Tadeusz Morawski

Application of the FD-TD method to the analysis of circuits described by the two-dimensional vector wave equation

A class of microwave circuits described by a two-dimensional vector wave equation is defined. It is proposed to refer to them as vector two-dimensional or 2-DV circuits to distinguish them from circuits described by a two-dimensional scalar wave equation (typically referred to as 2-D circuits). It is shown that the 2-DV class contains some planar circuits filled with anisotropic media, two-dimensional waveguide discontinuities, and circular waveguide discontinuities. Calculation of dispersion characteristics of inhomogeneously filled hollow waveguides is an eigenvalue problem belonging to the 2-DV class. Application to the finite-difference-time-domain (FDTD) method to the analysis of 2-DV circuits is described. Examples show the efficiency of the method for several types of circuit. >

Analysis of circular horn antennas using the FD-TD method

Application of the vector two-dimensional FD-TD (finite-difference time-domain) method to the analysis of circular horn antennas is presented. An antenna should maintain axial symmetry of boundary conditions and can be arbitrarily shaped in two other directions, in the cylindrical coordinate system. The medium filling the antenna can be inhomogeneous. Modes of excitation of sinusoidal dependence on angle can be considered. A full-wave solution is obtained. An example of a circular horn antenna has been computed and compared with experimental data.<<ETX>>

A S-band 7 W GaN HEMT adaptive power amplifier

In the paper a 7 W GaN HEMT adaptive power amplifier (APA) operating over 1.8 to 4.0 GHz is presented. To control APA states the six pin diodes as regulators have been used in both input and output matching networks. The design is based on the small-signal approach for modelling active elements such as transistor and regulators. The measured results of APA have proven usefulness of the proposed design methodology. The APA is controlled by specialized unit - Universal Controller of Adaptation.

Ring of Four Overlapped Microstrip Hybrid Couplers

The ring of couplers known from Butler matrix, correlators and direction finding systems has been discussed in the paper. The ring of four hybrid couplers is a regular pattern of a fundamental eight-port forming a set of four output responses. The responses can be excited in two orthogonal modes. The eight port with ring of five hybrid couplers has been included as an extension of the basic ring of four couplers. The pentagonal ring enables four way distribution in three modes. All available modes have been discussed on the base of perfect scattering matrix. Both the rings were embodied using broadside coupled Overlapped Microstrip lines with PTFE substrates and were measured in frequency ranges 2-16GHz and 10-20GHz. The presented results prove existence of recognized modes in real imperfect embodiments within approximate bandwidth of an octave. The rings are devoted for widely meant analog signal processing.

A 300W S-band solid-state transmitter

This paper describes the structure and the performance of a 300 W compact solid-state transmitter operating over 2.9 to 3.1 GHz, for radar and medical applications. The transmitter consists of three major parts: PLL-DDS synthesizer, pulse shaping circuit and multi-stage class-C amplifier. A 300 W peak power with a pulse width up to 50 /spl mu/s and 5% duty cycle was achieved by combining two 160 W amplifiers with Si-BJT using a balanced configuration. The output power level is controlled in 6 dB dynamic range by means of a DC supply block. The power droop during RF-pulse is less than 0.2 dB for 5% duty operation in the whole output power dynamic range. The synthesized VCO achieves more than 10/sup -7/ long-term stability including pulling effect and -75 dBc/Hz@1 kHz phase noise. In addition the spectrum requirements are also satisfied.

The optimization of the transmittance phase changes of power amplifiers for T/R module of active phased array radar

A method of limitation of the transmittance deviation during the RF pulse of power amplifiers for the T/R module of active phase array radar is described. The method is based on the load-pull technique and is examined using a GaAs MESFET transistor.

An efficiency measurement of microwave two-ports using perturbation methods

For the determination of the efficiency of a reciprocal microwave two-port loaded with a known variable impedance, the measurement of three values of input impedance is required. If the region in which the load impedance can be changed is narrow, the error of the classical method (Ginzton 1957) may be significant. The perturbation method (Morawski 1973) which is described in this report can be used to determine the efficiency of any two-port and the error is comparable or even smaller than the error of the classical method. The perturbation method is particularly useful when the region of the load impedance change is narrow. This method is much simpler than the classical one for the matched network and for some special cases of unmatched networks. The method is convenient for the determination of the efficiency of jigs including PIN diodes, or varactors.

Microwave Phase Shifters for Radar Applications

Paper presents description of a method for designing phase shifters which enables obtaining multistate phase shifter based on varactor diodes with digital biasing system. It includes only two units which is a great advantage comparing to solutions with PIN diodes. Results of measurements of designed and constructed exemplary phase shifter for L-band (1.2-1.6GHz) are also presented.

Designing T/R module for active phased array radar

The paper presents the concept and the performances of the L- and C-band T/R module for an active phased array radar (APAR). The transmitters were optimized for minimum transmittance distortions and maximum output power level. The method used was based on a self-invented electro-thermal MESFET model. The receivers were optimized with respect to the minimum noise figure and maximum resistance for the input power. The most important parameters of the T/R modules are as follows: L-band with P/sub out/ = 100 W, /spl Delta/|T|<0.1 dB, /spl delta//spl phi/<1/spl deg/, F<2.5dB; and C-band with P/sub out/ = 4 W, /spl Delta/|T|<0.1dB, /spl delta//spl phi/<0.2/spl deg/, F<2.5dB.

Some properties of the quality factor of microwave switches

A switching system composed of an n-port, loaded with n–1 simultaneously switched elements is considered. It is proved that if the n-port is absolutely stable, then a quality factor of the system is less than or equal to the maximum value of the loading elements’ quality factors. As a consequence, any increase of the resulting quality factor is possible only at the price of the potential unstability of the system.