Empirical Calibration Coefficient Estimation in the Context of Multi-Functional RF Systems

This paper presents an empirical approach to estimate the transfer function required for the calibration in general of a two-channel multi-functional broadband receiver developed at Fraunhofer FHR. Modern broadband receivers may enable increased functionality, provided they maintain adequate performance. For example, some modern active electronically scanned arrays (AESAs) and, increasingly, future systems may incorporate simultaneous operating modes, particularly multiple different radar modes together with communications and spectrum sensing modes. It is clear, therefore, that broadband hardware calibration is an essential feature for the realization of Multi-Functional RF Systems (MFRFS). In this paper the characteristics of the MFRF receiver are described via its transfer function. Under laboratory conditions, the receiver transfer function may be determined classically using a vector network analyzer. However, for in-theatre applications, on-site calibration will be necessary. A defined input signal is fed into the broadband receiver via an external signal source and the output signal is recorded. The receiver transfer function is then determined by comparing the input and output signals. A coherent signal processing approach using empirical transfer function estimation and a corresponding measurement concept will be presented resulting in reduced measurement and computational effort compared to state-of-the-art. The performance of the proposed approach is evaluated using real measurement data from a laboratory setup.