Simulation Study of Altitude and Angle Estimation with an InSAR Altimeter

Abstract

We present a simulation study of an algorithm for the range and angle of arrival(AOA) estimation with an interferometric synthetic aperture radar(InSAR) altimeter using a real digital elevation model(DEM). We also illustrate a step-by-step procedure of generating raw InSAR data, as well as their range and azimuth compressed data, which is to be used for the subsequent altitude and angle estimation. The AOA is estimated using a deterministic maximum likelihood estimator(DMLE) applied to the first arrived point for each pulse in the compressed data obtained with three antennas. The range bin size and the pulse repetition interval(PRI) are much smaller than the cell size of the DEM used in this study. To make the DEM compatible to the radar parameters, we first generate a higher resolution DEM by linearly interpolating the given DEM. After a brief description of the principle of the InSAR altimeter, the algorithms for altitude and angle estimation are presented, and their performance is assessed through simulation.

Altimetry Method for an Interferometric Radar Altimeter Based on a Phase Quality Evaluation

“…The target range (R k ) detected at each observation point (t a k ) in Figure 5 can be expressed as Equation (10) [23], where R 0 is the closest range in Figure 5 and ∆R k is the RCM component that forms the range curve indicated by the red line in Figure 5.…”

“…The range (=time t e ) axis of the received signal was transformed into the frequency domain, and the center of the sinc function is k e 2R k c . Given that R k varies at every point (t a k ) in Equation (10), ∆R k is added to the closest range (R 0 ) at every point (t a k ) in Equation (12). Consequently, in this paper, we calculate ∆R k for each observation point (t a k ) and move the range cell by an amount equal to the calculated value, as shown in Figure 6.…”

“…To minimize these errors, researchers have investigated radar altimeters for aircraft to measure not only the range of the target but also the angle of the target [10][11][12][13][14]. Among these altimeters, an interferometric radar altimeter (IRA) [10][11][12] estimates the target angle using the phase comparison monopulse (PCM) technique [15,16] with monopulse radar [17,18].…”

“…To minimize these errors, researchers have investigated radar altimeters for aircraft to measure not only the range of the target but also the angle of the target [10][11][12][13][14]. Among these altimeters, an interferometric radar altimeter (IRA) [10][11][12] estimates the target angle using the phase comparison monopulse (PCM) technique [15,16] with monopulse radar [17,18]. Unlike conventional radar altimeters that provide only one-dimensional range information, an IRA can provide three-dimensional information (range/elevation/azimuth) about the target and reduce altitude errors.…”