Design of beam forming networks with reduced frequency dependence in output phase distribution

Beam forming networks (BFNs) are essential for array antennas or array-fed reflector antennas in order to excite antenna elements with the desired exc itation coefficients. The excitation coefficients are usually designed as c onstant values over the frequency band, and therefore BFN frequency depende nce causes coefficient variation with frequency shift and degrades antenna performance. In this paper, a method of design of TEM-line BFNs with reduce d linear frequency dependence in output phase distribution is proposed, and is verified by a design example. The major characteristic of the method is that a unique design result is obtained for given excitation coefficients and a given BFN topology by iteration of a simple procedure. (C) 1999 Scrip ta Technica.