Research On E-band Slotted Waveguide Array Antenna With Low Sidelobe Levels

Nowadays,systems such as wireless communication and radar face complex electromagnetic interference and noise in the background of strong ground clutter.In some cases,the sidelobe level even exceeds the gain,which becomes the most important indicator in antenna design.Slotted waveguide(SW)array antennas have attracted much attention due to their outstanding advantages such as low loss in millimeter wave,large power capacity,and high radiation efficiency.Especially,the amplitude distribution on the radiation aperture is easy to control,to achieve low sidelobes or extremely low sidelobes.With these benefits,the SW array antenna is the first choice for millimeter wave antennas.In this thesis,two low sidelobe SW array antennas are designed and studied.The specific research contents are as follows:1.A low-profile,high-gain 32×64 waveguide slot array antenna for the 71-81 GHz band is designed.The antenna achieves different levels of low sidelobes and unequal beams-width in the E-and H-planes,respectively.The antenna is composed of 512(16×32)2×2-slot sub-arrays arranged with equal spacing in the x-and y-directions of the array and excited by a single ridge waveguides non-uniform corporate-feeding network.Array synthesis is performed on the feed network using two different sets of Taylor amplitudes to achieve low sidelobe levels.The sidelobe level and beam-width of the E-and H-planes can be independently controlled in combination with the different size and amplitude distributions of the x-and y-directions of the array.Since the Taylor amplitude distribution excites the 2×2-radiation element,which causes the quasi-Taylor distribution between the radiation slots,the 2×2-radiation elements are separately optimized and designed to suppress the grating lobe in E-plane which is caused by the quasi-Taylor distribution.Finally,A prototype slotted waveguide(SW)array is fabricated by machining to verify the array properties.The measurement results show that the reflection coefficient of the array antenna impedance matching is better than-14 dB over the entire bandwidth.The sidelobe levels in the E-and H-planes are below-18.9 dB/-24 dB,and the maximum half power beam-width is 2.3°/1.3°,respectively.In addition,a high gain of not less than 39.4 dBi and a cross-polarization discrimination(XPD)of less than-36.2 dB are also achieved.2.Another design is a wideband,high gain and low sidelobe SW array antenna operating at 70-88 GHz.The array antenna consists of 64(8×8)radiating elements and a single-ridge waveguide full-corporated feed network,and a standard waveguide port rotated by 45° feeds the entire antenna.The single-ridge waveguide of the feed network can widen the working bandwidth of the array antenna while reducing the size.The sidelobes of the square array are mainly concentrated on the main plane of the array arrangement direction.The designed array antenna reduces the sidelobe level by rotating the array plane by 45° to achieve 45° polarization.The simulation results show that the fractional bandwidth with a reflection coefficient less than-15 dB reaches 22.8%,the peak gain is better than 32.3dBi,and the sidelobe power is lower than-26.5dB with in the whole operating frequency band.