Wideband active mixer exceeds +30dBm IIP3 with 0dB conversion gain

January 31, 2014 // By Graham Prophet
LTC5577 is a 300 MHz to 6 GHz active downconverting mixer with +30 dBm IIP3 (Input Third Order Intercept) and 0 dB conversion gain. It has wide operating frequency capability, covering all cellular bands from 450 MHz to 3.6 GHz with a single part.

The device’s IF output port, usable from 1 MHz to 1.5 GHz, delivers flat conversion gain performance to over 600 MHz bandwidth, for LTE and LTE-Advanced base stations, as well as other wideband receiver applications. Its exceptionally low M•RF x N•LO mixing spur products are suitable for low distortion receivers and improve the distortion correction performance of digital predistortion (DPD) receivers. Its very low LO to RF leakage enable receivers to satisfy spurious emissions requirements with little or no RF input filtering. The IC’s RF input is designed to withstand strong in-band blocking signals while delivering the lowest noise figure, ensuring receiver sensitivity in the presence of interference.

The LTC5577 has integrated wideband RF and LO input transformers, enabling the mixer to operate 50 Ohm single-ended from 700 MHz to 4.3 GHz continuously with the same external matching. As a result, minimum external components are needed. The LO input remains 50 Ohm terminated regardless of whether the device is powered on or off, and hence can be TDD (Time Division Duplex) enabled and disabled rapidly without causing disturbance that can unlock a PLL (phase-locked loop). The LO input is buffered, requiring only 0 dBm drive level and thus can be driven directly from a VCO circuit with minimum or no frequency pulling. All these features combine to yield a cost-effective solution that is space efficient and easy to design.

Aside from cellular base station applications, the LTC5577 is also suited for a range of radios requiring robust performance, such as cable TV transceivers, wideband military radios, broadband VHF/UHF white space broadcast radios, software-defined radios, RF test instrumentation, wireless repeaters and satellite communications.

It occupies a 4 x 4 mm QFN package, operates over -40°C to 105°C, and needs a single 3.3V supply at 180 mA: the LTC5577 consumes the lowest power in the +30dBm IIP3 mixer class. Disabled power drain is a maximum of 200µA leakage current. It costs $6.75