Photonic-assisted fast broadband microwave vector network analyzer based on FMCW

Area of Science:

• Photonics
• Microwave Engineering
• Network Analysis

Background:

• Traditional vector network analyzers (VNAs) face limitations in speed and bandwidth for characterizing complex microwave devices.
• Frequency Modulated Continuous Wave (FMCW) techniques offer potential for broadband measurements but require sophisticated implementation.
• Photonic approaches can overcome electronic bottlenecks in high-frequency signal generation and processing.

Purpose of the Study:

• To propose and demonstrate a photonic-assisted fast broadband microwave vector network analyzer (FB-VNA).
• To achieve extended measurement bandwidth and accelerated measurement speed for microwave devices.
• To enable the characterization of rapid transient changes in device parameters.

Main Methods:

• Utilizing a photonic recirculating frequency shift (RFS) loop to extend the bandwidth of optical FMCW.
• Generating broadband electrical FMCW signals by beating optical FMCW with continuous wave (CW) light.
• Employing de-chirping on the device under test (DUT) response signals modulated on the extended optical FMCW.
• Down-converting broadband response signals to a single-tone intermediate frequency (IF) signal for simplified electrical backend processing.

Main Results:

• Experimental implementation achieved a bandwidth multiplication of FMCW from 6-18 GHz to 6-498 GHz.
• A 6-54 GHz FB-VNA was demonstrated, measuring S-parameters of a 25-GHz low-pass filter (LPF) in 6 μs.
• The system successfully captured sudden parameter changes as short as 0.01 μs.

Conclusions:

• The proposed photonic-assisted FB-VNA significantly extends measurement frequency range and accelerates measurement speed.
• The single-tone IF output simplifies the electrical backend requirements.
• The FB-VNA is suitable for monitoring fast dynamic changes in microwave devices.