DE1219139B - Electromechanical filter - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. CL:

H03h

German AI .: 21g-34

Number: 1219 139

File number: N18914IXd / 21g

Arrival day; September 15, 1960

Opening day: June 16, 1966

The invention relates to an electromechanical filter, its mechanical oscillating system Is rotationally symmetrical and its damping characteristics damping poles at frequencies has in the immediate vicinity of the filter passage area. Such a filter has opposite an embodiment in which the oscillating bodies are connected to one another by means of elastic coupling rods that are soldered on are connected, the advantage that the diameter and the lengths of the different filter elements have it checked very precisely and thus an exact matching transmission characteristic can be reached·

From French patent specification 1113 648 it is already known that the, between converter and Clamping located resonator parts exert an influence on the transmission characteristics. From this patent specification and from the journal "RCA Review" - X, 3, September 1949, p. 348 bis 365, the expert knows how an optimal locking effect can be achieved with the least amount of constructive effort The resulting mounting location for the resonators is to be found, which is decisive for the damping poles are.

In order to generate a strong attenuation peak immediately below or directly above the transmission range, which increases the blocking steepness of the transmission characteristic, it is known, secondary resonators to couple with parts of the filter, between its coupling with electromechanical transducers lie. However, this leads to difficulties in structural terms and has the disadvantage that none exact reproducibility can be maintained. This with the accuracy that is required in practice The object of the invention is to avoid any solder joints.

In the case of an electromechanical filter, its damping characteristics are damping poles at frequencies in the immediate vicinity of the filter passage area and its mechanical oscillation system, which consists of resonators and coupling elements, is rotationally symmetrical, is this achieved according to the invention in that between the pinch point and the with the Converter-coupled resonator a coaxial rotationally symmetrical generating a damping pole Resonator is attached, which consists of two rotationally symmetrical and cylindrical ones connected via coupling rods Bodies consists, the first as a half-wave length resonator or in whole multiples of a Half-wavelength resonating resonator and its second as a quarter-wavelength or a Electro-mechanical filter

ίο

Applicant:

NV Philips' Gloeüampenfabrieken,
Eindhoven (Netherlands)

Representative:

Dipl.-Ing. H, Zaepke, patent attorney,

Munich 12, Ridlerstr. 37

Named as inventor:

Jacob Frederik Klinkharner, Eindhoven;

Johan Rinkel, Hilversum (Netherlands)

Claimed priority:

Netherlands 18 September 1959 (243 515)

odd multiple of a quarter wavelength tuned oscillating body · is formed.

An improvement of the transmission in the pass band can be seen according to a development of the Invention achieve that the diameter of the resonator coupled to the transducer around about 20% smaller than that of the other resonators of the filter part located between the transducers is.

The invention is explained in more detail below using the exemplary embodiment shown in the figure explained.

The filter consists of a number of cylindrical resonators r, the lengths of which are each equal to one half of the wavelength belonging to the mean frequency of the passband or a whole multiple thereof. The resonators r are connected to one another via coupling rods, the length of which is preferably equal to a quarter wavelength or an odd multiple of this value.

The first resonator ^ is connected to a transducer ^, with the help of which electrical vibrations fed to the terminals 1 are converted into mechanical vibrations which cause torsional vibrations in the filter. In principle, two transducers oscillating in antiphase and coupled to symmetrical points on the cylinder circumference of the resonator T ₁ can be used. However, a longitudinal vibration can also be generated in a known manner in that

609 579/302

a coil is attached to the resonator ^. The transducers ^ ₁ and t ₂ are usually matched electrically and mechanically.

By coupling the last resonator r ₂ with a similar transducer t ₂ , which in turn converts the mechanical vibrations into electrical vibrations, there is known to be an electrical transmission characteristic in the form of a band with very sharp edges between the input and output terminals 1 and 2, respectively. To improve: the characteristic in the pass band of the band, in particular to reduce the attenuation fluctuations depending on the frequency within this part, the resonators r and the coupling rods k can be dimensioned with slight deviations from one another. As is known, the reduction in the edge steepness of the band filter at the blocking frequencies which occurs here can be increased by using a resonator which generates an attenuation pole directly above or directly below the passband.

