Abstract: A millimeter and/or submillimeter network vector analyzer comprises a millimeter source and a millimeter heterodyne receiver, and the network to be analyzed is placed between the source and the receiver. The millimeter source comprises a first microwave source feeding a millimeter harmonic generator. The millimeter heterodyne receiver comprises a millimeter harmonic mixer which is fed by a second microwave source which serves as a local oscillator for it, an HF (high frequency) vector receiver and a device for displaying the characteristics of the analyzed network. The analyzer includes a device for servocontrolling the frequency of emission of the second microwave source by the frequency of the first microwave source (or conversely), and a main HF (high frequency) oscillator activating this servocontrol device. The main oscillator is also directly used as a phase reference for the HF (high frequency) vector receiver.