700MHz to 6GHz Low Power Direct Quadrature Modulator

The LTC5589 is a direct conversion I/Q modulator designed for low power wireless applications that enables 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 adjustments of I and Q gain and phase imbalance to optimize the LO carrier feedthrough and side-band suppression. The LO port can be driven with sine wave or square wave LO drive. A fixed LC network on the LO and RF ports covers 700MHz to 6GHz operating range. 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

* Vector Modulator

* 2.45GHz and 5.8GHz Transmitters

* Software Defined Radios (SDR)

* Military Radios

* Frequency Range: 700MHz to 6GHz

* Low Power: 2.7V to 3.6V Supply; 29.5mA

* Low LO Carrier Leakage: –43dBm at 1.8GHz

* Side-Band Suppression: –50dBc at 1.8GHz

* Output IP3: 19dBm at 1.8GHz

* Low RF Output Noise Floor: –157dBm/Hz at 30MHz Offset, PRF = 1.8dBm, fRF = 2.17GHz

* Sine Wave or Square Wave LO Drive

* SPI Control:

* Adjustable Gain: 19dB in 1dB Steps

* Effecting Supply Current from 9mA to 39mA

* I/Q Offset Adjust: –64dBm LO Carrier Leakage

* I/Q Gain/Phase Adjust: –61dBc Side-Band Suppressed

* 24-Lead 4mm × 4mm Plastic QFN Package