This thesis presents the design and performance evaluation of electronically steered phased lens arrays operating at 140 GHz for high resolution sensing applications. The primary objective of the thesis is to design and analyze lens phased arrays fed by an array of leaky-wave antenna elements achieving 1 degree resolution, while having 20 degree field of view, 30dB single lens directivity and 70% spillover efficiency. Bi-directional ray-tracing approach is used to calculate the required weights for single lens beam steering together with GO/PO methods. Key parameters such as directivity, gain, spillover efficiency and maximum side lobe level are optimized using a graphical method called 'Two dimensional sweeps'. The results obtained using the proposed methods have been validated using full wave simulations.