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Pout for different GSM,EDGE, WCDMA

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keshav_77

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Hi all,
One of freescale datasheet specifies(attached)

Typical GSM Performance: VDD = 28 Volts, IDQ = 500 mA, Pout =72 Watts CW
and for GSM EDGE

Typical GSM EDGE Performance: VDD = 28 Volts, IDQ = 700 mA, Pout =45 Watts Avg

my question is why Pout is different for different standards?, then what will be the Pout for WCDMA at same VDD=28 and IDQ =700mA.

pls suggest how to understand the datasheet and wireless standards.

thanks
 

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tony_lth

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Because different system have different modulation, GSM uses GMSK, mainly for voice. And EDGE modulation is more complicated. So the peak-average-ratio of the systems are different. If EDGE peka power is 70W, the average power should be 45W. And you can estimate the WCDMA power maybe can't reach 45W.
What is power value? There are some specifications, such as EVM to determine the max output power.
 

keshav_77

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Thanks tony,
The power @1dB compression is 108W CW.
1. is it right way initially to measure amplifier Pout_max or P1dB then power back off about the value of PAR to operate amplifier in linear mode?.
2. How to determine particular PAR or CCDF value for particular system theoretically.

example from wikipedia.

QPSK 0 dB
64QAM 3.7 dB
WCDMA downlink carrier 10.6 dB
OFDM ~12 dB
GMSK 0 dB

Thanks
 

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tony_lth

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QPSK 0 dB
64QAM 3.7 dB
WCDMA downlink carrier 10.6 dB
OFDM ~12 dB
GMSK 0 dB

Thanks
I don't know what the "dB" means?
Yes, should back off from P1dB. But you should use EVM to measure or simulate first before you design.

---------- Post added at 23:43 ---------- Previous post was at 23:42 ----------

In my experience, QPSK should back off 12dB for linerity system.
 
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