A connector interface provides high-frequency differential connection to a balanced cable or balanced electronic device, such as a balanced probe. The connector interface includes two coaxial structures in a single connector. When the connector interface is used in a package launch, the closeness of the center pins of the two coaxial structures facilitate connection to a balanced circuit. When used in conjunction with a balanced vector network analyzer, the connector interface can simplify calibration and testing of devices by reducing the number of connections to the calibration standards or devices being tested, and provide improved measurement accuracy.