A radio frequency (RF) loopback substrate or printed circuit board (PCB) which contains receive and transmit antennas located on the bottom of the loopback substrate which are aligned with the complementary transmit and receive antennas on an antenna on package (AOP) device under test. The loopback substrate receive and transmit antennas are coupled to each other. The device under test contacts are driven by a conventional tester, which causes RF circuitry in the integrated circuit to drive an AOP transmit antenna. The corresponding loopback substrate receive antenna receives the RF signal from the AOP transmit antenna and provides it to the loopback substrate transmit antennas. The integrated circuit package AOP receive antennas then receive the RF signals from the loopback substrate transmit antennas. The signals at the integrated circuit package AOP receive antennas are monitored through the integrated circuit contacts to monitor the received RF signals.