U.S. patent number 3,864,679 [Application Number 05/347,506] was granted by the patent office on 1975-02-04 for antenna system for radiating doppler coded pattern using multiple beam antenna.
This patent grant is currently assigned to Hazeltine Corporation. Invention is credited to Peter W. Hannan, Harold A. Wheeler.
United States Patent |
3,864,679 |
Hannan , et al. |
February 4, 1975 |
ANTENNA SYSTEM FOR RADIATING DOPPLER CODED PATTERN USING MULTIPLE
BEAM ANTENNA
Abstract
Disclosed is an antenna system for radiating a frequency coded
or "Doppler" pattern of wave energy into a region of space using a
multiple-beam antenna unit. The system radiates a pattern in which
the radiated frequency varies as a function of angular direction
from the antenna unit. The system uses an antenna unit capable of
radiating simultaneous multiple beams and having a separate input
port associated with each beam. The frequency coded pattern is
achieved during a time period by simultaneously supplying wave
energy signals having a varying phase in relation to each other to
the antenna input ports.
Inventors: |
Hannan; Peter W. (Smithtown,
NY), Wheeler; Harold A. (Smithtown, NY) |
Assignee: |
Hazeltine Corporation
(Greenland, NY)
|
Family
ID: |
23363978 |
Appl.
No.: |
05/347,506 |
Filed: |
April 3, 1973 |
Current U.S.
Class: |
342/405 |
Current CPC
Class: |
G01S
1/40 (20130101); H01Q 25/007 (20130101); H01Q
3/34 (20130101) |
Current International
Class: |
H01Q
3/30 (20060101); G01S 1/40 (20060101); G01S
1/00 (20060101); H01Q 25/00 (20060101); H01Q
3/34 (20060101); G01s 001/38 () |
Field of
Search: |
;343/16D,113DE,1SA,854 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Wilbur; Maynard R.
Assistant Examiner: Berger; Richard E.
Claims
What is claimed is:
1. An antenna system for radiating wave energy into a desired
region of space during a selected time period in a desired
radiation pattern, wherein the frequency of said radiated energy
within said region of space varies with at least one of the
components of angular direction from said antenna system
comprising:
an antenna unit capable of radiating a plurality of beams in
different directions within said region of space from a common
aperture, and having a plurality of wave energy input ports such
that each of said ports corresponds to one of said beams;
and means for simultaneously supplying a plurality of wave energy
signals during said time period, one to each of said ports of said
antenna unit, each of said wave energy signals having a phase,
measured with respect to the phase of the wave energy signal
supplied to the port corresponding to an adjacent antenna beam,
which varies during said time period between a predetermined pair
of values, said variation being less than 360.degree. and the sense
of said variation being alike for pairs of antenna ports
corresponding to similarly adjacent beams;
whereby when said signals are supplied to said antenna ports, said
antenna radiates said desired radiation pattern.
2. An antenna system for radiating wave energy into a desired
region of space during a selected time period in a desired
radiation pattern, wherein the frequency of said radiated energy
within said region of space varies with at least one of the
components of angular direction from said antenna system
comprising:
an antenna unit capable of radiating a plurality of beams in
different directions within said region of space from a common
aperture, and having a plurality of wave energy input ports such
that each of said ports corresponds to one of said beams;
means for individually controlling the phase of wave energy signals
supplied to each of the ports of said antenna unit such that each
of said wave energy signals has a phase, measured with respect to
the phase of the wave energy signal supplied to the port
corresponding to an adjacent antenna beam, which varies during said
time period between a predetermined pair of values, said variation
being less than 360.degree. and the sense of said variation being
alike for pairs of antenna ports corresponding to similarly
adjacent beams;
and means for simultaneously supplying wave energy signals during
said time period to said antenna ports via said phase control
means;
whereby when said wave energy signals are controlled by said phase
control means and supplied to said antenna ports, said antenna
radiates said desired radiation pattern.
3. An antenna system as specified in claim 2 wherein each of said
wave energy signals is controlled to have a phase which varies
linearly with time between said predetermined pair of values.
