SIW Leaky Wave Antenna Based On CRLH

Leaky-wave antennas(LWAs)are attractive due to their inherent frequency beam scanning capabilities and broad operational bandwidth.In this paper,LWAs with continuous backwardto-forward scanning properties are studied based on composite-right/left-handed(CRLH)transmission line(TL)and substrate integrated waveguide(SIW).The proposed LWAs can provide good broadside radiation with wide backward scanning range.The investigations are addressed as follows:1.Two single-slot CRLH SIW LWAs are designed.The first one is the single-slot four-via SIW LWA.A rectangular transverse slot and four metalized vias are introduced as left-handed structure,combining with the SIW TL to form the CRLH TL radiation unit.The LWA consists of these radiation units scans from-52 ° to + 32 ° continuously.On the basis of the first design,the advanced single-slot SIW LWA is achieved by adding vias and changing the length of transverse slots.In this way,the gain is improved by 1 d B and the beam scanning range is increased to-58 ° to + 32 °.2.Miniaturization of CRLH SIW LWAs are investigated.The radiation efficiency of the antenna unit is improved by replacing the transverse slot to the rectangular loop slot.Therefore,the vertical size of the antenna is reduced by 40% while maintaining the highest gain.The scanning range is also widened to-62 ° to + 32 °.The lateral size of the former antenna is reduced by using half-mode substrate integrated waveguide(HMSIW)to achieve a more compact structure.The proposed LWA also exhibits continuous beam scanning from 55 ° to +31°.3.CRLH SIW LWA with low cross-polarization(XP)and circular polarization(CP)CRLH SIW LWA are studied.The XP level of the antenna is decreased 9 d B by adding cross-shaped slots on rectangular-loop slot to influence the electric field distribution.The gain fluctuation is also suppressed with the gain increased and beam scanning range widened to-61 ° to + 35 °.To achieve CP radiation,the perturbation is introduced by replacing the rectangular loop slot into the open loop slot.The antenna gain is more constant and almost higher than 10 d B.What's more,the beam scanning range is wide from-65° to + 31 °.