A novel transition between rectangular waveguide and layered ridge dielectric waveguide (LRDW) is reported. The transition is also suitable for use with image guide, insulated image guide, dielectric ridge waveguide and other open dielectric waveguides. Both experimental and theoretical data are presented which compare the new transition to three transitions reported in the literature

Dib, Nihad I.

Katehi, Linda P. B.

Ponchak, George E.

English

NASA Technical Reports Server

NASA Technical Memorandum 106661 /57:2 
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A Novel Transition Between Rectangular 
Waveguide and Layered Ridge 
Dielectric Waveguide 
George E. Ponchak 
Lewis Research Center 
Cleveland, Ohio 
and 
Nihad 1. Dib and Linda P.B. Katehi 
University of Michigan 
Ann Arbor, Michigan 
Prepared for the 
European Microwave Conference 
cosponsored by the Institute of Electrical Engineers and 
Institute of Electrical and Electronics Engineers 
Cannes, France, September 5-8, 1994 
e,""'  .. ., ... .. , '" ~ - ' ~ ' 
" 
National Aeronautics and 
Space Administration 
( NASA -TM-I066 61) A NOVEL 
TRANSITION BETWEEN RECTANGULAR 
WAVEGUIDE A 0 LAYERED RIDGE 
O IELECT~IC WAVEGUIDE (NASA. Lewis 
Research Center) 7 p 
N94-36955 
Unclas 
G3/32 0015728 
https://ntrs.nasa.gov/search.jsp?R=19940032448 2020-06-16T10:52:54+00:00Z
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A NOVEL TRANSmON BETWEEN RECTANGULAR WAVEGUIDE AND 
LAYERED RIDGE DIELECTRIC WAVEGUIDE 
George E. Ponchak 
National Aeronautics and Space Administration 
Lewis Research Center 
Cleveland, Ohio 44135 
ABSTRACT 
Nihad 1. Dib and Linda P. B. Katehi 
Radiation Laboratory 
Department of Electrical Engineering 
and Computer Science 
University of Michigan 
Ann Arbor, Michigan 48109-2122 
A novel transition between rectangular waveguide and Layered Ridge Dielectric Waveguide (LRDW) is reported. 
The transition is also suitable for use with Image Guide, Insulated Image Guide, Dielectric Ridge Waveguide and 
other open dielectric waveguides. Both experimental and theoretical data are presented which compare the new 
transition to three transitions reported in the literature. 
INTRODIICTION 
An efficient transition between dielectric waveguide and rectangular waveguide is critical for interconnecting 
dielectric waveguides such as image guide [1], insulated image guide [2], trapped image guide [3], ridge guide 
[4], and layered ridge dielectric waveguide (LRDW)[5,6] to test equipment and millimeter-wave sources such as 
Gunn diodes which typically have a rectangular waveguide output port. For open dielectric waveguides, the 
transition must not only match the impedances of the two different transmission lines but must also transform the 
fields from the well confined rectangular waveguide to the weakly confined open dielectric waveguides . In 
addition, the radiation loss from the open waveguide must be minimized to obtain a low insertion loss. Transition 
designs are especially difficult when high permittivity materials or layered ridges are used to fabricate electrically 
small dielectric waveguides. An example is the LRDW designed for Ka-Band shown in Figure 1. This dielectric 
waveguide is A.o/lO high and "A.o/5 wide at 30 GHz. All results presented in this paper are developed for transitions 
to the LRDW shown in Figure 1. 
Three types of transitions from rectangular waveguide to open dielectric waveguides have been reported in the 
literature. These may all be considered as variations of the transition shown in Figure 2a. In the first transition, 
referred to as A in the rest of the paper, the full height rectangular waveguide is butted directly to the dielectric 
waveguide. The second transition, referred to as B in the rest of the paper, incorporates a taper to reduced height 
waveguide. The dielectric waveguide is then butted directly to the reduced height rectangular waveguide. Since 
the height of the rectangular waveguide is now closer to the height of the dielectric waveguide, the field interaction 
is stronger and lower insertion loss is expected. Finally, a hom is added to impedance match the shielded dielectric 
waveguide to the open dielectric waveguide. This transition will be referred to as C throughout the rest of the 
paper. In each of the transition designs, a dielectric wedge or tapered section of the dielectric waveguide may 
be used to reduce the reflection from the transition [1]. 
This paper presents a new transition, shown in Figure 2b, from rectangular waveguide to open dielectric 
waveguide. A tapered ridge waveguide section is used to confine the power in the rectangular waveguide to an 
area equal to the width of the dielectric waveguide. The ridge is then continued into the horn section of the 
transition for impedance matching to the open dielectric waveguide. Since the ridge waveguide section localizes 
