Research On Millimeter-wave Horn Antenna And Array Based On Multilayer Technology

Millimeter-wave bands are becoming increasingly important in wireless applications such as radar, imaging, and wireless communication systems due to the short wavelength, ultra-wide bandwidths and high doppler sensitivity. The thesis focuses on the design of transmitting and receiving antenna arrays used in the millimeter-wave velocity radars. The antenna array features low profile and high performance by using multilayer technologies such as LTCC and multi-layer PCB. The contents thesis can be summarized as follows:Firstly, a high-gain LTCC antenna is designed. Due to considerable dielectric loss at millimeter-wave frequencies, a relatively low-loss horn antenna with multi-layer structure is designed to achieve high gain. The designed antenna is then fed with microstrip and stripeline structures respectively to obtain optimum performance.Secondly, an antenna array features high gain and low sidelobes is proposed based on theories of irregular plane array. A radar antenna requires radiation characteristics of high gain and low sidelobes that may not be achievable with a single element. A regular array with uniform amplitudes features a sidelobe level about-13.5 dBi, which also cannot meet requirements in practical applications. A heart-shaped planar array is proposed in this thesis, which can improve the directivity of an array, thus achieving high gain and low side-lobes as well as smaller aperture compared with a conventional planar array. This research result has been applied for a national invention patent.Thirdly, feeding networks for the proposed array are accomplished. A feeding network with high efficiency is a challenge for an array. In this paper, high efficiency is achieved based on multiple coupling and power dividing of a stripline. Eventually, the designed LTCC antenna array features good performance with overall size of 24×21×1.6mm3. The relative VSWR(≤ 2) bandwidth is about 22%, and the simulated gain is 14.5dBi at the center working frequency of 30 GHz with side lobe below-22 dB on the E-plane and-27 dB on the H-plane. The heart-shaped array achieves very high radiation efficiency and aperture efficiency with a small size.Fourthly, a heart-shaped horn array is designed based on multilayer PCB process. It also features good performance with overall size of 32×39.3×4.8mm3. The simulated gain is 14.1dBi at 24 GHz with side lobes below-20 dB and back lobes below-25 dB.Finally, work in the thesis is summarized and possible improvements are discussed.