EP0920070B1 - Directional filter - Google Patents

Description

State of the art

The present invention relates to a directional filter, consisting of two filters with the same Filter characteristics and at least one 3 dB power divider, the same as an input signal Power shares on the two filters divides and the Output signals of the filters combined.

In active microwave assemblies is a frequency filtering e.g. between frequency converters and amplifier units necessary to disturbing Spiegelfrequenz- and Suppress oscillator signals, the used Filter also outside of the usable frequency band one largely reflection-free termination for the active Must provide circuit components. To this end are used in general directional filter.

A directional filter, as described in the introduction of two Filter with the same filter characteristics and a 3 dB power divider for splitting one Input signal power to both filters and one another 3 dB power divider for combining the Output signals of the two filters is off "Microwave Filters Impedance-Matching Networks, and Coupling Structures "by G.L. Matthaei, L. Young, E.M.T. Jones, McGraw-Hill Book Company 1964, p. 966-968.

It is now the object of the present invention, a To indicate directional filter of the type mentioned, the has a compact design and also low-attenuation is and has good selection properties.

Advantages of the invention

According to the features of claim 1, said Problem solved in that the two filters with the same Filter characteristics are designed as a waveguide filter and these waveguide filters in a planar conductive structure are integrated, wherein the at least one Input signal dividing the two filters and the Output signals of the filter combining 3 dB power divider executed in planar line technology and is coupled to the waveguide filters.

By using waveguide filters can be very meet high selection requirements (blocking frequency band approx. 3% next to the usable frequency band). With a planar Filter structure can not be such a good selection realize, as well as not a very small Insertion loss, as achievable with waveguide filters is. Because even slight fluctuations in the properties of Substrate material lead to strong fluctuations in the Filter characteristic, which is very disadvantageous in particular a series product is. With waveguide filters can be realize optimal filter characteristics, in particular because attenuation poles at arbitrary frequencies in the stopband can be realized. Because all the rest Circuit components realized in planar line technology be, results in a very space-saving Circuitry, with very high demands on the Quality of the directional filter can be fulfilled.

Advantageous developments of the invention will be apparent from the Subclaims forth.

A very compact arrangement is obtained by the fact that the Waveguide filters are part of a housing that is the receptacle a substrate of the planar line structure is used. So can e.g. the waveguide filters of two half-shells consist of which a half-shell in the lid of the Housing and the other half-shell in the bottom of the housing is integrated and that the substrate with the at least one 3 dB power divider in the dividing plane between the two Half shells lie.

Preferably, the coupling of at least one planar 3 dB power divider to the waveguide filters in that input and output line arms of the 3 dB power divider on tongue-like extensions of the substrate extend, which protrude into the waveguide filter.

The directional filter may be constructed so that a first 3 dB power divider the input signal to the two Waveguide filter with bandpass characteristic divides and that a second 3 dB power divider outputs the output signals combined waveguide filter.

Another embodiment is that a single 3 dB power divider the input signal to the two Waveguide filter with belt stop characteristic divides and that the same 3 dB power divider that of the two Waveguides reflected signals combined.

Description of exemplary embodiments

Figur 1 einen ersten Querschnitt A-A,

Figur 2 einen zweiten Querschnitt B-B durch ein Richtungsfilter mit zwei 3-dB-Leistungsteilern,

Figur 3 einen Querschnitt durch ein Richtungsfilter mit einem 3-dB-Leistungsteiler und

Figur 4 einen Ausschnitt aus einem Richtungsfilter mit einer Variante zur Ankopplung eines planaren 3-dB-Leistungsteilers an ein Hohlleiterfilter.

On the basis of several embodiments shown in the drawings, the invention is explained in more detail below. Show it:

FIG. 1 shows a first cross section AA,

FIG. 2 shows a second cross section BB through a directional filter with two 3 dB power dividers,

3 shows a cross section through a directional filter with a 3 dB power divider and

Figure 4 shows a section of a directional filter with a variant for coupling a planar 3-dB power divider to a waveguide filter.

