As the demand for higher data rates increases, wireless technologies (e.g., satellite communications, fifth Generation (5G) wireless communications, and automotive radars) are migrating toward millimeter-wave (mm-W) frequencies (30-300 GHz) to utilize the numerous unused spectra available over this frequency band. For truly ubiquitous coverage over the globe, high throughput Ka-band satellite communication (SATCOM) offers the most optimal and a unique solution for providing world-wide information and sensing. Of particular interest is the development of land, or close-to-land, mobile systems for high data rate communications with continuous coverage for on-the-move commercial platforms, including cars, airplanes, ships, and trains. A modular and scalable phased-array antenna (PAA) architecture wherein the entire phased-array system is made of identical sub-array modules (building blocks) is the most promising approach to develop cost effective and flexible systems for mass market applications. Obviously, such architecture depends on the availability of a high-performance antenna element, antenna subarray modules, and beam-forming circuits. These are the main topics investigated in this PhD thesis. Two approaches were extensively studied in this PhD research to develop intelligent steerable antenna array modules as building blocks for large-scale Ka-band SATCOM applications. The first approach targeted the development of a working prototype for a wide-angle beam-steering Ka-band active PAA (APAA). In this approach, two APAA architectures were proposed, designed, fabricated, and measured to validate the proposed concepts. Both approaches exhibit wide beam-steering angles and fast beam-forming capabilities with full control on amplitude and phase of each antenna element by utilizing an intelligent beam-forming circuit that was developed at CIARS (Centre for Intelligent Antenna and Radio Systems). The first architecture comprises a novel single-fed CP antenna element integrated with the intelligent beam-forming circuit, to construct a wide beam-steering and low-cost CP-APAA. A 4×16 CP-APAA was designed and fabricated using low-cost printed circuit board (PCB) technology and it was tested over the frequency range (29.5-30 GHz) over an angular range of 0o-±40o. The second architecture utilized a highly integrated and wide band dually-polarized antenna element as a core component for the realization of a high-performance, compact, and polarization-agile Ka-band APAA module. The proposed antenna module was used to construct a proof-of-concept 16×16 modular APAA to radiate a high polarization purity pattern over a wide beam-steering angles ≥70o. The second proposed approach investigated two novel wideband and passive steerable antenna concepts as attractive low-cost alternatives suitable for a wide range of emerging mm-W communication systems. Such antenna systems are made of passive components, antennas, phase shifters, and passive feeding networks to reduce the power consumption, cost, and complexity of conventional active electronically steered arrays. In order to build such systems, a high-performance antenna and passive phase shifter (invented at CIARS) were integrated to eliminate the necessity for costly variable gain amplifiers (VGAs). The first proposed concept is a novel CP passive PAA comprised of the proposed single-fed CP antenna integrated with the CIARS phase shifter. The novel high-performance passive phase shifter was controlled by a low-profile and low-power consumption novel magnetic actuator to overcome the limitation of state-of-the-art passive phased arrays. The proposed CP passive PAA was designed, fabricated and tested at Ka-band (29.5-30.5 GHz) over an angular range of 0o-±38o. The second concept proposed here is a novel reconfigurable reflectarray antenna (RAA) element with a true-time-delay functionality. Its reconfigurability is realized by utilizing the proposed phase shifter integrated with an aperture-coupled microstrip patch antenna (ACMPA) to receive and re-radiate the electromagnetic energy efficiently. The proposed RAA element was designed and tested at Ka-band (27.5-30 GHz).