Time-Domain and Frequency-Domain Methods Combined in the Study of Open Resonance Structures of Complex Geometry

Abstract

The paper discusses the methodological questions arising in the study of open electrodynamic structures of resonance quasi optics via time-domain technique. As demonstrated, all of the interesting physical characteristics inherent in these objects (including the objects with various frequency-selective elements) can be obtained through the numerical solution of the relevant model initial bowldaryvalue probhxns. For the first time, a finite difference method equipped with the exact local 'absorbing' conditions on artificial boundaries has been applied for the solution of this kind of open problems. The results of the computational experiments performed have verified the possibility of the efficient selection of oscillations in dispersive open resonators with diffraction gratings, among them the resonators with gratings operating in the quasitotal nonspecular reflection mode.

Time-Domain Analysis of Open Resonators. Analytical Grounds.

“…(12) A central problem of the approaches based on the spacetime representations is to obtain a reliable information about analytical properties of the resolvent operator-function of problem (11) everywhere over the natural region of variation of the complex frequency parameter k. This problem has been discussed in the context of the spectral theory of open resonators. Below are given some results of this theory [14,15,17,18] that will be used in further analysis.…”

“…In Table 1 we give approximate values of b and c obtained [11] from the well-known analytical representations for some fixed γ. Parameters β j allows one to excite the oscillation of a given symmetry class.…”

“…The resonant modes of the nonsinusoidal-wave scattering are highly sensitive to the influence of the virtual fields caused by reflections from the imperfect 'absorbing' boundaries L. The calculation of resonance electrodynamic characteristics calls, as a rule, for a long time intervals 0 < t < T [11]. Therefore, the reliable analysis of field oscillations in open high-Q resonant structures must not exploit those algorithms that truncate the computational domain inefficiently.…”

Compression and Radiation of High-Power Short Rf Pulses. Ii. A Novel Antenna Array Design With Combined Compressor/Radiator Elements

“…8(a)). The amplitude of free-oscillating field U (g 1 , t) decreases with time t as exp(−t|Imk|), so the value of |Imk| and, thus the Q-factor, can be found (see [30][31][32] for methodology). For the combined compressor/radiator element considered here, Imk = −0.095 and the Q-factor (see (13) in Part I) is Q ≈ 1225.8.…”

An FFT-Accelerated FDTD Scheme With Exact Absorbing Conditions for Characterizing Axially Symmetric Resonant Structures

“…It should be noted here that the proposed method allows the transient analysis to be carried for long time intervals and can provide highly accurate and reliable numerical data pertinent to physical processes under resonant conditions [14,[23][24][25]. The proposed method is especially useful for accurate analysis of long-duration processes in resonant radiators and energy compressors with different types of storage units (e.g., waveguide and open resonators with metal, semitransparent, and frequency-selective mirrors) and switches (e.g., distributed grating-type switches, interference and resonant switches).…”