Covert Photonics-Enabled Millimeter-Wave Transmitter

Military communications are at a high risk of interception and detection and operate in regions with intentional jamming. Covert communication systems can reduce the probability of intercept and detection and increase robustness against jamming by employing spread-spectrum waveforms. To observers, a spread-spectrum signal appears as random noise, whereas to intended users the data can be recovered by using a shared key. Since spread-spectrum signals require large bandwidths, millimeter-wave (mmW) frequencies offer ideal bands for operation. Long-distance covert communications can use the W-band (75–110 GHz) and efficiently employing spread-spectrum signals at W-band is the focus of this paper. Specifically, our work uses photonic components in the analog front end of a transmitter to communicate covertly in the W-band. In this manner, high bandwidth, low-loss photonic components replace performance-limited RF components. The end result is a photonics-enabled spread-spectrum W-band transmitter demonstrated at 83 GHz and spreading the signal over a 4 GHz bandwidth.