Such a resonator R ₁ may be disposed between the transducer coupled resonator _x t r _x and the entrapment be attached; it forms a rotationally symmetrical body with the rest of the filter. The resonator R _x has a length equal to half the wavelength assigned to the frequency of the damping pole or an integral multiple thereof and is connected to the pinch point via a coupling rod k _x , which is preferably a quarter wavelength or an odd multiple thereof. To set the coupling between the resonators R _x and r _x , a cylindrical oscillating body L ₁ with a length of about a quarter wavelength or an odd multiple of this value via coupling rods α _χ or b _x , which is preferably also a quarter wavelength or an odd multiple of this Are long, connected to these resonators A ₁ and r _x , respectively. By correct adjustment of the diameter of this body L ₁ , the required steepness in the blocking characteristic of this filter can be obtained without the transmission in the pass band being influenced too much. An improvement in the transmission in the pass band is achieved by making the diameter of the resonator r _x approximately 20% smaller than the diameter of the other resonators r .

In a similar manner, between the r t ₂ with the transducer coupled resonator ₂ and the trains-in place of the illustrated cylindrical configuration of the different resonators may, if necessary, even complicated rotationally symmetrical shapes application. For the coupling of these resonators to one another, vibrating bodies similar to those of the bodies L ₁ or L ₂ can be used if necessary.

In a practical embodiment of a 250 kHz filter with a width of 3 kHz, these are

ίο diameter of the resonators A ₁ , R ₂ and r and the bodies L ₁ and L ₂ equal to 6,000 mm; the diameter of the coupling rods k, R ₁ , k ₂ , a _v a ₂ , b _x and b ₂ is 1.948 mm and that of the resonators r _x and r ₂ is 5.045 mm. The length of the resonators r, T ₁ and r ₂ is 5.896 mm,

that of the coupling rods k, k _x , k ₂ , a _x , a ₂ , b _x and b ₂ and the body L ₁ and L ₂ is 2.948 mm. The length of the resonator R is about 5.8 mm and that of the Resona-τητη.

tors R ₂ about 6.0]

35

40

45

Claims (2)

Patent claims: 1. Electromechanical filter, the damping characteristic of which has damping poles at frequencies in the immediate vicinity of the filter pass band and whose mechanical oscillation system, which consists of resonators and coupling elements, is rotationally symmetrical, characterized in that between the pinch point and the one with the converter (^ ₁ or . t ₂ ) coupled resonator (r _x or r ₂ ) a damping pole generating coaxial rotationally symmetrical resonator (L ₁ , R ₁ or L ₂ , R ₂ ) is attached, which consists of two coupling rods (a _x , b _x or . A ₂ , b ₂ ) connected rotationally symmetrical and cylindrical bodies (L _x and R ₁ or L ₂ and R ₂ ) , the first (R ₁ or R ₉ ) as a half-wavelength resonator or in whole multiples of a half-wavelength resonating resonator and their the second (L ₁ or L ₂ ) is designed as an oscillating body tuned to a quarter wavelength or an odd multiple of a central wavelength. 2. Electromechanical filter according to claim 1, characterized in that the diameter of the resonator (r _x or r ₂ ) coupled to the transducer is about 20 ° / o smaller than that of the other resonators (r) between the transducers (^ ₁ and t ₂ ) is the lying filter part. arranged pinch point a resonator R ₂ and an oscillating body L ₂ with coupling rods k ₂ , a ₂ , b _{2 are} attached. The attenuation pole of a resonator R _x can, for. B. immediately below that of the other, R ₂ , are immediately above the passband, or vice versa. Both attenuation poles can also be on the same side of the passband. Considered publications:
French Patent No. 1113 648;
"RCA Review", Vol. X, No. 3 (September 1949), pp. 348 to 365; Bulletin of the Yamagute University, Vol. 5, No. 2 (March 1959), pp. 335-372. 1 sheet of drawings 609 579002 6.66 © Bundesdruckerei Berlin