Phase Noise Analysis of Photonic Radar Systems with Optical LO Distribution

Photonic radar systems with optical local oscillator (LO) distribution have the potential to increase the angular resolution in multiple-input multiple-output (MIMO) imaging radars. In single-input single-output (SISO) radar systems, phase noise increases the occupied intermediate frequency (IF) bandwidth around strong targets, which makes it hard to detect weak targets nearby. This effect is even more critical in imaging MIMO systems since the uncorrelated phase noise sources increases the noise floor of the overall system. Within this work the phase noise characteristic of a photonic radar system with optical LO distribution is analyzed mathematically. Since the same optical LO signal is distributed to each transceiver (TRX) frontend, the focus of this work lies on the amplitude modulation (AM) to phase modulation (PM) conversion due to the electrooptical (EO) and optoelectronic (OE) conversion. Within this work it will be shown, that due to these conversions, baseband (BB) amplitude noise will be converted into bandpass (BP) phase noise around the desired LO carrier.