Linear Technology Corporation introduces an active double-balanced up-conversion mixer

     Linear Technology Corporation introduced the LTC5576, an active double-balanced up-conversion mixer with a wide RF frequency range from 3GHz to 8GHz. The LTC5576 improves microwave transmitter and upconversion performance with excellent 25dBm OIP3 linearity and an excellent conversion loss of only 2dB at 8GHz, providing superior output signal quality compared to other passive mixers, which typically have a loss of 8dB.

     In addition, the integrated buffer at the LO input only requires a 0dBm drive level, so an external amplifier circuit is virtually eliminated. The LTC5576 integrates a unique RF balanced-unbalanced transformer design to expand the output frequency bandwidth while enabling single-ended operation in the 3GHz to 8GHz range. The IF input also has a large bandwidth and is continuously 50Ω differential matched from 30 MHZ to more than 3GHz. With a suitable externally balanced and unbalanced transformer, this upper limit range can be extended beyond 6GHz.

     The LTC5576 features an active double-balanced mixer core with excellent port-to-port isolation. For example, at 5.8GHz frequency and 0dBm LO input, the RF output has an extremely low LO leakage of -35dBm. This low leakage level helps minimize the need for external filtering, making it easier to meet regulatory requirements for out-of-band radiation. Even at 8GHz, its LO leakage of -27dBm is excellent. The frequency expansion capability meets the requirements of a variety of applications, such as short-range microwave backhaul, 5.8GHz cellular base stations and wireless repeater stations. In addition, its dynamic range meets the performance requirements of wireless test equipment, radar receivers and satellite communications.

     The LTC5576 is more robust than other integrated microwave mixers and offers a higher ESD rating on all pins for a 2500V mannequins (HBM). The LTC5576 comes in a 16-lead, 4mm x 4mm QFN package that allows for designs that require minimal external components, resulting in a very compact solution. The device is specified to operate in a housing temperature range of -40 °C to 105°C, supporting an extended ambient operating temperature range.

     The mixer is optimized to operate with a single 5V supply with a nominal supply current of 99mA. By using a 3.3V power supply, its power consumption can be reduced, while performance is slightly reduced. In addition, the LTC5576 has an enable pin to disable the IC, which consumes a typical spare current of only 1.3mA when deactivated. This enable pin can be used to quickly turn on or off the device in less than 0.6µs, thus supporting time-division duplex (TDD) or burst-mode radio devices.