System-in-Antenna (SiA): A Compact Architecture for Integrated RF and Thermal Management

This paper introduces a new System-in-Antenna (SiA) architecture aimed at mitigating thermal issues in compact RF frontend integration. Departing from traditional layouts, where RF circuits are positioned between antenna and baseband layers. The proposed SiA architecture incorporates RF circuits directly within the cavity of the antenna's radiating structure. This integrated layout enables the antenna to simultaneously function as an electromagnetic radiator and a thermal dissipation structure, thereby enhancing heat removal efficiency without relying on external cooling mechanisms. To validate this concept, a prototype employing a half-wavelength shorted patch antenna was designed and fabricated. Experimental results confirm that the SiA system operates effectively over the 3.3 to 3.6 GHz band, delivering an antenna gain of 29.3 dBi, a receiver path gain of 24.1 dB, a noise figure of 3.4 dB, and output power surpassing 36 dBm. Thermal measurements indicate a temperature reduction of 29.1 °C (from 96.5 °C to 67.4 °C), when compared to conventional integration architecture. By utilizing the antenna surface as a shared electromagnetic and thermal interface, the SiA design provides a promising direction for thermally efficient, densely integrated RF frontends in next-generation wireless systems such as 5G/6G base stations and phased array radars.