very tiny slit on the transmission line

[shanmei]

If there is a very tiny slit on the transmission line, which breaks the connection. Whether RF signal still transfer througth the slit? Thanks.

 

[SLK001]

I'm assuming that the slit is directly across the TL. What that does is place a small capacitor in series with the TL. Most likely, some RF will get through - the amount depends on the circuit. To test this out, use the Smith Chart and introduce a small -j to a TL and see where the TL ends up.

 

[vfone]

Most likely the RF signal will be attenuated few tens of dBs, at least.

 

[shanmei]

Thanks.

If the feedlines are very tiny, then capacitance formed by the slit is very small beacuse of the small diameter of the feedlines. They it would attenuate the signal a lot.

 

[ge]

I can tell you from experience... RF will leak. My experience was semi-rigid coax that had a stress fracture.

 

[biff44]

well....a coaxial cable workes because the outer shield is a relatively solid piece of metal, and forms a faraday cage around the internal RF. In other words, there is RF energy on the INSIDE surface of the coax shield, but after a few skin depths there is no longer any RF current flowing in the shield metal. This by the time you reach the OUTSIDE surface of the coax shield, the RF energy is way down...maybe 100 dB lower.

So now put a slit in that shield. So the RF current has to hit the slit, and go around it to continue on down the cable. When it hits the slit, SOME of the RF current can now ride up the slit edge, and end up on the shield OUTSIDE surface. Once it is on the outside surface...it radiates into the air like an antenna would.