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References
1
and STEWART, w.J.: ‘Magnetism
from conductors and enhanced nonlinear phenomena’, fEEE Trans.
Microw. Theory Tech., 1999, 47, pp. 2075-2084
2
WILTSHIRE. M.C.K., PENDRS, J.B., YOUNG, I.R., LARKMAN, D.J.,
GILDERDALE, D J., and HAJNAL, J.V: ‘Microstructured magnetic materials
PENDRY, J.H., HOLDEN, A.I., RoBBiNs, D.J.,
for RF flux guides in magnetic resonance imaging’, Science, 2001, 291,
(5S05), pp. 849-851
3 LANDAU, L D., and LIFSHIZ. E.M.: ‘Electrodynamics of continuous media’
(Pergamon Press, Oxford UK, 1984)
Fast electromagnetic characterisation
method of thin planar materials using
coplanar line up to V-band
Extraction method: The extraction method of the dielectric substrate
properties is based on S-parameter measurements achieved at the
coplanar access planes. It requires the propagation to be the quasiTEM dominant mode and dispersion to be low ( h > W+2s). The
reflection/transmission method [5] allows the first reflection (r)to be
obtained at the input of the coplanar cell and the first transmission ( r )
along the coplanar cell of length d. The resolution of the reflection/
transmission methods equations leads to the terms of complex
effective permittivity and permeability [ 5 , 61. However, for nonmagnetic materials to be measured, it is possible to increase the accuracy
of the E:. and E: characteristics by fixing the permeability at I in the
reflection/transmission method. This leads us to look for only one
complex unknown instead of two. Two equations can then be
determined [6, 71:
t&f/
=
(g)[email protected]
J. Hinojosa, K. Lmimouni and G. Dambrine
A very broadband method for determiningthe electromagnetic properties of isotropic thin planar materials, which uses a coplanar line as a
cell, is presented. The complex permittivity is quickly computed from
S-parametermeasurements of coplanar cells propagating the dominant
mode by using analytical equations. Measurements between 0.05 and
75 GHz of alumina and doped silicon show good agreement between
measured and predicted values.
where Z, is the characteristic impedance of the test device (50 Q) and
Zb is the characteristic impedance of the coplanar cell when E,. = p,. = 1,
which is computed from an analytical equation [3].
In the case of (I), owing to the periodic behaviour of the coplanar cell
with frequency, dimensional resonances appear on the Sll and
parameters at frequencies corresponding to integer multiples of one
half wavelength (Q. At these particular frequencies, the S I Iand
magnitudes are small and the phase uncertainties are large [6-81. This
leads to the appearance of inaccuracy peaks in the computed complex E,.
values. These inaccurate peaks can be avoided by using (2) as in [7].
The exchange between complex effective permittivity and the sample
desired relative permittivity (E,) is obtained from analytical equations
[3,41:
r
(3)
(4)
where qtg 6,,,/1= (1 -(~;)-‘)/(l - (E:.&’)
is the filling factor for the
effective dielectric loss [4] and tg Sder*= E & / E ; . ~ The parameters k, kl ,
k’ and k; are bound to the coplanar line structure. K(k), K(k’), K(kl),
K(k;) are the complete elliptical integrals of first order of modulus k and
k , and complementary modulus k‘ and k ; . These integrals are also
obtained by analytical equations [4].
51.O-
(0
H: I
(io\
50.5-+$
+
0
*
+-
m
73
a
.._E
50.0-
c
.-
I
. . .
:
L
.
-
iii)’
0
0
L
W+2S=175ym
h=635 pm
coplanar cell
E2
;
49.549.0!
.
L
L
v ti IS L
h r r E , pr
I
5
I
I
I
I
10 15 20 25
I
1
I
I
I
I
I
I
I
I
30 35 40 45, 50 55 60 65 70 75
frequency, GHz
Fig. 1 Coplanar characteristic impedances against frequency and various
substrates
Coplanar configurations have been optimised to SO R and values have been
computed from spectral domain approach numerical method [2]
(i) W c,= 10 -jO.O, AI, = 1 -;O.O
(ii)
c,= IO-jO.1, &.=0.6-;0.006
(iii) A E,.= IO-jl.0, /1,.=3-jO.3
Measurement bench: To implement measurements with coplanar
cells up to 75 GHz, we have chosen two commercially available onwafer systems covering DC-40 GHz and 50-75 GHz, which use
coplanar lines as probes. They allow different sizes of coplanar line
and easy and fast measurements to be implemented without thermocompression between the on-wafer system and the coplanar cell.
