An amplifier linearization method based on a quadrature balanced structure

A quadrature balanced structure is presented for linearizing amplifiers. It works by reducing the most annoying distortion component: the third-order intermodulation. This arrangement has some advantages over the negative feedback method, which is prone to oscillations. It also has advantages over predistortion and feedforward linearization methods, as it is simpler and needs no adjustments. Theoretically, third-order intermodulation products would be totally eliminated when using the proposed arrangement. In practice, it was observed that, even with nonperfectly balanced amplifiers, the third-order intermodulation level was reduced up to 17 dB. The fifth-order intermodulation components were not reduced.