Linear Technology LTC5588-1 I/Q modulator

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Linear Technology has introduced the LTC5588-1, the latest generation of an ultra-high linearity direct conversion I/Q modulator that operates over a wide frequency range from 200 MHz to 6 GHz. The device offers linearity performance of 30.9 dBm OIP3 (output third-order intercept) at 2.14 GHz - without calibration.

The device can carry out simple calibration by a single-pin adjustment with a DC input voltage that further optimises its OIP3 up to 35.1 dBm. The modulator’s linearity performance is complemented with a noise floor of -160.6 dBm/Hz at 6 MHz offset, enabling transmitters to achieve good dynamic range performance.

The device offers image suppression of -56.6 dBc at 2.14 GHz. In addition, its carrier leakage is -39.6 dBm while delivering 5 dBm signal power to its output without calibration. Over the operating temperature range from -40 to 85°C, both parameters exhibit stable behaviour, varying only about ±3 dB.

Its performance satisfies the system requirements of the most demanding broadband wireless 4G basestations, including LTE, WiMAX, multi-carrier GSM/EDGE, W-CDMA, TD-SCDMA, CDMA-2000 and CDMA, as well as other wireless applications.

The I and Q inputs are biased to a 0.5 V DC common-mode voltage that is directly compatible with commercially available D/A converters that have similar DC common-mode voltage. The I and Q inputs support signal bandwidth greater than 400 MHz.

The device is powered from a single 3.3 V supply with an operating current of 300 mA. It has an enable pin, allowing the chip to power down. In shutdown mode, it draws a sleep current of less than 900 µA.

The modulator has fast turn-on and turn-off time, at 15 and 5 ns, supporting time division duplexing mode of operation.