Inverse Precision Velocity Update for Monopulse Calibration

A critical function of a radar system is to precisely locate moving targets for identification and targeting. The moving target location is determined with respect to the actual boresight of the radar antenna performing the angle measurements. The accuracy of these angle measurements is often limited by bias errors (e.g., radome errors, sum and difference channel isolation and imbalances, and harmonization errors) which are not related to the signal-to-noise ratio of the received radar return. In effect, the bias errors preclude accurate monopulse angle measurement to a target, even if the target is clearly visible by the radar. A new technique is proposed which avoids these limitations, deriving a correction for the electrical boresight of a monopulse antenna mounted on a moving platform. It exploits highly accurate velocity measurements from currently available low-cost INS/GPS systems with carrier phase measurements. The measured velocity coupled with advanced multichannel processing of a monopulse SAR mode provide independent pointing error estimates from many pixels. This patented technique has been named Inverse Precision Velocity Update (or Inverse PVTJ) for monopulse calibration. The angle estimates from a selected set of pixels are weighted and averaged to obtain a precise estimate of the monopulse beam pointing for accurate moving target geolocation.