EP0053986A2 - Bandpassfilter, welches auf eine bestimmte Anzahl einzelner Frequenzen in einem breiten Frequenzbereich abstimmbar ist - Google Patents

Bandpassfilter, welches auf eine bestimmte Anzahl einzelner Frequenzen in einem breiten Frequenzbereich abstimmbar ist Download PDF

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Publication number
EP0053986A2
EP0053986A2 EP81401956A EP81401956A EP0053986A2 EP 0053986 A2 EP0053986 A2 EP 0053986A2 EP 81401956 A EP81401956 A EP 81401956A EP 81401956 A EP81401956 A EP 81401956A EP 0053986 A2 EP0053986 A2 EP 0053986A2
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EP
European Patent Office
Prior art keywords
sections
cut
cuts
internal
coaxial
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Withdrawn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
EP81401956A
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English (en)
French (fr)
Other versions
EP0053986A3 (de
Inventor
Gilles Beauquet
Vasudéo Devarhubli
Gérard Dubost
Michel Jacques Robert Nicolas
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.)
Safran Aircraft Engines SAS
Original Assignee
Societe Nationale dEtude et de Construction de Moteurs dAviation SNECMA
SNECMA SAS
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.)
Filing date
Publication date
Application filed by Societe Nationale dEtude et de Construction de Moteurs dAviation SNECMA, SNECMA SAS filed Critical Societe Nationale dEtude et de Construction de Moteurs dAviation SNECMA
Publication of EP0053986A2 publication Critical patent/EP0053986A2/de
Publication of EP0053986A3 publication Critical patent/EP0053986A3/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Withdrawn legal-status Critical Current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
    • H01P1/202—Coaxial filters

