Antenna design in CST varies depending on the intended application and learning objective. At a basic level λ/4 monopoles microstrip patch antennas and dipole antennas can be employed. At an intermediate level U-slot patch antennas CPW-fed wideband monopoles dual-band structures MIMO systems patch arrays DGS-based antennas and printed circuit dipoles with baluns are utilized. At an advanced level mmWave patch or slot arrays helical antennas DRAs Vivaldi antennas log-periodic antennas leaky-wave antennas spiral antennas and RIS or FSS unit cells can be implemented.
Clarifying Your Question: When you ask about the "best antenna," do you mean:
The easiest antenna to learn in CST?If so, I recommend starting with basic designs like a dipole, IFA (Inverted-F Antenna), PIFA (Planar Inverted-F Antenna), or patch antenna. These will help you grasp fundamental antenna mechanisms.
The best antenna for practical applications?In that case, focus on terminal antennas (e.g., IFA, PIFA, loop antennas) commonly used in devices like smartphones and IoT products. A valuable future study could be multimode generation in IFA antennas, which enhances performance in compact designs.