 The cutoff frequency decreases as the radial propagation delay within a layer , relative to propagation delay between the layers, increases, introducing an upper limit on temporal resolution.
<clarity>  The cutoff frequency decreases as the radial propagation delay within a layer , relative to propagation delay between the layers, increases, introducing an upper limit on temporal resolution.
 The cutoff frequency decreases as the radial propagation delay within a layer , relative to propagation delay between the layers, introducing an upper limit on temporal resolution.