Telecommunications – Carrier wave repeater or relay system – Portable or mobile repeater
Reexamination Certificate
2001-05-22
2004-06-01
Maung, Nay (Department: 2684)
Telecommunications
Carrier wave repeater or relay system
Portable or mobile repeater
C455S427000
Reexamination Certificate
active
06745004
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to a secondary DC power source for a satellite system and, more particularly, to a technique for using secondary DC power from a frequency generator on a satellite to provide secondary DC power to a low noise amplifier/frequency downconverter and a satellite beacon assembly.
2. Discussion of the Related Art
Various communications systems, such as certain cellular telephone systems, cable television systems, Internet systems, military communications systems, etc., make use of satellites orbiting the Earth to transfer signals. A satellite uplink communications signal is transmitted to the satellite from one or more ground stations, and then re-transmitted by the satellite to another satellite or to the Earth as a downlink communications signal to cover a desirable reception area depending on the particular use. The uplink and downlink signals are typically transmitted at different frequencies, are polarized and are coded. For example, the uplink communications signal may be transmitted at 30 GHz and the downlink communications signal may be transmitted at 20 GHz.
The satellite includes a satellite structure or bus that provides primary DC power. System components within the satellite, referred to as the satellite payload, include electrical components and systems that operate on secondary DC power, having a lower voltage than the primary DC power. For example, the primary DC power may be 50V and the secondary DC power may be 6.5V.
The satellite payload includes an antenna system having a configuration of antenna arrays that receive the uplink signals and transmit the downlink signals to the Earth. The antenna, signals received by the antenna arrays on a particular antenna channel are typically switched to another channel to be included on a downlink signal for one of a plurality of transmission antennas directed to different locations.
FIG. 1
is a schematic block diagram of a signal switching architecture
10
that provides signal switching on a satellite. The signal architecture
10
is a general depiction of this type of a system on a satellite, and it is intended to be exemplary only. The signal architecture
10
includes a series of channels
12
connected to four separate receive antennas
16
. Only one of the channels
12
will be discussed herein with the understanding that the other channels operate in the same manner. The channel
12
includes a waveguide input filter
14
that filters the received uplink signal to a bandwidth in which the desired signal is contained. The filtered signal from the antenna
16
is then sent to a low noise amplifier and frequency downconverter (LNA/DC)
18
where the signal is amplified and downconverted to a lower frequency suitable for the switching operation. The LNA/DC
18
receives a local oscillator (LO) signal from a frequency generator. The LNA/DC
18
includes redundant amplification and down converting components.
Each of the amplified and downconverted signals on each channel
12
is sent to a separate splitter
26
within an input multiplexer
28
. Each splitter
26
includes four outputs. The multiplexer
28
also includes a switch
30
in each channel
12
that receives an input signal from each of the splitters
26
so that the switch
30
can select which of the antennas
16
is to be connected to that channel. Therefore, all of the uplink signals for the four separate antennas
16
can be switched to any one of the channels
12
. The selected antenna's
16
downconverted signal or intermediate frequency is applied to a second bandpass filter
32
where it is further filtered to remove additional noise and further limit the bandwidth. The bandwidth of the filters
32
are set to a narrow frequency band so that a particular frequency from any one of the antennas
16
can be provided on any one of the channels
12
.
The multiplexer
28
further includes a plurality of transfer switches
34
that allow the signal on a particular channel
12
to be switched to another channel
12
. A careful review of the switches
34
show how five channels are provided from four antennas
16
. As is apparent, the center channel is a spare channel that is not connected to a bandpass filter
32
, and thus is a redundant channel. By switching the transfer switches
34
, the spare channel can be selectively connected to one of the two center channels in the multiplexer
28
.
A signal on each channel from the multiplexer
28
is applied to a test coupler
38
, and then to a channel amplifier (CAMP)
40
that provides both fixed gain and controlled gain for the signal. The signal from the amplifier
40
is then applied to a frequency upconverter (UC)
42
that frequency upconverts the downconverted frequency signal to the higher downlink frequency for transmission. The UC
42
also receives an LO signal from the frequency generator to provide the upconversion. The upconverted signal is then applied to a traveling wave tube (TWT) amplifier
44
that increases the power of the signal for transmission to the Earth. A power converter
46
receives primary satellite DC bus power (50V), and reduces the primary power to secondary DC power for each of the amplifier
40
, the UC
42
. It supplies a separate secondary DC voltage to the TWT amplifier
44
.
The amplified signal from the TWT amplifier
44
is applied to a transfer switch
50
within an output multiplexer
52
. The switches
50
receive the downlink signals from the five separate channels
12
, and select the signals on these channels to be on one of the downlink channels. The signals from the switches
50
are applied to a switching network
54
that provides high power waveguide switching. The switched signals from the switching network
54
provide four separate signals where each signal from a particular downlink channel is applied to each of three switch selectors
56
. Therefore, the switch selector
56
select one of the four channels to be output onto one of three separate downlink antennas
58
.
A challenge in satellite design and assembly is to minimize cost, size, weight, power and integration complexity. One area in which design complexity, weight and cost can be reduced is by reducing the requirement for multiple secondary power converters. In the known signal architecture of the type disclosed in
FIG. 1
, the LNA/DCs
18
would operate on secondary DC power. Thus, a power converter would be required to convert the primary satellite bus DC power to the secondary DC power suitable for the LNA/DCs
18
. A separate DC power converter could be provided for each one of the LNA/DCs
18
, or a single DC power converter could be provided for all four of the LNA/DCs
18
. Additionally, the amplifiers
40
and the UCs
42
also require secondary DC power that is provided in this example by the power converter
46
.
Further, in known satellite payload architectures, a stand alone secondary DC power converter is sometimes used to provide secondary DC power to the satellite beacon assembly that provides a downlink beacon signal to the Earth for calibration purposes. In those systems where a stand alone converter was not used for this purpose, the beacon assembly included an internal secondary power converter. Thus, because secondary DC power converters are heavy and require significant satellite space and resources, the several such converters typically required in satellite payload designs added significant cost and weight to the satellite.
What is needed is a secondary DC power conversion scheme on a satellite that reduces the number of secondary DC power converters needed to reduce the cost, size, weight and integration complexity of a satellite payload. It is therefore an object of the present invention to provide such a technique.
SUMMARY OF THE INVENTION
In accordance with the teachings of the present invention, a technique for providing secondary DC power to certain satellite payload components is disclosed that reduces the number of secondary DC power converters heretofore required in the art.
Lane Daniel R.
Martin Bridget M.
Maung Nay
Northrop Grumman Corporation
Perez Angelica
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