Wideband 3 GHz to 8 GHz mixer improves upconversion specifications

May 27, 2015 // By Graham Prophet
LTC5576 is an active double balanced upconversion mixer with very wide RF frequency range, extending from 3GHz to 8GHz: for microwave transmitter and upconversion functions it offers linearity of 25 dBm OIP3 and conversion loss of only 2 dB at 8 GHz, providing superior output signal quality compared to alternative passive mixers, which typically have 8 dB of loss.

The local oscillator (LO) input’s integrated buffer needs only a 0 dBm level drive, effectively eliminating an external amplifier circuit. The LTC5576 employs a unique integrated RF balun transformer design to extend output frequency bandwidth while enabling single-ended operation from 3 GHz to 8 GHz. Its IF input also has wide bandwidth, and is continuous 50Ω differential matched from 30 MHz to over 3 GHz. With a proper external balun transformer, the upper range can be extended to over 6 GHz.

The LTC5576 employs an active double balanced mixer core with excellent port-to-port isolation. For example, at 5.8 GHz frequency and 0 dBm LO input, the LO leakage at its RF output measures an exceptionally low -35 dBm. This low leakage level helps minimise external filtering in order to meet regulatory out-of-band emission requirements. Even at 8 GHz, its LO leakage is -27 dBm.

The LTC5576’s extended frequency capability addresses a wide range of applications such as short-range microwave backhauls, 5.8 GHz cellular base stations and wireless repeaters. Its dynamic range supports the performance requirements of wireless test equipment, radar receivers and satellite communications.

The LTC5576 is more rugged than other integrated microwave mixers with its improved ESD rating of 2,500V human body model (HBM) on all pins. Housed in a 16-lead, 4 x 4mm QFN package and with its minimal external component design, the LTC5576 produces a compact solution footprint. The device is rated for operation from -40°C to 105°C case temperature to support extended environmental operating temperature. The mixer is optimised for single 5V supply operation, with a nominal supply current of 99 mA. Its power consumption can be reduced by powering from a 3.3V supply, with slightly reduced performance. Additionally, the LTC5576 has an enable pin to disable the IC, which when deactivated, draws only 1.3 mA typical standby current. This enable pin can be used to turn the device on and off rapidly in less than