Abstract ¾ Properties (complex
refractive index, permittivity, transmission and reflection coefficients) of
the different materials (liquid and solid dielectrics, semiconductors,
ferrites, composite, building, natural and common use materials) at the
millimeter and submillimeter wavelengths are presented. [1]
These properties are
of a great interest for millimeter and submillimeter guiding and antenna
systems, including passive and active devices inserted in such systems, for
millimeter and submillimeter propagation especially for indoor propagation, as
well for introscopy problem and for materials and media content testing (first
of all for aquametry).
Index Terms ¾ Millimeter and Submillimeter Waves,
Semiconductor, Ferrite.
I. INTRODUCTION
There are many papers with results
of investigation of the different materials in millimeter (MM) and
submillimeter (SMM) ranges. But sometimes it is difficult to compare the
results of the different authors. So the National Physical Laboratory (UK) has
carried out a complex experiment on intercomparison of measurement techniques
of 13 research groups from different countries [1]. The comparison of the
results of low loss materials (polyethylene, quartz, rexolite, BeO) properties
measurements has shown that the disagreement in measurement of real n
and imaginary k parts of complex refractive index
by different techniques amounts to 0.3 - 10 % for n and an order
of magnitude for k.
Therefore here we present some
results of our investigation at frequencies 30-500 GHz of the different
material properties (n, k, complex permittivity 
) for low loss and lossy dielectrics (including composite and
natural materials as well as polar and nonpolar liquids). The same properties
for ferroelectrics, semiconductors, and ferrites were measured, as well
components of ferrite permeability tensor were determined. For some kind of
artificial materials e.g. for clothes effective refractive index neff
,and transmission t and reflection r coefficients
were measured.
II. MEASUREMENT METHODS AND CIRCUITS
For measurements in the wavelength
range 8 - 0.6 mm we have used beam waveguide technique [2] with backward wave
oscillator (BWO) as a source (Fig. 1).
Fig. 1. Here I -
resonator for low loss material properties measurement, II -transmission
measuring circuit, III - Michelson or Max - Zender interferometer, IV -
reflectometer . 1 - BWO, 2 -magnet, 3 - horn, 4 -modulator, 5 -lens, 6 -
polarizer, 7 - attenuator, 8 - iris, 9 - receiver, 10 - absorber, 11 - mirror, 12
- beam splitter, 13 - amplifier, 14 - synchronous detector, 15 - digital
voltmeter, 16 - storage unit, 17 - voltmeter, 18 - light source, 19 - LED, 20 -
power supply.
Equipment fig. 1 allows to measure n,
k; e1, e2, t, r in very wide
intervals n from 1.05 to 20, 
from approximately 1
to 10-6, 
from 10-5
to 1, and 
from »1 to 10-4.
The method of measuring 
and 
, where l -sample thickness, f-frequency,
T - temperature appears to be the most universal. In the case of
liquids it was used tray of variable thickness with a readout accuracy Dl = ±1 mkm or if absorption is low
measurement chamber had short -circuiting plunger making it possible to vary
the liquid layer thickness.
To determine the k of low loss solid materials with n
from 1.3 to 1.6 the 
value is measured in
immersion liquids featuring practically the same refractive indices and certain
absorption.
In interferometer (see III, fig. 1)
arg t = j or 
are measured using
primarily the frequency sweeping technique which eliminates spurious
interference effects in the sample and beam path and provides unambiguous
determination of the interference order.
Measurements of the 
tensor components in
ferrites were performed with the aid of an interferometer with circulary
polarized waves which are the natural waves of the longitudinally magnetized
material. The diagonal, (
) and non-diagonal (
) components of are related to the 
of right and left
circularly polarized waves. The most accurate method of determination is by measuring 
by reversing the
direction of the permanent longitudinally magnetic field. Alternately, was determined by
measuring the Faraday rotation angle q of a linearly polarized wave: 
.
Of special interest are the measurements
double beam refraction and dichroism of crystals 
, 
(i, j=x,
y, z and i¹j). At small 
, and 
when 
, 
, 
and 
cannot be determined
individually with adequate accuracy rotating a sample between polarizers and
frequency sweeping were used. There are two adjacent frequencies 
corresponding to a
circular - polarization waves at the crystal output. These frequencies and the
angle of axis i rotation relative to the electrical field vector
of the incident wave, and reflection coefficients 
, 
allow us to find 
, and 
.
