P. P. LI ET AL.

Copyright © 2013 SciRes. CN

In this test, the nonlinearity of the model was truncated

to order 5. For comparison, the value of α was set from

0.2 to 2. To evaluate the model’s fidelity in the time do-

main, the NMSEs and number of coefficients for each

partial model were calculated. These results are shown in

Figure 1. Due to the fact that memory effects of different

PAs were not the same，so the value of α was different

for different PAs. In this paper, the value of α was set to

1.6 while the performance of proposed model for the

tested PA was better and with lesser number of coeffi-

cients.

To show the model accuracy in the frequency domain,

the spectra of modeled errors are plotted in Figure 2. It

can be seen that the error signal spectrum of our pro-

posed model is very small, while significant errors are

generated in the output predicted by the memoryless mod-

el. For reference, the spectrum of the simulated output is

also plot t e d in Figure 2.

4. Conclusion

An efficient and effective Volterra model pruning me-

Figure 1. Model performance in the time domain.

Figure 2. Sample frequency domain output and modeled

error spectra.

thod for RF PAs has been presented in this letter, which

based on a function of the sum of nonlinearity order with

the sum of memory length. The advantage of this model

reduction approach is that it allows ef ficient reduction of

the model complexity, while keeping the essential prop-

erties caused by memory effects of a real PA. With a

Doherty PA tested, the proposed model can be employed

to characterize a nonlinear PA with memory effects in

high accuracy.

5. Acknowledgements

The research work is supported by Chinese Major Na-

tional Science and Technology Projects

(No.2010ZX03007-003).

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