The S-parameters measurements are repeatable and accurate. The
calibration procedure uses a line-reflect-match (LRM) covering
0.05-75 GHz, since the quasi-TEM mode dispersion of the 50 !2
characteristic impedance coplanar standard lines on alumina substrate
is very low. The two obtained reference planes are the outputs of the
two probes. Retum losses, insertion losses and repeatability were
better than - 15, - 1 and -50 dB, respectively, in the 0:05 to 75 GHz
frequency range.
Results: Alumina (~$=9.85, ~:<0.001 at 10 GHz, pv= 1) (Fig. 2)
and doped silicon (E: = 1 1.7, 40 Q c m < p < 60 R cm) (Fig. 3) with
well-known dielectric properties were measured in the 0.05 to 40 GHz
and 50 to 75 GHz frequency ranges at room temperature. The
coplanar cells were made from thin-film technology (gold conductor)
~41.
In this Letter we present an easy and fast complex permittivity
extraction method of the coplanar substrates from S-parameter measurements, which takes into account the quasi-TEM mode. The S-parameter
measurement bench employs vector network analysers and coinmercially available high-quality on-coplanar test fixtures covering
0 . 0 5 4 0 and 50-75 GHz without the necessity to make a transition
between the network analyser and the sample-cell as in [l].
ELECTRONICS LETTERS
11th April 2002
The measured E: values for alumina (Fig. 2) and doped silicon
(Fig. 3) correspond to those anticipated. The error is lower than 3%
with regard to the manufacturer values at frequencies above 5 GHz. At
frequencies below 5 GHz, the large errors on E: are due to large
uncertainties on the S-parameters. Various integer multiples of one
half wavelength are required to increase the accuracy of the complex
permittivity with this method [6, 71. As can be seen from Figs. 2 and 3,
Vol. 38 No. 8
373
c: values do not exactly correspond at 40 and 50 GHz. These errors are
linked to the position errors of the on-wafer system probes at the access
planes of the coplanar cells. The small resonances in E: and E: values in
the 0.05 to 40 GHz frequency range for alumina are due to the
fabrication imperfections of the coplanar line, which do not disturb
the result interpretation. Thus, they were avoided in the 50 to 75 GHz
frequency range by omitting some measurement points. This same
process was carricd out for doped silicon (0.05-75 GHz). The small
increment of the E: and E:’ values against frequency for alumina and
doped silicon is due to both the low dispersion of the 50 R characteristic impedance coplanar load and the low quasi-TEM mode dispersion
of the measured coplanar cells. These factors were not taken into
account during the LRM calibration procedures (0.0540 and 5075 GHz) nor by the analytical equations in the complex permittivity
extraction method. In the case of dielectric losses, large errors are
shown for alumina (Fig. 2). These errors are mainly due to the network
analyser, the test fixture performance, and the whole coplanar cell
(dielectric, metallic and radiation) losses. A detailed error bound
analysis of this method from [7] is presented in [6]. The measurement
of low-loss samples is difficult with this technique. To obtain reasonable accuracy, E:! must be greater than 0.1 as the case of measured doped
silicon (Fig. 3), where the values are in good agreement with the
manufacturer data.
