2-18 GHz circular array interferometer DF antenna system
Murphy, S.; Eyring, P.M.
Antennas and Propagation Society International Symposium, 1998. IEEE
Volume 4, Issue , 21-26 Jun 1998 Page(s):2332 - 2335 vol.4
Digital Object Identifier 10.1109/APS.1998.701789
Summary:The DF antenna system contains two 3:1 bandwidth circular array
interferometers (CAI). Each CAI consists of an 8-element circular-array
aperture coaxially connected to an 8-input, 4-output Butler matrix
mode-forming network as shown. The Butler matrix outputs represent the
omnidirectional phase modes of the CAI. High-accuracy (1.2 deg. RMS),
monopulse angle-of-arrival (AOA) measurement over a full 360-degree
instantaneous field of view is obtained using only three receiver
channels. The CAIs provide true azimuth AOA independent of the elevation
angle; unlike linear interferometers, which exhibit coning about their
baseline. Of the remaining Butler matrix outputs, one is utilized as a
wide-open signal acquisition channel and the other four are terminated.
Using a common aperture with a 360 degree instantaneous field of view
enables acquisition and AOA determination to be performed simultaneously
on every pulse. The common aperture also eliminates differential
multipath between the acquisition and DF channels. In addition, it also
minimizes the antenna size and overall system cost
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