In order to minimize the effect of packaging on the microwave performance and the sensitivity at X-band, a packaging theory of an inline coupling RF MEMS power sensor is proposed in this paper. The inline RF MEMS power sensor implemented based on GaAs MMIC technology is flip-attached to a large CPW transmission line fabricated on the ceramic substrate with a low dielectric loss. The design method realizes the electrical contact between CPW line ports of the power sensor and the large CPW line on the ceramic substrate served as the supporting role, and maintains the impedance matching of the contact areas. And the ceramic substrate underneath the chip of the power sensor is removed for resulting in thermally isolating and obtaining the excellent sensitivity. Finally, input and output ports of the CPW line on the ceramic substrate are directly connected with standard SMA connectors. The simulated results show reflection losses of less than −22 dB and insertion losses of less than 1 dB at X-band after the packaging, and verify the accuracy of the packaging theory.
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