Strong- and broadband-spin-wave (SW) excitation/detection structures are useful for magnonic devices. In particular, such structures are essential for observing magnonic bandgaps of magnonic crystals (MCs). Therefore, this study proposes a manufacturable broadband-SW excitation/detection antenna structure suitable for evaluating MCs. The antenna structure comprises a microstrip line fabricated on a yttrium iron garnet on a metal-covered silicon substrate. Calculations were performed using a three-dimensional finite integration technique and dispersion curves of SWs. The proposed structure exhibited high performance because of the significantly short distance between the signal line and ground plane. The generated bandwidth was ~1.69 GHz for the 8.9-μm-wavelength SW at a frequency of 4 GHz. This work proposed an appropriate antenna structure for observing magnonic bandgaps, showing high potential for the development of MCs in integrated SW devices.