Linear introduces LTC5569 RF mixer for multi-mode receivers in 4G base stations

Linear Technology Corporation introduces the LTC5569, a dual-channel high-performance RF mixer that combines 26.8dBm IIP3 (input 3rd order intercept), 300mW power per mixer and wide operating frequency coverage to meet the high-density board requirements of multi-mode 4G RRH (remote radio head) MIMO (multiple input, multiple output) receivers. The mixer operates over a wide frequency range of 300MHz to 4GHz, so a single device can be configured to operate on any cellular band from 700MHz to 2.7GHz. The LTC5569 dual-channel mixer offers best-in-class power consumption while providing excellent IIP3, 2dB conversion gain and 11.7dB noise figure. This achieves excellent dynamic range performance for MIMO and a wide range of wideband receiver applications. In addition, the LTC5569 has a rugged input that can withstand strong in-band blocking interferers without significantly degrading the noise figure, thereby improving receiver sensitivity.

Each channel of the LTC5569 dual mixer contains an integrated balun at the RF and LO inputs. These ports are single-ended 50Ω matched, requiring minimal external components, saving cost and reducing the solution footprint. Each channel's LO has a separate buffer driven from a common input, providing excellent channel-to-channel isolation while maintaining phase coherence between the two channels. The LO input port is also single-ended and always 50Ω matched, regardless of whether the mixer is powered on or off. Therefore, switching channels on and off does not cause load disturbances, thereby avoiding unlocking the PLL (phase-locked loop) and VCO circuits. The LO input requires only a 0dBm drive level and has excellent reverse RF isolation, so it can be driven directly with an external VCO circuit without an external buffer. All of these features ensure a compact solution with minimal external components and enhanced ease of use.

Photo Caption: High-Performance, Low-Power, Wideband Dual-Channel RF Mixer

The LTC5569 dual-channel mixer's low power and compact solution is optimized for multimode receivers in the next generation of 4G base stations. The device's 300mW per channel power consumption eases the thermal challenges of MIMO RRH designs, allowing up to 8 or 16 receiver channels to be packed into a small, weather-proof sealed enclosure. The dual-channel mixer requires minimal external components, providing a highly compact solution with its 4mm x 4mm QFN package. In addition, the LTC5569 is specified to operate over a temperature range of -40°C to 105°C to ensure reliability in harsh environments. To further improve performance under these conditions, the dual-channel mixer provides excellent conversion gain variation to ensure consistent receiver performance over temperature.

The LTC5569 operates from a single 3.3V supply and draws 180mA of total supply current when both channels are on. Each mixer can be independently shut down with a separate enable control. The maximum leakage current when the IC is disabled is 200uA. The LTC5569 is priced at $8.50 each in 1,000-piece quantities. Samples and production quantities are available now.