the fields better than the reduced height waveguide, the ridge waveguide transition has lower insertion loss and 
reduced radiation. This transition will be referred to as transition D in the rest of the paper. 
ExPERIMENTAl , CHARACTERIZATION 
Experimental characterization of the transitions was performed on an HP 8510B Vector Network Analyzer with 
a WR-28 Reflection/Transmission test set. The measurement system was calibrated to the end of the WR-28 
rectangular waveguide using the open, short, load calibration technique. To verify that any reflected power was 
due to the transition and not flaws in the dielectric waveguide, the time domain feature of the ANA was used to 
determine where all reflections originated from. The transitions were connected back to back through a 19 cm 
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section ofLRDW. The LRDW and the dielectric wedges were fabricated from RT/Duroid 5880, 6006, and 6010 
microwave substrates and Rogers 3001 bonding film. Through experimental characterization, the dielectric 
waveguide has a loss of 0.02 dB/mm. 
THEORETICAl. CHAR ACTERlZATION 
To theoretically characterize the transitions, the Finite Difference Time Domain (FDTD) method was used. 
Maxwell's curl equations are expressed in discretized space and time domains which are then used to simulate 
the propagation of an initial excitation in a "leapfrog" manner [7]. The excitation pulse is chosen such that its 
spectrum has a peak value at 30.5 GHz while the value is reduced to 5% of the peak value at 21 and 40 GHz (the 
TEID band of the WR-28 rectangular waveguide) [8,9]. The first-order Mur absorbing boundary condition (ABC) 
is used at the side and top walls surrounding the dielectric waveguide while the super-absorber first-order Mur 
ABC is implemented at the front and back walls. 
RESIILTS 
The accuracy of the theoretical modeling is demonstrated in Figure 3 which shows the measured and theoretical 
return loss for transition B with no dielectric wedge. The measured reflected power is lower across the frequency 
band than theoretically predicted due to the absence of conductor and dielectric loss mechanisms in the theoretical 
simulations. The maximum difference between the two curves is 2.5 dB . To eliminate the reflected power from 
the second transition during the experimental measurements, absorbing material was placed over the dielectric 
waveguide. The time domain feature of the HP8510 was used to verify that no signal was reflected from either 
the absorbing material or the second transition. 
Using the FDTD method, the power reflected from the transition, transmitted through the LRDW, and radiated 
into free space can be plotted. Figure 4 shows a cross-section of transition C without a dielectric wedge. The 
power transitioned to the LRDW is clearly shown across the top of the figure. Notice that the power is 
concentrated in the center layer, the low permittivity layer, of the LRDW. For this transition, the reflected power 
shown in the rectangular waveguide propagating back towards the source is relatively large. The radiated power, 
although small, is clearly shown propagating away from the transition faster than the power is propagating in the 
LRDW. 
The best measured performance for each type of transition is shown in Table 1. The Insertion Loss values at 26.5 
GHz and 40 GHz are per transition with the loss of the LRDW line subtracted out. The Return Loss value is the 
maximum value measured across the 26.5-40 GHz band for the back to back connected transitions. The length, 
height, and relative permittivity of the dielectric wedge are for the optimum characteristics which are given in 
Table 1. Transition D has the best overall characteristics with a total return loss better than 17.5 dB and an 
average insertion loss of 1.2 dB across the full waveguide band. The measured RF characteristics of transition 
D measured in the back to back configuration is shown in Figure 5. Note that the total return loss of transition 
Dis 5 dB lower than the return loss for transitions A, B, and C. Also, for all four transition types, an optimum 
dielectric wedge exists which improves the transition characteristics. 
CONCI JISIONS 
Transitions from rectangular waveguide to LRDW have been studied . A new type of transition which uses a ridge 
waveguide taper in both the rectangular waveguide and the horn section has been shown to have superior 
performance compared to previously used types of transitions. A maximum insertion loss of 1.5 dB with a 17.5 
dB return loss across the 26.5-40 GHz band has been demonstrated. 
ACKNOWT EDGEMENTS 
This work was supported by funds from the ARO (Army Research Office) and the NASA Lewis Research Center 
Director's Discretionary Fund. 
REFERENCES 
[1] M. Dydyk, "Image guide: a promising medium for EHF circuits," Microwaves, April 1981, pp . 71-80. 
[2] W. V. McLevige, T. Itoh, and R. Mittra, "New waveguide structures for millimeter-wave circuits," 
