Research On The Design Of The High Scanning Rate Composite Right/Left-Handed Leaky-Wave Antennas

In recent years,the beam-scanning leaky-wave antennas(LWAs)with frequency control have gained significant attention in many fields such as Imaging,Internet of Things,and automotive radar,due to their advantages of low cost,low profile,easy integration,and simple feeding.Since a Composite Right/Left-Handed transmission line(CRLH-TL)can support not only the forward wave(? > 0),but the backward wave(? < 0)in different frequency ranges,a balanced CRLH is utilized to design LWA without an open stopband(OSB)phenomenon.Recently,the scanning rate of the beam-scanning antennas has risen greatly interesting in the antenna community with the increasingly spectrum congested environment.In this article,a novel method to improve the scanning rate of CRLH LWA is proposed.The design of this article is organized as follows.1.A novel topology model for tuning the CRLH dispersion characteristic is proposed.The traditional CRLH model reveals that both the unit cell size and the losses will be increased with a further improvement of the LWA scanning rate.The novel topology model is formed by introducing an additional T-type network into the symmetric center of the traditional CRLH equivalent circuit topology.Hence,the dispersion characteristic of the novel topology can be manipulated by the extra T-type network while remaining the series impedance and shunt admittance constant.This explains that the unit cell can achieve a narrow dispersion bandwidth while keeping the unit cell size constant.2.A novel CRLH LWA with high scanning rate is designed.Based on the novel topology,a novel CRLH unit cell with a narrow dispersion characteristic is proposed,which equivalent circuit is subsequently extracted with the microstrip theory.After optimization using HFSS,the dispersive bandwidth of the unit cell is 9.3 10.65 GHz,and the transmission frequency is10.05 GHz.Then,a CRLH LWA is design with 9 proposed unit cells to be operated in the desired frequency band.The simulated and measured results show that the prototype can achieve a seamless beam scanning from-68° to +70° within 9.3 GHz to 10.65 GHz(i.e.,13% for fractional bandwidth)and a high scanning rate of 10.62.The measured gain is 6.99 10.4d Bi.3.Another novel ultra-high-scanning-rate CRLH LWA is presented.Another novel CRLH unit cell with ultra-narrow dispersion characteristic is proposed based on the novel topology.Firstly,the relationship between the novel model and traditional model is explained by a practically design comparison between CRLH unit cells.Then,the equivalent circuit of the novel unit cell is extracted.The dispersion characteristics of both unit cell and equivalent circuit simulation show that the operating frequency is 9.25 GHz to 9.92 GHz,and the transmission frequency is 9.62 GHz.The CRLH LWA is designed with 9 proposed unit cells.And the simulated and measured results of the antenna prototype show that the LWA can achieve a seamless beam scanning from-65° to +65° within 9.3 GHz to 9.93 GHz(i.e.,6.6% for fractional bandwidth)and an ultra-high scanning rate of 19.7,i.e.,the main beam can scan 19.7° within1% fractional bandwidth.