EP0369757A2 - Wendelleiterfilter - Google Patents

Wendelleiterfilter Download PDF

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Publication number
EP0369757A2
EP0369757A2 EP89311804A EP89311804A EP0369757A2 EP 0369757 A2 EP0369757 A2 EP 0369757A2 EP 89311804 A EP89311804 A EP 89311804A EP 89311804 A EP89311804 A EP 89311804A EP 0369757 A2 EP0369757 A2 EP 0369757A2
Authority
EP
European Patent Office
Prior art keywords
helical
oscillators
harmonic
frequency
frequencies
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.)
Ceased
Application number
EP89311804A
Other languages
English (en)
French (fr)
Other versions
EP0369757A3 (de
Inventor
Masami Toko Kabushiki Kaisha Osawa
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.)
Toko Inc
Original Assignee
Toko Inc
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
Priority claimed from JP28845488A external-priority patent/JPH0666563B2/ja
Priority claimed from JP3754489A external-priority patent/JPH02217001A/ja
Application filed by Toko Inc filed Critical Toko Inc
Publication of EP0369757A2 publication Critical patent/EP0369757A2/de
Publication of EP0369757A3 publication Critical patent/EP0369757A3/de
Ceased legal-status Critical Current

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Classifications

    • 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
    • H01P1/2053—Comb or interdigital filters; Cascaded coaxial cavities the coaxial cavity resonators being disposed parall to each other

