BS EN 62562:2011 pdf free download Cavity resonator method to measure the complex permittivity of low-loss dielectric plates
1 Scope
The object of this International Standard is to describe a measurement method of dielectricproperties in the planar direction of dielectric plate at microwave frequency. This method iscalled a cavity resonator method. It has been created in order to develop new materials and todesign microwave active and passive devices for which standardization of measurementmethods of material properties is more and more important.
This method has the following characteristics:
. the relative permittivity :’ and loss tangent tano values of a dielectric plate sample can be
measured accurately and non-destructively;
temperature dependence of complex permittivity can be measured;
the measurement accuracy is within 0,3 % for s ‘ and within 5×10—° for tano ;
fringing effect is corrected using correction charts calculated on the basis of rigorousanalysis.
This method is applicable for the measurements on the following condition:-frequency
: 2 GHz< f< 40 GHz;
- relative permittivity: 2 < E' < 100;
-loss tangent: 1o-6 < tano < 10-2.
2Measurement parameters
The measurement parameters are defined as follows:
where
D is the electric flux density;
E is the electric field strength;
ε is the permittivity in a vacuum;
ε and ε '' are the real and imaginary components of the complex relative permittivity ε r ;
TCε is the temperature coefficient of relative permittivity;
ε and ε ref are the real parts of the complex relative permittivity at temperature T and
T reference temperature T ref (= 20 °C to 25 °C), respectively.
3 Theory and calculation equations3.1 Relative permittivity and loss tangent
A resonator structure used in the nondestructive measurement of the complex permittivity isshown in Figure 1a.
A cavity having diameter D and length H = 2M is cut into two halves in the middle of itslength.
A dielectric plate sample having e ' , tano and thickness t is placed between these two halves.
The TEo11 mode, having only the electric field component tangential to the plane of thesample,is used for the measurement,since air gaps at the plate-cavity interfaces do notaffect the electromagnetic field.Taking account of the fringing field in the plate region outsidediameter of the cavity on the basis of the rigorous mode matching analysis, we determine s'and tano from the measured values of the resonant frequency fo and the unloaded Q-factor.This numerical calculation,however, is rather tedious.
u
Therefore,
a) approximated values e'a and tanoa from the fo and Quvalues by using simple formula for
a resonator structure shown in Figure 1b, where a fringing effect for Figure 1a is neglected,will be determined;
b) then,accurate values :' and tano from :'a and tanoa using charts calculated from the
rigorous analysis will be obtained.
where correction terms due to the fringing field Δε' ε' a , ΔA A and ΔB B are calculated numerically on the basis of rigorous mode matching analysis using the Ritz-Galerkin method, as shown in Figures 2 and 3. It is found from the analysis for a circular dielectric plate with diameter d that f 0 converges to a constant value for d D > 1,2 . The correction terms shown in Figures 2 and 3 were calculated for d D > 1,5 . Therefore, the correction terms are applicable to dielectric plates with any shape if d D > 1,2 .