Fig. 3. Calibration philosophy for proposed methodology: (a) SMC + phase reference/measurement calibration setup; (b) Scalar calibration setup; (c) EVM calibration setup; (d) Phase calibration setup using TLT. is carried out from the DUT downlink switch matrix path to the spectrum analyzer path using an expected stimulus. Fig. 3c shows the setup for EVM calibration. This calibration refers to step-c. Scalar and Phase Calibration using Test Loop Translator (TLT): Multibeam payloads typically consist of 20 uplink and downlink paths. The time required for a system operating from 10-15 GHz generally is 20 minutes per path for measurement channel calibration, 45 minutes for one-time phase reference calibration and 5 minutes for EVM calibration per path. October 2022 Therefore, the total time required is around 545 minutes, i.e., approximately 9 hours. Calibration time significantly contributes to ATE throughput, so we explored various options without compromising measurement uncertainty. In ATE, there are no frequency-selective components; hence, there is no need to carry out measurement channel calibration up to switch matrix nodes, and only scalar calibration from SINE common port to switch matrix node is sufficient. Phase calibration up to the DUT node is primarily required for phase-related relative measurements like group delay and AM/PM conversion/transfer coefficients, which do not IEEE Instrumentation & Measurement Magazine 41