Feedforward is known to be one of the best methods for power amplifier
linearization due to its superior linearization performance and broadband stable
operation. However feedforward systems have relatively poor power efficiency and
are complicated due to the presence of two nonlinear amplifiers and the requirements
of amplitude, phase and delay matching within two different loops. In this thesis
stochastic characterization of a simple feedforward system with autocorrelation
analysis has been presented for Code Division Multiple Access (CDMA)
applications taking the amplitude and delay mismatches into consideration. It has
been assumed that, the input signal can be represented as Gaussian noise, main and
error amplifiers can be modeled with third order AM/AM nonlinearities and there
exists no phase mismatch within the loops. Hence closed form expressions, which
relate the main channel and distorted adjacent channel power at any point in the
feedforward circuitry to the system parameters, have been obtained. Consequently, a
mathematical handy tool is achieved towards specifying the circuit parameters
rapidly for optimum linearity performance and efficiency. The developed analytical
model has been verified by Radio Frequency (RF) and system simulations. An
alternative approach towards modeling feedforward systems for arbitrary signals has
also been brought into consideration and has been verified with system simulations.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/626721/index.pdf |
| Date | 01 January 2003 |
| Creators | Coskun, Arslan Hakan |
| Contributors | Demir, Simsek |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | Ph.D. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for public access |
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