DE1963867B2 - BAND BARRIER FILTER FOR ELECTROMAGNETIC WAVES - Google Patents

Description

»5

The invention relates to band-stop filters for electromagnetic waves with a piece of transmission conductor and at least one resonance cavity tuned to the frequency band to be blocked.

Dielectric waveguides for electromagnetic wave energy in the infrared, visible and ultraviolet Part of the spectrum of frequencies, commonly referred to as "optical" waves, are known. Such Waveguides are particularly interesting because they are very small and utilize the present available solid-state fabrication technology can be manufactured at low cost. However circuit elements must be used for this type of waveguide in order for it to be useful in a communications system be designed that are capable of both circuit functions, such as modulation, To be able to perform power distribution, channel branching, band rejection and pass-through and the like are also compatible with the waveguide structure at the same time.

A well-known band stop filter for electromagnetic waves (Journal of Applied Physics, Vol. 18, No. 8, August 1947, pp. 691 to 703) has a waveguide with a secondary branch and a cavity on. This cavity represents a volumetric resonator. When processing optical frequencies due to the very small dimensions required, it is impractical to use such a volumetric To use the cavity as a resonator.

Microwave filters usually have a transmission line with a metallic wall which is coupled by means of a pair of coupling points arranged at a distance from one another to a resonator cavity which is set to the center of the frequency band to be blocked. Such a bandstop filter is described in general terms in »Proc. NEC ", Vol. 9 (1953), pp. 833 to 840, in particular in P i g. 1 on p. 834. While a microwave coupling port such as a magnetic T or a resonant cavity can be made on the order of a wavelength, this can not be easily or economically done when considering wavelengths shorter than microwaves, relatively short coupling distances or intervals optical frequencies interconnect traveling waves and feed on directional couplers so that the coupled wave's energy propagates in only one direction within the cavity. Therefore, an optical frequency filter cannot be manufactured simply by making the dimensions of a microwave filter correspondingly small.

The invention is based on the object of designing a band-stop filter of the type specified at the outset in such a way that that it becomes useful for optical frequencies.

The task at hand is with a band stop filter for electromagnetic waves with a first transmission line and at least one towards it Blocking frequency band tuned resonance cavity solved by having the first transmission line is dielectric and that the resonance cavity is a dielectric transmission line in closed Loop and is arranged to the first transmission line that it is together with this forms two directional couplers designed to induce two striving in opposite directions, serve traveling waves in the resonance cavity.

Such dielectric lines can easily be made for dimensions as they are for frequencies well above the microwave spectrum are required. For example, materials with low Loss coefficient is deposited on a base, the materials with the low loss value have a higher dielectric constant than the surrounding and protective medium. In addition, there are losses caused by incomplete reflection at the end of the cavity are avoided by the closed loop cavity.

The invention is explained with reference to the drawing. It shows

F i g. 1 a first band stop filter,

FIG. 2 is an addition to the embodiment according to FIG. 1,

F i g. 3 a second embodiment of the band-stop filter,

F i g. 4 an addition to the embodiment according to FIG. 3,

F i g. 5 a third embodiment of a band-stop filter,

6 shows a fourth embodiment of a band-stop filter,

F i g. 6 shows a fourth embodiment and

F i g. 7 shows a fifth embodiment of a band-stop filter.

In general, the known microwave band-stop filter has a rectangular waveguide section and a resonance cavity for standing worlds, which is tuned to the center of the frequency band to be blocked. The coupling between the waveguide and the resonator cavity takes place with the aid of a pair of coupling openings arranged one behind the other at a distance. Typically, the band width of the blocked band changes as a function of both the size and the spacing of the openings.

With certain modifications due to the much shorter wavelengths at the optical frequencies

dictated are any of those described below The filter is similar to the microwave filter in that a transmission line is provided in each case. the coupling zones to a resonance cavity with the help of a pair of spaced apart coupling zones is coupled to the center of the to be speared Frequency band is tuned. While em microwave cavity with a length in the Order of magnitude of a wavelength can be produced. however, this is not the case at optical frequencies *

the bandwidth of the rejected tape changes as a function of both the distance between the coupling openings and the coupling coefficient of the openings. In the embodiment according to FIG. 1, however, the bandwidth is independent of the distance between the coupling intervals 72

. .- *, __. _{Jm coupling} coefficient.

Filter bandwidth with 2J /, so /, ± J / along dev Signal-

and 73 and

In a way, relatively short coupling intervals take on traveling wave properties at optical frequencies and become directional gherds, causing the coupled wave energy to travel in only one direction within the cavity. Because of these differences, a filter at optical frequencies cannot be made simply by dimensioning a microwave filter accordingly
Bidding

^ 72Si a first Ausf.nrungsbeispiel cine ^g band stop filter according to the invention. The filter has a transmission line formed by a dielectric strip line 70, which in turn to a figure-resonant cavity 76 along two longitudinally spaced vonemanderliegender coupling intervals 72 and 73 is' S ¹ cavity 76 can be generated in two ways. In a first embodiment, the two parts 77 and 78 of the figure eight are physically separated from one another in the crossover area with the aid of a layer of transparent dielectric material. at

a second embodiment, as this .η F. fr I

is shown, intersect the two parts 77 and

78. In this latter case the crossover occurs

of the two parts at right angles to e.ne

Avoid Ouer-coupling. .

At optical frequencies a coupling between

see ribbon cables, even over very small physical

calic intervals, a directional coupling.

