 1
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- 230000001681 protective effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
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
- H03H7/0115—Frequency selective two-port networks comprising only inductors and capacitors
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F17/00—Fixed inductances of the signal type
- H01F17/02—Fixed inductances of the signal type without magnetic core
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F27/00—Details of transformers or inductances, in general
- H01F27/28—Coils; Windings; Conductive connections
- H01F27/2847—Sheets; Strips
-
- 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
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K1/00—Printed circuits
- H05K1/16—Printed circuits incorporating printed electric components, e.g. printed resistor, capacitor, inductor
- H05K1/162—Printed circuits incorporating printed electric components, e.g. printed resistor, capacitor, inductor incorporating printed capacitors
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H1/00—Constructional details of impedance networks whose electrical mode of operation is not specified or applicable to more than one type of network
- H03H2001/0021—Constructional details
- H03H2001/005—Wound, ring or feed-through type inductor
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H1/00—Constructional details of impedance networks whose electrical mode of operation is not specified or applicable to more than one type of network
- H03H2001/0021—Constructional details
- H03H2001/0085—Multilayer, e.g. LTCC, HTCC, green sheets
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K1/00—Printed circuits
- H05K1/18—Printed circuits structurally associated with non-printed electric components
- H05K1/181—Printed circuits structurally associated with non-printed electric components associated with surface mounted components
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
- H05K2201/10—Details of components or other objects attached to or integrated in a printed circuit board
- H05K2201/10007—Types of components
- H05K2201/1003—Non-printed inductor
Definitions
- the present invention relates to the technical field of systems for radio frequency broadcasting ("Broadcasting") of signals, for example of radio or television signals.
- Broadcasting radio frequency broadcasting
- the invention relates to a compact radio frequency LC filter with high power and very low return, particularly suitable for use in power equipment for the transmission of aforesaid radio or television signals.
- radio frequency transmitters are commonly used, capable of working with antenna emission power ranging from hundreds of Watts to tens of Kilowatts.
- Such transmitters generally comprise feed sections, signal amplification sections and one or more LC filters, aimed at limiting the antenna emission spectrum to the required frequency band and to keep out-of-band frequencies within acceptable limits.
- LC filters a solution generally adopted to limit power losses consists in their design with large sized components. Since the filters are often made in planar mode, that is with most of the inductive and capacitive components obtained directly in the printed circuit board, it is normal to envisage very large printed circuit boards, in which a low heat build-up required for the various components is easily obtained by increasing the surface area of the current flow. It also allows to reduce the production costs of filters, as it is possible to use materials that are not particularly sophisticated in terms of characteristics, such as dielectric constant and thermal conductivity.
- LC radio frequency filters even those manufactured using planar technology, also require customised calibration operations after being constructed and before being installed in the power transmitter. This is mainly caused by the fact that the geometry of planar inductors, which are realised with square-shaped spiral turns on the printed circuit board, is very critical, both with regard to the correct electrical dimensioning of the components and to the production of parasitic effects and out-of- band signal return.
- a further necessity of the fabrication of LC filters for power equipment arises from the development of modular broadcast transmission systems, in which the overall transmission power is obtained from one or more standardised transmitter modules, which are integrated in a support structure (cabinet with a 'bus', or common connection system) situated closely side by side.
- Each module includes all the components necessary for substantially independent operation, as well as the logic for interfacing with the support structure and the other modules in the system.
- Transmitters of this type require components that are as compact as possible, capable of being housed in an independent transmitter module, yet without sacrificing the performance, efficiency and reliability characteristics typical of high-quality broadcasting systems.
- Another object of the invention is to propose a radio frequency power LC filter which does not need calibration, but whose electrical characteristics are obtained by simple design dimensioning of the components.
- a further object of the invention is to limit the construction costs of the power LC filter low, while maintaining its performance and reliability characteristics.
