EP0431234A1 - Schnell abstimmbarer Bandpassfilter in Kammleitungsform - Google Patents

Schnell abstimmbarer Bandpassfilter in Kammleitungsform Download PDF

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Publication number
EP0431234A1
EP0431234A1 EP89830542A EP89830542A EP0431234A1 EP 0431234 A1 EP0431234 A1 EP 0431234A1 EP 89830542 A EP89830542 A EP 89830542A EP 89830542 A EP89830542 A EP 89830542A EP 0431234 A1 EP0431234 A1 EP 0431234A1
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EP
European Patent Office
Prior art keywords
pass
band
filter
speedy
type
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP89830542A
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English (en)
French (fr)
Inventor
Giovanni Bianchi
Giuseppe Pinto
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Elettronica SpA
Ital Elettronica SpA
Original Assignee
Elettronica SpA
Ital Elettronica SpA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
Application filed by Elettronica SpA, Ital Elettronica SpA filed Critical Elettronica SpA
Priority to EP89830542A priority Critical patent/EP0431234A1/de
Publication of EP0431234A1 publication Critical patent/EP0431234A1/de
Withdrawn legal-status Critical Current

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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
    • H01P1/205—Comb or interdigital filters; Cascaded coaxial cavities

Definitions

  • the present invention relates to improvements in combline-­type filters. More specially, it relates to improvements in band-pass speedy tunable filter of the combline-type the elec­trical circuit of which is provided with semiconductor devi­ces so connected that: the junction capacity of each one is liable to controllable variation dependent on the controlled variation of the applied reverse tension of polarization; a corresponding variableness of the center frequency of the pas­sing band is thereby possible; a band-pass speedy tunable filter of the combline type is consequently realized.
  • the resulting output signal is only light­ly attenuated; when, on the contrary, the frequency of the in­put signal is very different in respect to the resonance fre­quency, the output signal results greatly attenuated, so that the combline-type filter assumes the characteristic of a "band-­pass filter".
  • the center frequency f o namely the resonance frequency, depends substantially on the cited head capacity C, with an inverse proportionalty. It is also important to note that the center frequency f o assumes generally a fixed value depending on the selected fixed value of the head capacity C.
  • the main object of the invention is to overcome the disadvantageous fixed value of the center frequency f o depending on the fixed value of the so-called head capacity C of a combline-type filter according to the prior art.
  • the fundamental structure of a combline-type filter for microwave according to the prior art is now replaced with an innovated structure in accordance with the present invention.
  • a set of resonators is provided in a combline arrangement, one end of each resonator being earthed, for example, by a single metal strap for all resonators, while the opposite end of each one is connected to a respective semiconductor device and then in series to a controllable capacity C, which is liable to varia­tion by controlling the reverse (direct) tension of polariza­tion.
  • a source of direct current is provided in order for sup­plying a reverse tension V c in the range of 0 to plus/minus 20 V as desired and controlled by the operator,through sui­table control rheophore and connecting wires.
  • junction ca­pacity C dependent on the applied reverse tension of polari­zation.
  • the junction capacity C decreases when the applied reverse tension increases; and on the ground of/the recalled formula cited above, the decrease of the junc-tion capacity C causes a corresponding increase of the center fre­quency f o .
  • the important innovating features of the invention are eviden­ced by graphic representations of the frequeny on Cartesian co-­ordinates, generally referred to the applied reverse tebsion of polarization, or the attenuation of the input signal (ordinate), and the corresponding response frequency (abscissa).
  • the increa­sing values of the center frequency f o dependent on the sequentially controlled application of the reverse tension lie generally along a line parallel to the abscissa.
  • a remarkable characteristic to be point out for this combline-ty­pe filter concerns the time necessary to notice a desired varia­tion of the junction capacity after the reverse tension has been controlled. In effect, there is a very short delay from the mo­ment such a reverse tension has been controlled by the operator, to cause the variation of the junction capacity, such a delay being in the range of nanoseconds. Because of its remarkable fea­tures the combline-type filter according to the invention is, in effect, a band-pass speedy tunable filter which may overcome the difficulties arising from the prior art in this field.
  • the invention solves the very important problem of how to design practically a band-pass speedy tunable filter of the combline-ty­pe wherein the "head capacity" does not have a fixed value and therefore a single center frequency f o , this latter being, on the contrary, liable to variation, which depends on the reverse tension of polarization controlled by the operator.
  • FIG.1 A fundamental structure of conventional combline-type filter according to the prior art is shown in fig.1 and shortly descri­bed hereafter so that the comparison may be made with a combline-­type filter in accordance with this invention.
  • fig.1 a set of three resonators are supposed in a combline arrangement wi­thin the cavity of a metal container 11.
