Design of a Novel Wideband Reconfigurable Transmit-Reflect-Array Antenna Utilizing Twin Lines

This communication proposes a novel topology that enables the integration of a reflect-array (RA) and a transmit-array (TA). Based on this topology, a reconfigurable transmit-RA (RTRA) antenna is physically implemented, capable of switching between a 1-bit reconfigurable RA mode and a fixed beam TA mode. The key to achieving this functionality is the proposed three-state reconfigurable circuit, which utilizes two shunt p-i-n diodes to generate two reflection states with a 180° phase difference and one transmission state. The twin line is selected to build the reconfigurable circuit due to the discovery that the characteristic impedance of the transmission line is critical to the on/off performance of the shunt p-i-n diodes. As a natural consequence, half-wavelength-dipole antennas, which can be simply fed by the twin line, are used as the receiving and radiating elements. After loading the dipole antennas to the reconfigurable circuit, the length of the in-between transmission line is adjusted to stabilize the original frequency-dependent phase difference between the two reflection states at around 180° with a small variation over a wide band. A
$16\times16$
-element array was constructed and measured, demonstrating over 36% bandwidth in the broadside RA and TA modes with maximum aperture efficiencies of 27% and 29% respectively. In terms of the beam steering characteristic in the RA mode, the antenna can cover ±45° in both the E- and H-planes. It is also noteworthy that the entire RTRA surface, including the dc biasing network, is fabricated using single-layer PCBs, thus making the proposed design easy and cost-effective to fabricate.