Research And Design Of Active Intelligent Reflecting Surface

Traditional wireless communication systems consist of a transmitter and a receiver,with the transmitter sending electromagnetic waves carrying information through an uncontrollable propagation environment to the receiver.In exploring the architecture of5 G networks,researchers have proposed the use of intelligent reflecting surfaces(IRS)to achieve a reconfigurable propagation environment.The main idea is to transmit the signal received by the IRS to the destination in a beamforming manner to support transmission from the source to the destination.However,the practical application of IRS still faces some challenges,one of which is the dual-path attenuation experienced by the signal in the source and destination links in the IRS-assisted communication system.The gain provided by the passive IRS is limited by the size of the reflecting surface,so introducing active amplifiers to improve the gain performance of the IRS system has broad development prospects.This paper proposes a scheme of combining a single port reflection amplifier with a traditional antenna array to form an active IRS system,which can bring active gain while simultaneously having the reciprocity of signal transmission,and can more effectively improve the efficiency of the IRS system.It has great application prospects in expanding the coverage of base stations and solving non line of sight communications.This article combines theoretical analysis,simulation,and testing verification to ultimately achieve an active IRS system and test its active gain,verifying the feasibility of the active IRS scheme.The proposed quasi-ring resonator reflection amplifier has two different receive/retransmit signal paths,integrated with a reconfigurable phase shifter,and has the ability to reconfigure receive and reflect signals arbitrarily.By designing a quasi-ring resonator with excellent isolation characteristics and a broadband matching,narrowband gain amplifier,this article has designed,processed,and tested a reflection amplifier that works in the commercial 5G communication frequency band(3.5 GHz)in China,with a working bandwidth of 200 MHz and a linear gain of 15 d B.To enable the IRS system to obtain higher active gain,this article proposes a design scheme for an orthogonal polarized antenna unit based on the open-loop resonator structure of orthogonal feedback.The design achieves a bandwidth of 110 MHz with a return loss better than-20 d B,maintains excellent performance in ± 15° incident direction,and ensures good polarization isolation and radiation efficiency of the antenna unit.This paper proposes two active intelligent reflecting surface(IRS)design schemes:centralized amplification and distributed amplification,and conducts in-depth studies on them respectively.The proposed centralized amplification active IRS system combines an 8x8 feeding network,antenna array,and reflection amplifier to form an active IRS system,where both the incident beam and reflected beam are fixed at a direction of 0°.The test results show that the centralized amplification active IRS system generates a reflection gain of 53 d B at 3.45 GHz,with an active amplification gain of 14 d B.In the proposed distributed amplification active IRS system,a reflection amplifier is configured in each unit of the 4x4 antenna array.The test results show that the distributed amplification active IRS system achieves the mirror reflection characteristic of the signal and generates a reflection gain of 49 d B at an incident beam direction of 0°,with an active gain of 9 d B.