Wideband Microwave Vector Network Analyzer Based on Photonic Harmonic Mixing

We present a wideband microwave vector network analyzer (VNA) based on photonic harmonic mixing (PHM) that can relax the demand for electrical equipment, such as bandwidth and sample rate. A single-tone radio frequency (RF) signal serves as the incident signal of the device under test (DUT). The response signal of the DUT is modulated on the optical harmonics, which is generated by modulating the local oscillation (LO) microwave signal on a continuous wave (CW) light. After beating the modulated optical harmonics at the photodetector (PD), the response signal of the DUT is down-converted to an intermediate frequency (IF) signal. The DUT’s scattering parameters (
$S$
parameters) at this frequency can be obtained from the IF signal. Then by synchronous frequency sweeping of LO and RF signal with IF frequency fixed, the scattering parameters (
$S$
parameters) within a frequency range are acquired. Experiments are demonstrated, in which the
$S$
parameters of a 15-GHz low-pass filter (LPF) within 2.2–20.2 GHz is measured. And by employing higher order harmonics, the extension of measurable frequency range 4.2–40 GHz is achieved. The dynamic range (DR) of the proposed scheme exceeds 63 dB at an equivalent resolution bandwidth (RBW) of 16 kHz. The limit factors of the DR are discussed. The developed method offers a microwave photonic way for the researches of wideband and high DR microwave VNAs.