Abstract: The invention relates to the detection of liquid in a cavity of a structure, e.g. a sandwich-structure cell with honeycomb core and carbon fiber composite coating. The structure is subjected to a mechanical vibration, at a frequency fm in the audible range, by an excitation wave, the area being explored is subjected to an incident electromagnetic wave and the reflected electromagnetic wave is analyzed to deduce therefrom the presence or the absence of liquid in cavities. The Faraday wave induced on the surface of the liquid in the cavity comprises subharmonic frequencies of fm which modulate the reflected electromagnetic wave and make it possible to identify the presence of liquid. A detection apparatus comprises an excitation wave generation device for generating the vibration excitation wave, an electromagnetic wave generation device for generating the incident electromagnetic wave, a measuring device for detecting and measuring the reflected electromagnetic wave, and a signal processor.

Abstract: The invention relates to the detection of liquid in a cavity of a structure, e.g. a sandwich-structure cell with honeycomb core and carbon fiber composite coating. The structure is subjected to a mechanical vibration, at a frequency fm in the audible range, by an excitation wave, the area being explored is subjected to an incident electromagnetic wave and the reflected electromagnetic wave is analyzed to deduce therefrom the presence or the absence of liquid in cavities. The Faraday wave induced on the surface of the liquid in the cavity comprises subharmonic frequencies of fm which modulate the reflected electromagnetic wave and make it possible to identify the presence of liquid. A detection apparatus comprises an excitation wave generation device for generating the vibration excitation wave, an electromagnetic wave generation device for generating the incident electromagnetic wave, a measuring device for detecting and measuring the reflected electromagnetic wave, and a signal processor.

Abstract: The invention relates to a radioaltimeter type detector comprising an oscillator-transmitter (10), a modulator (20) suitable for frequency modulating the oscillator-transmitter according to a given characteristic, a mixer receiving the signal from the oscillator-transmitter and a corresponding echo signal reflected by a target, and a discriminator circuit (50, 60) connected to the output from the mixer. According to the invention, the modulator (20) includes a digital memory (21) containing a series of values defining the frequency modulation characteristic of the oscillator-transmitter (10).