A series of polyimide/vanadium pentoxide (PI/V 2 O 5 ) hybrid film has been successfully fabricated through the in situ formation of V 2 O 5 within a polymer matrix by sol-gel process. The polyamic acid (PAA) is prepared from 4,4 0 -diaminodiphenyl ether (ODA) and 3,3 0 ,4,4 0 -benzophenonetetracarboxylic anhydride (BTDA) in N-methylpyrrolidinone (NMP) solvent. Then different amounts of Bis-(2,4-pentanedionato) vanadium oxide are incorporated into polyamic acid (PAA) matrix, respectively and then thermally imidized to form PI/V 2 O 5 hybrid membranes. The imidization temperature and time are optimized by FTIR measurements through the observation of V 2 O 5 absorption peak. The influence of V 2 O 5 content on the thermal stability, morphology and mechanical properties of PI/V 2 O 5 hybrid films are studied.
In a radio frequency (RF) system, it is possible to use variable inductors for providing tunable or selective frequency range. Variable inductors can be implemented by the microelectromechanical system (MEMS) process or by using transistors as switches to change the routing of coils or coupling quantities. In this paper, we investigated the design method of a variable inductor by using MOS transistors to switch the main coil paths and the secondary coupled coils. We observed the effects of different metal layers, turn numbers, and layout arrangements for secondary-coupled coils and compared their characteristics on the inductances and quality factors. We implemented two chips in the 0.18 m CMOS process technology for each kind of arrangement for verification. One inductor can achieve inductance values from about 300 pH to 550 pH, and the other is between 300 pH and 575 pH, corresponding to 59.3% and 62.5%, respectively, inductance variation range at 4 GHz frequency. Additionally, their fine step sizes of the switched inductances are from 0.5% to 6% for one design, and 1% to 12.5% for the other. We found that both designs achieved a large inductance tuning range and moderate inductance step sizes with a slight difference behavior on the inductance variation versus frequency.
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