Coaxial coupling systems and methods couple a first coaxial cable that includes a first inner conductor and first shield conductor to a second coaxial cable that includes a second inner conductor and a second shield conductor, through an insulator that includes first and second insulator surfaces. A first center plate and a first surrounding plate are adapted for attachment to the first insulator surface such that the first surrounding plate surrounds the first center plate on the first insulator surface. The first center plate is electrically connected to the first inner conductor and the first surrounding plate is electrically connected to the first shield conductor. A second center plate and a second surrounding plate are adapted for attachment to the second insulator surface such that the second surrounding plate surrounds the second center plate on the second insulator surface, the first and second center plates are adjacent one another with the insulator therebetween and the first and second surrounding plates are adjacent one another and the insulator therebetween. The second center plate is electrically connected to the second inner conductor and the second surrounding plate is electrically connected to the second shield conductor. The coaxial coupling systems and methods can allow communication signals to pass with low insertion loss, over a desired frequency range, between an antenna mounted outside a window and a radio transceiver mounted inside the window. Transmission takes place via a coaxial transmission line on each side of the window.