U.S. patent number 3,771,077 [Application Number 05/075,086] was granted by the patent office on 1973-11-06 for waveguide and circuit using the waveguide to interconnect the parts.
Invention is credited to Frederick J. Tischer.
United States Patent |
3,771,077 |
Tischer |
November 6, 1973 |
WAVEGUIDE AND CIRCUIT USING THE WAVEGUIDE TO INTERCONNECT THE
PARTS
Abstract
Rows of generally parallel elongated conducting members,
parallel to the polarization of an electromagnetic wave and
intersecting a dielectric slab, are used to control the path of
such wave. The invention may take the form of a waveguide. A
waveguide utilizes a slab of insulating material. Two parallel rows
of metallic posts, with each post generally perpendicular to the
slab, intersect the slab. The rows of posts are spaced apart a
distance at least equal to 0.6.lambda..sub.o where .lambda..sub.o
is the free space wavelength for the lower end of the operational
wavelength range of the circuit. The radio frequency energy
transmitted down the waveguide is polarized electrically in a
direction parallel to the axes of the posts. The new waveguide, in
one of its forms, is ideally suited to constitute an antenna, and
is so shown as one form of the invention. The new waveguide is also
ideally suited to interconnect the components of an electric
circuit, and therefore I have also illustrated a portion of a
circuit with the electronic components interconnected by the new
waveguide.
Inventors: |
Tischer; Frederick J. (Raleigh,
NC) |
Family
ID: |
22123455 |
Appl.
No.: |
05/075,086 |
Filed: |
September 24, 1970 |
Current U.S.
Class: |
333/239;
343/785 |
Current CPC
Class: |
H01Q
13/28 (20130101); H01P 3/00 (20130101) |
Current International
Class: |
H01Q
13/20 (20060101); H01Q 13/28 (20060101); H01P
3/00 (20060101); H01p 003/16 (); H01q 013/06 ();
H01p 003/12 () |
Field of
Search: |
;333/95S,95R,84M
;343/78S,785 ;29/600 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
barlow, H. E. M., "A Method of Changing the Dominant Mode in a
Hollow Metal Waveguide & its Application to Bends," IEE Vol.
106B Supp. 13, 1959, pp. 100-105 .
Griemsmann et al., "A Low-Loss H-Guide for Millimeter Wavelengths,"
Proc. of the Symposium on Millimeter Waves, N.Y., N.Y. 3-31 to 4-1,
2-59, Polytechnic Press, 1960, pp. 543-562 .
Duhamel et al., "Launching Efficiency of Wires & Slots for a
Dielectric Rod Waveguide" MTT-6, 1958, pp. 277-284 .
Duncan et al., "A Technique for Controlling the Radiation from
Dielectric Rod Waveguides" AP-5, 1957, pp. 284-289 .
Reindel, J., "The H-Guide-A Useful Waveguide for Millimeter Waves"
Electronic Defense Lab. Tech. Memo No. EDL-M377 1961, pp. 7, 18,
20, 22, 24, 31, 38. .
Lewin, L., "Miniaturization of Microwave Assemblies" MTT-4, 1956,
pp. 261-262 .
Schlesinger et al., "Dielectric Image Lines," MTT-6, 1958, pp.
291-299 .
Craven et al., "The Design & Testing of Integrally Constructed
Wave Guide Asemblies," IEE Vol. 106B, 1959, pp. 321-334 .
Reindel, J. "The H-Guide-A Useful Waveguide for Millimeter Waves,"
Electonic Defense Lab Tech. Memo No. EDL-M377, 1961 pp. 1-6, 17,
21-23, 30 .
MacFarlane, GG, "Surface Impedange of an Infinite Parallel-Wire
Grid at Oblique Angles of Incidence," JIEE Vol. 93 Pt. IIIA p.
1523-1527, 1946 .
Tischer, F. J."Properties of the H-Guide at Microwaves &
Millimeter Waves", IRE Wescon Conv. Record, 1958, Vol. PII pp 4-12
.
Tischer, F. J., "H-Guide with Laminated Dielectric," Pro. IEEE
5-1969, pp. 820-821 .
Nagelberg, E. R., "Dispersion Characteristics of an Array of
Parasitic Linear Elements," MTT-14 No. 8, 8-1966, pp. 391-396 .
