A signal processing device for processing a signal of a reflected wave which is a wave reflected in a medium and is received by a receiver, when a wave propagating through the medium is continuously transmitted by a transmitter. The signal processing device includes: an estimation unit configured to estimate a lower limit distance of a detection distance range for which an intensity level of a scattered wave from the medium in the detection distance range is equal to or smaller than an allowable level; and a scattering reduction unit configured to remove, from a signal of the reflected wave received, a signal of the scattered wave from the medium in a masking region from the receiver to the lower limit distance to perform output.

A signal processing device for processing a signal of a reflected wave which is a wave reflected in a medium and is received by a receiver, when a wave propagating through the medium is continuously transmitted by a transmitter. The signal processing device includes: an estimation unit configured to estimate a lower limit distance of a detection distance range for which an intensity level of a scattered wave from the medium in the detection distance range is equal to or smaller than an allowable level; and a scattering reduction unit configured to remove, from a signal of the reflected wave received, a signal of the scattered wave from the medium in a masking region from the receiver to the lower limit distance to perform output.

To acquire a beat frequency necessary for target extraction, target speed estimation, and Doppler influence detection by preventing the necessary beat frequency from overlapping unnecessary frequencies in a heterodyne processing result, an apparatus includes a wave receiver that receives a reflected wave of a chirp wave reflected from a target, and outputs a reception wave signal, a dual-sweep signal generator that generates a dual-sweep signal of the chirp wave, having a frequency which does not overlap that of the chirp wave, and a heterodyne processor that generates a beat frequency by multiplying the reception wave signal and the dual-sweep signal as a heterodyne signal.

To acquire a beat frequency necessary for target extraction, target speed estimation, and Doppler influence detection by preventing the necessary beat frequency from overlapping unnecessary frequencies in a heterodyne processing result, an apparatus includes a wave receiver that receives a reflected wave of a chirp wave reflected from a target, and outputs a reception wave signal, a dual-sweep signal generator that generates a dual-sweep signal of the chirp wave, having a frequency which does not overlap that of the chirp wave, and a heterodyne processor that generates a beat frequency by multiplying the reception wave signal and the dual-sweep signal as a heterodyne signal.

A system for searching for underground entities in ground of an area, including a search probe configured to generate and deliver an acoustic signal into the ground of the area, wherein the acoustic signal uses a low frequency signal so that wavelengths of the acoustic signal are between 0.01-500 times the depth to the sought underground entity, two or more sensors positioned on the ground at about an equal distance from the search probe at different angles, an analysis device that receives measurements from the two or more sensors in the form of a measured echo signal responsive to the delivered acoustic signal, wherein said analysis device designates pairs of sensors and subtracts their echo signals to identify a difference indicating the existence of an underground entity.

Methods and systems for estimating a distance between an acoustic sensor and an acoustic reflector in a conduit are disclosed. One such method includes using the acoustic sensor to measure a combined acoustic signal that comprises an originating acoustic signal propagating along the conduit and an echo signal. The echo signal is generated by the originating acoustic signal reflecting off the acoustic reflector after propagating past the acoustic sensor. A frequency domain representation of the combined acoustic signal is determined and the echo signal is identified by identifying in the frequency domain representation periodic oscillations having a peak-to-peak difference between 0.75 Hz and 1500 Hz. The distance between the acoustic sensor and the acoustic reflector is determined from the velocity of the echo signal and a time required for the echo signal to propagate between the acoustic sensor and the acoustic reflector.

Methods and systems for estimating a distance between an acoustic sensor and an acoustic reflector in a conduit are disclosed. One such method includes using the acoustic sensor to measure a combined acoustic signal that comprises an originating acoustic signal propagating along the conduit and an echo signal. The echo signal is generated by the originating acoustic signal reflecting off the acoustic reflector after propagating past the acoustic sensor. A frequency domain representation of the combined acoustic signal is determined and the echo signal is identified by identifying in the frequency domain representation periodic oscillations having a peak-to-peak difference between 0.75 Hz and 1500 Hz. The distance between the acoustic sensor and the acoustic reflector is determined from the velocity of the echo signal and a time required for the echo signal to propagate between the acoustic sensor and the acoustic reflector.

A method for constructing a frequency profile of an emitted signal suitable for use in a non-contact ranging system with multi-scale spectral analysis includes determining N stepped frequency chirps, wherein each frequency chirp of the N stepped frequency chirps has a linear FM modulation of predetermined bandwidth and slope, and wherein a starting frequency for each of the plurality of stepped frequency chirps is chosen so that a non-linear step profile is created which extends over a predetermined total bandwidth, sorting the plurality of N stepped frequency chirps into P sub-sequences, where P is equal to the product of decimation factors to be used in the multi-scale spectral analysis, and ordering the P sub-sequences end to end in time.

A method for constructing a frequency profile of an emitted signal suitable for use in a non-contact ranging system with multi-scale spectral analysis includes determining N stepped frequency chirps, wherein each frequency chirp of the N stepped frequency chirps has a linear FM modulation of predetermined bandwidth and slope, and wherein a starting frequency for each of the plurality of stepped frequency chirps is chosen so that a non-linear step profile is created which extends over a predetermined total bandwidth, sorting the plurality of N stepped frequency chirps into P sub-sequences, where P is equal to the product of decimation factors to be used in the multi-scale spectral analysis, and ordering the P sub-sequences end to end in time.

A method for measuring, using a radar or sonar, the velocity with respect to the ground of a carrier moving parallel to the ground, includes the following steps: a) orienting the line of sight of the radar or sonar toward the ground; b) emitting a plurality of radar or sonar signals (P.sub.1-P.sub.N) that are directed toward the ground, and acquiring respective echo signals (E.sub.1-E.sub.N); c) processing the acquired echo signals so as to obtain, for one or more echo delay values, a corresponding Doppler spectrum; d) for the or at least one the echo delay value, determining a high cut-off frequency of the corresponding Doppler spectrum; and e) computing the velocity of the carrier with respect to the ground on the basis of the one or more high cut-off frequencies. A system allowing such a method to be implemented.