Hi there,
I intend to use the ADG902 switch for backscattering applications, with a control signal pulse of 50 MHz. The time domain response of the switch in the forward direction is shown below:
which matches the figure in the datasheet (ignore the blue RF signal, only the red envelope is meaningful in this figure). However, when I looked at the return signal in the same experiment, I got this result:
which shows clearly some heavy distortions. Such distortions happen for lower frequency of switching too. For instance, for a 10 MHz pulse the result is shown below in (d):
,but at lower frequency the distortions are less important as the period of the pulse becomes larger.
So in general, I'm wondering why such distortion is happening. Can we have a simplified model of the internal circuit?
I understand that usually the return signal is not important for many applications, but for my application this is especially important (the applications is a backscattering wireless node).
Also in general, similar switches (eg HMC194) also seems not to work at such high frequency of switching (50 MHz). What determines the highest frequency of switching for a switch? I don't think this data is available anywhere in the datasheet.
Any help would be much appreciated!
Update (Nov 22, 2018): To clarify, a schematic for my test setup is shown below:
I'm using a circulator to collect the return signal. In this setup, the switch is alternating between on and off every 20 ns, so exactly one half of the period of the RF signal should be in the through signal and one half should be in the return signal.
Added a schematic of the test setup
[edited by: Navid_rz at 3:25 PM (GMT -5) on 22 Nov 2018]