Goodall et al., "Transmission of Electromagnetic Waves Through Wire
Gratings," The Marconi Review, 2nd Quarter 1959, pp. 91-98 .
Watson, W. H., "The Physical Principles of Waveguide Transmission
& Antenna Systems," Oxford U. Press, 1947, pp. 63-70 & Ref.
page .
Kraus, J. D. "Electromagnetics," McGraw-Hill, 1953, pp. 445-451
.
Reynolds et al., "Yagi Transmission Lines," IEEE Wescon Technical
Papers, Vol. 7, PT.I, 1963, pp. 1-7.
|
Primary Examiner: Rolinec; Rudolph V.
Assistant Examiner: Punter; Wm. H.
Claims
I claim to have invented:
1. A waveguide for electromagnetic waves comprising at least two
juxtaposed dielectric materials of different dielectric constants,
one of which is a slab and another of which extends away from both
faces of the slab, said slab being oriented generally perpendicular
to the direction of polarization of said waves, said dielectric
materials taken together constituting means for carrying the
electromagnetic waves as surface waves with part of said waves
traveling in said slab,
and wave guiding means comprising at least two rows of many
elongated conducting members, each such member being embedded in
said slab and extending through the slab and away from both sides
of the slab and arranged generally parallel to each other member of
the same row transverse to the slab, each row constituting
reflecting means to form collectively a waveguide so that the waves
traveling along the waveguide bounce back and forth between the
rows, each of the conducting members in the same row being so
closely spaced to each adjacent conducting member as to maintain
the major energy flow between the rows, said dielectric slab
extending between conducting members of the same row and beyond the
rows forming the waveguide.
2. A waveguide as defined in claim 1 in which the conducting
members separately extend at least one wavelength away from the
slab.
3. A waveguide as defined in claim 1 in which said slab is thicker
between said rows of conductors than it is beyond said rows.
4. A waveguide as defined in claim 1 including means for launching
the said polarized electromagnetic waves into the waveguide with
the direction of polarization generally perpendicular to the slab,
the conducting members being generally perpendicular to the
slab.
5. A waveguide as defined in claim 1 including a metallic base
plate attached, on one side of the slab, to the outer ends of the
conducting members.
6. A waveguide as defined in claim 1 in which the spacing between
some of the conducting members is increased to allow energy to leak
out of the waveguide.
7. A waveguie as defined in claim 6 having a second waveguide
positioned to receive the energy that leaks out between the members
of increased spacing, said second waveguide comprising two spaced
rows of parallel conducting members in said dielectric slab means,
the space between rows being interconnected with the first
waveguide at the location of said increased spacing.
8. A waveguide as defined in claim 1 in which the height of the
elongated conducting members, as measured from the surface of the
slab, progressively decreases to form an antenna.
9. A component of a circuit comprising at least one section of a
waveguide as defined in claim 1.
10. A plurality of components mounted on a single continuous
dielectric slab comprising at least one section of waveguide as
defined in claim 1.
11. A plurality of components mounted on a single slab with the
waves guided between at least two components by a section of
waveguide as defined in claim 1.
Description
BACKGROUND OF THE INVENTION
The invention pertains to waveguides, to electric components such
as antennas which may be constructed upon the principles of
waveguides, and to electric circuits having components
interconnected by waveguides.
In the frequency range of microwaves, hollow pipes, known as
waveguides, are frequently used for the transmission of energy
between the various components of microwave systems and as
fundamental elements of these components. Using this approach, the
metallic structures of more complex microwave circuitry are
difficult and expensive to manufacture. Microstrips transmission
lines were developed in recent years to simplify the design and the
production of such circuitry used in radars and communications
equipment. The microstrip circuitry basically consists of a
dielectric slab which is completely covered on the bottom surface
with an electrically conductive coating which represents a ground
plane. Narrow conducting strips on top of the dielectric slab
represent the actual transmission-line sections between the
individual components of the circuitry. Shorted and open-ended
strip-type transmission line sections also form elements of
components such as inductances, capacitances, and resonant
circuits. The strip structure on top of the dielectric slab is
commonly formed starting with a completely coated surface by
etching away the undesired parts. This leaves the narrow conducting
strips which are separated from the conducting ground plane by the
dielectric slab. Complete circuitry can then be designed to be
carried on top of a single dielectric slab.
