Linear Technology Corp.’s lasted wide bandwidth active upconverting mixer, the LT5578, delivers high dynamic range performance from 400MHz to 2.7GHz, supporting all of the allocated LTE (Long-Term Evolution) broadband wireless services. At 900MHz, the mixer offers 27dBm Output IP3 linearity and noise floor of -160.5dBm/Hz at an output level of -5dBm, enabling outstanding transmitter dynamic range. In addition, the mixer has 1.4dB conversion gain with integrated RF balun transformers that provide a single-ended RF output and LO input to simplify designs while reducing external component count. Moreover, the device’s LO input is internally buffered, requiring a drive level of only -1dBm. This results in an outstanding LO-to-RF leakage of -43dBm.
The LT5578 is designed to satisfy the requirements of next generation LTE wireless basestation transmitters and improves the performance of wireless equipment including W-CDMA, UMTS, TD-SCDMA, CDMA2000, CDMA, and GSM/EDGE basestations. The mixer is also ideal for a wide range of communications gear such as cable headend transmitters, microwave broadband transmitters, wireless repeaters, military radios, digital video broadcast systems, 2.4GHz ISM band transmitters, test instrumentation, micro-cell and pico-cell basestation applications.
The LT5578’s active, double-balanced design provides several unique benefits. Compared to alternative passive mixers’ more than 8dB of conversion loss, the LT5578’s 1.4dB conversion gain produces 9dB higher signal power without the need of an external high power, high linearity RF output amplifier stage. The LT5578 not only saves cost but also reduces power consumption. Additionally the device can deliver an output level of -5dBm with an outstanding output noise floor of -160.5dBm/Hz. This feature enables users to deliver maximum transmitter signal power while preserving dynamic range performance. Hence optimum ACPR (Adjacent Channel Power Ratio) performance can be attained. Moreover, most passive mixers have poor port-to-port isolation, resulting in undesirable leakage of the LO signal to the RF output, which necessitates a high rejection RF filter for suppression. The LT5578’s balanced design inherently suppresses the LO-to-RF leakage to -43dBm typical, thus relaxing and reducing external filtering requirements. The combination of these attributes makes possible a cost-effective, compact and high performance solution.
The LT5578 operates from a single 3.3V supply. Typical quiescent supply current is 152mA. So the LT5578 delivers outstanding performance powered with only modest 500mW consumption. The device comes in a 24-lead 5x5mm plastic QFN surface mount package.
