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US007450919B1

(12) United States Patent

Chen et al.

(io) Patent No.: (45) Date of Patent:

US 7,450,919 Bl Nov. 11, 2008

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A system and method are provided for compensating for an I/Q mismatch of a receiver in a mobile terminal. In general, the receiver and a transmitter of the mobile terminal are formed on a single substrate. A transmit signal is transmitted via the transmitter. Due to leakage through the substrate, the transmit signal is provided to one or more points in the receiver. One of these points is an input of the amplifier circuitry. A gain of the amplifier circuitry is modulated during reception of the transmit signal such that an amplified signal provided by the amplifier circuitry is offset from the carrier frequency of the transmit signal by a known frequency offset. The amplified signal is downconverted to provide a quadrature output signal. Processing circuitry processes frequency components of the quadrature output signal corresponding to the known frequency offset to determine the I/Q mismatch of the receiver.

20 Claims, 3 Drawing Sheets

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RECEIVE THE TRANSMITTED SIGNAL DUE TO LEAKAGE OF THE TRANSMITTED SIGNAL FROM THE TRANSMITTER INTO THE RECEIVER FRONT END

MODULATE THE GAIN OF THE LNA DURING RECEPTION OF THE TRANSMITTED SIGNAL

SUCH THAT THE OUTPUT OF THE LNA IS OFFSET FROM THE CARRIER FREQUENCY OF THE TRANSMITTED SIGNAL BY A KNOWN FREQUENCY OFFSET (Y)

PROCESS THE OUTPUT OF THE RECEIVER
FRONT END TO DETERMINE FOURIER
COEFFICIENTS (CPR ,CP| ,CMR ,CM|)

FOR THE FREQUENCY COMPONENTS AT ±y

DETERMINE THE l/Q MISMATCH
OF THE RECEIVER FRONT END
USING THE FOURIER COEFFICIENTS
(CPR ,CP| ,CMR ,CM|)

FIG. 3

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