S. I. Kuzlyakina, N. P. Chmyrova
Nonlinearity of power amplifiers of transmitters results in appearance of in-band and interference signal distortions with high spectral efficiency. One of ways of increase of linearity of transmitters is application LINC-structure. Its principle consists in a representation of a signal with amplitude and phase manipulation by two signals with phase manipulation which are separately amplified by nonlinear amplifiers. The disadvantage of this method is dependence of parameters on disbalance of branches of amplification. To reduce it they apply methods of adaptive correction. Examples of use of LINC-structure in VHF transmitter are known.
In the article the authors introduce the model of LINC transmitter with the correction circuit designed in Simulinc of MATLAB system and give the research results. The estimation of in-band interference distortions (in amplitude disbalancement up to 3 decibels and phase disbalancement up to 10 degrees) was made by spread of points of signal constellation of OFDM signals in the transmitter output and by probability of errors in the demodulator output.
Influence of clock rate of correction algorithm on a level of out-of-band interference distortions was investigated. The authors have concluded that to fulfill requirements on out-of-band collateral radiations of HF transmitters, clock rate of performance of algorithm of adaptive correction should be much higher than information rate.