Digital trigger filter for a real time digital oscilloscope

摘要

A real time - dso is equipped with a digital trigger filter, which has a high frequency suppression, however, a lower frequency, an alternating signal - and a trigger signal is carried out of the same. The digital trigger filter comprises a first and a second digital implemented iir - (infinitely input response) - filter. A digitized conditioned to the first input signal is applied - an iir filter. The same has pick-offs, which the trigger signal output, to supply signals which for a high - and low frequency are required under therewithin. The high frequency suppression of gear signal of the first iir - filter is essentially a low-pass output signal (3 db at 50 khz) and is also known as the digital input signal to the second iir - filter is used, the output signal in the form of a much more aggressive suppression of high frequencies, (3 db at 50 hz). The ac - trigger signal output, by means of a subtracting the output signal of the second iir - filter from the original input signal to the entire digital filter generates a trigger, and the dc - trigger signal output is simply to be equal to the original input signal. A mux selects, from which trigger signal to a digital trigger comparator is applied.