Miniaturized microwave components have drawn increased attention due to the size shrinking of the modern communication systems. This dissertation proposes two approaches to address this problem by reducing the size of the RF components and the antennas.

First, miniaturized substrate integrated waveguide components are introduced and developed by using the metamaterial concept. Traditional waveguide components have excellent performance but with a bulky size due to the above-cutoff frequency operation. We demonstrate that by loading the metamaterial elements, the rectangular waveguide can be operated well below the cutoff frequency while maintaining good performance. Based on the substrate integrated waveguide technology, their wave propagation characteristics are studied and their practical applications for guided and radiated RF/microwave components, including transmission lines, filters, couplers, diplexers, oscillators, and leaky-wave antennas, are proposed and implemented. These devices are substantially miniaturized with superior performance achieved.

Second, various miniaturized planar antennas are developed to meet the industry application requirements. Different techniques, such as the metamaterial resonators, meta-surfaces, multi-layer folded structures, and the shared radiator approach, are adopted to design different antennas which are suitable to be applied in many wireless systems, including the WLAN links, cellular phone systems and ultra-wideband communication systems. Some special antennas, such as dually or circularly polarized antennas, diversity antennas, are also designed for specified applications. These antennas exhibit good radiation performance with a smaller size compared with the conventional planar antennas. Some of them are going to be used in commercial WLAN communication systems.