Crosspolarisation behaviour of series-fed microstrip linear arrays

Crosspolarisation effects in microstrip antenna arrays have received little attention to date, and the purpose of this paper is to identify sources of crosspolarisation and quantify design parameters for a wide variety of radiating structures suitable for use in series-fed arrays. Surface wave effects and radiation from connectors and feed transitions are included as additional factors. Chain, rampart, comb, serpent-line and patch array antennas are some of the types examined, and it is concluded that a magnetic source radiation model having two degrees of positional freedom allows generation of useful first-order design data for all structures. To obtain a more accurate assessment, second-order effects pertaining to the specific radiating structure must be included, and this is illustrated for the comb-line antenna. The constraints imposed by the two degrees of positional freedom and the necessity to trade the overall comb-line antenna performance in order to optimise the crosspolarisation characteristics are particular conclusions which are likely to hold for all types of micro-strip antenna.