[HELP]OFDM amplifier question

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ofdm amplifier

Motorola amplifier MHL9838 used to amplify -23dBm 746MHz DVB-T signal (OFDM+16QAM).The gain is -5dB,but the one tone test gain is 19dB.
Another amplifier module (Mini-circuits company provided) has 44dB gain in one tone test,but has only 20dB gain in DVB-T signal test.Why?
 

Do you measure the gain correctly?
Take care to measure the integrated output power instead of the simple marker value.
Are you sure that you're driving the amplifier in linear region?
Mazz
 

for one tone test ,it is the marker value;
for OFDM signal test , it is the integrated power(over 8MHz channel ),-23dBm is an integrated value.
MHL9838 has P1dB=39dBm,gain=30dB
I am sure that the amplifier is in linear status.
Is it possible that it has variable gain for different modulation modes?
 

I've checked the data sheet; it's an LDMOS with no voltage gain control.
Do you have a properly designed test board and do you supply it at correct voltage (27 V)?
Do you measure the correct current consumption (770 mA)?
Mazz
 

I have used this amplifier in some products like gsm/cdma 2W amplifier module.
In these cases,it got right performance.
I used it to amplify OFDM signal for it is simple to use and 39dBm is enough for -23dBm input power.
The DVB-T signal has 9.5dB PAR(peak to average ratio),so I pick this amplifier to
get about 0dBm output power.
And I used attenuate network in the circuit,so the gain is only about 20dB.
 

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