Requirements for perspective medical system for non-invasive radiation diagnostics of functional state of biological organs and tissues, based on application of microwave sensing techniques, practically implemented in a smart antenna array, are synthesized. Estimates of characteristics of beam pattern and gain factor for the simulated smart antenna array meet the requirements for microwave medical imaging applications. A perspective diagnostic microwave imaging system is supposed to have high functional characteristics, enabling the possibility of precise imaging of biological organs and tissues without using contrast agents, and at a lower cost, compared with existing X-ray, magnetic resonance and positron emission tomography systems on the market.