Therefore, the generated between the transfer belt

lcitung70 and the hollow ribbon line75 are coupled

pclte wave energy at each of the two coupling

fntervallc a wandering wave by each of the

Coupling intervals continue in only one direction

To create a standing wave in cavity 76

53ώ ¹ So ^F ; _p rn ^O te, r ° advance in ^^^^ directions along the ribbon line 75. In the arrangement according to F, g 1 w, rd this is achieved by the figure-eight shape of the cavity 76.

During operation, a signal with a frequency compo-

several cavities can be indicated

^who i ^ 7 ' ^e _pr ^dl " ^e _s ^S _fij ^S i ^ S _orni are three cavities

76, 76 ^un * ™ "J ™ * ° _{n could} either the

^ offset against each other on pleasure

η ^ χ of the wavelength ^ _β jj _{st it} a high frequency

4? ** «Ui Ra ^ Γ divisions of half a ^. ^^^^^ the cavity is 76 * 5 wavelength>« ■ Preferably the _{nearest neighbors}

short enough night so there '^ _if

Aulerhaft resonance, of ^«a ^ _{if reduzlert is} to _{reduce% oh} .niums,

^, ^^ ^U _the arrangement according to F i g. 3 gesmd tei wmc - ™ Nahrungsmittel . _{a circular-shaped} hollow _broader ta half the size of üer _At half.

^ _n , coupling of wave force set energy m the H * '™ ^ ™

ubJ ^ gg

nform 84. The one Kopp cavity 80 and the

^ f ^ f ^ t along the ribbon line 81

Taming «befiiK g ^^ _coupling s-

fe _ei outside der_ glide _{Hohlrauni 8} 0 and the band portion 83 ™ * ™ * ™ £ _{T sdl.} Around every cross line "; ^erl _can ^α ^ Pg _is the überkreu-45 coupling to ^ve ™ ^e £ J ^a _loop either zungsste »^ e r be the ends α ^ ^ ^ _

^ formation n that ad ^ J ^it _{case) or that} the

th angle ^ envy jg ^ ^^ ^ ^. ^

₅ o X ^ i material separated from each other

The honing _room can be connected to the system for two "" in FIG. 4 is shown.

Sf, indzwd cavities 80 'and 80 "to the over-Hier ^ nJ jwe, Hohja _fc ^, _{a ek lt} .

However, directed energy and runs on the ^ pplungsbereichen in the directions out because of the eight shape of the cavity 76 to flow the two migratory waves along ^ r Bandle.tungTS hang in opposite Richtu and bi the '' ^ w standing wave to be. the cavity resonance

'Could micro wave band-stop filters enrten

«5 be den

As ^ at ⁸ den

_the ^ß _übert ragungsleitung 91 under _{zwe} longitudinally} spaced-Offn 92 and 93. Between these _ert S ragungsleitung to both the cavity along two

^. 94 _and 95 directional coupled. Embodiments according to FIGS.

through 4, the two signals coupled into the cavity 90 at the two coupling intervals flow in opposite directions.

As in the described embodiments, the cavity and the transfer δ transmission line from each other at the crossing points 92 and 93 with the help of an intermediate vei hist-poor dielectric layer physically and are electrically isolated from each other. With this latter arrangement, the angle between the Cavity and the transmission line nn the two crossing points also deviate from 90 °.

In the embodiment according to FIG. 6, the cavity 100 is in the shape of a figure eight with right-angled crossings, with each of the loops of the figure eight being symmetrically disposed on opposite sides of a cutting transmission line 101. In order to avoid any cross coupling between the ribbon line parts 102 and 103 of the cavity 100 in the crossover region 104 , the ribbon line parts 102 and 103 intersect at right angles. In order to obtain equal coupling between the transmission line and each of the ribbon line parts, the transmission line 101 penetrates the cavity in the crossover region a $ 104 so that the angle between the ribbon line parts 102 and 103 is halved.

The disadvantage of the arrangement according to FIG. 6 lies in the fact that the coupling angle between the transmission line and the cavity 100 is fixed at 45 °. However, this coupling can be reduced by adding a dielectric spacer between the cavity and the transmission line at the crossover site.

An alternative embodiment, which includes the selection of the angle of intersection between the cavity and of the transmission line is shown in FIG. 7 shown.

In the arrangement according to P i g. 7, the cavity 133 has the shape of an oval which intersects the transmission line 134 at two points 135, 136 which are longitudinally spaced from one another. To ensure equal coupling at the two interfaces, the angles of intersection between the transmission line and the cavity segments 132 and 131 are the same. The smaller the angle, the greater the coupling and the greater the bandwidth of the filter.

Although not shown, it is understood for each of the filters described above that also one Multiple cavities lying one behind the other along the wave path can be arranged to control the shape of the filter and that the cavities on each other the same frequency or tuned to mutually offset frequencies can be, depending on how this requires the individual case.

1 sheet of drawings

2387

Claims (1)

Claim: Band-stop filter for electromagnetic waves with a first transmission line and at least one resonance cavity matched to the frequency band to be blocked, characterized in that the first transmission line (70, 81, 91, 101, 134) is dielectric and that the resonance cavity (76, 80, 90, 100, 133) is a dielectric transmission line in a closed loop and is arranged in relation to the first transmission line in such a way that, together with it, it forms two directional couplers (72 and 73, 82 and 83, 94 and 95, 104, 135 and 136) , which serve to induce two traveling waves moving in opposite directions into the resonance cavity (76, 80, 90, 100, 133). 20th