The Research About Intermodulation Of Multichannel In Wireless Communication

Radio Frequency(RF)power amplifier is an important component in the transmitter,its main role is to increase the power of the RF signal to a level that it can be transmitted to the receiver through the air.There are two important design specifications which are linearity and power efficiency in power amplifier design,and they are mutually exclusive.In other words,the improvement of the linearity of power amplifier is at the cost of reducing the power efficiency,inversely,the improvement of the power amplifier of power amplifier is at the cost of sacrificing the linearity.The nonlinearity cause serious interference to the adjacent channels,and it also brings interference to in-band signal that can't be filtered out.Besides,it reduces SNR of the signal,so it affects the quality of the signal.On the other hand,with the rapid development of wireless communication,the spectrum resources become more scarce and precious,in order to improve the utilization efficiency of spectrum,frequency space between the adjacent channels become smaller and smaller.Thus it proposes a more serious challenge to the nonlinearity effect of RF power amplifiers.For the beginning,the analysis and simulation of the output of RF power amplifier under the condition of third-order nonlinear function model will be followed,including the total output of the desired channel,third intermodulation products(IM3),1-dB compression point and third-order intercept point(IP3).Next,the analysis and simulation of the output of RF power amplifier under the condition of fifth-order nonlinear function model will be given,including the total output of the desired channel,fifth intermodulation products(IM5),1-dB compression point and fifth-order intercept point(IP5).Through theoretical analysis and experimental simulation,the channels whose position is symmetrical have the same property for a given total number of channels,and the linearity get worse when the channel moves from both sides to the central.Besides,the linearity of the channel signal also degrades with the increasing of the total number of channels and the magnificent of the input signals.