ANALOG DEVICES DC1048A Evaluation Board, LT5575EUF, Quadrature Demodulator, RF / IF

DC1048A demonstration circuit is a 1.5GHz to 2.7GHz direct conversion I/Q receiver featuring the LT5575. The LT® 5575 is an 800MHz to 2.7GHz direct conversion quadrature demodulator optimized for high linearity receiver applications. It is suitable for communications receivers where an RF signal is directly converted into I and Q baseband signals with bandwidth up to 490MHz. The LT5575 incorporates balanced I and Q mixers, LO buffer amplifiers and a precision, high frequency quadrature phase shifter. The integrated on-chip broadband transformers provide 50 ohm single-ended interfaces at the RF and LO inputs. Only a few external capacitors are needed for its application in an RF receiver system. Demonstration circuit 1048A is designed for evaluating the LT5575 in the frequency range between 1.5GHz and 2.7GHz. It can be optimized for input frequencies below 1.5GHz by insta ling external shunt capacitors at RF input and LO input ports.

• 4.5V to 5.25V supply voltage, 132mA supply current
• 100µA maximum shutdown current at EN = Low
• 57.1dB RF to LO isolation, -64.6dBm LO to RF leakage
• 0.4° I/Q phase mismatch, 0.01dB I/Q gain mismatch
• 11.2dBm input 1dB compression, 12.7dB noise figure (double-side band)
• 4.2dB conversion gain (voltage gain, RLOAD = 1Kohm), -13dBm to 5dBm LO input power
• > 10dB RF/LO input return loss (Z0 = 50 ohm, 1.5GHz to 2.7GHz, internally matched)
• 65ohm/5pF baseband I/Q output impedance (single-ended)
• DC to 490MHz baseband frequency range
• < 9mV output DC offset voltage