Recent advances in MMCI technology make it possible to construct transitions from CPW-to-microstrip with via hole, microstrip-to-slot line and microshield line-to-CPW all of which have potential applications in the feed network of antennas. In this study we investigate the characteristics of the microstrip-to-slot line uniplanar transition using the finite element methods (FEM) and finite difference time domain (FDTD) techniques, and compared the theoretical results with the measurements. In both cases, the results agree with the measurements within a few percent

Dib, Nihad I.

Katehi, Linda P. B.

Simons, Rainee N.

Taub, Susan R.

Yook, Jong-Gwan

English

NASA Technical Reports Server

N A:sA-TJv1 ~) 0 (.,/5 to (;; 
NASA Technical Memorandum 106566 : NASA-TM-106566 19940028399 
Theoretical and Experimental Study 
of Microstrip-to-Slot Line 
Uniplanar Transition 
Jong-Gwan Yook, Nihad I. Dib, and Linda P.B. Katehi 
The University of Michigan 
Ann Arbor, Michigan 
Rainee N. Simons 
NYMA, Inc. 
2001 Aerospace Parkway 
Brook Park, Ohio 
and 
Susan R. Taub 
National Aeronautics and Space Administration 
Lewis Research Center 
Cleveland, Ohio 
Prepared for the 
1994 IEEE AP-S International Symposium and URSI Radio Science Meeting 
sponsored by the Institute of Electrical and Electronics Engineers 
Seattle, Washington, June, 19-24, 1994 
National Aeronautics and 
Space Administration 
https://ntrs.nasa.gov/search.jsp?R=19940028399 2020-06-16T12:00:28+00:00Z
~ L 1111111111111111111111Ii1Ifil~lrl'll~j Il'~lillrllllllllllllllll 
3 1176014088349 
Theoretical and Experimental Study of 
Microstrip-to-Slot Line Uniplanar Transition 
Jong-Gwan Yook*, Nihad 1. Dib, and Linda P.B. Katehi 
The University of Michigan 
Ann Arbor, MI 48109 
Rainee N. Simons 
NYMA, Inc. 
2001 Aerospace Parkway 
Brook Park, Ohio 44142 
and 
Susan R. Taub 
National Aeronautics and Space Administration 
Lewis Research Center 
Cleveland, Ohio 44135 
Summary 
Recent advances in MMIC technology makes it possible to construct transitions from 
CPW -to-microstrip with via hole, microstrip-to-slot line and microshield line-to-CPW all of 
which have potential applications in the feed network of antennas. In this study we investigate 
the characteristics of the microstrip-to-slot line uniplanar transition using the finite element 
method (FEM) and finite difference time domain (FDTD) technique, and compared the 
theoretical results with the measurements. In both cases, the results agree with the measurements 
within a few percent. 
1. Introduction 
Many of planar microwave circuit discontinuities have been characterized accurately with 
full wave integral equation (IE) techniques [1,2]. However, these approaches are limited to 
simple geometries. Frequency and time domain volume discretization techniques are more 
appropriate for the treatment of complex geometries involving arbitrary shapes. In this paper, 
the finite element method and the finite difference time domain technique have been employed 
for the characterization of the microstrip-to-slotline transition shown in Figure 1. This type of 
transition has potential to integrate MMIC based components such as phase shifters and 
amplifiers in the feed network of linearly tapered slot antenna arrays [3]. Derived theoretical data 
are compared to measurements. A brief summary of both techniques and explanations of the 
results will be given below. 
II. Formulations 
A. FINITE ELEMENT METHOD 
To apply the finite element technique we subdivide the considered space into tetrahedrons 
which are suitable for an arbitrary geometry. With this tetrahedral element the edge-based vector 
basis function [4] is employed to represent the local electromagnetic fields. For a given 
tetrahedron there are 6 edges and accordingly it has 6 unknowns per element. After we represent 
the field in a tetrahedron as a linear combination of six edge basis function, the energy 
functional derived from Maxwell's equations using Galerkin's procedure is minimized with 
respect to unknown coefficients. As a result we have a linear system of equations and the 
resulting FEM matrix is highly sparse and symmetric. This matrix equation is solved by using 
the preconditioned bi-conjugate gradient method with only non-zero matrix entries. Moreover, 
since there is a geometrical symmetry we can reduce the size of the problem to half of the 
original one. 
For the electric field formulation with ideal current excitation, the geometrical symmetry 
can be taken into account by incorporating a perfect magnetic (pmc) or electric (pec) wall 