- a compact LC filter for radio frequency power transmitters comprising an input terminal, an inductor and at least one capacitor, which form a resonant circuit, electrically connected to the input terminal to receive a radio frequency signal to be filtered, and an output terminal, electrically connected to the resonant circuit to carry a filtered radio frequency signal to the output.
- Two resonant circuits are connected in series. The input and output terminals and the resonant circuits are supported by a printed circuit board.
- Each capacitor is of the planar type, made by photoetching in a conductive layer of the printed circuit board, and each inductor comprises a substantially circular evolving spiral consisting of a flat strip of metal, attached at its ends to the printed circuit board, substantially parallel thereto and at a predetermined distance from the conductive layer.
- FIG. 1 is a preferred circuit diagram of a low-pass LC filter made according to the invention.
- FIG. 1 is a plan view of a preferred embodiment of the filter of Figure
- FIG. 3 is a perspective view of the filter of Figure 2.
- a compact LC filter as a whole, according to the invention is indicated with 100 and is particularly suitable for use as a low-pass output filter in a radio frequency power transmitter.
- the above-mentioned compact LC filter 100 is made on a printed circuit board 10, provided with a layer of conductive material 11 on which the planar components of the filter are made, as will be described in further detail below.
- the printed circuit board is made of material with a high dielectric constant and high thermal conductivity. This makes it possible to make planar capacitor armatures on the conductive layer 11 of small dimensions, with the same required capacitance value, and to have a good transfer of the heat dissipated by the inevitable power losses caused by strong currents necessary to transfer the signal power generated by the preceding RF amplifier stage to the antenna.
- the material selected to make the printed circuit board 10 is alumina, a ceramic oxide of aluminium, characterised by a very high dielectric constant (greater than 9.5 - the materials normally used for printed circuit boards have a dielectric constant no greater than 2) and by an excellent thermal conductivity, generally greater than 12 W/m°K.
- Another usable material is a composite PTFE based material reinforced with glass fibre and a ceramic component, for example known by the technical-commercial name TC600.
- This material still has a high dielectric constant, greater than 6, and a not very high thermal conductivity, which can be compensated for by using more efficient heat sinks with a larger surface area.
- an input terminal 1 is provided, which is used to introduce the power RF signal into the filter.
- a first resonant circuit 2 connected to the input terminal 1 , comprises an inductor 21 and a capacitor 22, likewise connected to said input terminal 1 and to a common circuit node.
- a further capacitor 24 is connected in parallel to the inductor 21 .
- a second resonant circuit 2 is provided, arranged in series with the above described first circuit.
- An additional capacitor 23 is provided between the two resonant circuits, connected to the common node between the two resonant circuits 2 and to the common circuit node.
- the second resonant circuit 2 is in turn connected to an output terminal 3, aimed at transferring the filtered power RF signal to the antenna.
- circuit configurations and operation modes of LC filters are universally known, and will not be described in further detail, since their functional characteristics are irrelevant with respect to the objects of the present invention.
- the following values of the above-described components are provided: 63 nH for the inductors 21 ; 19 pF for the capacitors 22; 36 pF for the additional capacitor 23; and 10 pf for the additional capacitors 24.
- the capacitors 21 and the additional capacitor 23 are of the planar type, an armature of which is made in the conductive layer 11 of the printed circuit board 10.
- the second armature is made in a further conductive layer present in the opposite surface of the board 10, which forms the aforementioned common circuit node.
- the further capacitors 24 are of the discrete type and are soldered onto the conductive layer 11 .
- Each of the inductors 21 is advantageously air-core inductor and is fixed in a suitable position to the conductive layer 11 , parallel thereto and at a predetermined distance with respect thereto, preferably between 2 and 5 mm.
- the inductor 21 comprises a substantially circularly evolving spiral 21a consisting of a flat strip of metal (preferably, but not necessarily, silver-plated copper).
- the length of the coil 21a, the distance between consecutive turns, the width and thickness of the flat strip very precisely define the inductance value of the inductor 21 , its power transmission characteristics and its resistance to thermal stress, according to empirically defined results derived from research and field experiments.
