I. Introduction
We have already developed a bi-directional type optical fiber link system for vector network analyzer (VNA) up to 6 GHz [1][2]. Our proposed system Our proposed system consists of two bi-directional optical fiber link transceivers with microwave directional coupler for antenna under test, two bi-directional optical fiber link transceivers for VNA and two single mode optical fibers. Our system can measure s-parameter in full 2-port calibration. For calibrating antenna gain, we usually use 3-antenna extrapolation technique [3] with accurate measurement condition. For this reason, we evaluate our proposed system performance for antenna transmission coefficient and transmission coefficient measurement.