In FIGS. 1 and 2, two are mutually orthogonal Sections shown by a directional filter. there the section A-A shown in FIG. 1 runs parallel to it a partially illustrated substrate 1 with a planar line structure of a microwave circuit. In the Substrate 1, two waveguide filters 2 and 3 are inserted, which both have the same filter characteristic for a Have directional filter. The waveguide filter 2 or the Waveguide filters 3 each have several Cavity resonators 21, 22, 23, 24 and 31, 32, 33, 34, which via coupling apertures 25, 26, 27, 28 and 35, 36, 37, 38th coupled together. The number and location of Cavity resonators and coupling diaphragms of the two Waveguide filters 2 and 3 is chosen so that a desired filter characteristic results.

On the substrate 1 is in a planar Line technology executed first 3 dB power divider 4, the an input signal on its input line 41 its two output lines 42 and 43 in equal parts divides. The output line 42 of the 3 dB power divider is connected to the waveguide filter 2 and the output line 43 at the waveguide filter 3 coupled. The coupling of each Output line 42 and 43 to the respective waveguide filter 2 or 3 takes place in that they are on a tongue-shaped extension 44 and 45 of the substrate. 1 extending into the first cavity 21 and 31, respectively of the waveguide filter 2 and 3 protrudes. Like the one in FIG 2 illustrated cross-section B-B illustrates the projecting tongue-shaped extension 45 through a slot 6 in the Hollow wall of the cavity resonator 31 in this. The idle end of the output line 43 on the tongue-shaped extension 45 acts like a Coupling antenna. The same applies to the tongue-shaped Extension 74 and the extending thereon idle End of the output line 42.

In the illustrated embodiment, the 3 dB power divider a so-called Wilkinson divider. Whose both output lines 42 and 43 are of an ohmic Resistor 46 bypassed. So with this divider between the output signals of the two output lines 42 and 43 a required phase difference of 90 ° arises exists between the two output lines 42 and 43 a Length difference of λ / 4. Instead of a Wilkinson divider but can also use any kind of 3 dB power dividers become.

The output signals of the two waveguide filters 2 and 3 are combined via a second 3 dB power divider 5. These are the two input lines 52 and 53 of the 3-dB power divider 5 in the same way to the two Waveguide filters 2 and 3 coupled like the Output lines 42 and 43 of the first 3 dB power divider 4. The input line 52 extends on a tongue-shaped extension 54, in the cavity resonator 24th of the first waveguide filter 2 protrudes, and the Output line 53 extends on a tongue-shaped Extension 55, in the cavity 34 of the second Waveguide filter 3 protrudes. The example of Input line 53 is shown in Figure 2 that the tongue-shaped extension 55 with the end of the input line 53 through a slot 7 in the cavity 34th protrudes. Also the second 3 dB power divider is for example, as a Wilkinson divider executed in which the Input lines 52 and 53 from a resistor 56th are bridged.

The cross-sectional view B-B in Figure 2 can be seen, that the substrate 1 on its the line structure opposite side in a known manner with a Ground surface 8 is provided. This ground surface 8 is connected to the Waveguide filters 2 and 3 contacted where the tongue-shaped extensions 44, 45, 54 55 through slots 6, 7th in the waveguide walls in the cavity resonators 21, 31, 24, 34 lead into it. Here, the ground surface 8 is below the in the cavity resonators 21, 31, 24, 34 protruding Ends of the lines 44, 45, 54, 55 removed.

As FIG. 2 shows, the substrate 1 is in a housing 9 housed, consisting of a bottom part 91 and a Cover part 92 is made. A very compact arrangement results when the two waveguide filters 2 and 3 in such split two half shells that the first half shell the two filters 2 and 3 on the bottom part 91 and the second Half shell is integrated on the cover part 92. The substrate 1 with the planar line structure runs in the parting plane 10 between the two half-shells of the waveguide filter second and 3. This results in a very simple installation of the Waveguide filters 2 and 3 with the 3 dB power dividers 4 and 5 on the substrate 1. By separating the Waveguide filters 2 and 3 in two half-shells result also advantages in the production of cavity resonators the waveguide filters 2 and 3.

