Why isn the high power RF burst coherent with the external trigger input signal?
A. This delay is due to the timing circuitry generating the gates, which are used to select the desired number of cycles from the CW RF signal and to turn on the gated amplifier. The gates turn on at the positive zero crossing of the RF CW signal and are on for a programmed number of RF cycles. If the external trigger is sent just after a zero crossing, then the circuitry will wait until the next zero crossing before starting the high-power RF burst. Therefore, there can be an uncertainty of up to 1 period of the operating frequency between the external trigger input and the start of the high-power RF burst. The “Trigger Out” signal is always coherent with the start of the RF burst.