4. An antenna system as specified in claim 2 wherein said wave
energy signals are supplied to the ports of said antenna during a
succession of said periods.
5. An antenna system as specified in claim 2 wherein said means for
controlling the phase of the supplied wave energy signals comprises
a plurality of phase shifters and means for controlling said phase
shifters.
6. An antenna system for radiating wave energy into a desired
region of space during a selected time period in a desired
radiation pattern wherein the frequency of said radiated energy
within said region of space varies with at least one of the
components of angular direction from said antenna system,
comprising:
an antenna unit capable of radiating a plurality of beams in
different directions within said region of space from a common
aperture and comprising means for focusing incident wave energy and
a plurality of feed elements, each having a wave energy input port,
for illuminating said focusing means with wave energy patterns such
that each of said feed elements corresponds to one of said
beams;
means for individually controlling the phase of wave energy signals
supplied to each of the ports of said antenna unit such that each
of said wave energy signals has a phase, measured with respect to
the phase of the wave energy signal supplied to the port
corresponding to an adjacent antenna beam, which varies during said
time period between a predetermined pair of values, said variation
being less than 360.degree. and the sense of said variation being
alike for pairs of antenna ports corresponding to similarly
adjacent beams;
and means for simultaneously supplying wave energy signals during
said time period to said ports via said phase control means;
whereby when said wave energy signals are controlled by said phase
control means and supplied to said ports, said antenna unit
radiates said desired radiation pattern.
7. An antenna system for radiating wave energy into a desired
region of space during a selected time period in a radiation
pattern wherein the frequency of said radiated energy within said
region of space varies with at least one of the components of
angular direction from said antenna system comprising:
an antenna unit capable of radiating a plurality of beams in
different directions within said region of space from a common
aperture and comprising a parabolic cylindrical reflector for
focusing incident wave energy and a plurality of feed elements,
each having a wave energy input port, for illuminating said
reflector with wave energy patterns such that each of said feed
elements corresponds to one of said beams;
a number of phase shifters equal to the number of said feed
elements for individuallly controlling the phase of wave energy
signals supplied to each of the ports of said antenna unit;
means for controlling said phase shifters such that the phase of
wave energy signals supplied to each of said phase shifters is
shifted to a phase, measured with respect to the phase of the wave
energy signal supplied to the port corresponding to an adjacent
antenna beam, which varies during said time period between a
predetermined pair of values, said variation being less than
360.degree. and the sense of said variation being alike for pairs
of antenna ports corresponding to similarly adjacent beams;
and means for simultaneously supplying wave energy signals during
said time period to said ports via said phase shifters;
whereby when said wave energy signals are controlled by said phase
shifters and supplied to said ports, said antenna unit radiates
said desired radiation pattern.
8. An antenna system for radiating wave energy into a desired
region of space during a selected time period in a desired
radiation pattern wherein the frequency of said radiated energy
within said region of space varies with at least one of the
components of angular direction from said antenna system,
comprising:
an antenna unit capable of radiating a plurality of beams in
different directions within said region of space from a common
aperture and comprising an array of antenna elements, a plurality
of wave energy input ports and means for coupling each of said
ports to said elements such that each of said ports corresponds to
one of said beams;
means for individually controlling the phase of wave energy signals
supplied to each of said antenna ports such that each of said wave
energy signals has a phase, measured with respect to the phase of
the wave energy signal supplied to the port corresponding to an
adjacent antenna beam, which varies during said time period between
a predetermined pair of values, said variation being less than
360.degree. and the sense of said variation being alike for pairs
of antenna ports corresponding to similarly adjacent beams;
means for simultaneously supplying wave energy signals during said
time period to said antenna ports via said phase control means;
whereby when said wave energy signals are controlled by said phase
control means and supplied to said antenna ports, said antenna unit
radiates said desired radiation pattern.
9. An antenna system, as specified in claim 8 wherein the means for
coupling said antenna ports to said elements comprises a matrix of
transmission lines and couplers.
