Linear Technology's LTC6946 is an integer-N frequency synthesiser with integrated VCO, that will deliver -226dBc/Hz normalised closed-loop in-band phase noise, -274dBc/Hz normalised in-band 1/f noise and -103dBc spurious output.

In a typical 900MHz application, this means the device can achieve a closed-loop phase noise of  -100dBc/Hz at 1kHz offset.

The device is available in three frequency options: the LTC6946-1 tunes from 2.240GHz to 3.740GHz; the LTC6946-2 from 3.080GHz to 4.910GHz; and the LTC6946-3 covers 3.840GHz to 5.790GHz.

Each synthesiser has an on-chip output divider that is programmable from 1 through 6 to extend frequency coverage to as low as 373MHz.

This family of devices integrates a low noise 5.7GHz phase-locked loop (PLL), which includes a reference divider, phase-frequency detector (PFD) with phase-locked indicator, ultralow noise charge pump, and integer feedback divider to attain very low noise PLL operation.

The PLL circuit is coupled to a low noise VCO as well as internal self-calibration to ensure optimum VCO resonator tuning for best phase noise performance.

The VCO requires no external components. The on-chip SPI compatible bidirectional serial port allows frequency tuning and control, and read back of register and loop status information. 

Target applications are likely to be in multiband basestations supporting LTE, W-CDMA, UMTS, CDMA, GSM and WiMAX standards.

The PLLWizard comprehensive PC-based design tool software is available to facilitate interactive control and interface with the LTC6946’s evaluation board. 

The PLLWizard design tool software is available for download free of charge from the Linear Technology website at www.linear.com/synthesizers