Method and system for calibrating a quadrature phase modulator
AssigneeNEC Corporation
InventorAkihiro Kirisawa
Life of this patent
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Abstract
A calibration system for calibrating a quadrature phase modulator comprises a signal generator for generating a pair of sine-wave signals which are quadrature in phase, an adjusting section for adjusting the amplitude and phase of the pair of sine-wave signals, a DC voltage offset block for adjusting the DC level of the pair of sine-wave signals, and a frequency spectrum analyzer for monitoring the output of the quadrature phase modulator. The output spectrum of the quadrature phase modulator includes three maximal points, two of which are caused by amplitude error, phase error and carrier leakage and minimized by consecutive adjustment in the adjusting block to calibrate the quadrature phase modulator.
Claims28
A calibration system for a quadrature phase modulator having a pair of mixers each for mixing a corresponding one of quadrature modulation signals with a corresponding one of quadrature carrier waves and a hybrid block for synthesizing outputs of said mixers, said calibration system comprising:
- a spectrum analyzer for monitoring an output frequency spectrum of said hybrid block, said output frequency spectrum including an indication of at least one of an amplitude error and a phase error in an output of said hybrid block;
- a signal generator for generating a pair of sine-wave signals;
- an adjusting block for adjusting at least one of said sine-wave signals to correct at least one of the amplitude error and the phase error in an output of said quadrature phase modulator as indicated in said output frequency spectrum, said adjusted sine-wave signals being the quadrature modulation signals to said mixers;
- and
- wherein said adjusting block includes a first correction circuit which adjusts a first one of said sine-wave signals to correct said amplitude error and a second correction circuit which adjusts a second one of said sine-wave signals to correct said phase error.
A calibration system for a quadrature phase modulator having a pair of mixers each for mixing a corresponding one of quadrature modulation signals with a corresponding one of quadrature carrier waves and a hybrid block for synthesizing outputs of said mixers, said calibration system comprising:
- a signal generator for generating a pair of sequential data for representing a pair of sine-waves,
- an adjusting block for adjusting an amplitude of at least one of said sine-waves when there is an amplitude error in an output of said quadrature phase modulator and a phase of at least one of said sine-waves when there is a phase error in the output of said quadrature phase modulator, to thereby supply a pair of adjusted sequential data,
- a pair of D/A converters for converting said adjusted data to supply a pair of sine-wave signals as the modulation signals to said mixers, and
- a spectrum analyszer for monitoring an output frequency spectrum of said hybrid block.
A method for calibrating a quadrature phase modulator, including the steps of:
- supplying a pair of sine-wave signals and a pair of carrier waves to a pair of mixers of the quadrature phase modulator, respectively,
- monitoring an output frequency spectrum of the quadrature phase modulator to detect at least one of an amplitude error and a phase error of the quadrature phase modulator, and
- adjusting an amplitude of at least one of said pair of sine-wave signals when the amplitude error is detected and a phase of at least one of said pair of sine-wave signals when the phase error is detected.
A method for calibrating a quadrature phase modulator, said modulator having two mixers for mixing, respectively, different quadrature modulation signals with respective quadrature carrier waves and a hybrid block for synthesizing outputs of the mixers,, said method comprising steps of:
- inputting first and second quadrature modulation signals into said quadrature phase modulator;
- monitoring a first output of said quadrature phase modulator as generated based on said first and second quadrature modulation signals;
- detecting at least one of an amplitude error and a phase error between said quadrature modulation signals;
- adjusting at least one of said quadrature modulation signals to correct said at least one of an amplitude error and a phase error, and when the amplitude error and the phase error are both detected, adjusting a first one of said quadrature modulation signals to correct the amplitude error and adjusting a second one of said quadrature modulation signals to correct the phase error;
- and
- monitoring a second output of said quadrature phase modulator as generated based on said at least one of said adjusted quadrature modulation signals to detect that at least one of the amplitude error and the phase error have been corrected.
Dependencies are inferred from the claim text.