An actual RF transformer’s lower cutoff frequency is dictated by the winding’s active inductance, and the high frequency cutoff is dominated by the inter-winding and intra-winding capacitance. The insertion loss in the operating bandwidth is a product of the ohmic losses in the primary and secondary windings, as well as the dissipation within the core. As the ohmic losses tend to be a function of frequency and temperature, the transformer’s effective operating bandwidth is limited by these factors. Several RF transformer types introduce leakage inductances due to incomplete magnetic coupling between the windings. As the reactance of the leakage inductance is proportional to frequency, these parasitics reduce the return loss at high frequency and increase the insertion loss at lower frequency.