We propose and demonstrate a wavelength-division multiplexing (WDM)-based degenerate architecture for array photonic analog to digital converters (ADCs), which can be applied in phased array and multiple input multiple output (MIMO) systems. This architecture is capable of optical sampling and demultiplexing simultaneously with excellent synchronization and consistency. In the experiment, the four-channel array photonic ADCs is realized with a 20 GSa/s sampling rate for each channel. The synchronization accuracy among channels is below 0.2 ps. The frequency response uniformity in the operating frequency range of 20 GHz is also characterized. The effective number of bits is ∼6.5 bits within 20 GHz. Furthermore, we successfully apply the array photonic ADCs in wideband digital beamforming of multiple linear frequency modulated signals at 8-10 GHz.