In the high frequency region of microwaves above possibly 15 GHz
(15 kilomegacycles per second), commonly termed "millimeter-wave
region", the microstrip lines become rather lossy. This is due to
the decrease of the skin depth and the increase of the surface
resistance on conducting surfaces with increasing frequency and due
to the simultaneously increasing loss tangent of the dielectric
slab. Both effects cause a considerable increase of the attenuation
of microstrip lines at millimeter-wave frequencies. As a
consequence, the energy losses along the line sections become
appreciable and the characteristics of the components become
altered by the losses such that they do not longer perform
satisfactorily. A typical example is the Q-value of circuit
elements which becomes so low that filters and resonators have
unsatisfactory characteristics. As a consequence, waveguides in the
form of hollow pipes have to be used in the millimeter-wave regions
which interconnect the various components of the circuitry and
represent the basic elements of these components. The various
components and transmission line sections are coupled together by
coupling elements such as coupling flanges which often introduce
discontinuities which in turn cause reflections and losses of
energy. Such circuitry occupies often relatively large volumes of
space and is usually expensive to manufacture.
SUMMARY OF THE INVENTION
A main objective of the invention is to modify or control the path
of electromagnetic waves, and to provide a simple and inexpensive
device for accomplishing that end.
It is the objective of the present invention to provide a waveguide
which permits the integrated design of complete circuitry in one
unit and eliminates coupling elements between the components of the
circuit.
It is also an objective to provide a waveguide which, having the
precedingly noted advantages, has simultaneously lower losses than
those obtained in corresponding structures of prior art such as
microstrip lines.
The invention has as an additional object the provision of improved
electrical components such as antennas in those cases when the
components can be constructed according to the principles
applicable to waveguides.
It is a further object of the invention to provide an improved
electrical circuit of the type in which the components are
interconnected by waveguides.
The invention in its broadest aspects utilizes a row of elongated
conducting elements projecting from a dielectric slab for modifying
the path of electromagnetic waves polarized in a direction
generally parallel to said elements.
According to the invention, the waveguide, which usually is part of
a more complex millimeter-wave circuit, is composed in its basic
form of a dielectric slab with two rows of parallel metallic posts.
The posts may take various shapes such as rods, strips, etc. The
posts run through the slab, are oriented with their axes generally
perpendicular to the slab, and project out evenly for more than a
wave length on both sides. The distance between the two rows is
usually equal to the width of a standard rectangular waveguide for
the same frequency range. The posts of each row are as close as the
mechanical strength of the structure permits. If electromagnetic
waves are excited in the region between the two rows of the
electrically conducting posts with the E-field parallel to the
posts, surface waves travel along the dielectric between the two
rows of posts. The field-strength amplitudes associated with these
surface waves decrease exponentially in the direction from the slab
on both sides. The surface waves are bounced back and forth
laterally between the two rows of posts in a similar manner as
between the side walls in a standard rectangular waveguide carrying
transverse electric wave modes (TE.sub.01). Since the electric
field vector of the waves is parallel to the conducting posts, the
leakage between the posts which represent a wire grid can be kept
relatively small. The waveguide behaves generally similar to an
open waveguide known under the name "H-guide". Such an H-guide,
which has the cross-section of an H, consists of two parallel
conducting strips with a centrally located dielectric slab in
between. The two strips form the vertical legs of the H and the
dielectric slab the horizontal bar in the cross-sectional
configuration. Since the fields decrease exponentially toward the
lower and upper openings, the radiation losses can be kept
small.
In a waveguide according to the invention, the two rows of posts
have a function similar to that of the solid sidewalls of the
H-guide, namely, to reflect and to confine the waves in the lateral
direction. The posts allow the design of complex millimeter-wave
circuitry on a single dielectric slab. They confine the waves on
the slab along prescribed paths and are essential elements of the
components formed by sections of the waveguide. Modern production
methods typical in the plastics industry make the outlined
structure easily adaptable to the mass production of
millimeter-wave circuitry. Other objects, advantages, and the
usefulness in circuit design, will become apparent in the following
detailed descriptions in relation to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a section of a waveguide according
to the invention in its basic form.
FIG. 2 is a perspective view of another embodiment of the invention
where metal strips are used to form the side walls which confine
the waves in lateral directions.
FIG. 3 is a cross-sectional view of a modified form of the
waveguide. In this form there is increased thickness of the
dielectric slab in the region between the rows of posts.
