Linear Technology has released an RF mixer that has an IIP3 (input third order intercept) of 26.8dBm and a wide operating frequency coverage to address the footprints of multimode 4G RRH (remote radio head), MIMO (multiple-input, multiple-output) receivers. The mixer operates over a frequency from 300MHz to 4GHz and therefore a single part can be configured to operate on any of the cellular bands from 700MHz to 2.7GHz. It consumes less power and delivers good IIP3 with a conversion gain of 2dB and a noise figure of 11.7dB. The company claims that the mixer has robust inputs that can withstand in-band blocking interference signals without degrading its noise figure.
Each channel of the dual mixer contains an integrated balun transformer at the RF and LO inputs. The channel's LO has separate buffers driven from a common input and provide good channel-to-channel isolation while preserving phase coherency between the two channels. The LO input port is single-ended and 50Ω matched regardless of whether the mixer is turned on or powered down. The channels do not induce load disturbance and avoid unlocking of a phase-locked loop and VCO circuit. The LO input requires 0dBm drive level and has good reverse RF isolation.
The dual mixer's low power and compact solution are optimized for multiple receivers in 4G base stations. The device's 300mW/channel power consumption eases the thermal design challenge in MIMO RRH designs and packs as many as 8 or 16 channels of receivers in weather-sealed housings. The mixer operates from -40 to +105°C and offers good conversion gain variation to ensure consistent receiver performance over temperature. It operates from a single 3.3V supply and draws a total supply current of 180mA when both channels are on. Each mixer can be independently shut down with a separate enable control. When disabled, the IC has a maximum of 200μA leakage current.
