Volume 61, Nº 10 (2018)

The paper presents a rigorous solution of the electrodynamic problem for T-type waves in a coaxial waveguide of elliptical cross-section. The solution was obtained using the original modified elliptical coordinate system. The advantages of this approach are convenient expressions for the electrodynamic characteristics of the transmission line and a simple transition to a particular case of a circular waveguide. The authors have obtained explicit expressions for the impedance, transmitted power and propagation losses of the coaxial elliptical waveguide with T-type waves, and have analyzed their dependences on the size and shape of the cross-section of the transmission line. The graphs of the dependences of these characteristics on the normalized parameters that define the shape and size of the waveguide allow choosing the geometric dimensions of the transmission line based on the requirements of a given characteristic impedance, limiting transmitted power or losses. It is shown that at large eccentricities, the energy in waveguides with similar sizes of internal and external conductors and low wave resistance is concentrated near the foci, which allows using such waveguides as the basis for developing effective probes for radio-spectroscopic studies.

Devices for shaping and processing of signals based on known varieties of digital amplitude-phase modulation are considered. Their disadvantages are exposed during realization of modulation and demodulation of the signals that are characterized by non-rectangular signal constellations. There are explored properties of devices for shaping and processing of signals based on a new variety of signal modulation, namely amplitude modulation of many components (AMMC). The results of carried out researches show that advantages of proposed AMMC modulator are simplification of phase modulated or amplitude-phase modulated signal shaping, in particular AMMC signal shaping, and improve of modulator internal interference protection. Advantages of AMMC demodulator are simplification of phase modulated or amplitude-phase modulated signal processing, in particularAMMC signal processing, and improve of demodulator internal interference and zero drift protection at its practical realization. The proposed AMMC modulator and demodulator can be applied for shaping and processing of signals based on known and new varieties of amplitude-phase modulation.