2.5 GHz Wide Band Linear Amplifier with Feedforward Lineariser on a Board

Abstract

A wide band feedforward lineariser amplifier we have developed is described. In particular, we report the IM3 improvement obtained without automatic adaptive control circuits, indicating the possibility of realizing small, low-cost products. We designed a lineariser amplifier for 2.5 GHz band to demonstrate the effectiveness of our approach and measurement revealed the wide band linearising capability of over 100 MHz.

Performance of feed‐forward linearizers of power amplifiers in OFDM systems under complex gain errors

“…It is evident from (23) and (24) that this ratio approaches unity as the complex gains are at their optimum values, that is, It is evident from (23) and (24) that this ratio approaches unity as the complex gains are at their optimum values, that is,…”

“…In the first approach, the amplifier is operated at a point further in the linear region, or equivalently, a point with a large power input back-off (IBO). These complex gains are used to compensate for drifts in the main and error amplifier gains [23][24][25][26][27]. The second approach is to use a linearization technique such as predistortion, feed-forward (FF), feedback, and envelope elimination and restoration approaches [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20].…”

“…The second approach is to use a linearization technique such as predistortion, feed-forward (FF), feedback, and envelope elimination and restoration approaches [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Out of these techniques, FF linearization has been the most attractive approach in OFDM systems because of the wideband nature of the analog circuitry used in manipulating the signals in the FF implementation [21][22][23][24][25][26][27][28]. The operation of the FF techniques is basically concerned with canceling the distortion signal.…”

“…Therefore, a significant problem in the design of FF linearization schemes is the imbalance in the complex gains used in the signal and distortion cancelation loops of the FF system. These complex gains are used to compensate for drifts in the main and error amplifier gains [23][24][25][26][27]. Imbalances in these complex gains result in imperfect signal cancelation, which compromises the overall performance of the FF system.…”