Circularly Polarized Ellipse-Loaded Circular Slot Array for Millimeter-Wave WPAN Applications

A circularly polarized slot array suitable for millimeter wave WPAN applications is presented. The array uses a new type of circularly polarized element, comprising a circular slot loaded with an elliptical patch, and is fed by a microstrip line. The array is implemented on liquid crystal polymer (LCP), which is both low-loss and low-cost. A total of 8 array elements are used in a 4 times 2 configuration to achieve a maximum gain target of greater than 14 dBic. Sequential rotation of the elements within each of the 2 times 2 sub-arrays is used to increase the axial ratio bandwidth. Other novel features of the array are the finite ground plane, and open cavity structure used to support the LCP substrate of the slot array above a reflector plate. Measured and computed results presented for the packaged array confirm its wide impedance, axial ratio, and gain bandwidths. The effect of the packaged array back-short on the measured axial ratio is also discussed.