Use of load modulation for interference control between primary and secondary systems

Controlling interference from the secondary system to the receiver of the primary system is important issues when the secondary system uses the same frequency band in the area of television broadcast system. The reason includes that the secondary system cannot know the interference channel to the primary receiver, which does not have a transmitter. In this paper, we propose the interference control method between primary receiver and secondary system, where a load modulation scheme is introduced to the primary receiver. In this method, the signal from the transmitter station is scattered by switching load impedance at the primary receiver. Also, the secondary system estimates the reflected wave from receiver and estimates the interference suppression weights. Based on the simulation, it is shown that the proposed method is effective in controlling interference between primary receiver and secondary system.