A technique to estimate the relative gains, tuning phases, and RE phase shifts of the elements of a phased-array radar

Abstract

An in-situ technique to estimate the following parameters of a phased-array antenna is described: 1) the relative array-element excitation voltages, 2) the array-element tuning phases, and 3) the RF phase shifts at the array elements. This technique has several significant features. First, it involves the use of two auxiliary antennas. One is a remote continuous wave (CW) source directed at the phased-array antenna. The other is a passive antenna mounted close to the phased-array antenna. Its output is used to produce a reference phase for phase measurements. Second, it contains a technique to reduce the errors in phase estimates. Third, it takes note that beam steering uses phase sums of the form ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\phi_{k} + \beta_{kl}</tex> ), where <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\phi_{k}</tex> is the tuning phase for the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</tex> th array elemenet and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\beta_{kl}</tex> , is an RF phase shift of the array element, and pays special attention to reduce the errors associated with the estimates of these sums. Fourth, it assumes the use of a reasonably stable and strong CW source of commerically available quality. No other assumptions are made. Experimental results obtained with a 295-element <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</tex> -band space-fed phased-array antenna are given.