US 8,135,055 B2 · I/Q calibration of transmit and receive paths in OFDM FDD communication systems

Abstract

I/Q gain and phase mismatches of both transmit and receive paths of an OFDM FDD transceiver are simultaneously estimated. An up-converted RF signal is generated when the transmit path performs IQ modulation on a reference signal having a single sideband tone. The up-converted RF signal is sent via a loop-back path to the receive path. A down-converted evaluation signal is generated when the receive path performs IQ demodulation on the up-converted RF signal. The single evaluation signal is used to determine the transmit path gain and phase mismatches and the receive path gain and phase mismatches. The four I/Q mismatches are estimated without using significant hardware nut otherwise used in the regular transmission of data signals. The I/Q mismatches in data signals are corrected by pre-processing the up-converted RF signals and post-processing the down-converted RF signals by adding attenuated components of the in-phase and quadrature-phase signals to each other.

Claims42

Dependent claims

A method comprising:

(a) receiving a single tone reference signal into a quadrature mixer of a transmit path, wherein the transmit path exhibits a gain mismatch and a phase mismatch;
(b) using the single tone reference signal to generate an up-converted RF signal;
(c) transmitting the up-converted RF signal via an RF loop-back path to a quadrature mixer of a receive path, wherein the receive path exhibits a gain mismatch and a phase mismatch;
(d) using the up-converted RF signal to generate a down-converted evaluation signal, wherein the down-converted evaluation signal is generated as a result of the single tone reference signal being received in (a);
and
(e) using the down-converted evaluation signal to determine the gain mismatch of the transmit path, the phase mismatch of the transmit path, the gain mismatch of the receive path, and the phase mismatch of the receive path substantially simultaneously at one time, wherein the evaluation signal has a first sideband tone with a first amplitude, a second sideband tone with a second amplitude, a third sideband tone with a third amplitude and a fourth sideband tone with a fourth amplitude, and wherein the gain mismatch and the phase mismatch of the transmit path and the gain mismatch and the phase mismatch of the receive path are determined based on the first amplitude, the second amplitude, the third amplitude and the fourth amplitude.

3 more elements

A method comprising:

(a) generating a reference signal;
(b) transforming the reference signal into an in-phase Tx component and a quadrature-phase Tx component;
(c) generating an up-converted in-phase signal by mixing the in-phase Tx component with an in-phase transmitter oscillator signal;
(d) generating an up-converted quadrature-phase signal by mixing the quadrature-phase Tx component with a quadrature-phase transmitter oscillator signal;
(e) generating a composite RF signal by adding the up-converted in-phase signal and the up-converted quadrature-phase signal;
(f) generating a down-converted in-phase signal by mixing the composite RF signal with an in-phase receiver oscillator signal;
(g) generating a down-converted quadrature-phase signal by mixing the composite RF signal with a quadrature-phase receiver oscillator signal;
(h) transforming the down-converted in-phase signal and the down-converted quadrature-phase signal into an evaluation signal, wherein the evaluation signal has a first sideband tone with a first characteristic, a second sideband tone with a second characteristic, a third sideband tone with a third characteristic and a fourth sideband tone with a fourth characteristic;
(i) determining the first characteristic, the second characteristic, the third characteristic and the fourth characteristic;
and
(j) determining an amplitude of the down-converted in-phase signal and an amplitude of the down-converted quadrature-phase signal at which the first characteristic increases and each of the second characteristic, the third characteristic and the fourth characteristic decreases.

8 more elements

A circuit comprising:

a first multiplier that receives a down-converted in-phase signal and generates a first attenuated component signal having an amplitude;
a second multiplier that receives a down-converted quadrature-phase signal and generates a second attenuated component signal having an amplitude, wherein a data signal with a single sideband tone is transmitted and used to generate the down-converted in-phase signal and the down-converted quadrature-phase signal;
a third multiplier that receives the down-converted in-phase signal and generates a third attenuated component signal having an amplitude;
a fourth multiplier that receives the down-converted quadrature-phase signal and generates a fourth attenuated component signal having an amplitude;
a first adder that generates an in-phase component signal by adding the second attenuated component signal to the first attenuated component signal;
a second adder that generates a quadrature-phase component signal by adding the third attenuated component signal to the fourth attenuated component signal;
and
a Fourier transform calculation circuit that generates a corrected signal using the in-phase component signal and the quadrature-phase component signal, wherein the corrected signal has a first sideband tone with a first characteristic, a second sideband tone with a second characteristic, a third sideband tone with a third characteristic and a fourth sideband tone with a fourth characteristic, and wherein the first multiplier adjusts the amplitude of the first attenuated component signal, the second multiplier adjusts the amplitude of the second attenuated component signal, the third multiplier adjusts the amplitude of the third attenuated component signal and the fourth multiplier adjusts the amplitude of the fourth attenuated component signal all such that the first characteristic increases and the second characteristic, the third characteristic and the fourth characteristic decrease.

