SN74CBTLV3251: waveform distortion

The SN74CBTLV3251 has a specified bandwidth of 200 MHz. The attenuation in figure 2 happens already at 60 MHz, so I guess there are additional resistances and capacitances in the circuit. Are there any long traces, cables, or connectors? Please show the schematic and the board.

HI Clemens Ladisch 

Here is my block diagram.We still confuse why the signal pass the switch will distortion at 60 MHz??

Please specify the characteristics of the cables, and the termination (if any).

www.keysight.com/.../passive-probe-10-1-500-mhz-1-3-m.html

The probes are probably OK. How are the DUT and the SN74CBTLV3251 connected?

Use Dupont Line connect DUT and SN74CBTLV3251 

Hey Calvin,

I'm merging from this thread : https://e2e.ti.com/support/switches-multiplexers-group/switches-multiplexers/f/switches-multiplexers-forum/1287379/sn74cbtlv3251-signal-pass-the-switch-ic-will-be-distortion

Nothing here really stands out as the root cause but can you clarify on your waveforms what each wave represents.
Is yellow bypassing the mux and green through the mux? it looks like your signal integrity drops at 60MHz even without the mux while the 60MHz signal through the mux does have more of a drop probably due to the extra capacitance. What's the DUT and what's the capacitance there? I see your probes are 9.5pF. 
Additionally what do the board traces look like? Are they particularly long or thick? 
Do you have another source you can use for debugging here besides the DUT?

Thanks,
Rami

1.

Figure 1: 30MHz

Yellow (Probe1):Controller output

Green (Probe2): Output after SN74CBTLV3251PWR

Figure 2: 60MHz

Yellow (Probe1):Controller output

Green (Probe2): Output after SN74CBTLV3251PWR

2.

DUT (device under test) is the output terminal of the IC controller.

3.

The switch IC sample look like the figure below

4.

We have also tried to use the Function generator to directly pass the output signal.

The measurement results are as shown below :

Hello Jeff,

For such high frequencies application, using DuPont wires is not recommended since they have high parasitic capacitance that will cause distortions in the signal.  

Could you please provide a picture of your setup with everything connected? 

Your issue could be related to parasitic distortions or noise.

Thanks,

Nir