Tunable Huygens' Transmission Metasurface on Double-Layer PCB

A tunable transmission Huygens' metasurface implemented in compact double-layer PCB is presented. The unit cells consist of electric and magnetic dipoles where the phase responses are independently controlled by an off-the-shelf PIN diode and varactors, respectively. The DC bias lines are embedded in double metallic layers and highly resistive resistors and DC blocking capacitors are used to reduce cell-to-cell and RF-DC coupling. The metasurface unit cell structures are designed for proof of concept at 10 GHz. For efficient transmission with multiple phases, the optimum pairs of ON-OFF states of the PIN diode and capacitance of the varactors are investigated. The final unit cells with electronic tuning cover transmission phase states from -90°to +150° with average loss of -3 dB.