An ESD-protection-free monolithic harmonic filter for WLAN applications

Modern multi-band and multi-mode handheld wireless devices require novel approaches for the integration of passive elements into the radio front-end. In this paper, we present the design of an electrostatic discharge (ESD)-protection-free harmonic filter using an improved high-resistivity silicon copper technology for the monolithic integration of active and passive devices. Typical metal-isolator-metal (MIM) capacitors are replaced by inter-digital metal capacitors which provide a high breakdown voltage of up to 800 V. As the machine-mode ESD voltage is lower than 500 V, this filter can operate without ESD protection. In this design, electromagnetic (EM) simulation was used extensively for inductor and filter optimization. The fabricated device has an insertion loss of less than 0.3 dB and 2^nd and 3^rd harmonic attenuations of more than 30 dB for the WLAN 2.4 GHz frequency band and features a size of 0.75×0.67 mm².