The LT®5502 is a 70MHz to 400MHz monolithic integrated quadrature IF demodulator. It consists of an IF limiter, quadrature down mixers, integrated lowpass filters, and divide-by-two LO buffers. The demodulator provides all building blocks for demodulation of I and Q baseband signals with a single supply voltage of 1.8V to 5.25V. The IF limiter has 84dB small-signal gain, and a built-in receive signal strength indicator (RSSI) with over 90dB linear range. The input referred noise-spectral-density is 1.45nV/√Hz, which is equivalent to a 4dB noise figure when the input is terminated with a 50? source. The integrated lowpass output filters act as antialiasing and pulse-shaping filters for demodulated I/Q-baseband signals. The 3dB cutoff frequency of the filters is about 7.7MHz. The VCO frequency is required to be twice the desired operating frequency to provide quadrature local oscillator (LO) signals to the mixers. The standby mode provides fast transient response to the receive mode with reduced supply current when the I/Q outputs are AC-coupled to a baseband chip.
