The subject of the thesis concerns microstrip antennas, in particular those operating at millimeter waves. Millimetre-wave technology is being emphasized because of its capacity to transfer massive amounts of data. The antenna design challenges, as well as the benefits of the specified spectrum, are several, making this an extraordinarily rich and profound topic of research in recent and future years. This thesis aims to provide new structures of microstrip antennas operating at millimeter waves that meet the requirements of wide bandwidth and high gain while granting a degree of miniaturization and compatibility with the LTCC technology for integration and packaging solution. For this, very powerful commercial software such as the CST Microwave Studio and the ANSY S HF SS will be used. The ease of simulation on such software will allow us to better interpret and explain the results. Throughout the thesis, novel antennas are designed, manufactured, and characterized for optimal operation in terms of bandwidth, gain, efficiency, polarization, and their integration using advanced technologies and experience.