Abstract
Linear FMCW radar suffers from impairments in range and range rate if there are errors in the modulation rate or phase discontinuities. Often, this is a result of a nonlinearity of the voltage-controlled oscillator that is in the source of the transmit and receive local oscillator. The nonlinearity can be corrected at the source by using a nonlinear control voltage or by processing the received beat frequency. Any signal processing using the later method leads to computation time and energy costs, which can be considerable in some applications. When the range migration algorithm using the Stolt Transform is used for Synthetic Aperture Radar (SAR) image processing, the autofocus linearization technique described here costs nothing in additional hardware or computation time.
Highlights
Transform is used for Synthetic Aperture Radar (SAR) image processing, the autofocus linearization technique described here costs nothing in additional hardware or computation time
SAR data data taken taken with with aa low-cost low-cost radar radar. This and and platform platform constructed constructed by the the authors authors in in the the same same way way as as the the previously previously published published coffee-can coffee-can radar radar [23]
(VCO) was was purposefully purposefully driven of 1.1 well outside its linear radarThe wasradar mounted driven over overa bandwidth a bandwidth of GHz, 1.1 GHz, well outside its region
Summary
Much has been written about FMCW radar, especially using linear modulation [1,2,3,4]. The phase of the received signal from a single point scatterer at a delay θr, is θ t ( t ) = π m o ( t + τ )2 + ω o ( t + τ ) + φ. ItItisisalso the modulation, modulation, i.e., i.e.,replacing replacingmm m(t), o with alsoknown known that that nonlinearity nonlinearity in in the m(t), reo with results in a baseband frequency that is not constant over the modulation ramp. Solutions have been proposed and proven to compensate or correct for nonlineariThese solutions require additional hardware such as a delay line [5,6], a Phase-Locked ties. Some methods require additional digital signal processing of the Intermediate Frequency (IF) [12,13,14].
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