Joint TX and feedback RX IQ mismatch compensation for integrated direct conversion transmitters

Abstract

The direct conversion (DC) architecture has been adopted for wireless base-station transceivers due to its cost and area efficiency. The shortcomings of DC transceivers need to be overcome to meet their high performance requirements. In-phase (I) and quadrature phase (Q) mismatch is one of most significant impairments. This paper presents an integrated, on-line mismatch compensation system which calibrates frequency-dependent transmitter (TX) and feedback receiver (FBRX) IQ mismatches using the digital TX signal as a reference. The proposed method was fabricated in 45nm CMOS technology. Measurements show 60 dBc TX ACPR for 20MHz LTE low-IF signals. TX EVM of 0.8% is achieved with 20MHz zero-IF LTE signals.