5MHz to 1.6GHz High Linearity Direct Quadrature Modulator Extends Dynamic Range Performance of Wireless Transmitters

The LTC5598 has outstanding dynamic range performance, from low frequency to above 1GHz, making it ideal for point-to-point broadband microwave links, 450MHz and 700MHz LTE basestation transmitters, 800MHz GSM / 900MHz EDGE basestation transmitters, 880MHz CDMA2000 basestations, video and cable broadband modulators, multiband military radios, 900MHz multiprotocol RFID readers and satellite transmitters. It is also uniquely capable of operating down to 5MHz, enabling many very low-frequency applications such as 13.56MHz RFID and contactless readers, telemetry, military communications and medical instrumentation.

The LTC5598 integrates two matched, high linearity double-balanced mixers and a broadband precision quadrature phase-shifter with buffered LO. The phase-shifter maintains an accurate 90° phase relationship between the I and the Q mixers' LO inputs to provide excellent image rejection over a wide frequency range. The I and Q input bandwidth of over 400MHz supports virtually all broadband digital transmission requirements. For ease of use, the two mixer outputs are summed into a single-ended, 50-Ohm terminated RF output.

The LTC5598 operates from a single 5V supply. It runs on a quiescent current of 168mA, consuming 20% less power than other comparable modulators. The LTC5598 provides a power-down feature with turn-on and turn-off time of 75ns and 10ns, respectively, supporting TDD (Time Division Duplex) type transmitters. When the chip is disabled with a logic LOW applied to its ENABLE input pin, the device draws a typical shutdown current of 43uA. The LTC5598 comes in a 24-lead, 4mm x 4mm QFN surface mount package.