Radiation Pattern Inspection of the FMCW Signal Using Asynchronous Electro-Optic Measurement System

Abstract

We propose and demonstrate a new measurement technique for the radiation pattern inspection of the Frequency Modulated Continuous Wave (FMCW) signal. The proposed measurement system makes it possible to measure FMCW signal based on a photonic frequency tracking in asynchronous electro-optic measurement system. The radiation pattern of the FMCW signal measured by our new system is the average value of the radiation patterns of all the CW signals in the signal bandwidth. We measured a radiation pattern of a FMCW signal at quasi-millimeter wave band $(24 \text{GHz} \pm 80 \text{MHz})$ and compared it with the radiation pattern of a monotonous signal at 24 GHz. We confirmed deviation between the radiation pattern of the FMCW signal and that of the CW signal when we place a vehicle emblem in front of the horn antenna. The proposed technique is considered to be useful when measuring the signal with the larger frequency deviation width at the millimeter-wave band such as an FMCW radar of 79 GHz with a fractional bandwidth of 5%.