DE19837025A1 - Directional coupler suitable for high-power, high-frequency amplifiers comprises parallel coplanar strips, with further coupling strip on opposite side of circuit board, dimensioned to set coupling coefficient - Google Patents

Abstract

On the other side of the substrate (1), opposite the coupling slot (s), a strip conductor (10) is located. Its width and length are selected to determine the fixed coupling coefficient.

Description

The invention relates to a directional coupler according to the preamble of the main claim.

Directional couplers, consisting of coupled planar lines, are in the various embodiments known (e.g. Meinke / Grundlach, Taschenbuch der Hochfrequenztechnik, 5th edition, page L 33, table 1). For fixed Only the so-called. broad-side coupled triplate Lines or so-called Four-wire / interdigital coupler (types b and f according to table 1 according to Meinke-Grundlach and description on page L 33, right column, lines 6 to 4 from underneath). In the case of the triplate lines coupled on the broad side, the strip conductors are attached on opposite sides of the substrate, the dielectric for the So the two striplines are different. Iriter digital couplers cannot be Manufacture entirely in printed circuit technology.

There are already so-called Coplanarly coupled striplines are known as directional couplers (Types a and c according to Table 1 by Meinke / Grundlach), but only for relative weak couplings are suitable and not for the parallel connection of High frequency amplifiers are suitable. This requires a very tight coupling.

It is an object of the invention to use a planar line technology To create directional coupler that can be manufactured entirely in printed circuit technology and which has a predetermined fixed coupling.

This task is based on a directional coupler according to the preamble of the Patent claim solved by its characteristic features.

The invention is based on a coplanar directional coupler known per se coupled strip conductors, the strip conductors as in a shielded Three-layer stripline (suspended substrate-line) attached to a substrate are arranged at a distance above a ground plane. For the desired firm  Coupling between the strip conductors is on the opposite side of the An additional substrate in the air space between the substrate and the ground plane Coupling strip line arranged. By choosing the width and length of this Coupling stripline can be the coupling between the coplanar striplines can be set arbitrarily. As a result of the known suspended substrate structure such a directional coupler is also suitable for high RF powers, for example for Parallel connection of RF amplifiers. Nevertheless, the directional coupler can be very simple and can be realized inexpensively in printed circuit technology. Because the coupled Strip lines are in the same plane on one side of the substrate, bumps of the electromagnetic field are avoided and the dielectric is the same for the two striplines. The directional coupler according to the invention has thus also very advantageous electrical properties.

The invention is illustrated below with the aid of a schematic drawing Embodiment explained in more detail.

Fig. 1 shows the plan view of a directional coupler according to the invention,

Fig. 2 shows the rear view of the substrate,

FIG. 3 shows a cross section through the directional coupler according to section line II in FIG. 1.

The directional coupler shown consists of a substrate 1 , which is arranged above a ground surface 2 with a recess 3 in the manner of a suspended substrate line. The massive ground surface 2 is connected to a circumferential ground liner 7 formed on the back of the substrate 1 . The recess 3 is closed at the end.

On the front of the substrate 1 , two strip conductors 8 and 9 are applied in parallel in a small distance in printed circuit technology, the slot s between the strip conductors 8 and 9 is selected so that the two strip conductors are coupled to one another in a coplanar manner. The width and length of the strip conductors 8 and 9 are dimensioned according to the known dimensioning guidelines of a coplanarly coupled triplate line in a suspended substrate structure. The ends of the two strip lines 8 and 9 are connected either to coaxial lines, microstrip lines or corresponding coplanar lines, as is indicated schematically by the connections 11 .

On the back of the substrate 1 opposite the coupling slot s, a coupling strip conductor 10 of width B and length L is likewise arranged in printed circuit technology in the air space of the recess 3 , by means of which the two strip conductors 8 and 9 are very firmly coupled to one another. The coupling strip conductor 10 is either idling and ends freely at both ends, or it is connected to ground (short-circuited).

In some applications, the length L of the coupling strip conductor 10 can also be selected to be somewhat shorter than the length of the strip conductors 8 and 9 , it is also conceivable that the strip conductor 10 is not continuous and continuous, but is divided into individual sections, as is the case here Fig. 2 shows. In the example shown, the coupling strip conductor 10 has a width B1 along its length L1, then changes to a width B2 along the length L2, is then interrupted and finally continues along a length Ln with a width Bn. In this way, special coupling properties can be set.

Claims (1)

Directional coupler next to each other on, characterized by two spaced parallel one side of a substrate (1) disposed coplanar striplines (8, 9) disposed above a ground surface (3) that, on the strip conductors (8, 9) opposite On the side of the substrate ( 1 ) opposite the coupling slot (s), a coupling strip conductor ( 10 ) is arranged, the width (B) and length (L) of which is selected in accordance with the desired fixed coupling.