5 more elements

A circuit that operates in a first mode and in a second mode, comprising:

an inverse Fourier transform calculation circuit that outputs an I-phase Tx component and a Q-phase Tx component;
a first correction circuit having a first multiplier and a third multiplier that receive the I-phase Tx component and having a second multiplier and a fourth multiplier that receive the Q-phase Tx component;
a second correction circuit having a fifth multiplier and a seventh multiplier that receive a down-converted in-phase signal and having a sixth multiplier and an eighth multiplier that receive a down-converted quadrature-phase signal, wherein the second correction circuit generates an I-phase Rx component and a Q-phase Rx component;
a Fourier transform calculation circuit that receives the I-phase Rx component and the Q-phase Rx component;
and
a digital signal processor, wherein in the first mode the inverse Fourier transform calculation circuit receives a reference signal and the Fourier transform calculation circuit generates an evaluation signal, wherein the evaluation signal has a first sideband tone with a first characteristic, a second sideband tone with a second characteristic, a third sideband tone with a third characteristic and a fourth sideband tone with a fourth characteristic, wherein the digital signal processor uses the evaluation signal to determine the first characteristic, the second characteristic, the third characteristic and the fourth characteristic, wherein the digital signal processor determines a first multiplication factor and a third multiplication factor by which the first and the third multipliers attenuate the I-phase Tx component, a second multiplication factor and a fourth multiplication factor by which the second and the fourth multipliers attenuate the Q-phase Tx component, a fifth multiplication factor and a seventh multiplication factor by which the fifth and the seventh multipliers attenuate the down-converted in-phase signal, and a sixth multiplication factor and an eighth multiplication factor by which the sixth and the eighth multipliers attenuate the down-converted quadrature-phase signal, and wherein the digital signal processor determines the first, second, third, fourth, fifth, sixth, seventh and eighth multiplication factors such that the first characteristic increases and each of the second characteristic, the third characteristic and the fourth characteristic decreases.

3 more elements

A non-transitory processor-readable medium for storing instructions operable in a wireless device to:

(a) generate a reference signal;
(b) transform the reference signal into an in-phase Tx component and a quadrature-phase Tx component, wherein an up-converted in-phase signal is generated by mixing the in-phase Tx component with an in-phase transmitter oscillator signal, wherein an up-converted quadrature-phase signal is generated by mixing the quadrature-phase Tx component with a quadrature-phase transmitter oscillator signal, wherein a composite RF signal is generated by adding the up-converted in-phase signal and the up-converted quadrature-phase signal, wherein a down-converted in-phase signal is generated by mixing the composite RF signal with an in-phase receiver oscillator signal, and wherein a down-converted quadrature-phase signal is generated by mixing the composite RF signal with a quadrature-phase receiver oscillator signal;
(c) transform the down-converted in-phase signal and the down-converted quadrature-phase signal into an evaluation signal, wherein the evaluation signal has a first sideband tone with a first characteristic, a second sideband tone with a second characteristic, a third sideband tone with a third characteristic and a fourth sideband tone with a fourth characteristic;
(d) determine the first characteristic, the second characteristic, the third characteristic and the fourth characteristic;
and
(e) determine an amplitude of the down-converted in-phase signal and an amplitude of the down-converted quadrature-phase signal at which the first characteristic increases and each of the second characteristic, the third characteristic and the fourth characteristic decreases.

3 more elements

A circuit comprising:

(a) a first correction circuit that corrects for both an up-conversion phase mismatch and an up-conversion gain mismatch between an up-converted in-phase signal and an up-converted quadrature-phase signal, wherein the first correction circuit multiplies an I-phase Tx component by a first multiplication factor and by a third multiplication factor, and wherein the first correction circuit multiplies a Q-phase Tx component by a second multiplication factor and by a fourth multiplication factor;
(b) a second correction circuit that corrects for both a down-conversion phase mismatch and a down-conversion gain mismatch between a down-converted in-phase signal and a down-converted quadrature-phase signal, wherein the second correction circuit multiplies the down-converted in-phase signal by fifth multiplication factor and by a seventh multiplication factor, wherein the second correction circuit multiplies the down-converted quadrature-phase signal by sixth multiplication factor and by an eighth multiplication factor;
and
(c) means for determining the first, second, third, fourth, fifth, sixth, seventh and eighth multiplication factors based on evaluating a single evaluation signal.

1 more element

Dependencies are inferred from the claim text.

I/Q calibration of transmit and receive paths in OFDM FDD communication systems

Life of this patent

I/Q calibration of transmit and receive paths in OFDM FDD communication systems

Life of this patent

Abstract

Claims42