Research On Miniaturized Branch Line Directional Coupler Based On Tsv

With the rapid development of modern communication technology,higher requirements are put forward for wireless communication systems.High-quality and high-speed signal transmission,miniaturized and convenient mobile devices and high-integration RF systems have become the main trend of development at present.Branch line couplers play a vital role in wireless systems.The traditional structure faces the problems of large size and difficulty in integration,which seriously restricts the miniaturization development of RF systems.Three-dimensional integrated circuits(3D IC)and through-silicon via(TSV)technology can not only solve the traditional interconnection delay problem,but also provide greater flexibility for the design and integration of RF and microwave circuits.Taking advantage of the small size,integration and low loss of TSV,four branch coupler structures based on TSV technology are proposed for different application scenarios in this paper.The main tasks are as follows:1.A lumped element branch line coupler based on TSV is proposed based on the odd/even mode analysis and transmission line equivalence theory.The coupler adopts π type equivalent coil,and the operating frequency is 2.4GHz.The lumped elements adopt TSV solenoid inductor and double-layer RDL interdigital capacitor respectively.Through research and comparison of TSV solenoid inductors,RDL inductors,and IPD inductors,the advantages of TSV solenoid inductors have been confirmed.For the same inductance value,TSV solenoid inductors have the highest self resonant frequency and quality factor,while the area is only 53%of the traditional planar structure.The branch line coupler finally realized is in the frequency range of 2.1～2.4GHz,with return loss less than-19dB,insertion loss less than 1.53dB and isolation less than-20dB.Besides,the size is only 660×0.630×0.287mm3(0.018×0.017×0.0078λg2).2.Utilizing the broadband characteristics of multilevel branch line couplers,a three-branch coupler based on TSV is proposed.The high-density TSV nested MIM capacitor is used in the equivalent circuit.And the influence of the height of TSV,the thickness of insulation layer and the length of RDL on the capacitance is analyzed.Finally,the layout and interconnection of lumped components in HFSS are carried out,and the simulation results show that the relative bandwidth can reach 41.6%.3.Based on TSV technology and dual-band bridge T-coil(BTC),a dual-band branch line coupler with compact structure is proposed.The TSV solenoid inductors and MIM capacitors are interconnected by RDLs,and a compact layout of 1.342×0.876μm2(0.037×0.025λg2)is obtained.The proposed dual-band branch line coupler is modeled and verified by HFSS.The results show that the operating frequency of the proposed coupler is 2.4/5.2GHz.In the frequency range of 2.19～2.51GHz,the return loss is less than-15dB and the isolation is less than-15.6dB.In the range of 5.15～5.37GHz,the return loss is less than-15dB,the isolation is less than-17.2 dB,and the amplitude imbalance of the two frequency bands is within 0.28dB and 1.36dB,respectively.4.Two types of 3dB branch line couplers for millimeter wave applications is realized through the three-dimensional interconnection of coaxial TSV and CPW transmission lines.By using coaxial TSV and CPW as the main and branch lines respectively,a three-dimensional millimeter wave branch line coupler was implemented.In addition,an equivalent circuit model of the structure was established,and the accuracy of the circuit model was verified through finite element simulation.The proposed structure has the characteristics of low loss and high isolation at a high frequency of 100GHz,and the size is only 285×385×350μm3.On this basis,a small-sized and low loss three-dimensional meandering transmission line based on coaxial TSV was proposed.The transmission characteristics of the transmission line were studied,and a miniaturized millimeter wave branch line coupler with operating frequency of 30GHz was implemented using this transmission line,which size is only 768.7×695μm2(0.265×0.240λg2).