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US H1,773 HGranted
Ultra-wideband active electronically scanned antenna
AssigneeUnited States of America
InventorsTheodore C. Cheston, H. Paris Coleman
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AssigneeUnited States of America
InventorsTheodore C. Cheston, H. Paris Coleman
Estimating the term…
The architecture of this invention makes multiple use of switched time-delay circuits to reduce the complexity of both series and parallel feed antenna arrays. Each time-delay circuit can give a delay that can be switched to values between 0 and 2d/c, where d is the inter-element spacing and c is the velocity of light. At the highest frequency of the series feed array, the elements are spaced by .lambda./2 to avoid grating lobes and the maximum delay corresponds to 360.degree. of phaseshift. When the time-delays are set half way (d/c), the various lines feeding the elements of the array at the aperture have bias delays that make them all equal in length, thereby giving a broadside beam, independent of frequency. At the highest frequency, the switchable time delay gives some excess in available delay. If additional excess time-delay is needed it can be obtained by increasing the time delay circuit range. Insertion loss is proportional to the number of bits used. This could become high in large antennas, however, this loss may be compensated by the addition of two-way amplification in the branch lines with an appropriate bias length adjustment. Also the insertion loss may be reduced by dividing the array into subarrays which are then combined by a series feed combiner network.
An apparatus for beamforming in a broadband antenna array having a plurality of antenna elements comprised of:
An apparatus for beamforming a broadband antenna array having a plurality of antenna elements comprised of:
An apparatus for beamforming a broadband antenna array having a plurality of antenna elements comprised of:
A method for beamforming in an antenna array having a plurality of antenna elements comprising the steps of:
Dependencies are inferred from the claim text.
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1. Field of the Invention
This invention deals with time-delay circuits utilized for beamforming in a phased array antenna system and more particularly to a phased array antenna system utilizing switched time-delay circuits to significantly reduce the complexity of time-delay beam steering.
2. Description of the Related Art
FIG. 1 is a schematic of the architecture for an ultra-wideband beam forming line source with a series feed having adjustable time delay modules having an odd number of antenna elements.
FIG. 1a is a schematic of the architecture for an ultra-wideband beam forming line source with a series feed having adjustable time delay modules having an even number of antenna elements.
FIG. 1b is a schematic of an adjustable time-delay module utilizing solid state components.
In the preferred embodiment 10, shown in FIG. 1, ultra-wideband beamforming with a series feed in its simplest form is shown that is comprised of a plurality of time delay circuits 18 having a means for switching in time delays from 0 to 2d/c, where d is the inter-element spacing and c is the velocity of light. At the highest frequency the elements are spaced by .lambda./2 to avoid grating lobes and the delay corresponds to 360.degree. of phaseshift, as with a normal phaseshifter.
In the series feed, an electromagnetic signal is coupled at uniform intervals along branch lines 24, 26, and 28 to antenna feed line 33 to radiating elements, 12 that are equally spaced along the aperture. For frequency independent steering of the beam, the electrical pathlengths from the electromagnetic signal source 14 to each radiating element 12 to the desired equiphasefront 16 must be the same. This is accomplished by the insertion of an adjustable time-delay circuit 18 into the antenna feed line 33 prior to each element 12.
An electromagnetic signal generated by an electromagnetic signal source 14, such as a radar or microwave transmitter, passes through a signal splitter 22 which divides the electromagnetic signal into a plurality of electromagnetic signals which are applied to the antenna elements 12 through a plurality of signal branches 24, 26, and 28. For an antenna array having an odd number of branches, at minimum there are three branches, a center or central branch 24, a right branch, and a left branch, 26 and 28, respectively. The center, or central, branch 24 is without variable time-delay 18, having only a bias delay 32 of a preselected amount. Its feed length is the same as that of the other branches 26 and 28 with delay adjusted to d/c. Dependent upon the operational frequency and power of the system, these branches 24, 26, and 28 and element feedlines 33 may be either waveguides, coaxial cable, or microstrip.