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Gain calibration for direct modulation synthesizer using a look-up table searched by a reduced count from an overflow counter
Gain calibration for direct modulation synthesizer using a look-up table searched by a reduced count from an overflow counter
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机译:使用查找表对直接调制合成器进行增益校准,查找表通过溢出计数器的减少的计数进行搜索
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摘要
A two-point modulation Phase-Locked Loop (PLL) has a gain-adjustable voltage-controlled oscillator (VCO). A digital data modulation signal is combined with a carrier and input to a feedback divider. The data modulation signal is also input to a Digital-to-Analog Converter (DAC) to generate an analog voltage to a second input of the VCO. A calibration unit divides the VCO output and counts pulses. During calibration, the data modulation signal is set to minimum and then maximum values and VCO output pulses counted. A count difference for the data modulation signal at maximum and minimum values is input to a Look-Up Table (LUT) to read out a gain calibration value. During normal operation mode, the gain calibration value from the LUT is applied to a second input of the DAC, which drives the VCO to adjust VCO gain. A switch before the VCO opens the loop for faster open-loop calibration.
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