(19)
(11) EP 0 369 757 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
27.03.1991 Bulletin 1991/13

(43) Date of publication A2:
23.05.1990 Bulletin 1990/21

(21) Application number: 89311804.2

(22) Date of filing: 15.11.1989
(51) International Patent Classification (IPC)5: H01P 1/205, H01P 7/00
(84) Designated Contracting States:
DE FR GB NL

(30) Priority: 15.11.1988 JP 288454/88
17.02.1989 JP 37544/89

(71) Applicant: TOKO KABUSHIKI KAISHA
Tokyo-To (JP)

(72) Inventor:
  • Osawa, Masami Toko Kabushiki Kaisha
    Tsurugashima-Machi Iruma-Gun Saitama-Ken (JP)

(74) Representative: Dawson, Elizabeth Ann et al
A.A. THORNTON & CO. Northumberland House 303-306 High Holborn
London WC1V 7LE
London WC1V 7LE (GB)


(56) References cited: : 
   
       


    (54) Helical filter


    (57) A helical filter is constructed by coupling a plurality of helical oscillators (4, 5; 54, 55).
    The oscillators (4, 5; 54, 55) have the same resonant frequency or the same harmonic frequency and have different harmonic frequencies or resonant frequencies, respectively. The oscillators (4, 5) have the same resonant frequency by adjusting the distributed capacities (C₁, C₂) thereof, respectively, and have different harmonic frequencies by varying the lengths of coils (L₁, L₂). Furthermore the oscillators (54, 55) have different resonant frequencies by varying the distributed capacities (C₃, C₄), respectively, and have the same harmonic frequency by using coils (L₅, L₆) having same length.






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