Millimeter-Wave Beam-Steering Focal Plane Arrays With Microfluidically Switched Feed Networks

Microfluidically switched feed networks are introduced to realize millimeter-wave beam-steering focal plane arrays (FPAs). Switching functionality is achieved by a selectively metallized plate (SMP) repositionable within a microfluidic channel that is brought in close proximity to the microstrip line feed network of an FPA. The feed network is strategically designed to exhibit gap discontinuities that are sequentially overlapped by the SMP metallizations. The capacitive couplings between the SMP metallizations and the gap discontinuities are designed to achieve wideband (~20 GHz) switching functionality with low insertion loss (IL . 0.2 dB). Transmission line theory is utilized to demonstrate that the feed network offers 38% fractional bandwidth with ≤7 dB IL for linear arrays of 32 elements. This performance constitutes a significant improvement over the recently reported resonant feed network based realization of microfluidic beam-steering FPAs (MFPAs). Experimental verification is carried out through the design and fabrication of a 30 GHz eight-element FPA. The FPA exhibits measured gains ranging between 20.2 and 22.6 dBi. Loss budget breakdown confirms the low-loss performance of the microfluidically switched feed networks (≤3 dB). The required microfluidic actuation range is 4.2 mm and 10× lower than that of the prior work. This allows to achieve a faster beam-steering speed (0.27 s versus 5.25 s of previous designs). An integrated sensing approach for detecting the SMP position is also presented for the first time to facilitate the use of presented MFPAs with closed-loop position control.