EP0337825B1 - Mikrowellensperrfilter in Mikrostreifenausführung - Google Patents

Mikrowellensperrfilter in Mikrostreifenausführung Download PDF

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Publication number
EP0337825B1
EP0337825B1 EP19890400632 EP89400632A EP0337825B1 EP 0337825 B1 EP0337825 B1 EP 0337825B1 EP 19890400632 EP19890400632 EP 19890400632 EP 89400632 A EP89400632 A EP 89400632A EP 0337825 B1 EP0337825 B1 EP 0337825B1
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EP
European Patent Office
Prior art keywords
filter
microstrip
segment
varactor
frequency
Prior art date
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Expired - Lifetime
Application number
EP19890400632
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English (en)
French (fr)
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EP0337825A1 (de
Inventor
Daniel Auffray
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Thales SA
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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 numerous signals to be processed simultaneously, typically radar signal receivers.
  • a notch filter is thus to attenuate the disturbing signals in order to be able to analyze and identify the signals of lower amplitudes.
  • a YIG filter (Yttrium-Iron Garnet: yttrium-iron garnet) has been suitably polarized for this purpose to tune it to the frequency to be eliminated.
  • tunable microwave notch filters have also been proposed based on the so-called coupled line structure, that is to say comprising a transmission line in the form of a microstrip associated with at least one filter cell comprising a microstrip segment arranged parallel to and at a distance from the transmission line.
  • the object of the invention is to remedy these drawbacks.
  • connection to the ground potential is carried out for each cell with the interposition of a tunable LC resonant circuit and the other end of the line segment is in open circuit.
  • the capacitive element of the tunable resonant circuit LC comprises a varactor, the anode of which is brought to an adjustable continuous potential, so that the control of this continuous potential allows the variation of the central rejection frequency of the notch filter.
  • the subject of the invention is a microwave band cut filter as defined in the claims.
  • 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 generator 2 of microwave signals to a load impedance 3, and there is provided at least one filtering 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 F0 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 be modified and its tuning in frequency will depend essentially on ement of the DC voltage applied to 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 F0min and a value F0max 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 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.
  • 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)

Claims (5)

  1. Höchstfrequenz-Kerbfilter in Mikrostreifenleiter-Technologie des Typs mit gekoppelten Leitungen, mit einer Übertragungsleitung in Form eines Mikrostreifens (1), der wenigstens mit einer Filterungszelle verbunden ist, die ein Mikrostreifensegment (4) aufweist, das parallel zur Übertragungsleitung und in einem Abstand von dieser angeordnet ist, wobei dieses Mikrostreifensegment mit einem ersten seiner Enden über ein variables kapazitives Element mit Massepotential verbunden ist, dadurch gekennzeichnet, daß die elektrische Länge des Mikrostreifensegmentes im wesentlichem einem Viertel der Wellenlänge der mittleren Sperrfrequenz der Filterungszelle entspricht, daß das andere Ende des Mikrostreifensegmentes ein offener Kreis ist und daß zwischen Masse und das erste Ende des Segmentes ein induktives Element (5), das in Form eines Drahtes zur Verbindung des Mikrostreifensegmentes (4) mit der Varaktordiode (6) verwirklicht ist, mit dem variablen kapazitiven Element (6) in Reihe geschaltet ist, um einen abstimmbaren LC-Resonanzkreis zu bilden.
  2. Filter gemäß Anspruch 1, dadurch gekennzeichnet, daß das kapazitive Element des abstimmbaren LC-Resonanzkreises eine Varaktordiode (6) enthält, die auf demselben dielektrischen Substrat (7) wie das Mikrostreifensegment angeordnet ist und deren Anode auf einem einstellbaren Gleichstrompotential (-V) gehalten wird, derart, daß die Steuerung dieses Gleichstrompotentials die Veränderung der mittleren Sperrfrequenz des Kerbfilters gestattet.
  3. Filter gemäß Anspruch 2, dadurch gekennzeichnet, daß das Gleichstrompotential an die Anode der Varaktordiode über ein Tiefpaßfilter (13, 14) angelegt wird.
  4. Filter gemäß einem der vorangehenden Ansprüche, dadurch gekennzeichnet, daß es außerdem Umschaltmittel enthält, um das erste Ende eines jeden Mikrostreifensegmentes (4) wahlweise, anstatt es mit Massepotential zu verbinden, zu einem offenen Kreis zu machen.
  5. Höchstfrequenz-Kerbfilter in Mikrostreifenleiter-Technologie, dadurch gekennzeichnet, daß es mehrere in Kaskade geschaltete Filter gemäß Anspruch 4 enthält, wobei die Umschaltmittel eines jeden Filters wahlweise so gesteuert werden, daß nur dasjenige/diejenigen Elementarfilter umgeschaltet wird/werden, dessen/deren Sperrfrequenz-Veränderungsbereich die zu beseitigende(n) Frequenz(en) enthält.
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 EP0337825A1 (de) 1989-10-18
EP0337825B1 true EP0337825B1 (de) 1993-11-18

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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)

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

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5063362A (en) * 1990-05-04 1991-11-05 International Business Machines Corporation Suppression of electrical interferences from an electronic circuit
FR2678450B1 (fr) * 1991-06-27 1993-09-03 Dassault Electronique Dispositif de filtrage coupe-bande hyperfrequence.
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

Family Cites Families (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

Also Published As

Publication number Publication date
DE68910719T2 (de) 1994-03-17
FR2628571B1 (fr) 1990-11-09
EP0337825A1 (de) 1989-10-18
FR2628571A1 (fr) 1989-09-15
DE68910719D1 (de) 1993-12-23

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