Adjustable directional coupler having tiltable coupling conductor

A directional coupler for coupling between four inner conductors 16,18,20,22 of four coaxial lines has two coupling conductors 10,12 which are connected across respective pairs of inner conductors 20,22,16,18, and are spaced apart to define a coupling gap 14. The width of the coupling gap can be varied by tilting movement of one, and preferably both coupling conductors which are attached to the respective inner conductors by tilting joints in the form of leaf springs 124. A modification (FIGS. 4,5) enables the coupler to be used for crossed coaxial lines.

The invention relates to a directional coupler having band-like coupling 
conductors guided in air and with coupling into both sides of the coupling 
conductors. In a known directional coupler of this kind, the coupling 
attenuation can be varied by adjusting the mutual separation of the 
coupling conductors to vary the coupling gap defined therebetween. The 
central plane of the coupling gap formed between the broad sides of the 
coupling conductors includes the axes of the coaxial conductor system and 
can be adjusted by means of mechanical adjusting members. The coupling 
conductors are rigidly constructed and secured via resiliently deformable 
members to fixedly arranged terminal ends of the inner conductors of the 
coaxial lines. The resiliently deformable members allow movement of the 
coupling conductors relative to the terminal ends of the inner conductors. 
Directional couplers of this kind which are known from German Pat. No. 24 
34 144 make it possible, in a space-saving construction, to vary the 
coupling attenuation by sensitive adjustment of a coupling gap which is of 
constant cross-section over the whole length of the coupling. Moreover, it 
is possible to use almost the entire length of the housing for the 
coupling conductors so that the dimensions of the housing of the coupler 
depend essentially only on the length of the coupling conductors. 
In the arrangement of the above-mentioned German patent, the resiliently 
deformable members are, however, constructed in such a way that relative 
movement of the coupling conductors occurs in the direction of the 
associated inner conductors of the coaxial lines. Provision has to be made 
to accommodate this movement and leads to an increase in the complexity of 
the coupler. 
The principal object underlying the present invention is to be able to 
sensitively adjust the coupling gap within wide limits without producing a 
radial displacement of the inner conductor sections and to ensure a simple 
mechanical construction. This object is accomplished by an arrangement in 
which the resiliently deformable members form tilting joints the axes of 
tilting of which extend parallel to the axes of the coupling conductors, 
i.e. to the axis of the coupling gap. 
The fact that the coupling conductor is tilted means that the terminals can 
be rigidly constructed so that no radial displacement of the inner 
conductor sections is necessary. In this connection the arrangement can be 
such that a tilting movement of one of the coupling conductors results in 
the two coupling conductors being mutually inclined to one another. 
In order to avoid this inclined position both coupling conductors can be 
tiltable with respect to one another in such a way that their coupling 
planes remain parallel in every tilted position. 
The tilting joints which are usefully formed by leaf springs can be 
arranged, in accordance with a first embodiment of the invention, between 
the inner conductor terminals of the coaxial lines and the coupling 
conductors in place of the parallel bands provided in the aforementioned 
German patent. This arrangement means that the coaxial lines leading to 
each coupling conductor must be arranged on the same side of the coupling 
gap. It is, however, frequently desirable for the coupling conductors to 
cross over each other i.e. for the inner conductor terminals associated 
with each coupling conductor to be arranged on opposite sides of the 
coupling conductor. 
This situation can be catered for by an arrangement in which a resiliently 
deformable member in the form of a leaf spring is clamped at two 
oppositely disposed sides in clamping slots formed in at least one of the 
coupling conductors and a fixed conductor section which extends parallel 
to the coupling conductor and is connected to the associated inner 
conductor terminals. Unrestricted movement of the leaf spring between the 
clamping slots is ensured by forming a widened cut-out in at least one of 
the coupling conductor and the conductor section. 
In this arrangement a tiltable coupling conductor can once again face a 
rigid coupling conductor or, alternatively, two coupling conductors which 
are tiltable and parallel to one another can be used. Naturally this kind 
of tiltable mounting of the coupling conductor is not restricted to 
arrangements in which the inner terminal members lie on opposite sides of 
the associated clamping conductor but can also be used for a directional 
coupling in which the two terminal conductors associated with one coupling 
conductor both lie on the same side of that coupling conductor.

