High Linearity Dual Downconverting Mixers Reduce Power Consumption & Size for 4G MIMO Receivers

The LTC559x dual mixers offer outstanding IIP3 (Input Third-Order Intercept) of more than 26dBm, low noise figures of less than 10dB and high conversion gain of 8.5dB, enabling excellent dynamic range performance for both MIMO (Multiple-Input, Multiple-Output) and diversity wideband receivers. The LTC559x family of dual mixers provides best-in-class capability to maintain a low noise figure in the presence of strong blocking interferers, significantly enhancing receiver sensitivity and robustness. Unlike other dual mixers in their class, the LTC559x family can operate on a single 3.3V supply without compromising performance, reducing power consumption by more than 24% compared to the closest competing solution.

The four dual mixers are optimized for performance within their frequency bands. All four parts are pin compatible to enable easy migration from one frequency band to another.

The LTC559x dual mixers are designed to address the challenging implementations of high performance, multichannel receivers of next-generation 4G and other broadband wireless networks. Their low power consumption eases the thermal challenge associated with implementation of RRH (Remote Radio Head), which can pack as many as 8 or 16 channels of receivers in weather-sealed housings. The dual mixers provide a highly compact solution footprint with their 5mm x 5mm QFN packages, requiring minimum external components. The LTC559x are specified for case operating temperature from -40°C to 105°C to meet the rugged environment to which such equipment is exposed. To further enhance performance under these conditions, the dual mixers offer best-in-class conversion gain variation to ensure consistent receiver performance over temperature.

Each channel of the LTC559x dual mixer contains an integrated IF amplifier, LO buffer and RF balun transformers on chip. Each mixer’s RF input is single-ended, 50Ohm matched. A common LO input drives the two internally split LO buffers, affording excellent channel-to-channel isolation while preserving phase coherency between channels. The LO input is also single-ended, always 50Ohm matched regardless of whether the mixer is active or powered down to avoid disturbing or unlocking the PLL (phase-locked loop) driven VCO circuit. The LO input requires only 0dBm drive level. All of these features ensure a compact solution with minimal external components and enhanced ease of use.

The LTC559x dual mixers have identical pinouts, allowing designers to share PC board layouts across multiple platforms operating in different frequency bands. This helps users reduce total ownership costs and speed time to market.

The LTC559x dual mixers are powered by a single 3.3V supply, drawing a total supply current of 380mA with both channels on. Each mixer can be independently shut down with a separate enable control. When disabled, the IC consumes a maximum of 500μA standby current. In addition, a digital bias control pin allows systems to further reduce the power to about 800mW, enabling more efficient management of energy consumption during non-peak hours. In low power mode, the IIP3 reduces from 26.2dBm to a usable 21.4dBm (at 1.95GHz).