FIG. 4 is a cross-section of another modified form of the
waveguide. In this form there is a conducting plate placed parallel
to the dielectric slab on the bottom with the posts attached to the
plate and carrying the total circuit structure.
FIG. 5 is a top view of a directional coupler utilizing my novel
waveguide principle.
FIG. 6 is a perspective view of an antenna based upon the
principles of the invention.
FIG. 7 is a perspective view of a receiver circuit designed on a
single slab by use of the waveguide according to the invention.
FIG. 8 is a cross-sectional view of a modified arrangement of the
slab and posts.
With reference to the drawings shown of sections of waveguides and
their applications, it will be realized that these figures show a
few examples only. Those skilled in the art may design similar and
modified structures and great varieties of components based on the
concept of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
A waveguide module according to the present invention is shown in
FIG. 1. It is composed of a dielectric slab 10 and of two parallel
rows of metallic posts 11 and 12 crossing the slab 10 with their
axes near to normal to the slab. The rows of posts serve as
reflectors which confine waves launched into or generated in the
region between the posts to this region and force them to travel
along the path prescribed by the posts as indicated in FIG. 1 by
the arrow. FIG. 1 also shows as an example the launching of the
waves by a dipole antenna 9. The waves are polarized electrically
with their E-vector parallel to the posts. They are surface waves
with their field amplitudes decreasing exponentially above and
below the dielectric slab in the region between the rows of posts.
By proper choice of the height of the posts, only a small fraction
of the power (perhaps 1/100 or 1/1000) is carried along the guide
above and below the end plane of the posts. The distance between
the two rows of posts is about the same as or larger than that
between the sidewalls of standard rectangular waveguides for the
same frequency range (equal or larger than 0.6 .lambda..sub.o,
.lambda..sub.o = free space wave length). The dielectric slab 10 of
the figure may be just a part of a larger slab and the guide shown
just a part of a waveguide system which forms a more complex
millimeter-wave circuit. By this approach, components, such as
power dividers, directional couplers, filters, resonators, or other
components, which contain waveguide sections, can be designed as
parts of an integrated circuit placed on a single dielectric
slab.
Referring to FIG. 2, there is shown, as another example of the
embodiment of the invention, a waveguide section with two parallel
rows of metallic strips 13 and 14 which confine the waves to the
region between the strips and make them travel along a prescribed
path along the dielectric slab 10. The section of waveguide may be
again a part of a more complex circuit. It will be realized that
the posts which form the two sidewalls of the guide may have other
cross sections than those shown in FIGS. 1 and 2. Elliptical and
square cross-sectional configurations are examples. The two
reflector sidewalls may also consist of double and multiple rows of
wires or equivalent elements. The single elements crossing the
dielectric slab may also be interconnected mechanically and
electrically near their ends and bent to increase the mechanical
strength of the structure. Since the fields decrease exponentially
from the slab toward the upper and lower openings, the structural
form, at a distance from the dielectric slab, of the two rows of
posts have a minor effect on the basic field configuration of the
surface waves guided along the slab.
The embodiment illustrated in FIG. 3 shows a cross-sectional view
of the waveguide with two longitudinal dielectric strips 15 and 16
added between the posts on top and bottom of the dielectric slab.
The strips cause an increase of the thickness of the dielectric
slab in the guide which in turn causes a reduction of the guide
wavelength and corresponding reduction of the velocity of the waves
traveling in the guide. This reduction reduces the already small
leakage of the energy sidewards through the reflecting rows of
conducting posts. This can be understood if one realizes that the
leakage is practically zero if the guide wavelength and wave
velocity are equal to or smaller than the wavelength and velocity
for the surface waves outside the guide respectively. Such measures
are important to obtain high Q-values in shorted sections of the
guide used as resonators and in filters. The increase of the
thickness of the dielectric between the posts may be obtained also
directly during the manufacturing process of the waveguide instead
of by the addition of strips as indicated in the example of FIG. 3.
It is also noted that the dielectric slab may be composed of layers
of dielectrics with different values of the permittivity in the
form of a laminated-dielectric slab and that the air space above
and below the slab may be filled with a foamed dielectric with a
permittivity approaching that of air.
FIG. 4 shows a cross-sectional view of an arrangement employing a
metal plate 17 with good electrical conductivity, as bottom plane
which carries the entire circuit. The two rows of posts or wires
are fastened in the plate to give the waveguide structure
particular mechanical stability. The basic character of the surface
wave propagation along the dielectric slab 10 between the posts 11
and 12 remains practically unchanged by this measure.
