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This paper proposes a novel active interference cancellation system that allows simultaneous operation of multistandard collocated radios. It addresses specifically, the coexistence problem of closely spaced Bluetooth and 802.11b WLAN radio systems on a mobile wireless device. The suggested technique uses a small replica of the aggressing signal tapped off from the transmit antenna to generate a cancellation signal across the entire receive band. A prototype of the solution has been implemented on an FR-4 board, which consists of an emulation filter to model the coupling channel; and amplitude, delay and phase alignment of the cancellation signal. The required VGA and phase aligner have also been fabricated on chip with a 0.18 μm CMOS technology using active circuitry. Cancellation of up to -30 dB of in-band interference has been measured. The integrated components dissipate 15mW of power.