Analysis And Simulation Of The Characteristics Of Millimeter Wave Antenna-in-Package Based On LTCC

With the rapid iteration of wireless communication technology,low-band spectrum resources are becoming scarce.Millimeter wave wireless communication technology is considered as one of the effective ways to achieve the next generation of high-speed communication because of its short wavelength,narrow beam and strong anti-interference capability.Using multilayer Low Temperature Co-fired Ceramics（LTCC）with high dielectric constant and low dielectric loss to make millimeter wave antenna dielectric substrate,and setting up the package cavity under the antenna to realize the design of high performance miniaturized millimeter wave RF system in the form of Antenna-in-Package（AiP）.This paper is based on the LTCC process to study the characteristics of microstrip array antenna and corresponding Antenna-in-Package array in W-band for in-vehicle radar.The main work includes:（1）Based on the theory related to microstrip antennas,a 45°polarized antenna unit operating in W-band millimeter wave AiP is designed.In order to improve the shortcomings of low gain and narrow bandwidth of microstrip patch,the design approach of compressing the antenna size in high order mode and introducing parasitic patch antenna is used in the design of this antenna unit,and the principle of the proposed method is also analyzed qualitatively.To further improve the antenna unit performance,the current distribution is optimized by loading slots in the antenna structure after simulating and analyzing the antenna size parameters that can affect the antenna unit performance.The designed antenna unit has about3.10 GHz bandwidth around the resonant frequency,which is about 130%higher than before optimization,and has more stable directionality.The antenna unit has a stable gain of more than 6.00dBi in the operating band,up to a maximum of 7.80dBi.（2）Using the designed antenna unit,an array antenna is built with parallel feed.The design and analysis of the T-shaped power divider required in the array antenna are developed.The effect of unit distance on the performance of array antenna is studied in a 1x2 array antenna with a designed T-shaped power divider.A 2x4 8-cell array antenna is ultimately obtained by symmetrically extending the feed network.The designed parallel feed network performs well.The 2x4 array antenna has a bandwidth of approximately 3.92GHz near the resonant frequency,and this array antenna has a stable gain of greater than 12.00dB in the operating band,with a maximum gain of 15.03dBi.（3）Employing the concept of Antenna-in-Package,there is a four-channel packaging layer vertically underneath the array antenna.The overall size of the designed AiP array is approximately 15.3mm×22.0mm×1.30mm.A 4.00mm×3.00mm air cavity is reserved for embedding the chip in the package layer.The AiP array has a reflection coefficient S₁₁ of less than-10dB from 76.54GHz to 80.67GHz and a bandwidth of approximately 4.13GHz near the resonant frequency,with a maximum gain of 15.30dBi.The performance of the AiP array is also analyzed as influenced by the physical parameters within the package layer such as feed-through vias size,isolation vias pitch and air cavity size.The AiP array achieved by determining the package size meets the requirements for miniaturization and high gain.