Research On Leaky-wave Antenna And Array Based On Substrate Integrated Waveguide

Since the leaky-wave antenna(LWA)was proposed in the 1940 s,it has been one of the antenna research hotspots due to its good radiation directivity and frequency scanning ability.Leaky-wave antenna has been widely used in wireless communication systems,such as aircraft,high-resolution radars,and satellite ground station communications in motion.In the early 21 st century,substrate integrated waveguide(SIW)was proposed as a new type of guided wave structure,which integrates the advantages of traditional metal waveguide and planar guided wave structure,such as high power capacity,low profile and low cost.It is used in the design of various mircrowave elements and injects new vitality into the reseach of leaky-wave antennas.Based on the SIW structure,leaky-wave antennas and arrays are studied from the characteristics of high efficiency,high gain,beam-formed radiation pattern and fixed-frequecy beam steering,and a series of novel leaky-wave antennas for different applictions are designed in this paper.The main innovations of this paper are as follows:1.Based on the method of dual-mode hybrid radiation,a high-efficiency SIW leaky-wave antenna array with low side lobe level(SLL)and dual-beam generation is designed.This array is composed of a fundamental wave radiation antenna element and a-1st spatial harmonic radiation antenna element.By using the asymmetric power-recycling feeding stucture,it generates the characteristic of different beam radiations from different input ports.By design of Taylor distribution aperture field for each antenna element,the radiation patterns with low SLL are realized.From the results analysis of S-parameter,radiation pattern,gain and efficiency,and compared with other references,the proposed design is verified to be effective.2.A method to improve the radiation efficiency and realize the hign-gain LWA with power-recycling feeding network is proposed.To overcome the disadvantage of low radiation efficiency of LWA,the fundamental wave radiation antenna elements and the-1st spatial harmonic radiation antenna elements are alternately integrated on the same substrate to form the antenna array.Through the feeding structure of power-recycling network,the array not only realizes high efficiency and high gain,but also keeps the compact structure.According to this design principle,the antenna arrays with 3 and 5 elements are designed,fabricated and measured.The results show that,the radiation efficiency and gain of these antenna arrays with power-recycling feeding network are improved significantly.3.A method of superposing radiations from the-1st space harmonic beams in a weighting way to realize the beam-formed pattern is proposed,and a SIW beam-formed LWA array with periodic transverse slots is designed.Firstly,to get the optimized results of the superposed beams,the period,length and width of transverse slots for two antenna elements are designed respectively,which generates two wide beams with different beam directions and different radiation strengths.Then by superposing the two beams in a weighting way,a cosecant-squared-like pattern are formed finally.From the results and analysis of S-parameters,radiation patterns,gains and efficiencies,the feasibility and effectiveness of the beam-superposition pattern-shaping method is verified.4.By appling the method of beam-superposition of different periodic structures in a weighting way to design a LWA with cosine-shaped periodic slot,a SIW beam-formed LWA with a composite slot is proposed for the application of long straight confined space to achieve the uniform coverage.And a double-layer power recycling feeding netwok is used to design the antenna array to improve the radiation efficiency.The experiment results validate that,the combination of beam-superposition pattern shaping method and the power-recycling feeding network can realize the design of leaky-wave antenna with specific beam-formed radiation pattern.5.To realize the fixed-frequency beam-steering characteristic of LWA,a radiation pattern-reconfigurable LWA based on SIW structure is proposed.The waveguide has inner row and outer row of metallized vias on each side.Each via in the inner rows is connected to the ground plane and top wall through the PIN diode,which works as the binary switch.By setting the states of switches in a coding way,the effective width of the waveguide can be changed numerically,which makes the antenna have the ability of beam-scanning at a fixed frequency.The measured results show that the main beam direction of the proposed antenna can be steered from 46° to 68° at the operating frequency of 5.2 GHz by four different codes.