Techniques for correcting for phase and amplitude offsets in a MIMO radio device
First Claim
1. A radio device comprising:
- a. a plurality of transmitters that upconvert corresponding ones of a plurality of baseband transmit signals for simultaneous transmission via corresponding ones of a plurality of antennas;
b. a plurality of receivers that downconvert a plurality of radio signals detected by corresponding ones of the plurality of antennas to produce a corresponding plurality of baseband receive signals; and
c. a processor coupled to the plurality of transmitters and the plurality of receivers, wherein the processor measures differences in phase responses among the plurality of transmitters and plurality of receivers by measuring a first phase difference between an input to a transmitter associated with a first antenna and an output of a receiver associated with antenna i, and a second phase difference between an input to a transmitter associated with antenna i and an output of a receiver associated with the first antenna, for i=2 to N, where N is the number of antennas, and the processor processes the plurality of baseband transmit signals and/or the plurality of baseband receive signals with corresponding correction values that correct for differences in broadband phase responses among the plurality of transmitters and plurality of receivers.
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Accused Products
Abstract
Techniques to correct for phase and amplitude mismatches in a radio device in order to maintain channel symmetry when communicating with another device using MIMO radio communication techniques. Correction for the amplitude and phase mismatches among the plurality of transmitters and plurality of receivers of a device may be made at baseband using digital logic (such as in the modem) in the receiver path, the transmitter path or both paths of that device. In a device, amplitude and phase offsets are determined among the plurality of radio transmitter and radio receiver paths by measuring phase and amplitude responses when supplying a signal to a transmitter in a first antenna path of the device and coupling the radio signal from a first antenna to a second antenna path of that device where the signal is downconverted by a receiver associated with the second antenna path, and similarly coupling a signal from the second antenna path to the first antenna path. Measurements are obtained between the first antenna path and each of the other antenna paths when coupling a signal in both directions between them. Phase and amplitude offset correction values are computed from the phase and amplitude measurements during a self-calibration operation or mode of the device, and are used during a run-time operation or mode when processing the baseband transmit and/or receive signals to compensate for the phase and amplitude offsets among the plurality of transceiver paths of a device. Amplitude offset correction may not be necessary (or optional) for certain radio implementations or MIMO radio algorithms. The device may execute the self-calibration mode on device power-up, and then periodically thereafter. Self-calibration may also be performed at the factory on a device.
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Citations
57 Claims
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1. A radio device comprising:
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a. a plurality of transmitters that upconvert corresponding ones of a plurality of baseband transmit signals for simultaneous transmission via corresponding ones of a plurality of antennas;
b. a plurality of receivers that downconvert a plurality of radio signals detected by corresponding ones of the plurality of antennas to produce a corresponding plurality of baseband receive signals; and
c. a processor coupled to the plurality of transmitters and the plurality of receivers, wherein the processor measures differences in phase responses among the plurality of transmitters and plurality of receivers by measuring a first phase difference between an input to a transmitter associated with a first antenna and an output of a receiver associated with antenna i, and a second phase difference between an input to a transmitter associated with antenna i and an output of a receiver associated with the first antenna, for i=2 to N, where N is the number of antennas, and the processor processes the plurality of baseband transmit signals and/or the plurality of baseband receive signals with corresponding correction values that correct for differences in broadband phase responses among the plurality of transmitters and plurality of receivers. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
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26. A radio device comprising:
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a. a plurality of transmitters that upconvert corresponding ones of a plurality of baseband transmit signals for simultaneous transmission via corresponding ones of a plurality of antennas;
b. a plurality of receivers that downconvert a plurality of radio signals detected by corresponding ones of the plurality of antennas to produce a corresponding plurality of baseband receive signals; and
c. a processor coupled to the plurality of transmitters and the plurality of receivers that measures phase offsets at a plurality of sub-carriers k associated with a multi-carrier baseband modulation process used for the plurality of baseband transmit signals and the plurality of baseband receive signals, by measuring at each sub-carrier k a first phase difference when a multi-carrier baseband signal is applied at an input to the transmitter associated with the first antenna and coupled as receive input to the receiver associated with antenna i via an over-the-air link or a cable connection, and measuring at each sub-carrier k a second phase difference when a multi-carrier signal is applied at an input to the transmitter associated with antenna i and coupled as a receive input to receiver associated with the first antenna via an over-the-air link or a cable connection, for i=2 to N, where N is the number of antennas, and wherein the processor processes the plurality of baseband transmit signals and/or the plurality of baseband receive signals with correction values that correct for the phase offsets measured at each of the plurality of sub-carriers k. - View Dependent Claims (27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37)
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38. 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:
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a. measuring phase responses of the plurality of transmitters and the plurality of receivers, comprising measuring a first phase difference between an input to a transmitter associated with a first antenna and an output of a receiver associated with antenna i, and a second phase difference between an input to a transmitter associated with antenna i and an output of a receiver associated with the first antenna, for i=2 to N, where N is the number of antennas; and
b. computing a plurality of correction values from the phase differences to correct for differences in broadband phase responses of the plurality of transmitters and the plurality receivers. - View Dependent Claims (39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57)
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Specification