  • the resonators have their lower ends solidly connected to the inner wall of the cavity and thereby earthed, while the opposite end of ech one is connected to the facing inner wall of the cavity through an intermediate capacity C inserted therebetween.
  • Each resonator has his own inductance LR1, LR2, LR3, respectively as well as coupling inductance LaE and LaU are provided in connection to the power input E and power output U, respectively.
  • the intermediate capacity is in­dicated by the reference character C and symbolizes the head ca­pacity of such a combline-type filter.
  • the center frequency f o of the passing band is expressed by the well known formula reported hereabove, which gives the resonance condition and is bound to the inductance LR and capacty CR of the resonators, and depends on the head capa­cty, or tuning capacity C of the filter.
  • FIG. 2 A typical example of structure of a microwave filter in accordan­ce with the innovating features of the invention, namely the con­trollable variation of the head capacity and thereby the corre­sponding variation of the center frequency of the filter, is shown schematically in figs. 2 to 4, wherein such a filter is in­dicated with the reference number 20. It was assumed that this filter is provided with a set of three resonators R1, R2, R3 in combline arrangement upon an insulating bed 24 placed on the flat upper surface of a base 21 of a rectangular metal support mem­ber 21-22 having a thick square shaped projecting part 22 which according to figs.2 to 4 forms the left longitudinal side of the support member.
  • Insulating bed 24 is leaning against the inner face of the projecting part 22, and the surfaces of these two elements 22, 24 are substantially complanar in order for being covered by a suitable metal strap 23 which covers and solidly connects therebetween either one end of the resonators and the corresponding part of the metal projecting element 22. In this manner such ends of the resonators are earthed.
  • a semiconductor device is connected to each free end of the resonators R1, R2, R3 to exploit the variability of the junction capacity of such a device, the variation being controlled by the opera­ tor, by suitably regulating the applied reverse tension on which the junction capacity depends.
  • MESFET-, HEMT-, or VARACTOR-type Semiconductor devices suitable to satisfy the controllable va­riation of such junction capacity were found of the MESFET-, or HEMT-, or VARACTOR-type, specifically suitable to realize varia­tions of capacity through variations of reverse tension, and for­med on gallium arsenide (GaAs).
  • GaAs gallium arsenide
  • Each selected semiconductor device is inserted between the reso­nator R and the by-pass capacity CB according to the electrical circuit 50, schematically shown in fig.5.
  • the resonators R1, R2, R3 have been assumed as having: its own inductance LR1, LR2, LR3, respec­tively; input coupling inductance LaE and output coupling induc­tance LaU; and inductance M between the adjacent resonators.
  • By-pass inductances LB1, LB2, LB3 are provided between respecti­ve semiconductor devices D1, D2, D3 and the positive of a di­rect voltage source V c to be controlled by the operator for rea­lizing as desired the variation of the reverse tension of po­larization on which is depending the variation of the junction capacity of the semiconductor devices.
  • the desired variation of the junction capacity happens with a very short delay from the moment that such reverse tension has been controlled by the ope­rator, such very short delay being in the range of nanoseconds.
  • R1, R2, R3 are the resonators placed upon the upper surface of an insulating bed 24 in a combline arrangement, this lat­ter being, in turn, placed on the flat base 21 of the main metal support member 21-22;
  • LaE, LaU are the input- and output-inductances, respectively, of the resonators, these coupling inductances being assumed along straight lines;
  • D1, D2, D3 are semiconductor devices of the MESFET-, or HEMT-, or VARACTOR-type;
  • CB1, CB2, CB3 are by-pass capacities; 25 indicates the control rheophore to vary the reverse ten­sion of polarization to be applied for varying as desi­red the junction capacty, and after all the center fre­quency f o of the filter at the resonance condition;
  • LB1, LB2, LB3 are the resonators placed upon the upper surface of an insulating bed 24 in a combline arrangement, this lat­ter being, in turn,
  • FIG.9 An example of such a system 40 is shown in fig.9 wherein a fil­ter according to the invention is connected to some representa­tive blocks of following instruments: 41 - pulse generator 42 - oscillator 43 - detector 44 - oscilloscope
  • a selection of semiconductor devices D1, D2, D3 is possible, the MESFET-, or HEMT-, or VARACTOR-type being preferred on the ground of experiments in this connection.
  • the selection may be extended to other com­ponents of the filter in accordance with this invention, and figs.11 to 15 evidence, among other possible modifications, some possibilities concerning: the earthing connection of the resonators; the inductive as well as the capacitive coupling.
  • An earthing connection of the resonators provided: - through a single metal strap for all resonator (fig.11a) - trough a single metal strap for each resonator (fig.11b) - by through-holes (fig.11c)
  • the inductive coupling of these latter with filter-input E and filter-output U may be performed : - through a straight connecting line between input E and the first resonator, as well as between the third resonator and the filter output U, this third resonator being, in this exam­ple of embodiment, the last resonator of the filter (fig.12); - through a bent connecting line (fig.13) while the capacitive coupling may be provided: - as indicated by the character c between the filter input E and the first resonator, and between the last resonator and the filter output U (fig.14); - a "transformer" coupling may also be provided (fig.15).

