Dual-band transceivers are widely researched, especially for WLAN applications. A conventional dual-band system needs two sets of mixers for both frequency bands. For hardware integration and cost reduction, a single-stage mixer was reused with a subsequent dual-band filter or two single-band filters. However, extra loss is inevitable when using passive filters. In spite of previous solutions, a Gilbert mixer with a dual-band LC current mirror combines differential output currents with extra gain improvement at two designated frequency bands.