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The LTC5598 direct-conversion quadrature modulator from Linear Technology Corp. offers superior linearity performance and low noise to enhance the dynamic range performance of basestation transmitters, according to the company, with +27.7-dBm output third-order intercept (OIP3) and +74-dBm output second-order intercept (OIP2).
Also, it offers a –160-dBm/Hz noise floor at a +5-dBm output level. It provides –50.4-dBc image rejection and a carrier leakage of –55 dBm.

The LTC5598’s dynamic range performance, from low frequency to above 1 GHz, suits point-to-point broadband microwave links, 450- and 700-MHz Long-Term Evolution (LTE) basestation transmitters, 800-MHz GSM and 900-MHz EDGE basestation transmitters, 880-MHz cdma2000 basestations, video and cable broadband modulators, multiband military radios, 900-MHz multiprotocol RFID readers, and satellite transmitters. It can operate down to 5 MHz, enabling low-frequency applications like 13.56-MHz RFID and contactless readers, telemetry, military communications, and medical instrumentation.

The device 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°C phase relationship between the I and Q mixers’ LO inputs to provide excellent image rejection over a wide frequency range. The I and Q bandwidth of more than 400 MHz supports virtually all broadband signal requirements. For ease of use, the two mixer outputs are summed into a single-ended, 50-Ω terminated RF output.

The LTC5598 operates from a single 5-V supply. It runs on a 168-mA quiescent current, consuming 20% less power than comparable modulators, according to Linear. Also, it provides a power-down feature with turn-on and turn-off time of 75 ns and 10 ns, respectively, supporting TDD-type (time-division duplex) transmitters. When the chip is disabled with a logic LOW applied to its ENABLE input pin, it draws a typical shutdown current of 43 µA. The LTC5598 comes in a 24-lead, 4- by 4-mm quad flat no-lead (QFN) surface-mount (SMT) package. Available immediately from stock, pricing starts at $5.19 each in 1000-piece quantities.