A 24 GHz circularly polarized on-chip antenna for short-range communication application

This article presents a design method of miniaturized, circularly polarized (CP), concentric ring-shaped monopole on-chip antenna for 24 GHz short-range application. The proposed antenna covers automotive radar spectrum 22-29 GHz with a resonance at 24 GHz. Taking a simple circular ring-shaped patch as reference antenna, a small gap is introduced in the closed-loop structure that helps to provide the required travelling wave current distribution for realizing the CP property. Then a smaller circular ring is incorporated inside the reference antenna to improve the antenna performance in terms of CP characteristics. Finally, the proposed antenna is tuned to obtain the CP characteristics in the desired band ranging from 23.2 GHz to 27 GHz with 3-dB axial ratio (AR) bandwidth of 3.8 GHz. It offers a maximum gain of -4.5 dBi and wide angular range coverage (HPBW>75° in both E and H-plane). The standard CMOS process with only one level of mask (metal patterning) is used to realize the designed antenna. Compact in size of 3.8 mm × 4 mm × 0.678 mm, simple design layout, and its performance make the antenna as a suitable candidate for system-on-chip (SoC) application.