Dual-Band Coradiator Antenna Employing Cascaded Triangular Cavities With a Steerable Beam in the Millimeter-Wave Band

A dual-band coradiator antenna with a beam-scanning capability for the sub-6 GHz and millimeter-wave (mm-wave) bands is proposed in this article. First, four subarrays based on cascaded triangular cavities are arranged using a mirror operation to form the mm-wave antenna array. Then, four mm-wave subarrays are connected at the position where the electric field is at a minimum on their edges. Finally, the entire mm-wave array structure resonates in the microwave band, which can be equivalent to a shorted quarter-wavelength patch antenna in the sub-6 GHz band. Hence, the same radiator can work as both a sub-6 GHz antenna and an mm-wave antenna array with broadside patterns in both cases. Attributed to the novel co-radiator structure, the proposed design is simple and compact. An interdigital coupled line with a high-pass filtering characteristic is inserted into each mm-wave feeding line to enhance the isolation. Besides, two parasitic patches are loaded to increase the microwave bandwidth. The experimental results show that the peak gain at 2.56 GHz is 3.2 dBi and at 28 GHz is 14.3 dBi for the sub-6 GHz and mm-wave bands, respectively. The isolation among different feeding ports is greater than 15 dB and the mm-wave array also provides ±38° beam-scanning performance.