2-D localization and identification based on SAW ID-tags at 2.5 GHz

An identification and localization system based on surface acoustic wave (SAW) radio sensors is presented in this paper. This system is able to identify and localize objects within a two-dimensional area. Identification is achieved with a fixed coded passive SAW identification-tag. Localization is carried out with three receiving antennas and with a following analysis of time delay between the sent interrogation signal and the received signals. For practical tests, a special interrogator has been established, as well as the receiving and demodulation unit. The whole system is controlled by a computer.     

Buildup behaviour of IMPATT oscillators in linear and nonlinear ranges

The growth rate, frequency shift and starting amplitude of oscillations in IMPATT-diode oscillators are calculated in the linear and nonlinear range. It turns out that, with increasing r.f. amplitude, the frequency in such oscillators always decreases, and that this frequency shift cannot be compensated for by proper tuning of the load. The r.f. amplitude remains below the measurable level for a certain time depending on the oscillator tuning. This accounts for the observed delay of the onset of the r.f. pulse.     

Analysis of Excitations for a Groove Guide Resonator at 10 GHz by means of the FDTD Method

Various excitations of a new groove guide resonator working in the X-band (8 GHz – 12 GHz) are investigated by means of numerical simulations. For the numerical simulations the Finite-Difference Time-Domain method is used. The groove guide resonator, modelled both with and without excitation structures, is discretised in space. The results in the time domain are then transformed into the frequency domain in order to obtain the resonance frequency spectrum. Comparison between simulations with and without excitations shows the effect of the excitations on the resonance frequency spectrum. The results are compared with those of previous analytical methods.     

Millimeter waveband semisymmetrical groove guide resonators

As an alternative to the classical waveguides, such as the H-waveguide and the rectangular waveguide, the groove waveguide has been used at millimetre wavelengths for the last couple of decades. Most of these properties are attributed to the open sides of the guide, which reduce the wall losses. This article describes a semisymmetrical groove guide resonator that is designed and analyzed analytically, numerically, and experimentally. The numerical simulations are performed via a powerful time-domain simulator based on the finite-difference, time-domain (FDTD) method. Both Cartesian- and cylindrical-coordinate FDTD packages are developed and used for the simulations. The purpose in using cylindrical-coordinate FDTD is to calibrate Cartesian-coordinate FDTD and to see the error introduced due to discretization. A measurement setup with an adjustable support platform in the frequency range of 20-40 GHz is used in the experiments.     

Noise figure and conversion loss of self-excited Gunn-diode mixers

Gunn-effect oscillators, used as self-excited mixers in X band/v.h.f. band convertors, are investigated. Noise figure and conversion loss are measured. It is shown that both fairly high oscillator Q factor and proper matching of the input signal to the Gunn diode leads to mixers comparable in performance with usual microwave mixers. Because of the negative differential resistance of Gunn diodes, conversion gain is easily realisable.     

Lagrangian formulation of electromagnetic fields in nondispersive medium by means of the extended Euler–Lagrange differential equation

This work is concerned with the Lagrangian formulation of electromagnetic fields. Here, the extended Euler–Lagrange differential equation for continuous, nondispersive media is employed. The Lagrangian density for electromagnetic fields is extended to derive all four Maxwell’s equations by means of electric and magnetic potentials. For the first time, ohmic losses for time and space variant fields are included. Therefore, a dissipation density function with time dependent and gradient dependent terms is developed. Both, the Lagrangian density and the dissipation density functions obey the extended Euler–Lagrange differential equation. Finally, two examples demonstrate the advantage of describing interacting physical systems by a single Lagrangian density.