IEEE Trans. Microwave Theory Tech., Oct. 1975, pp . 788-794. 
[3] T. Itoh and B. Adelseck, "Trapped image guide for millimeter-wave circuits," IEEE Trans. Microwave 
Theory Tech., Dec. 1980, pp. 1433-1436. 
2 
I 
[4] T. Wang and S. E. Schwarz, "Design of dielectric ridge waveguides for millimeter-wave integrated 
circuits," IEEE Trans. Microwave Theory Tech., Feb. 1983, pp. 128-134. 
[5] A. G. Engel, Jr. and L. P. B. Katehi, "Low-loss monolithic transmission lines for submillimeter and 
terahertz frequency applications," IEEE Trans. Microwave Theory Tech., Nov. 1991, pp. 1847-1854. 
[6] G. E. Ponchak and L. P. B. Katehi, "Development of leaky wave antennas for layered ridge dielectric 
waveguide," IEEE AP-S Int. Symp Dig .. , Ann Arbor, Michigan, June 28- July 2, 1993, pp. 580-583. 
[7] K. Kunz and R. Luebbers, The Finite Difference Time Domain Method for Electromagnetics, Florida: 
CRC Press, 1993. 
[8] N. Dib and L. Katehi, "Analysis of the transition from rectangular waveguide to shielded dielectric image 
guide using the finite~fference time-domain method," IEEE Microwave and Guided Wave Lett. ," Sept. 
1993, pp. 327-329. 
[9] N. Dib and L. Katehi, "Characterization of the sub-mm wave dielectric waveguide directional coupler 
using the FDTD method," 1994 IEEE MTT-S Int. Microwave Symp. Dig., May 1994, pp. 297-300. 
Transition ~dge Return Loss (dB) Insertion loss at 26.5 GHz ~nsertion loss at 40 GHz 
Type X Wh) (cm) (dB) (dB) 
A /without 10.0 0.25 5.25 
A 1.91XO.15 Er=2.2 13.0 0.25 4.0 
B !without 9.0 2.25 3.75 
B 1.91XO.13 Er=6.0 10.0 1.0 1.5 
C lwithout 7.5 2.25 3.75 
C 1.91XO.13 Er=6.0 12.5 0.5 1.5 
D lwithout 10.0 1.5 2.75 
D !1.27XO.13 Er=6.0 ! 17.5 ! 0.75 ! 1.5 
TABLE 1. 
0.0635 
0.0203 
0 . 0254 
Figure 1 : Layered Ridge Dielectric Waveguide for 26.5-40 GHz 
(dimensions in cm) 
3 
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rectangular 
waveguide 
rectangular 
reduced height 
waveguide 
dielectric 
wedge 
Figure 2a 
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dielectric 
horn 
dielectric 
ground planes 
dielectric 
wedge 
Figure 2b 
Figure 2: Transitions between rectangular waveguide and dielectric waveguide 
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Sll log MAG 
Ref 0 dB 
5 dB/ 
hp 
Theoretical 
I-
Measured 
Start 26.500000000 GHz 
Stop 40.000000000 GHz 
Figure 3: Measured and theoretical return 
loss for transition B 
4 
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10. 0 
20.0 
30.0 
40.0 
>< 50.0 
60.0 
70.0 
80 .0 
90.0 
0.0 10 .0 
C 
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-10 
-15 
-20 
20.0 
-500.0 
30 .0 
z 
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40 .0 
Figure 4: FDTD analysis of transition C 
500.0 
Sl1 log MAG S21 log MAG 
Ref 0 dB 
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hp 
~ ~ .~ A 
~ lrv~1 W~ 
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Ref 0 dB 
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Start 26.500000000 GHz 
Stop 40.000000000 GHz 
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Figure 5: Measured characteristics of transition D 
5 
50.0 60 .0 
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June 1994 Technical Memorandum 
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A Novel Transition Between Rectangular Waveguide and Layered Ridge 
Dielectric Waveguide 
6 . AUTHOR(S) WU-307-51-OO 
George E. Ponchak, Nihad I. Dib and Linda P.B. Katehi 
7 . PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) B. PERFORMING ORGANIZATION 
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National Aeronautics and Space Administration 
Lewis Research Center E-8977 
Cleveland, Ohio 44135-3191 
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National Aeronautics and Space Administration 
Washington, D.C. 20546-0001 NASA TM-106661 
11. SUPPLEMENTARY NOTES 
Prepared for the European Microwave Conference cosponsored by the Institute of Electrical Engineers and Institute of Electrical and Electronics 
Engineers, Cannes, France, September 5-8, 1994. George E. Ponchak, NASA Lewis Research Center; Nihad 1. Dib and Linda PB. Katehi, Department 
of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109. Responsible person, George E. Ponchak, 
organization code 5630, (216) 433-3504. 
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13. ABSTRACT (Maximum 200 words) 
A novel transition between rectangular waveguide and Layered Ridge Dielectric Waveguide (LRDW) is reported. The 
transition is also suitable for use with Image Guide, Insulated Image Guide, Dielectric Ridge Waveguide and other open 
dielectric waveguides. Both experimental and theoretical data are presented which compare the new transition to three 
transitions reported in the literature. 
14. SUBJECT TERMS 15. NUMBER OF PAGES 
07 
Millimeter-wave; Microwave; Transmission lines; Waveguides; Transitions 16. PRICE CODE 
A02 
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