Optical fiber link 1-pass 2-port antenna measurement system

We have proposed the optical fiber link antenna measurement system that can measure the calibrated S11 and S21 between two antennas under test (AUT) after OSLT calibration in one-pass two-port system. Our system consists of the transmitting and receiving optical-fiber link systems. The transmitting system consists of the electro-absorptive modulator, erbium doped fiber optical amplifier (EDFA), optical fiber, zero biased uni-traveling-carrier photodiode (UTC-PD), small type bi-directional coupler, and two optical reflection type Mach-Zehnder LiNbO₃ optical intensity modulators (LN-modulators) with 50 ohm loads. The system can detect the reflection signal from the transmitting AUT and the reference signal toward the AUT. The receiving system consists of an optical reflection type LN-modulator and the optical field measurement system, to measure the transmission signal through the receiving AUT. Our system can measure the reference signal, the reflection signal, and the transmission signal in one-pass two-port model between the two AUTs. Then OSLT calibration can be adopted. In this paper, in order to demonstrate the validity of our optical fiber link system, we compare the calibrated S11 and S21 results of two UHALP9108A 1 Log-periodic antennas by our proposed optical-fiber link system with the ones by the conventional coaxial cable system in frequency-domain and time-domain measurements. The results clearly indicate that our proposed system can be used to evaluate the S11 and S21 of the AUT at the frequency range from 300 MHz to 1800 MHz without coaxial cables.