Apparatus and method for calibrating local oscillation frequency in wireless communications
First Claim
1. A receiver comprising a digital automatic frequency control loop configured to receive a baseband input signal having a first frequency, said digital automatic frequency control loop comprising a frequency error discriminator, said frequency error discriminator being configured to produce an error measure, said digital automatic frequency control loop further comprising:
- a digital rotator configured to receive said baseband input signal having said first frequency, said digital rotator providing a rotated digital baseband output to said frequency error discriminator for producing said error measure.
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Accused Products
Abstract
According to a disclosed embodiment, a receiver comprising a digital rotator in combination with a frequency error discriminator in a digital automatic frequency control loop is used to arrive at accurate digital values used to calibrate a local oscillation frequency. A frequency error in the oscillation frequency of a local frequency generation loop causes a change in the baseband input signal frequency. The change in the baseband input signal frequency related to the frequency error in the local frequency generation loop can be detected as a phase rotation by the frequency error discriminator. By using the digital automatic frequency control loop, the frequency error introduced by the local frequency generation is determined with accuracy. The frequency error and corresponding control bits are entered into a calibration table. The calibration table may be used to adjust the local oscillation frequency for temperature changes, pilot frequency searching, and quick paging.
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Citations
25 Claims
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1. A receiver comprising a digital automatic frequency control loop configured to receive a baseband input signal having a first frequency, said digital automatic frequency control loop comprising a frequency error discriminator, said frequency error discriminator being configured to produce an error measure, said digital automatic frequency control loop further comprising:
a digital rotator configured to receive said baseband input signal having said first frequency, said digital rotator providing a rotated digital baseband output to said frequency error discriminator for producing said error measure. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method in a digital automatic frequency control loop comprising a digital rotator in combination with a frequency error discriminator, said method comprising steps of:
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receiving a digital baseband input signal having a first frequency;
supplying a rotated digital baseband output to said frequency error discriminator;
producing an error measure for causing an adjustment in said first frequency. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A receiver comprising a digital automatic frequency control loop and a local frequency generation loop, said digital automatic frequency control loop receiving a baseband input signal having a first frequency and said local frequency generation loop including an oscillator for oscillating at a second frequency, said digital automatic frequency control loop comprising:
a digital rotator configured to receive said baseband input signal having said first frequency, said digital rotator providing a rotated digital baseband output to a frequency error discriminator for producing an error measure, said error measure causing an adjustment in said first frequency, said adjustment corresponding to a frequency error in said second frequency. - View Dependent Claims (21, 22, 23, 24, 25)
Specification