A means for scrambling the digital modulation content in the sidelobes of a radio transmission from a steerable antenna array is presented. The method uses a Fourier transform beam-forming network simultaneously excited by an RF information stream and orthogonally injected interference streams. The proposed system is implemented using a Fourier Rotman lens and its operational characteristics are validated for a 10 GHz QPSK transmission.
Zhang, Y., Ding, Y., & Fusco, V. (2013). Sidelobe modulation scrambling transmitter using Fourier Rotman lens. IEEE Transactions on Antennas and Propagation, 61(7), 3900-3904. https://doi.org/10.1109/TAP.2013.2254453