Vectorial network analyser comprising - an input measuring device having: - a terahertz transmitter for applying a terahertz signal to an input of a measurement object; - a terahertz receiver for receiving a terahertz signal emitted via the input of the measurement object; - a terahertz reference receiver for receiving part of the terahertz signal generated by the terahertz transmitter; - an output measuring device having: - a terahertz transmitter for applying a terahertz signal to an output of the measurement object; - a terahertz receiver for receiving a terahertz signal emitted via the output of the measurement object; - a terahertz reference receiver for receiving part of the terahertz signal generated by the terahertz transmitter; - a beat source for generating an optical beat signal; - an optical transfer device, which divides the optical beat signal into at least a first and a second partial signal (TS1, TS2), wherein the transfer device guides the first partial signal to at least one of the terahertz transmitters (11, 21) and the second partial signal to at least one of the terahertz receivers (12, 22) and/or at least one of the terahertz reference receivers (13, 23); and - a phase changing unit for varying the phase of the first and/or the second partial signal (TS1, TS2) of the optical beat signal. - an input measuring device having: - a terahertz transmitter for applying a terahertz signal to an input of a measurement object; - a terahertz receiver for receiving a terahertz signal emitted via the input of the measurement object; - a terahertz reference receiver for receiving part of the terahertz signal generated by the terahertz transmitter; - a terahertz transmitter for applying a terahertz signal to an input of a measurement object; - a terahertz receiver for receiving a terahertz signal emitted via the input of the measurement object; - a terahertz reference receiver for receiving part of the terahertz signal generated by the terahertz transmitter; - an output measuring device having: - a terahertz transmitter for applying a terahertz signal to an output of the measurement object; - a terahertz receiver for receiving a terahertz signal emitted via the output of the measurement object; - a terahertz reference receiver for receiving part of the terahertz signal generated by the terahertz transmitter; - a terahertz transmitter for applying a terahertz signal to an output of the measurement object; - a terahertz receiver for receiving a terahertz signal emitted via the output of the measurement object; - a terahertz reference receiver for receiving part of the terahertz signal generated by the terahertz transmitter; - a beat source for generating an optical beat signal; - an optical transfer device, which divides the optical beat signal into at least a first and a second partial signal (TS1, TS2), wherein the transfer device guides the first partial signal to at least one of the terahertz transmitters (11, 21) and the second partial signal to at least one of the terahertz receivers (12, 22) and/or at least one of the terahertz reference receivers (13, 23); and - a phase changing unit for varying the phase of the first and/or the second partial signal (TS1, TS2) of the optical beat signal.