July 1994, Volume 3, Number 2
Logic behind the design of a dual feedhorn for the 26-meter Cassegrainian antenna of the Agassiz Station-Harvard-Smithsonian Observatory is presented in the paper. Theoretically predicted arid measured results in the "waterhole" band (1.4-1.7 GHz) are presented. The antenna has been utilized in the Harvard Wide-Bandwidth HighResolution Microwave Search for ExtraTerrestrial Intelligence (SETI) Program, with the Observatory as a SETI-dedicated facility.
A new class of waveguide bandpass filters with suppressed higher-order passbands is described, designed, theoretically and experimentally verified. Methods of minimal autonomous blocks and mode matching are used for analysis. Attenuation of higher-order passbands is achieved by adding waveguide shunt elements to the filter structure.
The paper presents the results of modelling the influence of real atmosphere with precipitation clouds on the radar signal polarisation status. The relationship between the signal vector depolarisation shift value and the initial wave polarisation is examined.
This paper presents the multichannel sampling of a continuous-time signal with division of its frequency band into a few sub-bands. It deals with the combination of this sampling method and spline interpolation with the aim of utilizing their advantageous properties,i.e. low sampling frequency of the multichannel sampling and small error in the spline interpolation series. On the basis of the derived multichannel interpolation series by using of the spline functions, the simulation of two and three channel interpolation of the discrete signals was done.
In this paper the popular, multiple-feedback, ARC single opamp, highpass second-order filter is proposed in several types of modes, namely voltage, current and hybrid ones. These modes are studied and compared in detail. Computer experimental results are given supporting the theory.