Simple E-Plane Decoupling Structure Using Embedded Mushroom Element for Wide-Angle Scanning Linear Microstrip Phased Arrays

In this letter, a simple and novel E-plane decoupling structure is presented for wide-angle scanning microstrip phased array antennas. Consisting of a mushroom-like element and a capacitive circular air gap, the proposed structure essentially behaves as an inductor-capacitor (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i>) series resonator. By embedding such an element into two closely spaced square microstrip antennas with mirrored and translated arrangements, respectively, the mutual coupling can be effectively suppressed without compromising compactness or requiring additional space. Then, a 1 × 8 microstrip array antenna with a close center spacing of 0.4<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is elaborately designed by exploring the proposed decoupling structure. All port isolations are better than 16 dB within the -10 dB operating bandwidth of 2.9 GHz to 3.1 GHz. For validation, the proposed prototypes have been fabricated and experimentally tested; the measured results show that the proposed antenna array can scan from −74° to 70° with a realized gain loss of less than 3.3 dBi. With the merits of simple structure, compact size, and good decoupling performance, the proposed method has great potential for wide-angle beam-scanning phased array antennas.