On design of linear RF power amplifier for CDMA signals

Abstract

In this paper, we analyze the nonlinear effect of an RF power amplifier on CDMA signals and then derive the direct relation between the power transistor's traditional nonlinearity parameter, the third order intermodulation coefficient (IP3), and an estimate of the out‐of‐band emission levels for CDMA signals which is used in IS‐95 [1] for the control of the amplifier's nonlinearity. This result will be useful to system and component engineers in design of RF power amplifiers for CDMA wireless systems. © 1998 John Wiley & Sons, Inc. Int J RF and Microwave CAE 8: 283–292, 1998

Estimation of Intermodulation Rejection Value as a Function of Frequency in Power Amplifier Using AM-AM and AM-PM Diagrams Based on Power Series Analysis

“…The cause of this error is due to the higher value of a 1 , that is the dominate factor in calculating IM 1 , than the other factors. The coefficient a 1 is related to the linear gain G of the amplifier, and the coefficients a 3 and a 5 , that are the dominate factors in calculating IM 3 they have smaller values than a 1 and, so, error in a 1 shows higher difference than errors in a 3 and a 5 , as we can see in Figures 3 and 4.…”

“…Generally, IM3 is used as a linearity parameter, but when an input signal becomes large, higher order IM products are also generated [3]. So, by using our model, an analytical expression that relates IM product in general order to the amplitude of the input of two tone test is derived.…”

“…Since the spectral regrowth is stringently regulated and is mostly generated by a nonlinear RF power amplifier [3], it is very important for RF system designers to predict the distortion effects of power amplifiers and analyze its effect on the output.…”

“…The phase variations have an important effect on the spectral regrowth [7]. However, similar previous models only used AM-AM diagram to characterize power amplifier's transfer functions [3,[8][9][10][11] while such an effect is considered in [7,[12][13][14][15]. Although, in this case, transfer function's coefficients have become complex and this increases the difficulty of the calculations, but neglecting the AM-PM distortion causes many problems in predicting output spectrum [16][17][18].…”

“…It is found that adjacent channel power ratio performances is not only dependent on the input signal magnitude (or power) but also dependent on the bandwidth of the signal that is used [19]. Main advantage of this model is that we don't neglect the frequency dependence of power amplifier's transfer function coefficient that makes asymmetric spectrum in the upper and lower band which is not taking into consideration in [3,7,14,15]. The factor is added in our model with considering our transfer function's constants as a function of input frequency besides they are complex.…”