Research On Dual-Polarized Fixed-Frequency Beam Scanning Leaky-Wave Antenna Based On Dual-Mode Waveguide

Through the orthogonal polarization of the two signals,the dual polarization antenna can transmit and receive the two signals at the same time in the same bandwidth,multiplex the frequency,improve the frequency band utilization and increase the communication capacity.At the same time,the receiving characteristics of dual polarization antenna enable it to overcome the adverse effects caused by polarization rotation during reception and combat multipath fading through polarization diversity.Due to the above advantages,the dual polarization technology of antenna has been widely used in many fields.On this basis,in order to realize the dual polarization beam scanning,the dual polarization unit is usually used to construct the array antenna,and the electronically controlled beam scanning is realized in the form of phased array.However,phased array requires a large number of TR components,resulting in high cost,large volume and weight of antenna.Therefore,this paper studies the dual polarization electronically controlled beam scanning antenna based on the leaky-wave structure,uses two modes to generate the dual polarization radiation wave,and uses the periodic reconstruction method to realize the fixed frequency beam scanning.The main work and innovative achievements of this paper are as follows:1.A dual-mode waveguide design based on groove gap waveguide is proposed,which can transmit TE₁₀ and TE₀₁ modes simultaneously and realize the characteristics of slow wave transmission.By designing and combining the slow wave structures in groove gap waveguide which are independently suitable for TE₁₀ and TE₀₁ modes,a U-shaped slow wave structure is designed,which can increase the phase constants of TE₁₀ and TE₀₁modes to 542 rad/m and 558.8 rad/m,change the two modes from fast wave transmission to slow wave transmission,and show good transmission effect.2.A dual-polarization fixed-frequency beam-scanning leaky-wave antenna based on dual-mode slow-wave groove gap waveguide is designed.A periodic leaky-wave antenna is constructed by arranging periodic elements（each element is composed of transverse slot and longitudinal slot）in the metal layer above the groove gap waveguide.When the TE₁₀and TE₀₁ modes are transmitted simultaneously in the waveguide,it can produce dual-polarization radiation.By loading the PIN diode,the working state of the slot can be controlled,and then the working state of the radiation patch is controlled.On this basis,the electronically-controlled beam-scanning is realized by using the method of periodic reconstruction.In the actual measurement,the horizontal polarization of the antenna realizes the beam-scanning range of-43.8°～28.7°at 23.7 GHz,and the peak gain is 11.8d Bi;The vertical polarization realizes the beam-scanning range of-47.0°～19.3°at 22.7GHz,and the peak gain is 4.7 d Bi.3.Using a three-row-slot structure,the second dual-polarization fixed-frequency beam-scanning antenna based on dual-mode and slow-wave groove gap waveguide is designed.The three-row-slot structure adopted includes two rows of periodic longitudinal slots and one row of periodic transverse slots.Each slot excites its own radiation patch to construct a periodic leaky-wave structure.Under the excitation of TE₁₀ and TE₀₁ modes,the dual-polarization radiation beam is generated,and the electronically-controlled beam scanning is realized by controlling the PIN diode and using the method of period reconfiguration.The simulation results show that at 24.5 GHz,the horizontal polarization of the antenna realizes the beam-scanning range of-24°～45°,and the peak gain is 13.8 d Bi;The vertical polarization realizes the beam-scanning range of-25°～44°,and the peak gain is 16.74d Bi.Compared with the first dual-polarization fixed-frequency beam-scanning leaky-wave antenna,the vertical polarization gain of the antenna is significantly enhanced,and the cross polarization is effectively reduced.