Dual broadband RF mixer finds use in 4G basestation receivers

Linear Technology has introduced the dual, high-performance LTC5569 RF mixer, which operates at 300 MHz to 4 GHz frequencies. The highly linear part has an input IP3 (third-order intercept) of 26.8 dBm, an output IP3 of 28.8 dBm, and a conversion gain of 2 dB. The IC has a noise figure of 11.7 dB, or 17dB with a 5-dBm inband blocking-interference signal. The LTC5569 operates from a single 3.3V supply, and power consumption is 600 mW when you enable both mixers. When you disable the mixers, the IC has a maximum 200-µA leakage current. You can independently shut down either channel using a separate enable control. Turning on and off the channels does not induce a load disturbance, which might unlock the PLL (phase-locked-loop) and VCO (voltage-controlled-oscillator) circuits.

Each channel of the LTC5569 dual mixer contains an on-die integrated balun (balanced-unbalanced) transformer at the RF and local-oscillator inputs. These single-ended ports are matched at 50Ω. Each channel's local oscillator has separate buffers you drive from a common input, providing channel-to-channel isolation and preserving phase coherency between the two channels. The local oscillator's input port is always matched at 50Ω, regardless of whether the mixer is on or off. The local oscillator's input requires a 0-dBm drive level, and it has excellent reverse-RF isolation. You can drive it directly from an external VCO circuit.

The IC targets use in the new generation of multiple receivers in 4G (fourth-generation) base stations. It eases the thermal design challenge in MIMO (multiple-input/multiple-output) remote-radio-head designs, which pack as many as 16 channels of receivers into small weather-sealed housings. You can configure the part to operate on 700-MHz to 2.7-GHz cellular bands.

Linear Technology specifies the LTC5569 for a case operating temperature of −40 to +105°C and offers it in a 4×4-mm QFN package. It costs $8.50 each (1000). Samples and production quantities are available.

Linear Technology
Dual broadband RF mixer finds use in 4G basestation receivers