No abstract

The most popular schemes of digital potentiometers (DP) and digital-to-analog converters (DAC) are considered. DP and DAC use how elements of parameter adjustment of active RC-filters. The circuits of the DAC on the Kelvin-Varley divider, the Kelvin divider based on the R-2R matrix, and the architecture of the DAC with a segmented circuit are shown. The internal structure of DP an Analog Devices and Intersil company is shown, and also the DP switching circuits in a tunable low-pass filter and a band-pass filter, a programmable inverting amplifier and a voltage regulator are presented.

Report is devoted to investigations of graphene meta–surfaces for the transmission of radiation induced by plasmons in subTHz and THz ranges, cell of which consists of structures based on graphene ring and graphene nano–tape. It create regimes of radiation transmission – transparency windows induced by electric dipole resonances. Resonant frequency of transparency window can be dynamically tuned in wide band of subTHz and THz bands by changing the chemical potential (Fermi energy) of graphene by applying external electric field (gating) instead of re–fabricating of structures. Questions of possibilities of electronic controlled filters creating of subTHz and THz bands grounded on different configurations of graphene meta–surfaces are discussed; their characteristics and frequency dependencies are investigated. Mathematical modelling and electrodynamic calculation of the filters characteristics of subTHz and THz bands grounded on multilayer structures of “graphene–dielectric” type are carried out. From results of mathematical modelling it follows that periodic layered microstructures “graphene–dielectric” type can be used for creation of subTHz and THz bands broadband filters of planar construction, controlling by electric field and fast tuning at small changes in Fermi energy level of graphene.

A band-pass filter with an extended operating frequency range based on composites - metamaterials is considered. Two design stages are presented, when, at the first stage, a two-stage microstrip filter on a resonator with a stepwise change in impedance, an SIR filter, is developed. At the second stage, the SIR-filter is remodified by adding to it a cell of mixed combined right-handed and left-handed transmission lines made of metamaterials. At lower frequencies, in the bandwidth, insertion loss is about 4 dB in the 3.1-4.2 GHz frequency range, due to the difficulty of meeting the impedance requirements of the mixed right-hand and left-hand transmission line, for all six phases throughout the ultra-wide frequency band is required. It was found that such methods are quite applicable for the design of other radio-electronic devices, in which impedance matching in an ultra-wide frequency band is required.