An apparatus includes an electrical connector. The electrical connector is configured to electrically couple a signal transmission line to another signal transmission line. The electrical connector includes a first electrical conductor and a second electrical conductor. The first electrical conductor is disposed around a center axis. The first electrical conductor is disposed azimuthally symmetric around the center axis. The second electrical conductor is disposed around the center axis and around the first electrical conductor. The second electrical conductor is disposed azimuthally symmetric around the center axis. Faces on opposing ends of the electrical connector along the center axis are configured to mate the signal transmission line and the second electrical conductor in a first plane and the other signal transmission line and the second electrical conductor in a second plane.