EP0337825A1 - Mikrowellensperrfilter in Mikrostreifenausführung - Google Patents

Mikrowellensperrfilter in Mikrostreifenausführung Download PDF

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Publication number
EP0337825A1
EP0337825A1 EP89400632A EP89400632A EP0337825A1 EP 0337825 A1 EP0337825 A1 EP 0337825A1 EP 89400632 A EP89400632 A EP 89400632A EP 89400632 A EP89400632 A EP 89400632A EP 0337825 A1 EP0337825 A1 EP 0337825A1
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EP
European Patent Office
Prior art keywords
filter
microstrip
varactor
potential
tunable
Prior art date
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Granted
Application number
EP89400632A
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English (en)
French (fr)
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EP0337825B1 (de
Inventor
Daniel Auffray
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Thales SA
Original Assignee
Thomson CSF SA
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Publication date
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00—Auxiliary devices
    • H01P1/20—Frequency-selective devices, e.g. filters
    • H01P1/201—Filters for transverse electromagnetic waves
    • H01P1/203—Strip line filters

Definitions

  • the present invention relates to a microwave band cut filter in micro-band technology.
  • Tunable microwave notch filters are used in particular in instantaneous very broadband microwave receivers generally having many signals to be processed simultaneously, typically radar signal receivers. Because of the very large instantaneous band, the signals are very often disturbed by the presence of strong parasitic signals which saturate the reception chains. The function of a notch filter is thus to attenuate the disturbing signals in order to be able to analyze and identify the signals of lower amplitudes. These disturbing signals generally having neither a frequency known in advance nor a stable frequency, it is necessary to provide a notch filter which is tunable.
  • a YIG filter (Yttrium-Iron Garnet: yttrium-iron garnet) has been used for this purpose, polarized appropriately to tune it to the frequency to be eliminated.
  • This technique despite its interesting performance (high rejection rate, low attenuated bandwidth), has the disadvantage of significantly increasing the dimensions and mass of the circuit and presenting a transition time ("rallying time”). ) relatively long, on the order of 10 to 20 ms, and to require a complex control circuit.
  • One of the aims of the present invention is to provide a tunable microwave notch filter which has electrical properties comparable to YIG filters, but which eliminates the aforementioned drawbacks.
  • the invention makes it possible to combine the following advantages: - low rejection out-of-band insertion losses, - broadband operation, compatible with the performance of current reception channels (typically, bandwidth from 2 to 18 GHz), - large frequency tuning range, - high rejection at the tuning frequency, - tuning system without power consumption, - very short rally time, - very small dimensions, allowing easy integration into microelectronics.
  • the present invention uses the basic structure known as coupled lines, that is to say comprising a transmission line in the form of a microstrip associated with at least one filtering cell comprising a microstrip segment disposed parallel to the line of transmission and at a distance therefrom, this microstrip segment having one of its ends in open circuit and the other connected to the ground potential.
  • connection to the ground potential is carried out for each cell with the interposition of a tunable LC resonant circuit.
  • the capacitive element of the tunable resonant circuit LC comprises a varactor, the anode of which is brought to an adjustable DC potential, so that the control of this DC potential allows the variation of the central rejection frequency of the notch filter. .
  • the inductive element of the tunable LC resonant circuit is produced in the form of a wire connecting the microstrip segment to the varactor, that being placed on the same dielectric substrate as this microstrip segment; - the continuous potential is applied to the anode of the varactor with the interposition of a low-pass filter; - the ratio of possible extreme rejection frequencies is at least equal to 1.5; the filter further comprises switching means for selectively placing said other end of each microstrip segment in open circuit instead of connecting it to the ground potential;
  • FIG. 1 shows the structure, in itself known, of a notch filter of the type known as "with coupled lines" produced in microstrip technology: such a filter comprises a transmission line 1 in the form of a microstrip connecting a microwave signal generator 2 to a load impedance 3, and there is provided at least one filter cell (five, in the example illustrated) formed by a microstrip segment 4 arranged parallel to the transmission line , and having an electrical length corresponding substantially to a quarter of the wavelength at the central rejection frequency which it is desired to give to the filter. Each of the segments 4 has one of its ends in open circuit and the other directly connected to the ground potential.
