Abstract: Device and method for permanently checking the integrity of a transmission affected by parameters not directly accessible to measurement and whose influence on the modulus and phase of the field radiated in space can be determined by utilizing a mathematic model, the transmission being from an antenna array. Each antenna is supplied with one or more Hf carrier frequencies, each being modulated in a known way by one or more sinusoidal low frequency signals. First, a recording is made, at least at one point and during a time period T, of the amplitude of the combination of the signal received at this point and of a reference signal, having a fundamental frequency equal to one of the HF frequencies of the signal to be analyzed. Then, the amplitude of low frequency components of the signal thus obtained is extracted and memorized.