Communications: radio wave antennas – Antennas – Wave guide type
Reexamination Certificate
2002-01-30
2004-01-13
Wilmer, Michael C. (Department: 2821)
Communications: radio wave antennas
Antennas
Wave guide type
C343S756000, C333S02100R
Reexamination Certificate
active
06677911
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to antennas for satellite-based communication systems, and more particularly to antenna feed assemblies capable of configuring the communication ports of an antenna at selected polarizations.
BACKGROUND OF THE INVENTION
In the past few years, there has been a significant increase in the number of satellite-based communication systems. As with other types of communication systems, however, there is a limited amount of bandwidth to handle this increase. For this reason, a technique known as frequency reuse is typically implemented. In this technique, signals used in communication with a satellite, (such as two receive signals or a transmit and receive signal), are oriented in polarization planes with respect to each other, so that both signals can reside on the same channel, (one in each plane). As such, the channel is used for communication of two signals as opposed to just one, thereby increasing the amount of information that may communicated on each channel of the frequency band. The signals may be either at the same polarization, (co-polarized), orthogonal to each other, (cross-polarized), or at a predetermined polarization difference.
Antennas used in frequency reuse applications, typically include a feed assembly for coupling either two receive waveguides or a transmit and receive waveguide to a common feedhorn, depending on the requirements for the antenna application. The orientation of the ports of the common waveguide for connecting the receive and transmit waveguides to the feed assembly determine the polarization for each waveguide. As an aid to understanding this concept,
FIGS. 1A and 1B
respectively illustrate cross- and co-polarization configurations of the ports of a common waveguide. Although not illustrated, the ports could be configured at any predetermined polarization by altering the orientation of the ports relative to each other.
FIG. 1A
illustrates an antenna feed assembly
10
with cross-polarization. The assembly includes a common waveguide
12
having a first end
14
for connection to the feedhorn of an antenna, not shown. The common waveguide also includes two ports,
16
and
18
, for connection to either two receive waveguides, two transmit waveguides, or a transmit and a receive waveguide. The ports,
16
and
18
, are rectangular in shape so as to receive or transmit only one polarization signal. As illustrated in
FIG. 1A
, the first port
16
has a longitudinal dimension
16
a
that extends in parallel with the longitudinal axis A of the common waveguide, and the second port
18
has a longitudinal dimension
18
a
that extends perpendicular to the longitudinal extension A of the common waveguide. In a cross-polarization configuration, the longitudinal dimension
16
a
of the first port
16
and the longitudinal axis A define a first plane extending vertically in
FIG. 1A
substantially bisecting the common waveguide. The longitudinal dimension
18
a
of the second port
18
and the longitudinal axis A define a second plane extending substantially horizontally in FIG.
1
A and perpendicular to the first plane. In this configuration, signals with one polarization are accepted by the first port
16
, while signals with an orthogonal polarization are accepted by the second port
18
. In a cross-polarization configuration, the common waveguide is typically referred to as an orthogonal mode transducer (OMT).
FIG. 1B
illustrates the first and second ports in a co-polarization orientation. In this instance, the longitudinal dimension
16
a
of the first port
16
and the longitudinal axis A define a first plane extending horizontally in
FIG. 1B
, and the longitudinal dimension
18
a
of the second port
18
and the longitudinal axis A define a second plane extending substantially horizontally in
FIG. 1B
such that the first and second planes are substantially coplanar. In a co-polarization configuration, the common waveguide is typically referred to as a diplexer.
Although these antennas provide proper orientations for operating with signals that are at different polarizations, there are some current problems with the manufacture and implementation of these antennas. Specifically, signal conventions for the transmission and reception of signals may vary in different areas of the world depending on the position of satellites and possible interference between different communication signals. For example, in some areas, the received signals propagate in a horizontal plane, and the transmitted signals propagate in a vertical plane, while in other areas of the world the communication signals are oriented in an opposite configuration. In light of this, antennas must either be individually manufactured for the different signal configurations, or the antennas must be configurable in the field to select the proper configuration of the wave-guides. To decrease cost, however, it is typically preferable to manufacture one antenna that can be reconfigured in the field based on the location and the application in which it is used.
With reference to FIGS
1
A and
1
B, for in-field configuration, the antenna feed assembly must be rotated so as to place the ports of the waveguides in proper polarization orientation with respect to the communication signals. For example, by rotating the feed assemblies of FIGS
1
A and
1
B by ninety (90) degrees R the waveguides are switched in polarization. To facilitate in-field configuration, many conventional systems include a flange
20
connecting the common waveguide
12
and to the feedhorn of the antenna. During configuration, the common waveguide, as well as receiver electronics
22
and transmitter
24
connected to the common waveguide, are all rotated to the proper polarization for the application in which the antenna is used.
Although in-field configuration decreases time and cost in manufacturing, there are still drawbacks to this conventional solution. Specifically, the transmitter of an antenna is typically an expensive portion of the overall cost of the antenna. Also, given the complexity of most transmitters, they are more susceptible to damage from mishandling. Designs such as those shown in FIGS
1
A and
1
B that require rotation of the transmitter during in-field configuration are thus less advantageous, as it is more likely that the transmitter of the antenna can be damaged.
In addition, some new antenna designs do not allow for rotation of both of the transmitter and receiver waveguides connected to the antenna feed assembly. Specifically, the assignee of the present application has designed a new antenna that advantageously reduces the overall size of the antenna and reduces the moment forces on the support structure of the antenna. This new antenna design places the transmitter or receiver electronics on the boom arm of the antenna, as opposed to an in-line configuration behind the feedhorn, making the antenna more compact. By attaching the transmitter or receiver to the boom arm in a fixed configuration, the antenna or receiver cannot be rotated with the common waveguide to reconfigure the polarization of the antenna in the field using conventional techniques. This newly designed antenna is described in U.S. patent application Ser. No. 09/797,012, filed Mar. 1, 2001, now U.S. Pat. No. 6,417,815, and entitled: ANTENNAS AND FEED SUPPORT STRUCTURES HAVING WAVEGUIDES CONFIGURED TO POSITION THE ELECTRONICS OF THE ANTENNAS IN A COMPACT FORM, the contents of which are herein incorporated by reference.
As such, an antenna feed assembly design is needed that allows for easy in-field configuration of the polarization of the waveguides of the antenna. Further, the antenna feed assembly should allow, the feed assembly to be rotated to place the antenna in proper polarization even though one of the waveguides connected to the feed assembly is in a fixed position.
SUMMARY OF THE INVENTION
As set forth below, the present invention provides antenna feed assemblies that overcome many of the deficiencies associated with configuring the waveguides of an a
Alston & Bird LLP
Prodelin Corporation
Wilmer Michael C.
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