3-D-Printed Tunable Circularly Polarized Microstrip Patch Antenna

We present a tunable circularly polarized (CP) microstrip patch antenna developed using three-dimensional (3-D) printing. Circular polarization is achieved by a novel method of introducing an L-shaped slot in a square patch antenna. Moreover, by loading the four edges of the patch with shunt varactors, the frequency of the antenna can be tuned while maintaining CP radiation. The use of 3-D printing for manufacturing enables the vertical integration of varactors between the patch and the ground, which has not been shown before. Such integration minimizes the interaction of varactors with the radiating properties of the antenna and results in reduced parasitics. Measured results show that the antenna has a frequency tuning range of 27.2% for CP operation with the center of tuning range around 1.9 GHz. The 3 dB axial-ratio bandwidth remains above 3% for each fixed frequency band of operation.