The drawings show only the inner conductor system of a coaxial directional 
coupler constructed in accordance with the invention. This system is 
surrounded, as in the embodiment shown in German Pat. No. 24 34 144, by an 
outer conductor system which has positioning members in order to be able 
to adjust the coupling gap by adjusting the position of the coupling 
conductors. 
The coupling gap 14 is defined between the coupling conductors 10 and 12 
and the coupling attenuation can be selected by adjusting the width of the 
coupling gap i.e. the mutual spacing of the coupling conductors. As can be 
seen from the embodiment FIGS. 1 and 2, the terminal ends 16, 18 of two 
inner conductors of two coaxial lines are rigidly connected to, or formed 
in one piece with, the two ends of the coupling conductor 12. As 
illustrated, the inner conductor terminals 16,18 extend in the same 
direction and are connected to the coupling conductor 12 from the same 
side and at right angles thereto. The inner conductor terminals could also 
be arranged on the same side of the coupling conductor 12 and be inclined 
thereto. 
The coupling conductor 10 is tiltably connected, via respective leaf 
springs 24 which lie in the plane of the coupling gap parallel thereto, to 
the terminal ends 20,22 of two inner conductors of two coaxial guides 
which are arranged on the other side of the coupling gap. These leaf 
springs 24 make it possible for the coupling conductor 10 to tilt from the 
position shown in full lines to the position shown in chain dotted lines 
in FIG. 2. In the tilted position the coupling conductors admittedly no 
longer lie exactly parallel to one another, this can, however, be 
tolerated in many cases. If, however, a parallel position of the coupling 
conductors is required in every coupling position then the arrangement 
shown in FIG. 3 can be used. In the arrangement of FIG. 3 the coupling 
conductor 12' which lies opposite to the coupling conductor 10 is also 
tiltably connected to the adjoining coupling conductor 16', and to the 
corresponding inner conductor terminal at the other end of the coupling 
conductor 12', via leaf springs 24'. The parallelism of the two coupling 
conductors can be maintained for any width of the coupling gap by tilting 
the coupling conductors in the same sense which can be achieved by 
externally actuatable positioning members 26. 
The embodiments of FIGS. 1 to 3 are suitable for a directional coupler in 
which the pairs of coaxial connection lines to each coupling conductor 
approach that conductor at an angle or at right angles from the same side 
or in which the connection lines extend in the direction of the coupling 
conductors. The embodiment of FIGS. 4 and 5 is a suitable for applications 
in which the coaxial connecting lines to each coupling conductor approach 
that coupling conductor from opposite directions. In this embodiment the 
coupling conductor 110 is tiltably connected via a leaf spring 124 to a 
rigid conductor section 111 which is disposed in the coupling zone and 
which is rigidly connected with inner conductor terminals 120 and 122, or 
formed in one piece with these inner conductor terminals, which extend 
away from the coupling conductor in opposite directions. 
The spring 124 is clamped in slot 125 of the coupling conductor 110 by set 
screws 127. The other side of the leaf spring is clamped into a slot 129 
of the conductor section 111 by set screws 131. In order to ensure free 
movability of the coupling conductor 110 the clamping slot is widened to a 
slot recess 133 between the clamping zones defined by screws 127 and 131 
and a gap 135, which is bridged by the leaf spring 124, is provided 
between the facing edges of the coupling conductor 110 and the conductor 
section 111. In this way it is possible for the coupling conductor 110 to 
tilt freely via the leaf spring 124 when engaged by an appropriate 
positioning member. The re-setting of the coupling conductor usefully 
takes place through the re-setting force of the leaf spring 124. 
FIGS. 4 and 5 show only a single coupling conductor. This coupling 
conductor co-operates with a second coupling conductor of mirror image 
symmetry which can be rigidly constructed in accordance with the 
embodiment of FIGS. 1 and 2 so that the coupling conductor 110 adopts an 
angle relative to this neighbouring coupling conductor when tilted. 
Alternatively, both coupling conductors can be constructed in accordance 
with FIGS. 4 and 5 so that they can both be tilted along the lines of the 
embodiment of FIG. 3 in such a manner that the parallelism of the coupling 
conductors is maintained and the coupling gap has the same width at all 
positions along the coupling conductors. FIG. 5 illustrates such a second 
coupling conductor 112 with mirror image symmetry, wherein all other 
elements corresponding to those of the first conductor 110 are similarly 
numbered with primed numbers. The galvanic connection between the terminal 
conductors and the coupling conductor 110 takes place via the leaf spring 
124. In order to improve the galvanic contact, additional contact springs 
137 can be provided with the additional contact springs being screwed to 
the rigid conductor sections and having angled sprung ends which project 
into the gap 139 between the coupling conductor 110 and the terminal 
conductor 122. 
In the embodiment of FIGS. 4 and 5 the terminal conductors 120 and 122 are 
lead away to opposite sides of the coupling conductor. They could, 
however, be led away to the same side in the same manner as for the 
embodiments of FIGS. 1 to 3, i.e. the tiltable coupling conductor 110 
could also be inserted into a conductor section rigidly connected to the 
associated inner conductor terminals 20,22, (this is not shown in the 
drawings). Clearly the coupling conductor associated with the second 
coupling conductor could also be connected in the same manner to the inner 
conductor terminals 16,18.