Technique to characterise transient behavioural of multistage RF power amplifier for two-way radio applications
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A new technique to characterise the behavioral response of multistage RF power amplifier (PA) is presented. A simplified design methodology of closed loop PA with DC current sensing of multistage PA (cascaded) and voltage shaping algorithm is introduced in this study. An accurate characterisation of transient behavioral which includes ramping of RF energy from noise level to steady state level and adjacent channel transient power (ACTP), shows a high degree of correlation with measurement level for wideband RF PA operation (400–520 MHz). A prototype board is fabricated and measurement results demonstrated good correlation with transient behavioral model simulation. On board measurements demonstrated transient timing response of 1 ms while maintaining good ACTP of less than -60 dB over the wide frequency range of 400–520 MHz.