600MHz to 1100MHz High Linearity Direct Quadrature Modulator

The LT5558 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 GSM, EDGE, CDMA, CDMA2000, and other systems. It may also be confi gured as an image reject upconverting 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 doublebalanced 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 balanced I and Q baseband input ports are intended for DC coupling from a source with a common-mode voltage level of about 2.1V. The LO path consists of an LO buffer with single-ended input, and precision quadrature generators which produce the LO drive for the mixers. The supply voltage range is 4.5V to 5.25V.

Applications

* RFID Single-Sideband Transmitters

* Infrastructure TX for Cellular and ISM Bands

* Image Reject Up-Converters for Cellular Bands

* Low-Noise Variable Phase-Shifter for 600MHz to 1100MHz Local Oscillator Signals

* Microwave Links

* Direct Conversion from Baseband to RF

* High OIP3: + 22.4dBm at 900MHz

* Low Output Noise Floor at 20MHz Offset:

* No RF: –158dBm/Hz

* POUT = 4dBm: –152.7dBm/Hz

* Low Carrier Leakage: –43.7dBm at 900MHz

* High Image Rejection: –49dBc at 900MHz

* 3 Channel CDMA2000 ACPR: –70.4dBc at 900MHz

* Integrated LO Buffer and LO Quadrature Phase Generator

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

* High Impedance Interface to Baseband Inputs with 2.1V Common Mode Voltage

* 16-Lead QFN 4mm × 4mm Package