The impact of channel spacing on memory polynomial model in concurrent dual-band RF power amplification

This paper investigates the impact of frequency separation between RF channels on the non-linear behavioural model of a 30MHz to 2000MHz, 25W GaN WideBand Power Amplifier. Tests have been carried out under the presence of concurrent dual-band RF input signals. The measurement has been made with one channel (Channel-B) fixed at 1GHz, and the other channel (Channel-A) centred at different spectral points between 850MHz and 960MHz. When the frequency difference (Δf) between the two channels is 40MHz, Channel-A and Channel-B have shown an Adjacent Channel Power Ratio (ACPR) improvement of 15dB and 13dB respectively at memory depth (k value) of two for both. When Δf is increased to 80MHz, 15dB ACPR improvement is obtained. These results show that the frequency spacing between the RF channels affects the required memory depth of the memory polynomial behavioural model. The proposed model characterizes the behaviour of the RFPA in the presence of the aggregated RF input channels. The overall behavioural model coefficients have been reduced by 25% when Δf=80MHz, and reduced by 50% when Δf=150MHz.