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Constant Envelope Modulation using Non-Linear Power Amplifie - RF
Cafe Forums
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| Waverider
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Post subject: Constant Envelope Modulation using Non-Linear Power Amplifie
Posted: Tue Jun 21, 2011 6:20 am
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Joined: Sat Apr 22, 2006
2:37 am
Posts: 6
Location: SoUtH EaSt of
AsIa |
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As we know, we like to utilize the power amplifier
in non-linear/saturation region for its maximum
power efficiency.
We also know that only
constant envelope modulation scheme can use non-linear
power amplifier.
So my questions are:
1. Are basic form of BPSK and QPSK (without
pulse shaping) considered constant envelope modulations?
2. If they are constant envelope modulation
schemes, we can employ a non-linear power amplifier.
Knowing that besides amplitude distortion a
non-linear amplifier can introduce, it can also
produce phase distortion on the output signal.
So for PSK modulation where information is modulated
in the phase, won't a non-linear amplifier distorts
the phase and hence information?
Pls help
solve my confusion.
Tee
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Waverider |
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Post subject: Re: Constant Envelope Modulation using Non-Linear Power
Ampl
Posted: Tue Jun 21, 2011 9:31 am
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Joined: Sat Apr 22, 2006
2:37 am
Posts: 6
Location: SoUtH EaSt of
AsIa |
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I think I got my answer, any form of PSK (BPSK or
QPSK) is not supposed to be constant envelope.
So this nulls all the questions I posted.
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IR |
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Post subject: Re: Constant Envelope Modulation using Non-Linear Power
Ampl
Posted: Thu Jun 23, 2011 1:54 pm
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Joined: Mon Jun 27, 2005
2:02 pm
Posts: 373
Location: Germany
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Constant envelope signals can also be distorted
in linear PA. It depends on what is the maximal
ouptput power compared to the P1dB of the given
amplifier.
Phase distortion and amplitude
distortion goes hand in hand. They can be measured
by Vector Signal Analyzer under average power conditions,
it is named EVM which is a vector contains phase
and magnitude.
_________________
Best regards,
-
IR
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Posted 11/12/2012
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