III. EXPERIMENTAL
RESULTS
Tables I - V present the measured
values of n and 
or 
and 
of the main materials
under test. Table I presents properties of low loss liquids.
TABLE 1
|
Nº |
liquid |
n ±0.3% |
|
l,m |
|
1 |
octane |
1.396 |
0.74 |
0.63 |
|
2 |
nonane |
1.405 |
0.93 |
0.63 |
|
3 |
decane |
1.407 |
0.83 |
0.63 |
|
4 |
cyklohexane |
1.424 |
0.5 |
0.63 |
|
5 |
crude oil |
1.47-1.51 |
0.8 ¸1.5 |
2.0 |
For practice it is important to know complex permittivity dependence of water content, w,%, in crude oil (Table II).
TABLE II
|
l, mm |
w, % |
e1 |
e2×102 |
a×102, dB/mm |
|
10 |
0.5 1.0 |
2.16 2.19 |
1.5 2.5 |
2.7 4.6 |
|
4 |
0.5 1.0 |
2.15 2.18 |
1.6 2.8 |
7.4 12.8 |
|
2 |
0.5 1.0 |
2.15 2.17 |
1.5 2.5 |
13.8 23.4 |
Table II shows very high dependence a on w%, especially at short MM waves. The same
dependence has alcohol - water solution.
Table III presents lossy liquids properties.
TABLE III
|
Nº |
liquid |
|
|
|
|
1 |
H2O |
6.3 |
8.8 |
2.0 |
|
|
H2O |
5.1 |
5.1 |
1.03 |
|
|
H2O |
4.7 |
4.0 |
0.74 |
|
|
H2O |
4.5 |
3.5 |
0.58 |
|
2 |
DMCO |
3.39 |
1.6 |
0.9 |
|
3 |
(CH3)2CO |
3.04 |
3.23 |
0.99 |
|
4 |
CH3COC2H5 |
2.69 |
2.19 |
1.02 |
|
5 |
CH3NO2 |
3.19 |
5.16 |
1.02 |
|
6 |
C6H10O |
2.62 |
1.06 |
1.02 |
, mmLow loss polymer properties gives Table IV.
TABLE IV
|
Nº |
Material |
n ±0.5% |
|
l,mm |
|
1 |
Teflon (unsintered |
1.35-1.44 |
0.23-0.26 |
0.63 |
|
2 |
Teflon (sintered) |
1.43 |
0.7 |
1.3 |
|
3 |
Polyethylene |
1.53 |
0.6 |
0.63 |
|
4 |
Polypropylene |
1.51 |
0.6 |
0.63 |
|
5 |
TPX |
1.44 |
0.41 |
1.3 |
|
6 |
Polystyrene |
1.59 |
2.4 |
0.9 |
|
7 |
Rexolite-1422 |
1.59 |
2.4 |
1.0 |
|
8 |
Duroid-5880 |
1.48 |
0.9 |
3.0 |
|
9 |
Teflon -4MB |
1.42 |
1.2 |
0.63 |
Here unsintered Teflon has density from 1.3 to
2.2 g/cm3.
The most interesting materials with n
> 1.7 properties presents the Table V.
In MM wavelength region there are a
lot of very lossy solid materials (first of all ferroelectrics). These
materials have 
up to 300 and
absorption up to 100 dB/mm (BaTiO3, TGS, KDP, La0.5Li0.5TiO3,
ferroepoxy and some other materials).
And lastly of interest for
communication, nondestructive test and other applications to know building,
natural , and clothes materials properties (Tables VI and VII).
In Table 6 less value of 
for pine-tree wood
corresponds to electrical field vector perpendicular to wood fibers.
So now we have very broad information
concerning electromagnetic properties of practically all kinds of materials and
media in frequency region 30-500 GHz and have equipment for measurement of such
properties.
