The Substrate Integrated Waveguide (SIW) technology is a very promising candidate to provide widespread commercial solutions for modern communications systems. Its main advantage is the possibility to integrate passive/active components and antennas in the same substrate by using standard manufacturing processes, such as the Printed Circuits Board (PCB) processing technique. Nevertheless, the production of low-cost SIW devices is inherently linked to commercially available substrates and fabrication methods. In particular, these constraints usually limit (a) the frequency range of operation of certain SIW antennas and (b) the possibility of creating multimode structures dealing with orthogonal polarizations. The motivation of this PhD thesis is to overcome these two limitations by proposing innovative SIW components based on PCBs in order to favour the compatibility with existing systems and to lower their cost. Hence, the usage of the SIW technology would be extended towards new applications and scenarios. One type of antenna strongly affected by the limitation (a) is the H-plane SIW horn antenna. While standard horns are employed in many applications and in a wide range of frequencies, their counterparts in SIW technology are restricted to the Ka-band and above. At lower frequencies, commercial substrates are electrically thin and the performances of these end-fire antennas severely diminish. To solve this problem, a novel low-profile SIW horn antenna has been designed to be used at the Ku-band and below, while offering wideband characteristics. In addition, the horn shape has been further optimized to reduce the antenna footprint for a given directivity. In order to overcome the limitation (b), a substrate integrated guide able to simultaneously carry orthogonally polarized modes has been developed: the so called Extended Substrate Integrated Waveguide (ESIW). An ESIW dual-polarized system composed of an Orthomode Transducer (OMT) feeding a dual-polarized horn antenna has been designed and experimentally verified. The overall combination of concepts and ideas proposed in this thesis opens the door towards new SIW components that can increase the capacity, robustness and compactness ofmodern communication systems.