10. An antenna system for radiating wave energy into a desired
region of space during a selected time period in a desired
radiation pattern, wherein the frequency of said radiated wave
energy within said region of space varies with at least one of the
components of angular direction from said antenna system,
comprising:
an antenna unit capable of radiating a plurality of beams in
different directions within said region of space from a common
aperture and comprising a linear array of antenna elements, spaced
from each other by substantially equal distances, a number of wave
energy input ports, equal to the number of antenna elements, and a
Bulter Matrix for coupling each of said ports to all of said
elements, such that each of said ports corresponds to one of said
beams;
a number of phase shifters, equal to the number of said ports for
individually controlling the phase of wave energy signals supplied
to each of the ports of said antenna unit;
means for controlling said phase shifters such that the phase of
wave energy signals supplied to each of said phase shifters is
shifted to a phase, measured with respect to the phase of the wave
energy signal supplied to the port corresponding to an adjacent
antenna beam, which varies during said time period between a
predetermined pair of values, said variation being less than
360.degree. and the sense of said variation being alike for pairs
of antenna ports corresponding to similarly adjacent beams;
and means for simultaneously supplying wave energy signals during
said time period to said ports via said phase shifters;
whereby when said wave energy signals are controlled by said phase
shifters and supplied to said ports, said antenna unit radiates
said desired radiation pattern.
11. An antenna system as specified in claim 6 wherein said
predetermined pair of values for the phase of the wave energy
supplied to each of said ports comprises a first phase value
selected to cause the wave energy radiated by all of said feed
elements to form a phase front for illuminating a first selected
area on said focusing means and a second phase value selected to
cause the wave energy radiated by all of said feed elements to form
a phase front for illuminating a second selected area on said
focusing means.
12. An antenna system as specified in claim 11 wherein each of said
wave energy signals is controlled to have a phase which varies
linearly with time between said predetermined pair of values.
13. An antenna system as specified in claim 7 wherein said
predetermined pair of values for the phase of wave energy supplied
to each of said ports comprises a first phase value selected to
cause the wave energy radiated by all of said feed elements to form
a phase front for illuminating a first selected area on said
reflector and a second phase value selected to cause the wave
energy radiated by all of said feed elements to form a phase front
for illuminating a second selected area on said reflector.
14. An antenna system as specified in claim 13 wherein said first
and second selected areas on said reflector are displaced from each
other in a direction which is perpendicular to the focal axis of
said reflector.
15. An antenna system as specified in claim 14 wherein each of said
wave energy signals is controlled to have a phase which varies
linearly with time between said predetermined pair of values.
16. An antenna system as specified in claim 7 wherein said wave
energy signals are supplied to the ports of said antenna during a
succession of said periods.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
The present invention relates to antenna systems radiating Doppler
coded patterns using multiple beam antennas, one form of which is
described in co-pending U.S. application Ser. No. 347,505, filed
Apr. 3, 1973, entitled "Antenna System For Radiating Multiple
Planar Beams," which is assigned to the same assignee as the
present application.
BACKGROUND OF THE INVENTION
This invention relates to systems for determining the angular
position of a target with respect to a reference location. In
particular this invention relates to systems which use a frequency
coded pattern to perform angle measurement, also known as "Doppler"
systems. In a Doppler system an antenna radiates wave energy into a
region of space in a pattern wherein the frequency of radiation
varies with one of the angular components of direction from the
antenna. Frequency coded radiation has in the past been achieved by
radiating wave energy sequentially from the individual antenna
elements of an array. This causes apparent motion of the radiation
source, resulting in a "Doppler" frequency shift which depends on
the relative angle of the target with respect to the antenna.
Some deficiencies associated with the sequentially excited array
antenna for generating Doppler signals are difficulty in
controlling beam shape and complexity in construction. A multiple
beam antenna radiating a different frequency on each beam would
appear to be an attractive method for radiating a Doppler coded
pattern. This method could use a simpler antenna unit and have
better control over pattern shape and coding. An attempt to
continuously radiate different frequencies on the various beams of
a multiple beam antenna would result in random interference between
the radiated signals, resulting in widely varying signal amplitude
and failure of coding.