- a spiral length of 123 mm, a flat strip width of 2 mm and a distance between consecutive turns of 1.6 mm are provided to obtain an inductor 1 with an inductance value of 63 nH, capable of operating up to a rated power of 1 .5 kW.
- the thickness of the spiral is 1 mm.
- the inductor 21 made in the above described manner is extremely stable, and its electrical and thermal characteristics can be perfectly reproduced, respecting the dimensional ratios described above.
- the above described inductor 21 is substantially free of unwanted out-of-band return.
- the inductance value for the inductor 21 of the invention is precisely defined by its geometry and by the dimensional specifications of the spiral 21a, and therefore does not require any calibration.
Abstract
The compact LC filter for radio frequency power transmitters comprises an input terminal (1), an inductor (21) and at least one capacitor (22), forming a resonant circuit (2), electrically connected to said input terminal (1) to receive a radio frequency signal to be filtered, and an output terminal (3), electrically connected to the resonant circuit (2) in order to transfer a filtered radio frequency signal to the output. Two resonant circuits (2) are connected in series. The input terminal (1) and the output terminal (2) and the resonant circuits (2) are supported by a printed circuit board (10). Each capacitor (22) is of the planar type, made by photoetching in a conductive layer (11) of the printed circuit board (10), and each inductor (21) comprises a substantially circular evolving spiral (21a) consisting of a flat strip of metal, attached at its ends to the printed circuit board (10), substantially parallel thereto and at a predetermined distance from the conductive layer (11).
Description
COMPACT LC FILTER FOR RADIO FREQUENCY POWER TRANSMITTERS
TECHNICAL FIELD
The present invention relates to the technical field of systems for radio frequency broadcasting ("Broadcasting") of signals, for example of radio or television signals.
In particular, the invention relates to a compact radio frequency LC filter with high power and very low return, particularly suitable for use in power equipment for the transmission of aforesaid radio or television signals.
BACKGROUND ART
In the technical field of radiocommunication electronics, and in particular in the field of broadcasting of radio and television signals (Broadcasting), high power radio frequency transmitters are commonly used, capable of working with antenna emission power ranging from hundreds of Watts to tens of Kilowatts. Such transmitters generally comprise feed sections, signal amplification sections and one or more LC filters, aimed at limiting the antenna emission spectrum to the required frequency band and to keep out-of-band frequencies within acceptable limits.
TECHNICAL PROBLEM
In the aforementioned transmitters, it is extremely important to keep under control the production of heat that inevitably takes place during the transfer of power during normal operation of the equipment, despite optimal circuit configurations and particularly efficient components and construction technologies. Low power dissipation is necessary to limit consumption, and thus the operating costs of the equipment, and to avoid thermal stress of the components due to the high temperatures produced by the power dissipation. This is true both for the strictly power-related components of the transmitter, such as the i
MOSFET amplifier stages, and for the passive components, such as the LC filters, and especially the output low-pass filter, which carries the power signal to the antenna.
Regarding the LC filters, a solution generally adopted to limit power losses consists in their design with large sized components. Since the filters are often made in planar mode, that is with most of the inductive and capacitive components obtained directly in the printed circuit board, it is normal to envisage very large printed circuit boards, in which a low heat build-up required for the various components is easily obtained by increasing the surface area of the current flow. It also allows to reduce the production costs of filters, as it is possible to use materials that are not particularly sophisticated in terms of characteristics, such as dielectric constant and thermal conductivity.
LC radio frequency filters, even those manufactured using planar technology, also require customised calibration operations after being constructed and before being installed in the power transmitter. This is mainly caused by the fact that the geometry of planar inductors, which are realised with square-shaped spiral turns on the printed circuit board, is very critical, both with regard to the correct electrical dimensioning of the components and to the production of parasitic effects and out-of- band signal return.
