The MAX2700/MAX2701 are highly integrated direct downconversion (zero-IF) receivers designed for wideband wireless local loop (WLL) systems operating in the 1.8GHz to 2.5GHz band. The MAX2700/MAX2701s' zero-IF architecture eliminates the need for IF downconversion stages and the use of an IF SAW filter. This reduces the overall receiver cost by reducing the component count and required board space.
The MAX2700/MAX2701 have three main blocks: low-noise amplifier (LNA), quadrature downconverter, and baseband variable gain amplifiers (VGAs). The LNA is a single-ended amplifier with selectable gain and shutdown options. It provides a high input third-order intercept point (IP3), which reduces cross-modulation and gain compression due to high-level RF interference. The quadrature downconverter section consists of two highly linear double-balanced mixers driven by an external local oscillator (LO) with a selectable LO doubler. The double-balanced mixers are optimized to provide high input IP3 and minimum added noise. The mixers’ high input second-order intercept point (IIP2) helps minimize receiver desensitization due to high-level AM-modulated interferers.
The two baseband VGAs in each channel provide 80dB of total maximum gain and greater than 60dB of gain control. The first AGC amplifier is optimized for low noise, low power dissipation, and high linearity over the entire gain range to ensure high gain compression performance. An external lowpass filter between baseband VGAs provides the required channel selectivity at the adjacent channel. An integrated gain offset correction loop circuit provides <0.3dB amplitude mismatch between the I and Q channels.
The MAX2700/MAX2701 operate from a single +2.7V to +3.3V power supply, drawing only 165mA of supply current and 20µA in shutdown mode. Both devices are available in small 48-pin TQFP packages with exposed paddle (EP) for optimum high-frequency performance.