GB/T 5597-1999 English PDF (GBT5597-1999)

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GB/T 5597-1999: Test method for complex permittivity of solid dielectric materials at microwave frequencies
GB/T 5597-1999
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 31.030
L 90
Replacing GB/T 5597-1985
Test Method for Complex Permittivity of Solid Dielectric
Materials at Microwave Frequencies
ISSUED ON: MAY 19, 1999
IMPLEMENTED ON: DECEMBER 01, 1999
Issued by: The Quality and Technology Supervision Bureau
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Definition ... 4
3 Principle of Test ... 4
4 Test Environment Conditions ... 5
5 Instruments and devices ... 5
6 Specimen Sizes and Requirements ... 7
7 Test Procedure ... 8
8 Calculation of Results ... 9
9 Test Error ... 11
Appendix A (Prompted) Schematic Diagram of Dielectric Test Cavity Structure ... 12
Appendix B (Prompted) Test Errors and Selection of Sample Thickness ... 13
Appendix C (Prompted) Schedule ... 16
Test Method for Complex Permittivity of Solid Dielectric
Materials at Microwave Frequencies
1 Scope
This Standard specifies the test method for the microwave complex permittivity of
homogeneous and isotropic solid dielectric materials.
This Standard applies to the determination of the complex dielectric constant within the
frequency range of 2 GHz ~ 18 GHz. The recommended test frequency is 9.5 GHz. Its
measurement range: the real part of the relative permittivity ε' is 2 ~ 20, and the dielectric loss
tangent tanδε is 1×10-4 ~ 5×10-3.
2 Definition
The complex permittivity εሶ is as follows:
Where:
εr - complex relative permittivity;
ε0 - vacuum permittivity, its value is 8.854×10-12F/m.
The complex permittivity mentioned in this Standard actually refers to the relative permittivity,
and is characterized by the real part of the relative permittivity ε' and the dielectric loss tangent
tanδε=ε"/ε'.
3 Principle of Test
At a certain frequency, the resonant length of the cylindrical TE0 01n mode high-quality factor test
cavity is lo, and the inherent quality factor is Qoe, as shown in Figure 1(a). When a disk-shaped
sample with a thickness d is placed in the test cavity, as shown in Figure 1(b), two changes will
occur: (1) since the dielectric constant ε of the dielectric sample is greater than 1, the phase
constant of the section of the waveguide filled with the sample medium will increase; and the
length of the resonant cavity at the original frequency will be shortened to ls; (2) since the
dielectric sample will introduce additional dielectric loss, the inherent quality factor of the test
Voltage resolution is 1µV, 4 ଵଶ digits of reading.
5.6 Crystal detector
Non-modulated broadband crystal detector.
5.7 Isolator
The isolation ratio is superior than 20 dB; and the forward and reverse standing-wave-ratio
coefficients are less than 1.20.
6 Specimen Sizes and Requirements
6.1 Sample diameter Ds
Where:
R – radius of test cavity, in mm;
δ – The amount related to the size of the test cavity is recommended to be 1.5 mm in the test
cavity with the recommended test frequency.
6.2 Sample thickness d
The principle of selecting the sample thickness d is to take its electrical length at about 85° to
improve the test sensitivity and reduce the test error. When the dielectric constant ε of the
material to be tested is roughly known, the sample thickness can be calculated according to the
following Formula.
Where:
fo – test frequency, namely, the resonant frequency of the test cavity, in GHz;
R - radius of test cavity, in mm;
d – sample thickness, in mm.
Selection of sample thickness can refer to Appendix B (prompted).
6.3 Sample requirements
The non-parallelism of the two main planes of the disc-shaped sample is no more than 0.01 mm;
and the non-straightness of the two main planes is no more than 0.01 mm.
There shall be no abnormal spots and scratches on the surface of the sample, and no abnormal
impurities and pores inside; it shall be strictly cleaned and dried before testing.
7 Test Procedure
7.1 Measurement of empty test cavity
7.1.1 Turn on the machine and warm up for 15 minutes to make the system work normally.
7.1.2 Set the signal source to output the continuous wave frequency at the test frequency fo,
adjust the precision graduated attenuator within the range of 9.0 dB~9.8 dB; adjust the output
level of the signal source; and make the crystal detector output can read the indication number
α0 of about 10 mV on the digital voltmeter; and record the attenuation amount A1 of the precision
graduated attenuator at this time.
7.1.3 Adjust the medium test chamber. The test cavity has been adjusted to the resonance point
determined by the digital voltmeter indicating that has dropped to the lowest point. The
frequency of the resonance point is fo. Record the piston position scale lo and resonance
frequency fo of the dielectric test cavity. At this time, the reading on the digital voltmeter is αr.
7.1.4 Adjust the precision graduated attenuator (decrease the attenuation), so that the reading
on the digital voltmeter rises from αr to return and rise to α0; record the attenuation A2 of the
precision graduated attenuator at this time, then the attenuation introduced by the dielectric test
cavity introduced at the resonance point is Aoe=A1-A2 in decibels.
7.1.5 Calculate the attenuation Ahe at the "half power point" of the resonance curve according
to Formula (4); and set the precision graduated attenuator at Ahe+A2. At this time, the reading
on the digital voltmeter is α'r, α'r< α0.
7.1.6 Fine-tune the frequency of the signal source. On both sides of the resonant frequency fo,
adjust the reading of the digital voltmeter to return to α0, and record the two frequencies f1 and
f2. Calculate Δfe=f2 - f1.
7.2 Measurement of the test cavity after placing the sample
7.2.1 Use the same exact procedure as in 7.1 to measure the piston position scale ls at the original
frequency fo, the resonance point attenuation Aos, the half power point attenuation Ahs and the
Where:
Δfo - resonant frequency test error;
ΔR - machining accuracy of test cavity radius;
ΔS1 - the error introduced by the micrometer precision of the cavity when measuring S;
Δf'o - the deviation of the tuning of the test cavity between two tests before and after being
placed in the dielectric. It is determined by experimental statistics;
Δd - the measurement error of the thickness of the dielectric sample;
Δ(Δf)s - after the sample is loaded into the test cavity, measure the error of the bandwidth at the
“half power” point of the test cavity. Determined by experimental statistics;
Δ(Δf)e – measure the error in frequency width of the “half power” point of the test cavity without
a sample, determined by experimental statistics;
ΔA11 – measure the error of attenuation A1 introduced by the accuracy of the attenuator;
ΔA21s - after the sample is loaded into the test cavity, measure the error of the attenuation A2
introduced by the accuracy of the attenuator;
ΔA21e - when no sample is loaded in the test cavity, the error of the attenuation A2 introduced
by the accuracy of the attenuator;
In order to achieve:
The above accuracy, the following requirements shall be met in the test: