Assuming there is an infinite periodically sinusoidal signal x with known frequency, one can sample x at Nyquist zone or sampling-rate to recover the signal. In terms of digital predistortion (DPD) with modulated signal as input, this paper will show the same concept that theoretically one can sample the feedback signal at arbitrary sampling rate to obtain the same coefficient of DPD or behavioural models as the one calculated from the high sampling rate feedback signal. The performance of a generalised DPD technique using a traditional memory polynomial with low-rate analog-to-digital device(ADC) is experimentally validated. The NMSE and ACPR results indicate the same performance by using an ADC sampling from 100 MHz to 10 MHz.