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A more accurate and efficient millimeter-wave imaging algorithm for a monostatic system is presented in this paper. Firstly, a more precise physical model is implemented, which considers the propagation loss of both the incident wave and scattered wave. However, this physical model cannot be processed using classical mathematical methods such as spherical wave decomposition and Weyl identity. Instead, the method of stationary phase (MSP) is applied to derive the imaging formula. As a result, the proposed algorithm achieves superior imaging results for multiple targets at different ranges. Additionally, the range stacking technique is introduced to avoid time-consuming interpolation, which also contributes to improving computational efficiency comparing to the algorithms employing interpolation. The simulation results show that the proposed algorithm reduces the computation time by half. The proposed algorithm has been further verified through real data collected with our in-house developed prototype. [ABSTRACT FROM AUTHOR]

Projection adjustment is a technique that improves the rate of convergence, as measured by the number of iterations needed to achieve a given level of performance, of the Kaczmarz algorithm (KA) for iteratively solving a system of consistent linear equations, however at the cost of requiring additional time per iteration and increased storage. This hinders the applicability of the previously published Kaczmarz algorithm with projection adjustment (KAPA) to large-scale problems. An enhancement EKAPA of KAPA that uses projection adjustment only for a small subset of the equations is proposed for significantly reducing the time and storage requirements. An analysis of the behavior of EKAPA is provided. An illustration is given to show that EKAPA using a small subset of the equations for projection adjustment can achieve a speed-up over KA similar to that of KAPA in terms of the number of iterations, but requires much less computer time and storage; hence, it is more suitable for large-scale problems. [ABSTRACT FROM AUTHOR]