Millimeter-wave Dielectric Phase Shifter

In this thesis, the millimeter-wave thin film dielectric phase shifter was investigated, which has significantly potential application in T/R module of phased array radar. After the analysis of some structures commonly used in dielectric phase shifter, a new structure named distributed capacitor-loaded phase shifter was carried out. It is comprised of a high-impedance transmission line periodically loaded with BST (BaxSr1-xTiO3) thin film capacitors. Several simulations for the designed phase shifter were performed in HP-ADS. Various factors were considered in influencing the insertion loss and the phase shift of the phase shifter. Some effective measures were put forward to improve its performance. The process was studied and the flow chart was given out. Finally the phase shifter was fabricated. The results are as follows:(1) BST thin film prepared by pulsed laser deposition is well crystallized. The average grain size is 100nm and the surface roughness is about 10nm. When the electric field intensity is 3v/, the tunability of the thin film is about 30% and the loss tangent is about 20% under room temperature. (2) The distributed BST capacitor-loaded phase shifter was designed, of which the high impedance transmission line is finite ground coplanar wave-guide (FGCPW). Three line microstrip couplers is the transition from FGCPW to microstrip. The DC block is not needed for no via holes in this structure.(3) Electrode loss contributes the major part to the total insertion loss of the phase shifter. It is capable to lower the insertion loss by using high conductivity electrode material and increasing the electrode thickness and quality factor of BST capacitor .At the same time increasing the tunability of the dielectric constant and the length of the transmission line can increase the phase shift.(4) By means of integrated circuit (IC) process the phase shifter was fabricated. Platinum is more suitable in forming the bottom electrode of BST capacitor than gold, but the top electrode and transmission lines prefer to gold.