Fig. 1. Generic automated test system (ATS) architecture. Calibration Philosophy Network Analyzer Calibration: This refers to the calibration of the network analyzer for frequency converting DUTs and is also known as continuous wave (CW) calibration. The proposed calibration philosophy used is based on Scalar Mixer Converter (SMC) + Phase method. The method accurately calibrates amplitude/ power and phase over the broader frequency range (using a comb generator). The method does not require access to LO of DUT, which makes it most suitable for frequency converting DUTs like satellite transponders. This calibration refers to step-a, as shown in Fig. 3a. The calibration is divided into three parts: ◗ Phase Reference Calibration: The phase reference calibration provides the highest accuracy phase measurement, sweep-to-sweep stable and jitter-free results for mixer/ converter DUTs. A reference or calibration mixer is not required. The phase reference is a comb generator, which produces signals at the multiple of 10 MHz using VNA's 10 MHz reference output with a flat phase response. During calibration, VNA's Port-2 'B' receiver measures the phase at each 10 MHz comb frequency to generate correction values [17]. A phase reference calset file stores these values, which can be recalled and applied to correct subsequent SMC + phase measurements. The approach's advantages include non-requirement of reference/calibration mixer, providing calibration over full/user frequency range of VNA or phase reference. ◗ Measurement Channel Calibration: In this calibration, we create four channels inside VNA to facilitate various parametric measurements as listed below: ⦁ SMC + Phase: Two such channels are created for gain transfer curve measurements and frequency response/group delay characteristics of DUT. ⦁ IDX: This channel is for determining the third-order intermodulation distortion of DUT. ⦁ NFX: This channel is for determining the noise figure of DUT. Fig. 2. Setup of developed ATS. 40 ◗ EVM Calibration: This refers to the calibration for measurement of RF modulation related parameters such as EVM (Error vector magnitude), MER (modulation error ratio) etc. and is known as modulated parametric calibration. It IEEE Instrumentation & Measurement Magazine October 2022