Wideband Microstrip Leaky-Wave Antennas With Two Symmetrical Side Beams for Simultaneous Dual-Beam Scanning

Abstract

Wideband microstrip leaky-wave antennas (LWAs) that radiate two symmetrical side beams are described. The two beams are steered simultaneously by sweeping the operating frequency. To achieve this, the second higher order mode of the microstrip is excited. Two electric field nulls are created between the microstrip and the ground plane using via arrays to suppress lower order modes. To test the concept, one of the antenna designs was prototyped. The prototyped antenna is capable of steering two symmetrical beams within a range of 37° when frequency is swept between 6.92 and 8.75 GHz. The measured peak gain of the antenna is 12.7 dBi and the variation of gain from 6.92 to 8.75 GHz is 3.1 dB. The measured 10-dB return loss bandwidth is 23%, which is very large for a dual-beam microstrip LWA. Such a wide impedance bandwidth is essential to achieve beam scanning over a wide angular range by sweeping frequency. Another advantage is that this single-layer antenna is easy to fabricate.