Novel reduction technique of the non-linear distortion at the receiving point in the multi-beam active phased array antenna

The reduction technique of the non-linear distortion (NLD) is investigated in the multi-beam active phased array antenna (APAA) with the modulated signals. In the multi-beam APAA, NLD is given by the sum of intermodulation distortion (IMD) and interference distortion (IFD). IMD is generated by amplifying the modulated signal nonlinearly. IFD is generated by interference between the carriers. In this paper, it makes clear analytically that the IMD-beams and the carrier-beams are radiated in the same direction, however, the IFD-beams are radiated in the different directions. So that, the multibeam APAA can reduce NLD at the receiving point by removing IFD. In the two-beam APAA with the modulated signals, radiation pattern is calculated. It can be confirmed that IFD-beams and carrier-beams are radiated in the different direction. NPR in the direction of the carrier-beams is improved of 1.3 dB. The improvement is shown to be independent of the output back-off of the power amplifiers. This reduction technique is especially effective in the saturation region where the predistortion linearizer cannot reduce the distortion.