Many ships discover the hard way that meson weapons don't interact with matter enough to be blocked with the LDA fields.
Particle screens alter the resolution, frequency and wavelength on the LDA to operate on a subatomic scale, making it able to displace the beams of mesons and subatomic particles found in the long range meson cannons.
This interaction is enough to hold the Meson beam enough to cause it to decompose. This makes the shields very power hungry as the tighter shield effect is much more difficult to support.