A. A. Lavrinovich

Microwave-band reflection coefficient of high-temperature superconductor specimens in E-plane waveguide structures

The microwave-band reflectivity of high-temperature superconductor (HTSC) specimens was measured for the first time in the E-plane waveguide structures of two types: tapered waveguide termination and E-plane corner section. The measured reflection coefficient of a textured YBa2Cu3O7−δ specimen used as a tapered waveguide termination corresponds well to the theoretical curve calculated using an improved two-fluid HTSC model.

Temperature dependence of the microwave conductivity of a YBCuO film in the normal state

The results of an experimental study of the fluctuation conductivity of an optimally doped YBa2Cu3O7−δ epitaxial film are presented. The results were obtained from measurements of the complex reflection coefficient of the sample at grazing incidence according to a method developed and implemented by the authors in the millimeter wavelength range. The results demonstrate good agreement with a theoretical model constructed in the framework of Gaussian theory for a frequency-limited fluctuational 2D microwave conductivity in the temperature interval 93–120K.

Microwave - to - submm wave reflection and transmission coefficients for investigation of biochemical water solutions

The investigation of the complex conductivity (or permittivity) of superconducting samples by grazing incidence microwave reflectivity measurements is a promising method to study of the samples with different thicknesses in wide temperature range (i.e. conductivity range) [1,2]. The main feature of the method is use of grazing incidence p-polarized wave in order to increase the sensitivity of the measurement, which makes possible such a kind of investigation. The sensitivity of the reflection coefficient to permittivity changes increases up to Brewster angle, which is almost 90 degrees for metals and superconductors. The method could be also useful for the investigation of complex permittivity of different liquids and biochemical solutions by measuring of reflection or\and transmission coefficient of the samples under test.

Nonlinear coplanar waveguide on the basis of high-Tc superconducting thin film

Coplanar waveguides based on HTS thin films with two thicknesses were fabricated and their nonlinear properties were studied. Very weak nonlinear effect was observed at liquid nitrogen temperature. The effect increases under dc-bias applied to CW at T=77K and with increasing temperature up to critical value. The behaviour of phase coefficient for propagation constant is revealed to be strongly dependent on input power. The experimental results are in good agreement with theory, although the thermal effects are noticeable. The results show that planar transmission lines based on HTS thin films are promising structures for development of microwave signal limiters.