SUMMARY OF THE INVENTION
It is an object of this invention, therefore, to provide a new and
improved antenna system for radiating a Doppler pattern into a
region of space from a multiple beam antenna.
It is a further object of this invention to provide such a system
wherein the radiated signal has a substantially constant amplitude
versus time characteristic during a time period.
It is a still further object of this invention to provide such a
system wherein the radiated pattern can be shaped to coincide with
the desired region of space.
In accordance with the invention, there is provided an antenna
system for radiating wave energy into a desired region of space in
a desired radiation pattern during a selected time period. The
desired pattern is one in which the frequency of the radiated
energy within the region of space varies with at least one of the
components of angular direction from the antenna system. The
antenna system includes an antenna unit capable of radiating a
plurality of beams in different directions within the region of
space from a common aperture, and having a plurality of wave energy
input ports, such that each of the ports corresponds to one of the
beams. The antenna system additionally includes means for
simultaneously supplying a plurality of wave energy signals during
the time period, one to each of the ports of the antenna unit, with
each of the signals having a phase, measured with respect to the
phase of the wave energy signal supplied to the port corresponding
to an adjacent antenna beam, which varies during said time period
between a predetermined pair of values, the variation being less
than 360.degree. and the sense of the variation being alike for
pairs of antenna ports corresponding to similarly adjacent beams.
When these signals are supplied to the antenna ports, the antenna
radiates the desired radiation pattern.
For a better understanding of the present invention, together with
other and further objects thereof, reference is had to the
following description taken in conjunction with the accompanying
drawings, and its scope will be pointed out in the appended
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is one embodiment of an antenna system constructed in
accordance with the present invention.
FIG. 2 is a diagram illustrating the phase of wave energy signals
used in conjunction with the FIG. 1 antenna.
FIG. 3 illustrates the operation of the FIG. 1 antenna.
FIG. 4 is an alternative embodiment of the present invention.
DESCRIPTION AND OPERATION OF THE FIG. 1 ANTENNA SYSTEM
The antenna system of FIG. 1 includes an antenna unit consisting of
a plurality of feedhorns 10a, b, c for illuminating a focusing
reflector 11. The feedhorns 10 are located near the focal axis of
the parabolic cylindrical reflector 11 and displaced from each
other such that wave energy from each feedhorn 10 illuminates the
reflector 11 and causes a beam to be radiated at a different angle
in space with respect to the antenna system. This type of antenna
unit is more fully described and covered by the above referenced
co-pending application.
Associated with each of the feedhorns 10 are corresponding wave
energy input ports 12a, b, c. Each of these input ports 12 are
connected to a corresponding one of the phase shifters 14a, b, c by
suitable transmission lines 13a, b, c. An oscillator 15 supplies
wave energy signals to a power divider 16. The wave energy signals
from the outputs of the power divider 16 are supplied to the phase
shifters 14. Varying phase control signals are generated by control
unit 17 and supplied to control inputs of the phase shifters 14.
Thus, the wave energy signals supplied to the phase shifters 14
have their phase shifted in relation to each other in accordance
with the phase control signals such that signals with varying phase
in relation to each other are supplied by transmission lines 13 to
the input ports 12 of the feedhorns 10.
The oscillator 15, power divider 16, phase shifters 14,
transmission lines 13 and control unit 17 together comprise means
for simultaneously supplying a plurality of wave energy signals,
one to each of the ports 12 of the antenna unit, with each of the
wave energy signals having a predetermined varying phase in
relation to any other of said signals.
Each of the feedhorns 10 in FIG. 1 is designed to illuminate the
reflector 11, which forms a common aperture. The antenna unit
radiates a beam for each of the feedhorns 10 in a direction which
is unique to each of the feedhorns by reason of the displacement of
the feedhorns 10 from each other as explained more fully in the
aforementioned copending application. Each of the input ports 12 of
the feedhorns 10 is therefore associated with an antenna beam.
