The present invention relates to a device for high-frequency technology, or for the microwave region and millimeter wave region of the electromagnetic spectrum, characterized in that it contains a liquid-crystal medium which consists of one or more compounds, which one or more compounds, which contain 6 to 15 five-, six- or seven-membered rings, preferably 1,4-linked phenylene rings, or in that it contains a liquid-crystal medium which itself comprises a component A, which itself consists of one or more of the said compounds, which one or more compounds, which contain 6 to 15 five-, six- or seven-membered rings, preferably 1,4-linked phenylene rings. The present invention additionally relates to compounds of the formula (I), in which the parameters have the meanings given in the text, and to the corresponding, novel liquid-crystal media, to the use and preparation thereof, and to the production and use of the devices. The devices according to the invention are particularly suitable phase shifters in the microwave and millimeter wave region, for microwave and millimeter wave array antennas and very particularly for so-called tunable “reflectarrays”.