RF receiver mismatch calibration system and method
View Patent ↗A calibration system for an RF system that includes an RF receiver capable of operating in a normal mode and in a calibration mode. The calibration system includes a phase delay unit provided on at least one of an I channel output and a Q channel output of the RF receiver. The system further includes a phase detector configured to detect a phase difference between the I channel output of the RF receiver and the Q channel output of the RF receiver. The system also includes a calibration control unit configured to provide a digital calibration control signal to the RF receiver based on the phase difference as provided by the phase detector.
1. A calibration system for an RF system that includes an rf receiver capable of operating in a normal mode and in a calibration mode, comprising:
one or more phase/amplitude mismatch calibrating elements integrated with at least one RF receiver component selected from the group composed of a local oscillation buffering circuit, a divide-by-two circuit, and a down conversion mixer;
a calibrated phase delay unit provided on at least one of an I channel output and a Q channel output of the RF receiver;
a phase detector configured to detect a phase difference between the I channel output of the RF receiver and the Q channel output of the RF receiver with the calibrated phase delay; and
a calibration control unit configured to provide a calibration control signal to the RF receiver based on the phase difference as provided by the phase detector;
wherein the calibrated phase delay unit delays one or both of the I channel output and the Q channel output during a calibration mode to make I channel phase equal to Q channel phase.
2. The calibration system according to claim 1 , wherein the RF receiver comprises:
a frequency generator unit configured to provide a first LO signal to an input of the RF receiver when in the calibration mode, and a second LO signal lower in frequency than the first LO signal; and
a mixer configured to receive the input to the RF receiver on an input port, and to mix the input signal with the first and second LO signals when in the calibration mode, and to provide a mixed output signal as a result.
3. The calibration system according to claim 2 , further comprising:
an RF antenna configured to receive a wireless signal when in the normal mode; and
a low noise amplifier configured to receive the wireless signal output from the RF antenna when in the normal mode, and to receive the first LO signal output from the frequency generator unit as the input to the RF receiver when in the calibration mode, the low noise amplifier configured to provide a low-noise-amplified output to the RF receiver.
4. The calibration system according to claim 1 , wherein the phase delay unit comprises a voltage controlled delay unit.
5. The calibration system according to claim 1 , wherein the phase delay unit comprises a quarter-phase delay unit provided on the I channel or the Q channel output of the RF receiver.
6. The calibration system according to claim 1 , wherein the phase delay unit comprises a three-quarters phase delay unit provided on the Q channel or the I channel output of the RF receiver.
7. The calibration system according to claim 1 , wherein the calibration control unit comprises:
a counter configured to provide a count value as a time delay signal to the phase delay unit, in accordance with the phase detected output provided to the counter by the phase detector.
8. The calibration system according to claim 2 , wherein the calibration control unit provides a first calibration signal to the frequency generator unit and a second calibration signal to the mixer, based on the phase detected output provided by the phase detector.
9. The calibration system according to claim 1 , further comprising:
a baseband I filter provided between the I channel output of a frontend of the RF receiver and the phase delay unit; and
a baseband Q filter provided between the Q channel output of the frontend of the RF receiver and the phase delay unit; and
a gain mismatch control unit provided in at least one of the baseband I filter and the baseband Q filter outputs.
10. The calibration system according to claim 9 , wherein the gain mismatch control unit comprises:
an operational amplifier; and
a feedback resistor provided between an input port and an output port of the operational amplifier.
11. The calibration system according to claim 1 , wherein the calibration signal is a digital calibration signal.
12. The calibration system according to claim 1 , wherein the calibrated phase delay unit comprises a plurality of multiple-quarter-phase delay units provided on one or both of the I channel and the Q channel outputs of the RF receiver.
13. A method of calibrating an RF receiver, comprising:
providing a first local oscillation signal to an input of the RF receiver during a calibration mode, as an calibration input signal;
mixing the calibration input signal with a second local oscillation signal at a same frequency as the first local oscillation signal, and with a third local oscillation signal at a frequency lower than the first and second local oscillation signals;
delaying at least one of signals on I and Q channel outputs of the RF receiver;
detecting a phase difference between the delayed, at least one of signals on the I and Q channels; and
providing a calibration signal to the RF receiver based on the detected phase difference.
14. The method according to claim 13 , wherein the delaying step comprises:
delaying the I channel output by one-quarter of a period of the third local oscillation signal.
15. The method according to claim 13 , wherein the providing step comprises:
providing digital calibration bits as the calibration signal to the RF receiver.
16. The method according to claim 13 , wherein the providing step comprises:
providing the digital calibration bits to at least one of a mixer and a local oscillator of the RF receiver.
17. A calibration system for an RF system that includes an rf receiver capable of operating in a normal mode and in a calibration mode, comprising:
a phase delay unit provided on at least one of an I channel output and a Q channel output of the RF receiver;
a phase detector configured to detect a phase difference between the I channel output of the RF receiver and the Q channel output of the RF receiver; and
a calibration control unit configured to provide a calibration control signal to the RF receiver based on the phase difference as provided by the phase detector;
wherein the RF receiver comprises:
a frequency generator unit configured to provide a first LO signal to an input of the RF receiver when in the calibration mode, and a second LO signal lower in frequency than the first LO signal; and
a mixer configured to receive the input to the RF receiver on an input port, and to mix the input signal with the first and second LO signals when in the calibration mode, and to provide a mixed output signal as a result.
18. The calibration system according to claim 17 , further comprising:
an RF antenna configured to receive a wireless signal when in the normal mode; and
a low noise amplifier configured to receive the wireless signal output from the RF antenna when in the normal mode, and to receive the first LO signal output from the frequency generator unit as the input to the RF receiver when in the calibration mode, the low noise amplifier configured to provide a low-noise-amplified output to the RF receiver.
19. The calibration system according to claim 17 , wherein the calibration control unit provides a first calibration signal to the frequency generator unit and a second calibration signal to the mixer, based on the phase detected output provided by the phase detector.
20. The calibration system according to claim 17 , wherein the phase delay unit comprises a plurality of multiple-quarter-phase delay units provided on one or both of the I channel and the Q channel outputs of the RF receiver.