Method and apparatus for beamforming of multi-input-multi-output (MIMO) orthogonal frequency division multiplexing (OFDM) transceivers
AssigneeRalink Technology Corporation
InventorsChien-Cheng Tung, Thomas Edward Pare, Jr.
Life of this patent
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Abstract
An embodiment of the present invention includes a calibration system employed in a multi-input-multi-output (MIMO) system for beamforming and receiving a plurality of streams. The system includes a first calibration circuit responsive to inphase (I) and quadrature (Q) pairs of stream and operative to calibrate each I and Q pair and a second calibration circuit responsive to the calibrated I and Q pairs for all streams, wherein the first and second calibration circuits perform calibration in the time domain.
Claims21
A calibration system employed in a multi-input-multi-output (MIMO) system for receiving a plurality of streams comprising:
- a first calibration circuit responsive to inphase (I) and quadrature (Q) pairs of streams and operative to calibrate each of the I and Q pairs, the first calibration circuit is operative to calibrate and compensate for gain offsets, phase offsets, and group delays on a per stream basis by using reference signals, wherein the first calibration circuit is configured to calculate a gain offset between the I and Q of each of the I and Q pairs of a stream of the streams, over ‘n’ number of samples of I and Q wherein ‘n’ is an integer, and to compensate for the calculated gain offset and to generate a gain compensated I and a gain compensated Q for each of the I and Q pairs of the stream and is further operative to use the gain compensated I and gain compensated Q to calculate a phase offset between the I and Q of each of the I and Q pairs of the stream and to compensate for the calculated phase offset and to calculate and compensate for a group delay and to generate first calibrated I and Q pairs of streams;
- a second calibration circuit responsive to the first calibrated I and Q pairs of streams and operative to calibrate across the streams, the second calibration circuit operative to use the first calibrated I and Q pairs of streams to calculate and compensate for phase delay of I and Q pairs of streams across the streams to generate phase compensated I and Q pairs of streams and to compensate the phase compensated I and Q pairs of streams for a second group delay across the streams.
A calibration system employed in a multi-input-multi-output (MIMO) system for transmitting and receiving a plurality of streams comprising:
- a first calibration circuit responsive to inphase (I) and quadrature (Q) pairs of streams and operative to calibrate each of the I and Q pairs by calculating and compensating for a gain offset, a phase offset, and group delay for each of the I and Q pairs of the streams;
- and
- a second calibration circuit responsive to the calibrated I and Q pairs of streams by calculating and compensating for phase delay and a second group delay across streams,
- wherein the first calibration circuit includes N IQ gain correction blocks, ‘N’ being an integer, for calculating and compensating for the gain offset, each of the N IQ gain correction blocks is operative to receive I and Q pairs of a stream of the streams and to correct the gain offset,
- wherein the first calibration circuit further includes N IQ phase correction blocks, each coupled to a corresponding one of the N IQ gain correction blocks and operative to compensate for the calculated phase offset so that each pair of the I and Q pairs is substantially orthogonal,
- wherein the N IQ phase correction blocks are operative to calculate the phase offset between each of the I and Q pairs by averaging the cross-product between received I and Q signals, of a suitable broadband reference signal.
- wherein the second calibration circuit further includes N delay adjustment blocks coupled to the N IQ phase correction blocks and operative to generate N calibrated receiver baseband signals.
Dependencies are inferred from the claim text.