depending upon even or odd excitations. If a geometry has longitudinal symmetry on which the 
tangential magnetic field is zero, we can consider that plane as a pmc wall regardless of 
excitations. Following the solution of the problem for each one of the excitation, the scattering 
parameters are evaluated using standard network techniques. 
B. FINITE DIFFERENCE TIME DOMAIN TECHNIQUE 
In order to characterize any planar discontinuity using the FDTD technique, Maxwwell's 
curl equations are expressed in discretized space and time domains. As an excitation, a Gaussian 
pulse is used because it varies smoothly in time and its Fourier transform is also a Gaussian 
function centered at zero frequency. Following the time and space discretizations of the electric 
and magnetic field components, the FDTD equivalents of Maxwell's equations are then used to 
update the spatial distributions of these components at alternating half time steps. The space 
steps, &, 8y, and Az, are carefully chosen such that integral numbers of them can approximate 
the various dimensions of the structure. After the pulse has been launched, the ground plane at 
the front wall is switched into an absorbing boundary. The super-absorbing first-order Mur 
boundary condition is utilized to terminate the FDTD lattice at the front and back walls in order 
to simulate infinite lines and the first-order Mur boundary condition at the top and side walls. 
In general, the frequency dependent scattering parameters, Sij' can be obtained from the 
voltages at ports i andj. To obtain Sl1(OO), the incident and reflected fields must be known. The 
incident field is obtained from that of an infinite extent line (i.e., from the source to far 
absorbing wall). Then, this incident field is subtracted from the total waveform to yield the 
reflected field. 
m. Results and Discussion 
Figure 1 shows the schematic diagram of the microstrip-to-slot line uniplanar transition. 
The two side arms of the microstrip T -junction are bent to form a circle. The circular microstrip 
2 
lengths a-b-c and a-d differ by A,g(microstrip/2 at a design frequency of 10 GHz, thus making the 
fields at the locations c and d 1~0° out of phase. This is necessary to excite the odd mode on 
the coupled microstrip lines. The characteristic impedances of the various lines are also indicated 
in Figure 1. The transition was fabricated on a 0.635 mm thick RT-Duroid 1010.5 with dielectric 
constant er equal to 10.5. 
Figure 2 shows measurements vs. theory for the transition in an open and shielded 
environment. Specifically, the measurements where performed in the open transition while the 
theory considered a completely shielded environment. This difference is mainly responsible for 
the 3 % change in the resonant frequency. Furthermore the measurements included conductor, 
dielectric, and radiation loss, while the theory considered a lossless case. As a result, the 
experimentaJ: data have a much broader resonance than the theoretical one. Figure 3 shows data 
derived through the FDTD method for the open transition shown in the same figure and verifies 
the claim made above. Specifically, there is a clear reduction in the resonant frequency from the 
shielded case and there is a considerable amount of radiation loss as shown in Figure 4. Using 
the above techniques, a parametric study of these transitions will be performed and the 
efficiencies of the two techniques in terms of computational times and accuracy will be 
discussed. 
IV. Conclusion 
In this study, the characteristics of the transition of microstrip-to-slot line which can be 
used as a feeding network of the tapered slot antenna are examined and the theoretical and 
experimental results are compared. This transition has very narrow bandwidth characteristics 
inherently. When there is considerable amount of radiation from the circuit, the numerical 
computations which is performed under shielding condition does not predict exactly the 
characteristics of the circuit. 
References 
[1] Linda P.B. Katehi, "Novel Transmission Lines for the Submillimeter-Wave Region," 
Proceedings of the IEEE, vol. 80, No. 11, pp. 1771-1787, Nov. 1992. 
[2] N.L. VandenBerg and Linda P.B. Katehi, "Generalized Full-Wave Treatment of Shielded 
Multilayer Structures Using the Vector Wave Function Field Expansion Method," 
Electromagnetics, vol. 13, pp. 67':84, 1993. 
[3] R.N. Simons, T.D. Perl, and R.O. Lee, "New Coplanar Waveguide Feed Network for 
2 x 2 Linearly Tapered Slot Antenna Subarray," Microwave and Optical 
