Communications: directive radio wave systems and devices (e.g. – Directive – Including a steerable array
Reexamination Certificate
2002-08-06
2004-05-18
Tarcza, Thomas H. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Directive
Including a steerable array
C342S373000
Reexamination Certificate
active
06738017
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a modular phased array antenna having irregular or random connections of beam signals to beam ports of each modular antenna assembly so as to provide improved beam-to-beam isolation.
BACKGROUND OF THE INVENTION
The costs of communications spacecraft are under downward pressures due to competition among spacecraft manufacturers, and also due to competition with other forms of communications. One way to reduce the cost of a communications spacecraft is the use of modularized spacecraft techniques. For example, U.S. Pat. No. 5,666,128 to Murray, et al., describes the use of array antennas that are modular, so that a spacecraft may have its antennas made up of standard subarrays mounted in a standardized structure. Likewise, U.S. Pat. No. 5,870,063 to Cherrette, et al., describes a spacecraft having antennas that are constructed with modular elements, for ready interchangeability and configuring.
A typical modular phased array antenna includes a number of antenna array modules or building blocks radiating a number of signal beams. Each beam signal is processed by beam specific electronics, then input to each antenna array module. In a traditional design, each beam is input to the same input port of each antenna array module. A problem arises with this design due to electromagnetic coupling among the paths within the antenna array module. In particular, electromagnetic coupling among the circuit paths of an antenna array module cause coupling of the beam signal on each circuit path to the circuit paths of every other beam signal in the antenna array module. This coupling effect is typically dependent upon the geometry and layout of the circuit paths in the antenna array module, with (in general) greater coupling occurring among circuit paths that are physically closer to each other and that are parallel to each other. A signal that is introduced due to electromagnetic coupling may be seen as an error signal introduced into the intended signal.
Due to the regular geometry of antenna array modules, the coupling of beam signals will tend to correlate from module to module. Since the antenna array modules are typically mass-produced, the coupling among signals in each antenna array module will be similar. Thus, the magnitude and phase of the coupling is repeatable from module to module. These correlated, coupled signals reinforce each other and produce a much greater error signal in each beam than would be produced by any one uncorrelated signal. The beam pattern for each beam signal will be the vector sum of the intended beam pattern for the beam signal and the intended beam pattern for each other beam signal path that receives power from the first beam signal by unintended coupling, attenuated by the isolation of the coupling path. Each coupled error signal will create a sidelobe in the beam pattern of the beam associated with that signal in the direction of the mainlobe of the intended beam pattern of the beam into which the signal has coupled. This may cause unacceptable interference.
While the magnitude of the coupled error signals may be reduced by increasing the isolation of the coupling paths, this is an expensive and weight-increasing solution. What is needed is a technique by which the error signals that are introduced into beam signals by electromagnetic coupling may be reduced without resorting to expensive and weight-increasing solutions.
SUMMARY OF THE INVENTION
The present invention is a modular phased array antenna that provides a reduction in the error signals that are introduced into beam signals by electromagnetic coupling. The invention is inexpensive to implement and does not cause an increase in weight or power consumption. The modular phased array antenna has irregular or random connections of beam signals to beam ports of each modular antenna assembly so as to provide improved beam-to-beam isolation.
In one embodiment of the present invention, a modular phased array antenna comprises a plurality of modular antenna assemblies, each modular antenna assembly having a plurality of beam ports, each beam port of a modular antenna assembly connected to a different beam signal, wherein the beam signals are irregularly connected to the beam ports relative to the modular antenna assemblies. The beam signals may be randomly connected to the beam ports relative to the modular antenna assemblies. The beam signals may be connected to the beam ports relative to the modular antenna assemblies so that vector sums of coupling coefficients of beam signal to beamformer paths is reduced compared to a regular connection of the beam signals to the beam ports relative to the modular antenna assemblies. The beam signals may be connected to the beam ports relative to the modular antenna assemblies so that vector sums of coupling coefficients of beam signal to beamformer paths is minimized.
In one embodiment of the present invention, the modular phased array antenna is a receiving antenna, which may comprise a plurality of modular antenna assemblies. Each modular antenna assembly may comprise a plurality of power combiners, each power combiner having an output connected to a beam port of the modular antenna assembly, and each power combiner having a plurality of inputs, a plurality of phase shift attenuators, each phase shift attenuator having an output connected to an input of a power combiner, and each phase shift attenuator having an input, a plurality of power dividers, each power divider having a plurality of outputs, each output connected to an input of a phase shift attenuator, and each power divider having an input, a plurality of amplifiers, each amplifier having an output connected to an input of a power divider, and each amplifier having an input, and a plurality of antenna elements, each antenna element having an output connected to an input of an amplifier.
In one aspect of the present invention, the modular phased array antenna may further comprise a plurality of driver amplifiers, each driver amplifier connected between a beam port of the modular antenna assembly and a power combiner output, each driver amplifier having an input connected to a power combiner output and having an output connected to a beam port.
In one aspect of the present invention, the modular phased array antenna may further comprise a plurality of power combiners, each power combiner having an output connected to a beam signal and having a plurality of inputs inputting the beam signal, each of the plurality of inputs connected to a beam port of a modular antenna assembly. The connections of the beam signals to the beam ports of the modular antenna assemblies may be randomly assigned. The connections of the beam signals to the beam ports of the modular antenna assemblies may be assigned so that vector sums of coupling coefficients of beam signal to beamformer paths is reduced compared to a regular connection of the beam signals to the beam ports relative to the modular antenna assemblies. The connections of the beam signals to the beam ports of the modular antenna assemblies may be assigned so that vector sums of coupling coefficients of beam signal to beamformer paths is minimized. The connections of the beam signals to the beam ports of the modular antenna assemblies may be hard-wired. The connections of the beam signals to the beam ports of the modular antenna assemblies may be provided by at least one of fiber optic cable, coaxial cable, or printed circuit board traces. The connections of the beam signals to the beam ports of the modular antenna assemblies may be configurable in software. The connections of the beam signals to the beam ports of the modular antenna assemblies may be provided by a switching matrix or other programmable connection device.
In one embodiment of the present invention, the modular phased array antenna is a transmitting antenna, which may comprise a plurality of modular antenna assemblies. Each modular antenna assembly may comprise a plurality of power dividers, each power divider having an input connected to a beam po
Lockheed Martin Corporation
Mull F H
Tarcza Thomas H.
Townsend and Townsend / and Crew LLP
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