A further necessity of the fabrication of LC filters for power equipment arises from the development of modular broadcast transmission systems, in which the overall transmission power is obtained from one or more standardised transmitter modules, which are integrated in a support structure (cabinet with a 'bus', or common connection system) situated closely side by side. Each module includes all the components necessary for substantially independent operation, as well as the logic for interfacing with the support structure and the other modules in the system.
Transmitters of this type require components that are as compact as possible, capable of being housed in an independent transmitter module, yet without sacrificing the performance, efficiency and reliability characteristics typical of high-quality broadcasting systems.
OBJECTS OF THE INVENTION
It is an object of the present invention to propose a power LC filter for radio frequency equipment which is capable of assuring low current losses, and therefore limited heat generation, high cleanliness of the filtered signal due to the absence of parasitic effects and out-of-band signal return through the inductors, while having a compact construction suitable for use in high power transmitter modules.
Another object of the invention is to propose a radio frequency power LC filter which does not need calibration, but whose electrical characteristics are obtained by simple design dimensioning of the components.
A further object of the invention is to limit the construction costs of the power LC filter low, while maintaining its performance and reliability characteristics.
SUMMARY OF THE INVENTION
The above-mentioned and other objects are entirely achieved, in accordance with the content of the claims, by means of a compact LC filter for radio frequency power transmitters comprising an input terminal, an inductor and at least one capacitor, which form a resonant circuit, electrically connected to the input terminal to receive a radio frequency signal to be filtered, and an output terminal, electrically connected to the resonant circuit to carry a filtered radio frequency signal to the output. Two resonant circuits are connected in series. The input and output terminals and the resonant circuits are supported by a printed circuit board. Each capacitor is of the planar type, made by photoetching in a conductive layer of the printed circuit board, and each
inductor comprises a substantially circular evolving spiral consisting of a flat strip of metal, attached at its ends to the printed circuit board, substantially parallel thereto and at a predetermined distance from the conductive layer.
BRIEF DESCRIPTION OF THE DRAWINGS
The features of the invention will be apparent from the following description of a preferred, although not exclusive embodiment, in accordance with claims and with the help of the enclosed drawings, in which:
- Figure 1 is a preferred circuit diagram of a low-pass LC filter made according to the invention;
- Figure 2 is a plan view of a preferred embodiment of the filter of Figure
1 ;
- Figure 3 is a perspective view of the filter of Figure 2.
DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
With reference to Figures 1 and 2, a compact LC filter as a whole, according to the invention, is indicated with 100 and is particularly suitable for use as a low-pass output filter in a radio frequency power transmitter.
Since the latter is not the only use of the filter 100, although it is the use of choice, by way of example and not limitation, a preferred configuration according to the invention of a resonant two-stage low- pass LC filter will be described below. Obviously, it is understood that different configurations of filter circuits and other uses are considered to fall within the scope of the invention.
The above-mentioned compact LC filter 100 is made on a printed circuit board 10, provided with a layer of conductive material 11 on which the planar components of the filter are made, as will be described in further detail below.
According to the invention, in order to obtain the compactness of the device which is a necessary requirement, the printed circuit board is made of material with a high dielectric constant and high thermal conductivity. This makes it possible to make planar capacitor armatures on the conductive layer 11 of small dimensions, with the same required capacitance value, and to have a good transfer of the heat dissipated by the inevitable power losses caused by strong currents necessary to transfer the signal power generated by the preceding RF amplifier stage to the antenna.
In particular, the material selected to make the printed circuit board 10 is alumina, a ceramic oxide of aluminium, characterised by a very high dielectric constant (greater than 9.5 - the materials normally used for printed circuit boards have a dielectric constant no greater than 2) and by an excellent thermal conductivity, generally greater than 12 W/m°K.
Another usable material, less valuable than alumina but much less expensive, which still allows good performance and sufficient compactness and limits production costs in cases where this is a priority over optimising dimensions, is a composite PTFE based material reinforced with glass fibre and a ceramic component, for example known by the technical-commercial name TC600. This material still has a high dielectric constant, greater than 6, and a not very high thermal conductivity, which can be compensated for by using more efficient heat sinks with a larger surface area.
