Time delay estimation with receivers of approximately known phase difference characteristics

The problem of measuring the time delay (or difference in arrival times) of a signal emanating from a source and received at two separate locations is considered. Most existing techniques of time delay estimation assume identical receivers. The phase of the cross-spectrum between the receivers´ outputs is then directly proportional to frequency, with the time delay as the proportionality constant. The paper develops a new estimator for receivers having unequal phase characteristics. Their phase differences are represented by a polynomial in frequency, with the coefficients of the polynomial approximately known. An augmented least-squares estimator, incorporating the approximate phase information, is developed to compute the time delay. Simulation results that serve to illustrate the method and confirm some of the theoretical findings are presented.