(1) solid insulated cable
Between the inner and outer conductors of this cable, all of them are filled with solid high frequency dielectric, and most flexible coaxial RF cables adopt this type of insulation.
(2) air insulated cable
In the insulating layer of the cable, the bulk of the volume is air except for a part of the solid medium that supports the inner and outer conductors. The structure is characterized by that one conductor to another conductor can not pass through the dielectric layer. Air insulated cables have very low attenuation, and they are often used in ultra high frequency.
(3) half air insulated cable
This type of structure is an insulating type between the above two, and its insulation is also composed of air and solid medium. But from one conductor to another, it needs to pass through the solid dielectric layer.