Design of a Single-Radiator Multi-Port Compact Chip Antenna for UWB Direction-Finding

This paper proposes a single-radiator multi-port (SRMP) compact chip antenna for ultra-wideband (UWB) direction-finding. The antenna proposed in this paper is miniaturized to a physical size of 11.5 mm $\times 9.46$ mm $\times 1.6$ mm by utilizing a ceramic substrate with high-permittivity of 20. Furthermore, we designed a CPW feed line for the proposed chip antenna and verified its performance when mounted on a board through simulation and measurement. This small structure includes a multi-port system that can replace a conventional array system, utilizing the tripod-shaped single radiator. To verify the feasibility, the proposed antenna is fabricated and the antenna characteristics such as reflection coefficients, mutual couplings, and radiation patterns are measured in a full anechoic chamber. The proposed antenna has an operating bandwidth of 7 GHz to 9 GHz, which makes it well-suited for UWB Channel 9 (7.737 GHz–8.236 GHz) in Korean mobile devices. The measured mutual coupling result is below −10 dB across the operating frequency band. In addition, the radiation patterns in the zx-plane and zy-plane are anlayzed, and a bore-sight gain of 4.2 dBi is observed at 8 GHz. To verify the direction-finding performance, the proposed antenna is connected to the Nordic board nRF52840 DK with the commercial Qorvo DW3000 module to obtain channel impulse response (CIR) data. Then, the direction of arrival (DoA) is measured at distances of 0.3 m, 1 m, and 2 m according to the incident angle from −30° to 30°. The root mean square (RMS) errors at distances are 1.1°, 1.2°, and 1.5°, respectively. These results demonstrate that the proposed compact chip antenna is suitable for use in mobile devices equipped with UWB direction-finding technology.