A feed-forward amplifier using an equal group-delay signal cancellation technique

In this article, new signal cancellers that can match the out-of-phase and group delay of two signal paths simultaneously are proposed. The simultaneous matching of the out-of-phase and group-delay time between two paths can permit broadband signal cancellation. A feed-forward linear power amplifier that uses the proposed signal cancellers was fabricated for the IMT-2000 base station transmitting band. The main signal cancellation (first) loop of the fabricated feed-forward amplifier cancels the input signal by more than 26.3 dB and the intermodulation distortion (IMD) signal cancellation (second) loop cancels the IMD signal by more than 15.2 dB over a 200 MHz bandwidth. In the two-tone signals amplification process, the C/I ratio of the amplifier was improved by 21.2 dB, where the two tones were 2115 and 2165 MHz (Δf = 50 MHz), respectively.