INTERMODULATION DISTORTIONS IN TUNABLE LC FILTERS BASED ON VARICAPS

The article discusses the issues of minimizing intermodulation distortions arising in tunable bandpass filters made with the use of varicaps. It presents the analysis of the tunable filter circuits, on the basis of which we determined the circuits with minimum intermodulation distortions.

Multi-Pitch Liquid Crystal Filters with Single Layer Polymer Template

Multi-reflective peak and bandwidth scalable liquid crystal (LC) filters were investigated. By refilling a cholesteric LC (CLC) whose chiral pitch is different to the target template into a blue phase LC (BPLC) template, a multi-reflective peak single layer LC filter can be fabricated. With multiple templating and refilling processes, the number of reflective peaks can be further increased. Moreover, by refilling the CLCs of designed chiral pitch into a CLC template sequentially, a bandwidth scalable single layer CLC filter can be fabricated. The LC filters show great potential applications in optical communication, display, and LC lasing.

Asymmetric quasi impedance source buck-boost converter

An impedance source buck-boost converter (BBC) prototype for renewable energy (RE) application in the transportation industry is proposed. Its functions include stabilizing the variable output voltage of the RE sources such as fuel cells and photovoltaic cells. The converter utilized a topology of DC-DC quasi-impedance source converters (q-ZSCs) to achieve the gain curve of the BBC. With BBC gain curve, the converter earned advantages over the two other classes of non-isolated DC-DC q-ZSCs. These advantages include ecient buck-boost capability at the ecient duty ratio range of 0:35-0:65 and continuous and non-zero gain at the ecient duty ratio range. The converter's q-ZSC topology implies using two capacitors and two inductors. These two capacitors and inductors formed two separate LC filters that provides second order filtering compared to the first order filtering in BBC. Its other advantages over the traditional BBC include elim-ination of dead and overlap-time, simple contol and permitting higher switching frequency operation. The converter is capable of utilizing high switching frequency and asymmetric components to achieve BBC gain by using smaller components to reduce cost, weight and size. Its simulation response and that of a correspond-ing BBC for some given specifications were compared, presented and analyzed. An experimental scaled-down prototype was also developed to confirm its opera-tion. Analysis of the converters responses comfirmed the prototype's second order filtering as against the first order filtering in traditional BBC.