I'm trying to simulate pulse transmitted through bandpass filter (actually ,it is APD that has band pass type frequency response)
One of the problem is that the frequency respons is not like a typical band pass filter.
It is like a high-pass filter for low frequency and,like a low-pass filter
for high frequency.
I don't know how to get the
transfer function of such a filter,
Can I just multiply transfer funtions of two-filters?
Is it a linear, time-invariant system? If so, then yes. But...beware that the transfer functions you have for the two filters were almost certainly developed for those filters driven from particular source impedances, and operating into particular load impedances. Generally those are resistive sources and loads. When you cascade passive reflective filters (e.g. LC ladder filters), the first filter no longer "sees" a pure load resistance, and the second filter no longer "sees" a pure source resistance.
These days, it's convenient to use computer simulations for filter evaluation. There are several good programs specifically devoted to filters of various types, and Spice (e.g. LTSpice) can do a reasonable job with most filters.
Cheers, Tom
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