Patent ID: 7236750

Claim:
A method for calibrating a radio device that comprises a plurality of antennas, a corresponding plurality of receivers and a corresponding plurality of transmitters, the method comprising steps of: a. supplying a reference signal to an input of a receiver circuit associated with a first antenna path to enable the receive circuit to process the reference signal and produce a first baseband signal that is converted to a first digital signal by an analog-to-digital converter associated with the first antenna path; b. coupling the first digital signal to a digital-to-analog converter associated with a transmitter circuit of a second antenna path, wherein the transmitter circuit associated with the second antenna path outputs an analog signal; c. measuring the phase difference between the reference signal supplied to the input of the receiver circuit associated with the first antenna path and the analog signal output by the transmitter circuit associated with the second antenna path to produce a first phase difference; d. supplying a reference signal to an input of a receiver circuit associated with the second antenna path to enable the receiver circuit to process the reference signal and produce a second baseband signal that is converted to a second digital signal by an analog-to-digital converter associated with the second antenna path; e. coupling the second digital signal to a digital-to-analog converter associated with a transmitter circuit of the first antenna path, wherein the transmitter circuit associated with the first antenna path outputs an analog signal; f. measuring the phase difference between the reference signal supplied to the input of the receiver circuit associated with the second antenna path and the analog signal output by the transmitter circuit associated with the first antenna path to produce a second phase difference; and g. computing a phase mismatch value from the first phase difference and the second phase difference, whereby the phase mismatch value represents the phase mismatch between the first antenna path and the second antenna path and is used when processing baseband signals that are transmitted and/or received via the plurality of antenna paths.