Power Amplifiers Linearization Based On Complex Gain Memory Predistortion
Power Amplifiers (PAs) are important components in communication systems and are nonlinear. The nonlinearity creates out of band distortion beyond the signal bandwidth, which interferes with adjacent channels. It also causes distortions within the signal bandwidth, which decreases the bit error r...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English English |
| Published: |
2010
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/12260/1/FK_2010_4_.pdf |
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| Summary: | Power Amplifiers (PAs) are important components in communication systems and are
nonlinear. The nonlinearity creates out of band distortion beyond the signal
bandwidth, which interferes with adjacent channels. It also causes distortions within
the signal bandwidth, which decreases the bit error rate at the receiver. Digital
predistortion is one of the most cost effective ways among all linearization techniques
to compensate for these nonlinearities.
In this thesis a novel technique for compensating memory effects and out of band
distortions is proposed and is called Complex Gain Memory Predistortion (CGMP).
The main advantage of the CGMP technique as compared to the memory polynomial
technique is the ability of this technique to compensate all the memory effects inside
the PA. Two structures of the CGMP technique are proposed. The CGMP technique is
examined using two approaches, simulation and experiment. Power amplifiers are modeled with memory polynomial technique to examine the effects of the memory
that causes increment in Adjacent Channel Leakage Ratio (ACLR). To implement this
method, the complex divider is required. This complex divider is then designed and
implemented in Field Programmable Gate Array (FPGA) and combined with other
parts to make the predistortion block. The CGMP is implemented in Virtex 5 FPGA
and simulated using Xilinx blocks in Matlab. In the experimental approach the CGMP
is examined with the actual power amplifier ZVE-8G from Mini Circuit. Finally the
CGMP technique is compared with memory polynomial method and validated using a
1.9 GHz 60W LDMOS power amplifier that is designed in simulation and various
signals such as 2-carrier WCDMA with 10 MHz carrier spacing and Mobile WiMAX
with 10 MHz bandwidth. The simulations results showed between 25 to 30 dB
improvement in ACLR and almost 5 dB improvement as compared to the memory
polynomial method. The experimental results also show around 10 dB reduction in
ACLR with applying QPSK signal with 1 MHz bandwidth. The improvement of 7
percent in Power Added Efficiency (PAE) is also achieved. |
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