Microwave imagers featuring a fully electronic scanning are highly demanded in security, industrial, and medical applications. Planar multistatic arrays operating at close ranges offer exceptional image resolution and illumination coverage compared to conventional far-field imaging. Novel solutions for synthesizing multistatic arrays for close range imaging with a scalable topology are introduced in this work along with detailed experimental verifications in the millimeter-wave range. Consequently, an electronic microwave imager based on modern digital-beamforming techniques has been successfully realized. High quality imaging of humans has been demonstrated, which represents a key milestone for the future generations of personnel screening systems required for securing air traffic as well as critical infrastructures. The work establishes the theoretical foundations for designing electronic microwave imagers, while addressing the associated challenges, e.g., image reconstruction, illumination adjustment, signal processing, hardware architecture, calibration technique, and results interpretation. The achieved three-dimensional complex-valued images open vast opportunities for new applications to effectively utilize the advanced capabilities of microwave imaging.