Composite right/left-handed substrate integrated waveguide leaky-wave antennas

Leaky-wave antennas based on composite right/left-handed (CRLH) substrate integrated waveguide (SIW) are investigated and presented in this paper. By introducing series interdigital capacitors, which are realized by etching slots on the waveguide surface, a balanced CRLH waveguide leaky-wave antenna with a continuous beam-steering capability has been implemented. The backfire radiation is obtained when the waveguide is operated below its characteristic cutoff frequency while the broadside radiation is achieved at the balancing frequency point. By embedding the series interdigital capacitors in both the top surface and the ground of the SIW, a frequency-scanned leaky-wave antenna characterized by double-side radiation or a quasi-omnidirectional feature is achieved. The measured results show that the proposed antennas offer a scanning angle covering almost backfire-to-endfire directions with relatively high gains.