A TM30-/TM40-Mode Pattern-Reconfigurable Microstrip Patch Antenna for Wide Beam Coverage

Abstract

A novel two-state multi-lobe pattern-reconfigurable microstrip patch antenna (MPA) for wide beam coverage is proposed, where two states are realized by two higher modes, and a multi-lobe pattern is employed for each state. First, the equivalent transmission line model is used to analyze the input impedances of the dual-mode MPA. By adjusting sizes of the capacitive coupling patches and profile of the MPA, the frequency bands of TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">30</sub> and TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">40</sub> modes are controlled, yielding a band intersection. Second, by controlling the length of the radiating patch, the beam-level differences of TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">30</sub> -mode and TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">40</sub> -mode patterns are reduced, respectively. Third, two parasitic patches are also loaded. As a result, the mode-gain difference between TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">30</sub> and TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">40</sub> modes is small, and all the beam overlap levels are higher than -3 dB. The measured results show that the 3 dB beam coverage of the MPA at 2.9 GHz ranges from -68° to +73° in the xoz plane, and its maximum gain is 7.0 dBi. Furthermore, the two-state pattern-reconfigurable MPA has a 3-lobe pattern pointing at {0°, ±37°} for the first state and a four-lobe pattern pointing at {±17°, ±58°} for the second state. The measured results are in good agreement with the simulated ones.