I. Vendik

Narrowband Y-Ba-Cu-O filter with quasi-elliptic characteristic

The compact meander-shape configuration of planar resonators is suggested for applications in narrowband filters with quasi-elliptic characteristic. The quasi-elliptic frequency response with two transmission zeroes at the edges of the passband is provided by the specific symmetry of the coupled resonators and is controlled by an appropriate choice of the resonator dimensions and the couplings between the resonators. The 12-pole quasi-elliptic filter with 0.5% fractional bandwidth at 1.775 GHz has been designed using meander-line microstrip resonators and manufactured on a double-sided YBCO film on a LaAlO/sub 3/ substrate. The filter exhibited the in-band insertion loss less than 0.5 dB at T=60 K, the return loss of 20 dB, the out-of-band rejection better than 75 dB, and 40 dB/MHz slope of the characteristic.

Development of CAD tool for a design of microwave planar HTS filters

Accurate design of microwave planar high-temperature superconducting (HTS) filters is obtained using a computer-aided design tool, which provides simulation of characteristics of the multicoupled transmission-line structures. The quasi-static spectral-domain method is applied. In order to achieve a good correspondence between measured and simulated filter performance, correct models of the microwave propagation characteristics of HTS planar transmission lines have to be used in the simulation procedure. The goal of this paper is to demonstrate that it is possible to design the planar HTS filters that do not need additional trimming after manufacturing. The trimmingless filters can be used in mass production for the next generation of mobile communication systems.

Narrow-band 10-pole Y-Ba-Cu-O filter on sapphire substrate

D-7602 I Karlsrulie. (icriiiaiiy (e-inail. Al~x;iiidcr.%act sev~~~~i~~~.~~k. ~l~) design of these structures [4, 51. A presumable explanation of this situation is a complicated simulation of the filter performance, which should take into account the anisotropy of sapphire dielectric permittivity. Most of commercial software does not take into consideration the anisotropy of the substrate and the HIS film contribution in the filter characteristics. We derived an effective CAD tool, which allowed a careful simulation of HTS planar structures on sapphire substrate [6]. In this paper, we present the results of joint efforts of manufacturing and investigations of the planar Y BCO resonators and bandpass filters on sapphire substrate.

High-temperature superconductor filters: modeling and experimental investigations

10-pole HTS microstrip band-pass filters with central frequency 1.75 GHz have been designed, manufactured, and investigated without any trimming in the linear and nonlinear regimes. A high filter performance with insertion loss not more than 0.5 dB and power handling capability up to 10 W of input power at T=60 K has been observed. Different commercial and home-made software were used to simulate the filter characteristics.

Criterion for a Switching Device as a Basis of Microwave Switchable and Tunable Components

An unifi-ed way to characterize a two-state one-port switching device is discussed. A criterion for characterization of a switching device called Commutation Quality Factor (CQF) is introduced. It can be applied to different types of switching devices (semiconductor, ferroelectric, superconductor etc.) and used for a design of two-state components with optimum characteristics. A simple formula is derived for calculation of the CQF. The invariance of the CQF with respect to lossless reciprocal transformation is shown. The applicability of the CQF does not depend on the physical nature of the device. The CQF is a working tool for a selection of switching devices while designing electronically controlled microwave components and subsystems.

Design of Trimmingless Narrowband Planar HTS Filters

The use of high temperature superconductor (HTS) films provides a higher selectivity of planar filters. The lower out-of-band interference increases the sensitivity of receiving systems and allows reduction of transmitter radiated power. Our goal was to show how these filters can be designed with a desired accuracy, and to give evidence for a real possibility of designing the trimmingless planar HTS filters. The analysis of filter performance is based on accurate models of the characteristics of the HTS planar transmission lines. The HTS film and substrate characteristic tolerance sensitivity is investigated. The design procedure of the trimmingless filter is proposed. Mass production of such filters requires a specific certification of the substrate materials and HTS films used.

Modeling gap discontinuity in coplanar waveguide using quasistatic spectral domain method

An efficient computer technique based on the spectral domain method is presented to solve the problem of modeling coplanar gap discontinuity. Comparison with available published data is done to confirm the accuracy of the method.

Phenomenological model of the microwave surface impedance of high-T/sub c/ superconducting films

The model of the microwave surface impedance of thin HTS films is based on a modified two-fluid approach and includes the phenomenological description of the normal and superconducting carrier density and the relaxation time of the normal carriers. A correlation between the London penetration depth at T=0 and the model parameter, which is responsible for the temperature dependence of the superconducting carrier density, was found from numerous experimental data. This correlation allows developing the phenomenological model of the HTS film surface impedance with minimal number of the fitting parameters: the transition temperature T/sub c/, the normal conductivity at T=T/sub c/, the residual resistance parameter, and the exponent describing the temperature dependence of the superconducting carrier density. The validity of the model was verified by a comparison with experimental data.

Investigation and Modeling Nonlinear Characteristics of High-Tc Superconducting Resonators

The high-quality resonators and pass-band filters based on high-Tc superconducting (HTS) films are of the most interest for practical applications. The industrial application of the devices is retarded by nonlinearity of the film surface impedance under microwave power of a high level. The phenomenological model of nonlinear characteristics of HTS resonators was developed and applied to different kinds of planar resonators: disk, parallel plate, and micro-strip resonator. A comparison of experimental and modeled characteristics of the resonators revealed the distinctive difference in the model parameters. Some limiting characteristics are discussed.

Design of Resonators and Filters based on LTCC Lumped Components

We propose a method of the equivalent circuitry parameter extraction for passive components suitable for LTCC application: interdigital capacitor, parallel-plate capacitor, and spiral inductor as planar and 3D versions as well. The experimental measurements were performed to benchmark the accuracy of the modeling results and verify the characteristic repeatability. The paper outlines the design capability to build 3D microwave LTCC resonators using the derived extraction procedure.