ABSTRACT: Design, Verification, and Troubleshooting of radar and communication systems often involves examining their up and downconverters. For example, if the overall system is exhibiting bit errors, or radar target returns are being masked by noise, what is the root cause? Loop back bit error rate (BER) testing may highlight the problem, but is the issue in the transmit or the receive chain and, when that has been determined, which part of the chain is the root cause?