Volume 61, Nº 2 (2018)

The maximum likelihood algorithm for estimating the arrival time of ultra-wideband quasi-radio signal with unknown amplitude and phase has been synthesized. The duration of the specified signal can amount to several periods or a fraction of harmonic oscillation period. The realization of maximum likelihood algorithm (ML) for estimating the arrival time of ultra-wideband quasi-radio signal is shown to be appreciably more complex than the realization of ML algorithm for estimating the arrival time of narrowband radio signal. The probability of reliable estimate, bias and scattering of ML estimate of the arrival time of ultra-wideband quasi-radio signal have been found with due regard for anomalous errors making it possible to investigate its threshold properties. The computer methods of statistical simulation were used to determine the performance efficiency of the synthesized algorithm of ML estimate and the limits of the application scope of obtained asymptotically exact (with the rise of signal-to-noise ratio) formulas for the characteristics of time arrival estimate of ultra-wideband quasi-radio signal with unknown amplitude and phase.

In this paper a new design of a six-port circuit based on multilayer substrate integrated waveguides (SIW) is presented. This design is based on the use of a multilayer structure aimed at reducing the dimension of the circuit while conserving the performances of the component. The designed SIW six-port is composed of two basic elements, a SIW power divider and directional coupler. These two elements are designed, optimized and matched to produce a better performance at the required operating frequency of 11 GHz. The results of simulations show that the new multilayer SIW six-port circuit has good performances including a good return loss and isolation under–20 dB and the transmission magnitude better than–10 dB. This multilayer SIW six-port has the advantage of a small size 160-34.8 mm; its width is about 50% smaller than the planar SIW six-port circuit, which helps to get a higher density of integration in telecommunication systems and allows much smaller devices to be conceived.A microstrip toSIWtransition is used in order to facilitate the integration of this component into other planar circuits. The structures are designed, simulated and optimized using the Ansoft HFSS simulation software.

At present, research and development of heterojunctions are conducted in the directions of searching for new compositions and technological regimes for the creation of ohmic and barrier transitions for gallium arsenide. The transition to silver-based metallization, which has large thermal and electrical conductivity comparing with gold and a relatively low diffusion coefficient to gallium arsenide, should improve the technical characteristics of the devices. One of the most important technological operations in the formation of Schottky ohmic contacts and barriers is thermal annealing. Silver to gallium arsenide contacts are made in vacuum by the method of thermal evaporation. The deposition and thermal treatment regimes for creating ohmic contacts of Ag–Ge–In/n–n⁺ GaAs with specific contact resistance ρ_c = (5...7)+10^–5 Ω.cm² are developed. The influence of the substrate temperature during the silver deposition and the annealing temperature on the height of the Schottky barrier Ag/n–n⁺ GaAs, the injection coefficient γ and the nonideality factor η is established.