Photonic-assisted microwave frequency measurement with small time delay

A novel configuration for photonic-assisted instantaneous microwave frequency measurement is proposed. Different from the previous works, we employ the Mach-Zehnder interferometer (MZI) instead of long dispersive medium to get the transmission response related with the unknown microwave frequency, which can greatly enhance the response speed of the measurement system. The optical source is firstly modulated by the unknown microwave signal to be measured, and then the output signal from the Mach-Zehnder modulator (MZM) is divided into two branches and sent to the MZIs with different time delays, respectively. After detection by the photodetector, a unique relationship between the microwave power ratio function and the input microwave frequency can be established, from which we can estimate the unknown microwave frequency. This proposed configuration has been experimentally verified with the measurement range from 5 to 10 GHz and the measurement errors less than 0.3GHz.