Those skilled in the art will recognize that other types of
multiple beam antennas may be substituted for the antenna unit
shown in FIG. 1. The antenna must be capable of radiating a
plurality of beams in different directions within a desired region
of space from a common aperture, and have a plurality of wave
energy input ports such that each of the ports corresponds to one
of the beams. Antennas of this type may be conveniently referred to
as "Beamport" antennas.
The transmission lines 13 may be any type appropriate for use at
the operating frequency chosen for the antenna system. It is
important, however, in the FIG. 1 embodiment that these
transmission lines have a phase length in relation to each other
which is appropriate for supplying the wave energy signals to the
ports 12 with the required varying phase in relation to each
other.
The phase shifters 14 may be any type which is appropriate for the
frequency of the wave energy signals. Example of suitable phase
shifters are ferrite phase shifters and diode phase shifters, both
of which use phase control signals to vary their apparent
electrical length and thereby phase shift the wave energy signals.
The phase control signals supplied by the control unit 17 should be
signals appropriate for controlling the phase shifters 14 selected
for use in the antenna system. These signals may be digital logic
signals or analog signals according to the type of phase shifters
selected.
The oscillator 15 may be any suitable generator of wave energy
signals at the chosen operating frequency. The power divider may be
any of the commonly used types, well known in the art, such as
couplers, "T" junctions or reactive dividers.
It will be evident that other means may be used to supply the
necessary wave energy signals with a varying phase in relation to
each other. For example, phase control may be performed at a
different frequency than the radiated frequency and using frequency
converting devices, or by performing a digital or analog frequency
synthesis to generate the required signals. Phase control may also
be achieved by using mixing devices rather than phase shifters.
FIG. 2 illustrates typical varying phase of the signals supplied to
the input ports 12 of the FIG. 1 antenna. Phase is shown in
relation to the phase of signal "C," which would be supplied to the
input port 12c, for example. As is evident from the diagram, the
phase of the signals "A" and "B," which would be supplied to input
ports 12a and 12b, respectively, have a varying phase in relation
to the phase of the signal "C" and in relation to each other. As
shown in FIG. 2, the sense of phase variation for the signals
supplied to each port with respect to an adjacent port is alike for
pairs of antenna ports corresponding to similarly adjacent beams.
Consequently, signal "A," supplied to port 10a has a positive phase
variation with respect to signal "b" supplied to port 10b.
Likewise, signal "B" has a positive phase variation with respect to
signal "C" supplied to port 10c. The phase of the signals during a
period nominally varies linearly from a first predetermined phase
point for each of the signals to a second predetermined point for
each of the signals. The phase variation may depart from a linear
variation to account for particular characteristics of various
antennas such as defocusing or non-equal spacing of the feedhorns,
etc. The phase variation period may be continuously repeated as
shown in FIG. 2 to produce a substantially continuous frequency
coding.
It should be noted that during any particular period the effect of
the linear phase variation is to cause a frequency change in the
corresponding wave energy signal. However, it is not effective to
continuously supply wave energy signals of different frequency to
the input ports of the antenna to cause the desired radiation
pattern, because the phase relation necessary to prevent
interference of the signals in the various beams is only present
during a particular period. To prevent interference between
adjacent beams it is necessary that the phase between the signals
supplied to ports corresponding to adjacent beams never be such
that the adjacent beams are 180.degree. out of phase. Consequently,
the total phase variation between adjacent ports can never exceed
360.degree. and is usually much less than 360.degree..
Doppler frequency coding is most often associated with an antenna
which radiates energy from a moving radiation source. FIG. 3
illustrates a sectional view of the antenna unit used in the FIG. 1
antenna system. At the beginning of a period the phase of the wave
energy signals supplied to the feedhorns 10 combine when radiated
from the feedhorns to form a radiation phase front 18a which
proceeds in the direction 19a, to illuminate an area around the
point 20a on the reflector 11. During the period the phase of the
wave energy supplied to the feedhorns 10 varies, as shown in FIG.