Definitions

  • Bandpass filter tunable over a predetermined number of discrete frequencies distributed over a wide frequency band.
  • the subject of the present invention is a bandpass filter tunable over a predetermined number of discrete frequencies distributed over a wide frequency band, comprising at least one coaxial resonant cavity defined by an external conductor and an internal conductor.
  • bandpass filters made from at least one resonant cavity constituted by a coaxial line comprising an internal conductor and an external conductor and terminated by a short circuit, input coupling means or outlet being associated with the cavity.
  • the passband of such a filter is very narrow and the tuning means on a determined frequency of this passband are constituted by mechanical adjustment means.
  • Microwave bandpass filters have also been produced constituted by a single coaxial line divided into several adjacent resonant cavities separated by coupling members such as pistons, a tuning device being provided for each resonator and a coupling adjustment device being associated with each coupling member between two successive resonant cavities.
  • Such a type of filter can thus constitute a standard element which can be adapted to slightly different frequencies in a frequency band, by manual adjustments of the position of the pistons forming coupling members for example, or by action on other parameters of the geometry of the system.
  • hyper filters tunable rod frequencies comprising waveguide sections divided into several adjacent resonators by curtains of conductive rods and comprising a mechanical tuning device for each resonator such as an adjustable position dielectric stick and a coupling setting for each curtain of rods, such as a metal screw.
  • the present invention specifically aims to make it possible to produce a band-pass filter, essentially constituted by a coaxial cavity, the practically instantaneous tuning of which is possible for a certain number of discrete frequencies distributed in a wide frequency band.
  • a coaxial bandpass filter is thus essentially characterized in that at least one of the internal and external conductors of the coaxial cavity is divided into sections separated by cuts constituted by annular slots whose thickness is very small compared to the wavelength corresponding to the average frequency of the pass band and in that each section comprises at least one reactive tuning element and at least one switching element arranged in the vicinity of the cut of the section corresponding to selectively short-circuit this cut or insert the reactive tuning element of the corresponding section in response to electronic control means.
  • Each tuning reactive element consists of a portion of open or short-circuited coaxial line produced in an internal conductor or external conductor section.
  • the cavities of revolution formed in sections of internal or external conductor for producing an open or short-circuited coaxial line have transverse dimensions much greater than the thickness of a cut but small compared to the wavelength corresponding to the average bandwidth frequency.
  • the present invention thanks to a coaxial resonant cavity with predetermined geometric characteristics, it is possible to achieve, without manual action on mechanical adjustment elements, an almost instantaneous tuning of the cavity on a discrete tuning frequency chosen from a large number of predetermined frequencies distributed in a wide frequency band, thanks to a selective action for each of the switches associated with the breaks, which by an all-or-nothing command allow the closing of a break or its opening with the commissioning of the associated reactive element. It follows that with N cuts, the number of discrete frequencies for which it is possible to achieve a tuning of the resonant cavity amounts to 2 N , taking into account the possible combinations of states (open or closed) of the N cuts established using associated switches controlled by digital electronic tuning means.
  • each section several switching elements supplied with parallel are regularly distributed along the cut to achieve the short-circuiting of said cut or the insertion of a reactive element.
  • the switching elements consist of electromagnetic relays whose dimensions are small with respect to the average operating wavelength, and which are arranged in the immediate vicinity of the annular slots constituting the cuts between sections.
  • the switching elements are constituted by PIN diodes arranged in the immediate vicinity of the annular slots constituting the cuts between sections.
  • the control of the switching elements is effected by direct current by means of insulated conductor wires decoupled from the high frequency and incorporated in the internal or external conductors.
  • the dimensions of the coaxial cavity, those of the reactive elements of the N sections and the position of the N cuts are determined to define an approximately constant law Af, where f denotes any one of the 2 N discrete frequencies agreement obtained by the selective insertion of the N reactive elements and & .f represents the average of the differences between this frequency f and the adjacent frequencies among the 2N possible frequencies.
  • the bandpass filter according to the invention can be used in the most diverse applications but is advantageously applied to the connection to a single aerial, of several transmitters or receivers working on different frequencies.
  • FIG. 1 represents the basic configuration of a bandpass filter according to the invention divided, by way of example, into four sections S 1 to S4 .
  • the coaxial cavity of the filter of Fig 1 has an external body or conductor 1 closed by a cover 2 which is screwed onto the body 1.
  • the internal conductor 3 is divided into sections (Si to S 4 ) separated by cuts 1 1 to 14 having the form of annular slots whose thickness e is very small compared to the wavelength corresponding to the average frequency of the passband of the filter.
  • This configuration is possible if the internal conductors 3 and external 1 are for example produced in several superposed sections such as 301,302,303 or 101,102,103 respectively (Fig 3) screwed into each other.
  • a part 101 of external conductor can be connected to a part 102 by a screw connection lOla, 102b, the part 102 superimposed on a part 103 being itself connected to the latter by a screw connection 102a, 103b.
  • .the 301,302,303 sections of inner conductor 3 may be joined together by portions 3 0 1a, 302b and 302a, 303b are screwed into each other.
