This study presents a Zero-IF structured Stepped Frequency Continuous Wave (SFCW) radar system for range, respiration rate, and DOA estimation of the targets behind the walls. The radar hardware is a combination of SFCW and Uniform Linear Array (ULA) techniques. Four main improvements are done in signal processing. Averaging Delay Line Cancellation (ADLC) is proposed for moving-target indication. As a post-processing solution to the disruptive effects, a self-acting SVD-based algorithm is offered. The displacement signals of the targets are obtained after applying an additional phase extraction and wavelet-based filtering to lessen the phase discontinuities and noises. The Direction of Arrival (DOA) is estimated over the positive and negative range profiles of two separate antenna pairs. The median of these four angle values is used as the final DOA estimation. The performance of the system is tested with more than 150 experiments and compared with state-of-the-art studies.