A Large Microstrip Patch Array With a Simplified Feed Network: A low cross-polarized design

Discontinuities in the feed lines are one of the major sources of spurious radiation that results in high crosspolarized (XP) radiation in microstrip-line-fed large arrays. This limits the use of the arrays in satellites where frequency is reused by means of polarization diversity. But for low-profile and lightweight designs, microstrip arrays are very useful. In this article, the design aspects of a simpler topology for the array feed network are discussed in detail. The purpose is to realize an array with high XP isolation by reducing the number of discontinuities. In addition, this topology reduces the length of the feed network of 2 × 2 subarrays by approximately 20%, as well as reducing the amount of the mutual coupling. A rectangular array with 32 × 16 elements has been realized at 10.7 GHz using this concept, for transmission of satellite telemetry data. The measured results of the array indicate more than 35 dB of XP isolation, even in the diagonal planes. The aperture efficiency of the array is found to be approximately 27%, which is very good for a microstrip-fed array.