  • the attenuation provided by such a filter is illustrated in FIG. 2, the central frequency FO being determined by the length of each segment 4 and the bandwidth rejected depending on the number of cells and the coupled line impedance of each d 'between them.
  • the direct connection to earth of one of the ends of each segment is replaced by a resonant LC circuit formed by an inductor 5 in series with an adjustable capacity 6, this circuit constituting therefore a charge for the coupled line.
  • the adjustable capacity 6 consists of a varactor, the cathode of which is connected to ground and the anode of which is connected on the one hand to one of the terminals of the inductor 5 and on the other hand to a negative continuous potential source -V (the respective potentials -V1, -V2, ...
  • the tuning frequency of the resonant circuit LC will vary with the control voltage of the varactor, the operation of the filter will then be modified and its tuning in frequency will essentially depend on the DC voltage ap plicated with the varactor (of course, for a filter with several cells, all the potentials -V1, -V2, etc.
  • FIG. 4 The attenuation provided by such a filter is illustrated in FIG. 4, where it can be seen that the attenuation curve is similar to that of FIG. 2, but that its central frequency can move between a value FOmin and a value FOmax as a function of the potential applied to the cathode of the varactor, the minimum frequency being obtained for the maximum capacity of the varactor, itself corresponding to the lowest control potential.
  • the control circuits of the tuning frequency of the filter will become particularly simple, in particular compared to the tuning circuits currently used for filters tunable to YIG.
  • a five-cell filter has been shown of which all the LC circuits are similar, this number of five cells is in no way limiting, and essentially depends on the selectivity that is desired for the filter (by increasing the number of cells, we restrict the width of the ejected strip), the space available on the substrate to integrate the cells, etc.
  • FIG. 5 shows how it is possible without difficulty to produce the filter of the present invention with the integration techniques known in microelectronics.
  • the filter is for example produced on a dielectric substrate 7 of alumina (relative permittivity of 9.8) of small thickness, the lower face 8 of which is metallized so as to constitute both the ground plane and the mechanical support of the circuit .
  • Transmission line 1 is a conventional transmission line, with an impedance close to 50 ⁇ , comprising a microstrip extending between an entry point 9 and an exit point 10.
  • each segment 4 On either side of this line 1, five microstrip segments 4 have been distributed forming a coupled line; the tunable filter was therefore produced with five cells but, as we have just indicated, this number largely depends on the final electrical characteristics that one wishes to obtain. Opposite these segments 4 are provided throttles 11, 11 and 12, 12 allowing, in known manner, to adjust the impedances (in even and in odd mode) of each of the coupled lines. One end of each segment 4 is in open circuit, while the other end is connected by a connecting wire 5 to the cathode of a varactor 6, this connecting wire forming the inductance 5 of the diagram of the figure 3.
  • the varactor 6 is preferably a component produced in the form of a micropave carried over to the surface; the cathode of the varactor is connected to ground by means of a metallized via 16 connecting the circuit area on which the micropavé is welded to the underlying ground plane 8.
  • the continuous potential -V is applied to the anode of the varactor by means of a low-pass filter comprising a decoupling capacitor of high capacity 13 and a connecting wire 14 of considerable length constituting an impedance of high value, passing above a trench 15 delimiting the microwave circuits proper and the dielectric alumina substrate; the voltage control circuit of the varactors is thus made completely neutral in the microwave domain.
  • the filter switchable by replacing the series resonant circuit with a parallel resonant circuit and by varying the polarity of the voltage applied to the varactors.
  • a five-cell filter was produced with the layout of FIG. 5, intended to operate under the following operating conditions: - characteristic impedance 50 - bandwidth (excluding rejected frequency): 2 to 18 GHz, - possible tuning range: 7 to 10 GHz, - bandwidth attenuated to - 25 dB: 300 MHz.
  • FIGS. 6 and 7 both represent the response of the filter (FIG. 6 for the entire width W of the operating band; FIG. 7 in the range of variation of the filter).
  • the frequency of the filter can vary, substantially logarithmically as a function of the voltage applied to the varactor, between approximately 6.5 and 9.8 GHz, with an attenuated bandwidth w from 240 MHz to -25 dB and a maximum rejection of around -40 dB, values substantially constant whatever the tuning frequency.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Control Of Motors That Do Not Use Commutators (AREA)
EP19890400632 1988-03-11 1989-03-07 Mikrowellensperrfilter in Mikrostreifenausführung Expired - Lifetime EP0337825B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8803187 1988-03-11
FR8803187A FR2628571B1 (fr) 1988-03-11 1988-03-11 Filtre coupe-bande hyperfrequence en technologie micro-bande

