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Passive sensor systems are attractive for monitoring due to the absence of probing emissions. Two passive systems: an acoustic camera, manufactured by Brüel & Kjær (Sound and Vibration Measurement A/S) and a microwave radiometer are considered in the paper. The performance of these systems is carefully analyzed. The obtained results show the limitations of the acoustic camera in acoustic noise source localization caused by specific side lobes of a pattern of its microphone array. A suggestion how to avoid them is given. Application of microwave bistatic radiometer provides information about thermal electromagnetic radiation of objects in 3D spatial coordinates. The generated radiometric maps contain amplitude and phase information, which is suitable for estimation of displacements/vibration. The received results are applicable in nondestructive testing.

The work is devoted to fusion of radar and radiometer images. Noise waveform SAR generates radar images of reflective objects of its field of view. A bistatic radiometer with synthetic aperture estimates the thermal radio emissions of the objects along their angular coordinates and even range. The estimated brightness temperatures of rough and smooth surfaces are different, as well as the radar responses from them. Identification of the parameters of objects surfaces may be done using results of joint processing of images generated by both sensors. The optimum and quasi-optimum criteria for fusion of the images were obtained. The latter was experimentally checked. It approves the opportunity to fuse the images for further estimation of some parameters of objects surfaces. The results obtained may be used in environmental and security applications.

The paper is devoted to coherent radiometric imaging systems. The investigated systems may be considered as a version of bistatic noise waveform passive radar with synthetic aperture having external reference. Reference signal in this imaging system is received from the investigated emitting object using auxiliary receiver. Although a number of theoretical studies on aperture synthesis imaging algorithms exist, relatively few of them deal with experimental investigation. In particular, no information concerning range-azimuth coherent radiometric imaging has been found. In this paper, an experimental investigation of possibility to generate coherent radiometric images using two antennas with beam synthesizing is carried out. Indoor radiometric imaging has been validated using absorbers as the emitting objects. These experiments enabled to estimate range resolution of the radiometric system achieved by focusing antennas with beam synthesizing for range span limited by means about bistatic baseline. [ABSTRACT FROM PUBLISHER]