Problem with amplifier behind a SAW filter

[liberal]

I have circuit with an 50ohm amplifier behind a SAW filter.but the signal out from the amplifier has big second and third harmonics.why?

 

[VSWR]

Re: SAW+AMPLIFIER

The input signal of the amplifier may be close to the compression point of the amplifier. Then the level increases of the amplifier harmonics.

 

[khouly]

SAW+AMPLIFIER

yeah , this is the only reason , the input is high enough to make the amplfier near nonlinear region

khouly

 

[liberal]

Re: SAW+AMPLIFIER

No.I measure the signal input to the amplifer small enough.the saw has 20db IL,70MHz.

 

[khouly]

SAW+AMPLIFIER

what is the 1 dB comp point of this amp ?

and , what is the extact input power in this case

khouly

 

[liberal]

Re: SAW+AMPLIFIER

amp output 1db point is 10dbm,Gain is 20db.but the signal output from the SAW is -20dbm.the signal from the SAW is ok.

 

[khouly]

SAW+AMPLIFIER

mmm , yeah , ur far from the 1 dB compression , even if thr 1 dB point is the input is -10 dBm , i have assumed that the 10dBm is at output

how much attenutaion between the 2nd and the fundametal ?

khouly

 

[liberal]

Re: SAW+AMPLIFIER

maybe 10db

 

[khouly]

SAW+AMPLIFIER

10 dB between ur fundamental and the 2nd harmonic

ur harmonics is quit high

try to put the SAW after the amp

khouly

 

[liberal]

Re: SAW+AMPLIFIER

signal from the saw has no 2nd harm..it is only from the amp.

 

[khouly]

SAW+AMPLIFIER

yeah , i know , i meant to use th saw after the amp , coz the saw will attenuate the 2nd harmonic

khouly