Distortion compensation in wireless digital communication
AssigneeFujitsu Limited
InventorsTakeshi Ohba, Yasuhito Funyu, Hideharu Shako
Life of this patent
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Abstract
A distortion compensating technique applied to a transmitter for transmitting a quadrature modulated signal in a wireless digital communication system is provided. A phase adjustment value is determined for a quadrature demodulated feedback signal based on comparison between the feedback signal and a reference signal to be transmitted from the transmitter. This phase adjustment value is compared with the previous phase adjustment value. If the comparison result between the current and previous phase adjustment values satisfies a prescribed condition, correction for quadrature modulation, such as DC offset correction, orthogonality correction, or IQ amplitude correction, is performed.
Claims8
A distortion compensating device applied to a transmitter for transmitting a quadrature modulated signal in a wireless digital communication system, the distortion compensating device comprising:
- a phase adjusting unit configured to determine a phase adjustment value for a feedback signal subjected to a quadrature demodulation, based on a comparison between the feedback signal and a reference signal to be transmitted from the transmitter;
- a phase adjustment result storing unit configured to store a current phase adjustment result representing the determined phase adjustment value;
- a phase adjustment result comparison and determination unit configured to compare the current phase adjustment result with a previous phase adjustment result, and to output a comparison result;
- and
- a correction control unit configured to allow a correction for the quadrature modulation to be performed if the comparison result of the phase adjustment results satisfies a prescribed condition,
- wherein said correction control circuit increments a successful phase adjustment count if a difference between the current phase adjustment result and the previous phase adjustment result is within a predetermined range and performs the correction only if the successful phase adjustment count exceeds a prescribed value, and repeats incrementing the successful phase adjustment count and performing the correction until said correction is performed a target number of times, and
- wherein said prescribed condition is satisfied if said difference is within the predetermined range, the successful phase adjustment count exceeds said prescribed value, and the correction is performed said target number of times.
A distortion compensating method applied to a transmitter for transmitting a quadrature modulated signal in a wireless digital communication system, the method comprising:
- determining, in a phase adjusting unit of the transmitter, a current phase adjustment value for a feedback signal subjected to a quadrature demodulation, based on a comparison between the feedback signal and a reference signal to be transmitted from the transmitter;
- comparing, in a phase adjustment result comparison and determination unit of the transmitter, a current phase adjustment result representing the current phase adjustment value with a previous phase adjustment result, and outputting a comparison result;
- and
- allowing, in a correction control unit of the transmitter, a correction for the quadrature modulation to be performed if the comparison result of the phase adjustment results satisfies a prescribed condition,
- wherein said allowing increments a successful phase adjustment count if a difference between the current phase adjustment result and the previous phase adjustment result is within a predetermined range and performs the correction only if the successful phase adjustment count exceeds a prescribed value, and repeats incrementing the successful phase adjustment count and performing the correction until the correction is performed a target number of times, and
- wherein said prescribed condition is satisfied if said difference is within the predetermined range, the successful phase adjustment count exceeds said prescribed value, and the correction is performed said target number of times.
Dependencies are inferred from the claim text.