Abstract
It briefly introduced 1.5GHz to 2.5GHz High Linearity Direct Quadrature Modulator function, internal structure, pin array and typical apply circuit. The LT5572 is a direct I/Q modulator designed for high performance wireless applications, including wireless infrastructure. It allows direct modulation of an RF signal using differential baseband I and Q signals. It supports PHS,GSM, EDGE, TD-SCDMA, CDMA, CDMA2000, W-CDMA and other systems. It may also be confi gured as an image reject up-converting mixer by applying 90° phase-shifted signals to the I and Q inputs. The high impedance I/Q baseband inputs consist of voltage-to-current convertersthat in turn drive double-balanced mixers. The outputs ofthese mixers are summed and applied to an on-chip RF transformer which converts the differential mixer signals to a 50Ω single-ended output. The four balanced I and Q baseband input ports are intended for DC coupling from a source with a common mode voltage level of about 0.5V. The LO path consists of an LO buffer with single-ended input and precision quadrature generators that produce the LO drive for the mixers. The supply voltage range is 4.5V to 5.25V.