2, causing the illuminated area to move vertically across the
reflector. At the end of the period the phase of the wave energy
signals supplied to the feedhorns 10 form the phase front 18b,
which proceeds in a direction 19b, to illuminate an area around
point 20b on the reflector. This process may be repeated for
several periods, causing the illuminated area on the reflector 11
to repeatedly move from the vicinity around the point 20a to the
vicinity around the point 20b. Points 20a and 20b are shown by way
of example in FIG. 3. The illuminated area may center around any
points on the section of the reflector. This motion of the
illuminated area on the reflector causes the antenna system to
radiate a pattern similar to a sequentially excited array wherein
the frequency of radiation varies with one of the angular
components of direction from the antenna.
The group of feedhorns 10 may be considered to be a phased array
for illuminating the reflector 11 and array design principles are
therefore applicable. The spacing between the feedhorns should be
chosen such that there will be no "grating lobes" on the reflector
when the feedhorns are excited by any of the phase relations
associated with a period. The number of feedhorns required is a
function of the angular region of space within which it is desired
to radiate the frequency coded pattern. A larger number of
feedhorns would cause a narrower illuminated area and hence a
larger angular region in which the frequency coded pattern would be
radiated. Other tradeoffs will be evident to those skilled in the
art. For example, the time duration of the phase variation period
is dependent on the amount of frequency shift desired in the
radiated pattern. The shape and size of the reflector 11 and
feedhorns 10 are dependent on the region of coverage and beamshape
desired. The use of other feed elements in place of feedhorns and
other means for focusing wave energy in place of a parabolic
reflector will be evident to those skilled in the art.
DESCRIPTION AND OPERATIONS OF THE FIG. 4 ANTENNA SYSTEM
FIG. 4 illustrates another embodiment of an antenna system
constructed in accordance with the present invention. In the FIG. 4
system, wave energy signals are supplied to the antenna ports 21a,
b, c, d by similar devices 14-17 as in the FIG. 1 antenna. The
principal difference is that the antenna unit in the FIG. 4
embodiment comprises an array of antenna elements 22 which are
coupled to the antenna ports 21 by a Bulter Matrix 23. The
properties of a Butler Matrix are well known in the art. Basically,
each of the input ports 21 is coupled to the antenna elements 22 by
the Bulter Matrix 23 such that wave energy signals supplied to each
of the ports 21 will be radiated by the elements 22 in a beam which
is in a direction unique to that port. Thus, the antenna unit in
the FIG. 4 embodiment has the same general characteristics as the
antenna unit in the FIG. 1 embodiment, that is, they are both
"Beamport" antennas, although different in form.
Wave energy signals having varying phase in relation to each other,
when simultaneously supplied to the antenna ports 21 in FIG. 4,
will cause wave energy signals to be sequentially supplied to the
elements 22 of the aperture in a manner resulting in an apparent
motion of the radiation source. This operation is evident because
of the nature of the transformation performed by the Bulter Matrix
23.
Other variations in antenna systems which embody the present
invention will be evident to those skilled in the art. Other
matrices can be used to provide the necessary multiple-beam,
multiple-port antenna function, including those which operate at a
different frequency than the desired frequency of radiation in
conjunction with devices for frequency conversion. Also, devices
which are not matrices of themselves, such as enclosed lenses, but
have the same properties by reason of transmission characteristics
can be used in an antenna system constructed in accordance with the
present invention.
In describing the various embodiments above, reference has been
made to transmitting antenna systems, but it will be recognized by
those skilled in the art that the principles of the present
invention can also be applied to receiving antenna systems.
Accordingly, the appended claims shall be construed as covering
both transmitting and receiving antenna systems regardless of the
descriptive terms actually used therein.
While there have been described what are at present considered to
be the preferred embodiments of this invention, it will be obvious
to those skilled in the art that various changes and modifications
may be made therein without departing from the invention and it is,
therefore, aimed to cover all such changes and modifications as
fall within the true spirit and scope of the invention.
* * * * *