Overview on the Phase Conjugation Techniques of the Retrodirective Array

Table 2

Comparison of the major phase conjugation techniques.

Phase conjugation technique		Advantages	Disadvantages	Applications
heterodyne technique	using LO at 2𝑓RF	flexible structure, easily realized	high LO frequency, poor RF-IF isolation	simplex communication, RFID
	using IF		existing interference	full-duplex communication, wireless sonar, and radar
phase detection and PLL		better conversion gain and efficiency, high power carrier	more complex and expensive	full-duplex communication, point to point wireless application
digital technique		high link gain, flexible structure, and multifunction	more expensive	duplex digital communication