Wideband IQ Demodulator with IIP2 and DC Offset Control

The LTC5585 is a direct conversion quadrature demodulator optimized for high linearity receiver applications in the 400MHz to 4GHz frequency range. It is suitable for communications receivers where an RF signal is directly converted into I and Q baseband signals with bandwidth of 530MHz or higher. The LTC5585 incorporates balanced I and Q mixers, LO buffer amplifiers and a precision, high frequency quadrature phase shifter. The integrated on-chip broadband transformer provides a single-ended interface at the RF input with simple off-chip L-C matching. In addition, the LTC5585 provides four analog control voltage interface pins for IIP2 and DC offset correction, greatly simplifying system calibration.

The high linearity of the LTC5585 provides excellent spurfree dynamic range for the receiver. This direct conversion demodulator can eliminate the need for intermediate frequency (IF) signal processing, as well as the corresponding requirements for image filtering and IF filtering. These I/Q outputs can interface directly to channel-select filters (LPFs) or to baseband amplifiers.

Applications

* LTE/W-CDMA/TD-SCDMA Base Station Receivers

* Wideband DPD Receivers

* Point-To-Point Broadband Radios

* High Linearity Direct Conversion I/Q Receivers

* Image Rejection Receivers

* 400MHz to 4GHz Operating Frequency

* High IIP3: 28.7dBm at 700MHz, 25.7dBm at 1.95GHz

* High IIP2: 70dBm at 700MHz, 60dBm at 1.95GHz

* User Adjustable IIP2 Up to 80dBm

* User Adjustable DC Offset Null

* High Input P1dB: 16dBm at 1950MHz

* I/Q Bandwidth of 530MHz or Higher

* Image Rejection: 43dB at 1950MHz

* Noise Figure:

* 13.5dB at 700MHz

* 12.7dB at 1.95GHz

* Conversion Gain:

* 2.0dB at 700MHz

* 2.4dB at 1.95GHz

* Single-Ended RF with On-Chip Transformer

* Shutdown Mode

* Operating Temperature Range (TC): –40°C to 105°C

* 24-Lead 4mm × 4mm QFN Package