Compact multi-band RF transmitter solution will play a unique role in the forthcoming 4G-beyond and 5G wireless networks. The emerging RF class data convertor, i.e., RFDAC enables a promising single-chain multi-band RF transmitter solution. To combat the imperfections of practical nonlinear power amplifiers in the single-chain multi-band RF solution, we need multi-band RF signal conditioning unit. This paper presents a very compact single-chain multi-band digital predistortion (DPD) solution using only one under-sampling ADC and a low band-pass filter to replace the conventional DPD feedback paths. The experimental results verified the proposed compact multiband DPD architecture. Preliminarily, the proposed DPD scheme with a single real ADC at 76.8MSPS sampling rate can achieve satisfactory multi-band linearization performance, i.e., -55 dBc adjacent channel power ratio (ACPR) for 1GHz RF bandwidth.