Multiparameter Measurement of Microwave Signals Based on Optical Real–Time Fourier Transform

Multiparameter measurement of microwave signals is proposed and experimentally demonstrated based on a two–channel optical real–time Fourier transform (RTFT) system. The system can simultaneously measure the frequency, amplitude, pulse width (PW), and time of arrival (TOA) of microwave signals over a wide frequency range, while also enabling identification of intra–pulse modulation formats. The design implements frequency–to–time mapping with complementary dispersion and phase–to–amplitude mapping with two-channel interference. The signal under test (SUT) is split into two branches, with an appropriate time delay in one branch, then jointly drive a polarization–division–multiplexed Mach–Zehnder modulator (PDM–MZM) to generate two channel optical signals with orthogonal polarization. The frequency and amplitude of the SUT are obtained through frequency-to-time mapping in an independent channel, while the relative phase and modulation format are extracted from the interference between the two channels. In the proof–of–concept experiment, multiparameter measurements of microwave signals over a frequency range of 2–25 GHz are achieved, with a measurement error for frequency, amplitude, phase, PW, and TOA within ±91 MHz, ±40 mV, ±4.9°, 21 ns, and 20 ns. Based on envelope analysis of two–channel interference pulses across multiple mapping windows, the system clearly distinguishes and demodulates continuous wave (CW), binary phase shift keying (BPSK), and linearly frequency–modulated (LFM) signals that are difficult to identify by a single–channel RTFT system.