Definitions

  • the present invention relates to a helical filter which can decrease spurious response by increasing the damping of harmonics with a resonant frequency and conversely can be utilized with a high frequency by utilizing a harmonic.
  • a helical filter is constructed by electromagnetically connecting a plurality of helical coils each of whose one end is opened while the other end is grounded. More particularly, each helical coil is wound around each bobbin within a metal case and a plurality of such cases with the above-described construction are connected each other by soldering or with an adhesive. Alternatively, helical coils are wound around bobbins disposed on a common base and are covered with case which has a plurality of partition walls for separating adjacent helical coils.
  • Each helical coil functions as an oscillator and a resonant frequency is adjusted by varying the distributed capacity between the helical coil and its surrounding case.
  • the distributed capacity is varied to shift a dielectric body between the helical coil and the case and a metal screw electrically connected to the case in the vicinity of the coil.
  • the resonant frequency of all the oscillators is same and the filter is caused to resonate in response to the input signal of the resonant frequency. Furthermore the band of the filter is adjusted in response to the connection between the adjacent oscillators. The state of connection between the adjacent oscillators is varied by varying the sizes of openings of the sides of the cases between the helical coils and the partition walls.
  • the helical filters of the types described above are simple in construction and can attain a high Q, but it has a defect that they resonate at high frequencies which are odd multiples of the resonant frequency.
  • the helical filter is to resonate with an input signal with a high frequency in the vicinity of 1 GHz, the number of turns of a coil is considerably decreased so that the whole filter characteristics such as a resonant frequency, a degree of damping, a cutoff frequency and so on greatly vary from one helical filter to another. As a result, productivity is degraded and the helical filters cannot be satisfactorily used in practice.
  • the primary object of the present invention is to simultaneously solve the above problems.
  • a first object of the present invention is to provide a helical filter which can damps considerably of a signal of harmonic so that spurious response can be substantially eliminated.
  • a second object of the present invention is to provide a helical filter which can be used at high frequency by conversely utilizing a harmonic.
  • a harmonic frequency is varied by varying the length of a coil in an oscillator and even when a distributed capacity is adjusted to maintain the resonant frequency at a predetermined frequency, the harmonic frequency is varied by varying the length of the coil.
  • the present invention was made based upon the above-­described newly found out facts and is characterized in that a resonant frequency or a harmonic frequency of each oscillator is made equal while the other is made different in a helical filter comprising a plurality of interconnected helical oscillators.
  • FIG. 1 is a view used to explain a first preferred embodiment of the present invention
  • FIG. 2 a diagram illustrating an equivalent circuit thereof
  • FIG. 3 illustrates resonance characteristics of respective oscillators
  • FIG. 4 shows a characteristic of the first embodiment.
  • helical coils L1 and L2 have different length, respectively, and housed within a metal case 1.
  • a partition wall 3 between the helical coils L1 and L2 has an opening 2.
  • the distributed capacity C1 exists between the helical coil L1 and the case 1 while the distributed capacity C2 exists between the helical coil L2 and the case 1.
  • a helical oscillator 4 is constructed by the coil L1 and the distributed capacity C1 equivalently connected in parallel while an oscillator 5 is constructed with the coil L2 and the distributed capacity C2.
  • one end of the coil L1 is opened while the other end thereof is connected to a grounded terminal 6 with a tap being connected to an input terminal 7.
  • one end of the coil L2 is opened while the other end thereof is connected to a grounded terminal 8 with a tap being connected to an output terminal 9.
  • the coupling between the coils L1 and L2 produces an equivalent capacity Ck which represents the coupling condition between the oscillators 4 and 5.
  • the resonant frequencies of the oscillators 4 and 5 are selected in the vicinity of 250 MHz. This adjustment is carried out by screws 10 made of a metal and connected to the case 1 and movable vertically at the upper ends of the coils L1 and L2.
  • the harmonics of the oscillators 4 and 5 which are three times as high as the resonant frequency exist in the vicinity of 850 MHz and 650 MHz.
  • the characteristic of the oscillator 4 is represented by the solid line while that of the oscillator 5, by the dotted line, but the oscillators 4 and 5 have the same characteristic in the vicinity of the resonant frequency so that the characteristic is represented by the solid line.
  • FIG. 1 Component parts such as bobbins around which are wound the coils L1 and L2, nuts in threadable engagement with the screws 10 and other parts which do not constitute the present invention are not shown in FIG. 1.
  • the grounded terminal 6, the input terminal 7, the grounded terminal 8 and the output terminal 9 are extended from a common base 11, but it is of course apparent to those who are skilled in the art that such pin type terminals are replaced by flat connectors which can be directly connected to an electrical conductive pattern of a circuit substrate (not shown).
  • the filter characteristic in response to an input signal of the helical filter with the above-mentioned construction is shown in FIG. 4.
  • the frequencies of three helical oscillators are made different from each other in the vicinity of high harmonic frequencies so that three peaks appear and consequently the signal is damped.
  • each helical oil is wound around a bobbin exactly in the form of a helix.
  • a helical coil L4 is wound from the uppermost winding groove 31 to the lowermost winding groove 31 for a plurality of times.
  • the lower end of the helical coil L4 is connected to a grounded terminal while the upper end thereof is opened.
  • an oscillator can be constructed.
  • a helical coil can be wound in such a way that its turns are spaced apart from each other, but it is also possible that a helical coil is wound with the adjacent turns being made into intimate contact with other.
  • a helical coil can be formed by connecting conductor patterns through insulating films by utilizing the laminated inductor technique.
  • FIGS. 7-9 a fourth embodiment of a helical filter in accordance with the present invention in which all oscillators have the same harmonic frequency, but have different resonant frequencies, respectively, will be described.
  • FIG. 7 is a view used to explain the fourth embodiment
  • FIG. 8 is a diagram of an equivalent circuit thereof
  • FIG. 9 illustrates the characteristic thereof.
  • helical coils L5 and L6 have the same length and are covered with a metal case 51 with a partition wall 53 with an opening 52 being disposed between the coils L5 and L6.
  • the distributed capacity C3 exists between the helical coil L5 and the case 1 while the distributed capacity C4, between the helical coil L6 and the case 1.
  • a helical oscillator 54 is constructed with a coil L5 and the distributed capacity C3 equivalently connected in parallel with the coil L5 while another oscillator 55, with the coil L6 and the distributed capacity C4.
  • One end of the coil L5 is opened while the other end thereof is connected to a grounded terminal 56 with a tap being connected to an input terminal 57.
  • one end of the helical coil L6 is opened while the other end thereof is connected to a grounded terminal 58 with a tap being connected to an output terminal 59.
  • An equivalent capacity C kl is obtained by the coupling between the coils L5 and L6 and represents the coupling condition between the oscillators 54 and 55.
  • the resonant frequencies of the oscillators 54 and 55 are selected at frequencies in the vicinity of 250 MHz, but they are slightly different from each other by varying the distributed capacities C3 and C4.
  • the oscillator 55 it is provided a metal screw 60 which is always in contact with a case 51 and vertically moves the upper side of the coil L5, thereby adjusting the distributed capacity C4.
  • another oscillator 54 is not provided with such screw and the resonant frequency of the oscillator 55 is higher than that of the oscillator 54.
  • a harmonic frequency three times as high as the resonant frequency of each oscillator exists in the vicinity of 750 MHz.
  • bobbins around which are wound the coils L5 and L6, a nut for engagement with the screw 60 and other parts which do not constitute the present invention are not shown.
  • the grounded terminal 56, the input terminal 57, the grounded terminal 58 and the output terminal 59 are extended from a common base 61.
  • the helical filter with the above-mentioned construction has a filter characteristic in response to an input signal as shown in FIG. 9.
  • the harmonic frequency of the resonant frequency is determined by the length of the coil in each oscillator. Furthermore, the resonant frequency is hardly affected by the harmonic frequencies and is adjusted by the adjustment of the distributed capacity. When the harmonic frequencies of the oscillators are made different from each other, the signal is considerably damped so that the adverse effect of spurious response on the signal at the resonant signal can be eliminated.
  • the oscillators may have the same harmonic frequencies, but different resonant frequencies so that the helical filter is so constructed as to resonate at a harmonic frequency.
  • the resonant frequency is not different from the conventional one so that the number of turns of a helical coil is not necessary to extremely decrease as in the case of increasing the resonant frequency, so that the variation in filter characteristics can be avoided. Therefore the frequency which is used is not limited to a low resonant frequency, but can be increased to a high frequency.