TABLE V
|
Nº |
Material |
n ±0.5% |
|
l,mm |
|
1 |
SiO2 (crystal) |
ne =2.45 |
0.55 |
2.18 |
|
|
SiO2 (crystal) |
no =2.10 |
0.56 |
2.18 |
|
2 |
SiO2 (fused) |
1.95 |
1.4 |
0.85 |
|
3 |
SiO2 (ceramic) |
1.92 |
0.67 |
1.0 |
|
4 |
Al2O3
(ceramic) |
3.10 |
0.26 |
2.18 |
|
5 |
BeO |
2.63 |
1.2 |
1.0 |
|
6 |
MgF2 |
1.16 |
0.6 |
1.2 |
|
7 |
AlN |
2.88 |
0.7 |
1.4 |
|
8 |
GGG |
3.51 |
1.3 |
1.15 |
|
9 |
NB |
1.72 |
1.5 |
0.87 |
|
10 |
MgAl2O4 |
2.90 |
1.0 |
1.0 |
|
11 |
GaAs (r>108
Ohm×cm) |
3.60 |
0.2 |
2.24 |
|
12 |
Si (r>25×104 Ohm×cm) |
3.42 |
£0.01 |
1.46 |
|
13 |
YIG, Ni-Zn, Li ferrites |
3.54-3.95 |
0.8-1.5 |
2.0 |
TABLE VI, l=2 mm
|
Nº |
Material |
n ±1% |
|
|
1 |
Brick (r=1.5 g/cm3) |
1.8 |
3.5-4.2 |
|
2 |
Concrete (r=1.7 g/cm3) |
2.4 |
5.0-5.5 |
|
3 |
Asphalt (r=1.3 g/cm3) |
1.5 |
8.0 |
|
4 |
Sand (r=1.8 g/cm3) |
1.6 |
2.5 |
|
5 |
Pine-tree wood (moisture
<7%) |
1.4 |
3.4 / 2.0 |
|
6 |
Glass |
1.45 |
5.0 |
|
7 |
Veneer (d=7.6 mm) |
1.5 |
2.6 / 1.4 |
|
8 |
Marble |
1.5 |
1.0 |
|
9 |
Organic glass |
1.6 |
1.5 |
|
10 |
Cardboard |
1.8 |
6.0 |
TABLE VII, l = 1.6 mm
|
N |
material |
|
|
n-1 |
d, mm |
|
1 |
Clothes for tents |
82 ¸94 |
£1 |
0.2 -0.3 |
0.3 -0.5 |
|
2 |
Clothes coat,wool |
77 ¸84 |
£3 |
0.1 -0.2 |
2- 4 |
|
3 |
Clothes suit, wool |
85 ¸99 |
£1 |
0.20-0.35 |
0.5 -1.0 |
|
4 |
Silk |
89 ¸93 |
£1 |
0.28-0.35 |
0.15-0.25 |
|
5 |
Leather, natural |
79 ¸85 |
£8 |
0.35-0.45 |
0.9 -1.5 |
|
6 |
Leather, artifical |
87 ¸92 |
£5 |
0.22-0.28 |
0.7 -0.8 |
|
7 |
Fur, artifical |
75 ¸89 |
£3 |
0.04-0.07 |
4 -12 |
|
8 |
Fur, natural |
70 |
£1 |
0.14 |
35 |
,%
%REFERENCES
[1] J.R.Birch et.
al.. , “An intercomparision of measurement techniques for the determination of
the dielectric properties of solids at near millimeter wavelengths”, NPL Report
DES 115, Oct. 1991.
[2] V.V.Meriakri et al, “Submillimeter beam
spectroscopy and its applications. Problems of Modern Radio Engineering and
Electronics”, edd. by V.A.Kotelnikov, pp.179-197, Nauka, Moscow, 1982.
[3]
V.V.Meriakri, “Spectroscopy of millimeter and submillimeter ranges”, Moscow
University Physics Bulletin, vol. 47, no 3, pp. 81-88, 1992
[4] V.V.Meriakri and E.E.Chigrai, “Properties of
material for practical use at the mm and submm wavelengths”, 17 Int. Conf. on
IR and MM waves, Digest, pp.68-69, Colchester, UK, 1993
[5] V.V.Meriakri, Material properties in the
millimeter range, 3 Intern. Kharkov Symposium, “Physics and engineering of mm
and submm waves” ,MSMW ’98, Symp. Proc. Vol.1, pp. 121-123, Kharkov,Ukraine,
1998 .
