Photonic microwave-to-digital subsystems: When, why and how

The accurate collection and assessment of information contained in the electromagnetic (EM) environment is crucial to the success of a variety of avionic systems. The nature of the information to be collected and platform demanding multi-functionality requires these systems to simultaneously cover many RF and microwave bands and to deliver accurate (post-processed) information. Additionally, the increasing demands for higher system performance and increased versatility result in the reliance on digital signal processing (DSP) and consequently the high fidelity conversion of the analog microwave input signals to digital representations. In this paper, we seek to classify input waveforms representing the key classes of analog signals and identify desired output information classes. We will also provide guidance for matching recently demonstrated photonic microwave-to-digital architectures to the input waveform/output time-spectra reconstruction scenarios. In addition, we will cover the performance parameters and the crucial microwave-optical-electrical-digital interface issues.