Landscapes

  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Inductance-Capacitance Distribution Constants And Capacitance-Resistance Oscillators (AREA)
  • Control Of Motors That Do Not Use Commutators (AREA)
EP19890311804 1988-11-15 1989-11-15 Wendelleiterfilter Ceased EP0369757A3 (de)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
JP288454/88 1988-11-15
JP28845488A JPH0666563B2 (ja) 1988-11-15 1988-11-15 ヘリカルフィルタ
JP3754489A JPH02217001A (ja) 1989-02-17 1989-02-17 ヘリカルフィルタ
JP37544/89 1989-02-17

Publications (2)

Publication Number Publication Date
EP0369757A2 true EP0369757A2 (de) 1990-05-23
EP0369757A3 EP0369757A3 (de) 1991-03-27

Family

ID=26376665

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19890311804 Ceased EP0369757A3 (de) 1988-11-15 1989-11-15 Wendelleiterfilter

Country Status (1)

Country Link
EP (1) EP0369757A3 (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0492302A3 (en) * 1990-12-28 1994-06-15 For E M S P A System for filtering signals of high and low frequency bands, relevant implementation device
WO2001013460A1 (en) * 1999-08-11 2001-02-22 Nokia Networks Oy Microwave filter

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3538463A (en) * 1966-11-22 1970-11-03 Arf Products Microwave filter
US3936776A (en) * 1975-03-10 1976-02-03 Bell Telephone Laboratories, Incorporated Interspersed double winding helical resonator with connections to cavity
US4422058A (en) * 1981-11-10 1983-12-20 Motorola, Inc. Folded-over helical resonator
GB2129226B (en) * 1982-09-04 1986-02-26 Marconi Co Ltd Resonator arrangements

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0492302A3 (en) * 1990-12-28 1994-06-15 For E M S P A System for filtering signals of high and low frequency bands, relevant implementation device
WO2001013460A1 (en) * 1999-08-11 2001-02-22 Nokia Networks Oy Microwave filter
US6686815B1 (en) 1999-08-11 2004-02-03 Nokia Corporation Microwave filter

Also Published As

Publication number Publication date
EP0369757A3 (de) 1991-03-27

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