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A system and method for imaging objects obscured by a covering layer of snow. The system preferably utilizes a continuous-wave radar generating short-wavelength radio-frequency (RF) signal beam-scanned over angular displacements following a scanning pattern toward a target area. Reflections of the:R

A system and method for imaging objects obscured by a covering layer of snow. The system preferably utilizes a continuous-wave radar generating short-wavelength radio-frequency (RF) signal beam-scanned over angular displacements following a scanning pattern toward a target area. Reflections of the:RF signal from objects buried beneath the snow are registered by an array of RF detectors whose signal magnitudes are summed arid correlated with scan direction to generate a signal providing spatial object information, Which by way of example, is visually displayed. The radio-frequency beam may be scanned over the scene electronically or by either mechanically or electromechanically modulating antenna direction or the orientation of a beam deflector. The system is capable of generating multiple image frames per second, high-resolution imaging, registration of objects to a depth exceeding two meters, and can be implemented at low cost without complex signal processing hardware.

대표청구항 ▼

A system and method for imaging objects obscured by a covering layer of snow. The system preferably utilizes a continuous-wave radar generating short-wavelength radio-frequency (RF) signal beam-scanned over angular displacements following a scanning pattern toward a target area. Reflections of the:R

A system and method for imaging objects obscured by a covering layer of snow. The system preferably utilizes a continuous-wave radar generating short-wavelength radio-frequency (RF) signal beam-scanned over angular displacements following a scanning pattern toward a target area. Reflections of the:RF signal from objects buried beneath the snow are registered by an array of RF detectors whose signal magnitudes are summed arid correlated with scan direction to generate a signal providing spatial object information, Which by way of example, is visually displayed. The radio-frequency beam may be scanned over the scene electronically or by either mechanically or electromechanically modulating antenna direction or the orientation of a beam deflector. The system is capable of generating multiple image frames per second, high-resolution imaging, registration of objects to a depth exceeding two meters, and can be implemented at low cost without complex signal processing hardware. said first recorded count value to provide said first corrected count value attempts to provide a piece-wise linear mapping between possible values of said analog input and possible values of said first corrected count value. 3. The machine of claim 1 in which said first piece-wise non-linear analog reference waveform is a sinusoid, whereby well-developed prior art means for generating sinusoids can supply said first piece-wise non-linear analog reference waveform. 4. The machine of claim 3 further including means for using said sinusoid to modulate or to demodulate a signal which is a communications signal or an imaging system signal, whereby said sinusoid can be used both for frequency shifting of said signal and for A/D conversion of said signal. 5. The machine of claim 3 further including means for generating said sinusoid. 6. The machine of claim 5 in which said means for generating said sinusoid includes a voltage-controlled oscillator, whereby the frequency of said sinusoid can be precisely controlled. 7. The machine of claim 5 in which said means for generating said sinusoid further includes a phase-locked loop, whereby the frequency and the phase of said sinusoid can be precisely controlled. 8. The machine of claim 1 further including means for estimating parameters of said first piece-wise non-linear analog reference waveform or of said first piece-wise non-linear waveform segment, whereby said information can be derived and used even if said parameters are initially unknown or time-varying. 9. The machine of claim 8 in which said means for estimating said parameters includes means for measuring of a first reference count value corresponding to a first known analog input. 10. The machine of claim 9 in which said means for estimating said parameters further includes: a. means for measuring a second reference count value corresponding to a second known analog input b. means for digitally processing said first reference count value to provide a first corrected reference count value which is in accordance with a first linear mapping between analog input values and corrected digital count values c. means for digitally processing said second reference count value to provide a second corrected reference count value which is in accordance with said first linear mapping d. means for combining said first corrected reference count value and said second corrected reference count value whereby said first known analog input and said second known analog input can have different values and the same input configurations, or the same value but different input configurations, or different values and different input configurations, and can be used in estimating said parameters. 11. The machine of claim 1 further including means for correcting the effects of reference waveform level offset and comparator input offset voltage. 12. The machine of claim 11 in which said first corrected count value is in accordance with a linear mapping between analog input values and corrected digital count values and in which said means for correcting the effects of reference waveform level offset and comparator input offset voltage comprises: a. means for measuring of a first reference time count corresponding to a first known analog input, said means for measuring of said first reference time count employing said means for comparing which produced said first comparison result with the same input configuration b. means for digitally processing said first reference time value to provide a first corrected reference count value which is in accordance with said first linear mapping c. means for subtracting said first corrected reference count value from said first corrected count value to produce a first difference term whereby with the same input configuration, said first corrected count value and said first corrected reference count value include the same error due to waveform level offset and comparator input offset voltage, so that this error is largely absent in said first difference term. 13. The machine of claim 1 further including means for correcting the effects of reference waveform level offset and comparator input offset voltage and also for correcting the effects of unknown or poorly-estimated gain. 14. The machine of claim 13 in which said first corrected count value is in accordance with a linear mapping between analog input values and corrected digital count values and in which said means for correcting the effects of reference waveform level offset and comparator input offset voltage and also for correcting the effects of unknown or poorly-estimated gain comprises: a. means for measuring of a first reference time count corresponding to a first known analog input, in which said means for measuring of said first reference time count employs said means for comparing which produced said first comparison result, with the same input configuration b. means for measuring of a second reference time count corresponding to a second known analog input, in which: i. said second known analog input does not have the same value as first known analog input ii. said means for measuring of said second reference time count employing said means for comparing which produced said first comparison result, with the same input configuration c. means for digitally processing said first reference time value to provide a first corrected reference count value which is in accordance with said first linear mapping d. means for digitally processing said second reference time value to provide a second corrected reference count value which is in accordance with said first linear mapping e. means for subtracting said first corrected reference count value from said first corrected count value to produce a first difference term f. means for subtracting said first corrected reference count value from said second corrected reference count value to produce a second difference term g. means for computing a first normalized corrected count value substantially equal to the product of said first difference term and a scaling factor divided by said second difference term whereby with the same input configuration, said first corrected count value, said first corrected reference count value, and said second corrected reference count value include the same error due to waveform level offset and comparator input offset voltage and the same scale error, and whereby said first normalized corrected count value substantially eliminates these errors and provides a desired scale. 15. The machine of claim 13 in which said first corrected count value is in accordance with a linear mapping between analog input values and corrected digital count values and in which said means for correcting the effects of reference waveform level offset and comparator input offset voltage comprises and also for correcting the effects of unknown or poorly-estimated gain comprises: a. means for measuring of a first reference time count corresponding to a first known analog input, in which said means for measuring of said first reference time count employs said means for comparing which produced said first comparison result, with the same input configuration b. means for measuring of a second reference time count corresponding to a second known analog input, in which said means for measuring of said second reference time count employs means for comparing other than said means for comparing which produced said first comparison result, with a first input configuration c. means for measuring of a third reference time count corresponding to a third known analog input, in which: i. said third known analog input does not have the same value as second known analog input ii. said means for measuring of said third reference time count employing said means for comparing which resulted in said second reference time count, with the same input configuration, namely, said first input configuration d. means for di