Broadband High Dynamic Range Active Mixer
Linear Technology has developed an ultra-high dynamic range RF down-converting mixer for applications that demand the very best in performance. The LTC5551 offers very high linearity of +36 dBm IIP3 and low 9.7 dB noise figure comparable to the highest IIP3 passive mixers available. Unlike passive mixers which typically have 7 to 9 dB of conversion loss, the LTC5551 actually has 2.4 dB of conversion gain, substantially improving receiver dynamic range. The device also has broad RF frequency range capability, operating from 300 MHz to 3.5 GHz.
Additionally, passive mixers require high LO drive to reach their claimed IIP3. The LTC5551 has an integrated LO buffer requiring only 0 dBm drive level, hence external circuitry and costs are minimized. And with the elimination of a high power LO signal in the users’ receiver, it substantially reduces a potential source of undesirable radiation, thus simplifying filtering and RF shielding requirements.
The LTC5551 ensures robust radio performance with its high 1 dB compression point of +18 dBm. Both the RF and LO inputs have integrated balun transformers, further reducing cost and external components while simplifying the design task. The mixer is powered from a single 3.3 V supply with current consumption of 204 mA, delivering its high performance with exceptionally low power. If needed, the mixer also has a low power mode controlled via the ISEL pin. In this mode, current consumption drops by 30 percent to 142 mA, trading off the IIP3 to +29.3 dBm. The mixer’s minimum external circuits and its 16-lead, 4 × 4 mm QFN package provide a highly compact solution footprint.
The superior performance of this mixer is ideally suited for a wide range of mission-critical, high performance applications that are exposed to strong interference sources such as multi-carrier GSM, 4G LTE and LTE-Advanced multimode base stations, point-to-point backhauls, military communications, wireless repeaters, public safety radios, VHF/UHF/white-space broadcast receivers, radar and avionics.