Complex amplitude estimation of a monochromatic radio-frequency signal using frequency downconversion via direct detection of interfered optical phase-modulation signals

We propose an estimation scheme for a radio-frequency (RF) signal based on microwave and millimeter-wave photonics to avoid degradation of measurement accuracy due to RF devices used in signal detection. In this scheme, two-parallel optical phase modulation and low-pass optical direct detection of the interference signal are utilized, enabling the transfer of complex amplitudes of the RF signal into the interfered lightwave. A 10 GHz RF signal is successfully evaluated from the 20 kHz oscillation signal obtained from the direct detection. This scheme can be applied to signals in the millimeter-wave region because it does not require wide bandwidth detection and optical-domain filtering by using a special optical filter. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement