Optimized subarray amplitude tapers for array antennas

• US 5,434,576 A
• Filed: 02/23/1994
• Issued: 07/18/1995
• Est. Priority Date: 02/23/1994
• Status: Expired due to Fees

• Current Assignee: United States Air Force
• Original Assignee: United States Of America As Represented By The Secretary Of The Air Force
• Inventors: Haupt, Randy L.
• Primary Examiner(s): Issing, Gregory C.
• Application Number:
  US08/200,618
• Time in Patent Office: 510 Days
• Field of Search: 342/378, 342/379, 342/380, 342/383
• US Class Current: 342/378
• CPC Class Codes: G01S 3/06 Means for increasing effective directivity, e.g. by combining signals having differently oriented directivity characteristics or by sharpening the envelope waveform of the signal derived from a rotating or oscillating beam antenna comparing amplitude of signals having differently oriented directivity characteristics to determine direction G01S3/16, G01S3/28
• CPC Class Codes: G01S 7/2813 Means providing a modification of the radiation pattern for cancelling noise, clutter or interfering signals, e.g. side lobe suppression, side lobe blanking, null-steering arrays specially adapted to secondary radar systems G01S13/762; aerials or aerials systems H01Q21/29, H01Q25/00
• CPC Class Codes: H01Q 21/22 Antenna units of the array energised non-uniformly in amplitude or phase, e.g. tapered array or binomial array

Abstract

A method for economically producing low sidelobe levels in the far field pattern of an array antenna is disclosed. The current fed to the subarrays is identically tapered to the elements of each subarray. Both the subarray current taper and the element current tapers are optimized to yield the lowest possible sidelobe levels.

Claims

1. In an antenna array having a plurality M of subarrays, and a plurality N of antenna elements, each antenna element being provided with a predetermined identical amplitude taper, each of said subarrays comprising a summer and subarray port for summing the combined amplitude tapered outputs of said elements, to produce a subarray output signal, which is, in turn, weighted by a subarray weight, the method of amplitude tapering comprising the steps of:

a. selecting the number N of elements in the array and the number M of subarrays;

b. next, using numerical optimization, selecting the subarray amplitude weights and the element amplitude weights that yield the lowest sidelobes in accordance with the equation;

##EQU4## where;

M=number of subarrays

N=number of elements per subarray

b_m =amplitude weight at subarray m

a_n =amplitude weight at element n

k=2 Pi/wavelength

ds=spacing between subarrays

de=spacing between elements within a subarray

u=cos φ

φ

=observation direction

c. if the selection of the subarray and element amplitude weights does not yield sufficiently low sidelobe levels, then increase the number of subarrays by decreasing the number of elements per subarray; and

d. repeating steps a, b and c until sufficiently low sidelobe levels are obtained.