50-Ohm matched input maintained over 30 MHz to 6 GHz in high linearity mixer

July 26, 2013 // By Paul Buckley
Linear Technology has released a high performance mixer with a wide frequency range, extending to 6 GHz.

LTC5510 provides a continuous 50-Ohm matched input from 30 MHz to 6 GHz, while delivering outstanding linearity and gain flatness. The features enable applications to work over a wider frequency span without needing to rematch the input for different frequency bands, thereby reducing cost and simplifying design. Additionally, the LTC5510’s output can reach up to 4.5 GHz, allowing the device to be used either as an upconversion or downconversion mixer, making it highly versatile. The mixer has excellent linearity performance of 27.8 dBm OIP3 as an upconverting mixer, and 24.9 dBm IIP3 as a downconverting mixer at 2 GHz. Its conversion gain of 1.1 dB and noise figure of 11.6 dB produce outstanding dynamic range performance for robust radios.

The LTC5510 employs an active mixer core with an on-chip LO buffer. Its LO input requires only 0 dBm drive levels. Additionally, the device has excellent input and output isolation. For example, in downconverting mixer applications, the LO signal leakage to the RF input is -70 dBm. This low level leakage minimises or eliminates external filters. Similarly for upconverting mixer applications, the device’s LO leakage to the RF output is -35 dBm, 10 dB to 30 dB better than other mixers, particularly when compared to passive mixers, which have very high LO leakage. As a result, expensive SAW filter requirements can often be relaxed, which otherwise would be necessary to control the undesirable LO leakage to the antenna—a primary cause of excessive out-of-band emissions. Related cost savings can be significant.

The LTC5510’s extended frequency capability simplifies a wide variety of applications such as cellular basestations, wireless repeaters, microwave backhauls that can cross over multiple frequency bands. Other applications include VHF/UHF band radios, broadcast and white-space radios, military communications, cable systems, RF and wireless test equipment, public safety radios, radar receivers, satellite communications and wireless professional microphone receivers.

The LTC5510’s minimum external components and its 16-lead, 4 mm x 4 mm QFN