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Control Of Motors That Do Not Use Commutators (AREA)
EP89830542A 1989-12-07 1989-12-07 Schnell abstimmbarer Bandpassfilter in Kammleitungsform Withdrawn EP0431234A1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP89830542A EP0431234A1 (de) 1989-12-07 1989-12-07 Schnell abstimmbarer Bandpassfilter in Kammleitungsform

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP89830542A EP0431234A1 (de) 1989-12-07 1989-12-07 Schnell abstimmbarer Bandpassfilter in Kammleitungsform

Publications (1)

Publication Number Publication Date
EP0431234A1 true EP0431234A1 (de) 1991-06-12

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EP89830542A Withdrawn EP0431234A1 (de) 1989-12-07 1989-12-07 Schnell abstimmbarer Bandpassfilter in Kammleitungsform

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1691443A1 (de) * 2005-02-09 2006-08-16 NTT DoCoMo INC. Koppelstruktur, Resonatoranregungsstruktur und Filter für eine koplanare Schaltung
ITRM20090022A1 (it) * 2009-01-23 2010-07-24 Sie Soc It Elettronica Equalizzatore a curva di trasferimento variabile
CN105977587A (zh) * 2016-07-07 2016-09-28 电子科技大学 一种微波可调腔体滤波器

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3327255A (en) * 1963-03-06 1967-06-20 Bolljahn Harriette Interdigital band-pass filters
US4721932A (en) * 1987-02-25 1988-01-26 Rockwell International Corporation Ceramic TEM resonator bandpass filters with varactor tuning

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3327255A (en) * 1963-03-06 1967-06-20 Bolljahn Harriette Interdigital band-pass filters
US4721932A (en) * 1987-02-25 1988-01-26 Rockwell International Corporation Ceramic TEM resonator bandpass filters with varactor tuning

Non-Patent Citations (4)

* Cited by examiner, † Cited by third party
Title
15th EUROPEAN MICROWAVE CONFERENCE-PROCEEDINGS 12-15 september 1988,Stockholm,SE;Microwave Exhibitions and Publishers Ltd,Kent,GB,1988; J.-L.CAZAUX et al.:"The use of double heterojunction diodes in monolithic phase shifters" pages 1005-1010 *
1987 IEEE MTT-S INTERNATIONAL MICROWAVE SYMPOSIUM DIGEST,Vol.2,june 9-11,1987,Las Vegas,US; IEEE,New York,US,1987 K.CHANG et al.:"Varactor-tuned microstrip ring resonators" pages 867-870 *
IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES. vol. 30, no. 9, September 1982, NEW YORK US pages 1354 - 1360; I.C.HUNTER ET AL.: "Electronically tunable microwave bandpass filters" *
MICROWAVE JOURNAL. vol. 22, no. 12, December 1979, DEDHAM US pages 60 - 61; J.A.G.MALHERBE: "An etched digital elliptic filter" *

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1691443A1 (de) * 2005-02-09 2006-08-16 NTT DoCoMo INC. Koppelstruktur, Resonatoranregungsstruktur und Filter für eine koplanare Schaltung
US7397331B2 (en) 2005-02-09 2008-07-08 Ntt Docomo, Inc. Coupling structure, resonator excitation structure and filter for coplanar-waveguide circuit
CN100466374C (zh) * 2005-02-09 2009-03-04 株式会社Ntt都科摩 共面平面电路内耦合结构、谐振器激励结构以及滤波器
EP2065964A1 (de) * 2005-02-09 2009-06-03 NTT DoCoMo, Inc. Koppelstruktur, Resonatoranregungsstruktur und Filter für eine koplanare Schaltung
ITRM20090022A1 (it) * 2009-01-23 2010-07-24 Sie Soc It Elettronica Equalizzatore a curva di trasferimento variabile
WO2010084519A1 (en) * 2009-01-23 2010-07-29 Elettronica S.P.A Equalizer with a variable transfer curve
CN105977587A (zh) * 2016-07-07 2016-09-28 电子科技大学 一种微波可调腔体滤波器

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