In the embodiment of a shown in Figure 3 Directional filter is connected to the two waveguide filters 2 and 3 a single 3 dB power divider (eg ring hybrid coupler) coupled. This 3 dB power divider has four goals 111, 112, 113 and 114. The line ends of the gates 112 and 113 are in the manner described above on the tongue-like projections 44 and 45 to the waveguide filter second and 3 docked. An input signal at gate 111 becomes equal over the 3 dB power divider 11 Power parts divided between the two gates 112 and 113. The two filters 2 and 3, in which the power components unlike the Embodiment in Figure 3 not one Bandpass characteristic but a belt stop characteristic. Accordingly, the cavity resonators 21, 22, 23, 24 and 31, 32, 33, 34 and the associated coupling apertures 25, 26, 27, 28 or 35, 36, 37, 38 of the two filters 2, 3 arranged so that the input signal is reflected in the useful frequency band. The reflected signal components at the gates 112 and 113 are combined by the 3 dB power divider 11, so that the total output power of the usable frequency band at the gate 114 is available.

In a modification of the filters 2 and 3 of FIG. 1 illustrated embodiment is connected to the Cavity resonator 24 and 34 of the filter 2 and 3 a another cavity 244 and 344 via a coupling diaphragm 244th or 345 coupled. This additional cavity 244 or 344 is at least partially with an absorber material 246 or 346 filled to frequency components outside the Nutzfrequenzbandes absorb.

FIG. 4 shows, using the example of waveguide filter 2, in that the coupling of the planar lines 42 of the 3 dB power divider not directly to the first resonator 21 of the filter must be done, but that the coupling also via a short-circuited waveguide piece 211 to the filter 2 can be done. The waveguide piece 211 is again over a coupling aperture 212 to the first cavity 21 of the Filters 2 docked. Thus, the coupling of the 3-dB power divider to the filter regardless of the planar Lead on the tongue-like continuation 44 of the substrate 1. In this way, any planar line to the filter 2 or 3 can be coupled.

Claims (6)

1. A directional filter consisting of two filters (2, 3) with the same filter characteristics and at least one 3 dB power divider (4, 5, 11) which divides an input signal between the two filters (2, 3) in equal power proportions and combines the output signals of the filters (2, 3), characterised in that the two filters (2, 3) are realised as hollow waveguide filters; and in that these hollow waveguide filters (2, 3) are integrated into a planar line structure (1), wherein the at least one 3 dB power divider (4, 5, 11) is made in planar line technology and is coupled to the hollow waveguide filters (2, 3).
2. A directional filter in accordance with claim 1, characterised in that the hollow waveguide filters (2, 3) are part of a housing (9) which serves for the reception of a substrate (1) of the planar line structure.
3. A directional filter in accordance with claim 1, characterised in that a first 3 dB power divider (4) divides the input signal between the two hollow waveguide filters (2, 3) with a band pass characteristic; and in that a second 3 dB power divider (5) combines the output signals of the two hollow waveguide filters (2, 3).
4. A directional filter in accordance with claim 1, characterised in that an individual 3 dB power divider (11) divides the input signal between the two hollow waveguide filters (2, 3) with a band stop characteristic; and in that the same 3 dB power divider (11) combines the signals reflected from the two hollow waveguide filters (2, 3).
5. A directional filter in accordance with claim 2, characterised in that the hollow waveguide filters (2, 3) consist of two half shells of which the one half shell is integrated in the cover part (92) of the housing (9) and the other half shell is integrated in the base part (91) of the housing (9); and in that the substrate (1) comprising the at least one 3 dB power divider (4, 5, 11) lies in the separation plane (10) between the two half shells.
6. A direction filter in accordance with any one of the preceding claims, characterised in that input line arms or output line arms (42, 43, 52, 53, 112, 113) of the 3 dB power divider (4, 5, 11) extend on tongue-like projections (44, 45, 54, 55) of the substrate (1), which project into the hollow waveguide filters (2, 3), for the coupling of the at least one planar 3 dB power divider (4, 5, 11) to the hollow waveguide filters (2, 3).

Images