FIG. 5 illustrates as an example the application of the invention
in a directional coupler. The directional coupler may be a part of
a more complex circuit which is designed to operate on a single
dielectric slab. The part of the dielectric slab on which the
coupler is located is indicated in the figure by 10. Two pairs of
rows of posts each one composed of posts 11 and 12 form two
waveguides. One is the main guide indicated by I and the other the
secondary guide indicated by II. Both guides have a common sidewall
18 in the form of posts. The spacing between the posts and/or the
length of, the posts forming said common sidewall, vary in such a
manner that a desirable distribution of coupling is obtained
between the main guide I and the secondary guide II for forming a
directional coupler. The example of FIG. 5 shows that the
waveguides shown in the preceding figures lead to simple structures
for millimeterwave components.
As a further example of applications, an end-fire antenna is
illustrated in FIG. 6. The figure shows an antenna section
containing two antenna elements of an array. The two elements are
composed of two waveguide sections, such as are described in FIGS.
1 to 4, on a common dielectric slab 10. Each element has rows of
posts 11 and 12. The lengths of the posts are tapered toward the
edge 60 of the dielectric slab 10 as indicated in the figure. This
causes gradual radiation of the energy, carried between the rows of
posts 11 and 12 along the slab 10 in the waveguide region, beyond
the edge 60 of the slab in the direction indicated in the figure by
the arrows. The distance between the rows of posts may increase
toward the rim similar to the increase of the width in horn
antennas.
FIGS. 5 and 6 are indicative to those skilled in the art that the
invention as described may be applied to the design of all most
common components and may be used for the design of complete
millimeter-wave circuitry. The circuits may include waveguide
cavities containing active solid state elements, power dividers,
directional couplers, filters, mixer elements, below cutoff
attenuators, and even the antennas. The simplicity of the waveguide
structure permits simple and economical manufacturing by mass
production techniques of complicated circuitry without coupling
elements on a simple dielectric slab.
FIG. 7 shows a radio receiver circuit. The circuit is designed on a
single dielectric slab 10 with rows of conducting posts 11 and 12
as elements of the components and of the waveguide sections
connecting the components. The components are: First, a two-element
receiving-type antenna 19 each element constructed according to
FIG. 6. The antenna 19 is located adjacent the edge of the
dielectric slab 10. Secondly, an H-lane T-section of waveguide 20
combines the energies coming from the two antenna elements.
Thirdly, a filter 21, composed of two resonators, in the form of
shorted waveguide sections, receives the energy from the coupler
20. Coupling between the resonators and to the connecting
waveguides is achieved through the gaps between the posts of the
transverse grid walls. Finally, the output of the filter is fed via
the novel waveguide of this invention to a detector 20 which also
can be incorporated in a shorted post-type waveguide section.
FIG. 8 is a cross-sectional view of one form of the invention in
which the posts 11a and 12a are not exactly parallel but are
generally parallel, and also they depart somewhat from a
perpendicular relation with slab 10. For best results they should
be parallel to each other and perpendicular to slab 10 but some
deviation (for example, as illustrated in FIG. 8) is within the
broader aspects of the invention.
In all forms of the invention the posts of any given row should be
as close together as practicable except when it is desired to allow
some of the energy to pass out of the waveguide as, for example, in
the case of sidewall 18 of FIG. 5. Preferably, the spacing between
posts should not exceed .lambda..sub.o /8.
The height of the posts should be on the order of one wavelength,
as measured from the slab 10, although greater heights will also
work well.
From the foregoing, it will be apparent to those skilled in the art
that electrical circuit components may be constructed using
parallel rows of posts, and moreover, that electrical circuits
interconnected by the post-type waveguides are not only more easily
manufactured but function in a new and improved manner.
In each form of the invention of the drawings, a dielectric
material such as air is located between the rows of posts such as
11 and 12 and above or below the solid dielectric material shown.
Preferably the dielectric material, such as air, which is above and
below the solid dielectric material shown, has a lower dielectric
constant than the solid dielectric material (such as 10) shown.
It is obvious that many other modifications and variations of the
present invention are possible based on its previously outlined
basic concept. It is understood that equivalents apparent to one
skilled in the art after being exposed to the concept outlined
above are also covered.
* * * * *