A Fully-Connected Time-Modulated Phased-Array Transmitter Featuring Physical Security Directional Link and Multi-Beam PAPR Reduction

Phased-array techniques have been widely used in wireless and satellite communications. To maximize the communication capacity, multi-beam phased-array architectures have drawn more attention in recent years, which enable simultaneous communication with multiple independent users at different locations [1–2]. A conventional fully-connected topology of the 4-element 4-beam phased-array transmitter (TX) is shown in Fig. 1. The fully-connected phased arrays faces two challenges. First, for each beam of the multi-beam system, the same modulated signal is fed to all the TX elements, transmitting the same information to all directions with different power levels. This information can be demodulated with a sensitive enough eavesdropper receiver (RX). This may lead to the risk of information leakage. Second, one of the key components for a communication TX front-end (FE) is a power amplifier (PA) with relatively high output power and enhanced power-added efficiency (PAE) at both saturated output power (Psat) and power back-off (PBO) levels. The peak-to-average ratio (PAPR) of a modulated signal of $16-Q A M$ is approximately 5.6 dB. For a multi-beam system, when multi-beams operate at the same time, the PA faces an increased PAPR, 8.6dB for 2-beam and 14.6 for 8-beam for example, therefore further deep PBO levels are required, which reduces the overall efficiency and output power of the whole system.