Reconfigurable Transmitarray With Near-Field Coupling to Gap Waveguide Array Antenna for Efficient 2-D Beam Steering

Abstract

A novel array antenna architecture is proposed that can enable 2-D (full-space) radiation pattern control and efficient beam steering. This solution is based on a gap waveguide array antenna and a reconfigurable transmitarray (TA) that are coupled in the radiative near field. An equivalent two-port network model of the coupling mechanism is presented and validated numerically. The desired TA reconfiguration capability is realized by an $8 \times 8$ array of cavity-backed patch resonator elements, where two AlGaAs p-i-n diodes are integrated inside each element providing a 1-bit phase shift. The TA is implemented in an eight-layer printed circuit board (PCB), which includes radiating elements, fixed phase-shifting inner-stripline sections, impedance matching, and biasing circuitry. The combined antenna design is low profile (~1.7 wavelength) owing to the small separation between two arrays (~0.5 wavelength), as opposed to conventional TAs illuminated by a focal source. The design procedure of the proposed architecture is outlined, and the measured and simulated results are shown to be in good agreement. These results demonstrate 23.5–25.2 GHz −10-dB impedance bandwidth and 23.3–25.3 GHz 3-dB gain bandwidth, a beam-steering range of ±30° and ± 40° in the E- and the H-planes with the gain peak of 17.5 dBi, scan loss $\le3.5$ dB, and TA unit cell insertion loss $\le1.8$ dB, respectively.