Abstract:
A method of correcting the oscillator-sensitivity by amplifying or attenuating the control-voltage of the oscillator is developed. The size of the correction depends on the difference in oscillator-sensitivity compared to that of an ideal oscillator. This error is measured and the correct correction constant calculated.
To facilitate the measurements and correction extra circuits are developed and inserted in the loop. The circuits are both analog and digital. The analog circuits are mounted on an extra circuit board and the digital circuits are implemented in VHDL in an external FPGA.
Tests and theoretical calculations show that the method is valid and able to correct both positive and negative variations in oscillator-sensitivity of up to a factor ±2.5 times. The bandwidth of the loop can be adjusted between 2 to 15 Hz (up to ±8 dB, relative an unmodified loop).
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