Generalised digital predistortion of RF power amplifiers with low-rate feedback signal

Abstract

Abstract-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.

Undersampling Observation-Based Compact Digital Predistortion for Single-Chain Multiband and Wideband Direct-to-RF Transmitter

“…A generalized DPD comprises of a time-series-based behavioral model and least square (LS)-type (or its wider range derivatives) DPD parameter estimation algorithm. Particularly, this estimation can be performed by using feedback samples collected at any sampling rate as long as the ADC input bandwidth is sufficient to cover the whole observation band [14], and the captured data sequence can represent the statistical properties of the signals [15].…”

“…Previously, we initialized a DPD technique using the lowrate aliased feedback samples [13], [14]. Fig.…”

“…Fig. 3 captures the simplified diagram of the undersampling DPD introduced in [14], and it includes a data forward path with predistorter function at high data rate and a feedback path with undersampling function at low data rate. The DPD coefficients were estimated using the high-rate input signal and the aliased low-rate feedback signal under the direct learning structure.…”

“…As proposed in [14], the determined equation obtained by LS can be treated as the combination of autocorrelation matrix and cross-correlation matrix, as shown in…”

Digital Predistortion of Ultra‐Broadband mmWave Power Amplifiers with Limited Tx/Feedback Loop/Baseband Bandwidth

“…Tao et al in [17] proposed a random demodulation based reduced sampling rate method. Wang et al in [18,19] proposed a novel method using low feedback sampling rate to obtain the DPD coefficients, which is the same as the ones calculated with high sampling rates. Huang et al in [20] proposed a DPD function synthesis method by using undersampled feedback signal.…”