Microwave Phase Noise Analyzer Based on Photonic Delay-Matched Frequency Translation

A wideband and high-sensitivity microwave phase noise measurement approach is proposed and experimentally demonstrated based on photonic delay-matched frequency translation. In this scheme, the signal under test (SUT) is down-converted to a lower intermediate frequency (IF) signal using a local oscillator (LO) signal, effectively extending the operation bandwidth beyond the limitations imposed by electrical devices. Additionally, the residual phase noise introduced by the LO signal can be effectively suppressed by matching the time delays of the two down-conversion branches, thus eliminating the need for a high-performance reference source. Consequently, the proposed phase noise measurement technique offers a large operation bandwidth and high sensitivity compared to traditional frequency-discriminator-based method. Our experimental results demonstrate accurate phase noise measurement of SUTs within a large operation bandwidth ranging from 10 to 40 GHz. A high measurement sensitivity of −134.13 dBc/Hz@10 kHz is achieved with a 2-km single-mode fiber, which can be further enhanced by applying a longer fiber. In summary, our proposed approach presents a promising solution for evaluating wideband tunable and ultralow phase noise microwave signals.