Achieving Fixed-Frequency Beam Scanning With a Microstrip Leaky-Wave Antenna Using Double-Gap Capacitor Technique

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Abstract
This study presents a novel half-width microstrip leaky wave antenna (HW-MLWA) that can electronically control its beam at a fixed frequency by using a double-gaps capacitor with diodes, resulting in good impedance matching with small variation gain while scanning. The elementary building blocks of this antenna are periodic HW-MLWA and seven control unit cells (CUCs). A reconfigurable CUC is created by combining two triangle patches as double-gaps capacitor with two diodes as switches to connect the patches with the ground plane. A gap capacitor in each patch cell is independently disconnected or connected by using a PIN diode switch. The reactance profile at the free edge of the microstrip is modified when the state of the patch cell changes, which in turn, shifts the main beam direction. A single-pole double-throw switch is used to achieve backward-to-forward beam scanning at a certain frequency. An HW-MLWA is designed, fabricated, and validated. The proposed antenna prototype can scan the main beam forward between +28° and +67° and backward between -27° and -66° at 4.2 GHz. The measured peak gain of the antenna is 11.12 dBi at 4.2 GHz, the gain variation is 1.3 dB while scanning.

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