Vapor deposition polymerization by a coevaporation of pyromellitic dianhydride and decamethylenediamine monomers has been employed for the preparation of polyamic acid as a precursor for polyimide films. By curing at temperatures of 200–250°C the polyamic acid became the polyimide with directional arrangement of the molecular chain in the normal to the substrate observed by wide-angle X-ray diffraction. The sample containing a large amount of oriented crystals showed a small photocurrent. It was concluded that the oriented chain containing a decamethylene moiety hinders the carrier transfer between pyromellitimide moieties, resulting in a decrease of current.
The pre-distortion linearizer, which is composed of a RF transistor with a self base bias control circuit, is described. By applying the p-MOSFET current mirror circuit to the self base bias control circuit, the linearizer responds the envelope of the modulated signal. The linearizer realizes both positive and negative gain deviations, and compensates the distortion of any PA's. The GaAs FET power amplifier (PA), which has negative gain deviation, achieves the adjacent channel power leakage ratio (ACLR) improvement of 8.1dB by using the proposed linearizer for QPSK modulated signal with the chip rate of 3.84Mc/s. Also, the LDMOS PA, which has positive gain deviation, achieves the ACLR improvement of 8.3dB.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.