About the antenna switch ?

Hello guys !
What maybe influence the attenuation of the antenna switch low pass filter ?The spec say the attenuation is 30db for 2nd harmonic and 3rd harmonic in normal .But in practical layout ,the attenuation is much lower than spec , what maybe decrease the attenuation ?
Best regards !

If you are taliking about a surface mount component, the common mistake is to use an insufficient number of ground vias or too much pad length to connect the device to ground, a break in the ground plane due to unwise board layout--causing ground loops, or some stray leakage path like through a bias line.

If my memory is correct, Their excisting harmonic generation specification in ASM which counts on small Power input where as large power input for harmonic attenuation as your saying.

Regards,