Printed slot antennas are very attractive at millimeter wave frequencies due to their low profile, low cost, light-weight and the fact that they can be easily integrated with electronics. However, a single slot antenna printed on a dielectric substrate at millimeter-wave frequencies suffers from surface-wave losses. The surface-wave losses can be reduced by using half guided wavelength spaced broadside linear twin-slot elements based on the phase-cancellation approach [1-4]. However for linear slots, the phase cancellation is complete only at the broadside direction over the substrate. Here a new twin arc-slot antenna element is proposed to reduce the surface-wave fields effectively in all directions over the substrate. This work bears some similarity to the reduced surface-wave microstrip patch antennas proposed by Jackson, et al [5] However, a microstrip patch with no surface-waves is geometrically larger than a resonant one [5]. To achieve simultaneous complete surface-wave cancellation and resonance, etching an inhomogeneous region beneath the patch has been proposed [5]. This obviously increases the complexity of the structure. To this end, the proposed twin arc-slot element offers the ability of achieving almost complete surface-wave cancellation and resonance simultaneously by allowing its radius and the length of each arc-slot to be adjusted independently.
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