Summary
International Symposium on Antennas and Propagation
2010
Session Number:4FD4
Session:
Number:4FD4-4
Compact Single-Layer Planar Wideband 180°Balun Networks
H.K. Oh, W.Y. Lim, K.K. Chan,
pp.-
Publication Date:2010/11/23
Online ISSN:2188-5079
Summary:
Baluns are frequently used in microwave networks connecting balanced circuits to unbalanced ones such as mixers, amplifiers and antenna feed networks. In many instances, space for the circuit layout is not a concern since only one or two components are involved. In this paper, we evaluate a number of 180° baluns to investigate their suitability for use as compact element feeds for a broadband wide angle scan array. The balun should have a bandwidth of 80 - 90%, phase deviation of ±5°, amplitude imbalance of < 0.5 dB and input match < -13 dB. Typical broadband elements used in antenna arrays that required two anti-phase inputs are bow-tie and dual probe-fed patch radiators. Because of the wide scan requirement, element spacing is approximately 0.50 wavelength at the highest frequency of operation. This restricts the planar area available for the balun implementation to a half wavelength square. Further, to maintain a low profile implementation of the array, the feed network should be placed in a single layer backing and orthogonal to the array. Seven different networks have been evaluated. The most appropriate in the form of a parallel connection of double Schiffman coupled lines with matching lines is chosen for implementation. Plots of the measurements of this circuit are given below and they show that the network meets all of the requirements.