A method and apparatus are provided that determine group delay for a set of
transmit or receive chains over a wide frequency band without causing
significant interference with simultaneous users of the system. In one
embodiment, the invention includes an antenna array adapted to transmit
and receive radio communications signals with a plurality of other
terminals, the communications signals each using a particular minimum
bandwidth, a transmit chain to transmit a calibration signal through the
antenna array to a transponder on at least two different frequency bands
within the minimum bandwidth, and a receive chain to receive through the
antenna array a transponder signal from the transponder, the transponder
signal being received on at least two different frequency bands and being
based on the calibration signal. A signal processor determines a frequency
dependent calibration vector based on the at least two frequency bands of
the transponder signal as received through the receive chain.