As for the circuit configuration of the filter 100, with reference to figure 1 , an input terminal 1 is provided, which is used to introduce the power RF signal into the filter. A first resonant circuit 2, connected to the input terminal 1 , comprises an inductor 21 and a capacitor 22, likewise connected to said input terminal 1 and to a common circuit node. A further capacitor 24 is connected in parallel to the inductor 21 .
In the illustrative filter configuration, a second resonant circuit 2 is provided, arranged in series with the above described first circuit. An additional capacitor 23 is provided between the two resonant circuits, connected to the common node between the two resonant circuits 2 and to the common circuit node.
The second resonant circuit 2 is in turn connected to an output terminal 3, aimed at transferring the filtered power RF signal to the antenna.
The circuit configurations and operation modes of LC filters are universally known, and will not be described in further detail, since their functional characteristics are irrelevant with respect to the objects of the present invention. By way of information only, for a configuration of the low-pass filter 100 which requires a cut-off frequency of 125 MHz with 3 dB attenuation, the following values of the above-described components are provided: 63 nH for the inductors 21 ; 19 pF for the capacitors 22; 36 pF for the additional capacitor 23; and 10 pf for the additional capacitors 24.
Referring now to Figures 2 and 3, according to the invention, the capacitors 21 and the additional capacitor 23 are of the planar type, an armature of which is made in the conductive layer 11 of the printed circuit board 10. For all the aforementioned capacitors, the second armature is made in a further conductive layer present in the opposite surface of the board 10, which forms the aforementioned common circuit node. By contrast, the further capacitors 24 are of the discrete type and are soldered onto the conductive layer 11 .
Each of the inductors 21 is advantageously air-core inductor and is fixed in a suitable position to the conductive layer 11 , parallel thereto and at a predetermined distance with respect thereto, preferably between 2 and 5 mm.
The inductor 21 comprises a substantially circularly evolving spiral
21a consisting of a flat strip of metal (preferably, but not necessarily, silver-plated copper). The length of the coil 21a, the distance between consecutive turns, the width and thickness of the flat strip very precisely define the inductance value of the inductor 21 , its power transmission characteristics and its resistance to thermal stress, according to empirically defined results derived from research and field experiments.
Applications on RF transmitters of rated power greater than a few hundred watts require flat strip wider than 1.5 mm and distances between two consecutive turns of the coil 21a greater than 1 .5 mm.
By way of example, a spiral length of 123 mm, a flat strip width of 2 mm and a distance between consecutive turns of 1.6 mm are provided to obtain an inductor 1 with an inductance value of 63 nH, capable of operating up to a rated power of 1 .5 kW. The thickness of the spiral is 1 mm.
Essentially, the inductor 21 made in the above described manner is extremely stable, and its electrical and thermal characteristics can be perfectly reproduced, respecting the dimensional ratios described above.
Unlike the planar inductors made by photoetching in the conductive layer 11 or the planar air-core inductors with the conventional square spiral turns, the above described inductor 21 is substantially free of unwanted out-of-band return. Unlike conventional air-core inductors with cylindrical turns, which have optimal characteristics with respect to out-of-band return, but require calibration to define their exact inductance value, the inductance value for the inductor 21 of the invention is precisely defined by its geometry and by the dimensional specifications of the spiral 21a, and therefore does not require any calibration.
It is understood that what above is an example and not a limitation, therefore possible modifications of details are considered from now on
to be within the protective scope defined by the claims below.
