Patent ID: 8791875

Claim:
Apparatus for mitigation of pattern blockage due to the scattering of RF energy from an antenna that impinges on a blocking surface, comprising: an artificial surface located between the antenna and the blocking surface on a ground plane, said artificial surface including a slow wave structure for altering the spherical wave front of the RF energy from the RF antenna that is collected and reradiated by said artificial surface, said artificial surface providing at least one of a flattened wave front for the energy collected and reradiated by said artificial surface that impinges on said blocking surface, said slow wave structure including a variable impedance transmission line array, said variable impedance transmission line array having an operating frequency which is tunable, said variable impedance transmission line array including a number of meanderlines each having a low impedance section and an adjacent high impedance section, wherein said slow wave structure includes a ground plane array and further including a layer for altering the distance between said low impedance section and said ground plane array, thereby to alter the operating frequency of said meanderlines and thus the operating frequency of said variable impedance transmission line, said layer including a piezoelectric layer, including a pair of electrodes, and further including a control voltage and means for applying the control voltage to said electrodes, said control voltage being set based on an predetermined operating frequency, corresponding to the transmit frequency for the RF energy radiated by said antenna, and further including a control loop for sensing said transmit frequency and for providing signals used to adjust the operating frequency of the variable impedance transmission line array.