Dual-Band Leaky-Wave Antenna Based on Dual-Mode Composite Microstrip Line for Microwave and Millimeter-Wave Applications

A dual-mode composite microstrip line (DMC-MSL) is reported in this paper for the purpose of designing dual-band antennas and devices with a large frequency ratio. The metallic strip of the conventional MSL is replaced with a substrate integrated waveguide (SIW) arranged into a thin dielectric laminate, which leads to that two modes operating in different frequency bands, i.e., the quasi-TEM mode and the TE10-like mode, can propagate along the transmission line structure simultaneously. The DMC-MSL with a dual-layered planar configuration combines the merits of the MSL and the SIW. In addition, by adjusting the permittivity of the dielectric laminate used for realizing the thin SIW, the frequency ratio of the two operating modes can be varied flexibly. Based on the DMC-MSL structure, a novel dual-band leaky-wave antenna is presented. Periodic parasitic microstrip patches and the transverse slot array etched on the SIW are introduced in order to generate the required spatial harmonics. A feed structure that can excite the two operating modes of the DMC-MSL separately is designed as well. The fabricated prototype verifies that backward and forward frequency-scanning radiation beams are achieved within the low-frequency band from 5.75 to 8.5 GHz and the high-frequency band from 35 to 41.5 GHz, respectively. The proposed DMS-MSL structure and the leaky-wave antenna offer a new mean to implement antennas and devices for microwave and millimeter-wave dual-band applications.