k to peak ILE is reduced to about one sixth that of the original. Randomisation should reduce the amplitude of high order harmonic and intermodulation products and the lower mean value of the quantising error should improve SFDR. Experiments indicated that with this ADC a large amplitude sine-wave dither (about ?15dB relative to FSR) was required to improve small signal SFDR. paring Fig. 3 and Fig. 4 it is clear that sine wave dither reduces SFDR for large signals. This is probably due to intermodulation products between the dither and the test signal being significant for large input signals. Dither can also be seen to linearise the signal to noise and distortion ratio (SINAD) plot and extend the dynamic range below the Fig. 3 threshold of44 dB. Full-size image (14K) Fig. 3. Standard ADC.
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