Photonic-Assisted Intrapulse Parameters Measurement of Complex Microwave Signals

Measurement on intra-pulse parameters of complex microwave signals within a wide frequency coverage is essential for radar and communication systems. In this paper, a photonic approach based on a dual-port Mach-Zehnder interferometer (MZI) configuration is proposed to measure the intra-pulse parameters of phase/frequency-coded microwave signals. In the proposed approach, a light wave is externally modulated by a complex signal to be measured under the carrier suppression mode, and then sent to the dual-port MZI to perform frequency-to-power mapping. The optical powers at the two outputs of the MZI are detected as two instantaneous amplitudes, such that an amplitude comparison function (ACF) directly associated with the instantaneous frequency is derived via a division between the two instantaneous amplitudes. Multiple intra-pulse parameters are then identified through temporal analysis of the instantaneous amplitude, ACF, and instantaneous frequency. Measurements to pulsed microwave signals with intra-pulse modulation formats, including phase-shift keying, frequency-shift keying, and linear frequency modulation, are described theoretically and demonstrated experimentally. In addition, the performance of the proposed approach in terms of the signal-to-noise ratio and the minimum power level is discussed.