The modulation signals are sent through coaxial cables. The shield of the coaxial cable connects the modulator ground and the V- of the modulation signal.

Excuse, I still confuse why the signal has to be grounded.

Thank you.

Richie

The signal does not have to be grounded. The shield has to be grounded at the source and the destination.

 

The signal does not have to be grounded. The shield has to be grounded at the source and the destination.

Since shield is connected with one end of the signal, if shield is grounded, then the signal is grounded. Is the correct?

Why the shield has to be grounded both at the source and the destination?

Richie

 

Since shield is connected with one end of the signal, if shield is grounded, then the signal is grounded. Is the correct?

Why the shield has to be grounded both at the source and the destination?

Richie

Current must travel from the source to the destination and back. A complete circuit is required for this. If you don't have a return current path through the shield, how is the signal current going to get back to the source?

 

Current must travel from the source to the destination and back. A complete circuit is required for this. If you don't have a return current path through the shield, how is the signal current going to get back to the source?

The current can flow back through the shield. Why the shield needs to be connected with the ground?

 

The current can flow back through the shield. Why the shield needs to be connected with the ground?

What do you think it should be connected to?

 

What do you think it should be connected to?

The shield at target end is connected with ground. That sounds enough for me.

Why the shield at DAC part should also be connected with ground?

 

The shield at target end is connected with ground. That sounds enough for me.

Why the shield at DAC part should also be connected with ground?

The shield is not just a shield. It is an essential part of the transmission line. If the shield is not grounded, the signal current must return to the source through some other path. This will result in high frequency attenuation and/or reflections, which will make high frequency data on the line unintelligible.
There are lots of books and articles available where you can learn about transmission lines. I'm not going to try to teach you here.

 

The shield is not just a shield. It is an essential part of the transmission line. If the shield is not grounded, the signal current must return to the source through some other path. This will result in high frequency attenuation and/or reflections, which will make high frequency data on the line unintelligible.
There are lots of books and articles available where you can learn about transmission lines. I'm not going to try to teach you here.

Thanks for your reply.

Could you please check the diagram below?
The shield is connecting with signal source and the target ground. There is a current path flowing back even though the shield is not connected with ground.


Richie

 

Thanks for your reply.

Could you please check the diagram below?
The shield is connecting with signal source and the target ground. There is a current path flowing back even though the shield is not connected with ground.


Richie

I didn't notice that you were talking about the DAC side in post #26. I have been talking about the RF signal since post #17.

 

I didn't notice that you were talking about the DAC side in post #26. I have been talking about the RF signal since post #17.

Thank you Ron H. You are very patient!

Thanks for your help! ^^

Richie