Testing tone free close loop notch frequency calibration for delta-sigma data converters

A receiver module for a front-end circuit of a radio, said receiver module comprising:

• an analog-to-digital converter (ADC) that converts analog signals to digital signals;
• a Fast-Fourier transform (FFT) circuit responsive to the digital signals from the ADC and converting the digital signals to frequency spectrum signals;
• a moving average circuit responsive to the frequency spectrum signals from the FFT circuit, said moving average circuit smoothing out the frequency spectrum signals by applying a moving average to the frequency spectrum signals;
• a differentiator circuit responsive to the smoothed frequency spectrum signals from the moving average circuit and differentiating the frequency spectrum signals to make the signals linear;
• a minimum finding circuit responsive to the differentiated frequency spectrum signals from the differentiator circuit and converting the differentiated frequency spectrum signals into a positive value for frequencies above a notch frequency in the differentiated signals and a negative value for frequencies below the notch frequency in the differentiated signals;
• and
• an adaptive control circuit responsive to the positive and negative values from the minimum finding circuit, said adaptive control circuit comparing a transition between the negative values and the positive values to a desired frequency value to identify a difference therebetween, and providing a calibration signal to the ADC if the difference is greater than a predetermined threshold value.