1.5GHz to 2.5GHz High Linearity Direct Quadrature Modulator

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 configured 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 converters that in turn drive double-balanced mixers. The outputs of these 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.

Applications

* Infrastructure Tx for DCS, PCS and UMTS Bands

* Image Reject Up-Converters for DCS, PCS and UMTS Bands

* Low Noise Variable Phase Shifter for 1.5GHz to 2.5GHz Local Oscillator Signals

* Direct Conversion from Baseband to RF

* High Output: –2.5dB Conversion Gain

* High OIP3: +21.6dBm at 2GHz

* Low Output Noise Floor at 20MHz Offset:

* No RF: –158.6dBm/Hz

* POUT = 4dBm: –152.5dBm/Hz

* Low Carrier Leakage: –39.4dBm at 2GHz

* High Image Rejection: –41.2dBc at 2GHz

* 4-Channel W-CDMA ACPR: –67.7dBc at 2.14GHz

* Integrated LO Buffer and LO Quadrature Phase Generator

* 50Ω AC-Coupled Single-Ended LO and RF Ports

* High Impedance DC Interface to Baseband Inputs with 0.5V Common Mode Voltage

* 16-Lead QFN 4mm × 4mm Package