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In this paper, a high gain tetra-band microstrip patch antenna fed by a modified L-shaped strip has been designed, simulated and measured. The antenna consists of three concentric square-loop patches to support four operating modes and cover WLAN/Bluetooth, WiMAX, Mobile/Fixed satellite services, and WLAN/V2X commercial applications. In order to enhance gain of the antenna, the incorporating effect of the antenna with a superstrate and an artificial magnetic conductor (AMC)-perfect electric conductor (PEC) ground plane is investigated. It is demonstrated that the antenna gain is enhanced significantly when the superstrate is placed over the AMC-PEC ground plane based antenna. It shows a realized gain of 10.1 dBi at the first frequency band and achieves an increase in the gain by 7.5 dB. One outstanding result of the proposed design is that the air thickness between the square loops and the superstrate is about k/40, because of the AMC-PEC ground plane. The proposed antenna has a low profile with overall dimensions of 0.64k 9 0.64k 9 0.08k for the frequency at 2.42 GHz. A prototype of the antenna is fabricated and tested to verify the design.

In this study, an X‐band low‐profile monopulse array antenna with high aperture efficiency is proposed for tracking applications. It is consists of a 112‐element patch array antenna, a monopulse comparator, and a full corporate feed network which is composed of the waveguide and microstrip dividers. The monopulse comparator and waveguide part of the feed are produced out of a single‐layer substrate as the back‐end section. Also, the printed array antenna and microstrip part of the feed network are integrated as the front‐end. Finally, the back‐end and the front‐end are integrated through 32 SMP connectors. The proposed design decreases the lateral size of the feed and results in achieving a high level of aperture efficiency. A prototype of the proposed design was manufactured and validated the design experimentally. The measurement results demonstrate that the impedance bandwidth (∣Sii∣ ⩽−12thinmathspacedB) is up to 12% with the isolations better than 20 dB. The maximum gain of the sum beam is 28.7 dBi, while the null depths of the difference patterns are better than 24 dB. The excellent characteristics of the proposed design make it a good candidate for two‐dimensional monopulse tracking applications at X‐band up to millimetre wavelengths.