Statistical properties of linear antenna impedance in an electrically large cavity

Abstract

This paper presents models and measurements of linear antenna input impedance in resonant cavities at high frequencies. Results are presented for both the case where the cavity is undermoded (modes with separate and discrete spectra) as well as the overmoded case (modes with overlapping spectra). A modal series is constructed and analyzed to determine the impedance statistical distribution. Both electrically small as well as electrically longer resonant and wall mounted antennas are analyzed. Measurements in a large mode stirred chamber cavity are compared with calculations. Finally a method based on power arguments is given, yielding simple formulas for the impedance distribution.

Probability Distribution of the Quality Factor of a Mode-Stirred Reverberation Chamber

“…Probability density functions (PDFs) for idealized and imperfect fields, including EM boundary-value problems [1], [2], were calculated and compared with measurements or simulations. A natural extension is the stochastic characterization of intrinsic EM parameters of instrumentation and devices subjected to random fields, e.g., wave and input impedances [3]- [6], antenna parameters [7], [8], etc.…”

Two dimensional unstable scar statistics.

“…The idea of high frequency modal fields being composed of a random distribution of plane waves [6], leading to normal distributions of the field amplitude [7], [5] has been used in various areas, including problems in electromagetics [8]. Recently antenna radiation and coupling problems have been investigated using these chaotic field assumptions [9], [10], [11], [12], [13]. Many experimental verifications of predictions have also been carried out [14], [15], [16], [17].…”

Aspects of the Scattering and Impedance Properties of Chaotic Microwave Cavities

“…Our approach is to directly characterize the non-ideal coupling between the outside world and the system through a deterministic quantity known in electromagnetism as the radiation impedance, Z Rad . One can then define normalized impedance (z) and scattering (s) matrices that directly reveal the universal fluctuating properties of the scattering system [11][12][13]. More explicitly, the radiation impedance Z Rad = R Rad + iX Rad of each channel is determined in a separate measurement and combined with the cavity impedance Z = R + iX to create a normalized impedance matrix z as z =…”