I'm designing an automotive circuit where I'm using a reference power design from TI. Together with protection circuitry, this design includes a common mode choke.
The same circuit has an antenna input, and this antenna is grounded to the car chassis. This means that the circuit has two ground connections when the antenna is connected.
My understanding of a common mode choke is that it only works as expected when the same amount of current flows in each direction of the choke. (correct me if I'm wrong)
I'm then wondering how this second ground connection through the antenna cable will impact the performance of the common mode choke? Can it still be used?
update: Added schematics. The output of the choke goes to a TI LM53601 switching regulator and a TI TPS7B7701 antenna LDO for supplying phantom power to the antenna. IN GND and GND are separate nets. GND is also the ground connection for the antenna.
All the antennas I've investigated have 0 ohm resistance between the fixture that connects the antenna to the car and the shield around the antenna signal (inside the cable). Example of one such antenna is the Antennensysteme 3785.01 as shown below. When tightened to the car roof, the antenna will certainly be grounded to the chassis.