30MHz to 1300MHz Low Power Direct Quadrature Modulator

The LTC5599 is a direct conversion I/Q modulator designed for low power wireless applications that enable direct modulation of differential baseband I and Q signals on an RF carrier. Single side-band modulation or side-band suppressed upconversion can be achieved by applying 90° phase-shifted signals to the I and Q inputs. The I/Q baseband input ports can be either AC or DC coupled to a source with a common mode voltage level of about 1.4V. The SPI interface controls the supply current, modulator gain, and allows optimization of the LO carrier feedthrough and side-band suppression, with sine wave or square wave LO drive. A fixed LC network on the LO and RF ports covers a continuous 90MHz to 1300MHz operation. An on-chip thermometer can be activated to compensate for gain-temperature variations. More accurate temperature measurements can be made using an on-chip diode. In addition, a continuous analog gain control (VCTRL) pin can be used for fast power control.

Applications

* Wireless Microphones

* Battery Powered Radios

* Ad-Hoc Wireless Infrastructure Networks

* “White-Space” Transmitters

* Software Defined Radios (SDR)

* Military Radios

* Frequency Range: 30MHz to 1300MHz

* Low Power: 2.7V to 3.6V Supply; 28mA

* Low LO Carrier Leakage: –51.5dBm at 500MHz

* Side-Band Suppression: –52.6dBc at 500MHz

* Output IP3: 20.8dBm at 500MHz

* Low RF Output Noise Floor: –156dBm/Hz at 6MHz Offset, PRF = 3dBm

* Sine Wave or Square Wave LO Drive

* SPI Control:

* Adjustable Gain: –19dB to 0dB in 1dB Steps Effecting Supply Current from 8mA to 35mA

* I/Q Offset Adjust: –65dBm LO Carrier Leakage

* I/Q Gain/Phase Adjust: –60dBc Side-Band Suppressed

* 24-Lead QFN 4mm × 4mm Package