Square signals monitoring

[Vlad.]

Hi,

I want to view an square signal generated by an FPGA at 7 meters away by using oscilloscope. I had used 50 ohm coaxial cable, RG178, and also I terminated the cable at the end using 50 OHM inputs terminations of the oscilloscope. My question is regarding my method, if it ok to use it, or should I terminate the signal near FPGA and at the end the cable I should catch the wave with high impedance inputs of the oscilloscope.

cheers,
Vlad

 

[FvM]

You didn't mention signal level, frequency, required signal quality (e.g. acceptable reflection factor). Also driver output current rating must be considered.

I would use 50 ohm source side series termination and high impedance load if sufficient for required signal quality. For highest quality requirements or very high frequencies use double source and load termination. The FPGA side must be able to drive 100 ohm effective load in this case.

 

[Vlad.]

Hi,

The level will be between 1.8 V and 3.3 V and the frequency will vary between 1.7 and 12 MHz. The FPGA can drive a 50 ohm load.
About the signal quality, I need it to be good enough to highlight some of its parameters (duty cycle, frequency, rise time, fall time).

Many thanks for your answer.

Cheers,Vlad