J. Hinojosa (Universidad Politbcnica de Cartagena, Departamento de
Electrbnica, Tecnologia de Computadoras y Proyectos. C / . Doctor
Fleming s / n , 30202 Cartagena (Murciu), Spain)
E-mail: [email protected]
K. Lmimouni and G. Dambrine (DGpartement HyperfrC.qzcences et
Semiconducteurs, lnstitut d’Electronique et de Microblectronique du
Nord, Cite Scienti$que, Avenue PoincarG, B.P 69, 59652 Villeneuve
d’Ascq Cedex, France)
References
HINOJOSA, J., KRuCK, J.F., and DAMBRINE, G.: ‘Ridged waveguide to
microstrip transition for electromagnetic characterisation of materials in
V-band’, Electron. Lett., 2000, 36, (17), pp. 1468-1469
ITOH, T., and MITTRA, R.: ‘Spectral-domain approach for calculating the
dispersion characteristics of microstrip lines’, IEEE Trans. Microw
Theory Tech., 1973, 21, (7), pp. 496-499
CHIONE, G., and NALDI, C.: ‘Analytical formulas for coplanar lines in
hybrid and monolithic MICs’, Electron. Lett., 1984,20, (4), pp. 179-181
HOFFMANN, R.K.: ‘Handbook of microwave integrated circuits’ (Artech
House Inc., 1987)
WEIR, W.B.: ‘Automatic measurement of complex dielectric constant and
pemieability at microwave frequencies’, Proc. IEEE, 1974, 62, (l),
pp. 33-36
HINOJOSA, J.: ‘Contribution I’klaboration d’une nouvelle methode de
caracterisation electromagnttique de matkriaux a partir de lignes
plaqukes - Applications a I’etude de nouveaux matkriaux’. Thkse
d’universite en Electronique, Lille, France, May 1995
BOUGHRIET, A., LEGRAND, C., and CHAPOTON. A : ‘Noniterative stable
transmission/reflection method for low-loss material complex
permittivity determination’, ZEEE Trans. Microw. Theory Tech., 1997,
45, (I), pp. 52-57
DONEKER, B.: ‘Accuracy predictions for new generation network
analyzer’, Microwave 1,1984, 6 , pp. 127-141
Millimetre-wave wideband reflection-type
41
0
I
I
I
I
I
I
I
I
I
I
I
I
I 1 0
10 15 20 25 30 35 40 45 50 55 60 65 70 75
I
5
frequency, GHz
2 Measured E, data ,for alumina
Cell dimension: W = 50 pm, W+ 2S= 175 pm, h = 635 pm,f = 5 pm, length
d = l cm
, 10
20F .
I
CPW MMIC phase shifter
Hong-Teuk Kim, Dae-Hyun Kim, Youngwoo Kwon and
Kwang-Seok Se0
A reflection-type coplanar waveguide (CPW) phase shifter fabricated
using a standard monolithic microwave integrated circuit (MMIC)
process is presented. Air-gap overlay CPW couplcrs were employed
for wideband 3 dB coupling and low loss at millimetre wave. The twostage cascaded analogue phase shifter showed insertion losses of
6.9 1.6 dB, return losses > 10 dB, and maximum r m s phase error
of 15.5” for the relative phase shift from -20” to 135”, over a
wideband 27 to 47 GHz.
+
5
4
0
,
5
,
,
,
,
,
,
,
,
1
,
,
,
,
!
0
10 15 20 25 30 35 40 45 50 55 60 65 70 75
frequency, GHz
Fig. 3 Measured E,. data for doped silicon
Cell dimension: W=70 pm, W+ 2 S = 175 pm, h = 230 pm, t = 3 pm, length
d = l em
Conclusion: The experimental results have demonstrated the validity
of the method. This method can be conveniently applied to the study
of isotropic dielectric film-shaped materials in the 0.05 to 75 GHz
frequency range.
Acknowledgments: The authors thank S. Lepilliet for his contributions to the measurements with the network analyser.
0 IEE 2002
Electronics Letters Online No: 20020272
Dol: IO.1049/el:200202 72
37 4
8 November 2001
Introduction: Various reflection-type microstrip monolithic microwave integrated circuit (MMIC) phase shifters have been reported
using Lange couplers [l-31. However, coplanar waveguide (CPW)type reflective MMIC phase shifters have not been common since the
low-loss broadband 3 dB CPW coupler compatible with the standard
MMIC process have not been available. Previously, analogue
reflection-type CPW MMIC phase shifters with narrow bandwidth
( < I GHz) were realised using multilayer CPW couplers in which the
overlapped conductors were separated by an extra dielectric layer [4,
51. However, the phase shifters showed high mean losses of
31 dB/36Oo with eight couplers at 24 GHz [4], 16 dB/12Oo with
two couplers at 31.5 GHz [SI due to lossy polyimide dielectrics and
strong field intensities between the coupler conductors. Recently, the
authors proposed a standard MMIC-compatible Lange coupler using
air-gap overlay CPW structures [6]. The coupler showed very low loss
(0.6 dB at 30 GHz) over a wide frequency range 20-39 GHz. In the
overlay CPW coupler, the air-gap offset broadside coupling between
two lines offers tight coupling and reduces the conductor loss by
redistributing currents over broad surfaces. In this work, a millimetrewave two-stage cascaded reflection-type analogue phase shifter was
realised using a standard uniplanar MMIC process. There are no
additional dielectric layers for the couplers. The air-gap overlay CPW
couplers and GaAs Schottky varactor diodes were used as key
components of the phase shifter.
ELECTRONICS LETTERS
11th April 2002
Vol. 38 No. 8
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