Kapriel V. Krikorian

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.

Application of a joint tracking and identification method to dismount targets

This paper presents a method for tracking dismounts/humans in a potentially dense clutter background. The proposed approach uses Multiple Hypothesis Tracking (MHT) for data association and Interacting Multiple Model (IMM) filtering. The problem is made difficult by the presence of random and persistent clutter, such as produced by moving tree branches. There may also be moving targets (such as vehicles and animals) that are not of interest to the user of the tracking system, but that must be tracked in order to separate these targets from the targets of interest. Thus, a joint tracking and identification method has been developed to utilize the features that are associated with dismount targets. This method uses a Dempster-Shafer (D-S) approach to combine feature data to determine the target type (dismount versus other). Feature matching is also included in the computation of the track score used for MHT data association. The paper begins by giving an overview of the features that have been proposed in the literature for distinguishing humans from other types of targets. These features include radar cross section, target dynamics, and spectral and gait characteristics. For example, the number of secondary peaks around the main peak corresponding to the mean Doppler shift is one feature that is sent to the tracker. A large number of secondary peaks will be an indication that the observation is from an animal, rather than a vehicle. Also, if spectral analysis of the variation in Doppler shift due to torso motion yields a distinct periodic pattern with a peak at about 2 Hz, this can be used to identify the target as a human and, along with the target speed, may even be used as a target signature. The manner in which these features are estimated during signal processing and how this data is included in the track score is described. A test program conducted to produce data for analysis and development is described. Typical results derived from real data, collected during this test program, are presented to show how feature data is used to enhance the tracking solution. These results show that the proposed methods are effective in separating the tracks on dismounts from those formed on clutter and other objects.