50 MHz to 1000 MHz Quadrature Demodulator AD8348 FEATURES FUNCTIONAL BLOCK DIAGRAM VREF IMXO IOFS IAIN IOPP IOPN Integrated I/Q demodulator with IF VGA amplifier 14 8 13 6 4 3 Operating IF frequency 50 MHz to 1000 MHz BIAS VREF ENBL 15 CELL (3 dB IF BW of 500 MHz driven from R = 200 ) S 5 VCMO Demodulation bandwidth 75 MHz VCMO DIVIDE 1 LOIP Linear-in-decibel AGC range 44 dB BY 2 IFIP 11 PHASE Third-order intercept IFIN 10 SPLITTER 28 LOIN IIP3 +28 dBm minimum gain (FIF = 380 MHz) AD8348 IIP3 8 dBm maximum gain (FIF = 380 MHz) GAIN VGIN 17 CONTROL Quadrature demodulation accuracy VCMO Phase accuracy 0.5 18 19 24 21 16 23 25 26 MXIP MXIN ENVG QXMO QOFS QAIN QOPP QOPN Amplitude balance 0.25 dB Figure 1. Noise figure 11 dB maximum gain (F = 380 MHz) IF LO input 10 dBm Single supply 2.7 V to 5.5 V Power-down mode Compact, 28-lead TSSOP package APPLICATIONS QAM/QPSK demodulator W-CDMA/CDMA/GSM/NADC Wireless local loop LMDS GENERAL DESCRIPTION The AD8348 is a broadband quadrature demodulator with an Separate I- and Q-channel baseband amplifiers follow the baseband integrated intermediate frequency (IF), variable gain amplifier outputs of the mixers. The voltage applied to the VCMO pin sets (VGA), and integrated baseband amplifiers. It is suitable for use in the dc common-mode voltage level at the baseband outputs. communications receivers, performing quadrature demodulation Typically, VCMO is connected to the internal VREF voltage, but from IF directly to baseband frequencies. The baseband amplifiers it can also be connected to an external voltage. This flexibility are designed to interface directly with dual-channel ADCs, such allows the user to maximize the input dynamic range to the ADC. as the AD9201, AD9283, and AD9218, for digitizing and post- Connecting a bypass capacitor at each offset compensation input processing. (IOFS and QOFS) nulls dc offsets produced in the mixer. Offset compensation can be overridden by applying an external voltage The IF input signal is fed into two Gilbert cell mixers through at the offset compensation inputs. an X-AMP VGA. The IF VGA provides 44 dB of gain control. A precision gain control circuit sets a linear-in-decibel gain char- The mixers outputs are brought off-chip for optional filtering acteristic for the VGA and provides temperature compensation. before final amplification. Inserting a channel selection filter The LO quadrature phase splitter employs a divide-by-2 frequency before each baseband amplifier increases the baseband amplifiers divider to achieve high quadrature accuracy and amplitude balance signal handling range by reducing the amplitude of high level, over the entire operating frequency range. out-of-channel interferers before the baseband signal is fed into the I/Q baseband amplifiers. The single-ended mixer output is Optionally, the IF VGA can be disabled and bypassed. In this amplified and converted to a differential signal for driving ADCs. mode, the IF signal is applied directly to the quadrature mixer inputs via the MXIP and MXIN pins. Rev. A Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. rights of third parties that may result from its use. Specifications subject to change without notice. No Tel: 781.329.4700 www.analog.com license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Fax: 781.461.3113 2006 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. 03678-001AD8348 TABLE OF CONTENTS Features .............................................................................................. 1 Enable........................................................................................... 18 Applications....................................................................................... 1 Baseband Offset Cancellation................................................... 18 Functional Block Diagram .............................................................. 1 Applications..................................................................................... 20 General Description ......................................................................... 1 Basic Connections...................................................................... 20 Revision History ............................................................................... 2 Power Supply............................................................................... 20 Specifications..................................................................................... 3 Device Enable ............................................................................. 20 Absolute Maximum Ratings............................................................ 6 VGA Enable ................................................................................ 20 ESD Caution.................................................................................. 6 Gain Control ............................................................................... 20 Pin Configuration and Function Descriptions............................. 7 LO Inputs..................................................................................... 20 Equivalent Circuits ........................................................................... 9 IF Inputs ...................................................................................... 20 Typical Performance Characteristics ........................................... 11 MX Inputs ................................................................................... 20 VGA and Demodulator ............................................................. 11 Baseband Outputs ...................................................................... 21 Demodulator Using MXIP and MXIN.................................... 14 Output DC Bias Level................................................................ 21 Final Baseband Amplifiers ........................................................ 15 Interfacing to Detector for AGC Operation............................... 21 VGA/Demodulator and Baseband Amplifier......................... 16 Baseband Filters.......................................................................... 22 Theory of Operation ...................................................................... 18 LO Generation............................................................................ 23 VGA.............................................................................................. 18 Evaluation Board........................................................................ 23 Downconversion Mixers ........................................................... 18 Outline Dimensions ....................................................................... 28 Phase Splitter............................................................................... 18 Ordering Guide .......................................................................... 28 I/Q Baseband Amplifiers........................................................... 18 REVISION HISTORY 4/06Rev. 0 to Rev. A Updated Format..................................................................Universal Changes to Specifications................................................................ 3 Changes to IF Inputs Section ........................................................ 20 Changes to Evaluation Board Section.......................................... 23 Changes to Table 6.......................................................................... 27 Changes to Ordering Guide .......................................................... 28 8/03Revision 0: Initial Version Rev. A Page 2 of 28