Single-/Dual-Beam Switchable Beamforming Network Based on Phase-Shifter-Relaxed 4 × 4 Nolen Matrix

A novel beamforming network providing switchable states between single and dual beams is proposed. A new topology of the phase-shifter (PS)-relaxed Nolen matrix based on two-section couplers with arbitrary coupling coefficients and arbitrary phase differences is used as the feeding network. Theoretical analysis is conducted on the PS-relaxed Nolen matrix topology and flexible two-section couplers using vector synthesis methods. Based on the proposed topology and couplers, the feeding network can be easily switched between the phase states for single-/dual-beam radiation patterns by using only one reconfigurable PS. For demonstration, a single-/dual-beam switchable beamforming network based on the PS-relaxed
$4\times4$
Nolen matrix is designed, fabricated, and measured at 2.4 GHz. The phase differences between the output ports of the feeding network can be (0°, 0°, 0°), (90°, 90°, 90°), and (−90°, −90°, − 90°) with a biasing voltage of 5.2 V for single-beam beamforming, and (180°, 180°, 180°), (180°, 0°, 180°), and (0°, 180°, 0°) with a biasing voltage of 15.9 V for dual-beam beamforming. The measured additional insertion loss is 0.24–1.09 dB over all states. Using the proposed feeding network, the antenna array can radiate, respectively, at 0°, −26°, and 26°, or two-lobe beams at ±18°, ±33°, and ±51°.