A C-band four-element integrated receiver system for digital beamforming (DBF) has been designed and implemented. For an array with digital beam processing, as a means of achieving precise pattern control (low sidelobe, adaptive nulling and high resolution) over large bandwidth and large dynamic range, the use of self-calibration techniques and circuitry was studied and evaluated. A multilayer linear self-calibration loop was also suggested and developed. Furthermore, in this thesis, the use of active antennas and optically controlled microwave devices in DBF systems was investigated. Integrated antennas, as the first stage of the whole DBF system, are required for overcoming excessive power loss in large microstrip array antennas, for avoiding degraded array far-field pattern performance due to spurious radiation from microstrip feed networks and for larger effective isotropic radiated power (EIRP). The possibilities of using active antennas instead of conventional passive antennas are studied. Several new active antenna structures were proposed and implemented. Detailed design procedures and experimental results were given. Other applications for spatial power combiners and larger active antenna arrays were also addressed. The optical control of microwave devices and subsystems is a rapidly growing area of research. In this thesis, the possibilities of using optical control in DBF systems are discussed. This thesis also describes the first reported application of frequency-dependent finite-difference time-domain ((FD)²TD) method for modelling optoelectronic microwave semiconductor devices. The two major effects of a constantly illuminated semiconductor plasma which must be analyzed are: (i) the strong influence of carrier diffusion and recombination-generation processes on photoconductivity and (ii) the depth to which the plasma penetrates the device. Two examples of using modified (FD)²TD method to analyze a two-dimensional optically controlled d, Doctor of Philosophy (PhD)