  • the positions of the joint planes are only determined by machining conveniences and only intervene in the operation with respect to electromagnetic waves the location of cuts such as 12,13,12 ', 13' as well as the forms cavities such as 22,23, 22 ', 23'. Consequently, in FIGS. 1 and 2, the lines of separation between the various parts constituting the internal 3 and external 1 conductors of the coaxial cavity have not been shown, but only the cuts such as 11 to 14, which define the differential your sections S1 to S4.
  • the external 1 and internal 3 metal conductors can be made, for example, of brass.
  • each section S 1 to S 4 comprises a tuning reactance 21 to 24 incorporated in the internal conductor 3 and which can be put into service at the level of the corresponding cut 11 to 14.
  • a reactance okay can be constituted by a short-circuited coaxial line (reactances 22, 23, 24) which is equivalent to a self inductance or by an open line (reactance 21) which is equivalent to a capacity.
  • the open coaxial line 21, which constitutes the tuning reactance of the first section S 1 is centered by means of a cylindrical sleeve 4 made of a dielectric material.
  • second, third and fourth sections S 2 , S 3 , S 4 are themselves constituted by three portions of coaxial lines in the air short-circuited, defined by annular cavities whose shapes and dimensions can be diverse.
  • the transverse dimensions of the cavities 21 to 24 must therefore have non-negligible transverse dimensions, although always small compared to the wavelength to avoid parasitic modes of the TE or TM type.
  • At least one switch 31, 32, 33, 34 is associated with each cut 11, 12, 13, 14 and makes it possible either to short-circuit this cut by closing a contact. 41,42,43,44, that is to allow the insertion of the tuning reactance 21,22,23,24 included in the section S 1 , S 2 , S 3 , S 4 corresponding to this cut-off.
  • the effective tuning frequency of the filter depends on the state of the switches 31 to 34 and can be chosen from a large number of discrete frequencies even for a relatively small number N of cuts, since the number of discrete frequencies possible agreement depends on the combination of different states possible of the different cuts and is thus worth 2 N , each cut allowing the putting into service or not of a tuning reactance.
  • a cavity can operate in the UHF band (225 to 400 MHz).
  • the dimensions of the coaxial cavity constituting the filter, the position of the cutouts 11 to 14 and the dimensions of the reactances 21 to 24 can be optimized to achieve an approximately constant law ⁇ f, f denoting any of the N tuning frequencies and ⁇ f being the average of the differences between this frequency and the adjacent tuning frequencies.
  • Table II gives the list of the discrete tuning frequencies obtained with the example of a four-section filter defined above, as a function of the state of the cuts 11 to 14.
  • the letter F represents a short-circuited closed cut while that the letter 0 represents an open cut ensuring the insertion of a tuning reactance.
  • Table II indicates in MHz the theoretical frequency Ft, the frequency F e obtained experimentally and the difference F e - Ft.
  • FIG. 1 shows an example of a filter with four sections S1 to S 4 and four annular slots forming cuts 11 to 14, the invention naturally takes into account filters of this type having a different number of sections, and thus having a number different from tuning frequencies.
  • Figure 2 like Figure 3 further show that the cuts can be made both in the external conductor .1 in the internal conductor 3 of the coaxial cavity.
  • the annular cavities 22 ', 23', 24 'formed in the external conductor 1 to produce coaxial lines forming the tuning reactances associated with the cuts 12', 13 ', 14' respectively are not necessarily identical to. those (12,13,14) formed in the corresponding internal part of the internal conductor 3.
  • the cavities 12 ′, 13 ′, 14 ′ could also be used alone, independently of the cavities 11 to 14 of the internal conductor 3, these last remaining for example short-circuited.
  • the switches 31 to 34, 32 'to 34' actuating the contacts 41 to 44, 42 'to 44' to define the open or closed state of a cut 11 to 14, 12 'to 14' can be electromagnetic relays. However, preferably small PIN diodes are used. In general, the dimensions of the switching elements 31 to 34, 32 'to 34' must be small with respect to the operating wavelength and these switching elements must be placed in the cavity as close as possible of the slot ring to short-circuit.
  • the switches (31 to 34, 32 'to 34') are controlled by direct current by means of insulated conductors (not shown) arranged either in the axis of the central element 3 or in the wall of the element outside 1 of the coaxial cavity of the filter.
  • a system for decoupling conductors supplied with direct current, consisting of capacitors, makes it possible to isolate the high frequency from the outside.
  • the switches (31 to 34, 32 'to 34') are preferably each composed of a plurality of elements regularly distributed along the cut (11 to 14, 12 'to 14') corresponding and supplied in parallel.
  • a plurality of short-circuit elements such as 31, 41 arranged symmetrically (for example four elements 31, 41 distributed at 90 ° from one another) and supplied in parallel ensures a better distribution of currents.
  • the electronic circuits making it possible to determine the selective supply of the various switches 31 to 34, 32 'to 34' fixing the state of the cuts 11 to 14, 12 'to 14' according to the discrete frequency of tuning chosen, can be composed of very common logic circuits.
  • FIG. 2 shows an example of an input or output coupling, produced by a small antenna 9 (capacitive coupling) connected to a coaxial base 1 0 .
  • the bandpass filter according to the invention makes it possible in particular to make the connection of several transmitters, or receivers working on different frequencies, at a single air.
  • the field of application of such a filter is nevertheless much wider in the field of telecommunications, and another application may lie, for example, in the suppression of parasitic noise.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Control Of Motors That Do Not Use Commutators (AREA)
EP81401956A 1980-12-10 1981-12-09 Bandpassfilter, welches auf eine bestimmte Anzahl einzelner Frequenzen in einem breiten Frequenzbereich abstimmbar ist Withdrawn EP0053986A3 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8026217A FR2495844A1 (fr) 1980-12-10 1980-12-10 Filtre passe-bande accordable sur un nombre predetermine de frequences discretes reparties dans une large bande de frequences
FR8026217 1980-12-10

