The effectiveness of a wearable sinusoidal dipole antenna sensor in monitoring respiratory activity is investigated. An experimental setup combining the antenna sensor and a highly accurate optical tracking system is utilized, and a strong correlation between the antenna's reflection signal and the optical tracker is demonstrated during various respiratory behaviors. Obtained results show the antenna sensor's high accuracy in detecting respiratory cycles, amplitudes, and identifying sleep apnea events. The maximum mean squared error in cycle timings is calculated as 0.0044 seconds squared, and the maximum relative error of measured amplitudes is calculated as ±3.95%. Overall, these findings underscore the potential of sinusoidal antenna sensors as an effective tool for respiratory monitoring.