A method for simultaneous transmission of at least two high-frequency transmission signals via a common high-frequency line includes providing at least two input signals at respective inlet ports. The input signals are signals of a same carrier frequency. From the input signals, respective transmission signals are provided with different transmission frequencies from each other and from the carrier frequency by mixing the input signals using one frequency mixer each. The frequency mixers are supplied with respective mixer oscillator signals. The transmission signals are transmitted via the common high-frequency line. The mixer oscillator signals are provided from a same oscillator signal.