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International audienceA significant improvement is demonstrated in the measured pulse-to-pulse stability of an S-band 6 W GaN high electron mobility transistor (HEMT) power amplifier by generating an appropriate pulse of the gate bias and thus a warm-up drain current just before each radio-frequency (RF) pulse of a periodic and coherent radar burst. The amplitude and the width of this gate bias pulse preceding each periodic RF pulse of the burst are experimentally varied to investigate the trade-off between the improvement of pulse-to-pulse stability and the total power-added efficiency. Finally, this technique of synchronised warm-up gate bias pulse demonstrated a 10 dB improvement of measured amplitude pulse-to-pulse stabilities to meet the critical stability requirement below −55 dB for the RF power amplifier

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