Publications (2)

Publication Number Publication Date
EP0337825A1 true EP0337825A1 (de) 1989-10-18
EP0337825B1 EP0337825B1 (de) 1993-11-18

Family

ID=9364182

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19890400632 Expired - Lifetime EP0337825B1 (de) 1988-03-11 1989-03-07 Mikrowellensperrfilter in Mikrostreifenausführung

Country Status (3)

Country Link
EP (1) EP0337825B1 (de)
DE (1) DE68910719T2 (de)
FR (1) FR2628571B1 (de)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0454992A2 (de) * 1990-05-04 1991-11-06 International Business Machines Corporation Entstörung für elektrische Beeinflussung aus elektronischer Schaltung
FR2678450A1 (fr) * 1991-06-27 1992-12-31 Dassault Electronique Dispositif de filtrage coupe-bande hyperfrequence.
JP2008078734A (ja) * 2006-09-19 2008-04-03 Mitsubishi Electric Corp 周波数可変ｒｆフィルタ

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4004257A (en) * 1975-07-09 1977-01-18 Vitek Electronics, Inc. Transmission line filter
US4467296A (en) * 1982-08-23 1984-08-21 Loral Corporation Integrated electronic controlled diode filter microwave networks
US4468644A (en) * 1982-09-23 1984-08-28 General Instrument Corp. Tunable reject filter for radar warning receiver

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4004257A (en) * 1975-07-09 1977-01-18 Vitek Electronics, Inc. Transmission line filter
US4467296A (en) * 1982-08-23 1984-08-21 Loral Corporation Integrated electronic controlled diode filter microwave networks
US4468644A (en) * 1982-09-23 1984-08-28 General Instrument Corp. Tunable reject filter for radar warning receiver

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
1985 IEEE - MTT-S INTERNATIONAL MICROWAVE SYMPOSIUM DIGEST, 4-6 juin 1985, St. Louis, Missouri, pages 531-534, IEEE, New York, US; M. MEHDIZADEH et al.: "High speed varactor tuned notch filter" *
IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, vol. MTT-30, no. 9, septembre 1982, pages 1361-1367, IEEE, New York, US; I.C. HUNTER et al.: "Electronically tunable microwave bandstop filters" *

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0454992A2 (de) * 1990-05-04 1991-11-06 International Business Machines Corporation Entstörung für elektrische Beeinflussung aus elektronischer Schaltung
EP0454992A3 (en) * 1990-05-04 1991-11-21 International Business Machines Corporation Suppression of electrical interferences from an electronic circuit
FR2678450A1 (fr) * 1991-06-27 1992-12-31 Dassault Electronique Dispositif de filtrage coupe-bande hyperfrequence.
WO1993000718A1 (fr) * 1991-06-27 1993-01-07 Dassault Electronique Dispositif de filtrage coupe-bande hyperfrequence accordable
GB2263583A (en) * 1991-06-27 1993-07-28 Dassault Electronique Tunable microwave bandstop filter device
US5448210A (en) * 1991-06-27 1995-09-05 Dassault Electronique Tunable microwave bandstop filter device
GB2263583B (en) * 1991-06-27 1995-09-06 Dassault Electronique Tunable microwave bandstop filter device
JP2008078734A (ja) * 2006-09-19 2008-04-03 Mitsubishi Electric Corp 周波数可変ｒｆフィルタ
JP4650897B2 (ja) * 2006-09-19 2011-03-16 三菱電機株式会社 周波数可変ｒｆフィルタ

Also Published As

Publication number Publication date
FR2628571A1 (fr) 1989-09-15
FR2628571B1 (fr) 1990-11-09
DE68910719D1 (de) 1993-12-23
DE68910719T2 (de) 1994-03-17
EP0337825B1 (de) 1993-11-18

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