Technology Letters, vol. 5, No.9, pp. 420-423, Aug. 1992. 
[4] M.L. Barton and Z.J. Cendes, "New Vector Finite Elements for Three-Dimensional 
Magnetic Field Computation," J. Appl. Phys., vol. 61, No.8, pp. 3919-3921, Apr. 1987. 
3 
r---------------------------------, 
I I 
I ~ Microstrip I 
I 70 fi /', I 
I /', I 
I / '" I I ,I
I 
iii' 
;:Q. 
Q) 
Figure 1.-Schematic diagram of microstript-to-slot line 
uniplanar transition. 
0 
'f' 
.. 
-10 
A 
A 
S11: FEM - shielded 
S21: FEM - shielded 
... S11: Measured - open 
'f' S21: Measured - open 
A 
" 
A 
"0 
::J -20 
:t:: 
c: 
0) 
as 
~ 
-30 
-40 L..-.......... --I..--'"_'--.......... --I..--'-_'---'---.L..--'-__ '--""---' 
9.4 9.6 9.8 10.0 10.2 10.4 10.6 10.8 
Frequency [GHz] 
Figure 2.-Scattering parameters for the microstrip-to-slot line 
transition. Comparison between FEM results and measure-
ment. 
4 
S11: FDTD 
I!l S21: FDTD 
-10 
r----------------, 
I I 
I I 
-30 
~O~~~~~~~~~~~--~~~~~ 
8 9 10 
Frequency [GHz] 
11 
Figure 3.-Scattering parameters computed by FDTD 
method with rectangular loop for the microstrip-to-slot 
line transition. 
12 
-10 ~~~~~~~~~--~~~~~~~~ 
8 9 10 
Frequency [GHz] 
11 12 
Figure 4.-Radiation loss of the microstrip-to-slot line tran-
sition obtained from the FDTD results. 
5 
REPORT DOCUMENTATION PAGE Form Approved OMB No. 0704-0188 
Public reporting burden for this collection of information is estimated to average 1 hour per response. including the time for reviewing instructions. searching existing data sources. 
gathering and maintaining the data needed. and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this 
collection of information. including suggestions for reducing this burden. to Washington Headquarters Services. Directorate for Information Operations and Reports. 1215 Jefferson 
Davis Highway. Suite 1204. Arlington. VA 22202·4302. and to the Office of Management and Budget. Paperwork Reduction Project (0704·0188). Washington. DC 20503. 
1. AGENCY USE ONLY (Leave blank) 12. REPORT DATE 
1
3
. 
REPORT TYPE AND DATES COVERED 
May 1994 Technical Memorandum 
4. TITLE AND SUBTITLE 5. FUNDING NUMBERS 
Theoretical and Experimental Study of Microstrip-to-Slot Line 
Uniplanar Transition 
WU-506-44-2C 
6. AUTHOR(S) 
Jong-Gwan Yook, Nihad 1. Dib, Linda P.B. Katehi, 
Rainee N. Simons, and Susan R. Taub 
7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION 
REPORT NUMBER 
National Aeronautics and Space Administration 
Lewis Research Center E-8743 
Cleveland, Ohio 44135-3191 
9. SPONSORINGIMONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSORINGIMONITORING 
AGENCY REPORT NUMBER 
National Aeronautics and Space Administration 
NASA TM-106566 Washington, D.C. 20546-0001 
11. SUPPLEMENTARY NOTES 
Prepared for the 1994 IEEE AP-S International Symposium and URSI Radio Science Meeting sponsored by the Institute of Electrical and Electronics Engineers. 
Seattle, Washington. June 19-24. 1994. Jong-Gwan Yook. Nihad I. Dib. and Linda P.B. Katehi. The University of Michigan. Ann Arbor, Michigan 48109; Rainee N. 
Simons, NYMA. Inc .• 2001 Aerospace Parkway, Brook Park. Ohio 44142 (work funded by NASA Contract NAS3-27186); 
Susan R. Taub, NASA Lewis Research Center. Responsible person. Rainee N. Simons. organization code 5630. (216) 433-3462. 
12a. DISTRIBUTION/AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE 
Unclassified - Unlimited 
Subject Category 33 
13. ABSTRACT (Maximum 200 words) 
Recent advances in MMIC technology makes it possible to construct transitions from CPW-to-microstrip with via hole, 
microstrip-to-slot line and microshield line-to-CPW all of which have potential applications in the feed network of 
antennas. In this study we investigate the characteristics of the microstrip-to-slot line uniplanar transition using the 
finite element method (FEM) and finite difference time domain (FDTD) technique, and compared the theoretical 
results with the measurements. In both cases, the results agree with the measurements within a few percent. 
14. SUBJECT TERMS 
Microstrip-to-slot line; Uniplanar transition 
17. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION 
OF REPORT OF THIS PAGE 
Unclassified Unclassified 
NSN 7540-01-280-5500 
19. SECURITY CLASSIFICATION 
OF ABSTRACT 
Unclassified 
15. NUMBER OF PAGES 
7 
16. PRICE CODE 
A02 
20. LIMITATION OF ABSTRACT 
Standard Form 298 (Rev. 2-89) 
Prescribed by ANSI Std. Z39-18 
298-102 


Theoretical and Experimental Study of Microstrip-to-Slot Line Uniplanar Transition

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server