limit output <-10dBm

My input:-70~10dbm 150MHz
I want output<-10dBm insertion Loss<3dB
I use two PIN diobes parallel connect to earth,but it don't work well,output<10dBm.
who can help me,thank

use active bais

I have used bias voltage on PIN,when Vb<0.7V ,limited output>2dBm
if Vb>0.7v the PIN become a attenuator,the insertion loss will>3dB

so u need, senestive baising.
put coupler (more then 15 dB for good il at the path). put shotkey detector at the coupler, and the vidio out from the detector eill go to the limiter diode