Claims
CLAIMS ) A compact LC filter for radio frequency power transmitters, of a type comprising an input terminal (1), at least one inductor (21 ) and at least one capacitor (22), which form at least one resonant circuit (2), electrically connected to the input terminal (1 ) in order to receive a radio frequency signal to be filtered, and an output terminal (3), electrically connected to said resonant circuit (2) in order to transfer a filtered radio frequency signal to the output, said input terminal (1 ) and output terminal (2) and at least one resonant circuit (2) are supported by a printed circuit board (10), with said compact LC filter (100) characterized in that said capacitor (22) is of planar type, made by photoetching in a conductive layer (11) of said printed circuit board (10), and that said at least one inductor (21) comprises a spiral (21a) having a substantially circular evolution consisting of a flat strip of metal, fixed at its ends to said printed circuit board (10), substantially parallel thereto and at a predefined distance from the conductive layer (11 ). ) The LC filter according to claim 1 , characterized in that said LC filter comprises a pair of said inductors (21 ) connected in series, a pair of said capacitors (22) connected to opposite terminals of said inductors (21 ), and an additional capacitor (23), connected to common terminals of said inductors (21 ), the opposite terminals of said capacitors (22,23) being connected to a common line. ) The LC filter according to claim 1 or claim 2, characterized in that the spiral (21a) of each of said inductors (21 ) has a conductor width greater than 1.5 mm and a distance between consecutive turns greater than 1 .5 mm. ) The LC filter according to any one of the previous claims, characterized in that said printed circuit board (10) is made of material having a dielectric constant greater than 6, and a thermal
9
conductivity greater than 1.1 W/mK. ) The LC filter according to claim 1 or claim 4, characterized in that said printed circuit board (10) is made of alumina. ) The LC filter according to claim 1 or claim 4, characterized in that said printed circuit board (10) is made of a composite PTFE material and is reinforced with glass fibre and ceramic material.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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IT202021000005201 | 2021-11-03 | ||
IT202100005201 | 2021-11-03 |
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WO2023079469A1 true WO2023079469A1 (en) | 2023-05-11 |
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PCT/IB2022/060580 WO2023079469A1 (en) | 2021-11-03 | 2022-11-03 | Compact lc filter for radio frequency power transmitters |
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Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2001011771A1 (en) * | 1999-08-05 | 2001-02-15 | Nikko Company | Reflectionless lc filter and method of manufacture therefor |
US6191666B1 (en) * | 1999-03-25 | 2001-02-20 | Industrial Technology Research Institute | Miniaturized multi-layer ceramic lowpass filter |
US20120212305A1 (en) * | 2011-02-21 | 2012-08-23 | John Mezzalingua Associates, Inc. | Filter circuit and method of tuning filter circuit |
-
2022
- 2022-11-03 WO PCT/IB2022/060580 patent/WO2023079469A1/en unknown
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6191666B1 (en) * | 1999-03-25 | 2001-02-20 | Industrial Technology Research Institute | Miniaturized multi-layer ceramic lowpass filter |
WO2001011771A1 (en) * | 1999-08-05 | 2001-02-15 | Nikko Company | Reflectionless lc filter and method of manufacture therefor |
US20120212305A1 (en) * | 2011-02-21 | 2012-08-23 | John Mezzalingua Associates, Inc. | Filter circuit and method of tuning filter circuit |
Non-Patent Citations (3)
Title |
---|
"Lumped Elements for RF and Microwave Circuits, Second Edition", 2002, ARTECH HOUSE, Norwood, ISBN: 978-1-63081-932-3, article BAHL INDER J: "Printed and hybrid integrated circuits inductors", pages: 118 - 135, XP093024099 * |
"Lumped Elements for RF and Microwave Circuits, Second Edition", 2002, ARTECH HOUSE, Norwood, ISBN: 978-1-63081-932-3, article BAHL INDER: "Fabrication Technologies - Lumped Elements for RF and Microwave Circuits", pages: 395 - 427, XP093024097 * |
BELL P J ET AL: "Flip-Chip-Assembled Air-Suspended Inductors", IEEE TRANSACTIONS ON ADVANCED PACKAGING, vol. 30, no. 1, February 2007 (2007-02-01), pages 148 - 154, XP011184019 * |
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