Low-probability of Intercept/Detect (LPI/LPD) Secure Communications Using Antenna Arrays Employing Rapid Sidelobe Time Modulation

TL;DR

This paper introduces a reconfigurable antenna array that employs rapid sidelobe time modulation to enhance secure communications by making signals in undesired directions difficult to detect or intercept, without requiring additional encryption.

Contribution

The paper presents a novel antenna array design that uses rapid sidelobe time modulation to achieve low probability of intercept/detect and secure communications at the physical layer.

Findings

Validated spread-spectrum SLTM sequence generation through theory, simulations, and experiments.

Demonstrated LPI/LPD and jamming resilience with a fabricated prototype at X band.

Showed that the technique can be integrated into existing systems by replacing antennas.

Abstract

We present an electronically-reconfigurable antenna array offering low probability of intercept/detect (LPI/LPD) and secure communications capabilities simultaneously at the physical layer. This antenna array is designed to provide rapidly time-varying sidelobes and a stationary main lobe. By performing rapid sidelobe time modulation (SLTM), the signal transmitted in the undesired directions (i.e., through sidelobes) undergoes spread-spectrum distortion making it more difficult to be detected, intercepted, and deciphered while the signal transmitted in the desired direction (i.e., through the main lobe) is unaffected. Therefore, the intended receiver would not need additional modifications (i.e. encryption keys) to detect and recover the signal. We describe the operating principles of this SLTM array and validate its spread-spectrum SLTM sequence generation in undesired directions through theory, simulations, and experiments. Using a fabricated SLTM prototype operating at X band, we conducted system-level measurements to demonstrate its LPI/LPD, secure communications, and jamming resilience capabilities. The presented method is a physical layer technique, which can bring LPI/LPD capabilities to existing communications systems by simply replacing their antennas with SLTM arrays. This technique can be used independently or in combination with additional coding and signal-processing techniques to achieve further enhancements in LPI/LPD and secure communications.