Publications (2)

Publication Number Publication Date
EP0053986A2 true EP0053986A2 (de) 1982-06-16
EP0053986A3 EP0053986A3 (de) 1982-07-21

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP81401956A Withdrawn EP0053986A3 (de) 1980-12-10 1981-12-09 Bandpassfilter, welches auf eine bestimmte Anzahl einzelner Frequenzen in einem breiten Frequenzbereich abstimmbar ist

Country Status (5)

Country Link
US (1) US4472695A (de)
EP (1) EP0053986A3 (de)
JP (1) JPS57123701A (de)
FR (1) FR2495844A1 (de)
WO (1) WO1986003890A1 (de)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5065121A (en) * 1988-03-29 1991-11-12 Rf Products, Inc. Switchable resonator device
JP2000151207A (ja) * 1998-11-12 2000-05-30 Mitsubishi Electric Corp 低域通過フィルタ

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3444485A (en) * 1967-03-17 1969-05-13 Bell Telephone Labor Inc Single adjustment,variable selectivity-constant frequency coaxial transmission line filter
US3927347A (en) * 1974-03-22 1975-12-16 Varian Associates Microwave tube using electronically tunable cavity resonator
US4004257A (en) * 1975-07-09 1977-01-18 Vitek Electronics, Inc. Transmission line filter

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2630490A (en) * 1946-01-03 1953-03-03 Paul I Richards Coaxial transmission line filter
US3546633A (en) * 1966-01-04 1970-12-08 Gen Electric Electrically tunable microwave band-stop switch
US3569874A (en) * 1967-08-28 1971-03-09 Nippon Electric Co Microwave switching device employing a reed switch element
US4066988A (en) * 1976-09-07 1978-01-03 Stanford Research Institute Electromagnetic resonators having slot-located switches for tuning to different frequencies
US4179673A (en) * 1977-02-14 1979-12-18 Murata Manufacturing Co., Ltd. Interdigital filter
US4127829A (en) * 1977-03-28 1978-11-28 Microwave Development Labs. Inc. Fail-safe power combining and switching network

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3444485A (en) * 1967-03-17 1969-05-13 Bell Telephone Labor Inc Single adjustment,variable selectivity-constant frequency coaxial transmission line filter
US3927347A (en) * 1974-03-22 1975-12-16 Varian Associates Microwave tube using electronically tunable cavity resonator
US4004257A (en) * 1975-07-09 1977-01-18 Vitek Electronics, Inc. Transmission line filter

Also Published As

Publication number Publication date
WO1986003890A1 (fr) 1986-07-03
JPS57123701A (en) 1982-08-02
FR2495844B1 (de) 1984-05-11
US4472695A (en) 1984-09-18
EP0053986A3 (de) 1982-07-21
FR2495844A1 (fr) 1982-06-11

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Inventor name: DEVARHUBLI, VASUDEO

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Inventor name: BEAUQUET, GILLES